Auditory brainstem responses and masking level differences from persons with brainstem lesion

Twenty subjects with abnormal auditory brainstem responses (ABR) and diagnosed brainstem lesion or disease were studied. Normal listeners were used as controls. The objective of the project was to examine the relationship of the particular ABR patterns exhibited by these subjects to the binaural masking level differences (MLD) and transbrainstem acoustic reflex (AR) patterns yielded by the same subjects. Patients whose ABR abnormalities commenced with brainstem potentials I, II, or III had small or no MLD and absent or abnormal AR. Patients whose ABR abnormalities commenced with brainstem potentials IV or V yielded normal MLD and AR behavior. Most important, these findings suggest that MLD size is influenced by activity which also contributes importantly to the development of the early auditory brainstem potentials.