LAUSR

A 54-year-old woman presented for evaluation of binocular vertical diplopia worse in downgaze. She had limited infraduction of the right eye in adduction and a right hypertropia worse in left gaze and right head tilt, consistent with a right trochlear nerve palsy. MRI brain revealed enlargement and enhancement of the right trochlear nerve in the subarachnoid space (figure). Laboratory testing and CSF analysis were normal. The imaging findings were stable over several years, suggesting the diagnosis of a trochlear nerve schwannoma.