Author(s)
Michael F. Foster, DO
Douglas D. Backous, MD
Roberto A. Cueva, MD
Patrick C. Buchanon, DO
Affiliation(s)
Abstract:
Objective: Medial branch of Distal Anterior Inferior Cerebellar Artery (AICA) aneurysms are exceedinglyrare, but potentially lethal if ruptured. We report on two cases of a distal AICA aneurysm masquerading asan intracanalicular vestibular schwannoma and review the literature.Case 1: 47yo Hispanic male experienced right sudden SNHL and was treated with combined high dose oralprednisone taper and intratympanic (IT) Dexamethasone injections with complete recovery. An MRI revealeda right 1cm intracanalicular internal auditory canal lesion. The patient underwent elective craniotomy througha retrosigmoid approach. Intraoperatvely the mass was identified as an aneurysm arising from a loop ofthe AICA within the IAC. The aneurysm was successfully clipped. 4-year post op angiogram demonstratedpatent AICA without aneurysm.Case 2: 51yo Caucasian male with sudden deafness on the left side. Subsequent MRI showed a 7x7mmleft cerbellopontine angle (CPA) mass with unusual calcification. Patient elected to have the masssurgically resected via a translabyrinthine approach. Inraoperatively the mass was identified as a distal AICAaneurysm and was clipped successfully. Postoperative angiogram revealed no residual or recurrent aneurysmand a patent AICA.Conclusion: Vestibular Schwannomas make up the 85% of CPA and intracanalicular masses. Aspects of ourcases and review of the literature provide insight into atypical signs and symptoms that can raise suspicion fora distal AICA aneurysm. These characteristics can provide prudent insight when counseling a patient onetiology of their IAC lesion and the plan of intervention.Define Professional Practice Gap & Educational Need: 1. Lack of awareness 2. Lack of contemporaryknowledgeLearning Objective: 1. To call to attention the prevalence and characteristic clinical and radiologic features ofa distal AICA aneurysm that can mimic the presentation of a vestibular schwannoma.Desired Result: Physicians will critically examine an atypical appearing IAC mass and order furtherangiographic testing when necessary.Indicate IRB or IACUC Approval: Exempt