Electromagnetic neuromodulation for chronic pain: historical context, contemporary modalities, and evidence gaps

Electromagnetic neuromodulation is increasingly used as an adjunct or alternative to pharmacologic therapy for pain, with several approaches cleared for select indications and many others under active investigation. We review implanted neuromodulation approaches (intracranial and spinal), vagal neuromodulation, noninvasive central/cranial neuromodulation, peripheral neuromodulation, and hybrid/multimodal approaches, with a primary focus on chronic pain management and brief coverage of selected acute-use indications (e.g., primary headache disorders) where relevant. Beyond summarizing individual modalities, we highlight the recurring patterns that have shaped the evolution of pain neuromodulation. For each modality, we summarize putative mechanism of action, typical stimulation paradigms, and key strengths and limitations of the clinical evidence, emphasizing sources of heterogeneity that complicate cross-study comparison and translation. We conclude by outlining priorities for the field, including more rigorous trial design, standardized reporting of stimulation parameters and outcomes, and clearer indication-specific evidence to support clinical translation.