PRINTER-FRIENDLY VERSION AT PAINMEDICINENEWS.COM Neurostimulation for Pain TORY MCJUNKIN, MD PAUL J. LYNCH, MD NICOLE E. BERARDONI, MD All rightsFounder, reserved. Arizona Reproduction Pain Specialists in wholeFounder, or Arizona in part Pain without Specialists permission is prohibited.Research Director, Scottsdale, AZ Scottsdale, AZ Arizona Pain Specialists Assistant Professor of Anesthesiology, Clinical Instructor of Anesthesiology, Diagnostic Radiology, MayoCopyright Clinic College © of 2009 Medicine McMahon MayoPublishing Clinic College Group of Medicine unless otherwiseMaricopa noted. Medical Center Rochester, Minnesota Rochester, Minnesota Phoenix, Arizona Dr. McJunkin is a consultant for St. Jude Medical and Boston Scientific. Dr. Lynch is a consultant for St. Jude Medical. Dr. Berardoni has no relevant financial conflicts to disclose. hronic pain is a pandemic that affects approximately 11% of people in the United States, and is estimated to cost Cthe nation $100 billion per year in medical expenses, lost income, and decreased productivity.1,2 Chronic pain interferes with all aspects of life, including personal enjoyment, work, and relationships. Although pain is universal, the etiology of many painful conditions is not well understood, making treatment difficult. PAIN MEDICINE NEWS SPECIAL EDITION • DECEMBER 2009 9 Neuromodulation to sense previously perceived pain. The intensity of the Forms of neuromodulation were used long before the stimulator can be changed, the pattern of the electri- discovery of electricity. The Egyptians first attempted cal field can be varied, and the system can be turned electric stimulation to treat pain as early as 2,500 BC, as on and off as necessary to provide optimal pain relief seen on stone carvings depicting electric catfish being as experienced by the patient. Currently available IPG placed on people.3 The torpedo fish, which also gener- devices are listed in Table 1. Fluoroscopic images of ates electric currents, was used to treat pain and com- device leads are shown in the Figure. mon maladies like headaches and arthritis during the A stimulator trial is performed prior to permanently time of Socrates.4 Electric shocks from these animals implanting the IPG and leads. In a stimulator trial, 1 or canAll reach rights 220 reserved. volts, enough Reproduction to kill a human in adult. whole In or2 inleads part containing without varying permission amounts isof prohibited.electrodes are ancient Greece and Rome, the shocks from the species implanted percutaneously into the epidural space (SCS) Torpedo nobiliana were used as a treatment for gout, or close to pain-generating nerves (PNS) with local anes- headache, and otherCopyright sources ©of pain.20094 McMahon Publishingthetic and Group IV drug unless sedation. otherwise If pain and function noted. improve Grounded in the theory that non-noxious stimuli can by a margin of 50% or more (assessed on a visual ana- reduce noxious pain perception, modern neuromod- log scale [VAS] and through careful monitoring of the ulation works by introducing an electric current near patient over 3-7 days), the patient can receive permanent the source of chronic pain impulses or along pain path- electrodes and the IPG can be surgically implanted. ways. In 1967, Shealy introduced neuromodulation into contemporary medicine; however, the approach did not SPINAL CORD STIMULATION gain popularity for the treatment of pain until the mid- Spinal cord stimulation has proven to be an effec- 1980s.5,6 tive treatment modality in improving daily function and Stimulation is becoming increasingly popular for the quality of life for many patients suffering from severe treatment of refractory pain conditions. It is reversible, neuropathic pain of various causes, most commonly safe, cost-effective, and nonpharmacologic. The most chronic back and limb pain7 (Table 2). However, treat- common forms of stimulation offered to treat pain are ment of chronic neuropathic pain in the region of the spinal cord stimulation (SCS), peripheral nerve stimu- face, neck, head, and low back are challenging for pain lation (PNS), motor cortex stimulation, and deep brain specialists. The pain is typically refractory to many of stimulation. This review focuses on SCS and PNS. the conventional treatment options, including med- Most implantable pulse generators (IPGs) are ical therapies (nonsteroidal anti-inflammatory drugs rechargeable, programmable, and can connect to 1 or [NSAIDs], anticonvulsants, local anesthetics, antide- 2 leads. The IPG produces a low-voltage current, which pressants, and opiates), physical therapy, and nerve creates a sensation that blocks the ability of the brain blocks or ablations.8 Table 1. Comparison of Small, Rechargeable IPG Devices Device, Days Between Manufacturer Size FDA Battery Life Recharge Power Delivery Eon Mini 18 cc 10 yr 121 Constant current St. Jude Medical Precision 22 cc 5 yr 61 Constant current Boston Scientific RestoreULTRA 22 cc 9 yr 54 Constant voltage Medtronic IPG, implantable pulse generator Source: Clinician’s manual for Eon Mini Neurostimulation System. Plano, TX: St. Jude Medical Neurostimulation; 2008. Precision IPG [product brochure]. Valencia, CA: Boston Scientific; 2007. RestoreULTRA [product brochure]. Minneapolis, MN: Medtronic; 2008. 10 INDEPENDENTLY DEVELOPED BY MCMAHON PUBLISHING All rights reserved. Reproduction in whole or in part without permission is prohibited. Copyright © 2009 McMahon Publishing Group unless otherwise noted. Figure. Fluoroscopic images of leads. Images provided by ArizonaPain.com. PERIPHERAL NERVE STIMULATION subcutaneous placement of electrical leads over the Peripheral nerve stimulation is a type of neuro- generalized area of pain (eg, lumbar leads for axial lum- modulation that is becoming increasingly popular for bar pain). An advantage of PNS over SCS is the ability the treatment of many causes of chronic pain and to place the lead directly adjacent to an affected nerve peripheral neuralgias (Table 3). This innovative treat- or in the area of pain, and the ability to provide relief to ment works by delivering low-level electric impulses areas that may be difficult to reach with SCS. close to pain-generating nerves that interfere with the Head, Neck, and Facial Pain perception of nociceptive pain.9 The first through third cervical nerve roots are com- Peripheral nerve stimulation can be further divided monly involved when a patient presents with head, into 2 entities. The first is PNS of an identifiable pain- neck, and facial pain. Spinal nerve roots are not always generating nerve (such as the sciatic nerve in a patient the cause of these cephalad neuralgias and muscle con- with foot pain or the occipital nerves in a patient tractures. Patients who have failed other treatments for with occipital neuralgia). The second type of PNS, their pain have responded positively to PNS. In 2007, peripheral nerve field stimulation (PNfS), involves the Melvin et al conducted a study of patients with occipi- tal headaches. After 4 weeks of receiving PNS for their headaches, 46% of the patients rated the relief as excel- Table 2. Conditions Effectively lent, and at 12 weeks no patients enrolled in the study Managed With Spinal Cord Stimulation7 reported poor pain relief.10 Percutaneous implantation of peripheral stimulator leads has been shown to provide good to excellent results in treating intractable occip- Ischemic vascular ital neuralgia, which has been a suggested trigger for Peripheral vascular disease migraines.8 In a clinical investigation of patients receiv- Refractory angina ing PNS for craniofacial pain, 73% of the participants experienced significant improvement in pain intensity Emerging uses in the first 3 months.10 Chronic pancreatitis Chronic pelvic pain Facial pain (nucleus caudalis stimulation) Table 3. Conditions That May Be Idiopathic neuropathic foot pain Effectively Treated by PNS and PNfS Neuropathic pain Axial pain (cervical, thoracic, lumbar, sacral) Brachial plexus neuropathy Cervicogenic headaches Complex regional pain syndrome Chronic pelvic/testicular pain Peripheral neuropathy Complex regional pain syndrome (I & II), RSD Postherpetic neuralgia Migraines/chronic daily headaches (C1-C3 PNS) Post-laminectomy syndrome Post-laminectomy syndrome Post-thoracotomy syndrome Occipital neuralgia (C1 PNS) Phantom limb pain Radiculitis (cervical, thoracic, lumbar, sacral) PNfS, peripheral nerve field stimulation; PNS, peripheral nerve stimu- lation; RSD, reflex sympathetic dystrophy PAIN MEDICINE NEWS SPECIAL EDITION • DECEMBER 2009 11 Case Report Plan SCS trial with 2 lumbar epidural leads compared with PNS trial with 2 lumbar axial percutaneous leads. Chief Complaint: Chronic Low Back Pain (Without Radiculopathy) Trial History of present illness: The patient is a The patient underwent implantation of a trial 68-year-old man with a long history of lower back spinal cord stimulator with 2 epidural leads in the pain. The patient had been treated with NSAIDs, thoracolumbar region, as well as 2 peripheral field Allnarcotics, rights and reserved. physical therapy,Reproduction as well as inepidurals whole or in part without permission is prohibited. leads in the lumbar region. Two SJM Octrode and facet injections. The patient underwent spinal (St. Jude Medical) leads were advanced from the fusion 2 years ago without significant pain relief. 14-gauge Tuohy needles at the L2-L3 epidural inter- On presentation,Copyright the patient © 2009 describes McMahon the pain Publishing Group unless otherwise