Labyrinthine artery aneurysm as an internal auditory canal mass

Internal iliac artery aneurysm masquerading as a sciatic nerve schwannoma: illustrative case

BACKGROUND

Schwannomas are common peripheral nerve sheath tumors. Imaging techniques such as magnetic resonance imaging (MRI) and computed tomography (CT) can help to distinguish schwannomas from other types of lesions. However, there have been several reported cases describing the misdiagnosis of aneurysms as schwannomas.

OBSERVATIONS

A 70-year-old male with ongoing pain despite spinal fusion surgery underwent MRI. A lesion was noted along the left sciatic nerve, which was believed to be a sciatic nerve schwannoma. During the surgery for planned neurolysis and tumor resection, the lesion was noted to be pulsatile. Electromyography mapping and intraoperative ultrasound confirmed vascular pulsations and turbulent flow within the aneurysm, so the surgery was aborted. A formal CT angiogram revealed the lesion to be an internal iliac artery (IIA) branch aneurysm. The patient underwent coil embolization with complete obliteration of the aneurysm.

LESSONS

The authors report the first case of an IIA aneurysm misdiagnosed as a sciatic nerve schwannoma. Surgeons should be aware of this potential misdiagnosis and potentially use other imaging modalities to confirm the lesion before proceeding with surgery.

“Plugged” Anterior Inferior Cerebellar Artery Aneurysm Causing Facial Palsy, Hearing Loss, and Subarachnoid Hemorrhage Treated by a Translabyrinthine Approach

Anterior inferior cerebellar artery (AICA) aneurysms are rare, less than 1%-2% of all intracranial aneurysms. Aneurysms of the distal AICA are even less common and can present with hearing loss and facial paralysis because of their relationship with the internal auditory canal (IAC). A 65-year-old male was followed for fluctuating left facial weakness and left-sided hearing loss for over a year. Serial magnetic resonance imaging (MRI) scans showed a mass near the left IAC, thought to be a vestibular schwannoma. Just prior to his next clinic visit, the patient deteriorated suddenly from a subarachnoid hemorrhage. Cerebral angiography revealed a 5.5 mm saccular aneurysm at the distal left AICA, which was clip ligated via a translabyrinthine (TL) approach. The patient had a good functional outcome (modified Rankin Scale [mRS] 1) after 30 days despite persistent left facial weakness. Stable obliteration of the aneurysm was demonstrated by cerebral angiography postoperatively. Distal AICA aneurysms are rare and can have a similar presentation to tumors in the cerebellar pontine angle. Because of the unique anatomy of the distal AICA, open clip ligation via a TL approach is an effective method to secure these aneurysms.

Variaciones anatómicas del origen de la arteria laberíntica en una muestra de encéfalos en Colombia

Introducción. La arteria laberíntica transcurre a través del meato acústico interno hasta llegar al oído interno, aportando allí su irrigación. Se han descrito dos posibles variantes anatómicas de su origen: como rama directa de la arteria basilar o como rama de la arteria cerebelosa anteroinferior.Objetivo. Identificar la prevalencia del origen de la arteria laberíntica.Materiales y métodos. Se realizó un estudio analítico descriptivo con métodos cuantitativos sobre el origen de la arteria laberíntica en una muestra de 29 encéfalos obtenidos por muestreo a conveniencia.Resultados. Se determinó que la arteria laberíntica se originó de la arteria basilar en 22 (75.9%) encéfalos; en los 7 (24.1%) restantes esta surgía como rama de la arteria cerebelosa anteroinferior.Conclusión. El origen de la arteria laberíntica en la muestra seleccionada tiene una mayor prevalencia en la arteria basilar respecto a la arteria cerebelosa anteroinferior, hallazgo que se asemeja a algunas investigaciones contrastadas con este estudio.

Cranial Nerve Foramina: Part II - A Review of the Anatomy and Pathology of Cranial Nerve Foramina of the Posterior Cranial Fossa

Cranial nerve foramina are integral exits from the confines of the skull. Despite their significance in cranial nerve pathologies, there has been no comprehensive anatomical review of these structures. Owing to the extensive nature of this topic we have divided our review into two parts; Part II, presented here, focuses on the foramina of the posterior cranial fossa and discusses each foramen's shape, orientation, size, surrounding structures, and structures that pass through it. Furthermore, by comparing foramen sizes against the cross-sectional areas of their contents, we determine the amount of free space available within each. We also review lesions that can obstruct each foramen and discuss the clinical consequences.