Deciphering delirium through semantics: a selective synopsis.

During the course of the more than 2000 years of its recorded history, delirium has been given a very large number of different names, including phrenitis and paraphrenitis, mania and délire maniaque, (febrile, agitated, asthenic, lethargic, reversible toxic, symptomatic, exogenous) psychosis, inattention, acute and reversible dementia and insanity, amentia and sensorial phrenosis, reversible cognitive dysfunction, paralepsia, confusion and mental confusion, disorientation, dysergasia, and incoherence. Such a wide range of names with related definitions and pathogenic hypotheses not only bears witness to the interest that delirium has aroused in clinical investigators, but also reflects the difficulties in scientifically investigating its intrinsic nature. Furthermore, these difficulties have raised doubts about making a diagnosis that may explain why its incidence is reported to be under-estimated.