Internuclear ophthalmoplegia, prenuclear paresis of contralateral superior rectus, and bilateral ptosis.

A patient with infarction of the paramedian part of the lower midbrain on the right side is described, in whom internuclear ophthalmoplegia and bilateral ptosis were associated with limitation of elevation of the contralateral eye from paresis of the superior rectus. Supranuclear paresis was suggested by partial dissociation between phasic and tonic components of upward gaze. It is suggested that the right-sided lesion involved the rostral median longitudinal fasciculus before it reached the oculomotor nucleus, the central caudal nucleus medially situated in the lower end of the oculomotor nucleus, and the prenuclear fibres from the posterior commissure to the ipsilateral nucleus of the contralateral superior rectus. A supranuclear lesion may be suspected when there is a complex association of dysconjugate palsy of oculomotor muscles.