title: Isolated trochlear nerve palsy secondary to a juvenile pilocytic astrocytoma.
abstract: A 9-year-old female developed a fourth nerve palsy which was the first sign of a posterior fossa astrocytoma. The fourth nerve palsy was believed to have resulted from direct invasion of the trochlear nerve rather than compression by hydrocephalus. Sagittal reconstruction of a computed tomogram revealed extension of the tumor into the dorsal midbrain where the trochlear nerve exits.
mesh_terms: D001254:Astrocytoma / Q000150:complications / Q000175:diagnosis* / Q000601:surgery; D001932:Brain Neoplasms / Q000150:complications / Q000175:diagnosis* / Q000601:surgery; D002531:Cerebellum; D002648:Child; D004172:Diplopia / Q000209:etiology; D005260:Female; D006801:Humans; D009886:Ophthalmoplegia / Q000175:diagnosis / Q000209:etiology*; D014057:Tomography, X-Ray Computed; D014321:Trochlear Nerve