Rare Case of Cerebellopontine Angle Glioependymal Cyst in a Pediatric Patient

Introduction: Ependymal cells are neuroglial cells that line the ventricular system and central canal of the spinal cord. Glioependymal cysts lined by ependymal cells are postulated to arise from ectopic rests of primitive neuroglial tissue. These cysts can occur anywhere along the neuraxis; however, the cerebellopontine angle is not a usual site for these. We present an unusual case of a glioependymal cyst in the cerebellopontine angle in an adolescent boy presenting with hearing loss and facial palsy.

Case: A 13-year-old boy presented to our tertiary neurotology clinic with progressive left-sided hearing loss for 1 year and 3 months of progressive left-sided facial weakness (House Brackmann IV). Otologic exam was unremarkable. MRI of the Brain and IACs identified a large extra-axial cystic septated mass measuring 5.1 × 3.6 × 4.3 cm at the left cerebellopontine angle involving the internal auditory canal with enhancement of the margins of the mass with posterior dural tail. Temporal bone CT showed the mass abutting the petrous portion of the temporal bone and the left internal auditory canal. Both studies noted significant mass effect on the fourth ventricle and pons. Differential diagnosis included cystic vestibular schwannoma and meningioma. He underwent a translabyrinthine approach for excision of the mass. Beyond the porus, the facial nerve was splayed in the substance of the mass and was unidentifiable. The trigeminal was found to be significantly compressed but remained intact. He had gross total removal of the mass which was comprised of several large cysts contained within a fibrous capsule. Intraoperative frozen sections were suggestive of a meningioma or schwannoma. Final pathology results confirmed the mass to be a glioependymal cyst composed of epithelioid and spindle cells around a cyst that stained positively for GFAP and S100.

Conclusion: The presentation of glioependymal cysts in the posterior fossa is rare, and their presentation in the pediatric population is exceptional. To our knowledge, there is only one case reported of a cerebellopontine angle glioependymal cyst occurring in an adolescent, and our case is the first presenting with facial paralysis. Although extremely rare, glioependymal cyst should be considered as a differential diagnosis in patients presenting with a cystic mass at the cerebellopontine angle.