Binaural voltage summation of brainstem auditory evoked potentials: an adjunct to the diagnostic criteria for multiple sclerosis.

Brainstem auditory evoked potential (BAEP) amplitude is modified according to whether or not the stimulus is applied monaurally or binaurally. In normal subjects, wave V amplitude increases by an average of 68.7% upon changing stimulation from monaural to binaural. From earlier studies there is evidence that brainstem potential amplitude is reduced in patients with multiple sclerosis (MS) but none to suggest that binaural stimulation results in increased amplitude. This study evaluated the extent of binaural summation of BAEPs in patients with MS. In a large majority of patients with MS who have no hearing deficit, BAEPs showed no increase in wave V amplitude on binaural stimulation. This finding is in contrast to the normal group and thus has diagnostic importance. Measurements of binaural summation therefore might usefully be applied to the clinical assessment of disease progression, or lack of it, in individual patients.