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Valsalva Maneuver The Valsalva maneuver is a simple test of autonomically-mediated car- diovascular reflexes, comprising forced expiration against resistance (“straining”), followed by release of the resistance and completion of expiration. The first phase produces impaired cardiac filling due to impaired venous return as a consequence of elevated intrathoracic pressure, with a fall in cardiac output and blood pressure, inducing peripheral vasoconstriction (sympathetic pathways) to maintain blood pressure. The second phase causes a transient overshoot in blood pres- sure as the restored cardiac output is ejected into a constricted circu- lation, followed by reflex slowing of heart rate. In autonomic (sympathetic) dysfunction, reflex vasoconstriction, blood pressure overshoot and bradycardia do not occur. The latter may be conveniently assessed by measuring R-R intervals in a prolonged ECG recording, an R-R interval ratio between the straining and release phases of less than 1.1 suggesting impaired response. Cross References Orthostatic hypotension

Vegetative States The vegetative state is a clinical syndrome in which cognitive function is lost, due to neocortical damage (hence no , response, speech), while vegetative (autonomic, respiratory) function is pre- served due to intact brainstem centres. Primitive postural and reflex limb movements may also be observed. The syndrome, also known as neocortical death, coma vigil, and the apallic syndrome, may be seen after extensive ischemic-hypoxic brain injury, for example following resuscitation after cardiac arrest, and needs to be distinguished from coma, akinetic mutism, and the locked-in syndrome. Persistent vegeta- tive state (PVS) is defined by persistence of this state for > 12 months (UK) or > 6 months (USA) after brain trauma, or > 6 months (UK) or > 3 months (USA) following brain anoxia. The prognosis of PVS is poor, but occasional reports of very late recovery have appeared. References Jennett B. The vegetative state. Medical facts, ethical and legal dilem- mas. Cambridge: CUP, 2002 Wade DT, Johnston C. The permanent vegetative state: practical guidelines on diagnosis and management. British Medical Journal 1999; 319: 841-844 Zeman A. The persistent vegetative state: conscious of nothing? Practical Neurology 2002; 2: 214-217 Cross References Akinetic mutism; Coma; Locked-in syndrome - 316 - V.qxd 9/28/05 10:49 PM Page 317

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Venous Pulsation - see RETINAL VENOUS PULSATION

Vernet’s Syndrome - see JUGULAR FORAMEN SYNDROME

Vertigo Vertigo is an illusion of movement, a of rotation or of tilt, caus- ing a of imbalance or dysequilibrium. It is a subtype of “dizzi- ness’, to be distinguished from the light-headedness of general medical conditions (vasovagal attacks, presyncope, cardiac dysrhythmias). Vertigo is often triggered by head movement and there may be associ- ated autonomic features (sweating, pallor, , vomiting). Vertigo may be horizontal, vertical or rotatory. Pathophysiologically, vertigo reflects an asymmetry of signaling anywhere in the central or peripheral vestibular pathways. Clinically it may be possible to draw a distinction between central and peripheral lesions: in the latter there may be concurrent loss and (reflecting vestibulocochlear (VIII) nerve involvement). Facial weak- ness (VII) and ipsilateral ataxia suggest a cerebellopontine angle lesion; , bulbar dysfunction and long tract signs are suggestive of a central pathology. Peripheral vertigo tends to compensate rapidly and completely with disappearance of nystagmus after a few days, whereas central lesions compensate slowly and nystagmus persists. The clinical pattern of vertigo may gives clues as to underlying diagnosis:

Vertigo Peripheral Central Acute Prolonged, Otomastoiditis Brainstem/ spontaneous Vestibular neur(on)itis cerebellum Labyrinthine concussion hemorrhage/ Isolated labyrinthine infarct infarct/ Vestibular nerve section demyelination Drug-induced Recurrent, Ménière’s disease Vertebrobasilar episodic (endolymphatic hydrops) ischemia (with Autoimmune inner associated disease (isolated, systemic) features) Perilymph fistula Migraine (rare) Epilepsy (rare) Positional Benign paroxysmal 4th ventricle positional vertigo (BPPV) lesions: multiple sclerosis Chiari malformation (contd.) - 317 - V.qxd 9/28/05 10:49 PM Page 318

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(contd.)

Vertigo Peripheral Central Brainstem/ cerebellar tumors Spinocerebellar atrophy Chronic Vestibular Neurological decompensation/failure disorder Psychogenic

All patients with vertigo should have a Hallpike maneuver performed during the examination. Specific treatments are available for certain of these conditions. A brief course of a vestibular sedative (cinnarizine, Serc) is appropri- ate in the acute phase, but exercises to “rehabilitate” the semicircular canals should be begun as soon as possible in peripheral causes. In BPPV, most patients respond to the Epley maneuver to reposition the otoconia which are thought to cause the condition (canalolithiasis). Brandt-Daroff exercises are an alternative. Cawthorne-Cooksey exer- cises are helpful in vestibular decompensation or failure. References Baloh RW. Vertigo. Lancet 1998; 352: 1841-1846 Brandt T. Vertigo: its multisensory syndromes (2nd edition). London: Springer, 1999 Hain TC, Uddin MK. Approach to the patient with dizziness and ver- tigo. In: Biller J (ed.). Practical neurology (2nd edition). Philadelphia: Lippincott Williams & Wilkins, 2002: 189-205 Luxon LM. Vertigo: new approaches to diagnosis and management. British Journal of Hospital Medicine 1996; 56: 519-520, 537-541 Cross References Ataxia; Caloric testing; Facial paresis; Hallpike maneuver, Hallpike test; Hennebert’s sign; Illusion; Nystagmus; Vestibulo-ocular reflexes

Vestibulo-Ocular Reflexes The vestibulo-ocular reflexes (VOR) are a physiological mechanism which generates eye rotations that compensate for head movements, especially during locomotion, so stabilizing the retinal image on the fovea. VORs depend upon the integrity of the connections between the semicircular canals of the (afferent limb of reflex arc) and oculomotor nuclei in the brainstem (efferent limb). Loss of vestibular function, as in acute bilateral vestibular failure, causes gaze instability due to loss of VORs, causing the symptom of (q.v.) when the head moves. As well as vestibular input, compensatory eye rotations may also be generated in response to visual information (pursuit-optokinetic eye movements) and neck proprioceptive information; anticipatory eye movements may also help stabilize the retinal image. - 318 - V.qxd 9/28/05 10:49 PM Page 319

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VORs are also useful in assessing whether ophthalmoplegia results from a supranuclear or infranuclear disorder, since in the former the restriction of eye movement may be overcome, at least in the early stages, by the intact VOR (e.g., the supranuclear gaze palsy in the vertical plane in progressive supranuclear palsy). VORs are difficult to assess in conscious patients because of con- current pursuit-optokinetic eye movements, and because rotation of the head through large angles in conscious patients leads to interruption of VORs by vestibular nystagmus in the opposite direction (optokinetic nystagmus). The head impulse test (q.v.) may be used to test VORs in conscious patients, for example those with vertigo in whom vestibular failure is suspected. VOR may also be assessed using a slow (0.5-1.0 Hz) doll’s head maneuver while directly observing the eyes (“catch up” sac- cades may be seen in the absence of VOR), measuring visual acuity (dynamic visual acuity, or illegible E test; dropping two to three lines on visual acuity with head movement vs. normal if VOR impaired), and ophthalmoscopy (optic disc moves with head if VOR abnormal). In unconscious patients, slow phase of the VORs may be tested by rotating the head and looking for contraversive conjugate eye move- ments (oculocephalic responses, doll’s head eye movements) or by caloric testing. VORs are lost in brainstem death. Another important element of VOR assessment is suppression or cancellation of VOR by the pursuit system during combined head and eye tracking. VOR suppression may be tested by asking the patient to fixate on their thumbs with arms held outstretched while rotating at the trunk or sitting in a swivel chair. VOR suppression can also be assessed during caloric testing: when the nystagmus ceases with fixation, removal of the fixation point (e.g., with Frenzel’s glasses) will lead to recurrence of nystagmus in normals but not in those with reduced or absent VOR suppression. VOR suppression is impaired (presence of nystagmus even with slow head movements) in cerebellar and brainstem disease. References Bronstein AM. Vestibular reflexes and positional manoeuvres. Journal of Neurology, Neurosurgery and Psychiatry 2003; 74: 289-293 Leigh RJ, Brandt T. A reevaluation of the vestibulo-ocular reflex: new ideas of its purpose, properties, neural substrate, and disorders. Neurology 1993; 43: 1288-1295 Cross References Caloric testing; Coma; Doll’s eye maneuver, Doll’s head maneuver; Hallpike maneuver, Hallpike test; Head impulse test; Ocular tilt reac- tion; Oculocephalic response; Oscillopsia; Supranuclear gaze palsy; Vertigo

Vibration Vibratory sensibility (pallesthesia) represents a temporal modulation of tactile sense. On this ground, some would argue that the elevation of vibration to a “sensory modality” is not justified. Vibratory sensibility is easily tested using a tuning fork (128 Hz). This assesses the integrity of rapidly adapting (Pacinian corpuscles) and their - 319 - V.qxd 9/28/05 10:49 PM Page 320

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peripheral and central connections; the former consist of large afferent fibers, the latter of ascending projections in both the dorsal and lateral columns. The classification of both vibration and as “posterior column signs,” sharing spinal cord and brainstem pathways, is common in neurological parlance (and textbooks) but questioned by some. Instances of dissociation of vibratory sensibility and propriocep- tion are well recognized, for instance the former is usually more impaired with intramedullary myelopathies. Decrease in sensitivity of vibratory (increased percep- tual threshold) is the most prominent age-related finding on sensory examination, thought to reflect distal degeneration of sensory axons. References Calne DB, Pallis CA. Vibratory sense: a critical review. Brain 1966; 89: 723-746 Gilman S. Joint position sense and vibration sense. Journal of Neurology, Neurosurgery and Psychiatry 2002; 73: 473-477 Cross References Age-related signs; Myelopathy; Proprioception; Two-point discrimi- nation

Visual Agnosia Visual agnosia is a disorder of visual object recognition. The term derives from Freud (1891), but it was Lissauer (1890), speaking of see- lenblindheit (psychic blindness), who suggested the categorization into two types which continues to be used: ● Apperceptive visual agnosia: A defect of higher order leading to impaired shape recognition, manifested as difficulty copying shapes or matching shapes, despite preserved primary visual capacities, including visual acuity and fields (adequate to achieve recognition), brightness discrimination, vision and motion perception (indeed motion may facilitate shape perception; see Riddoch’s phenomenon). Reading is per- formed with great difficulty, with a “slavish” tracing of letters which is easily derailed by any irrelevant lines; such patients may appear blind. ● Associative visual agnosia: An impairment of visual object recognition thought not to be due to a perceptual deficit, since copying shapes of unrec- ognized objects is good. The scope of this impairment may vary, some patients being limited to a failure to recognize faces () or visually presented words (pure alexia, pure word blindness). Visually agnosic patients can recognize objects presented to other sen- sory modalities. Clinically, apperceptive visual agnosia lies between and associative visual agnosia. Apperceptive visual agnosia results from diffuse posterior brain damage; associative visual agnosia has been reported with lesions in a variety of locations, usually ventral temporal and occipital regions, - 320 - V.qxd 9/28/05 10:49 PM Page 321

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usually bilateral but occasionally unilateral. Pathological causes include cerebrovascular disease, tumor, degenerative dementia (visual agnosia may on occasion be the presenting feature of Alzheimer’s dis- ease, the so-called visual variant, or posterior cortical atrophy), and carbon monoxide poisoning. A related syndrome which has on occasion been labeled as apper- ceptive visual agnosia is simultanagnosia (q.v.), particularly the dorsal variant in which there is inability to recognize more than one object at a time. Associative visual agnosia has sometimes been confused with optic aphasia (q.v.). References Farah MJ. Visual agnosia: disorders of object recognition and what they tell us about normal vision. Cambridge: MIT Press, 1995 Riddoch MJ, Humphreys GW. Visual agnosia. Neurologic Clinics 2003; 21: 501-520 Cross References Agnosia; Alexia; Cortical blindness; Optic aphasia; Prosopagnosia; Riddoch’s phenomenon; Simultanagnosia; Visual form agnosia

Visual Disorientation Visual disorientation refers to the inability to perceive more than a frag- ment of the visual field at any one time; it is sometimes characterized as a shifting fragment or island of clear vision. There may be difficulty fixating static visual stimuli and impaired visual pursuit eye movements. Visual disorientation may be demonstrated by sitting directly opposite the patient and asking them, while looking at the bridge of the examiner’s nose, to reach for the examiner’s hand held up in the peripheral field of vision. Once contact is made with the hand, the examiner holds up the other hand in a different part of the field of vision. Individuals with visual disorientation will find it hard to see the hand and will grope for it, sometimes mistakenly grasping the exam- iner’s clothing (“tie sign”) or face. Visual disorientation is secondary to, and an inevitable conse- quence of, the attentional disorder of dorsal simultanagnosia (q.v.), in which the inability to attend two separate loci leads to impaired local- ization. It may be a feature of Alzheimer’s disease; indeed, sometimes it may be the presenting feature, but there are usually signs of more generalized cognitive problems (e.g., impairment of episodic memory). References Farah MJ. Visual agnosia: disorders of object recognition and what they tell us about normal vision. Cambridge: MIT Press, 1995 Cross References Simultanagnosia; Visual agnosia

Visual Extinction Visual extinction is the failure to respond to a novel or meaningful visual on one side when a homologous stimulus is given simultane- ously to the contralateral side (i.e., double simultaneous stimulation), despite the ability to perceive each stimulus when presented singly. - 321 - V.qxd 9/28/05 10:49 PM Page 322

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Cross References Extinction; Neglect

Visual Field Defects Visual fields may be mapped clinically by confrontation testing. The exact pattern of visual field loss may have localizing value due to the retinotopic arrangement of fibers in the visual pathways: any unilat- eral area of restricted loss implies a pre-chiasmatic lesion (choroid, retina, ), although lesions of the anterior calcarine cortex can produce a contralateral monocular temporal crescent. Bilateral homonymous scotomata are post-chiasmal in origin; bilateral het- eronymous scotomata may be seen with chiasmal lesions. Topographically, typical visual field defects are: Retina: monocular visual loss, altitudinal field defects; central or centrocecal , ring scotoma Optic nerve: central or centrocecal scotoma; junctional scotoma of Traquair Optic chiasm: bitemporal hemianopia; junctional scotoma Optic tract: homonymous hemianopia, usually incongruous Lateral geniculate nucleus: homonymous hemianopia, usually incongruous Optic radiations: homonymous hemianopia, usually congruous; quadrantanopia : homonymous hemianopia, usually congruous; quadrantanopia; cortical blindness References Hämäläinen HA, Julkunen LAM. Treatment of visual field defects after stroke. Advances in Clinical Neuroscience & Rehabilitation 2004; 3(6): 17-18 Schiefer U. Visual field defects: essentials for neurologists. Journal of Neurology 2003; 250: 407-411 Trobe JD, Acosta PC, Krischer JP, Trick GL. Confrontation visual field techniques in detection of anterior visual pathway lesions. Annals of Neurology 1981; 10: 28-34 Cross References Altitudinal field defect; Hemianopia; Junctional scotoma, Junctional scotoma of traquair; Macula sparing, Macula splitting; Quadrantanopia; Scotoma

Visual Form Agnosia This name has been given to an unusual and highly selective visual per- ceptual deficit, characterized by loss of the ability to identify shape and form, although color and surface detail can be appreciated, but with striking preservation of visuomotor control (i.e., a pattern of deficits inverse to those seen in optic ataxia). This reflects selective damage to the ventral (“what”) stream of in the lat- eral occipital area, while the dorsal (“where”) stream remains intact, yet its workings are not available to .

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References Goodale MA, Milner AD. Sight unseen. An exploration of conscious and unconscious vision. Oxford, OUP, 2003 Cross References Agnosia; Optic ataxia; Visual agnosia

Visual Grasp Reflex - see SACCADES

Visuopalpebral Reflex - see BLINK REFLEX

Vocal Tremor, Voice Tremor Vocal or voice tremor is a shaking, quivering, or quavering of the voice. It may be heard in: Essential tremor Cerebellar disorders Spasmodic dysphonia/laryngeal dystonia Parkinson’s disease Motor neurone disease. The pathophysiology is uncertain but may relate to rhythmic con- tractions of the cricothyroid and rectus abdominis muscles. Cross References Dysphonia; Tremor

Von Graefe’s Sign Von Graefe’s sign is the retarded descent of the upper eyelid during movement of the eye from the primary position to downgaze; the lid “follows” the eye. This may be termed “lid lag,” although some author- ities reserve this term for a static situation in which the lid is higher than the globe on downgaze. Von Graefe’s sign is seen in thyroid oph- thalmopathy. Cross References Lid lag; Pseudo-von Graefe’s sign

Vorbereiden - see GANSER PHENOMENON

VOR Suppression - see VESTIBULO-OCULAR REFLEXES

Vulpian’s Sign - see PREVOST’S SIGN

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