Isolated midbrain neurocysticercosis presenting as trochlear nerve palsy

Neurocysticercosis (NCC) is a neurological infection caused by the larval stage of the tapeworm Taenia solium. It can be found in the brain parenchyma or in the intraventricular and subarachnoid spaces and the spinal cord, giving rise to different clinical manifestations and prognoses. Isolated brainstem NCC is rare, with few cases reported in the literature. We describe a case of isolated NCC in the midbrain. The clinical presentation, diagnostic approach, and surgical management with histopathological confirmation are reported.

A 33-year-old male presented to the emergency department with a 1-month history of increased diplopia during the vertical gaze. Neurological examination revealed a positive Bielschowsky's head tilt test, consistent with a right trochlear nerve palsy. Magnetic resonance imaging of the head revealed a cystic lesion in the left midbrain. The patient underwent a suboccipital craniotomy with a telovelar approach, and gross total resection of the lesion was achieved. Histopathological analysis revealed a brainstem cysticercus. Following surgery, the patient received albendazole and steroids. Conjugate eye movements were recovered during the 1-year follow-up period.

This case report highlights the importance of considering NCC as a differential diagnosis for cystic lesions of the brain, even when they are found in atypical locations. Surgical excision should be considered in cases with mass effect or uncertain diagnosis.