Table 2

Red flags: clinical findings suggesting a diagnosis other than delirium or where a higher index of suspicion for alternative diagnoses is appropriate

Clinical finding (history or examination)Explanation
Evidence of self-neglectLonger prodrome of deterioration, not specific for aetiology
Change in sleepA potential red flag for affective or mixed psychiatric disorders, may also occur with autoimmune encephalitides such as Morvan’s syndrome
Recent travel history or immunosuppression including HIVBroadens the differential diagnosis for infective encephalitides 36 37
Checkpoint inhibitor use (programmed cell death protein-1, cytotoxic T lymphocyte antigen-4 or their corresponding ligandsEncephalitis has been described as part of the spectrum of autoimmune diseases these drugs can cause
AphasiaCommonly mistaken for confusion, and commonly occurs with herpes encephalitis, cortical strokes and acute demyelinating encephalomyelopathy
Brainstem/cerebellar signsThalamic damage can cause peduncular hallucinosis and fluctuating wakefulness
ParkinsonismDementia with Lewy bodies in particular causes fluctuations and visual hallucinations (silent people, animals)
MeningismSelf-explanatory
Automatisms, focal myoclonusFocal seizures (unlike generalised myoclonus which is in keeping with encephalopathy)
Facio-brachial seizures, catatoniaStrongly suggests particular autoimmune encephalitides
Petechial haemorrhagesAlong with acute derangements of blood tests indicative of other organ function, may indicate fat embolus from long bone or pelvic fractures (characteristic DWI MR brain changes)
AsterixisType 2 respiratory, renal or liver failure
Systemic signs of portal hypertensionLiver failure
Unusual affect, behaviour change suggesting auditory hallucinations, paranoiaUncontrolled psychotic symptoms in keeping with primary psychiatric disorder
Systemic signs of infective endocarditisRaises suspicion for an embolic cause