Changes in guinea pig cochlea after transient cochlear ischemia.

Perturbation of cochlear microcirculation, that is, ischemia is a major cause of hearing impairment. Earlier studies examined the short-term (≤7 days) effect of cochlear ischemia. This study characterized the long-term (4 weeks) functional and morphological changes in adult guinea pig cochleae subject to transient ischemia by clamping the labyrinthine artery for 0.25-3 h. Notably, cochlear ischemia for over 1 h caused an increase of auditory brainstem response thresholds and loss of high-frequency hearing, basal-turn hair cells, and spiral ganglions. Auditory recovery may be possible after 30-min ischemia. The extent of the functional and morphological changes depended on the ischemia period, and the changes progressed in extent from the apical to the basal turn in an orderly fashion.