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Organic mental disorders
Organic brain disorders result from structural pathology, as in dementia, or from disturbed central nervous system (CNS) function, as in fever-induced delirium. They do not include mental and behavioural disorders due to alcohol and misuse of drugs, which are classified separately.
- Delirium -
Delirium, also termed toxic confusional state and acute organic reaction , is an acute or subacute brain failure in which impairment of attention is accompanied by abnormalities of perception and mood. It is the most common psychosis seen in the general hospital. Ten to twenty per cent of surgical and medical inpatients have delirium during their admission. The degree of impairment classically fluctuates, so that there are intermittent lucid periods. Confusion is usually worse at night, with consequent sleep reversal, so that the patient is asleep in the day and awake all night. During the acute phase, thought and speech are incoherent, memory is impaired and misperceptions occur. Episodic visual hallucinations (or illusions) and persecutory delusions may occur. As a consequence, the patient may be frightened, suspicious, restless and uncooperative.
- Dementia -
Dementia is an acquired global impairment of intellect, memory and personality, but without impairment of consciousness. There is often an associated deterioration in emotional control, social behaviour and motivation. Dementia is used both to refer to the primary dementing illness, such as Alzheimer's disease, as well as the process itself, which may be secondary to some other disease (e.g. hypothyroidism). Presenile dementia is the term used for patients under 65 years of age and senile dementia for older patients. However, there is no clinical difference.
- Alzheimer's disease -
This is a primary degenerative brain disease of unknown aetiology that is insidious in onset, followed by gradual deterioration and death in about 10 years. The onset can be in middle adult life or even earlier, but the incidence is higher in later life. Patients particularly at risk of developing Alzheimer's disease are those who have a family history, who have sustained a head injury, or have Down's syndrome.
Organic amnestic (dysmnesic) syndrome
This is characterized by a marked impairment of memory occurring in clear consciousness and not as part of a delirium or dementia. Long-term memory is less affected than short-term memory. Often the patient is blandly unconcerned and commonly confabulates. One of the most common causes is severe thiamin deficiency secondary to chronic alcohol misuse (Korsakoff's syndrome).
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