General overview of psychogenic movement disorders: Epidemiology, diagnosis, and prognesis

Epidemiologic studies of "medically unexplained symptoms" are fraught with problems. Despite numerous confounding issues, it is clear that conversion disorders are probably as common as other disabling conditions such as multiple sclerosis and schizophrenia. Little is known about the frequency of movement disorders as a manifestation of conversion disorders. Reports from subspecialty clinics all suffer from ascertainment as well as selection/referral biases with an underrepresentation of acute or transient cases and overrepresentation of chronic or refractory problems. Although underlying neurologic diseases need to be carefully excluded when dealing with such patients, the diagnosis itself is not one of exclusion. Certain historical features are common to many different types of psychogenic movement disorders (PMDs), including abrupt onset (often triggered by a minor injury for which litigation or compensation is sought), rapid progression to maximum disability or peak severity shortly after onset, static course, previous remissions, and paroxysmal exacerbations. Clinical features common to most PMDs are the incongruity with their organic counterparts and inconsistencies during the examination, over time or with historical information provided. Additional "nonorganic" neurologic disturbances are also common, including give-way weakness, nonanatomic sensory disturbances, atypical pain syndromes, and extreme slowness of movement. Investigations may not be helpful (except for excluding specific underlying organic disorders), although electrophysiologic testing may be particularly useful in confirming the diagnosis in some PMDs, especially myoclonus and tremor. The diagnosis should not be made or refuted by physicians inexperienced in the investigation and management of both organic and psychogenic movement disorders. In the presence of clear positive confirmatory clinical features, the diagnosis should not be excluded on the basis of the screening psychiatric assessment failing to define the presence of underlying psychopathology. The natural history of PMDs is poorly defined, but often patients remain disabled over prolonged periods of time. Review of the appropriate literature highlights the need for considerable future research to establish a better understanding of all facets of PMDs including epidemiologic features, diagnostic methodologies, pathogenetic mechanisms, and, particularly, more effective treatment strategies.