Phenotype-specific diagnosis of functional (psychogenic) movement disorders

Published diagnostic criteria for functional (psychogenic) movement disorders (FMDs) include psychiatric symptoms and some historical variables to affect the threshold between categories of diagnostic certainty. Clinically probable and possible categories, however, do not suffice to rule in FMD or rule out complex organic movement disorders and therefore are of little practical help. In contrast, a handful of unequivocal and reliably incongruent or inconsistent clinical features in each functional movement phenotype, when present, allow a clinically definite diagnosis of FMD, regardless of any psychiatric symptom. We suggest that the use of phenotype-specific clinically definite FMD diagnostic criteria will increase inter-rater reliability and minimize false-positive diagnostic errors. This process involves the ascertainment of core (mandatory) examination features instead of supportive but insufficiently sensitive historical, psychiatric, and inconsistent examination features.