6 General adult psychiatry6.4 Emergency psychiatry
6.4.3 Differential diagnosis in psychiatric emergencies
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Written by Resident Doctor Committee · Published
Safety before diagnosis
Airway, breathing and circulation come before detailed psychiatric assessment, with temperature, pulse, blood pressure, respiratory rate, oxygen saturation and conscious level recorded.
Capillary glucose is checked promptly, because hypoglycaemia can cause agitation, confusion or unusual speech.
Reduced or fluctuating consciousness suggests a medical cause, even when the patient seems coherent between episodes.
When calls come at once, an acute life-threatening physical emergency in a psychiatric patient takes priority over urgent but less dangerous psychiatric or minor physical presentations.
Medical and psychiatric illness coexist: established schizophrenia does not explain away new delirium.
Time course
Time course | Suggests |
|---|---|
Varies hour to hour | Delirium or an active toxic or metabolic process |
Hours to a few days | Medical, drug-related or acute stress-related causes, though some psychiatric illnesses also begin rapidly |
Weeks to months | An evolving psychiatric disorder, while medical causes are still considered |
Collateral history, a review of every medicine started, stopped, increased or combined, and examination of neurological signs, pupils, tone, temperature, hydration and skin outweigh the reported symptoms.
Seizures and their mimics
Feature | Epileptic seizure | Dissociative (non-epileptic) attack |
|---|---|---|
Onset | Often abrupt | May be gradual |
Eyes | Often open | Closed during the attack |
Recovery | Post-ictal confusion and amnesia | Rapid return of alertness |
Tongue laceration along the side favours an epileptic seizure.
These are clues, not rules: the two can coexist, and video electroencephalogram (EEG) helps where doubt remains.
Epilepsy-related aggression is mostly post-ictal and resistive, following focal impaired awareness seizures: brief stereotyped altered awareness, automatisms and amnesia, then short-lived confusion.
Transient global amnesia is abrupt anterograde amnesia with a patchy retrograde gap in an alert person who keeps their identity, has no focal signs and recovers fully within 24 hours.
Organic causes mistaken for psychiatric illness
Dementia and delirium
Delirium is acute and fluctuating, with inattention.
Dementia beginning before 65 gives a steady progressive decline over months, with memory loss, behavioural change, a clear sensorium and preserved remote memory.
Catastrophic reaction is the sudden emotional outburst of a person with dementia or other acquired brain impairment faced with a task their impairment no longer allows.
Other organic mimics
Condition | Picture | Telling clue |
|---|---|---|
Wernicke's aphasia from a left temporal infarct in the dominant posterior superior temporal gyrus | Fluent speech with neologisms, poor comprehension, poor repetition | Often no weakness, so it is mistaken for psychosis |
Frontal lobe tumour | Slowly evolving personality change, disinhibition, apathy, unconcerned incontinence | Anosmia suggests an olfactory groove meningioma; morning headache, vomiting and papilloedema show raised intracranial pressure |
Syndrome of inappropriate antidiuretic hormone secretion | Confusion, nausea, falls | Low serum sodium, concentrated urine and high urine sodium in a euvolaemic patient; most often from SSRIs in older women within the first month |
Wernicke's encephalopathy
Thiamine deficiency in a poorly nourished drinker gives confusion, ataxia, ophthalmoplegia and nystagmus, but only a minority show the full triad.
Parenteral thiamine is given at once, without waiting for imaging or the full triad, because a glucose load before thiamine can worsen it.
Hypoglycaemia is still treated without delay.
Toxic syndromes
Syndrome | Trigger | Signs |
|---|---|---|
Neuroleptic malignant syndrome | Antipsychotic, especially parenteral haloperidol with dehydration or hot weather; or abrupt withdrawal of dopaminergic treatment in Parkinson's disease, with no neuroleptic given | Lead-pipe rigidity with normal or reduced reflexes, fever, labile blood pressure, very high creatine kinase; develops over days |
Serotonin syndrome | A serotonergic drug is added | Clonus and hyperreflexia worse in the legs, sweating, mydriasis, diarrhoea; often within hours |
Anticholinergic toxicity | Tricyclics, antihistamines, antiparkinsonian anticholinergics | Delirium, dilated pupils, dry flushed skin, urinary retention, reduced bowel sounds, tachycardia, hyperthermia |
Stimulant intoxication | Cocaine or amphetamine | Dilated pupils, tachycardia, hypertension, chest tightness, persecutory ideas; clears within hours |
Lithium toxicity | A thiazide diuretic reduces renal lithium clearance, and dehydration pushes the level higher still | Vomiting, diarrhoea, coarse tremor, ataxia, slurred speech |
In neuroleptic malignant syndrome and serotonin syndrome, the causative drug is stopped and urgent medical care obtained.
An unexplained febrile, rigid or clonic state is never treated as ordinary psychotic agitation.
Catatonia and stupor
Catatonia shows as mutism, immobility, staring, negativism, posturing and waxy flexibility, or purposeless excitement.
Malignant catatonia adds hyperthermia and autonomic instability and is hard to tell from neuroleptic malignant syndrome; recent dopamine antagonist exposure or dopaminergic withdrawal points to the latter.
A monitored lorazepam challenge, commonly 1 to 2 mg intravenously or intramuscularly, supports the diagnosis, but non-response does not exclude catatonia.
Malignant or persistent catatonia needs urgent specialist treatment, including electroconvulsive therapy (ECT).
Cause | Distinguishing picture |
|---|---|
Depressive stupor | Follows severe depression with early waking, guilt, nihilistic delusions and poor intake; awareness is preserved, so the eyes follow people; fluid refusal makes it urgent and ECT is often needed |
Schizophrenia | Posturing and mutism after weeks of first-rank symptoms, such as thought broadcast and third-person voices, in clear consciousness |
Anti-NMDA (N-methyl-D-aspartate) receptor encephalitis | Young woman with a viral-type prodrome, then anxiety, insomnia and paranoid ideas, then mutism, orofacial dyskinesia, seizures, catatonia and autonomic instability |
Autism spectrum disorder | Decline over weeks to months in adolescence or early adulthood, with slowing, freezing, dependence on prompts and posturing, often after a change of routine |
Anti-NMDA receptor encephalitis needs serum and cerebrospinal fluid antibodies and a search for an ovarian teratoma; extreme delta brush on EEG supports it, but its absence does not exclude it.
Agitation in public
Condition | Distinguishing features |
|---|---|
Mania | Greatly reduced need for sleep, high energy, grandiosity, reckless spending and flight of ideas over days; overactivity leaves no time to eat, causing weight loss |
Agitated depression | Pacing, hand-wringing, guilt out of proportion (possibly delusional), early waking, weight loss; more common in later life |
Panic attack | No trigger, peaks within minutes and is over within 20 minutes; palpitations, rapid breathing, tingling from low carbon dioxide, fear of dying |
Alcohol withdrawal delirium | Begins 2 to 4 days after the last drink; poor attention, disorientation, fluctuating course, coarse tremor, sweating, hallucinated insects |
Schizophrenia | First-rank symptoms such as thought insertion and running commentary after a prodrome of months, far exceeding the one month ICD-11 requires |
Antisocial (dissocial) personality disorder | Violence over minor frustration, calm lack of remorse, conduct problems from early adolescence, repeated offending, unstable work record |
Panic can resemble cardiopulmonary illness, so medical causes are still assessed.
Food refusal and starvation
Cause | Why the person does not eat |
|---|---|
Psychotic depression | Mood-congruent nihilistic or guilty delusions, with anhedonia, psychomotor retardation and early waking; life-threatening, and ECT is often considered |
Schizophrenia | A fixed persecutory belief that food is poisoned, with third-person voices and functional decline over months |
Obsessive-compulsive disorder | Contamination fear reaching beyond eating, with rituals such as bleaching tins and handwashing |
Anorexia nervosa | Deliberate restriction, laxative use, repeated weighing, and fear of fatness persisting at a very low body mass index; bradycardia and syncope make it a medical emergency |
The belief that food is poisoned is fixed in schizophrenia, whereas in obsessive-compulsive disorder the person recognises the contamination fear as senseless.
Reassessment and handover
A response to glucose, thiamine or lorazepam adds evidence without proving the full diagnosis.
Handover states the working diagnosis and its uncertainty, dangerous causes considered, outstanding investigations, treatment and response, monitoring, escalation criteria and who will review.