Strangulation of the abducens nerve by an arachnoid band within an epidermoid cyst: illustrative case

BACKGROUND: Intracranial epidermoid cysts (ECs) are rare benign lesions of ectodermal origin that can be found in the cerebellopontine angle (CPA). If large enough, they compress surrounding structures, causing cranial neuropathies, cerebellar dysfunction, and hydrocephalus. OBSERVATIONS: In this case report, the authors present a patient with headaches and diplopia secondary to a CPA EC. The cyst had wrapped itself around and was strangulating the abducens nerve. This choking of the nerve was believed to have been the cause of the patient’s double vision. The arachnoid band was released with a myringotomy knife. LESSONS: Intracranial ECs typically cause symptoms from mass effect on surrounding structures; it is unusual for one to have choked off the nerve in the fashion presented in this case. Knowledge of the potential ways that ECs can affect nervous structures is critical for resecting them without injuring normal tissue.