FFinalistSouthampton · 2027
Neurology
AKT · Neurology/Movement & neurodegeneration

Lewy body dementia

Cortical α-synuclein (Lewy body) deposition

Overview

A dementia defined by the triad of FLUCTUATING cognition, recurrent VISUAL HALLUCINATIONS and spontaneous PARKINSONISM, with REM sleep behaviour disorder. Crucially, patients have severe SENSITIVITY to antipsychotics — a key safety point.

Recognise

  • Fluctuating cognition/attention, recurrent well-formed visual hallucinations, parkinsonism
  • REM sleep behaviour disorder (acting out dreams), autonomic dysfunction, recurrent falls
  • Dementia within ~1 year of parkinsonism (vs Parkinson disease dementia which comes years later)

Red flags

  • NEUROLEPTIC SENSITIVITY — antipsychotics can cause severe rigidity/irreversible deterioration; recurrent falls

Differentials & how to tell them apart

Alzheimer's diseaseamnesia-led, no early hallucinations/parkinsonism/fluctuation
Parkinson disease dementiadementia arises >1 year AFTER established parkinsonism (the "1-year rule")
Deliriumacute, identifiable precipitant — but fluctuation overlaps, so exclude it
Vascular dementiastepwise, vascular risk, focal signs

Investigations

Clinical (consensus criteria); DaTscan (reduced striatal dopamine uptake) supports it; MRI relatively preserves the hippocampus (vs AD).

Management

Cholinesterase inhibitor (rivastigmine/donepezil); AVOID antipsychotics

  1. 1Cholinesterase inhibitor for cognition and hallucinations; non-drug management of behaviour and falls.Gate: AVOID antipsychotics — neuroleptic sensitivity can cause severe, sometimes irreversible parkinsonism/deterioration; if unavoidable use low-dose quetiapine cautiously
  2. 2Cautious levodopa for disabling motor symptoms (can worsen hallucinations); treat REM sleep behaviour and autonomic symptoms.
Cholinesterase inhibitors (rivastigmine/donepezil) — help cognition AND hallucinations
AVOID antipsychotics — severe neuroleptic sensitivity; if essential, cautious quetiapine

Key points

Fluctuation + visual hallucinations + parkinsonism = Lewy body. The "1-year rule" separates it from Parkinson disease dementia. Antipsychotic sensitivity is the exam safety point.

Monitor & prognosis

Cognition, hallucinations, parkinsonism, falls, drug tolerance.

Progressive; faster decline than Alzheimer.

Source: NICE NG97 (dementia)