Abstract
Delirium, an acute confusional state characterized by decline in attention and cognition, is a common, life-threatening, but potentially preventable clinical syndrome among older persons. Deficits in cholinergic function have been postulated to cause delirium and cognitive decline. In particular, an imbalance between levels of acetylcholine and monoamine (such as dopamine) may cause delirium. We describe two cases of delirium in hospitalized older patients, supporting the "cholinergic deficiency hypothesis". In the first patient, hypo-reactive delirium developed a few hours after a dose of the long-acting opiate tramadol (a drug with anticholinergic effect) as analgesic for pain related to advanced peripheral artery disease. In the second patient, with vascular parkinsonism plus pre-frontal cortex vascular lesions, hyper-reactive delirium developed a few hours after a prescribed administration of L-dopa. These symptoms disappeared completely on the following day. These two "natural" experiments support the hypothesis that both hypo-reactive and hyper-active delirium may be caused by a reduction in cholinergic signaling.