Idiopathic parkinsonism : epidemiology and clinical characteristics of a population-based incidence cohort

Sammanfattning: Background: Idiopathic parkinsonism is a neurodegenerative syndrome of unknown cause and includes Parkinson’s disease (PD) and atypical parkinsonian disorders. The atypical parkinsonian disorders are: Multiple system atrophy (MSA), progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD). The incidence rates of these diseases in Sweden are largely unknown. The diagnosis of each disease relies mainly on clinical examination although several imaging and laboratory parameters may show changes. A diagnosis based on clinical examination is especially difficult early in the course of each disease; diagnosis is easier later on when disease-charactersistic signs have evolved and become more prominent. However, even in later stages it is not uncommon that patients are misdiagnosed. PD can be divided into subgroups based on the main clinical symptoms, i. e. tremor dominant, postural instability and gait difficulty (PIGD), and indeterminate. The PIGD subtype has worse prognosis including higher risk of dementia. The aims were to study the incidence of idiopathic parkinsonism and the different specific parkinsonian disorders in the Umeåregion and to investigate the patients early in the course of the disease with brainmagnetic resonance tomography (MRI), external anal sphincterelectromyography (EAS-EMG) and oculomotor examination. Can these methods improve the differential diagnostic work-up and/or differentiate between the subtypes of PD? Methods: We examined all patients in our catchment area (142,000 inhabitants) who were referred to us due to a suspected parkinsonian syndrome. Our clinic is the only clinic in the area receiving referrals regarding movement disorders. During the period (January 1, 2004 through April 30,2009) 190 patients fulfilled the inclusion criteria and were included in the study. Healthy volunteers served as controls.  Results: Incidence: We found the highest incidences reported in the literature: PD (22.5/100,000/year), MSA(2.4/100,000/year), and PSP (1.2/100,000/year). No CBD patients were encountered. Brain MRI: Degenerative changes were common both in controls and PD. There were no differences between the PD subtypes. EAS-EMG: Pathological changes in EAS-EMG examination were common in PD, MSA and PSP. It was not possible to separate PD, MSA and PSP by the EAS-EMG examination. Oculomotor examination: Pathological results were common in all diagnosis groups compared to controls. It was not possible to separate PD, MSA and PSP or the PD subtypes with the help of oculomotor examination. Conclusions: The incidences of idiopathic parkinsonism, PD, MSA and PSP were higher than previously reported in the literature. It is not clear weather this is due to a true higher incidence in the Umeå region or a more effective casefinding than in other studies. MRI, EAS-EMG and oculomotor examination could not contribute to the differential diagnostic work-up between PD, MSA and PSP nor differentiate between PD subtypes early in the course of the disease.