Suggestibility as a valuable criterion for laboratory-supported definite functional movement disorders

Abstract

Highlights We present equivocal cases of FMD, but with ES findings that supported FMD diagnosis. Suggestibility can be utilized in ES to increase its diagnostic certainty. Further application and validation studies are needed to assess its reliability.

Moving Beyond Movement: Diagnosing Functional Movement Disorder

“…74 This battery involves examining: (1) distractibility during contralateral ballistic movement; (2) a tapping task with various frequencies evaluating incorrect performance and tremor suppression, entrainment, or frequency shift; (3) tonic muscle coactivation prior to onset of tremor; (4) increased tremor amplitude with loading; (5) and suggestibility. 74,75 Functional jerks and myoclonus can be evaluated with surface EMG, which will show long and variable burst durations, variability of order of muscle activation, variable and long-latency when stimulus-sensitive, and habituation with repeated stimulation. 75 Additionally, and not specific for FMD per se, EMG-electroencephalography back-averaging may demonstrate the Bereitschaftspotential premovement potential, demonstrating the engagement of voluntary motor pathways which can be supportive of a functional etiology depending on the other conditions being considered.…”

“…74,75 Functional jerks and myoclonus can be evaluated with surface EMG, which will show long and variable burst durations, variability of order of muscle activation, variable and long-latency when stimulus-sensitive, and habituation with repeated stimulation. 75 Additionally, and not specific for FMD per se, EMG-electroencephalography back-averaging may demonstrate the Bereitschaftspotential premovement potential, demonstrating the engagement of voluntary motor pathways which can be supportive of a functional etiology depending on the other conditions being considered. 76 Imaging of the nigrostriatal dopamine system using dopamine transporter single-photon emission computed tomography or positron emission tomography may be helpful for differentiating functional parkinsonism from Parkinson's disease.…”