Description
Lewy Body Dementia (LBD) is a type of progressive dementia that results from the degeneration and death of nerve cells in the brain. The disease is characterised by the presence of protein deposits known as Lewy bodies, which impair the function of neurons and lead to a range of cognitive, behavioural, and motor deficits.
Pathogenesis
The primary pathological feature of LBD is the presence of Lewy bodies – abnormal aggregates of the protein alpha-synuclein – in the cortical areas of the brain. These deposits disrupt the normal functioning of neurons, leading to the clinical features of LBD. The precise mechanisms by which Lewy bodies form and contribute to neuronal death are still being researched.
Epidemiology, Risk Factors & Associations
LBD is the third most common cause of dementia, after Alzheimer’s disease and vascular dementia, accounting for 5-20% of all dementia cases. It typically affects people aged 50 years or older, with a slight male predominance. Risk factors include older age and a family history of LBD or Parkinson’s disease. It is often associated with Parkinson’s disease and may overlap with Alzheimer’s disease in some cases.
Clinical Features
The cardinal features of LBD are cognitive fluctuations, recurrent visual hallucinations, and parkinsonism. Cognitive symptoms can be variable and may include attention deficits, executive dysfunction, and visuospatial impairment. Behavioural and mood symptoms, such as depression and apathy, are also common.
Complications
Complications of LBD include falls, pneumonia, severe sensitivity to neuroleptic medication, and a reduced life expectancy compared to the general population.
Pathological Features
Histopathology
LBD is characterised by the widespread presence of Lewy bodies in the cortex. The Lewy bodies are spherical inclusions located within the cytoplasm of neurons, made up of alpha-synuclein protein.
Radiological Features
General Features
Although routine imaging is typically normal in LBD, various neuroimaging techniques can show changes consistent with the disease.
MRI
- T1/T2: Generally normal in early disease, but can show global cerebral atrophy in advanced disease.
- DTI: May show alterations in white matter tracts.
NM
- PET/SPECT: Dopaminergic imaging can show reduced uptake in the striatum, similar to Parkinson’s disease.
Diagnosis
Diagnosis of LBD is primarily clinical, based on the presence of its characteristic features. Functional imaging and neuropsychological testing can provide supportive evidence.
Differential Diagnosis
- Alzheimer’s disease: Characterised by memory impairment and agnosia, with absence of motor symptoms in early stages.
- Parkinson’s disease: Parkinsonism precedes cognitive impairment by at least one year.
Management
Management of LBD is typically by a neurologist and includes symptomatic treatment with cholinesterase inhibitors for cognitive symptoms, careful use of antipsychotics for hallucinations, and physical therapy for motor symptoms.