[A case of partial fascicular oculomotor paresis]

We report a case of partial fascicular oculomotor paresis in a 22-year-old woman. The patient noticed sudden onset diplopia which had transiently occurred twice in the past two months for several hours. She also had left blepharoptosis. Neurological examination revealed left blepharoptosis and diplopia caused by paresis of the left inferior oblique and superior rectus muscles. No other focal neurological signs were detected. Laboratory data, CSF examinations, ABR, SEP and VEP studies were all normal. Brain MRI revealed a high-signal-intensity lesion of about 7 mm in diameter in the left paramedian area of the midbrain at superior colliculus level on T2-weighted images. Cerebral angiography showed no significant findings. The lesion was limited to the left oculomotor fascicles. Either demyelinating or vascular lesion might be responsible for her oculomotor paresis. The symptomatic differences between this and previously reported cases suggest that the topographical organization of the oculomotor fascicles for the superior rectus, levator palpebrae superioris, inferior oblique, medial rectus, and inferior rectus muscles and the sphincter muscles of the pupils consists of fibers that lie in a lateromedial order.