Neuromodulation in Chronic Migraine: Evidence and Recommendations from the GRADE Framework

Chronic migraine (CM) affects approximately 2% of the general population and is defined by the persistence of migraine symptoms for at least 15 days per month for at least 3 months. CM is often refractory to common drug treatments and is associated with a significant burden in functions of daily life during ictal phases, productivity loss, and direct costs. Modulation of pain is considered pivotal to reduce its impact and to improve the quality of life among patients with CM. In recent years, neuromodulation in CM has received growing attention; however, there remains no consensus regarding the effectiveness and safety of these procedures. Previous invasive methods such as occipital nerve neurolysis and interruption of the trigeminal dorsal root are not indicated due to high rates of relapsing pain and frequent procedural complications. Although emerging neuromodulation methods, both noninvasive, such as vagus nerve stimulation (VNS), transcranial magnetic stimulation (TMS), remote electrical neuromodulation (REM), and invasive, such as deep brain stimulation (DBS), occipital nerve stimulation (ONS), and high-frequency 10-Hz spinal cord stimulation (HF-10 SNS) have demonstrated promising outcomes in early clinical trials, their use has yet to be integrated into routine clinical practice. In this review, study evidence and strength of recommendations are assessed by the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) system. Other conditions such as therapeutic risk/benefit, direct and indirect costs, use of resources, and patient/clinician preferences are also evaluated.