Delirium

   Defined as acute brain failure, delirium means a reduced clarity of awareness of the environment caused by a medical condition or a substance. An important symptom of delirium* is loss of orientation: not really knowing where one is, what day it is, or who one is. It is primarily a clouded state of consciousness but may be associated with a narrowing or lowering of consciousness as well, in addition to visual hallucinations. The term was evidently introduced into medicine by the Roman writer Celsus (25 B.C.–A.D. 50) in the first century after Christ. Yet, for many years its use remained ambiguous and was often made co-terminous with madness, psychosis, or dementia. Nonetheless, in an era when infectious illnesses with high fevers were so common, delirium also acquired a core meaning of organically caused confusion and disorientation.

   According to Zbigniew J. Lipowski (1924–1997), a major student of delirium, the term is first used in English in the sixteenth century, where medical writers differentiate it from mania and melancholia—general terms for madness—as neither was associated with fever. The seventeenth-century physician Thomas Willis (1621–1675), in his Two Discourses Concerning the Soul of Brutes (published in 1672 and translated into English in 1683), said that delirium was not a disease in its own right but a symptom of various physical illnesses. In his account, Willis focused on disorientation and psychosis. In 1794, Erasmus Darwin (1731–1802; grandfather of Charles Darwin), in his Zoonomia, or the Laws of Organic Life, proposed that delirium was a sign of impaired consciousness—essentially the modern definition—and likened it to dreaming.

   In France, the term "délire" has tended to mean delusional disorder more than delirium, although it was a French sanatorium psychiatrist, Alexandre-Jacques-François Brierre de Boismont (1797–1881), who in 1845 introduced the phrase "acute delirium" (délire aigu) in the Mémoires of the Academy of Medicine. In 1851, Louis-Jean-François Delasiauve (1804–1893), who had just taken over the service of mental retardation and epilepsy at Bicêtre Hospital in Paris, proposed in the Annales de médecine the term "stupidity," or "mental confusion," for delirium: "Hallucinations and irrational fears are a consequence of stupidity, as are the shadows into which intelligence falls." Delasiauve * The "three Ds" help distinguish these concepts: in acute organic illness there is delirium, a consciousness disturbance; in a subacute disorder, such as alcoholism, there is dysmnesia, a disturbance of memory; in dementia, a chronic organic brain change, there is a deterioration of personality (Alzheimer’s disease [see DEMENTIA] is not primarily a disorder of memory, as is popularly thought). assigned the mental confusion of alcoholism or narcotics to "stupidity" (Semelaigne, Pionniers de la Psychatrie Française, I, 306). (In English, "mental confusion" is disorder of thought, whereas delirium is a disorder of consciousness.)

   In Germany, psychiatry professor Karl Bonhoeffer (1868–1948), then in Breslau, later in Berlin, made a fundamental contribution to delirium in 1909 by distinguishing in the Central Journal for Nervous Diseases and Psychiatry (Zentralblatt für Nervenheilkunde und Psychiatrie) between the "endogenous psychoses," including depression (see DEPRESSION: EMERGENCE: exogenous vs. endogenous), and the "exogenous psychoses" arising acutely from somatic disorders outside the brain. "Among such exogenous forms of reaction might be mentioned the deliria [die Delirien], and the occasional hallucinoses that occur in their context"; he went on to enumerate several others (p. 499). Yet, this insistence that delirium was a specific exogenous psychiatric reaction to organic illness sufficed to focus the entire field of psychiatry on exogenous versus endogenous sources of illness.

   The definition of delirium as a disturbance in levels of consciousness, a result of brain changes measured by electroencephalography (EEG), was begun in 1944 by John Romano (1908–1994) and George L. Engel, then in the departments of psychiatry and medicine at the University of Cincinnati (later they went to Rochester). In an article in Medical Clinics of North America in 1944 on "Physiologic and Psychologic Considerations of Delirium," they demonstrated that different levels of disturbance in brain function, as seen in EEG slowing, correspond to different levels of delirium. They wrote, "The close correlation between the electrical activity of the cortex and the basic disturbance in delirium, i.e. the alteration in the level of consciousness, provides convincing evidence that the psychologic symptoms are . . . the result of disturbances in higher cortical function" (p. 635).