Auditory brain stem responses in infantile spasms.

Auditory brain stem evoked responses (ABRs) and behavioral thresholds were studied in 30 infants with infantile spasms to determine the level of the lesion causing their inattention to sound stimuli. ABR thresholds, peak latencies of waves I and V and the peak interval latency of wave V-I were measured; behavioral audiometric thresholds were determined through conditioned-orientation-reflex (COR) audiometry. Thirty per cent of the infants (9 cases) with infantile spasms showed ABR abnormalities with respect to age-matched controls. The ABR abnormalities were classified into partial disappearance of latter waves (5 cases), prolongation of the wave V-I peak interval (3 cases) and no response (1 case). These findings are clear evidence that brain stem involvement may occur in infantile spasms. Eighty-six per cent of the patients showed threshold elevation by behavioral audiometry which may reflect by cortical dysfunction inherent in psychomotor retardation, as there was no peripheral hearing loss. Our results reveal that brain stem involvement can occur in patients with infantile spasms and their poor responses to sound are due to psychomotor retardation.