Isolated trochlear palsy due to midbrain stroke.

Trochlear palsy from intra-axial lesions usually accompanies other neurological deficits, and isolated trochlear palsy due to midbrain stroke is extremely rare. We report two patients with isolated trochlear nerve palsy due to circumscribed dorsal midbrain strokes, one from infarction and the other from hemorrhage, which are located in the region of the trochlear nucleus or adjacent fascicle. Focal brain stem stroke should be considered as a rare cause of trochlear palsy even though there are no associated neurological deficits.