Transcranial magnetic stimulation as a treatment for functional (psychogenic) upper limb weakness

Objective: There has been a recent resurgence of interest in physical treatments for functional motor disorders (FMD) including Transcranial Magnetic Stimulation (TMS). This pilot study aimed to test the effectiveness of a single session of motor cortex TMS as a treatment for functional upper limb weakness.

Methods: Ten subjects with a diagnosis of functional upper limb weakness were randomised to immediate (n=7) or delayed (3months) (n=3) TMS treatment. Median age was 35 (range 23-52) and median symptom duration was 2.3years (range 5months - 20years). 46-70 single pulses were applied to the motor cortex at 120-150% motor threshold. We used a verbal protocol designed to standardized the effects of suggestion. Primary outcome measures were self-reported symptom severity, grip strength and tapping frequency immediately after treatment, and symptom severity and disability (SF-12 and Modified Rankin Scale (MRS)) after 3months.

Results: There was a small significant reduction in symptom severity immediately after treatment, but no improvement in grip strength or tapping frequency and no change in symptom severity, SF-12 or MRS 3months after treatment. Small numbers precluded comparison of immediate treatment with delayed treatment. Four of eight subjects responding to three-month follow-up reported late-onset adverse effects.

Conclusion: This pilot study suggests limited benefits for TMS as a one-off non-neuromodulatory treatment for stable chronic outpatients. TMS may still have a role alongside more intensive multidisciplinary therapy input, or in patients with severe deficits where the possibility of normal movement can be hard to demonstrate.

Trial registration: NCT02102906.