Abstract
We observed two patients with acute onset hypersomnia and memory disturbance who had unilateral infarction in the anteromedial thalamus.
The first case is a 62-year-old, right-handed woman, who showed hypersomnia and memory disturbance. CT scan revealed a small low density area in the right anteromedial thalamus, which involved the anterior, intralaminar, centromedian, ventral anterior, ventral lateral, and dorsomedial nuclei and mamillothalamic tract. Angiography showed no occlusion in the major cerebral arteries, except for stenosis and wall irregularity in the circummesencephalic portion of the right posterior cerebral artery.
The second case is a 68-year-old, right-handed man, who had been suffering from hypertension and diabetes mellitus for ten years. He showed hypersomnia, memory disturbance and dyscalculation. Other symptoms included Homer's syndrome and a mild weakness and dysesthesia in the right arm. CT scan revealed a small low density area in the left anteromedial thalamus. Angiography showed no stenosis or occlusion in the major cerebral arteries. In both cases hypersomnia disappeared two weeks after onset.
It can be postulated that the intralaminar, centromedian and dorsomedial nuclei which are related to the ascending reticular activating system could play a chief role of the occurence of hypersomnia. It is suggested that the thalamic lesion on either dominant or nondominant hemisphere could cause memory disturbance.
