Complete bilateral horizontal gaze paralysis disclosing multiple sclerosis

Two women presented with bilateral internuclear ophthalmoplegia evolving in a few days to complete bilateral horizontal gaze paralysis. Convergence an d vertical eye movements were normal. Cerebral MRI showed a few small white matter lesions in the lateral ventricle regions, and, at the brainstem lev el, a single, small, bilateral lesion affecting the posterior part of the m edial pontine tegmentum and responsible for the clinical syndrome. The cond ition gradually improved in both patients, following a similar progression as at the onset: improvement first involved the adduction movements in both eyes, whereas bilateral abduction paresis still persisted for a few weeks, before complete recovery of eye movements. Bilateral damage to the medial longitudinal fasciculus and subsequent lateral extent of damage to the regi on of the two abducens emerging fibres may explain the clinical findings. I n both cases, the cause was probably multiple sclerosis.