Repetitive transcranial magnetic stimulation in functional motor disorders: A systematic review of effects and targets.

OBJECTIVE

To evaluate the effectiveness, safety, and potential mechanistic implications of repetitive transcranial magnetic stimulation (rTMS) in adults with functional motor disorders (FMD), focusing on possible phenotype-specific responses and stimulation protocols.

METHODS

Seven databases were searched from inception to July 2026. Randomised and non-randomised interventional studies were included. Risk of bias and evidence certainty were assessed using PEDro, RoB 2, JBI tools, and GRADE. Because of substantial clinical and methodological heterogeneity, findings were synthesised qualitatively.

RESULTS

Fourteen studies were included. The primary motor cortex was targeted in 11 studies. Functional tremor showed the most consistent evidence with inhibitory stimulation: one small sham-controlled trial found a significant group-by-time effect on tremor severity (p = 0.007), while an uncontrolled prospective series reported 40 % reduction in postural tremor amplitude (p = 0.05). Evidence for functional weakness was conflicting: excitatory M1 stimulation increased objective strength by 25 % versus 10 % with sham (p = 0.004), whereas the largest inhibitory sham-controlled trial found no benefit (p = 0.80). No severe adverse events were reported, but safety reporting was incomplete. GRADE certainty was moderate for tremor and very low for all other outcomes.

CONCLUSIONS

Current evidence is insufficient to establish the efficacy of rTMS in FMD or to recommend phenotype-specific protocols. Preliminary findings support further investigation of inhibitory stimulation for functional tremor, whereas evidence for excitatory stimulation in functional weakness remains uncertain.

SIGNIFICANCE: The possible interaction between phenotype and stimulation direction is hypothesis-generating. rTMS should currently be considered an experimental, context-sensitive adjunct within multidisciplinary care, pending adequately powered phenotype-stratified sham-controlled trials. Prospero Registration Number: CRD420251250969.