Lewy body dementia is an increasingly recognised cause of dementia, accounting for up to 20% of cases. The characteristic pathological feature is alpha-synuclein cytoplasmic inclusions (Lewy bodies) in the substantia nigra, paralimbic and neocortical areas.

The relationship between Parkinson's disease and Lewy body dementia is complicated, particularly as dementia is often seen in Parkinson's disease. Also, up to 40% of patients with Alzheimer's have Lewy bodies.


  • Incidence: 20.00 cases per 100,000 person-years
  • Peak incidence: 70+ years
  • Sex ratio: 1:1
Condition Relative
Lewy body dementia1
Parkinson's disease0.65
Frontotemporal lobar degeneration0.15
Multiple system atrophy0.03
<1 1-5 6+ 16+ 30+ 40+ 50+ 60+ 70+ 80+

Clinical features

  • progressive cognitive impairment
    • in contrast to Alzheimer's, early impairments in attention and executive function rather than just memory loss
    • cognition may be fluctuating, in contrast to other forms of dementia
    • usually develops before parkinsonism
  • parkinsonism
  • visual hallucinations (other features such as delusions and non-visual hallucinations may also be seen)


  • usually clinical
  • single-photon emission computed tomography (SPECT) is increasingly used. It is currently commercially known as a DaTscan. Dopaminergic iodine-123-radiolabelled 2-carbomethoxy-3-(4-iodophenyl)-N-(3-fluoropropyl) nortropane (123-I FP-CIT) is used as the radioisotope. The sensitivity of SPECT in diagnosing Lewy body dementia is around 90% with a specificity of 100%


  • both acetylcholinesterase inhibitors (e.g. donepezil, rivastigmine) and memantine can be used as they are in Alzheimer's. NICE have made detailed recommendations about what drugs to use at what stages. Please see the link for more details
  • neuroleptics should be avoided in Lewy body dementia as patients are extremely sensitive and may develop irreversible parkinsonism.