Objective:Our goal was to describe three cases of acute sensorineural hearing loss (ASNHL) that might be caused by arterial dissection of the vertebrobasilar system.Design:Retrospective case review. Setting: Yamagata University Hospital, Yamagata, Japan.Patients:Thirty-seven patients with ASNHL underwent magnetic resonance (MR) imaging between September 1993 and March 1995.Interventions:Proton density and T2-weighted axial images and three-dimensional spoiled gradient-recalled acquisition in steady state (3-D SPGR) imaging with gadopentetate dimeglumine were obtained with a 1.5 T MR system in all patients. T1-weighted images were obtained in 23 patients. Vertebral angiography (VAG) was performed in 4 of the 37 patients.Results:In 3 of the 37 patients, the presence of vertebrobasilar dissection was confirmed: contrast-enhanced 3-D SPGR images disclosed double lumen of the proximal basilar artery and/or the ipsilateral vertebral artery in all of the 3 patients. In two of them, the vertebrobasilar dissection was also confirmed by VAG. The hearing loss of all three patients improved after the onset. Audiograms revealed no characteristic pattern of the initial hearing loss among them.Conclusions:Vertebrobasilar dissection may cause an intramural hematoma involving the orifice of the anterior inferior cerebellar artery or a distal thromboembolism reducing the blood flow of the labyrinthine artery; these conditions can lead to onset of hearing loss. Arterial dissection of the vertebrobasilar system might be one of the causes of ASNHL.