Experimental study of transient cochlear ischemia as a cause of sudden deafness

Figure 3 Changes in auditory brainstem response threshold after transient cochlear ischemia. Auditory brainstem response (ABR) threshold before vertebral artery occlusion was defined as 0 dB. With 5 min ischemia, the ABR threshold at 8 kHz recovered almost completely on days 1 and 4, but became slightly worse on day 7, likely due to delayed neural cell death. With 15 min ischemia, the ABR threshold was almost constant after day 1. It remained constant in the range of 20-30 dB. The vertical scale indicates grade of hearing loss, expressed as change in ABR threshold.