J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.45.6.501 on 1 June 1982. Downloaded from Journal of Neurology, Neurosurgery, and Psychiatry 1982;45:501-506 Hair follicle discrimination dysfunction in multiple sclerosis patients RICHARD J SCHNEIDER, RONALD BURKE From the Laboratory ofNeuroscience, Maryland Institute for Emergency Medical Service Systems, Baltimore, Maryland, USA SUMMARY A method was developed of assessing somatosensory deficits quantitatively using hair follicle displacement as a stimulus within a psychophysical signal detection task paradigm. Multi- ple sclerosis patients with and without somatosensory disturbances could be differentiated and compared with normal subjects. This method may distinguish patients with somatosensory dys- function, and dorsal funiculus neuropathology may underlie this distinction. Concern with the difficulty of assessing sensory per- could account for these failures and which suggested ception is common to physiology, psychology and further investigation that might demonstrate these sensory losses.'8-20 Thus, we showed that neurology. However, the outcome of studies of sen- Protected by copyright. sory function in these separate but related sciences information from hair follicle stimuli was have seldom been brought together. Advances in transmitted to the primary somatosensory cortex the neurophysiology of single cells and fibres in the uniquely via the dorsal funiculus in Macaca mulatta cutaneous sensory system of the body (somatosen- monkeys.'9 20 21 These studies on the monkey sory electrophysiology) and the psychology of suggested that neurological deficits related to dorsal stimulus-response relationships (psychophysics) column dysfunction would be detected especially may provide answers to questions concerning the well by tests of hair follicle displacement detection of somatosensory dysfunction. discrimination. Further, psychophysical methods The general problem is how to identify and meas- had evolved which enabled us to control for ure differences in sensory acuity relating to misleading results deriving from psychophysical physiological organisation (for example, somatosen- factors (for example response bias) in gross sory pathway anatomy and function), psychophysi- neurological examination.2' 23 This study combined cal factors (for example, the cognitive significance of our insights on the transmission of hair follicle responses), and neurological pathology relating to displacement sensation in monkeys with disease or injury. For example, both in man and psychophysical methods for analysis of sensory monkeys, researchers have had difficulty in deter- acuity. The purpose of this present study has been to http://jnnp.bmj.com/ mining deficits ensuing from lesions to selected create an objective, quantifiable and sensitive means pathways, such as, the dorsal funiculus.-''0 of detecting somatosensory deficits in patients with Although some researchers were able to show sus- spinal cord neuropathology. We have investigated tained sensory deficits in monkeys,' 1-13 a precise, patients with sensory pathology caused by the quantifiable method of demonstrating the tradition- demyelination or plaque formation associated with ally taught pattern of dysfunction eluded them. multiple sclerosis. Moreover, the attempt to show deficits with simple passively applied stimuli led to failures which stimu- Methods on September 30, 2021 by guest. lated speculation on differing roles for the dorsal funiculus and to explanations involving Multiple sclerosis patients were solicited from a group pathway'4-'6 referred to the Department of Hyperbaric Medicine at the redundancy of spinal sensory pathways."' Mean- Maryland Institute for Emergency Medical Services Sys- while, other evidence was coming to light which tems for experimental treatment with hyperbaric oxygen. Address for reprint requests: Dr RJ Schneider, Laboratory of All had been diagnosed as having multiple sclerosis by at Neuropsychology, Building 9, Room IN107, National Institute of least two physicians. Their sensory symptoms were evalu- Mental Health, Bethesda, MD 20205, USA. ated from medical records, from interviews and from a Received 21 June 1981 and in revised form 13 November 1981 neurological examination prior to the testing sessions. Five Accepted 12 December 1981 patients were selected for study. Three of them-males 501 J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.45.6.501 on 1 June 1982. Downloaded from 502 Schneider, Burke aged 35, 38 and 48-had sensory symptoms which had not watt bulbs. The mechanical stimulus was delivered by a resolved at the time of the study. They all complained of galvanometer (MFE, model R-4-154) which oscillated at a sensory loss or paraesthesiae-numbness, tingling, temp- frequency of 10 Hz. A 1-5 mm long brass rod was attached erature sensations-both transiently in the past and at the at a right angle to the longitudinal axis of the galvanometer time of testing. All could walk, but they had difficulty with shaft (fig). This rod contacted and displaced hair follicles balance, motor control and coordination of the legs. 1 mm above the skin surface of the subject's leg. Hair folli- Two-a male aged 39 and a female aged 28-had no sen- cle displacement was at either 9-45 mm (S+) or 6-20 mm sory symptoms at the time of the study. The female patient (S-) measured at the tip of the oscillating rod. Thus, the had experienced sensory paraesthesiae in the past which difference in hair displacement to be discriminated at the had resolved. The male had never complained of sensory tip of the rod was 3-25 mm. A blind prevented the subject disturbances, but had a great deal of motor difficulty. The from viewing the stimulus delivery. A trough restrained leg four normal control subjects were drawn from the popula- movements while comfortably supporting the leg of the tion of the Institute's employees; they were two females seated subject (fig). A holder for the galvanometer per- and two males aged 28, 32, 26 and 34 years, respectively. mitted omnidirectional placement while damping vibra- Female subjects refrained from shaving their legs for two tion; it avoided cues being transmitted to the subject via weeks prior to testing. the leg restraint trough. By means of electromechanical and logic circuitry a The sequence of events was as follows. The central pro- sequence of events constituting a psychophysical yes/no gramming equipment initiated a discrete trial every eight discrimination task was presented to subjects in a manner seconds, the start of the trial being denoted by a green consistent with signal detection theory (TSD).21 The pro- lamp. Two seconds later, either of the two amplitudes of cedure and the associated series of events as applied by us hair displacement was presented with equal probability are described below. These events included an alerting (p(S+) = p(S-) = 0.5) in a quasirandom sequence. The light, a mechnical hair displacement stimulus and a feed- subject identified which of the two stimuli was being pre- back light. The lights were standard green and white 7-5 sented either by pressing or refraining from pressing a Protected by copyright. OX. http://jnnp.bmj.com/ on September 30, 2021 by guest. Figure Hair follicle displacement stimulus arrangement. The subject sits with his or her leg resting in an adjustable, plexiglass trough. The hair follicle stimulator is held by a vibration damping, omnidirectional supporting stand. The stimulator oscillates a brass rod which displaces hair follicles both rostrally and caudally (depending on the phase ofthe oscillation) during each stimulus presentation. The rod oscillates along the long axis ofthe leg. Holes in the trough permit access to medial, lateral andposterior dermatomes as well as anterior shown here being stimulated. Inset: Close-up ofstimulator and holder. J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.45.6.501 on 1 June 1982. Downloaded from Hair follicle discrimination dysfunction in multiple sclerosis patients 503 hand held button. A response when S+ was presented was tioned above, and the experimenter was not in the room defined as a correct identification. In all cases a stimulus with the subject. Testing continued until a series of 180 was presented for a maximum of 2 seconds. If a button discrete trials had been presented. Each subject was tested press response did not occur during this observation inter- repeatedly, various numbers of times at irregular intervals. val, the subject was considered to have refrained from The results of the experiment were analysed in pressing. The alerting lamp and the hair follicle displace- accordance with signal detection theory. Research has ment stimulus (either S+ or S-) were extinguished demonstrated the reduced variability inherent in immediately following the button press response or the dependent variables based on the assumptions of signal elapse of the two second observation interval. If a correct detection theory.24 Preliminary research in this laboratory identification was recorded, which could either be pressing has confirmed this result25-27 and demonstrated the the button when S+ was presented or refraining from pres- independence of the signal detection theory sensitivity sing the button when S- was presented, the white lamp was measure d' and the associated criterion or bias measure illuminated for 0-5 seconds. Incorrect identification did not beta (/3). These results recommend d' as a superior cause this (feedback) lamp to