Prevalence of functional (psychogenic) parkinsonism in two Swiss movement disorders clinics and review of the literature

• Published in: Journal of the neurological sciences Vol. 387; pp. 37 - 45
• Main Authors: Frasca Polara, Giulia, Fleury, Vanessa, Stone, Jon, Barbey, Anita, Burkhard, Pierre R., Vingerhoets, François, Aybek, Selma
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15-04-2018
• Subjects: Functional movement disorder; Parkinsonism; Prevalence; Prodromal manifestation; Parkinsonism; Prevalence; Prodromal manifestation; Functional movement disorder
• ISSN: 0022-510X; 1878-5883
• DOI: 10.1016/j.jns.2018.01.022

Functional parkinsonism (FP) is considered rare but no studies have looked at its frequency. Case series have described high rates of comorbidity with Parkinson's disease (PD), suggesting a possible association between these conditions.
To study the prevalence, epidemiology and clinical features of FP and its association with PD.
We conducted a cross-sectional population-based prevalence study as well as a chart review of cases who received a diagnosis of FP over a 10-year-period in two movement disorder clinics in Switzerland. Epidemiological data regarding FP features were collected. The co-occurrence of PD, psychiatric disorders and other functional disorders were recorded. Clinical differences between FP and FP+PD groups are presented and discussed in light of a literature review.
The crude prevalence of FP was 0.64 per 100,000 in our population. FP represented 0.24% of patients with parkinsonism. Among 12 FP cases, female gender predominance (87%), mean age of onset of 45.5(±13.3 Standard deviation SD) years and prolonged diagnostic delay (mean 59±75 SD months) was found. Six patients had an additional diagnosis of PD, 83% of depression and 66% of other functional neurological disorder. In four patients with FP+PD, FP preceded PD by 6 to 56months.
These results suggest that FP should be considered in the differential diagnosis of patients presenting with parkinsonism. The high rate of co-occurrence with PD emphasizes the importance of long-term follow up of these patients. The observation that FP often precedes PD should be verified in prospective studies.
•Functional Parkinsonism represents 0.24% of patients with parkinsonism.•Functional Parkinsonism has a young age of onset (45yo).•Functional Parkinsonism has a very long diagnostic delays (5years).•Functional Parkinsonims can co-occur with or precede Parkinson's disease.