Altered Mental State

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Definition: Any change in behaviour, emotion, memory, thought or speech content or conscious state.


Alterations in mental state can be florid such as a patient with delirium tremens or subtle such as forgetfulness.   It can be acute such as a diabetic experiencing hypoglycaemia or chronic such as Alzheimer’s Dementia.  The possibilities are broad but a systematic approach with a good history, physical exam and selective investigations usually yields a treatable cause.  Usually an organic cause should be rule out before a psychiatric one is considered unless if the patient has a history of mental illness and the mental state is consistent with previous reports.    When the patient is acutely disturbed often sedation is required to complete the assessment safely and quickly so that treatment can begin.


See Common Causes of All Emergency Presentations

  1. Toxic (Poisonings) – especially in the young, drug abuse or mental illness
  2. Infective – CNS infection or sepsis
  3. Metabolic – (see Metabolic Causes of Altered Mental State)
  4. Traumatic – CNS lesion (see Structural)
  5. Structural – Any cause of Raised Intracranial Pressure

Screening assessment

  1. BSL for hypoglycaemia
  2. Observed drug paraphernalia, needle marks, empty pill packets
  3. History of drug abuse or mental illness
  4. Toxic exposure
  5. History of head trauma
  6. Fever, WCC, CRP +/- Septic Screen
  7. Electrolytes, Renal Function, Liver function, Blood gas
  8. Full neurological exam (CT brain if evidence of significant head trauma or no other cause found)

See Differentiating Organic from Psychiatric Conditions

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