Dementia following strokes in the mesencephalon and diencephalon.

Six patients had ischemic infarcts in the paramedian thalamic, subthalamic, and mesencephalic areas. In addition to ocular motility problems, ataxia, dysmetria, and mild pyramidal signs, there were consistent behavioral observations and neuropsychological findings. All of the patients had initial deficits in arousal, and gradually improved to normal wakefulness. When awake, all of the patients had impaired attention, mental control, and slowed verbal and motor responsiveness. They were apathetic, poorly motivated, and affect was flat or occasionally labile. All of the patients had a memory disorder characterized by anterograde and retrograde loss. One patient had significant language impairment. These deficits persisted in all but one patient who had a predominantly mesencephalic lesion. We believe the cluster of findings in these patients constitutes a characteristic syndrome of dementia related to paramedian mesencephalic and diencephalic infarcts. This syndrome bears close resemblance to that associated with some subcortical degenerative disorders such as progressive supranuclear palsy. In cases of paramedian mesencephalic and diencephalic infarcts, however, computed tomography and magnetic resonance imaging can delineate clinicoanatomic relationships that account for specific constituents of the syndrome.