Scrambler Therapy for Chronic Neuropathic Pain: Why the Evidence Base Has Not Converged, and What Standardization Would Require

Scrambler therapy (ST) is a non-invasive transcutaneous electroanalgesic technique proposed to deliver synthetic “non-pain” information rather than conventional gate-control stimulation. Despite two decades of favorable clinical signals and few reported serious harms, guideline endorsement remains limited and quantitative syntheses diverge. This narrative review examines why the ST evidence base has not converged and what standardization would require. We identify six recurrent structural problems: an unresolved sham-control paradox, operator dependence, device heterogeneity, an unresolved medication interaction, outcome timing, and post hoc attribution of negative results to protocol deviation. A Korean national health technology reassessment independently reproduced comparator-dependent effect estimates and very low certainty. Public Health Insurance Review and Assessment Service (HIRA) price disclosure records further show that institutions reporting the relevant administrative item increased from 189 in 2021 to 871 in 2026, while the public record cannot identify the device used. As preliminary proposals rather than validated standards, we offer a 22-item reporting set, a conceptual phenotype-stratified dismantling trial, and a prospective registry model. We argue that intervention definition, delivery fidelity, and trial architecture limit the interpretability of the evidence and should be standardized before additional large confirmatory trials; standardization would make results interpretable, not predetermine their direction.