Delirium: a subcortical phenomenon?

Evoked potentials of 23 patients with chronic liver disease and delirium were compared with those of matched controls without delirium. Delirious subjects had significantly worse scores on the Mini-Mental State Exam and Trail Making Tests. Mean peak activity from computerized spectral analysis of the EEG was lower in delirious subjects than in nondelirious subjects (7.5 +/- 3.8 cycles per second (cps) and 9.5 +/- 3.2 cps, respectively). Mean auditory brainstem evoked potentials were abnormal in both groups, with delirious subjects showing a bimodal distribution of latency values and a greater proportion of abnormal values. Somatosensory evoked potentials were abnormal for delirious patients and normal for controls, and the differences were significant. The data suggest that the underlying pathophysiology of delirium may lie, at least in part, at the subcortical level.