Lewy Body Dementia (LBD) encompasses two clinical entities, namely dementia with Lewy bodies and Parkinson disease dementia. It is a progressive degenerative brain disorder characterized by dementia, psychosis, and features of parkinsonism. Symptoms fluctuate with time and vary among different individuals. Diagnosis of LBD requires thorough clinical examination as many of its features overlap with other dementia disorders. It is the third most common type of dementia after Alzheimer disease and Vascular dementia. It characterizes by the deposition of Lewy bodies in the brain that are intraneuronal cytoplasmic inclusion bodies having aggregates of alpha-synuclein and ubiquitin.
The etiology of LBD is still unknown. Genetics, environmental factors, and changes linked to aging, however, may have a role and still require further research.
LBD is an under-diagnosed condition as it is poorly understood and its clinical features overlap with other more common disorders, like Parkinson's disease and Alzheimer's disease. Studies have shown, however, that it accounts for up to 20% to 30% of all dementia cases. It is more common in men, and incidence increases with advancing age. It is prevalent in Asian, African, and European races. A family history of LBD and Parkinson disease increases a patient's risk.
Like Alzheimer disease, LBD presents with acetylcholine deficiency, but it is more pronounced in LBD. Decreased levels of acetylcholine in temporal and parietal cortex result in visual hallucinations (a prominent feature of LBD), while up-regulation of muscarinic M1 receptors in the temporal lobe results in delusions. Dopamine levels also diminish.
The pathology of LBD overlaps that of Parkinson's disease and Alzheimer's disease. Neuronal cytoplasmic inclusion bodies, called Lewy bodies (comprising aggregates of ubiquitin and alpha-synuclein) and found within brain parenchyma (mainly in the brainstem, limbic system, and cerebral cortex), are characteristic of Lewy body dementia. Genetic mutations, environmental toxins, and the aging process can lead to misfolding of alpha-synuclein and its accumulation in the form of Lewy bodies via oxidative stress and mitochondrial dysfunction. The location of Lewy bodies determines the clinical presentation. If Lewy bodies develop initially in the brainstem and cerebral cortex, then dementia sets on early, and we call it dementia with Lewy bodies; however, if Lewy bodies develop initially in the brain stem only and extend to cerebral cortex later, then dementia occurs late in the disease process and we call it Parkinson disease dementia. Other features include Lewy neuritis, senile plaques, neurofibrillary tangles, and neuronal loss in the substantia nigra, locus coeruleus, and Meynert nucleus.
There is a large variation in symptoms manifested among patients and their time of onset. The main features include progressive dementia (mainly affects attention and executive function, memory loss is not common but can occur later in the disease process), fluctuation cognitive function (with variation in attention and episodes of drowsiness), visual hallucinations (detailed and recurrent), and features of parkinsonism like muscular rigidity, tremors, and bradykinesia.
Other less common features include REM sleep behavior disorder, autonomic dysfunction, unexplained falls, depression, and sensitivity to antipsychotic medication.
No precise test can accurately diagnose LBD. Usually, a thorough workup, including the following, is useful to reach an alternative working diagnosis or rules out similar conditions:
Due to the incomplete specificity in the clinical diagnosis and the pathological definition of the disease, a postmortem biopsy or autopsy is the only method to secure a definite diagnosis.
Support and Therapies
Patient and caregiver education regarding symptoms of a disease and their management is necessary. Understanding the disease helps the caregivers cope with the everyday challenges. They require home modifications occasionally and individual patient needs should specifically guide them.
Patients can take part in different therapies to improve their quality of life, including:
It is of utmost importance to differentiate LBD from similar conditions since it is more responsive to certain medications if used early in the disease course.
Similar conditions include:
The prognosis of LBD is fair to poor. Patients die from multiple complications like falls, immobility, cardiac complications, medication side effects, pneumonia, swallowing problems, and depression leading to suicide. The average life expectancy is only five to eight years after the initial diagnosis. This also can be due to a lack of knowledge regarding LBD among physicians and the population and difficulty in differentiating it from other similar conditions which leads to a delay in diagnosis which delays the onset of specific therapy. Health professionals need to improve awareness regarding LBD and there should develop investigative methods to ensure its early diagnosis.