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Probability diagnosis

The 4 Ds:

  • dementia

  • delirium (look for cause)

  • depression

  • drugs: toxicity, withdrawal

Serious disorders not to be missed


  • CVAs

  • cardiac failure

  • arrhythmia

  • acute coronary syndromes


  • cerebral

  • cancer (e.g. lung)


  • septicaemia

  • HIV infection

  • infective endocarditis

Hypoglycaemia/diabetic ketoacidosis

Bipolar disorder/mania

Schizophrenia states


Subdural/extradural haematoma

Pitfalls (often missed)

Alcohol intoxication/withdrawal

Illicit drug withdrawal (e.g. amphetamines)

Fluid and electrolyte disturbances

Faecal impaction (elderly)

Urinary retention (elderly)


Pain syndromes (elderly)


  • postictal state

  • hypocalcaemia

  • kidney failure

  • hepatic failure

  • prion diseases (e.g. Creutzfeldt-Jakob disease)

Masquerades checklist


Diabetes (hypo and hyperglycaemia)

Drugs: iatrogenic/social illicit (see list)


Thyroid disorder (hypo and hyper)

Spinal dysfunction (severe pain in elderly)


Is the patient trying to tell me something?

Consider anxiety, depression, emotional deprivation or upset, change in environment, serious personal loss.

Key history

The basis of the history is an accurate account from relatives or witnesses about the patient’s behaviour. When communicating with the patient, speak slowly and simply, face them and maintain eye contact. Note the past history and recent psychosocial history, including recent bereavement, family upsets and changes in environment. Drug history is vital. Perform a mini mental status examination.

Key examination

  • Note the patient’s general demeanour, dress and physical characteristics

  • Check vital signs

  • Assess the patient’s ability to hear, speak, reason, obey commands, stand and walk

  • Look for features of alcohol abuse, Parkinson disease and hypothyroidism

  • Examine the neurological systems

  • Pulse oximetry (if available)

Key investigations

For delirious or demented patients of unknown cause consider:

  • MCU urine

  • blood culture


  • blood glucose

  • U&E, calcium and phosphate

  • B12 and folate, vitamin D

  • TFTs

  • LFTs

  • HIV test

  • arterial blood gases

  • CXR

  • cerebral CT scan.

Diagnostic tips

  • The cause may be single or multiple.

  • Psychiatric causes include panic disorder, mania, major depression and schizophrenia.

  • The key feature of dementia is impaired memory.

  • The two key features of delirium are disorganised thought and inattention.

  • Prescribed drugs that can cause antisocial behaviour: major and minor tranquilisers, anti-Parkinson, cardiogenic, corticosteroids.

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