Table 2.

Causes of delirium especially likely to be missed

InsultPresentationHow to detect
Modest insults in context of vulnerable brainHypoactive, hyperactive or mixed deliriumCore features of delirium; presence of vulnerability factors (eg dementia, brain injury)
Non-convulsive statusEpisodic confusion with sudden onsetEEG; history of epilepsy; vigilance to motor symptoms
Alcohol withdrawal/delirium tremensHyperactive delirium; sympathetic activation (tachycardia, sweating etc); visual hallucinationsAlcohol history; abnormal LFTs/MCV
Wernicke’s encephalopathyCan occur in absence of alcohol withdrawal; ophthalmoplegia or ataxia might be presentCharacteristic MRI changes (diencephalic hyperintensities on T2-weighted MRI) specific but not sensitive; response to Pabrinex®
Benzodiazepine or other sedative withdrawalSimilar to alcohol withdrawalHistory of sedative abuse
Medication adverse effectsVery common precipitant. Can present as sedated, but delirium can take various forms. Visual hallucinations can be particularly common with anticholinergic drugsBe particularly vigilant for medications with anticholinergic effects and opiates
Recreational drug intoxicationDepends on actions of drug: nystagmus common, stimulants likely associated with sympathomimetic effects and hyperactive deliriumDrug screen, but will not detect novel psychoactive substances; collateral history
Constipation and/or faecal impactionMay be no overt symptoms; abdominal painNursing records of bowel movements; abdominal and PR examination; abdominal X-ray
Sleep deprivationHistory of sleep disorder (eg sleep apnoea)History of disturbed sleep; polysomnography (sleep study)
  • EEG = electroencephalography; LFTs = liver function tests; MCV = mean corpuscular volume; MRI = magnetic resonance imaging; PR = per rectal