Definitions & spectrum

• Dementia with Lewy Bodies (DLB): cognitive impairment precedes or occurs within one year of parkinsonism.
• Parkinson’s Disease Dementia (PDD): dementia developing in the context of established Parkinson’s disease, typically after one year of motor symptoms.
• Mild vs Major: Mild LBD (mild NCD) involves cognitive changes with preserved independence using compensatory strategies; Major LBD (major NCD) causes marked interference with daily activities and independence.

Core clinical features

• Cognitive fluctuation: pronounced variations in attention and alertness across hours or days.
• Recurrent visual hallucinations: well-formed, detailed, often of people or animals.
• Parkinsonism: bradykinesia, rigidity, postural instability often accompanied by early gait disturbance.
• REM sleep behaviour disorder (RBD): acting out dreaming, vivid dreams.
• Autonomic dysfunction: orthostatic hypotension, constipation, urinary symptoms, hypersalivation.

Other supportive features

• Severe sensitivity to antipsychotic medications causing worsening parkinsonism or neuroleptic malignant-like reactions.
• Visuospatial impairment and executive dysfunction early in the course.
• Relative sparing of episodic memory in earlier stages compared with Alzheimer’s disease.

Assessment — practical approach

1. Detailed history emphasising fluctuation, hallucinations, RBD, and timeline of motor vs cognitive symptoms; obtain collateral from caregivers.
2. Use cognitive screening tools but add assessments sensitive to attention, visuospatial function and executive skills (MoCA, ACE‑III, bedside visual perception tests).
3. Assess for autonomic features, gait and parkinsonian signs on neurological exam.
4. Medication review — anticholinergics, dopamine blockers and sedatives can worsen symptoms.
5. Consider polysomnography for suspected RBD and neuropsychological testing for detailed profiling.

Investigations

• MRI brain to exclude alternative causes (vascular lesions, normal-pressure hydrocephalus); often shows less medial temporal atrophy than AD.
• DaT-SPECT (dopamine transporter scan) to demonstrate nigrostriatal degeneration supporting LBD diagnosis when available.
• FDG-PET may show occipital hypometabolism (supportive).
• EEG can show fluctuations in background activity correlating with cognitive fluctuation.

Differential diagnosis

• Alzheimer’s disease — more prominent early memory impairment and different progression.
• Parkinson’s disease without dementia — motor symptoms without significant cognitive decline.
• Delirium and medication-induced cognitive changes — identify acute contributors.
• Posterior cortical atrophy and vascular cognitive impairment — consider imaging and vascular risk profile.

Management principles

Management balances cognitive and motor symptom control, minimising medication sensitivities, and treating neuropsychiatric and autonomic features, while prioritising safety and caregiver support.

Cognitive symptoms

• Cholinesterase inhibitors (rivastigmine preferred evidence base) can improve cognition, attention and hallucinations in LBD.
• Monitor for side effects: gastrointestinal upset, bradycardia.

Motor symptoms

• Levodopa can improve parkinsonism but may worsen hallucinations or psychosis — use lowest effective dose and monitor closely.
• Non-pharmacological physiotherapy for gait and balance; fall prevention strategies essential.

Neuropsychiatric symptoms

• Non-pharmacological first — reorientation, lighting, sleep hygiene and caregiver strategies.
• If antipsychotics required for severe distress or safety risk, use quetiapine or clozapine with extreme caution and specialist input — avoid typical antipsychotics (haloperidol) due to severe sensitivity.
• Melatonin or clonazepam for RBD (clonazepam with caution in frail elders).

Autonomic and other supportive care

• Orthostatic hypotension: fluid optimisation, compression stockings, fludrocortisone or midodrine when indicated.
• Constipation and urinary symptoms managed proactively.
• Advance care planning, driving advice, and caregiver education about fluctuations and hallucinations.

Key takeaways

• LBD presents with fluctuating cognition, visual hallucinations, REM sleep behaviour disorder and parkinsonism—recognition is key to management.
• Rivastigmine is evidence-backed for cognitive and neuropsychiatric symptoms; levodopa can help motor signs but requires close monitoring.
• Avoid or use antipsychotics with extreme caution due to severe sensitivity; prioritise non-pharmacological strategies and safety planning.
• Multidisciplinary care and caregiver education improve outcomes and reduce risks from fluctuations and autonomic dysfunction.