Updated 18 May 2015

Organic brain syndrome

This general term describes acute or chronic disorders which cause impaired mental function.


Description and incidence

This is a general term used to describe acute or chronic disorders which cause impaired mental function, but specifically excludes psychiatric disorders. Whilst organic brain syndrome (OBS) is common amongst elderly people, it is not considered a normal feature of ageing.


The hallmark symptoms of OBS are:

  • Memory impairment,
  • Confusion,
  • Decreased intellectual functions,
  • Judgement errors, and
  • Dementia with or without agitation.

There may be overlap with symptoms of psychological or psychiatric problems occurring with OBS, such as depression.


There are many individual possible causes, best grouped as follows:

  • Degenerative conditions such as
    • Alzheimer's
    • Parkinson's
    • Multiple sclerosis
  • Cardiovascular disorders such as
    • Rhythm disturbances
    • Stroke, TIA, infective endocarditis with emboli
    • Severe hypertension
    • Multi-infarct dementia - multiple strokes
  • Trauma
    • Brain haemorrhage
    • Concussion
  • Metabolic
    • Thyroid, kidney or liver disease
    • Vitamin deficiencies
    • Cancer
  • Respiratory - any condition causing oxygen deprivation
  • Infection - especially septicaemia
  • Toxic
    • Alcohol withdrawal, Korsakoff's syndrome
    • Drug withdrawal, especially benzodiazepines and steroids

Diagnostic tests

The clinical diagnosis of the condition is followed by tests to identify any possibly reversible cause.

Blood tests for infection, organ dysfunction (liver, kidney and thyroid tests) are indicated. A full cardiovascular examination and ECG will detect cardiac problems. Chest X-ray will be of use here, and may detect underlying lung disease as well.

Scans will identify pathology in the head, such as bleeding or blood clots.


This will vary according to the underlying cause found on testing. Often, no specific cause is found, so that supportive measures are all that can be offered, for instance retraining in memory techniques. Some patients become aggressive, and may need to be medicated to control this.


Most of the disorders causing OBS are not treatable, and tend to be progressive. Attention and support may need to be focused on the patient's caregivers as well.

(Dr A G Hall)

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