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INDICATIONS

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Since the advent of the Gate Control Theory, as proposed by Melzak and Wall, the applications for neurostimulation by stimulation have exploded1. First introduced in the intrathecal space, electrical neuromodulation has progressively been advancing into the periphery, as ablative strategies continue to fall out of favor.

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  • Peripheral nerve stimulation (PNS) is the direct electrical stimulation of named nerves outside of the neuroaxis.

  • Peripheral nerve field stimulation (PNfS) is the stimulation of unnamed small nerves in the vicinity of pain by superficial, subcutaneous lead placement.

  • Unlike SCS that modulates second order nociceptors, PNS and PNfS directly inhibit primary nociceptive afferents.

  • PNS and PNfS suggest that central sensitization can be subverted by peripheral nociceptive suppression.

  • Similar to spinal cord stimulation, therapeutic PNS and PNfS replace the patients pain with a pleasant, therapeutic paresthesia.

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Historically, PNS can be performed via an open surgical or percutaneous technique, well described by Stanton-Hicks. The percutaneous techniques for both PNS and PNfS will be reviewed here, while open techniques will not be discussed. Further, although the scope of vagal nerve stimulation has broadened to include the treatment of neuropathic pain, these strategies have not become commonplace and will not be discussed.

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  • Like spinal cord stimulation, patient selection is crucial to treatment success.

  • PNS and PNfS are indicted for chronic neuropathic pain from peripheral origin.

  • Peripheral nerve and field stimulation lack strong leveled evidence.

  • Percutaneous neuromodulatory stimulation devices are not approved for PNS or PNfS by the FDA and are classified as “off label.”

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Not withstanding, the current indications for PNS include:

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  • Complex regional pain syndrome type II

  • Neuropathic pain from mononeuropathy or plexopathies

  • Headache (migraine, trigeminal neuralgia, occipital neuralgia, supraorbital neuralgia, cervicogenic headache, hemicrania continua)2

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Ideal candidacy for PNS has yet to be determined, as juxtaposed opinions exist. While some advocate a successful nerve block prior to the trial, others contend that a previous successful nerve block is unnecessary. Notwithstanding, a trial prior to implantation is mandatory. With the open technique (not described here), some advocate a direct implant approach in an effort to reduce repetitive procedural morbidity44.

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PNfS indications are less clear, as the mechanism is ill-defined.

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  • Neuropathic and nociceptive pain

  • PNfS alone or in concert with epidural leads for treatment of axial back pain related to FBSS 3

  • Failure or contraindication to conventional and conservative strategies

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PNfS candidacy is even less defined and further debated. Failure of conservative and traditional management of neuropathic or mixed nociceptive/neuropathic pain is typically a prerequisite.

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Patient selection regarding psychometric testing cannot be understated. Poor treatment outcome have been reported in patients with presurgical somatization, depression, anxiety, and poor coping strategies.

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  • Comorbid psychiatric illness significantly reduces interventional treatment success rates.

  • Approximately 20% to 45% of chronic pain patients have accompanying psychopathology.

  • It is paramount ...

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