Delirium, dementia, and other cognitive disorders

Abstract

Organic psychiatric disorders result from brain dys­function caused by organic pathology inside or outside the brain. Dementia is the most common condition, with Alzheimer’s disease alone affecting 1 per cent of the population at 60 years, rising to 40 per cent over 80 years. Many of the rarer organic psychiatric dis­orders tend to affect a wider age range, but present in similar ways. Given the changing demographics of most developed countries, disorders producing cognitive im­pairment in older adults are becoming increasingly important for provision of healthcare services and in daily clinical practice. This chapter will cover the more common causes of cognitive impairment, and there is additional information in Chapters 18 and 20 on psych­iatry of older adults in psychiatry and medicine. There are three common clinical presentations of or­ganic psychiatric disorders: … 1 Delirium— an acute generalized impairment of brain function, in which the most important feature is impairment of consciousness. The disturbance of brain function is generalized, and the primary cause is often outside the brain; for example, sepsis due to a urinary tract infection. 2 Dementia— chronic generalized impairment, in which the main clinical feature is global intellectual impairment. There are also changes in mood and behaviour. The brain dysfunction is generalized, and the primary cause is within the brain; for example, a degenerative condition such as Alzheimer’s disease. 3 Specific syndromes— which include disorders with a predominant impairment of isolated areas; for example, memory (amnesic syndrome), thought, mood, or personality change. These include neurological disorders that frequently result in organic psychological complications; for example, epilepsy…. Table 26.1 lists the main categories of psychiatric disorder associated with organic brain disease. The following sections describe these syndromes and the psychiatric consequences of a number of neurological conditions. Organic causes of other core psychiatric conditions (e.g. anxiety and psychosis) are covered in the relevant specific chapters. Delirium is characterized by an acute impairment of consciousness producing a generalized cognitive impairment. The word delirium is derived from the Latin, ‘lira’, which means to wander from the furrow. Delirium is a common condition, affecting up to 30 per cent of patients in general medical or surgical wards, with the primary cause often being a sys­temic illness. The term ‘acute confusional state’ is a synonym for delirium.