[Isolated oculomotor nerve palsy caused by mesencephalic hemorrhage].

A 62-year-old man with a history of diabetes mellitus, hypertension and liver damage has sudden diplopia on Nov. 4, 1992. Ocular movements of this right eye were normal, but his left eyelid was completely ptotic, and left pupil was dilated and nonreactive to light. In primary position, his left eye deviated outward, and could not move to any direction. He was diagnosed as having total oculomotor nerve palsy of the left side without any other neurological signs or symptoms; his consciousness level was alert and mental state was normal. The present case showed normal facial sensation, no facial palsy and no tongue deviation. Deep tendon reflexes were hypoactive bilaterally. Pyramidal tract sign, cerebellar sign, and gait disturbance were not observed. Superficial sensation of the extremity was normal. Brain CT scan revealed a small mesencephalic hemorrhage extending to the tegmentusm ventral to the cerebral aqueduct of the left side. Brain magnetic resonance imaging demonstrated a high-intensity area in the left oculomotor nucleus and its fascicles in the midbrain on T1- and T2-weighted image. The oculomotor nerve palsy of the left eye gradually improved, but mydriasis, adduction impairment and downward gaze palsy continued, and oculomotor nerve palsy of the left eye was compatible with so-called inferior branch palsy of the oculomotor nerve. Moreover, contralateral eye movements were normal except for mild upward gaze palsy. Oculomotor nerve palsy of this type was consistent with the syndrome of oculomotor nucleus described by Pierrot-Deseillingny in 1981. It was presumed that the superior rectus muscle is innervated by the contralateral oculomotor nerve nucleus in man as well as in animals.