Cryptic cerebellopontine angle neuroglial cyst presenting with hemifacial spasm

Abstract

Hemifacial spasm (HFS) is commonly caused by a vascular loop compressing the Root Exit Zone (REZ) of the facial nerve. We report a case of HFS caused by a vascular loop that was abnormally displaced by a neuroglial cyst not seen in Magnetic Resonance Imaging (MRI). Microvascular decompression (MVD) was planned and the patient underwent a key-hole retromastoid posterior fossa exposure. A cystic lesion was found in the cerebellopontine angle (CPA), located around the seventh and eighth cranial nerves extending from the porous acousticus to the brainstem REZ of the facial nerve. The cyst wall was partially excised revealing the region of the neurovascular conflict. MVD of the facial nerve was performed with immediate postoperative complete resolution of the patient's symptoms.

Enterogenous cyst as a rare cause of hemifacial spasm

“…17 However, the T1-weighted MRI of our patient showed a hypointense lesion, which may be explained by the varying protein content of the cyst fluid. Tumors Cerebellar astrocytoma 10 Ependymal or neuroglial cyst 8,15 Hemangioma at the geniculate ganglion 2 Ependymoma of the fourth ventricle 13 Enterogenous cyst 16 and the present report Hamartoma of the floor of the fourth ventricle 12…”

“…In addition we have added some recent reports to the list of unusual causes of HFS (Table 1). [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] Enterogenous cysts (ECs) are rare congenital lesions mostly found in the spinal canal at the lower cervical and upper thoracic levels and have been reported only rarely in the CPA cistern. The characteristic radiological features of EC are of a round or lobulated non-enhancing cyst with isointense or hyperintense signal on T1-weighted and hyperintense signal on T2-weighted MRI, and mild restriction on diffusion weighted images.…”

Knowledge Based Approach in Differential Diagnosis of Intracranial Cysts -A Requisite to Avoid Unwarranted Interventions

“…[3][4][5][6][7][8] Most common is however intracranial intracerebral location, especially frontal lobe 1 as in our patient. The inner layer of these lesions consists of ependymal lining surrounded by an outer layer of neuroglial tissue (astrocytes).…”

Hemifacial Spasm Caused by a Huge Tentorial Meningioma

“…When the artery is located between the tumor and facial nerve, the artery may be trapped and begin to compress the nerve as the tumor grows. The standard surgical treatment for this tumor and the associated HFS is microsurgical removal of the tumor first, with MVD added selectively according to the anatomy around the CPA 6,11,19) . Tumors remote to the CPA causing HFS are rarely reported and the pathogenic mechanism is not clear.…”

“…In most cases, mechanical compression of the facial nerve at the root entry zone (REZ) by blood vessels is the main pathophysiological mechanism, and surgical treatment using microvascular decompression (MVD) is performed for the majority of patients. HFS can also develop as a result of other pathological conditions around the cerebellopontine angle (CPA), such as tumors, aneurysms, or arteriovenous malformations involving the REZ of the affected facial nerve 6,7,9,11,15,18,19) . Lesions distant to the CPA are very rare causes of HFS 1,3,5,14,17) .…”