Table 1

Key features of delirium and differential diagnoses to consider

Clinical featureMain source of informationCaveatsDifferential diagnoses to considerRecommendations
Acute onset (hours to days)Collateral history;
Ambulance records
Evidence of neglect
Not specific
Chronic, progressive cognitive prodrome may reflect undiagnosed dementia and raise likelihood of delirium
Acute cortical pathologies including encephalitides (infective and non-infective) and acute strokeAcute and longer histories both relevant
FluctuationsCollateral history
Direct observation
Nursing records
Changing environment and stress can transiently worsen consistent impairmentsDementia with Lewy bodies
Metabolic and drug-related causes
Cognitive impairmentDirect and collateral history
General and cognitive examinations
Delirium should affect multiple cognitive domains. Limited aphasia or amnesia with limbic encephalitis or focal presentationsAssess language comprehension and expression
Assess at least attention, orientation and recall
Formal bedside cognitive examination if deficits unclear
Visual hallucinationsDirect and collateral history; observationCommon in delirium but not specific to diagnosisDementia with Lewy bodies
Alcohol withdrawal
Psychosis typically causes auditory hallucinations
Hyperactivity, hypervigilance, agitation and aggressionDirect and collateral history and direct observationNot specificAlcohol withdrawal
Stimulating or mood-altering medications
Environmental factors (is the patient hot/cold/hungry/scared?)
Non-pharmacological strategies to prevent delirium are sensible for at-risk individuals and essential in individuals with delirium
Hypoactive features (sleepiness, stupor, coma)Direct and collateral history and direct observationNot specific
Sleep-wake cycle disturbance common in Alzheimer’s disease
Fatigue and somnolence common in depression
Obstructive sleep apnoea/obesity hypoventilation syndrome
Hyperammonaemia from medications or liver impairment
Sedating medications
Examine for asterixis
Check thyroid stimulating hormone
Consider an early morning blood gas and ammonia testing
Context: is this individual vulnerable to delirium?Collateral history
Ambulance records
GP records
Evidence of neglect
Intensive care unit admission
Recent surgery
Beware of previous falls as a marker of frailty as these patients may have unwitnessed seizures, chronic subdural, progressive neurology affecting gait
Dementia and delirium commonly coexist; preceding cognitive impairment may be undiagnosed
  • GP, general practitioner.