Internuclear ophthalmoplegia: MR-anatomic correlation.

Internuclear ophthalmoplegia is a gaze disorder characterized by impaired adduction on the side of a lesion involving the medial longitudinal fasciculus with dissociated nystagmus of the abducting eye. Eleven patients with internuclear ophthalmoplegia (nine with clinical multiple sclerosis, two with clinical infarction) underwent MR imaging with spin-echo techniques on a 1.5-T system. Nine patients also had CT. MR showed focal or nodular areas of high signal intensity on T2-weighted images in the region of the medial longitudinal fasciculus in 10 of 11 patients. In one of four patients with internuclear ophthalmoplegia who had MR after intravenous gadolinium-DTPA, an enhancing ring lesion was seen in the region of the medial longitudinal fasciculus on short TR/TE images, indicating active blood-brain-barrier disruption, which correlated with this patient's recent-onset internuclear ophthalmoplegia. CT failed to show the lesions in all nine patients examined. This report demonstrates the superiority of MR in evaluating gaze disorders attributable to brainstem dysfunction, such as internuclear ophthalmoplegia, and correlates MR findings with the relevant neuroanatomy of the medial longitudinal fasciculus.