Clinical correlates of brain-stem auditory evoked potential variables in multiple sclerosis. Relation to click polarity.

The correlations between clinical signs and BAEP latency, amplitude and dispersion variables were investigated in 98 multiple sclerosis patients. A new dispersion variable, the wave IV-V "shape ratio" (SR IV-V), correlated most strongly with brain-stem signs (i.e., nystagmus). Severely reduced wave IV-V amplitude was frequently found in patients with vertical nystagmus or internuclear ophthalmoplegia, and interpeak latency (IPL) III-V correlated most strongly with cerebellar dysfunction (i.e., ataxia). The results may reflect different localizing ability among the various BAEP variables. The association between ataxia and increased IPL III-V was significantly stronger for BAEP to C clicks than to R clicks. Patients with abnormal BAEPs to one polarity (C or R) but not to the other, had significantly more clinical dysfunction than patients with normal BAEPs to both C and R clicks. Hence, C vs. R discordance may be interpreted to indicate possible brain-stem dysfunction.