How to diagnose dementia with Lewy bodies: state of the art.

Dementia with Lewy bodies (DLB) is the second most common cause of neurodegenerative dementia in older people that has only been recognized in the past decade and that remains widely underdiagnosed. At postmortem examination, affected patients show numerous alpha-synuclein-positive Lewy bodies (LB) in many parts of the cerebral cortex, particularly neocortical and limbic areas in addition to the nigral LB degeneration characteristic of Parkinson's disease (PD). Clinical presentation, unlike PD, is with progressive cognitive decline with particular deficits of visuospatial ability as well as frontal executive function accompanied by usually only mildly to moderately severe parkinsonism, which is often akineto-rigid without the classical parkinsonian rest-tremor. Further accompanying features include spontaneous recurrent visual hallucinations and conspicuous fluctuations in alertness and cognitive performance. The two main differential diagnoses are Alzheimer's disease (AD) and Parkinson's disease dementia (PDD). To improve the differential diagnosis of DLB, consensus criteria have been developed that establish possible and probable levels of clinical diagnostic accuracy. Generally, their sensitivity is variable and low but their specificity is high. Current consensus is to restrict a diagnosis of DLB only to patients with parkinsonism who develop dementia within 12 months of the onset of motor symptoms. Using operationalized criteria, DLB can be diagnosed clinically with an accuracy similar to that achieved for AD or PD. Ancillary investigations, particularly neuroimaging, can aid in differential diagnosis. We review the present state of the best practice in the clinical diagnosis of DLB. Future modifications of diagnostic criteria would ideally include the full range of clinical presentations that can be associated with LB disease.