Progress in neurological surgery
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The field of peripheral nerve stimulation (PNS) is now experiencing a phase of rapid growth in number of patients, number of implanters, number of indications, and procedure types. This, however, appears to be only a beginning of major developments that could revolutionize the field of PNS. It is expected that the progress in PNS will continue simultaneously in several directions as new indications, new stimulation targets and new device designs evolve in the foreseeable future. ⋯ Expanding the number of applications will without question strengthen the field of PNS. The turning point, however, will not occur until sufficient scientific evidence is gathered to unequivocally prove its safety, clinical efficacy and cost-effectiveness, and when PNS applications become officially endorsed through regulatory approval of each indication. Such changes will allow implanters to use approved devices for approved indications--instead of the contemporary 'off-label' use--and at the same time give device manufacturers a chance to market these devices and support education on their appropriate use.
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Peripheral subcutaneous stimulation has been utilized for a variety of painful conditions affecting the abdominal wall, including sequelae of hernia repair, painful surgical scars, ilio-inguinal neuritis. It has also occasionally been shown to be effective in patients with intractable abdominal visceral pain. Since this is a very recent modality, no large series or prospective studies exist. The results, however, are promising and certainly warrant further investigation.
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Cluster headache is well known as one of the most painful primary neurovascular headache. Since 1% of chronic cluster headache patients become refractory to all existing pharmacological treatments, various invasive and sometimes mutilating procedures have been tempted in the last decades. Recently, neurostimulation methods have raised new hope for drug-resistant chronic cluster headache patients. ⋯ Other peripheral nerve stimulation approaches used for this indication are also reviewed in detail. Although available studies are limited to a relatively small number of patients and placebo-controlled trials are lacking, existent clinical data suggest that occipital nerve stimulation should nonetheless be recommended for intractable chronic cluster headache patients before more invasive deep brain stimulation surgery. More studies are needed to evaluate the usefulness of supraorbital nerve stimulation and of vagus nerve stimulation in management of cluster headaches.
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Subcutaneous occipital nerve region stimulation is becoming an important part of the overall treatment regimen for a number of chronic headache syndromes refractory to nonsurgical, medical management. A combination of improved device technology and methodology, further understanding about appropriate indications and achievement of on-label FDA status should support continued use and success of this neuromodulation modality.
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The effect of peripheral neurostimulation has traditionally been attributed to the activation of non-noxious afferent nerve fibers (Aβ-fibers) thought to modulate Aδ and C-fiber-mediated nociceptive transmission in the spinal cord, compatible with the 'gate control theory of pain'. The concept has been extended since its initial description and more recent experimental evidence suggests that the analgesic effects of peripheral nerve stimulation in pain states such as in chronic headache require an interplay of multiple influences. ⋯ Beyond the concept of neuromodulation--decreasing excitation or increasing inhibition--a prerequisite of this arrangement is the convergence of different types of afferent activity and an intact descending modulatory network. In this review, we focus on the functional anatomy, pathophysiological mechanisms and neurophysiological and pharmacological findings elucidating the central mechanisms of peripheral nerve stimulation.