Autonomic Dysfunction in Multiple Sclerosis and Optic Neuritis

D 1061 OULU 2010 D 1061

UNIVERSITY OF OULU P.O.B. 7500 FI-90014 UNIVERSITY OF OULU FINLAND ACTA UNIVERSITATIS OULUENSIS ACTA UNIVERSITATIS OULUENSIS ACTA

SERIES EDITORS DMEDICA Anne Saari

ASCIENTIAE RERUM NATURALIUM AnneSaari Professor Mikko Siponen AUTONOMIC DYSFUNCTION BHUMANIORA IN MULTIPLE SCLEROSIS AND University Lecturer Elise Kärkkäinen CTECHNICA OPTIC NEURITIS Professor Pentti Karjalainen DMEDICA Professor Helvi Kyngäs ESCIENTIAE RERUM SOCIALIUM Senior Researcher Eila Estola FSCRIPTA ACADEMICA Information officer Tiina Pistokoski GOECONOMICA University Lecturer Seppo Eriksson

EDITOR IN CHIEF University Lecturer Seppo Eriksson PUBLICATIONS EDITOR

Publications Editor Kirsti Nurkkala FACULTY OF MEDICINE, INSTITUTE OF CLINICAL MEDICINE, DEPARTMENT OF NEUROLOGY, ISBN 978-951-42-6238-8 (Paperback) UNIVERSITY OF OULU; ISBN 978-951-42-6239-5 (PDF) DEPARTMENT OF MEDICAL REHABILITATION, ISSN 0355-3221 (Print) OULU UNIVERSITY HOSPITAL ISSN 1796-2234 (Online)

ACTA UNIVERSITATIS OULUENSIS D Medica 1061

ANNE SAARI

AUTONOMIC DYSFUNCTION IN MULTIPLE SCLEROSIS AND OPTIC NEURITIS

Academic dissertation to be presented with the assent of the Faculty of Medicine of the University of Oulu for public defence in Auditorium 8 of Oulu University Hospital, on 20 August 2010, at 12 noon

Supervised by Professor Vilho Myllylä Professor Uolevi Tolonen Docent Kyösti Sotaniemi

Reviewed by Docent Esko Kinnunen Docent Juhani Ruutiainen

ISBN 978-951-42-6238-8 (Paperback) ISBN 978-951-42-6239-5 (PDF) http://herkules.oulu.fi/isbn9789514262395/ ISSN 0355-3221 (Printed) ISSN 1796-2234 (Online) http://herkules.oulu.fi/issn03553221/

Cover design Raimo Ahonen

JUVENES PRINT TAMPERE 2010 Saari, Anne, Autonomic dysfunction in multiple sclerosis and optic neuritis. Faculty of Medicine, Institute of Clinical Medicine, Department of Neurology, University of Oulu, P.O.Box 5000, FI-90014 University of Oulu, Finland; Department of Medical Rehabilitation, Oulu University Hospital, P.O. Box 25, FI-90029 OYS, Finland Acta Univ. Oul. D 1061, 2010 Oulu, Finland

Abstract Multiple sclerosis (MS) is one of the major causes of disability in the young, mostly affecting people between 20–45 years of age. MS is considered as an autoimmune disorder, characterized by discrete areas of central nervous system inflammation, demyelination and axonal injury. Symptoms related to alterations of the autonomic nervous system are frequent in patients with MS. Bladder dysfunction or impairment of sexual performance is highly distressing for most MS patients, whereas the clinical relevance of other autonomic symptoms is less clear. The present study was designed to clarify the involvement of cardiovascular and sudomotor dysfunctions in patients with MS, to study the sudomotor functions in patients with optic neuritis (optic neuritis being a frequent initial manifestation of MS), and to assess the extent of demyelinative lesions in the CNS by using magnetic resonance imaging and by correlating the findings thus obtained with autonomic nervous system responses. The study showed cardiovascular autonomic regulation failure in MS patients manifesting itself both in the heart rate responses to deep breathing and in the heart rate and blood pressure responses in the tilt table test. In particular, midbrain lesions were found to be associated with cardiovascular dysfunction. MS patients also showed abnormal sympathetic skin responses indicating sudomotor failure. Focal MS lesions in the temporal lobe, in the pons and in the cerebellum were also associated with abnormal sympathetic skin responses. MS patients were also found to have an impairment in thermoregulatory sweating, which seemed to be related to disease severity and to total lesion volume in the brain. Sympathetic skin responses were also abnormal in optic neuritis patients, suggesting sudomotor autonomic failure. Patients with optic neuritis showed no thermoregulatory dysfunction.

Keywords: autonomic nervous system, blood pressure, heart rate, multiple sclerosis, optic neuritis, sweating

Acknowledgements

I am deeply grateful to all the people who have contributed to this work. In particular I wish to express my deepest gratitude to Professor Vilho Myllylä for his excellent guidance during my study. I am also deeply grateful both to Docent Kyösti Sotaniemi for his tireless support and excellent advice on the accomplishment of this scientific work and to Professor Uolevi Tolonen for his invaluable practical advice, continuous support and encouragement during this study. I am also grateful to Professor Matti Hillbom for providing the research facilities needed for the project. I also want to thank Professor Kari Majamaa for support during this study. I also express my gratitude to Professor Juhani Pyhtinen, Docent Eija Pääkkö and Docent Jukka Jauhiainen for assessing the MRI examinations. I would also like to thank Kalervo Suominen, MSc, for his invaluable help in both the neurophysiological assessments and the statistical analyses in this study. My special thanks go to the whole staff in the Department of Neurology for their excellent co-operation during this study. I also want to express my gratitude to the personnel of the Department of Clinical Neurophysiology for their ever competent technical assistance. I also thank Professor Markku Alen and the late Professor Tapani Kallanranta for their support and advice during this work. I further owe my sincere gratitude to Docent Esko Kinnunen and Docent Juhani Ruutiainen for their constructive criticism and advice during the preparation of the manuscript. I also wish to express my warm thanks to Ian Morris-Wilson, PhD, for his expert revising of the English language of the manuscripts. My cordial thanks to all the MS patients and the controls belonging to the study groups. Finally, I want to express my warmest thanks to my family, for their love and support.

Oulu, May 2010 Anne Saari

6 Abbreviations

ANS autonomic nervous system aSSRs auditory SSRs BP blood pressure CNS central nervous system ECG electrocardiogram EDSS Expanded Disability Status Scale EMG electromyography eSSRs electrical SSRs HR heart rate MRI magnetic resonance imaging MS multiple sclerosis NTS nucleus tractus solitarius ON optic neuritis R–R R-to-R SD standard deviation SSR sympathetic skin response

Ttymp tympanic temperature TEWL transepidermal water loss

8 List of original articles

This thesis is based on the following articles, which are referred to in the text by their Roman numerals:

I Saari A, Tolonen U, Pääkko E, Suominen K, Pyhtinen J, Sotaniemi K & Myllylä V (2004) Cardiovascular autonomic dysfunction correlates with brain MRI lesion load in MS. Clin Neurophysiol 115: 1473–1478. II Saari A, Tolonen U, Pääkkö E, Suominen K, Pyhtinen J, Sotaniemi KA, Jauhiainen J & Myllylä VV (2008) Sympathetic skin responses in multiple sclerosis. Acta Neurol Scand 118: 226–231. III Saari A, Tolonen U, Pääkkö E, Suominen K, Jauhiainen J, Sotaniemi KA & Myllylä VV (2009) Sweating impairment in patients with multiple sclerosis. Acta Neurol Scand 120: 358–363. IV Saari A, Tolonen U, Pääkkö E, Suominen K, Jauhiainen J, Sotaniemi KA & Myllylä VV (2010). Sudomotor dysfunction in patients with optic neuritis. Clin Auton Res 20: 199–204.

10 Contents

Abstract Acknowledgements 5 Abbreviations 7 List of original articles 9 Contents 11 1 Introduction 13 2 Review of the literature 15 2.1 The autonomic nervous system ...... 15 2.1.1 Anatomy and physiology ...... 15 2.1.2 Cardiovascular autonomic control ...... 17 2.1.3 Sudomotor regulation ...... 18 2.2 Multiple sclerosis ...... 20 2.3 Optic neuritis ...... 22 2.4 Magnetic resonance imaging ...... 23 2.5 Autonomic dysfunction in MS ...... 25 2.5.1 General aspects ...... 25 2.5.2 Cardiovascular dysfunction ...... 26 2.5.3 Sudomotor dysfunction ...... 26 2.6 Autonomic dysfunction in optic neuritis ...... 27 2.7 Evaluation of autonomic functions ...... 27 2.7.1 General aspects ...... 27 2.7.2 Cardiovascular autonomic reflexes ...... 28 2.7.3 Sudomotor functions ...... 29 3 Aims of the study 31 4 Subjects and methods 33 4.1 Subjects ...... 33 4.2 Cardiovascular autonomic reflexes ...... 35 4.3 Sympathetic skin responses...... 37 4.4 Evaporimetry measurements ...... 37 4.5 Magnetic resonance imaging ...... 38 4.6 Statistical analyses ...... 39 5 Results 41 5.1 Cardiovascular autonomic reflexes in MS patients ...... 41 5.2 Sympathetic skin responses in MS patients ...... 42 5.3 Thermoregulatory sweating in MS patients ...... 44

11 5.4 Sudomotor responses in optic neuritis ...... 48 5.5 Magnetic resonance imaging ...... 51 5.5.1 MRI and cardiovascular autonomic reflexes in MS patients...... 51 5.5.2 MRI and sympathetic skin responses in MS patients ...... 52 5.5.3 MRI and thermoregulatory sweating in MS patients ...... 53 5.5.4 MRI and sudomotor responses in optic neuritis ...... 54 6 Discussion 55 6.1 General aspects...... 55 6.2 Cardiovascular autonomic dysfunction in MS patients ...... 55 6.3 Impaired sympathetic skin responses in MS patients ...... 57 6.4 Thermoregulatory sweating dysfunction in MS patients ...... 59 6.5 Sudomotor dysfunction in optic neuritis ...... 61 7 Conclusions 63 References 65 Original publications 77

12 1 Introduction

The autonomic nervous system (ANS) innervates every organ in the body. The term dysautonomia refers to a change in ANS function that adversely affects health (Goldstein et al. 2002). Autonomic dysfunction is frequent in many neurological diseases (Goldstein & Sharabi 2009) and may be caused by lesions in single or multiple areas of the central or peripheral nervous system. The symptoms of ANS dysfunction may cause great discomfort to the patient, e.g. patients with autonomic failure can experience disabling incontinence, postural dizziness, syncope, falls and constipation. Multiple sclerosis (MS) is one of the major causes of disability in the young (Ragonese et al. 2008). MS is viewed as an autoimmune disorder, characterized by discrete areas of central nervous system (CNS) inflammation, demyelination and axonal injury (Simon 2006). Symptoms related to alterations of the ANS are frequent in patients with MS. Bladder dysfunction or impairment of sexual performance is highly distressing for most MS patients, though the clinical relevance of other autonomic symptoms is less clear (Merkelbach et al. 2006). Optic neuritis (ON) is a frequent initial manifestation of MS (Beck et al. 2003). Autonomic failure affecting the pupillary function (Moro et al. 2007) is known to exist in ON patients, but there are no reports of wider ANS disturbances. The quantitative assessment of the sympathetic and parasympathetic functions is essential for confirming the diagnosis of autonomic failure (Hilz & Dutsch 2006). The techniques most widely used for this in the clinical setting entail the measurement of an end-organ response to a physiological provocation. Current approaches to the clinical assessment of the ANS generally involve laboratory procedures which have been designed to test one or more autonomic subsystems objectively and quantitatively. Thus, characterizing the autonomic functions will lead to a better understanding of the various forms of autonomic dysfunction in MS and to more effective treatments of their clinical manifestations. The present study was designed to clarify the role of the cardiovascular and sudomotor autonomic functions in patients with MS, to evaluate the sudomotor functions in patients with ON, to assess the extent of demyelinative lesions in the CNS and to correlate magnetic resonance imaging (MRI) findings with ANS responses.

14 2 Review of the literature

2.1 The autonomic nervous system

2.1.1 Anatomy and physiology

The structures which are known today as the peripheral ANS were morphologically fairly well known to Galen (A.D. 130–200) (Ackerknecht 1974). Later, the great Eustachius, regarding the vagus and the sympathetic nerves as two different entities, described the sympathetic nerve as a continuation of the abducens nerve (Eustachio 1563). Later still Langley called the vegetative system the ANS and he developed the notion of a division between the sympathetic and parasympathetic systems (Langley & Dickenson 1889). The ANS as it is known today is a complex neural network maintaining internal homeostasis, especially homeostasis of the cardiovascular, thermoregulatory, gastrointestinal, genitourinary, exocrine, and pupillary functions (Ravits 1997). The ANS supplies and influences virtually every organ in the body, all its functions being related to adjusting the activities of tissue and organs so that they operate at levels that are most favourable to the state of the body and to its interactions with the environment. The autonomic control of organs is effected by means of reflexes. The cell bodies of the preganglionic neurones lie in the brain or spinal cord and those of the postganglionic neurones in the autonomic ganglia. The central autonomic network integrates the input and outflow of both divisions of the ANS: after these inputs have been evaluated, a specific pattern of autonomic outflow is relayed to the periphery. This network and coordinating center balances input for the hypothalamus, amygdala, insular cortex, anterior cingulate cortex, periaqueductal gray, the parabrachial nucleus of the pons, and several medullary regions, including the ventrolateral reticular formation of the medulla and the medullary raphe (Benarroch 2008a). The integration of incoming and outcoming signals occurs mainly through the central processing activity of the nucleus tractus solitarius (NTS), which is the first relay station for all medullary cardiovascular, respiratory, and gastrointestinal reflexes (Benarroch 2008a). The insular cortex, the anterior cingulate cortex, the adjacent orbitofrontal cortex, and the amygdala are intimately connected with one another and with the hypothalamus and brain stem areas controlling the autonomic function (Critchley

15 et al. 2003). The hypothalamus contains several distinct sets of neuronal populations that innervate the sympathetic and parasympathetic preganglionic neuronal structures. It has a central role in integrating autonomic and endocrine responses and is involved both in neuroendocrine control and in coordinating homeostatic mechanisms (Saper 2002). The insula is the primary viscerosensory cortex (Gray & Critchley 2007). The anterior cingulate cortex initiates autonomic responses related to motivation and goal-directed behaviours (Luu & Posner 2003), and is also involved in the modulation of autonomic output in response to pain and other emotionally or behaviourally significant stimuli (Critchley et al. 2003). The amygdala initiates autonomic and endocrine responses and motor activation that is critical for the expression of emotional responses (Benarroch 2008a). In contrast to the parasympathetic system, the sympathetic system enables the body to respond to challenges to survival, to situations of hemodynamic collapse and to respiratory failure. Sympathetic responses include an increase in heart rate (HR), blood pressure (BP), and cardiac output; a diversion of blood flow from the skin and splanchnic vessels to those supplying skeletal muscle; bronchiolar dilation; and a decline in metabolic activity (Freeman et al. 2006). The sympathetic nervous system exits from the thoracolumbar regions of the spinal cord and synapses at the prevertebral and paravertebral ganglia. The sympathetic preganglionic neurons are organized into different functional units that control specific targets, including muscle vasomotor, splanchnic vasomotor, skin vasoconstrictor, skin vasodilatator, cardiomotor, sudomotor, and visceromotor preganglionic neurons (Jänig & Häbler 2003). In the sympathetic system, the spinal segments T1 to T3 innervate the head, T2 to T6 the upper extremities and thoracic viscera, T5 to T11 the abdominal viscera, and T12 to L3 the lower extremities and pelvic and perineal organs (Benarroch 2008b). Postganglionic sympathetic neurons exit through the ventral roots and pass via white rami communicantes on the corresponding spinal nerve to reach the paravertebral sympathetic chain. Preganglionic fibers are myelinated and cholinergic; postganglionic fibers are unmyelinated and primarily adrenergic. Most sympathetic postganglionic axons release noradrenaline, but sympathetic sudomotor and muscle vasodilator axons are cholinergic (Jänig & McLachlan 1999). The parasympathetic nervous system is largely concerned with the conservation and restoration of energy both by causing a reduction in HR and BP and by facilitating the digestion and absorption of nutrients and discharge of

16 wastes (Freeman et al. 2006). Parasympathetic outputs arise from preganglionic neurons located in the nuclei of the brain’s stem and the sacral spinal cord. Parasympathetic efferents arise from the third, seventh, ninth and tenth cranial nerves (Jänig & McLachlan 1999). Furthermore, they leave the sacral cord in the second, third and fourth sacral nerves (McLeod & Tuck 1987). Preganglionic axons are myelinated and have long peripheral projections to cholinergic synapses in the ganglia located close to the end-organs; postganglionic axons are short and cholinergic (Ravits 1997). Most preganglionic parasympathetic output from the brain is mediated by the vagus nerve innervating the heart, respiratory tract, and the entire gastrointestinal tract with the exception of the descending colon and rectum (Benarroch 2008b).

2.1.2 Cardiovascular autonomic control

The neural regulation of circulatory function is mainly effected through the interplay of the sympathetic and vagal outflows, which are tonically and phasically modulated by means of the interaction of at least three major factors: (1) central integration, (2) peripheral inhibitory reflex mechanisms with negative feedback characteristics, and (3) peripheral excitatory reflex mechanisms with positive feedback characteristics (Montano et al. 2001). Sympathetic and parasympathetic fibers innervate the atria, ventricles, coronary arteries, and resistance vessels of the peripheral circulation. Sympathetic activity increases HR, increases myocardial contractility, dilates coronary vessels, and constricts resistance vessels; parasympathetic activity does the converse, except it has little influence on the peripheral vasculature (Ravits 1997). Afferent activation originates in arterial baroreceptors located in the carotid sinus, aortic arch and various thoracic arteries, in cardiac mechanoreceptors, and in pulmonary stretch receptors (Ravits 1997). Increasing activity of the afferent system results in decreasing activity of the sympathetic efferent pathway, and vice versa. The ventrolateral medulla contains the neurons that control the vasomotor tone (Dampney et al. 2003), cardiac function (Spyer 1994) and respiration (Benarroch 2008a). The rostral ventrolateral medulla is critical for the regulation of arterial pressure and cardiac output (Guyenet et al. 2001). This region contains bulbospinal neurons that provide a largely monosynaptic input to sympathetic preganglionic vasomotor neurons (Zagon & Smith 1993). The normal low HR and respiratory sinus arrhythmia are determined primarily by the tonic firing and reflex control of parasympathetic cardiac neurons in the brain stem. These

17 neurons from which the vagal fibers arise are in the dorsal motor nucleus of the vagus and the nucleus ambiguus, and dominate the neural control of the HR under normal conditions (Wang et al. 2001). Cardiac vagal activity is diminished and unresponsive in many disease states, and a delay in the inhibitory actions of this autonomic motor system following exercise is a powerful predictor of overall mortality (Cole et al. 1999). One of the functionally important pathways innervating vagal cardiac neurons is connected with NTS neurons. Cardiovascular afferents impinge on the dorsomedial NTS, whereas respiratory afferent endings are found ventrally and ventrolaterally (Andresen et al. 2001). The NTS sends efferents as ascending neurons to higher brain nuclei, as well as to other nuclei in the brain stem that are critical for efferent sympathetic and parasympathetic activity including the nucleus ambiguus (Wang et al. 2001). Assumption of an upright posture causes translocation of approximately 800 ml of blood from the intrathoracic compartment to veins in the buttocks, pelvis, and legs (Schondorf et al. 2001). The normal compensatory cardiovascular response to this orthostatic stress is a neurogenically mediated increase in the HR and in systemic vascular resistance (Schondorf et al. 2001). The main sensory receptors involved in this orthostatic neural reflex adjustment are the baroreceptors located in the aortic arch and carotid sinuses and mechanoreceptors located in the heart and lungs (Smit et al. 1999). The peripheral chemoreflexes, located in the carotid bodies, respond primarily to hypoxemia and elicit hyperventilation, tachycardia and increased sympathetic vasoconstrictor activity (Shamsuzzaman & Somers 2001). Much less is known about the central pathways subserving cardiovascular changes that occur during exercise or that are evoked by a threatening or alerting stimulus. Recent evidence indicates that the dorsomedial hypothalamic nucleus is a critical component of the pathways mediating the cardiovascular response to an acute alerting stimulus. Long-term sustained changes in sympathetic vasomotor activity occur under both physiological conditions (e.g. a change in salt intake) and pathophysiological conditions (e.g. heart failure). There is evidence to suggest that a critical component of the pathways mediating these changes is the paraventricular nucleus of the hypothalamus (Dampney et al. 2002.)

2.1.3 Sudomotor regulation

Heat dissipation is vital for mammalian survival during exercise and heat stress (Shibasaki et al. 2006). The ANS strictly maintains internal body temperature

18 within a narrow margin of 37 °. The maintenance of a constant internal temperature depends both on vasomotor control of the cutaneuous circulation and on sudomotor control of sweating and shivering, with nonshivering thermogenesis also contributing in neonates (Egan et al. 2005). The most effective mechanism of heat loss is the evaporation of sweat secreted by eccrine sweat glands (Loewy & Spyer 1990: 343). Concurrent with cutaneous vasodilatation, the evaporation of sweat decreases skin temperature, thereby cooling the blood in the dilated skin vessels before it returns to the core (Charkoudian 2003). The hypothalamus acts as a thermostat. Thermoreceptors are present in the preoptic-anterior hypothalamus area, responding to a deviation in core temperature relative to the temperature set point (Low 2004). It contains warm sensitive neurons that initiate skin vasodilatation and sweating to dissipitate heat, and cold sensitive neurons that trigger shivering, brown fat metabolism, and skin vasoconstriction to generate and conserve heat (Boulant 2000). When core temperature exceeds the hypothalamic set point, the sympathetic nervous system generates a thermoregulatory response consisting of generalised sweating and vasodilatation (Benarroch et al. 2008). In this way radiant and evaporative heat loss restores thermal homeostasis. The exact neural pathways responsible for sweating in humans are not yet entirely understood. However, efferent thermoregulatory pathways descend through the tegmentum of the pons and the lateral part of the medullary reticular formation to the intermediolateral column (Low 2004). The postganglionic neurons supplying the skin are situated in the paravertebral ganglia (Loewy & Spyer 1990:335). Emanating postganglionic sympathetic neurons that supply eccrine sweat glands are cholinergic sudomotor axons (Low 2004). Postganglionic sympathetic fibers are distributed segmentally. The spinal segments T1–T4 supply the face, the segments T2–T8 the upper limbs, the segments T4–T12 the trunk, and the segments T10–L2 the lower limbs (Benarroch et al. 2008). The eccrine gland is the primary mechanism responsible for thermoregulatory sweating in humans (Shibasaki et al. 2006). Peripheral thermosensory neurons that detect shell temperature are also found in the skin and in the oral and urogenital mucosa (Romanovsky 2007). Human brain regions that respond to changes in skin temperature have been identified in the somatosensory cortex, insula, anterior cingulate, thalamus and hypothalamus, with evidence to suggest that the hypothalamus response codes the direction of the temperature change (Egan et al. 2005). Thermogenesis results from activation of the tectospinal and rubrospinal tracts, which synapse upon spinal motor

19 neurons to induce shivering (Vassallo & Delaney 2002). Thermoregulatory responses in a variety of animal species can be elicited by local thermal stimulation of various areas in the CNS, including several brains stem neuron groups (the reticular formation of the medulla oblongata, pons, and midbrain) and the spinal cord (Romanovsky 2007). Excitatory suprasegmental inputs from the cerebral cortex and inhibitory striatal signals are known to exist in cats (Wang 1958).

2.2 Multiple sclerosis

A French neurologist, Jean Martin Charcot, first described MS in 1868, noticing the accumulation of inflammatory cells in a perivascular distribution within the brain and spinal cord white matter or patients with intermittent episodes of neurologic dysfunction (Hafler 2004). Although the precise cause of MS has remained undetermined, MS is widely believed to be an autoimmune disorder (Dyment et al. 2004) in which the CNS myelin is attacked, resulting in focal CNS lesions and clinical symptoms. Activation of immune cells and break-down of the blood-brain barrier leads to demyelination and axonal injury. Within the active lesions, lymphocytes (CD4 T cells, CD8 T cells, and B cells) are present together with inflammatory cells of microglial and/or macrophage lineage, supporting immunopathology as an essential feature of MS (Lucchinetti et al. 2000). An estimated 2% to 5% of all people with MS have onset before the age of 16 (Duquette et al. 1987, Ghezzi et al. 1997). About two-thirds of cases of MS have their onset between 20 and 40 years of age (Compston et al. 2006:199–200). It has been estimated that the prevalence of MS in Finland is in the western health- care district of Seinäjoki and Vaasa 202 and 111 per 100 000 respectively, and in the southern district of Uusimaa 108 per 100 000 (Sumelahti et al. 2001). However, MS has an uneven geographic distribution in Finland. The incidence of MS is 8.7 per 100 000 in the western part of Finland but only 5.1 in the southern part (Sumelahti et al. 2000). MS is a disease with considerable clinical complexity. Relapses and the progression of the disability are the two basic clinical phenomena of MS. MS begins in 85% of patients with relapsing and remitting neurologic symptoms localised in the brain, optic nerve or spinal cord (Compston et al. 2006:201, 291– 297). The relapsing–remitting form of the disease evolves into the secondary progressive form within 10–20 years in the majority of patients (Martinelli Boneschi et al. 2004). A minority of patients with MS (15%) present a form of the

20 disease that is progressive from the onset, so-called primary progressive MS (Compston et al. 2006:201). Relapses are considered to be the clinical expression of acute inflammatory demyelination in the CNS, whereas progression is considered to reflect both chronic demyelination, gliosis and axonal loss (Frohman et al. 2005) and the accumulation of cortical lesions (Roosendaal et al. 2009). Relapses typically occur subacutely, with symptoms developing over hours to several days, persisting for several days or weeks, and then gradually dissipating (Hafler 2004). Gamma globulins are synthesized in the cerebrospinal fluid of patients with MS and about 95% of patients with clinically definite MS are reported to have oligoclonal IgG bands in the cerebrospinal fluid (McLean et al. 1990). The clinical features of MS often include motor weakness, paresthesias, impaired vision, diplopia, vertigo and limb ataxia (Compston et al. 2006:200– 205). In about 20–25% of all patients the initial manifestation is an episode of ON (Kinnunen 1984, Compston et al. 2006:327). Cognitive dysfunction is also common in patients with MS (Glanz et al. 2007), 40–65% of MS patients showing a marked reduction in memory, sustained attention and information processing speed (Amato et al. 2006). Though demyelination produces conduction block, it does not necessarily or even usually lead to permanent loss of function (Miller et al. 1998). Remyelination undoubtedly occurs and is occasionally extensively found in postmortem examinations (Prineas et al. 1993). Remyelination can restore conduction properties to axons and thereby restore neurological function. However, it is not a prerequisite for recovery of functions and in adults it is exceptional for it to be extensive enough to restore normal latencies to evoked potentials (Jones 1993). Axon loss is the major cause of irreversible disability in patients with MS, and several mechanisms lead to it, including inflammatory secretions, loss of myelin- derived support, disruption of axonal ion concentrations, energy failure and Ca(2+) accumulation (Dutta & Trapp 2007). Although MS is generally considered a disease of the white matter, its pathology can also be found in the deep cerebral nuclei (Cifelli et al. 2002) and cerebral cortex (Kidd et al. 1999, Geurts et al. 2005). Brain atrophy is also widespread in MS (Bakshi et al. 2001, Horakova et al. 2008). There is increasing evidence to suggest that the severity of the clinical manifestations of MS does not simply depend on the extent of tissue destruction, but rather reflects a complex balance of tissue damage, tissue repair and cortical reorganization. Functional MRI has recently provided information about the extent and nature of brain plasticity in patients with MS, showing an altered

21 recruitment of regions normally devoted to the performance of a given task and/or the recruitment of additional areas which are not typically activated by healthy people (Rocca & Filippi 2007). An accurate and reliable diagnosis of MS is of great importance, but a specific test for the disease does not exist. In practice, MS is diagnosed on the basis of the dissemination of lesions in time and space, combining the history, clinical examination and laboratory findings. The Poser criteria for MS have been developed as guidelines for research protocols (Poser et al. 1983). These criteria consist of two major groups, definite and probable MS, each with two subgroups, clinical and laboratory supported. The diagnosis of clinically definite MS requires either the occurrence of at least two attacks and clinical evidence of two separate lesions, or the occurrence of two attacks with clinical evidence of one lesion and paraclinical evidence of another separate lesion. The most recent set of diagnostic criteria are the 2005 revisions of the McDonald Criteria, incorporating MRI, cerebro spinal fluid, and evoked potential studies to expand the clinician’s ability to demonstrate lesion dissemination in time and space (Polman et al. 2005). The Kurtzke Functional Systems and Expanded Disability Status Scale (EDSS) score (Kurtzke 1983) remain the most widely used scoring system for MS. Treatment options specifically target the inflammatory phase of MS and include immunomodulators (i.e., interferon betas, glatiramer acetate and natalizumab) and an immunosuppressant, mitoxantrone. Early treatment with these disease-modifying agents is desirable in order to reduce the progression of the disease and to limit long-term disability (Rizvi & Agius 2004). Primary progressive MS is unresponsive to immunosuppressive therapies (Anlar 2009). MS patients benefit from physical exercise, showing increased upper extremity endurance and walking speed improvement (Romberg et al. 2004). The mortality of MS patients is only slightly higher when compared with that in the general population, the number of years of life lost ranging from 5 to 10 (Ragonese et al. 2008). Mortality is higher for older patients and for those with a longer disease duration (Ragonese et al. 2008).

2.3 Optic neuritis

ON is a clinically isolated syndrome of a demyelinating nature that is often the initial attack of relapsing–remitting MS. ON usually presents with acute unilateral visual loss associated with periocular pain, abnormal visual acuity and afferent

22 pupillary defect (Pirko et al. 2004). In most cases the visual prognosis after a first attack of ON is excellent (Compston et al. 2006:328–330). At the median six-year follow-up in one study, 48% of ON patients had converted to clinically definite MS and 52% had remained with the clinically isolated syndrome (Swanton et al. 2009). In addition, the cumulative probability of developing MS by 15 years after onset of ON was 50% (95% confidence interval, 44–56%) and strongly related to the presence of lesions on the baseline non-contrast-enhanced MRI of the brain (The Optic Neuritis Study Group 2008). Strong confirmation of ON involvement in MS is provided by the fact that autopsies performed on MS patients have revealed optic nerve lesions in up of 94 – 99% of cases (Ikuta & Zimmerman 1976, Toussaint et al. 1983).

2.4 Magnetic resonance imaging

MRI has become the major confirmatory test for MS, by sensitively detecting disseminated lesions in the CNS (Barkhof & van Walderveen 1999). MS plaques are seen in 90–97% of definite MS patients, being hyperintense on T2 and proton- density weighted images (Pyhtinen et al. 2006). However, in established MS the correlations between T2 abnormalities and disability are modest (Miller et al. 1998). The term given to this lack of a close correlation between the MRI and the clinical status and disability in MS is the clinicoradiologic paradox (Barkhof 2002). Reasons for the clinicoradiologic paradox include the lack of pathologic specificity of MRI, the frequent lack of inclusion of spinal cord imaging, the insensitivity of MRI for detecting pathology in the normal-appearing white matter, as well as the suboptimal measures of disability used in correlations with MRI. Firstly MRI lesions are neither specific nor sensitive to axonal loss, the major pathological substrate for irreversible disability in MS (Compston et al. 2006:735). Secondly the normal-appearing white matter often has a reduced myelin density, axonal loss and microglial activation (Allen et al. 2001). Thirdly EDSS is neither quantitative nor continuous, is poorly responsive to change and mixes impairment with disability (Compston et al. 2006:195–196). Three parameters (T2-weighted, T1-weighted and proton density) determine the appearance of MRI (Compston et al. 2006:351–358). The measurement of T2 hyperintensity has been a common secondary end point in clinical trials (Compston et al. 2006:734–736). Gadolinium uptake by an MS lesion indicates blood brain barrier breakdown (Compston et al. 2006:356–358). T1 hypointensities represent a spectrum of lesions with an increased proportion of

23 tissue destruction compared with T2 hyperintensities (Compston et al. 2006:358). Proton density weighted images are useful in better showing the periventricular lesions because the cerebrospinal fluid signal is less intensive than those on T2- weighted images (Pyhtinen et al. 2006). Although MS lesion plaques can be found throughout the brain, they have a predilection for periventricular white matter and tend to have an ovoid configuration with the major axes perpendicular to the ventricular surface (Horowitz et al. 1989). At the initial stage of the disease process, the lesions are typically thin and appear to be linear (Dawsons`s fingers), a phenomenon probably associated with the inflammatory changes around the long axis of the medullary vein that create the dilated perivenular space (Ge 2006). Histopathologically, such perivascular inflammation has been thought to play a primary role in the disruption of the blood brain barrier, in myelin breakdown, and in the formation of new lesions (Adams et al. 1987). New symptoms are usually accompanied by new lesions being detected with MRI (Smith et al. 1993). On the other hand, clinically silent lesions are also often found (Barkhof & van Walderveen 1999). The opening of the blood-brain barrier may be the earliest event of an MS lesion. Gadolinium chelates, in combination with T1-weighted images, are sensitive markers of this abnormality (Miller et al. 1998). It has also emerged that destructive or degenerative changes with axonal loss in lesions are relatively common, and axonal loss seems likely to be an important contributor to the atrophy observed in MS (Miller et al. 2002). The spinal cord is known to be frequently involved in MS and the prevalence of cord abnormalities in established MS is 74–85% (Pyhtinen et al. 2006). Up to 75% of plaques occur in the cervical cord (Tartaglino et al. 1995). Evidence indicates that spinal cord pathology causes significant disability in MS (Furby et al. 2008, Stankiewicz et al. 2009). Spinal cord MS plaques are characteristically peripherally located, are less than two vertebral segments in length, and occupy less than half the cross-sectional area (Tartaglino et al. 1995). In proton density- weighted images, the spinal cord can be seen as isointense with the surrounding cerebrospinal fluid, and any increase in the signal of the spinal cord is easily visible (Pyhtinen et al. 2006). Many methods have been exploited in attempts to quantify lesion burden. In the past few decades MS imaging has frequently been used to assess the disease burden, which is often based on quantification of the T2 lesion load (i.e., the total lesion volume and/or number) (Ge 2006). In addition to lesions, another imaging hallmark of MS is brain atrophy, which is considered to be a net accumulative disease burden as the ultimate consequence of all types of pathologic processes

24 found in the brain (Miller et al. 2002). Brain atrophy in MS usually appears as enlarged ventricles and the reduced size of the corpus callosum (Ge 2006). It has been suggested that quantitative MR-derived metrics should be used in the context of MS trials to provide additional measures of the outcome (Martinelli Boneschi et al. 2004). ON is a frequent initial manifestation of MS. In one study, the 10-year risk of developing MS after an initial episode of ON was 56% if patients had one or more typical lesions on the baseline MRI scan of their brain, those with no lesions having only a 22% risk (Beck et al. 2003). Moreover, white matter abnormalities typical of MS are found with MRI in 48% to 62% of patients with monosymptomatic ON (Frederiksen et al. 1989, Jacobs et al. 1991, Beck et al. 1993).

2.5 Autonomic dysfunction in MS

2.5.1 General aspects

Various clinical manifestations of autonomic failure have been recognized in MS patients. Plaques of demyelination may disrupt the central autonomic network (Vita et al. 1993, Haensch & Jörg 2006). Vesicourethral dysfunction is frequent, and the prevalence of reported detrusor and sphincter disorders range from 30% to 96.8% (de Seze et al. 2007). Urogenital symptoms allegedly derive mainly from spinal cord involvement, so that some correlation between lower limb and bladder dysfunction is often clinically apparent (Betts et al. 1993). Sexual dysfunction is also a common problem (Secil et al. 2007), worsening the quality of life (Zorzon et al. 1999). Erectile failure has been estimated to affect between 50% and 75% of men with MS (Zorzon et al. 1999). Moreover, in relapsing– remitting MS, pontine lesions can also cause sexual dysfunction (Zivadinov et al. 2003), while in primary progressive MS voiding disturbances are associated with increasing brain and spinal cord abnormalities (Ukkonen et al. 2004). MS can also cause autonomic dysfunction affecting the pupil (Pozzessere et al. 1997, de Seze et al. 2001a, Surakka et al. 2008). Sleep disturbances associated with leg spasms, pain, immobility, nocturia or medication have also been noted in many patients with MS (Tachibana et al. 1994). Sleep disturbances are much less commonly associated with nocturnal respiratory insufficiency (Tachibana et al. 1994). Finally, MS is often associated with gastrointestinal disturbances,

25 constipation being found in one study in 43% of the MS patients and fecal incontinence occurring at least once in the preceding 3 months in 51% (Hinds et al. 1990).

2.5.2 Cardiovascular dysfunction

Several MS studies have reported abnormalities in cardiovascular reflexes involving both sympathetic and parasympathetic dysfunction. In contrast to bladder dysfunction in MS the clinical relevance of these cardiovascular abnormalities is less clear (Merkelbach et al. 2006). Several studies have shown cardiovascular autonomic regulation failure in MS patients, manifesting itself both in the HR responses to deep breathing and in the HR and BP responses in the tilt table test (Senaratne et al. 1984, Nordenbo et al. 1989, Anema et al. 1991, Vita et al. 1993, Drory et al. 1995, Acevedo et al. 2000, Gunal et al. 2002). Abnormal cardiovascular responses have been found in 25% to 53% of MS patients participating in different autonomic studies (Anema et al. 1991, Frontoni et al. 1996, Flachenecker et al. 1999, McDougall & McLeod 2003). However, only a few studies have reported cardiovascular symptoms in MS patients. Orthostatic intolerance has frequently been reported in up to 50% of MS patients (Acevedo et al. 2000, Flachenecker et al. 1999), but abnormal significant orthostatism has been found in only 2–13% of MS patients (Anema et al. 1991, Flachenecker et al. 1999, McDougall & McLeod 2003). In one study, when differences in HR variability were evaluated in and contrasted between two patients groups determined according to an MS diagnosis having been made either more than or less than five years previously, the “more than five-year” group had lower parasympathetic activity than the “less than five-year” group (Mahovic & Lakusic 2007). Finally, dysautonomy seems more likely to occur in MS patients with more severe clinical disability (Merkelbach et al. 2006).

2.5.3 Sudomotor dysfunction

MS patients may display various disturbances in sudomotor functions. Demyelinating lesions located among the central thermoregulatory pathways may cause regional or global anhidrosis, the risk being greater in advanced MS (Spies 2008). Areas of diminished sweating have been qualitatively identified in MS patients by using quinizarin powder being placed on the skin of individuals followed by exposure to a heat stress (Noronha et al. 1968, Vas 1969, Cartlidge

26 1972). Quinizarin powder, normally gray in colour, changes to a deep blue when exposed to sweat, giving a visual estimate of sweating (Davis et al. 2005). No differences have been noted between sweat gland density in MS patients compared to those of healthy controls (Davis et al. 2005). On the other hand sweat gland output has been shown to be lower in MS patients than in control subjects, and thus it has been surmised that the sweat glands are in fact intact, but MS patients cannot activate their sweat glands effectively because of a failure in sympathetic cholinergic control (Davis et al. 2005). The relevance of sweating dysfunction has been thought to be low (Merkelbach et al. 2006). Sudomotor dysfunction in MS patients has also been measured by the sympathetic skin response (SSR), i.e. the potential generated by sweat in response to different stimuli (Gutrecht 1994). The SSR is a multisynaptic somatosympathetic reflex and it can be diminished or abolished by any lesion along the arch (Caminero et al. 1995). MS patients have been shown to have impairment in the functions of their sudomotor pathways, and SSRs may be absent (De Seze et al. 2001b, Gunal et al. 2002, McDougall & McLeod 2003). More detailed investigations have also found SSR latency and/or amplitude abnormalities (Gutrecht et al. 1993, Caminero et al. 1995, Drory et al. 1995, Elie & Louboutin 1995, Linden et al. 1995, Alavian-Ghavanini et al. 1999, Nazliel et al. 2002) especially in the feet (Kodounis et al. 2005).

2.6 Autonomic dysfunction in optic neuritis

Pupil response to light flux increments is abnormal in severe ON. Although pupillary dysfunction is well known (Moro et al. 2007), no other ANS studies have been published on ON patients.

2.7 Evaluation of autonomic functions

2.7.1 General aspects

The evaluation of the ANS is time and labour consuming. When autonomic neuropathy is suspected, noninvasive tests may be used to determine whether sympathetic and/or parasympathetic pathways are involved. Simple and reliable methods for measuring the autonomic functions were lacking until the 1970`s when a new generation of simple bedside tests for autonomic function was

27 developed (Piha 1988). These non-invasive tests most widely used measure the end-organ response to different physiological provocations (Freeman 2006) and are based on changes in HR, on the length of R–R interval, and on the BP following some stimulus. These autonomic tests measure both cardiovagal and sympathoneural functions. A standardized battery for the screening of autonomic dysfunction has been recommended (Consensus statement 1996). Combining cardiovascular autonomic tests with sudomotor examination aims to improve the detection of autonomic failure. Sudomotor tests assess sympathetic cholinergic function.

2.7.2 Cardiovascular autonomic reflexes

An assessment of cardiovascular nerve damage can be made from the combined results of several cardiovascular autonomic tests. Various manoeuvres are suitable for activating the sympathetic and parasympathetic system. The commonly used cardiovascular tests in clinical practice are based on the measurement of HR and BP reflex changes as responses to adequate stimuli. The reflexive cardiovagal function can be tested by measuring the HR response to deep breathing, a method first introduced by Wheeler and Watkins (Wheeler & Watkins 1973). The subject lies in a quiet room, and after a period of rest, during which the HR stabilizes, the subject breathes deeply and steadily, but not maximally. Typically, the test is performed over 6 respiratory cycles (Freeman 2006). The beat to beat variability of HR is predominantly mediated by the vagus nerve. The amplitude of the beat to beat variation with respiration is the most commonly used measure although several additional measures are used, including the standard deviations (SD) of the R–R interval, the inspiratory ratio (E:I ratio), and the mean circular resultant (Freeman 2006). HR variability is known to decrease with age (Low et al. 1997). The maximal HR response in subjects with an autonomic neuropathy occurs at lower respiratory rates (Mackay 1983). The Valsalva manoeuvre is known to influence the HR, but it actually evaluates the baroreflex arc and its sympathetic and parasympathetic responses (Hilz & Dutsch 2006). During the manoeuvre, the person breathes into a mouthpiece that is connected to a manometer and maintains an expiratory pressure of from 35 mmHg to 40 mmHg for 15 seconds while an ECG record is made (La Rovere et al. 2008). The hemodynamic response to the resulting sudden, transient intrathoracic and intra-abdominal pressure in normal subjects may be subdivided into 4 phases (Freeman 2006). The Valsalva ratio is used as an index

28 of the baroreflex-mediated bradycardia and is calculated as the ratio of the highest HR during expiration and the lowest HR during the first 20 seconds after the expiratory strain (Hilz & Dutsch 2006). Cardiovascular adaptation to a prolonged orthostatic challenge can be tested by means of passive head-up tilting or active standing. The cardiovascular changes occurring during head-up tilt include a gradual increase in both BP and HR, but no major changes occur in the systolic pressure (Hilz & Dutsch 2006). Patients with adrenergic failure have a progressive reduction in BP, and the HR response is also typically attenuated (Low & Sletten 2008). The hemodynamic response to standing results in an abrupt increase in HR that peaks at approximately 3 seconds, followed by a more gradual increase in HR, mediated by the sudden inhibition of vagal while the more gradual increase is due to further vagal inhibition and increased sympathetic nervous activity (Freeman 2006). Both standing and tilting from the supine position result in pooling of blood in the sub- diaphragmatic venous system. However, a significant fall in arterial pressure is prevented by compensatory tachycardia and vasoconstriction of the resistance and capacitance vessels in the splanchnic, musculo-cutaneuous and renal vascular beds (Smit et al. 1999). Studying the HR changes to standing (30:15) ratio is indicated in testing the integrity of parasympathetic cholinergic (cardiovagal) function (Ravits 1997). Orthostatic hypotension is defined either as a decrease in systolic BP greater than 20 mmHg or as a decrease in diastolic BP greater than 10 mmHg within 3 minutes of standing (Lahrmann et al. 2006). The sustained handgrip test requires the patient to apply and maintain a grip at 30% maximal activity for up to 5 min if possible (Ravits 1997). The consequent increase in sympathetic activity and vasoconstriction induces a BP rise that is considered to reflect sympathetic autonomic activity (Hilz & Dutsch 2006). Analysis of HR variability involves first taking a sequence of R–R intervals and then calculating the successive R–R interval differences. This approach allows quantification of the SD of a given R–R interval sequence (Freeman et al. 2006), estimating both the parasympathetic and sympathetic inputs into the HR control.

2.7.3 Sudomotor functions

Transepidermal water loss (TEWL) describes the total amount of water lost through the skin, a loss that occurs constantly by passive diffusion through the

29 epidermis. An evaporimeter determines TEWL by measuring the pressure gradient of the boundary layer resulting from the water gradient between the skin surface and ambient air (Levin & Maibach 2005). The degree of sweating can be determined by transepidermal water loss (TEWL) measurement on different body areas during exercise (van Houte et al. 2008) or passive heating (Korpelainen et al. 1993a). TEWL measurements have also been used to study the fluctuations of sweating in Parkinson's disease with wearing-off phenomenon (Pursiainen et al. 2007). SSR stands for the momentary change in the electrical potential of the skin due to synchronized activation of eccrine sweat glands under the control of the sympathetic nervous system (Caminero et al. 1995). When elicited by electrical stimulation, the response uses a reflex arch, which includes large myelinated sensory fibers, central relays and efferent sympathetic pre- and postganglionic nerve fibers, which activate eccrine sweat glands in the skin (Nazliel et al. 2002). Little is known about the central processing of the SSR responses. Animal studies have shown that the sensorimotor, the limbic cortex, the anterior hypothalamus and the brain stem facilitatory system are involved (Vetrugno et al. 2003). Any arousal stimuli can be used to activate sudomotor nerve fibers and thereby change skin resistance (Hilz & Dutsch 2006). Stimuli commonly used include (a) an electrical single square pulse of 0.2 ms duration and 20–40 mA intensity just sufficient to produce a painful sensation, applied either to the median nerve at wrist or to any other nerve, (b) a single deep inspiration or cough, (c) an auditory click of varying intensity, and (d) magnetic stimulation (Arunodaya & Taly 1995). SSR can be recorded using a conventional electromyography apparatus (Arunodaya & Taly 1995). The stimulus must be delivered at rates >1/min and preferably at an irregular rate in order to avoid habituation (Gutrecht 1994). All normal subjects <60 years of age demonstrate SSRs (Gutrecht 1994). Individual responses are normally studied by choosing the best potentials for measurement (Vetrugno et al. 2003).

30 3 Aims of the study

The aims of the present study were first to investigate the cardiovascular and sudomotor autonomic control in clinically definite MS patients, and to correlate these findings with quantitative MRI scans of the CNS, and second to examine the sudomotor functions in patients with ON and to correlate these findings with MRI scan results. The more specific aims of the individual studies were: 1. To evaluate the cardiovascular autonomic control in clinically definite MS patients with a standardized battery of cardiovascular tests. 2. To evaluate autonomic functions in MS patients by recording SSRs. 3. To study sudomotor functions in MS patients by using an evaporimeter. 4. To evaluate sudomotor functions in ON patients by recording SSRs and by using an evaporimeter.

32 4 Subjects and methods

4.1 Subjects

This study was carried out in the Departments of Neurology, Clinical Neurophysiology and Diagnostic Radiology at the Oulu University Hospital. The studies were carried out according to the principles of the Declaration of Helsinki. All patients and control subjects gave their informed consent before their inclusion in the study. All the MS patients had clinically definite MS according to the criteria established by Poser (Poser et al. 1983). The MS patients were enrolled consecutively, but subjects with relapses in MS during the previous six months were excluded from the autonomic test protocol. The severity of the MS was evaluated with the EDSS score (Kurtzke 1983). All the patients were evaluated with MRI of the brain and the spinal cord. In addition, the cardiovascular and the sudomotor tests were performed in all the patients and the control subjects. All the ON patients had a history of acute unilateral ON with typical symptoms and typical courses for the disease. No cause of ON was found other than primary demyelination. An experienced ophthalmologist verified the diagnosis in all the cases. Two patients had recurrent ON: one female patient had suffered from her first bout of ON 5 years earlier, and another female patient 2 years earlier. The remaining patients had no previous history of neurological or visual symptoms. The sudomotor examinations and MRI scans were performed at the earliest 1 month (mean 3.2, SD 2.0 months; range 1–8 months) from the onset of visual symptoms of ON. Neurological impairment in the ON patients was evaluated with the EDSS score. The ON patients were also followed for a mean period of 12 years 6 months. The follow-up was performed by using medical records and phone calls made to the patients. None of the MS/ON patients and controls used any medication affecting the ANS, or had any other diseases which could influence the function of the autonomic system. All the MS and ON patients underwent a complete general and neurological examination by the same neurologist and were also interviewed in detail about autonomic symptoms. The sex- and age-matched control groups both in the MS and ON studies consisted of healthy hospital personnel, their healthy relatives and friends. The protocol was approved by the local Ethics Committee of the Medical Faculty.

33 In Study 1, 51 patients with clinically definite MS and 50 healthy controls were studied. The cardiovascular autonomic control was studied with a standardized battery of cardiovascular tests, and these findings were correlated with the brain MRI lesion loads in different brain regions. In Study 2, the SSRs were studied in 27 clinically definite MS patients and in 27 healthy controls, and the SSR findings were correlated with the brain MRI lesion loads and the spinal cord MRI findings. In Study 3, 29 clinically definite MS patients and 15 healthy controls were exposed to passive heating, and sweating was measured by using an evaporimeter. The sweating parameters were correlated with the brain MRI lesion loads and the spinal cord MRI findings. In Study 4, sudomotor functions were studied by using an evaporimeter and SSR method in 13 ON patients and 14 (the evaporimetry study) and 22 (the SSR study) healthy controls. The sweating parameters were correlated with the brain MRI lesion loads and the spinal cord MRI findings. The clinical characteristics of the patients and healthy controls in the various studies are presented in Table 1, Table 2, Table 3 and Table 4.

Table 1. The clinical characteristics of the MS patients and healthy controls in the cardiovascular autonomic function study.

STUDY 1 MS patients Controls N 51 50 Female/male 25/26 25/25 Age, mean years (SD) 39.5 (10.2) 39.3 (9.6) Age (range years) 21–61 22–59 Duration of MS, mean (SD) years 12.2 (8.2) EDSS, range 0–9 EDSS, mean (SD) 4.3 (2.4)

34 Table 2. The clinical characteristics of the MS patients and healthy controls in the SSR study.

STUDY 2 MS patients Controls N 27 27 Female/male 13/14 13/14 Age, mean years (SD) 38.4 (8.3) 39.7 (8.7) Age (range years) 23–60 28–56 Height, mean cm (SD) 169.2 (8.1) 172.7 (11.1) Duration of MS, mean (SD) years 6.1 (4.9) EDSS, range 0–9 EDSS, mean (SD) 4.2 (2.5)

Table 3. The clinical characteristics of the MS patients and healthy controls in the evaporimeter study.

STUDY 3 MS patients Controls N 29 15 Female/male 15/14 9/6 Age, mean years (SD) 35.8 (7.7) 34.6 (8.9) EDSS, range 0–9 EDSS, mean (SD) 4.3 (2.3) Duration of MS, mean (SD) years 6.2 (5.7)

Table 4. The clinical characteristics of the ON patients and healthy controls in the evaporimeter and SSR study.

STUDY 4 ON Patients Controls (TEWL-study) Controls (SSR-study) N 13 14 22 Female/male 9/4 8/6 13/9 Age, mean years (SD) 29.2 (7.3) 33.0 (6.6) 32.3 (5.8) Age (range years) 20–41 23–43 19–42 EDSS, range 0–1.5 EDSS, mean (SD) 0.62 (0.62) Height, mean cm (SD) 170 (10) 171.6 (11)

4.2 Cardiovascular autonomic reflexes

The cardiovascular autonomic function tests of the patients and controls were performed under standardized conditions in the same quiet room with a stable temperature. The cardiovascular tests were carried out using a standardized battery (Suominen 1997, Turkka et al. 1997). First, the patient’s maximum contraction power of their dominant hand was measured three times with a

35 dynamometer for the isometric work test. Second, during a 30-minute resting period, the BP was measured three times with an automatic arm sphygmomanometer. Then, with the patient lying in a supine position on the tilt table, five further tests were performed: 1. Normal breathing test: the HR variation was recorded during normal breathing. The consecutive R–R intervals for a period of one minute were measured, and the SD of the intervals was used as the variable. 2. Deep breathing test: the subject was instructed to perform six consecutive deep but not maximal inspirations and expirations while lying supine at a rate of 6 breaths/min. The ratios of the longest (expiration) to the shortest (inspiration) R–R intervals of 5 consecutive breathing cycles were calculated. The test was performed twice and the higher median of the R–R interval ratios (the “maximum-minimum (max-min) ratio”) was used as the variable. 3. Valsalva manoeuvre: the HR response was recorded during respiratory strain. The patient with head slightly elevated blew into a mouthpiece for 15 seconds and maintained a forced expiratory pressure of up to 40 mmHg or at least over 50% of maximum blowing capacity. The ratio of the longest R–R interval after blowing and the shortest one during blowing was calculated. The highest ratio of 3 manoeuvres was used as the ”Valsalva ratio”. 4. Tilt table test: the patient was raised quickly (within 2 seconds) from a horizontal to a vertical position on a tilt table with a foot board. The ratio of the longest R–R interval around beat 30 (20–40) to the shortest beat around beat 15 (10–20) was used as the ”30:15” ratio. The BP was measured at rest, immediately after tilting, and at two and seven minutes after tilting. The BP response was quantified as the largest drop or lowest increase in systolic and diastolic pressure. 5. Isometric work test: the largest increase in systolic and diastolic BP was recorded during a 5-minute period of sustained handgrip with a dynamometer maintained at 30% of the previously ascertained maximum voluntary force.

The ECG and breathing signals (using a nasal thermistore) were monitored continuously during these five tests, conveyed through an A/D converter with a sampling frequency of 320 Hz to a PC computer, analysed off-line using an automatic program package which allowed visual checking of the raw ECG and breathing signal.

36 4.3 Sympathetic skin responses

The tests to measure the SSRs of the patients and controls were performed under standardized conditions in the same quiet room with a stable temperature. The patient was kept awake and relaxed in a lying position. The SSRs were provoked by using two types of stimulation separately. An auditory click (0.1ms, 120 dB) was delivered to both ears, and an electrical single square pulse (0.5ms, intensity adjusted from 20% to 30% above the motor threshold) was delivered to stimulate the median nerve at the wrist. To prevent response habituation, both the auditory and electrical stimuli were delivered 4 times at irregular rates, with intervals longer than 45 seconds. Recording surface Ag/AgCl electrodes were attached to the palm and dorsum of both hands as well as to the sole and dorsum of both feet. SSRs were recorded simultaneously from the hands and feet by using a standard EMG machine (Counterpoint®, Dantec, Skovlunde, Denmark) with an amplifier gain of 0.1–2 mV and filter settings at 0.2–50 Hz. Skin temperatures at the recording areas were measured in all the recording sessions. The data were sampled digitally and transferred to a computer for the off-line analyses of the SSRs. Latencies were measured from the beginning of the stimulus to the onset of the response from the baseline. Amplitudes were taken from the peak to peak of the recorded waves and the largest amplitude was used for the analyses.

4.4 Evaporimetry measurements

The measurements were always performed in the same room with a stable temperature of 23–24 °C and no airflow. All the measurements were performed in the afternoon, between 3 and 5 p.m., before the patients and controls had had their dinner, in order to exclude gustatory sweating. Subjects remained lying down supine on a comfortable table wearing pants only. Peripheral sweat production was induced by local heating. The heating stimulus being provided by six standard thermo packages (75 °C/1000W) placed on the abdomen and chest. A thick cloth was inserted between the skin and the thermo packages to avoid skin burns. The subject was covered with a non-heat penetrating blanket from the level of the neck to the level of the knees. Transepidermal water loss (TEWL) (= sweating) was measured by an evaporimeter (Evaporimeter EP1, Servo Med AB, Sweden) which determined the skin water loss by calculating the vapour pressure passing through the boundary layer surrounding the skin with special sensors in a single probe. The probe was placed manually on the skin surface and the sweating

37 was recorded at 5 sites on both sides of the body: forehead, front of the forearm, dorsal surface of the hand, lateral leg and dorsum of the foot. Sweating was measured before the heating stimulus (baseline) and at 5-minute intervals up to 15 minutes after the induced heating. Tympanic temperature (Ttymp) of the right ear was measured both before and immediately after sweating measurements with an infrared tympanic thermometer (Thermoscan Pro-Lt, Thermoscan Inc., San Diego, CA, USA) approximating the body core temperature.

4.5 Magnetic resonance imaging

MRI was performed using a 1.0 T superconducting unit (Magnetom, Siemens, Erlangen, Germany). T2 and proton density-weighted sagittal and axial turbo spin echo images (TR 3500, TE 19, 93) were obtained through the brain with a 5 mm section thickness, a 1.5 mm intersection gap, a 23 cm FOV, a 192 x 256 matrix and one acquisition. The axial images were angled according to the inferior edge of the callosal genu and splenium. The volumes of hyperintense lesions in the brain were always measured by the same neuroradiologist on proton density- weighted axial images. A semi-automatic bounded two-dimensional seed fill segmentation technique was used. The segmentation was performed on a slice-by- slice basis by first setting the threshold levels. A seed point was placed by clicking on the image, and the radius of the circle that gives the outer boundary for the 2D seed fill was adjusted by dragging the mouse. The lesion load was measured in 16 different areas including the right and left medulla oblongata, pons, midbrain, cerebellum and temporal, occipital, parietal and frontal lobes. The posterior and superior borders of the temporal lobe were the trigonum and the Sylvian fissure, respectively. The level of the superior border of the splenium was considered as the border between the occipital and parietal lobes, and the central fissure between the frontal and parietal lobes. The caudate heads were included in the frontal lobe measurements, while the lentiform nuclei, the thalami and the areas around them were included in the temporal lobe measurements. To prevent the measurement of overlapping lesions a different algorithm was used when lesions occupied more than one anatomical area. The spinal cord lesions were evaluated by two observers using the hard copies. Each segment from C1 to Th 12 was evaluated separately and considered positive if a hyperintense lesion was observed in the sagittal proton density-

38 weighted and/or in the T2-weighted images. The axial images were used to confirm suspected lesions in the sagittal images.

4.6 Statistical analyses

The values of the HR responses (after logarithmic transformation) were corrected for the mean age and the mean baseline of the R–R intervals separately for the patients and the controls using multiple regression, since cardiovascular autonomic responses have been shown to be dependent on both age and HR (Wieling & Karemaker 1999). The values of the BP responses during isometric work were adjusted only for the mean age. Covariance analysis (ANCOVA) was used to compare the HR and BP responses of the patients with those of the controls. The TEWL values of the MS/ON patients and controls were compared with each other using covariance analysis, and since sweating has previously been shown to be dependent on age (Inoue et al. 2004), age was used as a covariant. The values of the SSR responses of the MS/ON patients and controls were also compared with each other using covariance analysis, and because SSRs have been shown to be dependent on age (Drory & Korczyn 1993), height (Dettmers et al. 1993) and skin temperature (Deltombe et al. 1998), these three factors were used as covariants. The Pearson correlation coefficient was calculated for each patient to determine whether there was a relationship between the MRI findings, EDSS scores, disease duration, TEWL values, SSR parameters or autonomic symptoms, and the actual P-value was determined.

40 5 Results

5.1 Cardiovascular autonomic reflexes in MS patients

Fifty MS patients were able to satisfactorily complete the deep breathing test and 49 the tilt table test. The HR responses to the deep breathing test (the max-min ratio, p < 0.05) and to the tilt table test (the 30:15 ratio, p < 0.001) were significantly lower in the MS patients than those in the controls (Table 5). The patients did not differ from the controls in their responses to normal breathing and in the Valsalva manoeuvre. In the tilt table test the BP responses (diastolic p < 0.001, systolic p < 0.05) at seven minutes were significantly impaired in the MS patients (Table 6). Thirty-four patients (18 women and 16 men) were able to complete the isometric test at 30% of their maximum voluntary power during the 5-minute period of sustained handgrip, and no significant differences were found between the MS patients and the control group. When compared to our laboratory normal values (one test outside the 95 percentile of the controls), 9 MS patients (18%) [(EDSS 4.2 (2.3)] had clinically abnormal values in cardiovascular autonomic tests. Eight patients had abnormal values in one of five different tests and 1 patient had abnormal values in two different tests. The EDSS score correlated significantly with the diminished SD of the HR variation during normal (p < 0.001) and deep breathing (p < 0.001), with the impaired Valsalva ratio (p < 0.01) and the systolic BP responses (p < 0.05) in the isometric test. Dysautonomic symptoms were common. Thirty-nine patients (78%) had symptoms of bladder dysfunction. However, these symptoms did not correlate significantly with cardiovascular reflex test results. Twelve MS patients (24%) had symptoms of diminished sweating, twenty-one (42%) had symptoms of orthostatism, and twenty-six patients (52%) had obstipation, but none of these symptoms had any correlation with the cardiovascular parameters. Fifteen of 26 male MS patients (58%) had partial or complete impotence with no correlation with the cardiovascular autonomic parameters.

41 Table 5. HR responses to normal breathing (SD), deep breathing (Max–min ratio), the Valsalva manoeuvre (Valsalva ratio) and tilt table test (30:15 ratio) in patients with MS and in controls.

Variable MS Patients Controls SD of R–R intervals 42.13 (22.92) 50.38 (21.55) Max–min ratio 1.28 (0.13)* 1.35 (0.16) Valsalva ratio 2.09 (0.46) 2.10 (0.49) 30:15 ratio 1.14 (0.09)*** 1.23 (0.14) *p < 0.05, ***p < 0.001 different from the controls using analysis of covariance (ANCOVA).

Table 6. Blood pressure (BP) changes (mmHg) in the tilt table test in the MS patients and controls.

Variable MS Patients Controls BP syst. 0 min -0.69 + 8.11 1.80 + 10.66 BP syst. 2 min -1.15 + 10.42 2.17 + 9.24 BP syst. 7 min -2.76 + 10.00* 1.73 + 9.57 BP diast. 0 min 1.53 + 7.96 2.83 + 9.65 BP diast. 2 min 2.88 + 6.88 4.19 + 5.64 BP diast. 7 min 0.38 + 9.73*** 4.86 + 6.19 *p < 0.05, ***p < 0.001 different from the controls.

5.2 Sympathetic skin responses in MS patients

SSRs could be elicited from the hands and feet in all the control subjects using both auditory and electrical stimuli. However, in three MS patients no responses could be elicited either by auditory or electrical stimuli. Moreover, four MS patients showed no responses to both auditory and electrical stimuli in one or both feet, and one MS patient had no responses to auditory stimuli alone in either foot. The patients [EDSS 6.8 (1.4)] with unelicitable auditory SSRs (aSSRs) in at least one extremity showed a more severe MS (p < 0.001) than the patients [EDSS 3.1 (2.0)] with preserved aSSRs. Similarly, the patients [EDSS 6.9 (1.4)] with absent electrical SSRs (eSSRs) in at least one extremity showed a more severe MS (p < 0.001) than the patients with preserved eSSRs [EDSS 3.3 (2.1)]. The SSR amplitudes in the feet of the MS patients were attenuated, the aSSRs (Table 7) being significantly so on the right (p < 0.01) and the eSSRs (p < 0.01) on both sides (Table 8). Both the latencies of the aSSRs (p < 0.05) and the eSSRs (p < 0.01) in feet (Figure 1) were significantly prolonged on both sides. However,

42 in the hands only the eSSRs showed abnormal amplitudes on the right (p < 0.05) and left (p < 0.01), and prolonged latencies on both sides (p < 0.01) (Table 8). Dysautonomic symptoms were common. Eleven patients (41%) had symptoms of orthostatism. Twenty-two patients (81%) had symptoms of bladder dysfunction, 8 patients (30%) had obstipation and 8 patients (30%) reported symptoms of decreased sweating. Eight male patients (57%) complained of impotency. The presence of bladder dysfunction correlated significantly with the diminished eSSR amplitudes in the right (p < 0.01) and left (p < 0.001) foot, and with the diminished aSSR amplitudes in the left (p < 0.01) foot.

Fig. 1. Regression lines of the latency of the right foot to electrical SSR stimuli against age using multiple regression. White squares represent individual values for controls, black squares for patients. The most pronounced difference between the patients and controls occurs at advanced age.

43 Table 7. Mean amplitudes and latencies of the SSR responses to auditory stimuli in the MS patients and controls.

Amplitude (mV) Latency (s) MS patients Right hand 1.02 (1.08) 1.49 (0.17) Left hand 1.00 (1.02) 1.45 (0.15) Right foot 0.69 (0.85)** 2.06 (0.25)* Left foot 0.83 (0.98) 2.13 (0.31)* Controls Right hand 1.85 (1.39) 1.44 (0.22) Left hand 2.25 (1.65) 1.41 (0.20) Right foot 1.67 (0.67) 1.96 (0.28) Left foot 1.68 (0.64) 1.97 (0.25) Values are mean (SD). The amplitudes and latencies of the MS patients and controls were compared by using covariance analysis with age, height and skin temperatures as covariates: *p < 0.05, **p < 0.01 different from the controls.

Table 8. Mean amplitudes and latencies of the SSR responses to electrical stimuli in the MS patients and controls.

Amplitude (mV) Latency (s) MS patients Right hand 1.01 (1.10)* 1.51 (0.25)** Left hand 0.87 (0.83)** 1.53 (0.35)** Right foot 0.73 (0.84)** 2.23 (0.46)** Left foot 0.73 (0.86)** 2.27 (0.41)** Controls Right hand 2.42 (1.32) 1.36 (0.15) Left hand 2.63 (1.56) 1.38 (0.18) Right foot 1.87 (1.03) 1.95 (0.22) Left foot 1.95 (0.22) 1.96 (0.26) Values are mean (SD). The amplitudes and latencies of the MS patients and controls were compared by using covariance analysis with age, height and skin temperatures as covariates: *p < 0.05, **p < 0.01 different from the controls.

5.3 Thermoregulatory sweating in MS patients

The mean (SD) Ttymp of the MS patients was 37.0 °C (0.3) at baseline and 37.1 °C

(0.4) after 15 minutes of heating. The mean (SD) Ttymp of the controls was 36.9 °C (0.2) at baseline and 37.1 °C (0.4) after 15 minutes of induced heating. No statistically significant differences in sweating were observed between the MS

44 patients and the controls at the baseline and after 5 minutes of heating. However, sweating increased abruptly within the subsequent minutes, being significantly lower at 10 minutes in the right forehead (p = 0.034), and in the right (p = 0.043) and left (p = 0.029) leg, and in the right (p = 0.033) and left (p = 0.037) feet in the MS patients than in the controls (Table 9). After 15 minutes of heating all the measured sweating responses at all the sites were lower in the MS patients than in the controls, but the differences were statistically significant in the feet only (right, p = 0.043; left, p = 0.029) (Figure 2). Sweating tended to be greater in the men than in the women, both in the MS group and the control group. Baseline sweating was greater on the forehead (right side p = 0.001; left side p = 0.006) of the male MS patients than on that of the female MS patients. After 15 minutes of heating, sweating at nearly all sites, especially in the upper body, was significantly greater in the male MS patients than in the female MS patients (right forehead p = 0.029; left forehead p = 0.038; right arm p = 0.007; left arm p = 0.009; right hand p = 0.027; left hand p = 0.011; right leg p = 0.026). This gender difference was also found in the controls. The EDSS score correlated inversely with sweating after 15 minutes of heating in the left hand (p < 0.05), and in the left (p < 0.05) and right foot (p < 0.05). Heating induced new neurological signs in 10 MS patients (34%), including dizziness, paresthesias and motor weakness in the extremities. All the new symptoms resolved themselves within 20 minutes after cessation of the heating stimulus. Eleven patients (38%) had symptoms of orthostatism, 21 patients (72%) had symptoms of bladder dysfunction, 6 (21%) patients reported symptoms of decreased sweating, and 6 of 13 male patients (46%) complained of impotency. Of the different autonomic symptoms studied the presence of urinary dysfunction was associated with decreased sweating in the right arm (p < 0.05) and in the left leg (p < 0.05). In this study twenty-one MS patients had a relapsing–remitting pattern of the disease, and 8 patients had a secondary progressive pattern. The mean duration of the disease with a relapsing–remitting pattern of the disease was 8.7 (5.9) years, and with a secondary progressive pattern 17.3 (4.9) years. The EDSS score ranged between 0–6 (mean 3.2, SD 1.6) in the patients with the relapsing– remitting disease and between 6–9 (mean 7.1, SD 1.1) in the patients with the secondary progressive disease. After 15 minutes heat exposure the mean (SD) TEWL values of the MS patients with a secondary progressive pattern of the disease were low especially in the lower extremities [right leg 4.5 (3.8); left leg 3.7 (2.5); right foot 4.3 (3.3); left foot 3.8 (2.7)]. The mean (SD) TEWL values of

45 patients with a relapsing–remitting form of the disease after 15 minutes of heat exposure were high [right leg 12.7 (14.4); left leg 13.6 (15.6); right foot 15.7 (17.4); left foot 14.3 (15.1)]. There were no statistical differences in the TEWL values, probably due to small number of patients studied in these subgroups (Figure 3). Seventeen patients also participated in our study assessing the SSR, representing a potential generated in skin sweat glands. Five of these 17 patients (29%) showed no SSRs in the lower extremities. The mean TEWL values were lower in these patients with absent SSR responses than in the patients with preserved, suggesting that both of these responses (TEWL and SSR) at least partly use the same sudomotor pathways. The mean (SD) TEWL values in the patients with absent SSRs were as follows: right forehead 11.4 (4.9); left forehead 12.5 (6.4); right arm 6.0 (3.3); left arm 8.8 (4.0); right hand 12.9 (10.5); left hand 12.7 (7.4); right leg 6.8 (3.5); left leg 5.7 (2.9); right foot 6.5 (3.3); left foot 6.5 (2.4). The mean (SD) TEWL values in patients with preserved SSRs were as follows: right forehead 30.9 (26.7); left forehead 33.3 (27.8); right arm11.7 (11.1); left arm 11.5 (9.6); right hand 18.6 (10.5); left hand 19.9 (14.2); right leg 12.4 (14.2); left leg 11.4 (10.1); right foot 14.0 (14.8); left foot 12.7 (12.2).

Table 9. Effects of heating on sweating in the MS patients and controls. TEWL values (g/m²/h) at the 10 registration sites before heating (baseline) and 5, 10 and 15 minutes after the heating stimulus.

Anatomic region TEWL measurements Baseline 5 min 10 min 15 min MS patients Forehead (R) 8.6 (3.1) 12.2 (11.3) 17.4 (19.0)* 21.3 (22.5) Forehead (L) 9.2 (3.4) 12.5 (10.7) 15.9 (15.2) 21.4 (21.9) Arm (R) 3.5 (1.8) 7.0 (5.2) 8.0 (8.3) 8.7 (8.5) Arm (L) 4.0 (2.0) 7.2 (4.5) 7.7 (9.3) 8.8 (7.4) Hand (R) 7.4 (4.2) 12.0 (10.6) 15.2 (15.6) 16.7 (14.1) Hand (L) 7.7 (4.3) 12.0 (10.6) 14.5 (15.2) 16.8 (13.5) Leg (R) 4.4 (2.7) 8.2 (9.1) 9.1 (10.9)* 10.4 (12.9) Leg (L) 4.9 (2.9) 9.2 (10.6) 9.5 (11.4)* 10.8 (13.9) Foot (R) 5.5 (4.5) 11.1 (14.5) 11.2 (15.7)* 12.7 (13.7)* Foot (L) 5.0 (4.5) 9.8 (13.4) 10.4 (19.7)* 11.3 (13.7)*

46 Anatomic region TEWL measurements Baseline 5 min 10 min 15 min Controls Forehead (R) 7.8 (1.8) 14.9 (13.1) 27.4 (23.9) 27.1 (23.5) Forehead (L) 8.0 (2.2) 16.2 (12.6) 28.6 (24.4) 26.2 (21.6) Arm (R) 3.4 (1.7) 7.7 (7.5) 10.8 (12.4) 10.8 (11.8) Arm (L) 4.0 (2.6) 6.7 (6.8) 10.6 (11.8) 10.5 (11.4) Hand (R) 7.3 (3.5) 16.9 (17.9) 10.8 (12.5) 22.4 (18.0) Hand (L) 7.3 (3.6) 16.7 (15.3) 23.9 (23.2) 21.1 (16.9) Leg (R) 4.8 (2.5) 13.2 (12.0) 19.6 (20.0) 20.8 (19.6) Leg (L) 5.2 (3.3) 18.2 (18.4) 20.4 (21.5) 21.6 (22.2) Foot (R) 8.6 (7.9) 20.4 (22.6) 23.5 (25.1) 25.5 (24.2) Foot (L) 8.1 (6.9) 19.0 (4.9) 22.96 (23.2) 24.4 (6.0) Values are means (SD). *p < 0.05 different from the controls.

Fig. 2. TEWL values of the right foot in relation to age in MS patients (solid squares) and healthy controls (open squares) after 15 minutes heating. Regression lines: patients (dashed line); controls (solid line); p < 0.05 (analysis of covariance).

47 Fig. 3. TEWL values in relation to the age of the MS patients with the secondary progressive pattern (solid squares, dashed regression line) and with the relapsing– remitting pattern of the disease (open squares, solid regression line).

5.4 Sudomotor responses in optic neuritis

SSRs could be elicited by both the auditory and electrical stimuli to the hands and feet in all the ON patients and controls. All the mean amplitudes of the auditory stimuli (Table 10) were lower, and all the mean latencies of the auditory stimuli (Table 11) were longer, in the patients with a history of ON, but no statistically significant differences between the ON patients and the controls could be found. Similarly, all the mean amplitudes of the electrical stimuli were lower (Table 10), and all the mean latencies of the electrical stimuli (Table 11) were longer in the patients with a history of ON. The SSR latencies of the electrical stimuli were statistically significantly prolonged in the left hand (p = 0.019) and in the feet (right p = 0.002; left p = 0.013) in the patients with a history of ON (Figure 4). No other statistically significant differences in the SSRs could be found.

The mean (SD) Ttymp of the ON patients was 37.0 °C (0.5) before the heating stimulus and 37.1 °C (0.2) at 15 minutes after induced heating. The mean (SD)

Ttymp of the controls was 36.9 °C (0.2) before the heating stimulus and 37.1 °C (0.4) at 15 minutes after induced heating. No statistically significant differences in sweating were observed between the ON patients and the controls before giving the heating stimulus. After five minutes of induced heating, sweating increased in both groups, but no statistically significant differences could be

48 found between the ON patients and the controls. At 10 and 15 minutes (Table 12) sweating showed a further increase in both groups studied though without a statistically significant difference between the two groups. Dysautonomic symptoms were uncommon. None of the ON patients had symptoms of bladder dysfunction, impotency or orthostatism. Three patients (23%) complained of constipation. One patient (8%) complained of subjective symptoms of decreased sweating. The presence of autonomic symptoms showed no correlation either with the SSR responses or with the sweating parameters as measured by the evaporimeter. Eight ON patients (62%) converted to clinically definite MS during the follow-up, the MS diagnosis being made by using the Poser criteria (Poser et al. 1983). Five patients remained asymptomatic. The mean total brain lesion volume of ON patients with later diagnosis of MS was 3.84 cm³ (SD 3.85, range 0.736– 11.80) and in those who did not develop MS 0.05 cm³ (SD 0.12, range 0.00–0.27). At the beginning of the follow-up the patients with later diagnosis of MS were older [mean (SD) 33.1 (6.7) years] than the patients [mean (SD) 23.0 (2.9) years] without subsequent neurological symptoms. No relationship between the later development of clinically definite MS and the detected SSR parameters could be found.

Table 10. Mean amplitudes (mV) of the SSR responses to the electrical and auditory stimuli in the patients with optic neuritis (ON) and in the healthy controls.

ON patients (mV) Controls (mV) p-value Electrical stimuli Right hand 2.21 (1.68) 2.43 (1.84) 0.570 Left hand 1.94 (1.08) 2.74 (1.87) 0.178 Right foot 1.35 (1.38) 1.80 (0.91) 0.796 Left foot 1.27 (1.65) 1.93 (0.97) 0.995 Auditory stimuli Right hand 1.40 (0.99) 1.74 (1.94) 0.193 Left hand 1.53 (1.05) 2.10 (1.82) 0.270 Right foot 1.24 (1.27) 1.68 (0.73) 0.320 Left foot 1.19 (1.38) 1.77 (0.90) 0.728 Values are mean (SD). The amplitudes of the ON patients and controls were compared by using covariance analysis with age, height and skin temperatures as covariates.

49 Table 11. Mean latencies (s) of the SSR responses to the electrical and auditory stimuli in the patients with optic neuritis (ON) and in the healthy controls.

ON patients (s) Controls (s) p-value Electrical stimuli Right hand 1.49 (0.21) 1.32 (0.14) 0.078 Left hand 1.51 (0.17) 1.30 (0.15) 0.019* Right foot 2.22 (0.27) 1.86 (0.25) 0.002** Left foot 2.27 (0.28) 1.90 (0.28) 0.013* Auditory stimuli Right hand 1.44 (0.23) 1.42 (0.17) 0.843 Left hand 1.44 (0.26) 1.41 (0.17) 0.097 Right foot 2.26 (0.34) 2.03 (0.29) 0.056 Left foot 2.41 (0.51) 2.03 (0.25) 0.118 Values are mean (SD). The latencies of the ON patients and controls were compared by using covariance analysis with age, height and skin temperatures as covariates: *p < 0.05, **p < 0.01 different from the controls.

Table 12. Transepidermal water loss (TEWL) values (g/m²/h) at ten registration sites at baseline and 15 minutes after heating in the patients with optic neuritis (ON) and in the healthy controls.

Anatomic region ON patients Controls p-value Baseline Forehead (R) 9.8 (9.5) 7.9 (1.9) 0.705 Forehead (L) 11.0 (9.5) 8.2 (2.2) 0.486 Arm (R) 4.3 (2.6) 3.2 (1.4) 0.336 Arm (L) 4.3 (2.1) 3.5 (1.6) 0.495 Hand (R) 11.1 (9.9) 6.9 (3.4) 0.291 Hand (L) 11.3 (8.3) 6.9 (3.4) 0.210 Leg (R) 7.5 (5.8) 5.0 (2.6) 0.396 Leg (L) 8.1 (7.6) 5.4 (3.4) 0.558 Foot (R) 10.8 (12.8) 8.0 (7.8) 0.890 Foot (L) 9.8 (9.7) 7.7 (6.9) 0.953 15 minutes Forehead (R) 30.1 (27.3) 27.1 (24.4) 0.991 Forehead (L) 29. 8 (24.1) 26.8 (22.3) 0.869 Arm (R) 13. 2 (13.6) 10.7 (12.2) 0.810 Arm (L) 11.3 (12.1) 10.5 (11.8) 0.995 Hand (R) 20.5 (17.3) 22.3 (18.7) 0.773 Hand (L) 20.5 (18.0) 21.3 (17.5) 0.768 Leg (R) 20.8 (25.0) 21.3 (20.2) 0.742 Leg (L) 20.9 (26.0) 22.4 (23.0) 0.637 Foot (R) 19.8 (19.0) 23.8 (24.1) 0.588 Foot (L) 20.0 (20.5) 23.8 (24.1) 0.540 Values are means (SD).

50 Fig. 4. SSR latencies of the right foot to electrical stimuli in relation to age in ON patients (solid squares) and healthy controls (open squares). Regression lines: Patients (dashed line); controls solid line; p < 0.01.

5.5 Magnetic resonance imaging

5.5.1 MRI and cardiovascular autonomic reflexes in MS patients

All the MS patients underwent brain MRI and adequate brain MRI data were available for 48 of them. All these 48 patients showed white matter abnormalities typical of MS. The total intracranial brain MS lesion volumes [mean (SD) 16.39 (17.98) cm³, range 0.10–83.42 cm³] showed a significant association with the duration of the disease (p < 0.001) and with the severity of the MS as expressed by the EDSS score (p < 0.001). The total intracranial MS lesion volumes also showed a correlation with the decreased diastolic BP in the tilt table test at two minutes (p < 0.05). In addition, the total midbrain lesion volumes [mean (SD) 0.25 (0.40) cm³, range 0–1.81 cm³] correlated with the decreased BP responses immediately (diastolic, p < 0.05), at two minutes (diastolic, p < 0.05), and at seven minutes (diastolic, p < 0.05 ) after tilting (Figure 5). Furthermore, the total parietal MS lesion volumes [mean (SD) 3.66 (4.85) cm³, range 0–24.92 cm³] were associated with the decreased BP responses at two minutes (diastolic, p < 0.05)

51 after tilting. There was no statistically significant correlation with the MRI lesion load and the R–R interval parameters. The symptoms of bladder dysfunction did not correlate significantly with the cardiovascular reflex test results, although there was an increase in the total MRI lesion loads (p < 0.03) in this subgroup.

-10

-20 Diastolic BP response [mmHg] Diastolic -30 0 0.5 1.0 1.5 Midbrain MS lesion volume [cm3 ] Fig. 5. Scatter diagram showing both diastolic BP responses in the tilt table test at seven minutes, and midbrain MS lesion volumes, with least squares line and 95% confidence limits for the population mean (dashed lines) and for an individual (dotted lines). The correlation coefficient r = -0.34 with p < 0.05.

5.5.2 MRI and sympathetic skin responses in MS patients

All the MS patients underwent brain MRI and adequate brain MRI data were available for all of them. All the cases exhibited white matter abnormalities typical of MS. The total lesion volumes in the whole brain ranged from 0.10 to 83.42 cm³ (mean, SD; 19.02, 20.18) and showed a significant correlation with the severity of the MS as expressed by the EDSS score (p < 0.001). The total lesion volumes also correlated with the decreased eSSR amplitudes in the feet (p < 0.01). The patients with absent SSRs in the feet showed more MS lesions (mean, SD; 41.94 cm³, 20.86 cm³) than those with preserved SSRs (mean, SD; 9.37 cm³, 9.35 cm³). The lesion volumes in the right pons correlated significantly with the increased aSSR latencies in the left hand (p < 0.01). Similarly, the lesion volumes in the left pons correlated significantly with the increased aSSR latencies in both

52 the right hand (p < 0.01) and in the left hand (p < 0.001). The lesion volumes in the right temporal lobe correlated significantly with the decreased aSSR amplitudes in the left hand (p < 0.01) and in the right (p < 0.01) and left (p < 0.01) foot. Moreover, the lesion volumes in the left cerebellum showed an association with the prolonged aSSR latency in the left hand (p < 0.01). The lesion volumes in the right pons correlated significantly with the prolonged eSSR latencies in both the right foot (p < 0.01) and the left foot (p < 0.01). The lesion volumes in the left pons correlated significantly with the prolonged eSSR latencies in both the right foot (p < 0.01) and the left foot (p < 0.01). The lesion volumes in the right temporal lobe showed a significant correlation with the decreased eSSR amplitudes in the left hand (p < 0.01) and in both the right (p < 0.01) and the left (p < 0.01) foot. In 25 of the MS patients MS lesions were also seen in distinct cervical spinal cord segments [mean (SD) 3.9 (2.14), range 0–7]. However, these cervical spinal cord lesions were not significantly associated with the SSR findings. Additionally, in 14 patients, MRI revealed MS lesions in the distinct thoracic spinal cord segments [mean (SD) 1.44 (1.95), range 0–8]. Contrary to the findings with the cervical spinal cord, a significant correlation was found between these thoracic spinal cord lesions and the attenuated eSSRs in the left foot (p < 0.01).

5.5.3 MRI and thermoregulatory sweating in MS patients

All the MS patients underwent brain MRI and adequate brain MRI data were available for all of them. The brain MRI proved to be abnormal in all cases, showing the white matter abnormalities typically seen in MS. The total lesion volumes in the whole brain ranged from 0.27 to 83.42 cm3 (mean, SD; 18.43, 19.71) and showed a significant correlation with the severity of the MS as expressed by the EDSS score (p < 0.001). After 15 minutes of heating the total lesion volumes in the brain correlated with decreased sweating both in the left foot (p < 0.05) and in the right hand (p < 0.05). In 27 of the MS patients (93%) MS lesions were seen in distinct cervical spinal cord segments [mean (SD) 4.3 (2.3), range 0–7], and in 15 of the MS patients (52%) MS lesions were also seen in distinct thoracic spinal cord segments [mean (SD) 1.7 (2.4), range 0–9]. However, there was no significant correlation between the spinal cord lesions and the TEWL values.

53 5.5.4 MRI and sudomotor responses in optic neuritis

The brain MRI scans were abnormal in 9 ON patients (69%), showing white matter abnormalities consistent with MS. All these patients showed MS lesions in the parietal lobes. Eight patients (62%) showed MS-like lesions in the frontal lobes, 8 patients (62%) in the occipital lobes, 6 patients (46%) in the temporal lobes, 2 patients (15%) in the midbrain and 1 patient (8%) in the pons. No lesions could be detected in the medulla or cerebellum. The mean total volume of lesioned tissue was 2.41 cm³ (SD 3.50). The mean volumes of lesioned tissue were in the frontal lobes 1.70 cm³ (SD 1.72, range 0.12–4.58 cm³ ), in the parietal lobes 0.80 cm³ (SD 0.73, range 0.17–2.07 cm³), in the occipital lobes 0.49 cm³ (SD 0.37, range 0.10–1.26 cm³), in the temporal lobes 0.99 cm³ (SD 1.47, range 0.12–3.93 cm³), in the midbrain 0.20 cm³ (SD 0.12, range 0.12–0.29 cm³) and in the pons 0.24 cm³. No significant correlations between the total brain lesion volumes and the sudomotor values were found, neither with the TEWL values nor with the SSR parameters. Neurological impairment in the ON patients was mild, and the EDSS score ranged from 0–1.5 (mean 0.62, SD 0.62). Three ON patients without identified MS lesions on their brain MRI scans showed mild neurological impairment (all EDSS 1). One ON patient showed neither MS lesions nor clinical disability (EDSS 0). The mean total lesion volume in patients with neurological disability (EDSS ranging from 1 to 1.5) was 5.92 cm³ (SD 4.74) while the mean total lesion volume in patients without neurological disability (EDSS 0) was 1.53 cm³ (SD 1.16). In 7 of the ON patients (54%) typical lesions of demyelinative disease were seen in distinct cervical spinal cord segments [mean (SD) 1.7 (1.9), range 0–5]. In 8 of the ON patients (62%) demyelinative lesions were also seen in distinct thoracic spinal cord segments [mean (SD) 1.2 (1.3), range 0–4]. However, these spinal cord lesions were significantly associated neither with the TEWL values nor with the SSR parameters.

54 6 Discussion

6.1 General aspects

The detected frequency of autonomic dysfunction in MS patients emphasises the importance of autonomic evaluations in MS. Autonomic evaluations provide objective information about vague symptoms and form an expansion of the neurological examination. The impact of key symptoms such as dizziness, syncope, falls, constipation and incontinence needs to be investigated. The value of autonomic studies is also based on their ability to reveal clinically silent lesions and to objectify the CNS damage. The present study was designed to assess quantitatively the cardiovascular and sudomotor control in MS patients. The sudomotor functions of ON patients at risk of developing MS were also studied. MS-related autonomic dysfunction was highly prelevant and autonomic dysfunction virtually encompassed all the disease stages. Standardized cardiovascular reflex measurements were used in studying the cardiovascular autonomic dysfunction. These methods have been well documented for the evaluation of ANS dysfunction in various diseases affecting the CNS (Korpelainen et al. 1994, Turkka et al. 1997, Haapaniemi et al. 2000a, Myllylä et al. 2002). Sudomotor dysfunction was evaluated by measuring SSRs and by measuring thermoregulatory sweating after heat provocation. Both these methods have also been used previously to estimate sudomotor dysfunction in various CNS diseases (Korpelainen et al. 1993a, Haapaniemi et al. 2000b). Both the cardiovascular and sudomotor methods proved to be useful here with MS patients. SSRs also proved to be practical for quantitating the sudomotor dysfunction in ON patients. The rate of the accumulation of the lesion loads visible on MRI were also found to be a useful marker of the anatomic level of autonomic dysfunction.

6.2 Cardiovascular autonomic dysfunction in MS patients

The present data showed cardiovascular autonomic regulation failure in MS patients, the failure manifesting itself both in the HR responses to deep breathing and in the HR and BP responses in the tilt table test. This agrees with previous MS studies (Senaratne et al. 1984, Nordenbo et al. 1989, Anema et al. 1991, Vita

55 et al. 1993, Drory et al. 1995, Acevedo et al. 2000, Gunal et al. 2002) reporting abnormalities in cardiovascular reflexes reflecting both sympathetic and parasympathetic dysfunction. In the present study the disease severity correlated with the decrease of the cardiovascular responses and also with the MRI brain lesion loads. Midbrain MS lesions seemed to account for most of the cardiovascular abnormalities, but hemispheric MS lesions also seemed to be involved. Some attempts have been made to correlate brain MRI findings with cardiac autonomic dysfunction in MS patients. However, in one study of 10 MS patients with abnormal and 11 MS patients with normal cardiovascular responses no significant differences in the presence and number of brainstem lesions were found (Anema et al. 1991). In another study of 16 MS patients, no correlation was found between the HR spectral parameters and the MRI lesion area or localisation (Frontoni et al. 1996). However, in two larger studies of 40 MS patients (Vita et al. 1993, Acevedo et al. 2000) a significant correlation between the presence of autonomic dysfunction and MRI evidence of brainstem lesions was established. In addition, in one study (Ferini-Strambi et al. 1995) comparing 25 MS patients with 25 controls during wakefulness and sleep, the MS patients showed impaired parasympathetic activity during sleep, but no correlation could be found between the autonomic cardiac data and the MRI lesions. None of these previous studies involved quantitative analyses of the MRI lesion load volumes. Midbrain MS lesions seem to account for most cardiovascular abnormalities in MS patients, but parietal MS lesions also seem to be involved. There is already some evidence to suggest that hemispherical brain activity is involved in the regulation of the cardiovascular system. In one study on BP and brain atrophy in nondemented aged people, frontal and most of all parietal brain atrophy was accompanied with lower systolic and diastolic BP (Skoog et al. 1998). There is also some evidence of cortical asymmetry in the regulation of HR and other cardiovascular functions (Oppenheimer 1993). However, in the present study no differences between the right and left hemisphere were found. This symmetry is most likely explained by MS plaques scattered on the anatomically widespread CNS autonomic regulatory system. The clinical relevance of cardiovascular dysfunction seems to be scarce. In the present study the most significant correlations were found in the tilt table test parameters in which the BP responses are mainly under sympathetic control. There is evidence that aged MS patients are less likely to have diseases such as acute myocardial infarction, heart failure, hypertension, angina pectoris and

56 cerebrovascular disease than age- and sex-matched controls (Fleming & Blake 1994). Because serious cardiovascular disorders are seldom encountered clinically in MS the possibility of sympathetic hypofunction providing protection for cardiac involvement can be hypothesized.

6.3 Impaired sympathetic skin responses in MS patients

The present results suggest that MS patients have impairment in the functions of the central sudomotor autonomic pathways, and that their SSRs are often abnormal, including absent, delayed or diminished responses especially in the feet. Interestingly, in the present study with two different stimulation modalities, the lack of responses in the majority of patients to both the auditory and electrical stimuli was almost identical, suggesting that both these SSR responses use mainly the same autonomic pathways. In the current study a significant correlation between the abnormal SSRs and the severity of the disability caused by MS was also found, which is compatible with previous reports (Gutrecht et al. 1993, Caminero et al. 1995, Drory et al. 1995). However, previously, in one study (Nazliel et al. 2002), no correlation between foot latencies and the EDSS score could be established, although foot latencies were prolonged compared to those of the controls. This lack of a correlation can be explained by the inclusion of only MS patients still able to walk, contrary to other studies. In another study (McDougall & McLeod 2003) the presence of SSR abnormalities in the upper but not in the lower limbs was associated with a significant increase in the EDSS score. One earlier attempt has been made to correlate the hypothalamus and brain stem MRI findings with SSR parameters in MS patients (Gutrecht et al. 1993), but no correlations were noted in the 16 patients studied. However, the present study mapped the whole brain in different anatomic regions and found that specific brain regions are related to the presence of SSR abnormalities in MS patients. The CNS pathway to the sweat glands is thought to begin in the posterior hypothalamus, travelling in the ventrolateral brain stem reticular formation down to the cervical spinal cord (Sato & Schmidt 1973). According to animal studies several brain regions are involved in SSR processing, including the orbitofrontal cortex, the caudate nucleus, the anterior lobe of the cerebellum, the dorsal thalamus, the posterior hypothalamic nuclei, the ventrolateral and ventromedial substantia reticularis and the intermediolateral nucleus (Wilcott 1969, Schondorf 1993). In the current study multiple brain areas were also associated with

57 abnormal SSRs. The lesion volume in the brain stem (pons region) seems to correlate with bilaterally abnormal SSRs, closely similar to SSR reflex abnormalities found in patients with brain stem infarction (Korpelainen et al. 1993b). In the present study the lesion volume in the temporal lobe also correlated with both ipsilateral and contralateral attenuated SSRs, suggesting that SSRs also receive input from the middle cerebral artery territory. This is consistent with studies in stroke patients (Korpelainen et al. 1993b, Schwalen et al. 1996) with hemispheric lesions in the middle cerebral artery territory and bilateral abnormalities in their SSR reflexes. Although it is difficult to draw safe conclusions about the causal relationship between focal lesion volume and SSRs, it is interesting to see a relation between lesion volumes in the right pons and the right temporal lobe and the SSRs of the contralateral hand. This agrees with the concept that some of the descending sudomotor pathways conducting responses to arousal stimuli cross over (in contrast to the thermoregulatory descending pathways). Furthermore, also cerebellum was found to modulate SSRs. There is some earlier evidence to suggest that the cerebellum may influence the SSR responses in humans, and that SSRs are abnormal in cerebellar degeneration (Yokota et al. 1993, Shindo et al. 1999). The current study supports the view that structural brain damage correlates with specific autonomic dysfunction in MS patients. The spinal cord is a common site of involvement in MS, but in the present study no association could be found between the MS lesions in the cervical part of the spinal cord and the sudomotor autonomic failure. On the other hand, there was a correlation between delayed feet latencies and thoracic spinal cord lesions. Since the sympathetic nervous system exits mainly from the thoracolumbal regions of the spinal cord, these findings suggest that thoracic spinal cord MS lesions may result in a more extensive injury of the sympathetic sudomotor pathways than cervical ones. Abnormal SSR values were more common when the stimulus was an electrical impulse to the median nerve than auditory one, which suggests that impaired afferent function have an impact on the results. Using the absence of SSR responses in at least one limb as the basis for determining abnormality, abnormal eSSRs were found in 26% of MS patients and abnormal aSSRs in 30%. All the patients with absent feet responses showed EDSS scores of 5 or more, indicating disability severe enough to preclude full daily activities. When pathological amplitude and latency values (+2SD for the SSR latencies and -2SD

58 for the amplitudes) were added to the basis for determining abnormality, abnormal SSRs were found in 52% of the MS patients.

6.4 Thermoregulatory sweating dysfunction in MS patients

Thermoregulatory functions in MS patients have scarcely been studied. However, contrasting with previous studies, the quantitative measurement of sweating in the MS patients in the present study was performed in different body regions, revealing significantly low levels of thermal sweating, and thus indicating a sympathetic ANS failure. The sweating impairment correlated with the severity of the MS. Previous studies, where the intensity and distribution of the change in colour of quinizarin powder applied to the body have been observed, have given only rough estimates of sweating. Using this quinizarin method Noronha (Noronha et al. 1968) found abnormal thermoregulatory sweating responses to heat and to drugs in 25 of 60 examined MS patients. The disturbances varied from total lack of sweating to absent sweating in the lower limbs, and the incidence of abnormal sweating responses was increased with advancing disease. Cartlidge (Cartlidge 1972) provoked sweating in 50 MS patients placing their hands in water as hot as they could stand. He also used quinizarin powder and found impaired sweating in 20 MS patients, 3 patients with no sweating below the nipples, 4 with no sweating below the waist and 13 with absent sweating in the legs. In the current study the thermoregulatory sweating was also similarly most often reduced in the lower extremities, but contrasting with the quinizarin powder studies, impaired but not complete absence of thermoregulatory sweating was found. The differences in sweating were significant after 10 minutes of heating in different parts of the body (forehead and lower extremities) and after 15 minutes of heating in the feet only. However, a type 2 statistical error should be considered, because nearly all the mean TEWL values even at baseline and after 5, 10 and 15 minutes of heating were lower in the MS patients than in the controls. It is possible that the thermoregulatory sweating is in fact more extensively affected, but that the differences could not be observed because of the number of patients studied was too small. In the current study decreased sweating correlated both with increased disability and increased total MRI lesion volume in MS patients. It is known that skin blood flow increases substantially in response to thermal stress, and that vasodilation and increased skin blood flow are essential for heat dissipation during heat exposure. It has been shown (Andersen & Nordenbo

59 1997), using a 133-Xenon washout technique, that no signs of sympathetic vascular dysfunction can be found in skeletal muscle or subcutaneous tissue in MS patients despite their severely disturbed sympathetic thermoregulatory sweating, the authors suggesting that the thermoregulatory parts of the sympathetic nervous system functions are more susceptible to demyelination in MS than the vasomotor parts. Reduced sweating can to some extent be due to low capacity in the physical performance of MS patients. It is known that avoiding physical activity can decrease the reliance on sweating as a heat dissipation mechanism, leading to reduction in sweat gland function (Nadel et al. 1974). On the other hand, one study has shown that 15 weeks of aerobic training does not increase stimulated sweating responses in MS patients (Davis et al. 2005). In the current study a gender difference was found, both healthy males and males with MS sweating more than their respective female counterparts. This gender difference is well known in healthy populations (Bittel & Henane 1975), women sweating less profusely than men. Heat induces neurological deterioration in MS patients and the raising of body temperature may lead to the temporary worsening of MS symptoms. Hyperthermia induces a heat-linked neuro-blockade of partially demyelinated axons (Guthrie & Nelson 1995) and this may be linked with the nerve conduction block affecting MS patients with small increases in core body temperature (Namerow 1971). Over 80% of MS patients develop neurological signs during hyperthermia (Guthrie & Nelson 1995). However, in the current study only 34% of the MS patients experienced a worsening of their MS symptoms while heated.

This can be explained by the fact that the Ttymp rose only moderately. However, since some reports claim that these heat-induced symptoms can be persistent (Berger & Sheremata 1983), only moderate heating was used. Sweating failure can be clinically relevant, and MS patients appear to be at increased risk of heat illness during exposure to elevated ambient temperatures (Kohlmeier et al. 2000, Harbison et al. 1989). Recently, it has been shown that cooling via one hand improves physical performance in heat-sensitive individuals with MS (Grahn et al. 2008). It can therefore be hypothesized that worsening symptoms of MS and fatigue can both provide protection for serious hyperthermia in hot environments and during physical exercise.

60 6.5 Sudomotor dysfunction in optic neuritis

The sudomotor functions of ON patients were measured in the present study, and increased latencies in SSRs were found, indicating sudomotor failure. Earlier, by using conventional evoked potentials, ON patients have been shown to have silent CNS lesions in the somatosensory (Ghezzi et al. 1996, Simó et al. 2008), motor (Ghezzi et al. 1996, Simó et al. 2008), visual (Ghezzi et al. 1996), and auditory pathways (Ghezzi et al. 1996). The present study shows that the central autonomic pathways may also be lesioned in ON patients. The strengths of this study are the multiparametric evaluation of the sudomotor pathways using quantitative evaporimetry and SSR measurements, and the quantitative measurement of structural changes by MRI scans. However, the weak points are the small number of ON patients studied and the great physiological variation in the used ANS measures, both of which reduce the detection level of mild changes in the sudomotor pathways. In the present study abnormal SSR responses were found only when the stimulus was an electrical impulse to the median nerve, which suggests that an impaired afferent function could have some impact on the results. However, by using electrical stimulation the SSR latency prolongation was up to 210 ms longer in the upper extremities, and up to 370 ms longer in the lower extremities, than in the controls. These latencies are far above the whole afferent somatosensory response latencies of 20 ms from hand to cortex and 40 ms from leg to cortex in healthy individuals. Morover, the SSR latency is the same whether stimulating at the hand or the foot (Tzeng et al. 1993). The latencies of the SSRs to auditory stimuli as measured in the lower extremities was up to 380 ms longer in the ON patients than in the controls, though this did not reach a significant level. These results support the idea that SSR latency prolongation is mainly due to a disturbed central integration and efferent sudomotor pathway function. Eight ON patients (62%) converted to clinically definite MS during the follow-up. This percentage could have been even higher if the ON patients had been studied clinically. It would seem that sudomotor dysfunction evolves early in the clinical course of MS and can be detected before the actual MS diagnosis is made. On the other hand, post-hoc analysis of the same data suggests that SSRs have no value in identifying those patients who will later develop MS. In several autonomic studies only MS patients in a stable phase of the disease have been investigated. However, the present study also included patients still recovering from acute ON and this may have had some impact on the results. All the patients

61 had suffered from a clinically isolated pure ON, but a large number of them showed extensive MS lesions in different brain regions outside the optic nerves. The activity of MS is usually greatest during relapses, and the exacerbation of the disease can also increase autonomic nervous dysfunction, as seen in increased bladder dysfunction during relapses of MS. It is possible that the other parts of the autonomic nervous system are also more vulnerable during relapses, although clinical signs of sudomotor dysfunction probably go unnoticed.

62 7 Conclusions

The findings of the present study indicate that both MS and ON injure the ANS. The main conclusions are: 1. MS results in both reduced HR variation and decreased BP reactions, indicating disturbed cardiovascular regulation. In particular, the midbrain lesions, but also to a lesser extent the hemispherical lesions, are associated with cardiovascular dysfunction. 2. MS is associated with sudomotor regulation failure. The lack of SSRs indicates severe MS. Though MS is a global disorder of white matter, even focal MS lesions evoke SSR abnormalities. 3. MS patients display impairment in their thermoregulatory sweating, and the abnormalities in their sweating correlate with the severity of the disease. 4. ON is a frequent initial manifestation of MS. ON patients show clinically silent disturbances in their sudomotor autonomic pathways. Sudomotor autonomic dysfunction virtually encompasses all the disease stages of MS.

64 References

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76 Original publications

Original publications are not included in the electronic version of the dissertation.

78 ACTA UNIVERSITATIS OULUENSIS SERIES D MEDICA

1045. Pääkkönen, Tiina (2010) Melatonin and thyroid hormones in the cold and in darkness. Association with mood and cognition 1046. Nevala, Terhi (2010) Endovascular treatment of an abdominal aortic aneurysm. Mid-term results and management of a type II endoleak 1047. Railo, Antti (2010) Wnt-11 signalling, its role in cardiogenesis and identification of Wnt/β-catenin pathway target genes 1048. Ahvenjärvi, Lauri (2010) Computed tomography in diagnostics and treatment decisions concerning multiple trauma and critically ill patients 1049. Haapea, Marianne (2010) Non-response and information bias in population-based psychiatric research. The Northern Finland 1966 Birth Cohort study 1050. Poikonen, Kari (2010) Susceptibility of human macrophages to Chlamydia pneumoniae infection in vitro 1051. Ojala, Kati (2010) Modern methods in the prevention and management of complications in labor 1052. Auvinen, Juha (2010) Neck, shoulder, and low back pain in adolescence 1053. Pirkola, Jatta (2010) Gestational diabetes. Long-term, metabolic consequences for the mother and child 1054. Santaniemi, Merja (2010) Genetic and epidemiological studies on the role of adiponectin and PTP1B in the metabolic syndrome 1055. Hyvärinen, Jaana (2010) Enzymes involved in hypoxia response. Characterization of the in vivo role of HIF-P4H-2 in mouse heart, of a novel P4H in human and zebrafish and of the catalytic properties of FIH 1056. Kastarinen, Helena (2010) Renal function and markers of cardiovascular risk 1057. Nevalainen, Jukka (2010) Utilisation of the structure of the retinal nerve fiber layer and test strategy in visual field examination 1058. Liukkonen, Esa (2010) Radiologisten kuvien katselussa käytettävien näyttöjen laatu. Näyttöjen laitekanta, suorituskyky ja laadunvalvonta sekä kuvankatselu- olosuhteet radiologisissa yksiköissä ja terveyskeskuksissa 1059. Ollila, Päivi (2010) Assessment of caries risk in toddlers. A longitudinal cohort study 1060. Vähäkangas, Pia (2010) Kuntoutumista edistävä hoitajan toiminta ja sen johtaminen pitkäaikaisessa laitoshoidossa

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