Isolated medial rectus paralysis caused by oculomotor dorsolateral nucleus infarction

Isolated internal rectus palsy secondary to midbrain infarction is extremely rare and mainly involves the internal rectus subnucleus of the oculomotor nerve. The subnucleus rectus motor neurons of the oculomotor nerve are composed of two independent regions, the dorsolateral nucleus and the ventral nucleus ventral. In the present case, a 44-year-old man developed isolated medial rectus palsy due to an oculomotor dorsolateral nucleus infarction. The presenting symptom was simple diplopia without other stroke manifestations. A 30-day follow-up visit was conducted, the symptom was alleviated completely. It was suggested that diplopia due to unilateral and isolated dorsolateral medial rectus nucleus paralysis may be the sole manifestation of midbrain infarction.