๐ง Dementia with Lewy Bodies (DLB) is the second most common form of degenerative dementia after Alzheimerโs disease.
It is clinically important because it combines cognitive decline with parkinsonism, vivid hallucinations, and sleep disturbance, and patients are uniquely sensitive to antipsychotics.
Histologically, a Lewy neuritis in the CA2 region of the hippocampus may be a distinctive feature of DLB.
๐ About
- Progressive neurodegenerative disorder characterised by dementia plus parkinsonian features.
- Distinct from Parkinsonโs disease dementia (PDD) mainly by timing: in DLB, cognitive impairment appears before or within 1 year of motor symptoms (โ1-year ruleโ).
- Accounts for 10โ15% of dementia cases; more common in older adults (70+).
- Response to L-dopa is often limited, and neuroleptic sensitivity is a diagnostic red flag.
๐งฌ Aetiology & Pathology
- Caused by abnormal deposition of alpha-synuclein (Lewy bodies) in cortical and subcortical neurons.
- Lewy bodies contain proteins such as ubiquitin, parkin, and ฮฑ-synuclein.
- Often coexists with Alzheimerโs pathology (amyloid plaques and tau tangles) โ โmixed dementiaโ.
- Disruption of dopaminergic and cholinergic neurotransmission explains both parkinsonism and cognitive/psychiatric symptoms.
๐ Clinical Features (Core)
- Fluctuating cognition: Episodes of confusion, reduced attention, or staring spells, alternating with near-normal lucidity.
- Visual hallucinations: Typically well-formed, vivid, and detailed (e.g., people, animals, children).
- Parkinsonism: Symmetrical bradykinesia, rigidity, shuffling gait; tremor less prominent than in idiopathic PD.
- REM Sleep Behaviour Disorder (RBD): Acting out dreams due to loss of REM atonia; may precede dementia by years.
โจ Supportive Features
- Delusions (often paranoid or bizarre).
- Neuroleptic sensitivity: severe extrapyramidal worsening with standard antipsychotics.
- Autonomic dysfunction: orthostatic hypotension, constipation, urinary incontinence.
- Depression and apathy are common comorbidities.
๐งช Investigations
- Blood tests: FBC, U&E, LFT, TFT, B12, folate โ exclude reversible causes of cognitive impairment.
- MRI/CT: Often non-specific; may show generalised atrophy but hippocampi are relatively spared compared to Alzheimerโs.
- DaTSCAN (dopamine transporter SPECT): Reduced uptake in basal ganglia supports a diagnosis of DLB vs Alzheimerโs. DaTSCAN can be used when diagnostic uncertainty remains. It shows reduced dopamine transporter uptake in the basal ganglia, supporting a diagnosis of DLB compared to Alzheimerโs, but it is not required if the clinical features are clear.
- Sleep study: Polysomnography can confirm REM sleep behaviour disorder.
๐ Differentials
- Idiopathic Parkinsonโs Disease: Dementia appears later (>1 year after motor symptoms).
- Alzheimerโs Disease: Memory impairment earlier and more dominant; hallucinations/parkinsonism not core early features.
- Vascular Dementia: Stepwise decline with vascular risk factors; imaging shows infarcts or white matter changes.
๐ Management
- Cognitive symptoms & hallucinations: Cholinesterase inhibitors (e.g., rivastigmine, donepezil) are first-line and may also reduce hallucinations.
- Parkinsonism: L-dopa can be tried but usually with modest benefit; monitor for worsening hallucinations.
- Psychosis: Avoid typical antipsychotics; if needed, use low-dose quetiapine or clozapine under specialist supervision.
- REM Sleep Behaviour Disorder: Clonazepam or melatonin at night.
- Depression: SSRIs (e.g., sertraline, citalopram) are preferred.
- Supportive Care: Carer education, multidisciplinary input (neurology, psychiatry, geriatrics), occupational therapy, and social support.
๐ Key Clinical Pearls
- Always ask about visual hallucinations โ they are a core differentiator from Alzheimerโs.
- Antipsychotic sensitivity can be life-threatening (rigidity, neuroleptic malignant-like syndrome).
- Look for RBD โ it can be an early marker of alpha-synucleinopathies (DLB, Parkinsonโs, MSA).
- Cognitive fluctuations are often mistaken for delirium โ careful history is essential.
๐ References
