[Pretectal syndrome caused by a plaque of multiple sclerosis].

We report a 20-year-old woman who presented with pretectal syndrome. She was well until September 12, 1991 when she noted an onset of difficulty in focusing her eyes. On neurologic examination, she showed convergence-retraction nystagmus and restriction of vertical eye movements more in the upward direction. A cranial CT scan revealed no abnormality. An oligoclonal band was detected in CSF. An MRI using Hitachi MRH-500 (0.5 T) revealed an abnormal high signal intensity lesion at the ventral area of the midbrain aqueduct, and another small lesion in the temporal white matter on the left. In addition, periventricular scattered small lesions were also visualized. Hydrocephalus, tumors and cerebrovascular disorders are common causes of pretectal syndrome, but multiple sclerosis is a rare one. Problems associated with the similar terminologies including Parinaud's syndrome, sylvian aqueduct syndrome or dorsal midbrain syndrome were discussed. According to Ranalli (1988), fibers mediating the upward gaze originate in the rostral interstitial MLF (riMLF), cross through the posterior commissure, and terminate in the contralateral oculomotor complex. On the other hand, downward gaze fibers take another route to the oculomotor complex. This may be a reason for the dissociation of the upward and downward gaze palsy, and the riMLF seems to be one of the most important structures responsible for the upward gaze.