Auditory brain stem and middle latency responses in a patient with cortical deafness

Auditory brain stem (ABR) and middle latency responses (MLR) were recorded in a patient with bilateral temporal lobe lesions. Audiological and higher cortical functions were assessed using conventional behavioral methods. Roentgenological findings were presented for localizing the lesions. Initially the patient showed no behavioral response to sound. Subsequently the patient reported inconsistent awareness of environmental sounds and pure tone sensitivity was impaired to a severe degree. Higher cortical function was essentially intact and the patient was not aphasic. ABR and acoustic reflex findings were consistent with normal functioning of the auditory periphery and brain stem pathways. MLR component P_a was absent bilaterally. These findings suggest that MLR component P_a is bilaterally generated in the temporal lobes. Auditory cortex appears to play a role in auditory sensitivity in humans.