Prevalence and diagnosis of Parkinson's disease: a community study

Clinicopathological and community studies have demonstrated misdiagnosis in Parkinson’s disease (PD). Clinical trials of antiparkinson medication have also shown a subset of patients labelled as having PD have normal functional brain dopaminergic imaging. Conditions commonly misdiagnosed as PD include Essential tremor (ET), vascular Parkinsonism (VP) and dystonic tremor (DT). This thesis examines the accuracy of clinical diagnosis of PD in a community setting by identifying misdiagnosed cases and supervising antiparkinson medication withdrawal. Prescription database searches and GP case record review were carried out in 92 West Scotland GP practices within a population of 511,927. 610 patients on antiparkinson medication for a PD diagnosis were identified and age-adjusted prevalence was 129.5 per 100,000. Patients were invited for assessment if there was (a) no increase in dopaminergic drug dose or (b) no recorded progression of disease over time, suggestive of possible misdiagnosis. 64 patients were assessed and this was supplemented with FP-CIT SPECT scanning in 25 uncertain cases. Patients considered unlikely to have PD were advised to reduce and discontinue antiparkinson drugs, with repeat PD motor scoring over 6 months. 33 of 64 patients (51.6%) successfully completed antiparkinson medication withdrawal. An age, sex and disease duration matched control group was also assessed. The selection criteria allowed identification of a high proportion of misdiagnosed cases and FP-CIT SPECT was a useful diagnostic tool for assessing patients (previously diagnosed as PD) in whom there was diagnostic doubt