Distal Mycotic Aneurysm of the AICA Mimicking Intracanalicular Acoustic Neuroma

Abstract

Among cases of cerebellopontine angle (CP) lesions, vascular lesions involving the internal auditory canal are extremely rare. We report a distal mycotic fusiform pseudoaneurysm of the anterior inferior cerebellar artery that simulated an acoustic neuroma on presentation. Its surgical management is described and possible pathophysiologic mechanisms are discussed along with the currently available literature. CASE REPORTA 60-year-old woman in otherwise healthy condition experienced onset of acute dizziness in the context of a twenty year history of rightsided tinnitus that had recently accentuated. There was no history of chronic mastoiditis. She had no facial nerve disfunction or any hearing complaints, and audiological assessment was excellent (speech reception threshold (SRT) 10 dB, speech discrimination score (SDS) 92%). Magnetic resonance imaging (MRI) examination (Figure 1) revealed a 6-7 mm lesion in the proximal internal auditory canal occupying approximately 1/3 of the porus and minimally protruding into ABSTRACT: Background: Among cases of cerebellopontine angle lesions, vascular lesions involving the internal auditory canal are extremely rare. We report a distal fusiform mycotic pseudoaneurysm of the anterior inferior cerebellar artery (AICA) that simulated an acoustic neuroma on presentation. Methods: A 60-year-old woman was investigated for recent onset of acute dizziness. Laboratory and radiographic investigations are presented, as well as the surgical management of the patient and pathological examination of the aneurysm. Conclusions: An exceptionally rare case of distal mycotic intracanalicular pseudoaneurysm of the AICA with intraluminal thrombus and fusiform anatomy is described. In our review of the literature (1966-present), only five other intracanalicular AICAaneurysms were encountered, none of which were infectious in etiology. The possible pathophysiologic mechanisms of distal AICA-aneurysms are discussed along with the currently available literature. CASE REPORTthe CP angle. The lesion was hyperintense in T1 and enhancing with gadolinium injection. On T2-weighted MRI, the lesion was found to be hypointense. On the basis of these findings a pre-operative diagnosis of right intracanalicular acoustic neuroma was made by both neuroradiologists and the neuro-otology team. In view of the excellent hearing, an attempt at hearing preservation was planned for removal of the mass. OperationThe patient was placed in the left park-bench position with the appropriate needle electrodes placed for intraoperative monitoring of the https://www.cambridge.org/core/terms. https://doi

Intrameatal aneurysm of the anterior inferior cerebellar artery

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14] The average age of the patients reported (53 years of age) does not differ from most aneurysm series with SAH but there is a striking female prevalence (14:1). Most patients, except those who had only VIIIth nerve symptoms, presented with SAH associated with a deficit of the VIIth and VIIIth cranial nerves.…”

Occipital Artery-Anterior Inferior Cerebellar Artery Bypass With Microsurgical Trapping for Exclusively Intra-meatal Anterior Inferior Cerebellar Artery Aneurysm Manifesting as Subarachnoid Hemorrhage

“…Intra-meatal AICA aneurysms are extremely rare, with only 16 previous cases. [2][3][4][5][7][8][9][10]12,16,17,[19][20][21] Ten of these 16 patients were treated by microsurgical neck clipping 4,[8][9][10]17,[19][20][21] by opening the meatus with extensive nerve dissection, 5 patients underwent meatal loop trapping without bypass, 2,3,7,12,16) and one patient with unruptured aneurysm was managed by microsurgical packing of the internal auditory canal. 5) None of the 5 patients treated by simple meatal loop trapping developed cerebellar infarction, probably due to the favorable collateral blood supplies from dominant PICA and superior cerebellar artery.…”

“…None of the 5 previous patients undergoing meatal loop trapping developed brain stem infarction. 2,3,7,12,16) The subarcuate artery rarely originates from the meatal segment of the AICA (4%), but occlusion could result in VII/VIII cranial nerve palsy. 14) Taken together, meatal loop trapping is considered to carry acceptable risks despite the substantial risk of hearing disturbance caused by ischemia.…”

“…[2][3][4][5][7][8][9][10]12,16,17,[19][20][21] Female prevalence (female/male＝15/1) is remarkable, with mean patient age of 53 years. Most patients (15/16) developed subarachnoid hemorrhage (SAH) at the onset, [2][3][4][7][8][9][10]12,16,17,[19][20][21] and only one presented with hearing disturbance due to the mass effect of the aneurysm. 5) The pathological nature of intra-meatal aneurysm is unclear.…”

“…Most cases were saccular aneurysm at non-branching sites of AICA, whereas one patient had mycotic aneurysm mimicking intracanalicular acoustic neuroma. 3) Surgical management of distal AICA aneurysm includes microsurgical neck clipping and meatal loop trapping, but the optimal management procedure has not yet been determined, especially if the affected AICA supplies a wide vascular territory and the aneurysm is located deeply inside the internal auditory canal.…”