Functional (psychogenic) movement disorders: merging mind and brain.

Functional (psychogenic) movement disorders (FMD) are part of the wide spectrum of functional neurological disorders, which together account for over 16% of patients referred to neurology clinics. FMD have been described as a "crisis for neurology" and cause major challenges in terms of diagnosis and treatment. As with other functional disorders, a key issue is the absence of pathophysiological understanding. There has been an influential historical emphasis on causation by emotional trauma, which is not supported by epidemiological studies. The similarity between physical signs in functional disorders and those that occur in feigned illness has also raised important challenges for pathophysiological understanding and has challenged health professionals' attitudes toward patients with these disorders. However, physical signs and selected investigations can help clinicians to reach a positive diagnosis, and modern pathophysiological research is showing an appreciation of the importance of both physical and psychological factors in FMD.