The brainstem auditory evoked responses in Alport's syndrome

Alport's syndrome is a "hereditary nephritis" associated with structural defects of basement membranes in kidneys, ears and eyes, with variable clinical expression. As the acoustic abnormalities are often subclinical, we studied the brainstem auditory evoked responses (ABR) and tonal audiometry in 12 patients (7 males, 5 females, mean age 32.50 +/- 16.70 years) with histologically documented renal lesions consistent with Alport's syndrome. ABR were used to document the altered acoustic-nerve conduction and transmission typical of the early stage of Alport's syndrome. In 11 patients (seven males, four females), we found bilateral delayed latency (I dx: 2.50 +/- 0.80 msec; III dx: 4.24 +/- 0.68 msec; V dx: 7.02 +/- 0.94 msec) and altered waveform I, III, V by ABR. By audiometry eight patients (six males, two females) showed a loss of medium-high tones, and this group included the patients with a negative ABR study. Therefore, the ABR is abnormal in Alport's syndrome; it may be positive in patients with normal tonal audiometry, usually all cochlear functions are grossly intact; the acoustic-nerve lesions in Alport's syndrome may precede the cochlear involvement and clinical hearing loss; the electrophysiological analysis does not identify the particular nervous structures involved in the acoustic pathways.