What Is Dementia with Lewy Bodies?
Dementia is a gradual decline of cognitive functions, including memory, language abilities and problem solving skills, severe enough to interfere with normal daily functioning. There are many causes of dementia, the most common form being Alzheimer's disease, where memory loss is the most prominent feature. Dementia with Lewy bodies (DLB) or Lewy body dementia is the second most common cause of dementia in the general population and affects an estimated 1.4 million individuals and their families in the United States.
Lewy body dementia is named after deposits called Lewy bodies, which are collections of an abnormal protein called alpha-synuclein. Lewy bodies are found throughout the outer layer of the brain (the cerebral cortex) and deep inside the midbrain and brainstem. They can also be found in Alzheimer’s disease, Parkinson’s disease, Down syndrome, and other disorders.
Signs and Symptoms
Lewy body dementia consists of a combination of symptoms: dementia, parkinsonism (slowness, stiffness, tremor and problems walking) and visual hallucinations (seeing things that are not real). Patients with Lewy body dementia may not have significant memory problems in the beginning, but almost always suffer from attention deficits, difficulties organizing and carrying tasks to completion, and problems with their visuospatial abilities. The symptoms usually fluctuate with "good days" and "bad days." The hallucinations in Lewy body dementiaare usually visual, such as anonymous people, family members, small animals or machines. They tend to be in color, very detailed and nonthreatening. Insight is usually retained, especially in the beginning. Many patients with Lewy body dementia also have repeated falls, faintness and marked sensitivity to certain psychiatric drugs (neuroleptics). Besides hallucinations, other psychiatric symptoms include delusions, depression and apathy. Patients with Lewy body dementia also tend to act out their dreams and become quite agitated and combative during sleep. This is known as REM sleep behavior disorder (RBD), which may precede the onset of any other symptom of Lewy body dementia by several years. On examination, besides cognitive impairment and parkinsonian features, many patients with Lewy body dementia have jerk-like movements (myoclonus).
Cognitive impairment may also be present in Parkinson's disease (PD) and is called Parkinson's disease dementia (PDD). It occurs in about one-third of Parkinson's disease patients, particularly in advanced stages. Severe dementia may be associated with agitation, disorientation, confusion and hallucinations. These and other psychiatric symptoms often necessitate close supervision by caretakers. Lewy body dementia and Parkinson's disease dementia probably represent the two clinical entities on a spectrum of Lewy body disease. The time course of the clinical symptoms differentiates these two conditions. In Parkinson's disease dementia, dementia develops within the context of an already established diagnosis of Parkinson's disease. In Lewy body disease, dementia precedes or coincides with the development of parkinsonian signs for at least one year.
The cause of Lewy body disease is unknown, but problems with cellular processing of abnormally folded proteins in certain brain cells have been suspected to cause the neurodegeneration in brain cortex and in the basal ganglia, the deep portion of the brain involved in control of movement. Although few families with Lewy body disease have been described, the disorder is almost always sporadic (not genetic). Analysis of the genetic forms of this disorder allows researchers to work on identifying proteins involved in the disease process. About one-third of Alzheimer's disease patients develop signs of parkinsonism, such as tremor, rigidity, slowed movement, and postural instability. Additionally, patients with PD have a slightly higher risk for Alzheimer's disease than those without PD, but the dementia that is seen in advanced stages of PD appears to be due to progression of PD rather than a co-existent Alzheimer's disease. A gene called APOE4, thought to increase risk of Alzheimer's dementia, has been found to increase risk of Lewy body disease as well.
Although Lewy body disease patients usually do not respond as well to levodopa as those with typical PD, many do obtain satisfactory improvement with levodopa and benefit from chronic treatment. The treatment of hallucinations, delusions, agitation, and other psychiatric symptoms may be challenging. The traditional antipsychotic drugs (also called typical neuroleptics), such as haloperidol (Haldol), can worsen parkinsonian symptoms, and should not be used.
The newer, atypical antipsychotic drugs, such as clozapine (Clozaril), olanzapine (Zyprexa), quetiapine (Seroquel), ziprasidone (Geodon), and aripiprazole (Abilify) can suppress hallucinations and treat other psychiatric problems without worsening parkinsonian symptoms. However, clozapine can cause loss of infection-fighting white blood cells in one to two percent of cases, a serious side effect that limits the usefulness of this drug. Also, medications used for dementia and behavioral problems associated Alzheimer's disease, such as donepezil (Aricept), rivastigmine (Exelon), and memantine (Namenda), may be helpful in Lewy body disease.
In most cases, Lewy body disease patients can live at home with careful monitoring and supervision. Some days, they may need more assistance than others but can find reassurance through caregivers help in turning their attention away from hallucinations. Support groups can help by teaching skills in how to communicate with a patient who has dementia. This will help reduce both patient and caregiver frustration.