The paramedian diencephalic syndrome: a dynamic phenomenon.

The paramedian diencephalic syndrome is characterized by a clinical triad: hypersomnolent apathy, amnesic syndrome, and impaired vertical gaze. We studied 4 cases with computed tomography evidence of bilateral diencephalic infarctions. Each case began abruptly with hypersomnolent apathy followed by fluctuations from appropriate affect, full orientation, and alertness to labile mood, confabulation, and apathy. Speech varied from hypophonia to normal; handwriting varied from legible script to gross scrawl. Psychological testing revealed poor learning and recall, with low performance scores. In 3 patients the predominant abnormality was in downward gaze.