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Case Reports in Neurological Medicine
Volume 2014 (2014), Article ID 435953, 4 pages
http://dx.doi.org/10.1155/2014/435953
Case Report

Thrombosed Large Distal Posterior Inferior Cerebellar Artery Aneurysm Mimicking an Infratentorial Ependymoma

Department of Neurosurgery, Kwong Wah Hospital, 25 Waterloo Road, Hong Kong

Received 16 December 2013; Accepted 7 January 2014; Published 11 February 2014

Academic Editors: S. T. Gontkovsky, R. Koide, M. Toft, and V. Wang

Copyright © 2014 Peter Yat Ming Woo et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Large or giant intracranial aneurysms can simulate brain tumors clinically and radiologically by virtue of their progressive mass effect. Unlike aneurysms from alternative locations, those arising from the distal posterior inferior cerebellar artery (PICA) are uncommon. We report a patient who experienced progressive hemiparesis with magnetic resonance imaging findings suggestive of an infratentorial ependymoma. Intraoperatively, a thrombosed large aneurysm of the distal PICA was unexpectedly encountered. The aneurysm was clipped and the patient did not develop any permanent neurological deficit. This case illustrates the radiological nuances of large aneurysms and infratentorial ependymomas. Three-dimensional contrast-enhanced magnetic resonance angiography can be falsely negative and the importance of the “target” sign is emphasized. One should be cognizant of this possible diagnosis for patients with midline fourth ventricular lesions in order to reduce surgical risk.