As early as in Hippocrates’ medical writings, clinical pictures of patients experiencing delirium were described . The syndrome we currently refer to as delirium was originally based on two distinct syndromes. A syndrome called Phrenitis, in which patients showed cognitive disturbances, exited and restless behaviour, with disruption of sleep, and a syndrome called Lethargus, in which patients were somnolent, apathetic, listless and showed slow mentation. Although it was known that Phrenitis could change into Lethargus, and vice versa, it was not until the late eighteenth century that both terms were displaced by the single term delirium. There is some uncertainty whether the word ‘delirium’ is derived from the Greek word ληρος, meaning empty drivel , or from the Latin word for disturbance of mind, deliratio . Even in ancient times it was known that the emergence of a delirium was a bad prognostic sign and often a herald of death, but the pathophysiology remained obscure. Based on meticulous observations of patients, the German psychiatrist Bonhoeffer reported in 1910 that the presence of the symptom clouding of consciousness could discriminate organic-psychiatric disorders from functional or endogenous psychiatric disorders . Furthermore, he postulated that toxic substances originating from disease processes in the body or brain might cause delirium. A theory that is remarkably similar to the present-day inflammatory delirium theory, in which cytokines produced by glia cells induce delirium . Engel and Romano in 1959 further elaborated on the delirium concept by describing the association between a reduced level of consciousness and the degree of slowing of the electro-encephalogram (EEG) . Combined with the finding that slowing of the EEG was associated with derangements of cerebral metabolism, this provided additional evidence that delirium should be regarded as a syndrome of cerebral insufficiency. Currently, delirium is the most frequently occurring organic-psychiatric syndrome in the general hospital. The incidence of delirium in the general hospital ranges from 5 to 32% , but in specific populations, such as older patients (aged 65 years or more) or patients in the intensive care unit (ICU), the incidence of delirium can be much higher.

W.J.G. Hoogendijk (Witte) , M.W. Hengeveld (Michiel) , R.C. van der Mast (Roos)
The studies were funded by the Department of Psychiatry, Erasmus MC, Rotterdam, The Netherlands.
Erasmus University Rotterdam
Erasmus MC: University Medical Center Rotterdam

Osse, R. J. (2013, November 6). Delirium after Cardiac Surgery in Older Patients : Predictors of occurrence and outcome. Retrieved from