• Aïda Kawkabani Marchini, Pascal J Mosimann, Jean-Pierre Guichard, Monique Boukobza, and Emmanuel Houdart.
• Department of Neuroradiology, Hôpital Lariboisière, Paris, France.
• J Neuroimaging. 2014 Jul 1;24(4):404-6.

Background And PurposeUnruptured anterior inferior cerebellar artery (AICA) aneurysms are rare but potentially lethal cerebellopontine angle (CPA) lesions that may be misdiagnosed as vestibular schwannomas when they present with vestibulo-cochlear symptoms.MethodsWe report two cases of unruptured but symptomatic AICA aneurysms initially referred to us as atypical vestibular schwannomas requiring surgery. Two discriminant MR features are described.ResultsOne patient refused treatment. The other was successfully treated by coil occlusion.ConclusionsCaution is advised before suspecting a CPA mass to be a purely extra-canalicular schwannoma, given its extreme rarity. Deafness and cerebellar ischemia may be prevented if AICA aneurysms are correctly identified preoperatively. In the absence of specific arterial imaging, two MR features may distinguish them from vestibular schwannomas: (1) the absence of internal auditory canal enlargement and (2) the "blurry dot sign," representing blood flow artefacts on pre- and postcontrast studies.Copyright © 2013 by the American Society of Neuroimaging.

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