[Divergence paralysis due to a lesion of the lateral tegmentum of the midbrain caused by thalamic hemorrhage].

A 66-year-old diabetic and hypertensive man suddenly developed right hemiplegia. Examination revealed right hemiplegia including his face, vertical gaze palsy, and divergence paralysis. The cranial CT scan disclosed a left thalamic hemorrhage as large as 40 mm in diameter, which extended to the midbrain. He was treated medically and his divergence paralysis improved. But all other symptoms remained for the next 11 months and he eventually died of acute retroperitoneal hemorrhage. The autopsy revealed spongy state and gliosis extending from the left thalamic nuclei to the left midbrain. In the tegmentum, dorsolateral part around the left oculomotor nucleus was involved. The precise location of the human divergence center of the eyes is still unknown. According to previous reports, the divergence center may locate in the tegmentum of the midbrain or pons. Recently, animal experiments detected the neurons which fire for divergent in the mesencephalic reticular formation just dorsal and lateral to the oculomotor nuclei. Our case had a lesion of gliosis and spongy state, namely the old hematoma, in the same portion. Therefore, we considered that the human divergence center of the eyes might exist in the lateral tegmentum of the midbrain, just lateral and dorsal to the oculomotor nucleus.