Interaural time discrimination and brain stem potentials in patients with multiple sclerosis

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Abstract
Twenty-nine patients with multiple sclerosis who had normal audiograms and good speech discrimination were studied. A two-alternative forced choice paradigm was used to determine interaural time and intensity JNDs for white noise bursts. Short-latency (< l0 ms) click evoked potentials were recorded between the vertex and earlobe. The subjects with normal interaural time JNDs usually had normal responses even if the interaural intensity JNDs were abnormally large. Those with abnormally long time JNDs usually had abnormal evoked responses; those with the longest time JNDs often exhibited no waves beyond the compound action potential of the auditory nerve. Patients with abnormal time JNDs and different evoked potentials on stimulating each ear showed a lateralization bias: whenever the interaural time of the stimulus was less than the subject's time JND the stimulus was localized towards the side for which potentials were more normal. [Supported by NIH and the Hôpital Cantonal of Geneva, Switzerland.]