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

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

Gerard Saranza  1   2 , Daniel Vargas-Mendez  1   3 , Anthony E Lang  1   4 , Robert Chen  1   4
Affiliations

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

Gerard Saranza et al. Clin Neurophysiol Pract. .

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.

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Conflict of interest statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Fig. 1
Fig. 1
Case 1. Demonstration of suggestibility in functional tremor. A. Deep palpation on the right ankle markedly increased the tremor amplitude, which was then reduced back to baseline upon cessation of deep palpation. B. Application of a vibrating tuning fork on the right knee increased the tremor amplitude continuously throughout the recording, even with removal of the instrument in between trials. EDB = extensor digitorum brevis; GAS = gastrocnemius; HAM = hamstring muscles; Lt = left; QUADS = quadriceps femoris; Rt = right; TA = tibialis anterior.
Fig. 2
Fig. 2
Case 2. Demonstration of suggestibility in functional movement disorder resembling tics. Application of a vibrating tuning fork (A) and deep palpation (B) on the left shoulder induced the slow, writhing movements. Lt = left; PARA = paraspinal muscles; Rt = right; SCM = sternocleidomastoid; Sp.Cp. = splenius capitis; TRAP = trapezius.
Fig. 3
Fig. 3
Case 3. Demonstration of suggestibility in functional jerks. The frequency of the jerky movements was significantly reduced with the application of a vibrating tuning fork on the glabella (A) and occiput (B). BRACHIO = brachioradialis; Lt = left; Rt = right; TRAP = trapezius.
See this image and copyright information in PMC

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