Internal auditory canal vascular loops and sensorineural hearing loss.

The relationship between vascular loops in the internal auditory canal and VIII nerve disorders was examined by performing pneumatic computerized tomographic (CT) cisternography in patients with idiopathic sudden deafness, idiopathic sensorineural hearing loss, and Meniere's disease. The incidence of vascular loops was higher in the diseased group than in the control group, viz. 19 of 61 cases (30%) in the former, compared with only 6 of 88 cases (7%) in the latter. The loops were classified as of Types I-IV according to the proximity to the fundus of the internal auditory canal. A large proportion of the loops found in the diseased group were classified as Type II or III. In most of the patients with vascular loops, the hearing loss was of the cochlear type, and in most cases, normal responses were obtained by the caloric test. Therefore, we concluded that vascular loops may be a possible cause of VIII nerve disorders and that this mechanism may involve circulatory disorder.