Lewy body dementia (LBD) is an umbrella term for two types of similar dementias: dementia with Lewy bodies (DLB) and Parkinson’s disease dementia (PDD). The similarities between DLB, PDD, and even Alzheimer’s disease lead to challenges in their diagnosis and treatment. Hallmark features of LBD are movement disorders, the presence of brain protein deposits called Lewy bodies, and symptoms of dementia, like cognitive impairment.
DLB and PDD can be difficult to distinguish, particularly at later stages. Their similarities have led some researchers to think that they might, in fact, be different manifestations of the same disease. Careful diagnostic approaches in these cases can lead to better symptom treatment and quality of life.
Read about Lewy body dementia causes and symptoms.
Diagnosing LBD is complicated, and research is ongoing into the biology of both DLB and PDD. Understanding how they differ biologically can help distinguish one disease from the other, which is important when it comes to treatment. One way researchers can distinguish DLB from PDD is by looking at the buildup over time of a protein called alpha-synuclein, a component of Lewy bodies.
To definitively diagnose LBD, teams including neurologists and other specialists use a variety of methods. First, they look for clinical signs of LBD. Doctors use many questionnaires and surveys to measure a person’s cognition and movement symptoms, which can help differentiate these similar disorders.
Next, special brain scans, called single-photon emission computed tomography (SPECT) or positron emission tomography (PET), can be used to find damaged areas of the brain that are typical of LBD. These scans use special molecules that bind to sites in the brain tissue called dopamine transporters. The dopamine transporters light up on SPECT and PET scans and help differentiate LBD from Alzheimer’s disease.
Dementia with Lewy bodies is characterized by dementia symptoms that start before motor (movement) symptoms appear. Research suggests this is because Lewy body proteins first begin to accumulate in the brain’s cortex, causing cognitive symptoms to appear before motor ones. This is a defining feature in the diagnosis of DLB, according to the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders,
In addition, at least one of these core clinical features must be present for a diagnosis of DLB to be made:
Other diagnostic features of DLB include rapid eye movement sleep behavior disorder and severe neuroleptic (antipsychotic medication) sensitivity. The presence of motor symptoms is the key to distinguish DLB from Alzheimer’s disease, as motor or movement symptoms are not present in Alzheimer’s disease.
Parkinson’s disease dementia is characterized by dementia symptoms that occur after Parkinson’s disease has begun. A diagnosis of PDD typically consists of a preexisting diagnosis of Parkinson’s disease, a disease of disordered movement with later cognitive decline. Clinical assessments for cognitive decline can include tests of executive functioning (planning, adaptable thinking, and organization) and memory.
Biologically speaking, the Lewy bodies in PDD usually begin in areas of the brain related to motor function, such as the basal ganglia. Later, as they move into other areas like the cortex, cognitive decline becomes apparent.
For someone living with dementia, a proper diagnosis is important for their quality of life. Confusion or misdiagnosis may delay treatment and cause undue hardship.
One type of treatment for DLB is the family of medications known as cholinesterase inhibitors. These drugs help maintain normal levels of a chemical in the brain called acetylcholine. Long-term treatment of individuals with DLB using one of these drugs, rivastigmine — sold as Exelon — has been scientifically shown to increase cognitive function and decrease neuropsychiatric symptoms.
Another type of medication called N-methyl-D-aspartate (NMDA) antagonists can also help individuals with DLB. The NMDA antagonist drug Namenda (memantine) has been shown to improve clinical outcomes compared to placebo in individuals with DLB (but not PDD).
Antipsychotic drugs are sometimes used to treat the symptoms of dementia, like hallucinations and agitation. For individuals with DLB, however, it is crucial to select the right medication. The biological effects of DLB make people more sensitive to these drugs, so certain antipsychotics can be extremely harmful.
Cholinesterase inhibitor medications are also used to treat individuals with PDD, while studies with NMDA antagonists have shown mixed results. Some research has shown that they don’t significantly affect clinical symptoms, while other studies with the same drug (memantine) find that they help those with PDD.
In addition to medications, cognitive behavioral therapy (CBT) has been proven helpful in cases of dementia. CBT is a form of talk therapy that focuses on using skills, such as mindfulness, to work through negative emotions.
Exercise is also helpful in cases of Parkinson’s disease. It may be able to help those with LBD as well. In one study of individuals with Parkinson’s disease, aerobic exercises like running decreased cognitive impairments.
Music therapy has also been used in cases of dementia. In one study, music therapy helped people with mild to moderate dementia relax, and it reduced their symptoms of depression. More research is needed to examine the role of nontraditional treatments for DLB and PDD.
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