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

BACKGROUND: 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. OBJECTIVES: To study the prevalence, epidemiology and clinical features of FP and its association with PD. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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 movement disorders.

PURPOSE OF REVIEW: The review highlights the clinical presentation of functional movement disorders (FMDs) and presents current evidence on bedside signs and paraclinical tests to differentiate them from other neurological disorders. RECENT FINDINGS: FMDs are diagnosed by the presence of positive clinical signs as emphasized in the new Diagnostic and Statistical Manual of Mental Disorders-5 classification criteria. Bedside signs are numerous, and a subset of them has been validated in controlled studies. This review summarizes evidence from the literature on specificity and sensibility of positive clinical signs for FMDs. The value of rule-in paraclinical tests to confirm the diagnosis is also presented. Recent developments in neuroscience with pathophysiological mechanisms and current treatment strategies are also discussed. SUMMARY: FMDs represent a field of neurology that is currently rapidly growing in terms of research. Clinicians should be aware that highly reliable signs exist for the diagnosis and that early multidisciplinary treatment should be offered.