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Migraine is a common neurological disorder. Approximately 18% of women and 6% of men in the US experience migraine.1,2 Characteristics of migraine include unilateral, throbbing pain of moderate-to-severe intensity that usually lasts for 12 to 24 hours but can persist anywhere from four to 72 hours; frequent associated symptoms include nausea, vomiting, photophobia, and phonophobia.3 To attempt to cope with these debilitating symptoms, a migraine patient often retreats to a darkened room,3 and at least 50% of migraineurs experience substantial functional impairment.4
Current treatments (e.g. acute and preventative medications, physical therapy, nerve blocks, cervical decompression, and surgical interventions directed at eliminating the genesis of pain) help many migraine patients; however, a subset of patients either do not achieve adequate pain relief or cannot tolerate the side effects of typical migraine medications.5 Patients whose migraines are refractory to standard medical treatments sometimes overuse their acute medications; medication overuse is associated with rebound headache, which intensifies and prolongs headache symptoms. The International Headache Society (IHS) defines medication overuse as 10 or more days per month of using triptans, ergotamines, analgesics, combination analgesics, narcotics, or any combination of ergotamines, triptans, analgesics, and/or opioids; or 15 or more days per month of using simple analgesics.6 Estimates for the number of medication overusers range from 5 to 10% of all headache patients and 50% or more of patients who are treated in headache clinics. Evidence supports the emerging view that migraine is progressive in a subgroup of migraineurs, thereby heightening the importance of early intervention.7 As the frequency and magnitude of headaches increase, it appears that central sensitization also develops, lowering the thresholds for triggering migraines and heightening resistance to treatment. Because a significant number of patients have treatment-refractory migraines, alternative treatments are needed. One promising alternative is the electrical stimulation of the occipital nerve via an implantable pulse generator. This technique is supported by clinical practice and a limited but growing amount of literature showing it to be a safe, effective treatment for headache disorders.
Literature on Occipital Nerve Stimulation for Headache
Research is increasing in the area of occipital nerve stimulation (ONS) for the relief of headache disorders, particularly in the population of patients whose headaches do not respond to prior treatments. Many studies of ONS have been directed toward the treatment of occipital neuralgia.8 12 Some additional studies are available for gauging the effect of ONS on migraine13 15 and other types of headache.16 18 Efficacy and safety data in the literature are mostly retrospective analyses, case series, or uncontrolled trials; however, the results of systematic randomized trials to test ONS for migraine will soon be available. The history of peripheral nerve stimulation began with tests of large fiber stimulation that took place in the 1960s.19 ONS is accomplished by means of an asymmetric biphasic electrical pulse applied to the tissue surrounding the occipital nerve, a process that depolarizes the nerve and sends electrical impulses anterograde and retrograde through the nerve, with the anterograde signals ending in the trigeminocervical complex.20,21 The technique appears to mitigate the frequency and severity of migraines in some patients.
Technically, the procedure requires an electrical lead to be advanced through a needle until it is adjacent to the nerve. Patient perception of paresthesia (tingling) is used to optimize placement of the contacts on the lead. The leads are fastened to the fascia after a skin incision, then tunneled to a site in the torso where the implantable generator is placed in the subcutaneous fat. Bilateral leads generally have been found to be superior to unilateral leads in clinical practice.22