The anterior inferior cerebellar artery in the internal auditory canal.

It has been proposed that compression of the auditory and vestibular nerve trunks by vascular loops might be the cause of otherwise unexplained hearing loss, tinnitus, and vertigo, as well as Meniere's disease. We studied the human temporal bone histological collection at the Massachusetts Eye and Ear Infirmary to determine whether audiovestibular symptoms could be correlated with the presence of the anterior inferior cerebellar artery within the internal auditory canal. Anterior inferior cerebellar artery loops were found within the internal auditory canals of 12.3% of 1327 temporal bones, about half the number found when preparations with intact brains are studied. This difference can be attributed to avulsion of the anterior inferior cerebellar artery during removal of the brain at autopsy. There were 5 cases of unexplained unilateral hearing loss with anterior inferior cerebellar artery loops: 3 in the opposite ear and 2 in both ears. There were 2 cases with unilateral unexplained tinnitus with anterior inferior cerebellar artery loops: 1 in the involved ear and 1 in the opposite ear. A case with bilateral tinnitus had an anterior inferior cerebellar artery loop in 1 ear. There were 29 cases of vertigo with no peripheral histopathological correlate or central nervous system disorder; anterior inferior cerebellar artery loops were found in the internal auditory canals of 7 (12.5%) of the 56 ears in this group, which is not significantly different from the 12.3% incidence recorded for the entire collection. In 23 cases of unilateral Meniere's disease, there were anterior inferior cerebellar artery loops in the hydropic ears in 3, the opposite ear in 1, and both ears in 1. We can find no correlation between unexplained hearing loss, tinnitus, vertigo, or Meniere's disease and the presence of the anterior inferior cerebellar artery in the internal auditory canal.