INTRODUCTION AND BACKGROUND
Psychogenic movement disorder (PMD) is a clinical syndrome defined as the occurrence of abnormal movements that result from a psychiatric cause rather than a general medical or neurologic cause . Psychogenic movement disorders were first described in the late 19th and early 20th centuries and have been the subject of great interest and puzzlement ever since [2-4]. Alternative terms for PMD include hysterical movement disorder, functional movement disorder, nonorganic movement disorder, and medically unexplained motor symptoms . In modern times, awareness of PMDs has increased in the movement disorder literature. However, the pathogenesis and pathophysiology of PMDs remain poorly understood [6-8].
The dangers of PMDs are manifold: excessive investigation of PMD resulting in reinforcing the sick role, misdiagnosing organic illness as psychogenic , misdiagnosing PMD as organic, and failure to recognize a kernel of organic illness embedded in the symptoms of a PMD . The prevalence, poor prognosis, and intensive healthcare utilization of PMDs present a problem that has been likened to a crisis in neurology . In order to offer the best chance for remission and to use scarce resources wisely, rapid and accurate diagnosis of psychogenic movement disorders is essential.
This topic will review clinical aspects of PMDs, including epidemiology, clinical features, diagnosis, management and prognosis.
The precise incidence and prevalence of PMD are unknown, as population-based studies are unavailable. Estimates of the prevalence of PMD among adults and children with movement disorders vary between 2 to 4 percent [12-17]. Women are affected more often than men. A retrospective chart review of our center in Toronto yielded 206 patients with a diagnosis of PMD out of 7624 records, for a prevalence of 3 percent . Of note, our center receives referral from both primary care physicians and from other academic movement disorders centers. The prevalence of PMD among patients who present with dystonia and fixed, contracted joints may be even higher. As an example, one study of 41 such patients with prospective data reported that criteria for psychogenic dystonia were fulfilled in 15 (37 percent) .
In most reports of adults and children with PMD, psychogenic tremor is the most frequent type of involuntary movement, followed by psychogenic dystonia [12,19-21]. Among our cohort of 206 patients with PMD, the most common psychogenic involuntary movements were tremor (33 percent), dystonia (25 percent), myoclonus (25 percent), gait disorders (11 percent), and parkinsonism (6 percent) . Women comprised 77 percent of the total cohort. Although our population is culturally diverse, a formal study of transcultural differences that compared patients with PMD from the United States and Spain revealed similar frequencies of movement types, gender, anatomic distribution, and disability across ethnic groups .