Update on the neuropathogenesis of delirium.

Delirium has been considered a syndrome of generalized dysfunction of higher cortical functions due to its breadth of symptoms and associated diffuse slowing on electroencephalogram. Advances in neuropsychiatry have revealed differences between brain regions, including the hemispheres, which may underlie the constellation of symptoms among different psychiatric disorders. For example, different neural pathways are involved in major depression and obsessive-compulsive disorder, including lateralization to one or the other hemisphere. In this article the author proposes that delirium, too, involves particular neural pathways and that lateralization to the right may be relevant. Structural and functional neuroimaging reports and recent neuropsychological studies support this lateralization. Prefrontal cortices, anterior and right thalamus, and right basilar mesial temporoparietal cortex may play a significant role in subserving delirium symptoms and may be the 'final common pathway' for delirium from a variety of etiologies. The final common pathway may be responsible for certain 'core symptoms' (disorientation, cognitive deficits, sleep-wake cycle disturbance, disorganized thinking, and language abnormalities), while other symptoms (delusions, hallucinations, illusions, and affective lability) may occur depending on the etiology causing delirium. An imbalance in the cholinergic and dopaminergic neurotransmitter systems is most commonly implicated in causing delirium, and could both account for delirium symptoms and be consistent with the neuroanatomical pathways being implicated.