Rationale for electrical parameter determination in external trigeminal nerve stimulation (eTNS) for migraine: A narrative review

Background Migraine is a primary headache disorder involving dysregulation of central and peripheral pain pathways. Medical treatment is often limited by drug side effects, comorbidities and poor compliance. This makes neuromodulation an ideal option for migraine treatment. Cefaly® is a transcutaneous electrical neurostimulator designed specifically for migraine treatment. It results in external trigeminal nerve stimulation of the supraorbital and supratrochlear nerves. External trigeminal nerve stimulation is effective for acute and preventive migraine treatment and may result in normalization of dysregulated pain pathways. Objective Our objective was to provide a narrative review of the neuroanatomical and pathophysiological basis of external trigeminal nerve stimulation for migraine treatment and to provide the rationale behind the choice of the electrical parameters used for external trigeminal nerve stimulation. Methods We reviewed external trigeminal nerve stimulation clinical trial publications, basic science neurostimulation literature, publications describing pathophysiological mechanisms in migraine, and documentation used in the application for the Food and Drug Administration approval of external trigeminal nerve stimulation. Results The electrical parameters used for external trigeminal nerve stimulation were chosen to maximize safety and efficacy. Critical parameters include generator characteristics, pulse shape, pulse duration, pulse frequency and session duration and frequency. We explain the rationale behind determination of each parameter. There is evidence of dysregulated central and peripheral pathways in migraine and evidence that external trigeminal nerve stimulation may normalize function of these pathways. Conclusion External trigeminal nerve stimulation is a safe and effective Food and Drug Administration-approved option for the acute and preventive treatment of migraine. The electrical parameters were optimized specifically for external stimulation of the trigeminal nerve to maximum safety, comfort and efficacy.