Lewy body dementia (LBD) is an umbrella term for two related types of dementia — dementia with Lewy bodies and Parkinson’s disease dementia. Dementia is a disease that progressively impairs a person’s ability to think, reason, remember, and function. Although these two conditions have overlapping features, there are also important distinctions. Understanding LBD causes and symptoms and how its two subtypes, dementia with Lewy bodies and Parkinson’s dementia, differ from one another is critical for proper diagnoses and shortening the time to start treatment.
Read about the diagnosis and treatment of Lewy body dementia.
After Alzheimer’s disease, LBDs are the second most common cause of dementia in people over 65 years old. Scientists are unsure how common these dementias are. In one review of studies on dementia with Lewy bodies, its prevalence in total cases of dementia ranged from 0.3 percent to 24.4 percent, depending on the study. This inconsistency is probably because scientists are only just beginning to understand dementia with Lewy bodies and to differentiate it from Alzheimer's disease. Another study estimates that at least 75 percent of individuals who live with Parkinson’s disease for at least 10 years will develop dementia.
LBDs are poorly understood but are thought to be characterized by the buildup of Lewy bodies in the brain. Lewy bodies are groupings or clumps of badly formed (misfolded) proteins called alpha-synuclein proteins. Healthy alpha-synuclein proteins are normally found widely throughout the brain and are thought to play many roles, including participating in plasticity. This means that they affect how brain cells communicate with one another and change in response to a person’s experience. However, when these proteins misfold and accumulate, the result is Lewy bodies, which lead to cell death in the brain.
The type of LBD a person has is determined by where in the brain the Lewy bodies first begin forming. When Lewy bodies first begin to form in the cortex, dementia with Lewy bodies is the most likely result. These initial protein deposits in the cortex lead to early cognitive changes, such as inattention. When the Lewy bodies first deposit in areas of the brain more related to motor control and movement, such as the substantia nigra, Parkinson’s disease dementia is the most likely result.
But what causes these Lewy bodies to form in the first place?
Genetics or hereditary elements likely play a role. The following genes are thought to be involved in the spectrum of disorders related to Parkinson’s disease, including dementia with Lewy bodies and Parkinson’s:
The APOE gene, which makes protein apolipoprotein E. has been associated with dementia with Lewy bodies. Specifically, dementia with Lewy bodies has been associated with the presence of the ε4 variant, as has Alzheimer’s disease. Parkinson’s dementia is not associated with this gene variant.
These diseases have also been linked to mutations in SNCA (a gene controlling the production of alpha-synuclein) and LRRK2 (a gene that controls the production of a kinase protein). LRRK2 is a particularly interesting gene, as mutations at LRRK2 are linked to the accumulation of both alpha-synuclein and tau protein (another abnormally folded protein that builds up in Alzheimer’s disease). However, more research is needed to understand the complicated role of these genes and how they may be interacting. Alterations in these proteins can lead to devastating consequences for individuals with Parkinson’s disease.
There are many signs and symptoms of LBD. A major hallmark is cognitive impairment. It is defined in the most recent version of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) as cognitive decline in one or more areas (complex attention, executive function, learning and memory, language, perceptual-motor, or social cognition). People with problems in these areas might be forgetful, have problems paying attention, have trouble with problem-solving, be unable to learn new facts or skills, have difficulty with speaking or forming sentences, or have behavioral changes. These symptoms can range from mild to major, and in order to make the diagnosis, they must significantly impair a person’s day-to-day functioning.
Cognitive impairment isn’t the only hallmark of LBD. People with dementia with Lewy bodies and Parkinson’s dementia may present very differently because of how (and where) the Lewy bodies deposit in the brain.
Dementia with Lewy bodies is characterized by three main features, according to the DSM-5:
Other features that can suggest dementia with Lewy bodies are:
Parkinson’s disease dementia symptoms are similar, but the timing is different. The important difference is that in Parkinson’s dementia, parkinsonian movement symptoms (slow movement, shuffling walk, tremors, shaking, rigid muscles, muscle cramps, balance problems) start before cognitive symptoms and dementia appear.
Hallmark symptoms of both diseases include:
Once dementia develops in someone with Parkinson’s disease (resulting in Parkinson’s dementia), there are no clinical or biological differences that can reliably distinguish it from dementia with Lewy bodies.
Diagnosing LBD can be challenging. Dementia with Lewy bodies is most often misdiagnosed as Alzheimer’s disease. The biggest difficulty in the diagnosis of dementia with Lewy bodies is early diagnosis and differentiation from Alzheimer’s. In Parkinson’s disease dementia, the main challenge is timely identification of cognitive impairment in individuals with Parkinson's disease.
To make a diagnosis, doctors will use specific clinical interview questionnaires, rating scales, and laboratory tests (including neuroimaging like MRI and PET scans). Neurological and physical exams will also be needed. Imaging techniques can be particularly useful when trying to distinguish LBD from Parkinson’s disease. Careful, accurate assessments and appropriate management plans are necessary components of diagnosing Lewy body diseases.
Several treatment strategies have been clinically shown to improve the symptoms of LBD. Some of these choices are medications and others are therapy-based options.
Although cholinesterase inhibitors cannot cure dementia, they can help slow the process and improve symptoms for some individuals. Cholinesterase inhibitors help increase the amount of important chemicals called neurotransmitters in the brain, which can help with memory and daily functioning. In one study, people with dementia with Lewy bodies who were treated with the drug rivastigmine had better moods, increased attention, and decreased hallucinations. The side effects generally include nausea, vomiting, and reduced appetite.
In another class of drugs called N-methyl-D-aspartate antagonists, memantine has been shown to improve attention and memory in people with dementia with Lewy bodies and Parkinson’s disease dementia.
People with LBD may often experience a sleep disorder called rapid eye movement sleep behavior disorder. This can sometimes be treated with sedatives like clonazepam or with melatonin (a sleep aid hormone). Other more severe symptoms of LBD including fluctuating levels of alertness (zoning out), hallucinations, agitation, severe confusion, and delirium can be challenging to treat. Doctors must first rule out underlying causes like infection or other medications that can be triggering these symptoms. If unable to find a treatable cause, doctors may use a low dose of the atypical antipsychotic medication quetiapine to treat these symptoms. However, people with LBD must not be given typical antipsychotics (like haloperidol) or high-potency atypical antipsychotics (like olanzapine), as people with LBD are very sensitive to these medications and may develop neuroleptic malignant syndrome if they take them. This is a life-threatening condition that causes fever, muscle stiffness, and racing heart and can lead to heart and kidney failure. Talk with your doctor about medication options.
Many nonmedical treatments can help improve the quality of life for people with Parkinson’s disease, dementia with Lewy bodies, and Parkinson’s disease dementia. Some of these choices include cognitive behavioral therapy, physical exercise and physical therapy, listening to music, and transcranial direct current stimulation.
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