Neurosurgery notes/Other specialities/Neurology/Dementia/Lewy body dementia

Lewy body dementia

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Dementia
Lewy body dementia is an increasingly recognized 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.
  • Numbers
    • Up to 40% of patients with Alzheimer’s have Lewy bodies.
    • Two out of three are needed for diagnosis
Neuroleptics should be avoided in Lewy body dementia as patients are extremely sensitive and may develop irreversible Parkinsonism.
  • Clinical features
    • Progressive cognitive impairment
    • Parkinsonism
    • Visual hallucinations (often very vivid)
    • Other features such as delusions and non-visual hallucinations may also be seen
He also has a few supportive features of Lewy body dementia hallucinations in other modalities, delusions, depression and repeated falls.
  • Diagnosis
    • Clinical
    • SPECT, commercially knowsn as DaT scan
      • Sensitivity: around 90%
      • Specificity: 100%
    • Dopaminergic iodine-123-I FP-CIT is used as the radioisotope
Diagnosis is usually clinical, but SPECT is increasingly used. It is currently commercially known as a DaT scan. Dopaminergic iodine-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%. Currently, evidence best supports cholinesterase inhibitors in the treating of Lewy body dementia. It must be remembered that these patients have high sensitivity to neuroleptics so Olanzapine should not be used here.

Differential diagnosis

  • What are the main differentiating factors between Alzheimer and Lewy body dementia?
    • In Alzheimer disease, cortical neuritic plaques and neurofibrillary tangles are seen; early impairment in short-term memory is evident. It is more prevalent in women.
    • In Lewy body dementia, there is relatively preserved memory with impairments in executive functions; Parkinsonian and autonomic features are present. It is more prevalent in men.