David J Burn, MD, MA, FRCP, Consultant & Senior Lecturer in Neurology, Regional Neurosciences Centre, Newcastle General Hospital, Westgate Road Newcastle upon Tyne, UK.
Ian G McKeith, MD, FRCPsych, Professor of Old Age Psychiatry, Department of Old Age Psychiatry, Institute for Ageing and Health Wolfson Research Centre, Newcastle General Hospital, Newcastle upon Tyne, UK.
Parkinsonism is a common problem, particularly in the elderly. One percent of the population over the age of 65 has Parkinson's Disease (PD), rising to 2% over the age of 80. Parkinsonism is also a core feature of dementia with Lewy bodies (DLB), the second most common cause of neurodegenerative dementia, after Alzheimer disease (AD). To differentiate patients with PD who develop cognitive impairment from DLB, Consensus Criteria stipulate that parkinsonism must be present for 12 months or less for a patient with dementia to qualify for a diagnosis of DLB.1 If the extrapyramidal features are present for longer than this before the dementia develops, the diagnosis is referred to as PD with dementia.
Although parkinsonism occurs in numerous other neurodegenerative diseases, including multiple system atrophy, progressive supranuclear palsy and corticobasal degeneration, as well as AD, hallucinations are less common.