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

Gerard Saranza; Daniel Vargas-Mendez; Anthony E Lang; Robert Chen

doi:10.1016/j.cnp.2021.03.001

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

Clin Neurophysiol Pract. 2021 Mar 17:6:103-108. doi: 10.1016/j.cnp.2021.03.001. eCollection 2021.

Authors

Gerard Saranza^{1

2}, Daniel Vargas-Mendez^{1

3}, Anthony E Lang^{1

4}, Robert Chen^{1

4}

Affiliations

¹ Edmond J. Safra Program in Parkinson's Disease and the Morton and Gloria Shulman Movement Disorders Clinic, Toronto Western Hospital, Toronto, Ontario, Canada.
² Section of Neurology, Department of Internal Medicine, Chong Hua Hospital, Cebu, Philippines.
³ Clinica de Merida, Merida, Yucatan, Mexico.
⁴ Division of Neurology, Department of Medicine, University of Toronto, Toronto, Ontario, Canada.

Abstract

Objective: To evaluate the application of suggestibility in electrophysiologic studies as a tool to increase the diagnostic certainty of "laboratory-supported definite" FMD.

Methods: We retrospectively reviewed the electrophysiologic studies performed in our center on patients with FMD. Recordings where suggestibility was included in the test battery were then selected.

Results: We present three cases with equivocal clinical features, but with findings on electrophysiologic studies that were consistent with "laboratory-supported definite" FMD.

Conclusion: When combined with other tests, demonstration of suggestibility in electrophysiologic studies may increase the accuracy in differentiating functional from organic movement disorders.

Significance: This case series is an essential first step in evaluating the applicability of suggestibility as an electrophysiologic criterion to aid in the diagnosis of FMD. Application in a larger cohort, incorporation in a test battery, and validation studies, including quantitative evaluation of suggestibility, are required to assess the reliability and the added value of this test.

Keywords: EEG, electroencephalography; EMG, electromyography; ES, electrophysiologic studies; Electrophysiology; FMD, functional movement disorders; Functional movement disorders; Functional neurologic disorders; Laboratory-definite; Psychogenic movement disorders; Suggestibility; sEMG, surface electromyography.