Makindo Medical Notes

🧠 Dementia with Lewy Bodies (DLB) is the second most common form of degenerative dementia after Alzheimer’s 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.

📖 About

• Progressive neurodegenerative disorder characterised by dementia plus parkinsonian features.
• Distinct from Parkinson’s disease dementia (PDD) mainly by timing: in DLB, cognitive impairment appears before or within 1 year of motor symptoms (“1-year rule”).
• Accounts for 10–15% of dementia cases; more common in older adults (70+).
• Response to L-dopa is often limited, and neuroleptic sensitivity is a diagnostic red flag.

🧬 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 α-synuclein.
• Often coexists with Alzheimer’s pathology (amyloid plaques and tau tangles) → “mixed dementia”.
• Disruption of dopaminergic and cholinergic neurotransmission explains both parkinsonism and cognitive/psychiatric symptoms.

🔎 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.

✨ 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.

🧪 Investigations

• Blood tests: FBC, U&E, LFT, TFT, B12, folate – exclude reversible causes of cognitive impairment.
• MRI/CT: Often non-specific; may show generalised atrophy but hippocampi are relatively spared compared to Alzheimer’s.
• DaTSCAN (dopamine transporter SPECT): Reduced uptake in basal ganglia supports a diagnosis of DLB vs Alzheimer’s. 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 Alzheimer’s, but it is not required if the clinical features are clear.
• Sleep study: Polysomnography can confirm REM sleep behaviour disorder.

📋 Differentials

• Idiopathic Parkinson’s Disease: Dementia appears later (>1 year after motor symptoms).
• Alzheimer’s 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.

💊 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.

📌 Key Clinical Pearls

• Always ask about visual hallucinations – they are a core differentiator from Alzheimer’s.
• Antipsychotic sensitivity can be life-threatening (rigidity, neuroleptic malignant-like syndrome).
• Look for RBD – it can be an early marker of alpha-synucleinopathies (DLB, Parkinson’s, MSA).
• Cognitive fluctuations are often mistaken for delirium – careful history is essential.

📚 References

• NICE NG97: Dementia: assessment, management and support
• Alzheimer’s Society – Dementia with Lewy Bodies
• McKeith IG et al. Diagnosis and management of DLB, Lancet Neurology 2017