Approved by the FDA in 1989, spinal cord stimulation (SCS) has become a standard treatment for patients with chronic pain in their back and or limbs who have not found pain relief from other treatments. While the treatment does not work for everyone, most patients who qualify for neurostimulation therapy report a 50 to 70% reduction in overall pain, as well as an increased ability to participate in normal family and work activities. Many patients find that they can decrease or stop taking painkillers or other pain medications after undergoing spinal cord stimulation. Given these benefits, there has been ongoing investment and advances in spinal cord stimulation technology, and many individuals suffering from chronic pain find that neurostimulation positively impacts the quality of their lives.
Electrical Stimulation Blocks the Pain Signals
In general, neurostimulation works by applying an electrical current to the source of chronic pain. This creates a pleasant sensation that blocks the brain’s ability to sense the previously perceived pain. There are two related forms of electrical stimulation commonly used to treat chronic pain:
Spinal cord stimulation (SCS). In spinal cord stimulation, soft, thin wires with electrical leads on their tips are placed through a needle in the back near to the spinal column. The leads are placed through a needle inserted in the back (no incision is required). A small incision is then made and a tiny, programmable generator is placed in the upper buttock or abdomen (under the skin) which emits electrical currents to the spinal column.
Sources of Chronic Pain Treatable with Spinal Cord Stimulation
While spinal cord stimulation and peripheral nerve field stimulation can be used to treat chronic pain from multiple sources, it does not eliminate the source of chronic pain or treats the underlying cause of the pain. Instead, they interfere with the transmission of pain signals to the brain, so the brain does not recognize (or has only limited recognition) of the pain. Sources of chronic pain that spinal cord stimulation may be used to treat include:
- Failed back surgery syndrome: chronic pain after one or more back or neck surgeries to fails to alleviate persistent low back pain, leg pain (sciatica) or lumbar radiculopathy) or arm pain (cervical radiculopathy)
- Reflex sympathetic dystrophy (complex regional pain syndrome): a progressive disease of the nervous system in which patients feel constant burning pain.
- Causalgia: chronic pain with a burning sensation caused by peripheral nerve injury.
- Arachnoiditis: painful inflammation and scarring of the meninges (protective layers) of the spinal nerves
- Peripheral Neuropathy: a constant burning pain of the legs caused by the most distant nerves dying off
It is important to note that the degree of pain relief experienced from spinal cord stimulation or peripheral nerve stimulation varies from person to person. As pain changes or improves, stimulation can be adjusted as necessary. The following pages discuss how spinal cord stimulation works, clinical evidence investigating its efficacy and safety, and advantages and risks of the pain therapy.
The first step in the process is to get a comprehensive evaluation by a spine physician to determine if the patient may or may not be a good candidate for spinal cord stimulation treatment of chronic pain.
Indications and Contraindications for Neurostimulation
Basic criteria that indicate someone might be a candidate for spinal cord or peripheral nerve field stimulation include:
- Chronic back pain with or without leg pain
- Chronic neck pain with or without arm pain
- Prior back surgery (or surgeries) but pain remains (or worsens)
- Peripheral Neuropathy
- Peripheral vascular disease
- Reflex Sympathetic Dystrophy (RSD)
- Refractory angina
- Other treatments have not helped reduce the pain
Although many patients have benefited from spinal cord stimulation and peripheral nerve field stimulation, the treatments are not right for everyone. Importantly, spinal cord stimulation should not be used if a patient has a correctable lesion, which is usually treated surgically.
How Spinal Cord Stimulation Works
Conditions that preclude use of the spinal cord stimulation or peripheral nerve field stimulation include:
- Individuals with a systemic infection
- Women who are pregnant or lactating
- Anyone with a demand type cardiac pacemaker
- Patients who experience discomfort from the sensation of transcutaneous electrostimulation (TENS) units
- Individuals who fail to have a greater than 50% reduction in their degree of pain during a trial of stimulation (see discussion below)
Unlike many other forms of pain treatment, spinal cord stimulation always involves a short trial (lasting a week) conducted with a temporary stimulator to determine whether or not spinal cord stimulation will provide the patient with adequate pain relief. The spinal cord stimulator for the trial period is implanted in an outpatient visit, during which:
- The patient’s skin is numbed with a local anesthetic
- Leads are placed under the skin and attached to a small generator that the patient carries (much like a pager or cell phone)
- Using pre-set programs, electrical currents are emitted in a pattern to target the areas of pain, with the goal of giving the best pain relief possible.
Placement of the trial stimulator generally takes about 10 to 20 minutes, and the patient can go home soon after the leads have been inserted. Preset programs are used to emit electrical currents in a pattern designed to target the areas of pain.
If the patient enjoys significant relief from pain during the trial, a complete system with a generator can then be implanted.
Spinal Cord Stimulator Surgery
For the permanent system, a surgical procedure is required to place the generator in the upper buttock or abdomen.
- The patient’s skin is numbed with a local anesthetic
- Leads are placed under the skin
- A small battery (generator) is surgically placed under the skin in the upper buttock or abdomen.
- The wires are connected so that the entire system is under the skin.
The entire procedure takes 60 to 90 minutes to complete, and is done on an outpatient basis (meaning that no overnight hospital stay is required). The generator and incisions are so small that patients can wear bathing suits, or participate in any other activities without inconvenience or interruption. Nothing is visible on the body, and there is nothing to carry.
Batteries power the system, and depending on the system and the amount of use the batteries will periodically (e.g. every two to five years) need to be replaced through a follow-up surgical procedure. The recent advance of rechargeable batteries in stimulator generators has reduced the need for frequent battery replacement.
There are many clinical studies that show the effectiveness of spinal cord stimulation therapy in reducing pain and allowing people with chronic pain to once again be active. A systematic review of the literature over a 20 year period by Cameron1 concluded that there are over 68 studies (consisting of 3,679 patients) that fulfill acceptable study methodology, reporting on the safety and efficacy of spinal cord stimulation therapy. The author of this literature review concluded that spinal cord stimulation had a: “positive, symptomatic, long-term effect in cases of refractory angina, severe ischemic limb pain secondary to peripheral vascular disease, peripheral neuropathic pain, and chronic low-back pain, and that, in general, spinal cord stimulation was a safe and effective treatment for a variety of chronic neuropathic conditions.”
A literature review by Taylor et al2 found that across a range of medical indications, the initial acquisition costs of spinal cord stimulators are consistently offset by a reduction in post-implant healthcare resource demands and costs.
Additional studies report the safety and efficacy of spinal cord stimulation include:
- Kemler et al3 reported in a randomized, controlled trial (RCT) of 56 patients that spinal cord stimulation can reduce pain and improve health-related quality of life.
- Burchiel et al4 reported in a randomized, controlled trial of 70 patients treated with spinal cord stimulation that 1 year of spinal cord stimulation can result in significant long-term improvement in the pain and quality of life among patients with chronic back pain and extremity pain.
Spinal Cord Stimulation for Failed Back Surgery Syndrome
A study by Kumar et al5 of spinal cord stimulation in 182 patients with post-laminectomy pain reported successful management of pain in 53% of patients.
Futhermore, the study found that after undergoing spinal cord stimulation many patients returned to gainful employment and a more active lifestyle.
- Prior to spinal cord stimulation therapy, only eighteen patients in this group were employed. All eighteen patients reported significant increases in their level of work post spinal cord stimulation.
- Additionally, 22 other spinal cord patients in this group reported entry into gainful employment.
- Furthermore, 6 patients over the age of 60 years reported a significant increase in activities of daily living.
Thus, a total of 46 patients (28% of those in the study) with successful implantation reported a significant increase in daily activities, which is analogous to gainful employment.
In separate research, North et al6 reported in a randomized, controlled trial of spinal cord stimulation versus re-operation (repeat surgery) for failed back surgery syndrome that patients treated with spinal cord stimulation showed a statistically significant advantage over re-operation.
- Cameron T. Safety and Efficacy of Spinal Cord Stimulation for the Treatment of Chronic Pain: a 20-year Literature Review. J. Neurosurgy: Spine, March 2004, 254-267.
- Taylor RS, Taylor RJ, Van Buyten, Buchser E, North R, Baylis S. The Cost Effectiveness of Spinal Cord Stimulation in the Treatment of Pain: a Systematic Review of the Literature. J Pain Symptom Manage. April 2004:370-378.
- Kemler MA, Barendse GA, van Kleef M, de Vet HC, et al. Spinal Cord Stimulation in Patients with Reflex Sympathetic Dystrophy. NEJM. 2000;343:618-24.