What is dementia with Lewy bodies?

Dementia with Lewy bodies (DLB) is the second or third most common cause of dementia in older adults, depending on the source. The classic features are cognitive changes (often with prominent fluctuations from day to day or hour to hour), visual hallucinations (often vivid and detailed), parkinsonian features (slowness, rigidity, sometimes tremor), REM sleep behaviour disorder (acting out dreams during sleep, often years before other features), and sensitivity to certain medications (particularly antipsychotics).

Why it is different from Alzheimer's. The underlying biology is different. DLB involves accumulation of alpha-synuclein protein in nerve cells (the same protein involved in Parkinson's disease), forming structures called Lewy bodies. Alzheimer's involves amyloid plaques and tau tangles. The clinical pattern is also different: DLB has more prominent fluctuations in alertness, more vivid visual hallucinations, and a different sensitivity profile to medications.

Why it has been underrecognised. DLB is often misdiagnosed as Alzheimer's disease (because both involve cognitive decline) or as Parkinson's disease dementia (because both involve alpha-synuclein and parkinsonian features). The distinction matters because the treatment is different and because some standard medications used in other dementias can cause severe reactions in DLB.

The diagnostic clues. Several features support a DLB diagnosis: prominent visual hallucinations, REM sleep behaviour disorder (often present years before cognitive symptoms), fluctuating cognition, parkinsonian features, severe sensitivity reactions to antipsychotics. Imaging tests can help: DAT-SPECT shows reduced dopamine transporter signal in DLB, cardiac MIBG scintigraphy shows reduced uptake. Plasma and cerebrospinal fluid biomarker testing for alpha-synuclein is improving rapidly.

The therapy approach.

Cholinesterase inhibitors: donepezil and rivastigmine are first-line for cognitive symptoms in DLB and are often more effective in DLB than in Alzheimer's disease. They can also help with hallucinations.

Levodopa: for parkinsonian features, levodopa is used at lower doses than in pure Parkinson's disease, balancing motor benefit with potential worsening of hallucinations.

Antipsychotic management: standard antipsychotics (haloperidol, older agents) often cause severe reactions in DLB and should be avoided. When antipsychotic therapy is needed for severe distressing hallucinations or behavioural symptoms, low-dose pimavanserin or quetiapine are the preferred options.

Behavioural and supportive interventions: structured environments, addressing sensory issues (particularly vision), cautious medication review (avoiding anticholinergic medicines that can worsen cognition), occupational therapy, physical therapy, and family support are all part of comprehensive care.

REM sleep behaviour disorder management: melatonin and clonazepam are used to reduce dream-enactment behaviours.

The emerging direction. Alpha-synuclein-targeted programs (covered in earlier rounds for Parkinson's disease) are reading out in DLB, with the proposition of disease-modifying intervention rather than symptom management alone. Research into prodromal DLB (using REM sleep behaviour disorder as a marker for future risk) is identifying patients earlier in the disease course.

What to expect. DLB is a serious condition but with appropriate diagnosis and care, most patients can live meaningful lives for years after diagnosis. The most important things are accurate diagnosis (so the right medications are used and harmful ones avoided), specialty care from a neurologist familiar with DLB, and proactive management of the multiple dimensions of the condition (cognitive, motor, sleep, behavioural).