Audiologic evaluation of patients with localized intracranial lesions.

A battery of audiological tests for retrocochlear disorders was performed of 79 cases with localized intracranial lesions confirmed surgically or neurologically. The Type III trace of Békésy audiometry was found to originate from pathologies in the brainstem and the Type IV from abnormalities in the first neuron of the VIIIth nerve or in the brainstem. It was suggested that an unusually large amplitude peak in the Békésy tracing indicates a lesion in the temporal lobe. Large values of differential limen for short increment (DLSI) were found in patients with brainstem lesions. A good speech discrimination with a poor filtered speech discrimination apparently indicated supratentorial lesions. The binaural separation test using dichotically presented digit sounds was found to be helpful for differential diagnosis between the supratentorial and subtentorial lesions.