Monocular elevation paresis caused by an oculomotor fascicular impairment.

A 54-year-old man developed an acquired monocular elevation paresis. Forced lid closure or oculocephalic reflexes failed to elevate the affected eye in contrast to the contralateral eye, which turned fully upward using either maneuver. A mass lesion compressing the lateral aspect of the right oculomotor nerve at the exit of the brainstem was found. The monocular elevation paresis in this patient reflects damage of the oculomotor nerve fascicles that supply the inferior oblique and superior rectus muscles. This case supports the accepted topographical fascicular arrangement of the oculomotor nerve, with the inferior oblique and superior rectus being the most lateral and caudal, and the pupilloconstrictor fibers and the inferior rectus being most medial and rostral.