Clinical features

Organic cerebral disorders in which the whole brain is affected usually present with cognitive impairment and/or clouding of consciousness, which may be accompanied by neurological symptoms or signs. The classical picture in acute cases is called delirium and in chronic cases dementia. Localized lesions give rise to focal impairments. Delirium, dementia, and focal syndromes are described below.

Less typical presentations include mood change, lability of mood, paranoid ideation, and changes in behaviour or personality. Organic cases may present with neurotic or psychotic symptoms resembling those found in 'functional' disorders, but often showing atypical features such as fluctuating symptomatology, visual hallucinations, vague or transient paranoid delusions, or first onset of neurotic symptoms in middle or old age. Cognitive testing may reveal unsuspected defects.

The symptom pattern depends more on the time course of the illness, and the part of the brain involved, than on the type of underlying pathology. Therefore, for example, a confusional state due to fever generally resembles, in its psychiatric aspects, confusion due to, say, renal failure.

Clinical features may also be modified by the patient's premorbid personality, premorbid vulnerability to psychiatric disorder, past life experience, current medication, and social circumstances.

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