[Bilateral ptosis, bilateral upgaze and adduction paresis, and monocular downgaze paresis from a mesencephalic infarction].

We report a 57-year-old man with an ischemic lesion in the midbrain. In the acute stage, he presented with bilateral ptosis and markedly limited extraocular motion except for bilateral abduction and downward motion of the right eye. The pupillary reaction to light of his left eye also was impaired. He was admitted to our hospital, and brain MRI showed a small infarction extending from the left paramedian to the median tegmentum of the midbrain. Three weeks after admission, the ptosis and limited extraocular right eye motion had resolved. The pupillary reaction and downward motion of the left eye normalized gradually within 3 weeks. Two months after admission, ptosis and the limited left eye adduction were partially resolved, but the markedly limited upgaze of the left eye had not changed. Initial neuro-ophthalmologic findings suggested involvement of the caudal part of the oculomotor nucleus and the left oculomotor nerve within the midbrain. The pattern of neuro-ophthalmologic impairment seen in our patient led us to conclude that the caudal oculomotor nucleus and medial part of the fascicular fibers of the left oculomotor nerve probably recovered first, after which recovery of the fascicular fibers progressed laterally. The results of serial MRI were consistent with this interpretation.