Mental status examination

At a glance

• The mental state examination (MSE) is the psychiatric equivalent of the physical examination: a cross-sectional record of what you observe and elicit at one moment.
• On medical wards it answers three questions. Is this delirium (a medical emergency)? Is there a primary psychiatric syndrome? What is the risk to the patient or others?
• It doesn't replace history, collateral, a cognitive screen or a physical examination. Its findings guide investigations, Mental Health Act decisions, capacity assessments and treatment choice.

What each domain records

Domain	What to record	Abnormal findings worth naming
Appearance and behaviour	Grooming, hygiene, eye contact, rapport, psychomotor activity	Picking at the air, psychomotor retardation, agitation, catatonic posturing
Speech	Rate, volume, tone, quantity, fluency	Pressured (mania), poverty of speech (depression, negative symptoms), dysarthria (toxicity, stroke)
Mood and affect	Mood in the patient's words; affect observed	Flat, blunted, labile, incongruent, elevated
Thought form	How thoughts link	Flight of ideas, loosening of associations, tangentiality, circumstantiality, thought block, perseveration
Thought content	What the patient thinks about	Delusions (persecutory, grandiose, nihilistic), obsessions, suicidal or homicidal ideation
Perception	Hallucinations, illusions	Modality matters: visual and tactile suggest organic causes
Cognition	Level of consciousness, orientation, attention, memory	Inattention, fluctuating alertness, disorientation
Insight and judgement	Understanding of illness and need for care	Graded: full, partial or none

Pitfall: writing "thought disorder" as a finding. Name the specific abnormality (for example loosening of associations) and give a quote.

Reading an MSE step by step

1. Level of consciousness and attention first. If the patient is drowsy, fluctuates or can't attend, the rest of the MSE is unreliable and delirium is the working diagnosis. Screen with the 4AT (a score of 4 or more suggests delirium; pooled sensitivity about 88% and specificity about 88%, Tieges 2021). See delirium in older adults.
2. Perception and modality. Visual, tactile or olfactory hallucinations point to delirium, drug toxicity, alcohol withdrawal, seizures or Lewy body disease.
3. Look for a toxidrome. Pair the MSE with pupils, skin, temperature, bowel sounds, tone and reflexes.
4. Then a primary psychiatric pattern. Mood, thought form and content separate mania, depression and schizophrenia spectrum illness.
5. Risk and capacity. Every MSE ends with suicide, self-harm, violence and vulnerability, and with insight as it bears on the decision at hand.

Typical patterns

Feature	Delirium	Schizophrenia	Depression	Anticholinergic toxidrome
Onset	Hours to days	Weeks to months	Weeks	Hours after ingestion
Consciousness	Fluctuating	Clear	Clear	Fluctuating
Attention	Impaired	Usually intact	Reduced effort	Impaired
Hallucinations	Visual, vivid	Auditory, third person or commentary	Mood-congruent, if psychotic	Visual, "picking at the air"
Thought form	Disorganised, rambling	Loosening of associations	Slowed, poverty of thought	Mumbling, incoherent
Physical signs	Signs of the cause	Usually none	Psychomotor change	Mydriasis, dry flushed skin, urinary retention, tachycardia

For toxidromes in detail see anticholinergic toxidrome and serotonin syndrome.

Worked example

A 74-year-old man, day 3 after hip fracture fixation, "isn't himself". Night staff report he is shouting at people who aren't there.

A/B: Lying in bed, plucking at the sheets, poor eye contact, intermittently drowsy. Speech: Mumbling, reduced volume. Mood: "Fine". Affect: Labile. Thought form: Disorganised, loses the thread mid-sentence. Content: Believes nurses are stealing from him. Perception: Sees children in the corner of the room. Cognition: Oriented to person only; months backwards fails at October. Insight: Nil.

4AT, item by item: alertness clearly abnormal (drowsy during the assessment) 4; AMT4 (age, date of birth, place, year) with 2 or more errors 2; months backwards started but fewer than 7 correct 1; acute change or fluctuating course 4. Total 11. Had the drowsiness been mild (alert within 10 seconds of waking), alertness would score 0 and the total 7, still well above the threshold of 4.

Interpretation: fluctuating alertness, inattention and visual hallucinations make this delirium (mixed subtype), not late-onset psychosis: drowsiness and quiet mumbling are hypoactive features, while shouting at night and plucking at the sheets are hyperactive ones. The persecutory belief is a feature of the delirium. Next steps: search for the cause (urine retention, opioid and anticholinergic load, infection, hyponatraemia, alcohol withdrawal), non-drug management, and no antipsychotic unless distress or danger can't be managed otherwise.

Special situations

• Catatonia: mutism, stupor, posturing, waxy flexibility, negativism, echolalia. Score with the Bush-Francis Catatonia Rating Scale. Give a lorazepam challenge (1 to 2 mg IV or IM), stop antipsychotics, check CK and temperature for NMS, and look for medical causes such as encephalitis. ECT treats benzodiazepine-resistant or malignant catatonia (mood disorders).
• Depressive pseudodementia: poor effort, "I don't know" answers and prominent low mood, against the confabulation and lack of concern seen in dementia. See approach to memory disturbance.
• Intoxication and withdrawal: an MSE taken while intoxicated can't be used for a psychiatric diagnosis. Repeat it once sober. Alcohol withdrawal adds tremor, sweating and visual hallucinations (alcohol withdrawal).
• Culturally and linguistically diverse and Aboriginal and Torres Strait Islander patients: use a professional interpreter, not family. Involve an Aboriginal mental health worker or liaison officer. Spiritual experiences such as hearing a deceased relative may be culturally normal and aren't delusions or hallucinations on their own.

When the MSE changes management

• Delirium on the MSE means a medical work-up before any psychiatric label.
• Psychosis with risk and impaired capacity may meet criteria for detention under the state or territory Mental Health Act. Capacity and the Act are separate tests (self-harm and suicidal behaviour).
• Catatonia changes drug choice: benzodiazepines in, antipsychotics out.
• Psychotic features guide treatment (psychotic disorders). Risk findings decide observation level and follow-up.

Pitfalls

• Doing the MSE without checking attention, then labelling delirium as psychosis or depression.
• Treating hypoactive delirium as depression because the patient is quiet and withdrawn.
• Calling a culturally sanctioned belief a delusion.
• Assuming a patient with psychosis can't consent, or that a calm patient has no risk.
• Recording an MSE once and never repeating it. Delirium fluctuates, so a normal MSE at 10 am doesn't exclude it.