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Probability diagnosis

Drugs: illicit or prescribed

Alcohol: acute or chronic


Febrile delirium

Affective (mood) disorders

Drug withdrawal inc. alcohol, hypnotics

Dementias esp. Lewy body disease

Serious disorders not to be missed


  • Cerebrovascular disease

  • Migraine (luminous)


  • Encephalitis/meningitis

  • Septicaemia

  • Any serious febrile illness


  • Cerebral tumours

  • Cancer treatment


  • Hypoxia

  • Liver failure

  • Metabolic/electrolyte imbalance

  • Dehydration

Pitfalls (often missed)

Major depression

Extreme fatigue

Vitamin deficiency esp. B group

Seizure disorders esp. complex partial


  • Narcolepsy

  • Post-concussion

  • Bereavement

  • Multiple sclerosis

Masquerades checklist



Drugs: iatrogenic/social–illicit

Thyroid/other endocrine: hypothyroid?

Urinary tract infection esp. elderly

Is the patient trying to tell me something?

Consider conversion disorder (hysteria); fabrication.

Key history

A careful history is required, esp. current history incl. general health, febrile illness, psychological issues, neurological features, nutrition and head injury. Elicit type of hallucination: auditory, visual, olfactory, tactile, hypnogogic or hypnopomic. Examine past, family and psychosocial history, as well as any history of cerebrovascular disease, diabetes, hypertension or migraine. Check thyroid symptoms, particularly for hypothyroidism. Also examine drug history: prescribed; OTC; alcohol; social esp. marijuana, opioids, amphetamines, LSD, petrol sniffing.

Key examination

  • General features: appearance of patient, vital signs

  • General respiratory, neurological and cardiovascular examination

  • Pulse oximetry

  • Mental state examination

Key investigations

First line:

  • urinalysis

  • blood glucose

  • FBE

  • U&E


  • LFTs (γGT)

  • ECG

  • KFTs

  • cerebral imaging

Diagnostic tips

Pay close attention to drugs use, esp. alcohol, caffeine, narcotics and illicit agents

Auditory hallucinations – incl. schizophrenia; depression; bereavement.

Visual: organic disease

Olfactory: complex partial seizures (temporal lobe)

Tactile: drugs (alcohol, opioids e.g. cocaine, amphetamines esp. ‘ice’)

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