Why Cognitive Assessment Is a High-Yield OSCE Station
Cognitive impairment affects over 900,000 people in the UK and is a presenting feature in geriatric, psychiatric, A&E, and GP OSCE stations. You may be asked to perform a formal cognitive assessment, screen for delirium in a deteriorating patient, or differentiate acute from chronic cognitive decline. The examiner also marks how sensitively you introduce the assessment — patients with cognitive impairment often feel embarrassed or defensive.
Introducing the Assessment — Get This Right
How you introduce the assessment scores communication marks:
"I'd like to ask you some questions to get a sense of how your memory and thinking have been. Some of them might seem quite straightforward — please don't worry if you find some harder than others. There are no right or wrong answers."
Never say "I'm going to test your memory" or "This is a memory test" — patients find it threatening. Frame it as part of a routine assessment.
The MMSE — Mini Mental State Examination
The MMSE scores out of 30. Under 24 suggests cognitive impairment; under 10 is severe. It has five domains:
| Domain | Score | What to assess |
|---|---|---|
| Orientation | /10 | Year, season, month, date, day (5 points); Country, county, town, hospital, ward or floor (5 points) |
| Registration | /3 | Name 3 objects (apple, penny, table); ask patient to repeat them — 1 point each |
| Attention and calculation | /5 | Serial 7s: "100 minus 7" (100, 93, 86, 79, 72, 65) — 1 point per correct subtraction; OR spell WORLD backwards (DLROW) |
| Recall | /3 | Ask for the 3 objects named earlier — 1 point each |
| Language and visuospatial | /9 | Name 2 objects (pen, watch), repeat "No ifs, ands, or buts", 3-stage command, read and obey "CLOSE YOUR EYES", write a sentence, copy intersecting pentagons |
🧠 Mnemonic
ORARL — the five MMSE domains
O — Orientation (10 points)
R — Registration (3 points)
A — Attention and calculation (5 points)
R — Recall (3 points)
L — Language and visuospatial (9 points)
MMSE score interpretation:
- 27–30: normal
- 24–26: borderline / mild impairment
- 18–23: moderate impairment
- Under 18: severe impairment
💡 Tip
The MMSE is copyright protected in the UK and some trusts have moved to the MoCA or ACE-III instead. Know which your clinical placement uses. In an OSCE, state which tool you are using and why.
The MoCA — Montreal Cognitive Assessment
The MoCA is more sensitive than the MMSE for mild cognitive impairment, particularly in detecting early Alzheimer's and vascular dementia. It scores out of 30; under 26 is considered abnormal.
MoCA domains:
- Visuospatial and executive function (5): trail making, cube copy, clock drawing
- Naming (3): name a lion, rhinoceros, camel (from pictures)
- Memory (5): learn 5 words, recall at end
- Attention (6): digit span (forward and backward), sustained attention (tap on A), serial 7s
- Language (3): repeat two sentences, name as many words beginning with F in 1 minute (over 11 = normal)
- Abstraction (2): how are a train and a bicycle alike? (both transport)
- Delayed recall (5): the 5 words from memory domain
- Orientation (6): date, month, year, day, place, city
💎 Clinical Pearl
The MoCA clock drawing test is a particularly good screening tool. Ask the patient to draw a clock face showing 11:10. A normal clock has all numbers present and correctly placed, and both hands pointing to the correct positions. Errors in clock drawing strongly correlate with executive dysfunction.
Delirium Screening: The 4AT
The 4AT is a rapid delirium assessment tool validated for use at the bedside. It takes under 2 minutes.
| Item | Score |
|---|---|
| Alertness: abnormal drowsiness or agitation | 0 or 4 |
| AMT4 (Abbreviated Mental Test 4): age, date of birth, current year, current location — under 3/4 correct | 0, 1, or 2 |
| Attention: months of the year backwards — under 7 correct | 0, 1, or 2 |
| Acute change or fluctuating course: evidence of change in mental status from baseline | 0 or 4 |
Scoring: 4 or more = delirium likely; 1–3 = possible delirium or cognitive impairment; 0 = delirium unlikely (but does not exclude it).
Delirium vs Dementia — Differentiating in an OSCE
🧠 Mnemonic
AODA — the key differences between delirium and dementia
A — Acute vs insidious: delirium is acute (hours to days); dementia is chronic (months to years)
O — Orientation to time: delirium fluctuates dramatically; dementia is more stable
D — Duration: delirium is transient (days to weeks with treatment); dementia is progressive
A — Attention: delirium severely impairs attention (cannot follow commands); dementia relatively preserves attention early
| Feature | Delirium | Dementia |
|---|---|---|
| Onset | Acute (hours–days) | Insidious (months–years) |
| Course | Fluctuating (worse at night) | Slowly progressive |
| Attention | Severely impaired | Relatively preserved early |
| Consciousness | Impaired (drowsy or hyperalert) | Usually normal until late |
| Reversible | Yes, with treatment | No (though rate can be slowed) |
| Common causes | Infection, drugs, metabolic, pain | Alzheimer's, vascular, Lewy body |
⚠️ Red Flag
Delirium in an older patient is a medical emergency. Always look for an underlying cause — the most common in hospital are infection (especially UTI and pneumonia), dehydration, medication (opiates, sedatives, anticholinergics), urinary retention, constipation, and pain. Treat the cause, not the delirium.
Completing the Cognitive Assessment
- Collateral history from a carer or family member (often more informative than the patient's own account)
- Depression screen: PHQ-2 or GDS (depression mimics dementia — "pseudodementia")
- Examine: neurological (focal deficits, gait, tremor, rigidity — Parkinson's/Lewy body), thyroid (hypothyroidism)
- Bloods: FBC, U&E, LFTs, TFTs, B12, folate, calcium, glucose (reversible causes)
- Imaging: CT or MRI head if diagnosis unclear or atypical features
Frequently Asked Questions
"How do I introduce a cognitive assessment sensitively in an OSCE?"
Avoid saying "memory test" — patients find it threatening. Instead say: "I'd like to ask you some questions to get a sense of how your thinking and memory have been. Some might seem quite simple — please don't worry if some are harder. There are no wrong answers." This framing scores communication marks and puts the patient at ease.
"What is the difference between the MMSE and the MoCA?"
The MMSE (out of 30, normal 27–30) is a widely used screening tool but is less sensitive for mild cognitive impairment. The MoCA (out of 30, normal 26–30) is more sensitive, particularly for executive dysfunction, attention deficits, and early Alzheimer's or vascular dementia. The MoCA also includes a clock drawing task and trail making, which are better at detecting frontal lobe impairment.
"What are the key differences between delirium and dementia?"
The key distinguishing features are onset and time course: delirium is acute (hours to days), fluctuating, and reversible with treatment of the underlying cause. Dementia is insidious (months to years), slowly progressive, and irreversible. Attention is severely impaired in delirium but relatively preserved in early dementia. Always look for an underlying cause of delirium — infection, medication, metabolic disturbance, and pain are the most common.
"What is the 4AT and when do I use it?"
The 4AT is a validated rapid delirium screening tool that can be completed in under 2 minutes. It tests alertness, abbreviated mental test (4 items), attention (months backwards), and looks for evidence of acute change or fluctuation. A score of 4 or more indicates likely delirium. Use it whenever a patient appears acutely confused, drowsy, or agitated — particularly in elderly patients admitted to hospital.
"What reversible causes of cognitive impairment should I screen for?"
The key reversible causes are thyroid dysfunction (hypothyroidism causes reversible cognitive impairment), B12 and folate deficiency (subacute combined degeneration), depression (pseudodementia), dehydration and electrolyte imbalances (hyponatraemia, hypercalcaemia), medications (particularly anticholinergics, benzodiazepines, and opiates), subdural haematoma, normal pressure hydrocephalus (triad: gait, incontinence, cognitive decline), and infections (especially in elderly patients).
Related guides: [Mental State Examination OSCE](/blog/mental-state-examination-osce) · [Falls Assessment OSCE](/blog/falls-assessment-osce) · [Neurological History OSCE](/blog/neurological-history-osce)