Ipsilateral inhibitory rTMS restores interhemispheric motor cortex balance and reduces phantom limb pain: an exploratory longitudinal nTMS mapping study.
Ghaith Altawalbeh, Eugen Ursu, Filippo Emanuele Colella and 10 others
Two amputees with severe phantom limb pain reported sustained relief after a few sessions of brain stimulation to the unaffected hemisphere, with brain maps becoming more symmetrical.
With only two people and no control group, this is a hypothesis, not a treatment to offer.
Key findings
1Both participants met the IMMPACT threshold for clinically meaningful pain change, sustained over a five-week follow-up: P1 dropped from 7.96 to 2.74 on a 0–10 scale (5.22 points, 66% relative reduction) and P2 from 7.00 to 4.72 (2.28 points, 33% relative reduction).
2Triceps motor-map area in the affected (deafferented) hemisphere shrank by 67% in P1 (416.48 to 137.59 mm²) and 61% in P2 (254 to 98.26 mm²), while the unaffected hemisphere shrank by 15.7% in P1 and 50.9% in P2, indicating bilateral change with a larger proportional effect on the affected side.
3The interhemispheric area gap narrowed from 216 mm² (P1) and 197 mm² (P2) at baseline to 31 mm² and 70 mm² respectively after stimulation, and the authors describe this as convergence toward symmetry.
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What it does not show
Only two participants, so there is no statistical generalisability and no way to separate a true treatment effect from spontaneous fluctuation. No sham-stimulation control, so the cortical and pain changes cannot be definitively attributed to the rTMS rather than to repeated testing, expectation, or natural history. P1 stopped pregabalin entirely before the baseline phase and P2 reduced his dose, so medication withdrawal is a plausible contributor to the pain reduction that the design cannot rule out. P1 received two sessions and P2 received five, and the stopping rule was based on the same pain outcome being measured, which limits any comparison between the two. Follow-up was five weeks; nothing is known about whether the effect lasts months or years. The callosal disinhibition mechanism is inferred from single-pulse mapping data; the authors explicitly note they did not measure interhemispheric inhibition with paired-pulse TMS, so the mechanistic claim is hypothesis-generating, not confirmed. The 50 µV threshold used to define cortical area was not subjected to a sensitivity analysis, so the reported area figures depend on an arbitrary cut-off.
Declared interests
Funded by Technische Universität München (a university). No industry sponsor, no author conflicts of interest declared.
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