Delirium

Delirium is a derangement of mental function characterized by disturbance of consciousness and impairment of cognition. In contrast to dementia, delirium usually develops over a short period of time, it tends to fluctuate in severity over the course of the day, and it usually resolves with treatment of the underlying causes. This disturbance of consciousness results in reduced awareness of the external environment, and a reduction of the ability to focus, sustain, and shift attention. Cognitive impairments in delirium include disorientation in time and place, memory deficits, and language disturbances. Sensory perception, particularly vision, may also be disturbed, resulting in misinterpretations, illusions, and hallucinations. There may be disruption of the normal sleep-wake cycle, with individuals being drowsy during the day and active at night. The acute mental disturbances of delirium can be very frightening and upsetting for patients, who may respond with agitated and aggressive behavior. In younger adults, an episode of delirium is usually quite dramatic and florid (hyperactive delirium), and its detection and diagnosis is relatively straightforward. By contrast, the mental disturbances in elderly individuals with delirium are often much less obvious, particularly if there is a pre-existing dementia (hypoactive delirium). As a result, it is quite common for delirium in an elderly person to be overlooked by their families, by other carers, and by medical and nursing staff. This is unfortunate because, like pain and fever, delirium is an important nonspecific sign that the patient is physically ill, and requires further investigation to identify the cause. If the individual is very demented or very ill, they may be unable to complain of other symptoms, and delirium may be the first or only sign that something significant is amiss.