Psychogenic movement disorders: past developments, current status, and future directions.

As the field of movement disorders has developed and matured over the past 25 years, psychogenic movement disorders have become increasingly recognized in subspecialty clinics. The diagnosis can be challenging and should be based on positive features rather than a purely exclusionary approach. The clinical phenotype can be quite varied, although certain categories of abnormal movement are more common than others. Electrophysiological studies may be particularly useful in establishing the diagnosis, especially with respect to tremor and myoclonus, and an argument can be made for adding a "laboratory-supported definite" category to earlier classification schemes. The diagnosis of psychogenic dystonia remains a major challenge, although there are some recent promising developments with respect to the evaluation of cortical plasticity that require further study. The pathogenesis of psychogenic movement disorders is poorly understood; insights may be provided from the study of other neurological conversion disorders such as psychogenic hemiparesis. Psychogenic movement disorders typically result in considerable disability and negatively impact quality of life to the same or greater extent than do many organic movement disorders. Treatment is extremely challenging, and many patients experience chronic disability despite various therapeutic interventions. Given the personal and societal impact of these problems, further advances in our understanding of their pathogenesis and the subsequent development of effective therapies are sorely needed.