Air CT cisternography of anterior inferior cerebellar artery loop simulating an intracanalicular acoustic neuroma.

Acoustic neuromas larger than 1 cm are usually apparent on routine computed tomography (CT) after contrast enhancement, but smaller lesions escape detection [1, 2]. Metrizamide CT cisternography can demonstrate small lesions, but it is not accurate for the detection of intracanalicular lesions [1, 3]. Pantopaque meatocisternography can detect intracanalicular lesions but has a high percentage of inconclusive results [4]. Air CT cisternography is considered to be the most sensitive procedure for the demonstration of very small and totally intracanalicular acoustic neuromas [5, 6]. A case is presented where partial filling of the internal auditory canal, simulating an intracanalicular tumor, was due to a loop of the anterior inferior cerebellar artery (AICA).