Dementia with Lewy Bodies

What Dementia with Lewy Bodies is

Dementia with Lewy Bodies is a neurodegenerative disorder characterised by the build-up of Lewy bodies (intraneuronal aggregates of alpha-synuclein) in the brainstem, limbic regions, and neocortex. It overlaps clinically and pathologically with Parkinson's Disease. The convention is to call it Dementia with Lewy Bodies (DLB) when cognitive symptoms appear before or within a year of motor symptoms, and Parkinson's Disease Dementia when motor symptoms have been present for more than a year before cognitive impairment.

Dementia with Lewy Bodies accounts for around 5 to 10 per cent of dementia in older adults, although autopsy studies suggest it is somewhat under-diagnosed in life.

The four core clinical features

The 2017 consensus criteria identify four core clinical features. The presence of two or more, in a person with progressive cognitive decline, makes "probable" Dementia with Lewy Bodies likely.

1. Fluctuating cognition, with marked variation in attention and alertness over days, hours or even within a single conversation.
2. Recurrent visual hallucinations, typically well-formed and detailed (often people, animals or children).
3. REM Sleep Behaviour Disorder, in which dreams are acted out, sometimes with shouting or violent movements; this can pre-date cognitive symptoms by many years.
4. Parkinsonian features, including bradykinesia, rest tremor, rigidity or postural instability.

Supportive features

Additional supportive features include severe sensitivity to antipsychotic medication, autonomic dysfunction (postural drops in blood pressure, constipation, urinary incontinence, syncope, hyposmia), repeated falls, sleep disturbance, depression, anxiety, and apathy.

Cognitive profile

The cognitive picture differs from Alzheimer's Disease. Memory may be relatively preserved early. The prominent deficits are usually in attention, executive function, and visuospatial skill. Clock drawing and intersecting pentagon copying can be markedly impaired. Performance can change noticeably between assessments because of fluctuation.

How it is diagnosed

Diagnosis is primarily clinical, supported by:

• Structured cognitive testing (Addenbrooke's Cognitive Examination (ACE-III)), with attention to attention, fluency and visuospatial scores;
• A structural Magnetic Resonance Imaging brain scan, which is often relatively unremarkable, with preserved medial temporal lobes (helping distinguish from Alzheimer's Disease);
• A DAT Scan (123I-FP-CIT SPECT) when uncertainty remains. A reduced dopamine transporter signal in the basal ganglia is highly supportive. NICE NG97 1.2.20 recommends DAT Scan in uncertain cases;
• 123I-MIBG cardiac scintigraphy, where DAT Scan is not available;
• Polysomnography (sleep study) when REM Sleep Behaviour Disorder is suspected but unclear.

How it is treated

Cognitive symptoms

Cholinesterase Inhibitors, particularly Rivastigmine and Donepezil, can produce meaningful improvements in attention, hallucinations and global function in Dementia with Lewy Bodies, often more so than in Alzheimer's Disease. They are recommended where tolerated. Memantine may help in moderate to severe stages.

Hallucinations and behaviour

The non-pharmacological approach is preferred first. Identifying triggers, optimising vision and lighting, treating any underlying infection or constipation, and maintaining a calm and consistent environment can substantially reduce hallucination frequency.

Where pharmacological treatment is needed, antipsychotic prescribing must be approached with caution. Typical antipsychotics (such as Haloperidol) are contraindicated in Dementia with Lewy Bodies and can precipitate severe sensitivity reactions. If antipsychotic medication is essential, an atypical agent (such as Quetiapine) is preferred, at the lowest effective dose, with close monitoring. Many people benefit from a Cholinesterase Inhibitor first, before antipsychotic medication is considered.

Parkinsonian features

Mild Parkinsonism may be tolerated without treatment. Where treatment is needed, low-dose Levodopa under specialist supervision is the usual first choice. Dopamine agonists are generally avoided because they can worsen hallucinations.

Sleep

REM Sleep Behaviour Disorder often responds to Melatonin (typically 3 to 6 mg at night) or low-dose Clonazepam under specialist guidance. Safe sleep arrangements (padded bedrails, partner in a separate bed if injuries occur) are recommended.

Autonomic features

Postural drops in blood pressure may need increased salt and fluid intake, compression stockings or medication (Midodrine, Fludrocortisone). Constipation responds to dietary fibre, fluids and softeners.

Medicines to avoid or use with extreme caution

• Typical antipsychotics (Haloperidol) and most atypicals at usual doses;
• High-dose anticholinergic medicines (some bladder, sleep and antidepressant medicines);
• Benzodiazepines, which can worsen confusion and falls;
• Dopamine agonists for Parkinsonism, which can trigger hallucinations.

What course it takes

The trajectory is variable. Mean life expectancy from diagnosis is around 5 to 8 years, often shorter than Alzheimer's Disease, but the early years can be substantially helped by Cholinesterase Inhibitor treatment. Recurrent falls, episodes of acute confusion (Delirium) and pneumonia are common contributors to deterioration.

Where to get assessed

Dementia with Lewy Bodies is sometimes missed when symptoms are subtle. If the diagnosis has been queried but not confirmed, or if you have features that suggest Dementia with Lewy Bodies but were given a different label, a second opinion can be valuable. The Dementia Service is the leading UK Private Memory Clinic and can arrange DAT Scan and other onward investigation alongside the structured letter to your GP.