Electrically elicited blink reflex in diagnosis of multiple sclerosis. Review of 260 patients over a seven-year period.

The blink reflex obtained from 260 patients with suspected multiple sclerosis was analysed according to clinical criteria for diagnosis. The R1 component was dealyed on one or both sides in 96 of 145 patients with definite diagnosis (66 per cent), 32 of 57 with probable diagnosis (56 per cent), and 17 of 58 with possible diagnosis (29 per cent). The incidence of abnormal R1 rose with increasing duration of illness in each category. When the reflex was analysed according to the clinical localization of the lesion in the 260 patients, R1 was abnormal in 49 of 63 patients with pontine signs (78 per cent), 59 of 104 with other brain-stem signs (57 per cent), and 37 of 93 with no clinical brain-stem signs (40 per cent). Alteration of R2 was less specific but, when seen in the face of a normal R1, was usually associated with clinical signs suggesting lateral medullary lesions. These fingings offer direct evidence that conduction through demyelinated zones in the central nervous system is indeed slowed and that the degree of slowing can be measured objectively by means of this simple technique in man. The high inicdence of delayed R1 in patients with no clinical pontine signs suggests that the test may be used to document a clinically silent pontine lesion in multiple sclerosis and help to establish the anatomical dissemination of pathology.