Spinal Cord Stimulation Treatment
Performed by Top Pain Management Doctors in San Antonio, Texas
For more than 40 years, spinal cord stimulation (SCS), where electrical pulses are delivered to targeted areas of the spinal cord, has been used to successfully manage pain in a wide variety of conditions1, 7, 13, 18. SCS is usually indicated for peripheral neuropathic pain syndromes in which nerves outside the brain and spinal cord continuously convey pain stimuli to the brain, and cases of ischemic pain in which lack of blood flow to tissues induces pain8.
While the exact physiologic mechanism underlying SCS is unknown, use of the technique is predicated on the theory that non-painful, sensory stimuli (such as electrical pulses) transmitted over the spinal cord can interfere with nearby traveling pain signals; this is known in medicine as the gate ‘control’ theory of pain2, 6, 18.
SCS is generally reserved as a last resort for patients who’ve been unsuccessful with alternative, and more conventional, approaches to pain management, including medications, physical therapy and nerve blocks3, 5, 13, 18.
The spinal column consists of several bones, called vertebrae, which are stacked atop one another from the pelvis to the base of the skull, forming a protective channel for the spinal cord21. There are 33 of these vertebrae divided into five regions: (1) cervical, which are found in the neck closest to the skull (identified as C1-C7), (2) thoracic, found along the upper back (identified as T1-T12), (3) lumbar, found along the lower back (identified as L1-L5), (4) sacral, which are contiguous with the pelvis or hip (identified as S1-S5), and (5) coccygeal, which are fused as the tailbone.
The spinal cord is part of the central nervous system and contains many tracts of nerves, communicating between the brain and the rest of the body. Similar to the vertebrae, the spinal cord is also divided into cervical, thoracic, lumbar and sacral segments; the cord is slightly shorter than the spinal column, such that the cord and column levels don’t exactly align, but rather the spinal cord terminates in nerve roots that traverse to their respective vertebral level. The spinal cord is composed of three meningeal layers, or protective sheaths that envelop the nerves of the spinal cord21. The thick, fibrous external dura mater covers a mesh-like, cushioning arachnoid mater, which in turn covers a thin, internal pia mater. The space between the dura mater and the bone comprising the vertebral canal is termed the epidural space and is the area in which the electrodes used in SCS are placed.
Device and Implantation
Today’s spinal cord stimulators are similar to pacemakers, in that they are implanted devices that intermittently generate an electrical pulse to adjacent tissues2. For pain management, these devices are typically implanted in the epidural space, just behind the spinal cord, of the spinal column3, 18. These devices stimulate what’s known as the dorsal column of the spinal cord, a tract of nerves which carries sensory information related to tactile stimulation and self-awareness of movement and position (proprioception) to the brain3. When the dorsal column of the spinal cord is stimulated, it is thought to interfere with the conduction of pain through the adjacent spinothalamic nerve tract via a process termed collateral inhibition3.
Even though SCS has been around for many years, technological advances have led to the use advanced electrode arrays that allow for stimulus of broader areas of tissue, more precise targeting, improved battery life of pulse generators and smaller device sizes2, 8.
Generally a trial of SCS is conducted before permanent implantation of a spinal cord stimulator, to test the effectiveness of stimulation in different regions and to identify patients most likely to benefit from SCS8, 18. During the trial, an electrical lead, connected to an external, cylindrical electrical pulse generator, is inserted through the skin to the epidural space3, 7. Once activated, the patient may feel parasthesias (numbness, tingling) and/or a reduction of pain if the device is properly placed. Trial ‘success’ is defined as a 50% reduction in pain, a reduced need for pain medications, tolerance of parasthesias, and subjective overall patient satisfaction with stimulation8, 13. Depending upon the trial results, permanent placement of a spinal cord stimulator can be performed by an experienced pain management specialist or neurosurgeon one month after a successful trial3, 18.
For permanent implantation, a cylindrical SCS electrode can be implanted through the skin similarly to the trial lead, or a wider paddle electrode can be implanted via open incision and laminectomy (the removal of a portion of vertebral bone to access the spinal cord)7, 18. During the procedure, the patient may be placed under local or general anesthesia. The surgeon guides implantation of the device using fluoroscopy, a real-time x-ray that allows visualization of device movement relative to surrounding tissues3, 18. Subsequently, a pulse generator is connected to the electrode and implanted internally under the skin of the lower back or abdominal wall. The electrode and pulse generator are connected by a subcutaneous tunnel, or channel under the skin3, 8. The strength of stimulation can then be adjusted via remote control3.
For low back and leg pain, the device is usually inserted into the epidural space and adjusted upward toward the thoracic spinal cord levels (T9-T11), to which sensory nerves insert from the lumbar vertebral levels3.
Indications for Treatment
SCS is indicated for the treatment for a variety of painful conditions, and is under investigation as a potential treatment for many more. The following conditions have strong evidence advocating for the effectiveness of SCS:
Chronic Regional Pain Syndrome (CRPS)
CRPS is a painful chronic and progressive neuropathic disease for which no proven cure currently exists11. CRPS leads to severe pain, swelling and changes in the temperature, color and texture of the skin, and can lead to disability and an inability to work11, 18.
Two types of CRPS exist12:
CRPS type 1, also known as reflex sympathetic dystrophy, causes these symptoms after minor trauma but with no evidence of discernible nerve lesions
CRPS type 2, known as causalgia, features these symptoms associated with apparent nerve damage
The biological basis for CRPS isn’t well understood, however onset of the syndrome typically occurs following trauma or surgical procedure on an extremity. Treatment focuses on slowing and managing the disease via physical therapy, medications and surgical intervention, such as SCS, which has been shown to be an effective component of CPRS symptom management3, 8, 12.
In one study, which followed up with CRPS type 1 patients having previously received both SCS and a physical therapy regimen for five years suggested promising initial improvement in pain compared to patients receiving physical therapy alone; however the pain improvement diminished over time11. Despite the diminished effect, however, most SCS patients in the trial indicated satisfaction with the treatment. Another study reported greater than 50% pain reduction following the SCS procedure, with 60% of patients discontinuing oral pain medications8. Yet another study found significant reduction in long-term pain for pts with CRPS type 22.
Another systematic review found that amongst over 500 patients treated with SCS for CRPS, 67% had greater than 50% pain relief and significantly improved quality of life, concluding that SCS combined with physical therapy was am effective and cost-effective approach to the management of CRPS3, 18.
Failed back syndrome (FBS)
FBS (also known as failed back surgery syndrome, or post-laminectomy syndrome) refers to chronic neuropathic pain that can occur after spine surgery13. FBS is the most common cause of chronic neuropathic pain in the United States, and is the most common indication for SCS therapy 13, 14, 18. Patients suffering from this syndrome often experience pain, particularly chronic, ‘burning’ lumbosacral and leg pain following a laminectomy procedure, as well as disability, diminished quality of life, and high healthcare costs2, 10, 14.
There are two primary treatment modalities for FBS; re-operation and SCS. In general, when compared to SCS, repeated back surgery is associated with declining success rates and higher costs as more procedures are performed13, 19. SCS has shown better promise for the long-term management of FBS.
SCS is indicated for treatment of FBS following lumbar and cervical spine surgery when all other conservative treatment options have failed2, 8.
One study has shown that for patients with FBS and leg pain, SCS in conjunction with conventional medical pain management led to more than 50% pain reduction in the lower extremities10. Secondarily, these patients reported improved quality of life, functional ability, and a reduced need for pain medications compared with patients receiving conventional pain management therapies alone. Another study followed patients two years after SCS implantation for FBS, and reported sustained pain relief, improved functional capacity and patient satisfaction with SCS treatment14.
A systematic review of medical literature suggests a moderate-to-strong recommendation for the use of SCS to treat FBS on a long-term basis13. Further, SCS appears to offer a substantial cost savings when compared to more conventional pain management18.
Refractory angina refers to chest pain caused by poor blood flow to the heart (angina) which is inadequately managed by more conventional therapies such as medications, angioplasty, and bypass surgery15.
SCS has been shown to be an effective and safe treatment option for the treatment of angina unresponsive to more conventional treatments, and offers an alternative to other invasive treatment methods such as bypass surgery or laser revascularization3, 15, 18. In fact, some studies have even shown SCS to be as effective in pain management and symptomatic relief of refractory angina as coronary artery bypass surgery. One study in particular reported success in reducing the severity and frequency of angina attacks in 80% of patients, with improvement in functional status and quality of life6.
Refractory pain secondary to peripheral vascular disease
Peripheral artery disease refers to the narrowing and hardening of arteries that supply blood flow to the extremities, notably the legs and feet. This decreased blood flow can lead to ischemic pain, parasthesias, and impaired wound healing of affected areas. SCS has been observed to induce pain relief, increased skin temperature and healing of small ulcers in patients with peripheral vascular disease3, 18.
Post-herpetic neuralgia refers to severe nerve pain as the result of Herpes Zoster infection of neuronal tissue. It is one of the symptoms of shingles. Preliminary studies have shown SCS to be an effective treatment modality for post-herpetic neuralgia, with as many as 82% of patients obtaining long term relief of intractable pain3, 18.
One study reported the use of SCS for the treatment of pain in frostbite patients, with the secondary benefit of lowering the level at which lower extremity amputations had to be performed4.
Chronic, visceral abdominal pain
Chronic visceral abdominal pain refers to recurring pain felt deep within the internal organs of the abdominal cavity, and can result from inflammation, disorders of the spine and organs, or can have no medical explanation. SCS has been shown to be effective for the treatment of visceral abdominal pain, as measured by patient reported pain improvement and patients’ decreased need for opioid based pain relievers17, 20.
Arachnoiditis refers to inflammation and potential scarring of the arachnoid layer of the spinal cord sheath due to trauma, compression or infection of the tissue13. SCS is currently the treatment of choice for long-term management of pain associated with this condition.
Diabetic neuropathy refers to damage to peripheral nerves due to high blood glucose (‘sugar’) levels. In some cases this nerve damage can manifest as pain, particularly in the lower extremities. In many studies, SCS has been shown to offer an effective and relatively safe therapy for chronic diabetic neuropathy16.
Inducing cough reflex
Patients with spinal cord injuries that weaken or paralyze the respiratory muscles can have difficulty breathing, and often lose their cough reflexes putting them at an increased risk for developing respiratory tract infections such as pneumonias9. One study reported that SCS was effective in stimulating expiratory muscles under operator control, thus manually inducing a cough reflex in a paralyzed patient, presenting yet another possible treatment indication for SCS.
Many studies have been performed investigating the efficacy of SCS, each for a specific condition as outlined above. The preponderance of findings from these studies suggests that for these conditions in general, about half of study participants experienced at least 50% pain relief within 5 years of device implantation2. SCS is also being investigated as a potential treatment modality for other conditions as well, including amputation stump pain, phantom limb pain, spinal cord injury, and Multiple Sclerosis3, 9.
As with any surgical procedure, SCS is not without risk. Studies have reported complication rates anywhere from 30-60%, however most complications are relatively mild2. The most common complications are infection (ranging from 3-6% amongst all studies) and migration of the epidural electrode away from the area targeted at implantation (ranging from 15-27%) 2, 3, 8, 10. Other complications include electrode displacement requiring repeat surgery, wound healing difficulty at the site of implantation, and battery failure. For some patients, despite an effective trial, implantation of a spinal cord stimulator may fail to provide any pain or symptom relief at all3. Serious complications, such as spinal cord compression or epidural abscess are rare3.
SCS should be avoided in cases of severe depression, existing infection, coagulopathies (blood clotting disorders), and for patients unable to appropriately operate and understand the device3, 18.
Compared with repeat surgical procedures (to treat FBS, for example), SCS tends to have fewer major adverse effects associated with treatment, and these complications are declining as devices and implantation techniques improve with time and research2.
SCS represents an effective therapy of last resort for a variety of painful conditions, particularly for CRPS, refractory angina, and FBS18. Many studies have shown that SCS is a relatively safe procedure, with most complications being minor and correctable10. SCS offers the possibility to manage painful conditions while reducing the need for pain medications and avoiding associated side effects, improve quality of life for patients suffering from debilitating conditions, and improve function to the point of resolving disability18. SCS has been shown to be as, or more, cost-effective as many alternative and more conventional therapies, and holds great promise as an emerging treatment for additional painful disorders.
References/ Journal Articles
Spinal Cord Stimulator Implants – PainDoctor.com
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2 Mehta, P.; Rathmell, J. (2008). Chronic Pain Management. Miller: Basics of Anesthesia, 6th Ed. MD Consult Web site, Core Collection.
3 Zhou, Y. (2008). Principles of Pain Management. Bradley: Neurology in Clinical Practice, 5th Ed. MD Consult Web site, Core Collection.
4 Freer, L.; Imray, C. (2011). Frostbite. Auerbach: Wilderness Medicine, 6th Ed. MD Consult Web site, Core Collection.
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12 A.D.A.M. Complex regional pain syndrome. Retrieved from: http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0004456/. Accessed March 10, 2012.
13 Frey, M.; et al. (2009) Spinal Cord Stimulation for Patients with Failed Back Surgery Syndrome: A Systematic Review. Pain Physician. Vol. 12, 379-397.
14 Kumar, K.; et al. (2008) The effects of spinal cord stimulation in neuropathic pain are sustained: a 24 month follow up of the Prospective Randomized Controlled Multicenter Trial of the effectiveness of spinal cord stimulation. Neurosurg. Vol. 63(4), 762-770.
15 Taylor, R.; et al. (2009) Spinal cord stimulation in the treatment of refractory angina: systematic review and meta-analysis of randomized controlled trials. BMC Cardiovascular Disorders. Vol. 9(13), 1-13.
16 de Vos C.; et al. (2009) Effect and safety of spinal cord stimulation for treatment of chronic pain caused by diabetic neuropathy. J Dia Comp. Vol. 23(1), 40-45.
17 Kapural, L.; et al. (2010) Spinal Cord Stimulation for Chronic Visceral Abdominal Pain. Pain Medicine. Vol. 11(3), 347-355.
18 Epstein, L.; Palmieri, M. (2012) Managing Chronic Pain with Spinal Cord Stimulation. Mt Sinai J Med. Vol. 79(1), 123-132.
19 North, R.; etal. (2007) Spinal Cord Stimulation versus Reoperation for Failed Back Surgery Syndrome: A Cost Effectiveness and Cost Utility Analysis Based on a Randomized, Controlled Trial. Neurosurgery. Vol. 61(2), 361-369.
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21 Hansen, J. (2010). Back. Hansen: Netter’s Clinical Anatomy, 2nd Ed. MD Consult Web site, Core Collection.