Impact of Transcranial Magnetic Stimulation on Functional Movement Disorders: Cortical Modulation or a Behavioral Effect?

Béatrice Garcin,Marie Vidailhet,Thomas Mauras,Emmanuel Roze,Cécile Hubsch,Bertrand Degos,Lionel Naccache,Iulia Iliescu,Francine Mesrati

doi:10.3389/fneur.2017.00338

Abstract

Recent studies suggest that repeated transcranial magnetic stimulation (TMS) improves functional movement disorders (FMDs), but the underlying mechanisms are unclear. The objective was to determine whether the beneficial action of TMS in patients with FMDs is due to cortical neuromodulation or rather to a cognitive-behavioral effect. Consecutive patients with FMDs underwent repeated low-frequency (0.25 Hz) magnetic stimulation over the cortex contralateral to the symptoms or over the spinal roots [root magnetic stimulation (RMS)] homolateral to the symptoms. The patients were randomized into two groups: group 1 received RMS on day 1 and TMS on day 2, while group 2 received the same treatments in reverse order. We blindly assessed the severity of movement disorders before and after each stimulation session. We studied 33 patients with FMDs (dystonia, tremor, myoclonus, Parkinsonism, or stereotypies). The median symptom duration was 2.9 years. The magnetic stimulation sessions led to a significant improvement (>50%) in 22 patients (66%). We found no difference between TMS and RMS. We suggest that the therapeutic benefit of TMS in patients with FMDs is due more to a cognitive-behavioral effect than to cortical neuromodulation.

Highlights

Individuals with functional movement disorders (FMDs) account for 3–20% of all patients seen in movement-disorder clinics [1,2,3]
We found no significant differences between the therapeutic efficacy of root and transcranial magnetic stimulation (TMS) in patients with FMDs, suggesting that magnetic stimulation acts mainly through a cognitive-behavioral effect rather than by cortical neuromodulation
We found no difference between the two modalities of stimulation. These results suggest that TMS does not have a neuromodulatory effect on cortical functioning

Summary

Introduction

Individuals with functional movement disorders (FMDs) account for 3–20% of all patients seen in movement-disorder clinics [1,2,3]. Recent studies suggest a beneficial effect of repeated supraliminal low-frequency transcranial magnetic stimulation (TMS) (i.e., TMS ≤ 1 Hz) on functional motor symptoms [9,10,11,12,13,14]. Focusing on FMDs two studies showed a beneficial effect of supraliminal low-frequency TMS, with a mean improvement rate of 67% [11] and 97% [13]. It is unclear whether the therapeutic benefit is due to cortical neuromodulation, i.e., to changes in cortical excitability and in connectivity between brain areas [15, 16]. The alternative hypothesis is a cognitive-behavioral effect, a therapeutic effect that is linked to suggestion and/or motor relearning

Methods

Results

Conclusion