Autonomic neuropathies

$24 $21 CRITICAL EVALUATION OF EVOKED POTENTIALS IN DIAGNOSIS OF MULTIPLE SCLEROSIS

MAUGUIERE,F., H6pital Neurologique, Lyon, France Delayed latencies of visual (VEPs), brainstem auditory (BAEPs) and somatosensory (SEPs) evoked p o t e n t i a l s are widely accepted as a valuable sign of c l i n i c a l l y s i l e n t demyelinating lesions of the sensory pathways in patients with suspected MS. Multimodal EPs approaches demonstrate that more than 9o% of patients with probable or d e f i n i t e MS have subnormal responses at least f o r one sensory modality. However abnormal EP can be viewed as a valuable argument f o r the diagnosis of MS only when the hypothesis of a single lesion responsible f o r a l l c l i n i c a l and electrophysiological signs can be d e f i n i t e l y eliminated. The results of a multimodal EP approach in our series of patients with suspected MS suggest that VEPs are the most e f f i c i e n t i n v e s t i g a t i o n s in MS. Indeed in patients with brainstem or "spinal" symptoms delayed VEPs, disclosing a c l i n i c a l l y s i l e n t lesion of the optic t r a c t s , prove the m u l t i f o c a l i t y of the disease, when abnormal BAEPs or SEPs are less unequivocal, even in the absence of any c l i n i c a l auditory or somatosensory impairment. In patients with isolated optic n e u r i t i s delayed BAEPs and SEPs are r a r e l y encountered. In acute m y e l i t i s EPs often f a i l to reveal multifocal lesions outside the spinal cord. Multimodal EPs study in MS should aim to answer the only crucial question f o r the neurologist i . e . : in which c l i n i c a l context, and in which percentage of cases the recording of EPs does help to diagnose MS ?

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$22 AUTONOMICNEUROPATHIES McLEOD JG, SAICH£LL P~ Dept. of Medicine, U n i v e r s i t y of Sydney, A u s t r a l i a Autonomic dysfunc'tion is manifested c l i n i c a l l y by impairment of bloodpressure and heart rate c o n t r o l , abnormal sweating, impotence, g a s t r o - i n t e s t i n a l disturbances, bladder dysfunction and p u p i l l a r y abnormalities. The autonomic nervous system is affected to some extent in many types of peripheral neuropathy but is seen most commonly in diabetes, Guillain-Barr#-Syndrome, amyloid disease, porphyria and some t o x i c neuropathies. Autonomic dysfunction is most l i k e l y to r e s u l t from conditions that a f f e c t the small myelinated and unmyelinated f i b r e s in the baroreceptor a f f e r e n t s , the vagal innervation of the heart and the sympathetic e f f e r e n t f i b r e s to the mesenteric vascular bed. Experimental studies of acrylamide neuropathy in the dog have demonstrated that the primary s i t e of autonomic damage is to the vagal a f f e r e n t f i b r e s from the a o r t i c arch, lungs and g a s t r o i n t e s t i n a l t r a c t . In experimental a l l e r gic n e u r i t i s there is demyelination and impairment of conduction in vagus and sympathetic nerves. Autonomic studies in man are designed to test the various function components of the autonomic nervous system and to detect early manifestations of disease