The choice of ABR click polarity and amplitude variables in multiple sclerosis patients.
Evoked brainstem responses (ABR) to 75 dB nHL condensation (C), rarefaction (R), and alternating (A = C+R) clicks were investigated in healthy subjects and in patients with multiple sclerosis. A new wave IV-V 'shape ratio' (SR IV-V) was most sensitive. SR IV-V correlated most strongly with clinical MS classification, and seemed to be rather specific for retrocochlear dysfunction. Wave IV-V amplitude was also more sensitive than the common IV-V amplitude ratio. The variability of latencies and interpeak latencies was lower in ABR to A clicks than in ABR to either R or to C clicks. In patients, fewer subcomponents were found in ABR to A than in ABR to R and C clicks. ABR to A clicks were on the average slightly more sensitive than either C or R click ABR. Our results suggest that both A-mode ABR and the 'dispersion' variable SR IV-V can be used without significant problems in the diagnosis of brainstem demyelination. A test protocol which requires ABR to both C and R clicks to be abnormal, will, however, be less sensitive, though probably more specific.
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Department of Neurology, University Hospital of Trondheim, Regionsykehuset, Norway.
D000161:Acoustic Stimulation; D000328:Adult; D001933:Brain Stem; D015834:Cochlear Diseases / Q000209:etiology / Q000503:physiopathology; D016057:Evoked Potentials, Auditory, Brain Stem; D005260:Female; D006309:Hearing / Q000502:physiology; D006311:Hearing Disorders / Q000209:etiology / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology