Dementia with Lewy bodies and Parkinson disease with dementia

The combination of progressive dementia and parkinsonism in a single patient is a common and frustrating condition. It represents one of the main unmet needs of the current management of parkinsonian patients and it is therefore important to encourage any initiative that could improve our understanding of the problem. Patients are usually classified within two clinically defined syndromes: PD with dementia (PDD) and dementia with Lewy bodies (DLB).1,2 Both syndromes present considerable clinical overlap, combining fluctuating subcortical/cortical neuropsychological impairment with neuropsychiatric features and motor parkinsonian symptoms.3 A commonly accepted way to separate these two entities uses a simple 1-year rule: onset of dementia within 1 year of parkinsonism qualifies for DLB while more than 12 months of parkinsonism before dementia onset does so for PDD.4 How relevant such a distinction is remains a matter of debate while most authorities consider that both syndromes represent the motor-onset or the cognitive-onset variants of the same (Lewy body dementia). Separating PDD from DLB according to …