ABR findings in vertebrobasilar ischemia.

Auditory brainstem response (ABR) changes in the ischemic brainstem condition and the correlation between ABR and blood flow of the auditory pathway are not clear. In this study, ABR changes in two cases with brainstem ischemia are reported. In order to clarify the correlation between ABR changes and cochlear blood flow, experimental studies on guinea pigs with brain ischemia were performed. Changes of ABR in the human brainstem ischemic condition consisted of a decrease of the amplitudes of all waves and a delay in wave latencies. Even if ABR showed no response, it turned to normal when the blood flow was recovered. In the experimental study, the same changing patterns in ABR occurred in parallel with a decrease of the cochlear blood flow, and the cochlear blood flow was not zero when ABR became non-responsive. This suggests that ABR changes reflect the degree of ischemia in the auditory pathway, and that non-responsive ABR does not imply irreversible ischemic condition.