[Midbrain hemorrhage presenting with trochlear nerve palsy--a case report].

A case of midbrain hemorrhage with isolated trochlear nerve palsy was reported. A 70-year-old female noticed vertical diplopia of insidious onset. Ouclar motility was normal. But her diplopia increased with right head tilt and in the left downward gaze, and disappeared with left head tilt. She had no other neurological symptoms and signs. CT scan revealed high density spot in the left tectum of lower midbrain. This lesion decreased over months but small high density spot existed five months later, which means calcified lesion, probably vascular anomaly. This is the first stroke case of trochlear nerve palsy without other neurological symptoms and signs. The first reason this patient showed isolated trochlear nerve palsy is that hematoma was small. The second is that hematoma developed slowly.