Dementia and delirium

Quick Overview

Dementia and delirium represent distinct but clinically overlapping cognitive syndromes requiring urgent differentiation. Delirium is an acute, fluctuating confusional state (medical emergency), while dementia is a chronic, progressive decline. The 4AT score enables rapid bedside differentiation, and NICE NG97 provides structured guidance on investigation, diagnosis, and pharmacological management of dementia subtypes.

Core Facts & Concepts

Delirium vs Dementia Key Features:

4AT Score (Delirium Screening):

• 0 = Delirium unlikely
• 1-3 = Possible cognitive impairment
• ≥4 = Probable delirium
• Components: Alertness (0-4), AMT4 (0-2), Attention (0-2), Acute change (0-4)

Reversible Causes of Dementia (Screen All):

• Vitamin B12/folate deficiency (<200 ng/L)
• Hypothyroidism (TSH >10 mU/L)
• Hypercalcaemia (>2.6 mmol/L)
• Normal pressure hydrocephalus (triad: dementia, gait apraxia, incontinence)
• Chronic subdural haematoma
• Depression ("pseudodementia")

Cognitive Assessment Tools:

• ACE-III: 100-point scale (≥88 = normal, <82 = impaired)
• MoCA: 30-point scale (≥26 = normal, sensitive to mild cognitive impairment)
• MMSE: 30-point scale (outdated, copyright issues)

Problem-Solving Approach

Step 1: Exclude Delirium First

1. Apply 4AT score at bedside (takes 2 minutes)
2. If ≥4: Investigate for underlying cause (sepsis, drugs, metabolic, hypoxia)
3. Manage delirium before assessing for dementia

Step 2: Confirm Dementia Diagnosis

1. Cognitive impairment affecting ≥2 domains (memory, language, executive, visuospatial)
2. Functional decline in ADLs
3. Duration >6 months
4. Not explained by delirium/psychiatric disorder

Step 3: Investigate Reversible Causes (NICE NG97)

• Bloods: FBC, U&E, LFTs, calcium, glucose, TSH, B12/folate
• Neuroimaging: MRI brain (or CT if contraindicated)
• Consider: HIV, syphilis serology if risk factors

Step 4: Subtype Classification

• Alzheimer's (60%): Gradual memory loss, temporal/hippocampal atrophy
• Vascular (20%): Stepwise decline, stroke history, white matter changes
• Lewy body (15%): Visual hallucinations, parkinsonism, fluctuating cognition
• Frontotemporal (5%): Personality change, disinhibition, frontal atrophy

🚩 Red Flags: Age <60, rapid progression (<2 years), focal neurology, headache, seizures → refer neurology urgently

Analysis Framework

Acetylcholinesterase Inhibitors (NICE NG97 Criteria):

When to Start Treatment (All Required):

1. Confirmed Alzheimer's/Lewy body dementia diagnosis
2. MMSE 10-26 (mild-moderate)
3. Specialist (memory clinic) initiation
4. Review at 3 months (continue if MMSE stable/improved AND functional benefit)

⚠️ Warning: Do NOT use antipsychotics routinely in dementia (↑ stroke risk, ↑ mortality). Reserve for severe distress/risk only.

Visual Aid

Delirium Precipitants Mnemonic:

📌 Remember: PINCH ME - Pain, Infection, Nutrition, Constipation, Hydration, Medication, Environment

Key Points Summary

✓ 4AT score ≥4 = probable delirium (medical emergency requiring urgent investigation)

✓ Dementia diagnosis requires: ≥2 cognitive domains affected + functional decline + >6 months duration

✓ Always screen reversible causes: B12, folate, TSH, calcium + MRI brain (NICE NG97 mandatory)

✓ Acetylcholinesterase inhibitors (donepezil/rivastigmine/galantamine): Start if Alzheimer's/Lewy body + MMSE 10-26 + specialist initiation

✓ Memantine: Reserved for moderate-severe Alzheimer's (MMSE <20) or intolerance to cholinesterase inhibitors

✓ Avoid antipsychotics in dementia unless severe distress/risk (↑ stroke, ↑ mortality)

✓ ACE-III >88 = normal, <82 = cognitive impairment (more sensitive than MMSE for mild cases)