Auditory behaviors and auditory brainstem responses of infants with hypogenesis of cerebral hemispheres

Three infants with an almost complete absence of the cerebral hemispheres as a result of brain anomalies were studied both audiologically and neurologically. The brain anomalies were diagnosed by means of MRI and CT scans. Behavioral audiometry revealed reactions only to loud sound stimulations but auditory brainstem responses showed wave configurations and thresholds compatible with the ages of the infants. There were significant differences in the thresholds obtained by behavioral audiometry and auditory brainstem responses. It can be considered that these auditorily stimulated behavioral responses are evoked by auditory motor reflexes originating in the brainstem, but not by auditory perception.