Diffuse Lewy body disease (DLBD) is considered to be a variant or overlapping condition lying between Alzheimer's disease and Parkinson's disease. Clinical differentiation may therefore be difficult. In most patients with DLBD, however, psychosis and dementia are often found to precede parkinsonism (gait disturbance, rigidity, and resting tremor). The differentiation between DLBD and other parkinsonian syndromes, especially progressive supranuclear palsy, is particularly difficult when a patient with parkinsonism and dementia is also found to have oculomotor deficit.
Possible other features (±)
Dementia Lewy bodies
Gait disturbance Dysautonomia Dysarthria/dysphagia Limb apraxia Myoclonus Oculomotor deficit Sleep impairment
Neuroimaging studies, including magnetic resonance imaging (MRI) and positron-emission tomography (PET) scanning, cannot reliably differentiate between Parkinson's disease, Alzheimer's disease, and DLBD.
Immunocytochemical staining techniques using antibodies against ubiquitin have improved the identification of Lewy bodies. More than 30% of patients with Alzheimer's disease have Lewy bodies in the cortex and substantia nigra, whereas all Parkinson's patients have cortical Lewy bodies. In addition to the diffuse distribution of Lewy bodies throughout the basal forebrain, brain stem, and hypothalamus, the lack of neurofi-brillary tangles in DLBD helps differentiate it from Alzheimer's disease.
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