Dementia With Lewy Bodies

Dementia with Lewy bodies is characterized by microscopically identified Lewy bodies in the cerebral cortex and other areas of the brain. Patients tend to have well-defined visual hallucinations, parkinsonism, frequent falls, fluctuations in alertness, and abnormal sleep characterized by acting out dreams. Diagnosis is by history and physical examination. Treatment is supportive measures and sometimes a cholinesterase inhibitor; antipsychotics should be avoided when possible because they tend to have severe adverse effects in patients with this dementia.

Geriatric Essentials

• In elderly patients with dementia, symptoms that suggest dementia with Lewy bodies include well-defined visual hallucinations, parkinsonism, falls, fluctuations in alertness, daytime drowsiness, sleep abnormalities, and disproportionate deterioration of visuospatial ability.
• Treatment with dopaminergic drugs may precipitate delirium, and treatment with antipsychotics can cause severe extrapyramidal effects.

Dementia with Lewy bodies accounts for up to 25% of cases of dementia. Age at onset is typically > 60.

Lewy bodies are rounded eosinophilic intracytoplasmic neuronal inclusions that contain the protein -synuclein; they are characteristic of dementia with Lewy bodies and of Parkinson's disease. In dementia with Lewy bodies, Lewy bodies occur in the cerebral cortex and other areas of the brain. In Parkinson's disease, Lewy bodies occur in selected subcortical structures, most notably the substantia nigra. Dementia with Lewy bodies, Parkinson's disease, and Alzheimer's disease (AD) overlap considerably. For example, patients who have Parkinson's disease may develop dementia with Lewy bodies; patients who have AD may have a modest number of Lewy bodies, and patients who have dementia with Lewy bodies may have neuritic plaques and neurofibrillary tangles. Further research is needed to clarify the relationships among these disorders.

Symptoms

Initial cognitive deterioration resembles that of other dementias. Patients may have well-defined visual hallucinations (often threatening), fluctuations in cognitive function, and mild parkinsonism. Periods of being alert, coherent, and oriented may alternate with periods of being confused and unresponsive to questions, usually over a period of days to weeks but sometimes during the same interview. Paranoia and falls are common. Delusions occur in 50 to 65% of patients and are often complex and bizarre, compared with the simple persecutory ideation common in AD. Dementia with Lewy bodies also causes daytime drowsiness and sleeping (often for > 2 h before 7:00 PM); patients tend to stare into space for long periods. Cognitive impairment affects visuospatial and visuoconstructional function more than memory. These features may help distinguish this dementia from AD.

Memory is impaired, but impairment appears to result more from deficits in alertness and attention than from deficits in memory acquisition. Patients who have dementia with Lewy bodies or who have Parkinson's disease may act out dreams.

Autonomic dysfunction is common; unexplained syncope may result. Autonomic dysfunction may occur with or after onset of cognitive deficits. Extreme sensitivity to antipsychotic drugs is typical. Dementia progresses, and prognosis is poor.

Diagnosis

Diagnosis is considered probable if 2 of 3 features (fluctuations in cognition, visual hallucinations, and parkinsonism) are present and possible if only one is present. Supportive evidence consists of repeated falls, syncope, and sensitivity to antipsychotics.

Because dementia with Lewy bodies causes deficits in alertness and attention, it may be difficult to distinguish from delirium. Thus, all patients presenting with these deficits should be evaluated for delirium.

Because symptoms overlap, dementia with Lewy bodies is difficult to distinguish from Parkinson's-associated dementia. Antemortem differentiation between dementia with Lewy bodies, Parkinson's-associated dementia, and AD is based on behavioral and motor functions. When parkinsonian motor deficits precede and are more severe than cognitive impairment, Parkinson's-associated dementia is usually diagnosed. When early cognitive impairment and behavioral disturbances predominate, dementia with Lewy bodies is usually diagnosed.

CT and MRI show no characteristic changes but are helpful initially in ruling out other causes of dementia. Positron emission tomography (PET) with fluorine-18-labeled deoxyglucose and single-photon emission CT (SPECT) with ¹²³I-FP-CIT (N-w-fluoropropyl-2b-carbomethoxy-3b-[4-iodophenyl]-tropane), a fluoroalkyl analog of cocaine, may help identify dementia with Lewy bodies, but these tests are not routinely done. Definitive diagnosis requires autopsy samples of brain tissue.

Treatment

General treatment measures are the same as those for dementia of any cause. Cholinesterase inhibitors, used to treat AD, typically reduce the cognitive deficits of patients who have dementia with Lewy bodies.

Treatment of parkinsonian symptoms with dopaminergic drugs, if necessary, should be done cautiously because they may precipitate delirium. If such drugs are needed, levodopa is preferred. Treatment with antipsychotics, even at very low doses, usually leads to severe extrapyramidal effects with acute worsening of parkinsonian symptoms; these drugs are best avoided.

This topic was last updated February 2006.