Peripheral nerve stimulation (PNS) plays an important role in treating chronic refractory pain syndromes that manifest in limited distributions and overlap with areas of neurologic innervation. The process is generally thought to capitalise on the inhibition and activation of pain-related neural circuitry, involving modulation of several neurotransmitters. Preoperative assessment should involve psychological screening of patients with medically refractory pain. Careful patient selection along with treatment trialling is an essential part of the work-up owing to the subjective nature of symptoms. Craniofacial stimulation is one of the more successful indications for PNS owing to the inability to use spinal cord or dorsal root ganglion stimulation to treat pain in craniofacial distributions. Both infraorbital and supraorbital stimulation have been found to alleviate pain in either post-herpetic neuralgia or trigeminal post-traumatic neuropathic pain. Trigeminal branch stimulation is performed using a percutaneous lead insertion technique. Trial implantation can be performed under conscious sedation, but permanent implants would require general anaesthetic owing to tunnelling in the neck to an area where the battery can be safely placed. The percutaneous entry point is marked out behind the hairline and above or below the zygoma pending supraorbital or infraorbital placement respectively. A large gauge needle Tuohy needle is passed subcutaneously under fluoroscopic guidance to the supraorbital or infraorbital region. A contact electrode is passed and connected to a pulse generator to confirm coverage. If trial is successful, a permanent electrode is implanted and connected to a pulse generator usually placed in a subcutaneous infraclavicular pocket. Interestingly, a variety of headache aetiologies respond well to trigeminal branch stimulation including cluster headaches and chronic migraine (with dual supraorbital and occipital nerve stimulation). This paper highlights the role of PNS in patients with chronic refractory pain and could be an option explored in select patients presenting to ENT clinic with this history. 

Evolving Techniques and Indications in Peripheral Nerve Stimulation for Pain.
Banks GP, Winfree CJ.
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Aaron SJ Ferguson

Victoria Hospital, Kirkcaldy, NHS Fife, UK.

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