Anterior inferior cerebellar artery syndrome: fact or fiction.

A prospective analysis of patients referred by Otolaryngologists from a tertiary hospital for detailed assessment of the posterior cranial fossa was undertaken. The objectives were to evaluate radiological characteristics of the anterior inferior cerebellar artery (AICA) within the cerebellopontine angle (CPA) and the internal auditory canal (IAC), and to correlate these characteristics with ipsilateral auditory symptoms. Three hundred and thirty-two consecutive adult patients who presented with unilateral auditory symptoms were studied. All patients were referred by the Department of Otolaryngology at City Hospital, Birmingham, from October 1999 to October 2001. Magnetic resonance imaging (MRI) with three-dimensional Fourier Transformation Constructive Interference in Steady State (3D FT-CISS) was the imaging strategy used to investigate each patient. Six hundred and sixty-four sides were studied and the AICA loop was identified in all patients. Using a simple anatomical classification to type the loops: there were 412 type I loops (within the CPA), 202 type II loops (at the porus acousticus, extending up to 50% of IAC) and 50 type III loops (extending beyond 50% of IAC). There was a statistically significant association with unilateral hearing loss and type II and III AICA loops (P = 0.016 and P = 0.006 respectively). An association between the presence of a large diameter vascular loop in the CPA and unilateral auditory symptoms was not found to be significant (P > 0.05).