What is spinal cord stimulation?
Spinal cord stimulation delivers low voltage electrical stimulation to the spinal cord to block the sensation of pain. Electrical stimulation is delivered through an implanted lead superficial to the spinal cord in the epidural space. The lead is connected to an implanted long life battery or a receiver that receives energy from an external battery.
How does SCS work?
According to the “Gate Control” theory of pain, SCS is thought to activate the body's pain inhibitory system. Closure of this gate helps to block incoming pain transmission from the periphery and spinal cord.
How does SCS differ from a TENS (transcutaneous electrical nerve stimulation) unit?
SCS is an internal, implanted system that delivers low voltage electrical stimulation close to the spinal cord. TENS is an external system that delivers electrical energy to the skin. TENS is most effective in acute pain control while SCS is used for chronic refractory pain. Failure to respond to the TENS unit does not predict your response to SCS.
What sort of treatment has been given before considering SCS?
SCS is NOT a first line treatment for chronic pain. Patients will have undergone conservative therapy before SCS is considered.
The following is a list of treatments that have usually been tried before SCS:
1. Medical management with anti-inflammatories, muscle relaxants, low dose anti- depressants and anti-convulsants.
2. Physical therapy, spinal manipulation and TENS units.
3. Nerve blocks and interventional management.
4. Stress management and behavioral programs.
5. Corrective surgery.
6. Long acting narcotics.
What types of conditions does SCS treat?
SCS is used in a variety of chronic pain conditions. The most common indications in the United States include failed back surgery syndrome and complex regional pain syndrome (formerly known as reflex sympathetic dystrophy). Other indications include peripheral vascular disease, refractory angina, radiculopathies, neuropathies, and phantom limb or stump pain. In general, SCS is more effective in patients with nerve pain on one side.
Which patients are considered candidates for SCS?
1. Conservative management as indicated above has been ineffective.
2. Surgery would not be indicated in treating pain.
3. Psychological clearance has been obtained.
4. There are no serious drug use issues.
5. There are no contraindications to implantation.
6. Trial screening has been successful.
What are the contraindications to SCS?
1. Patients who are not able to understand use of the stimulator (dementia, Alzheimer’s disease).
2. Implanted pacemaker, cardioverter/defibrillator.
3. Failure of trial screening.
4. Patients suspected of having an active infection.
5. Patients with weakened immune systems that could put them at greater risk for infections.
7. Patients who are taking blook thinners (and cannot be safely taken off these medications) or those who have bleeding disorders.
What is involved with trial screening?
Trial screening is performed on all patients before permanent implantation. One or two trial leads are placed through the skin into the epidural space. The leads are attached to an external trial screener and stimulation is adjusted to cover the area where the patient feels pain. Lead placement for trial screening is performed as an outpatient procedure. Patients are given intravenous sedation for the procedure. The patient goes home and the stimulation is optimally adjusted for pain control over the next 5-10 days. If the stimulation reduces the patient's pain significantly during the trial period, arrangements are made for permanent implantation. The trial leads are removed at the conclusion of the trial period in the office.
What is involved with permanent implantation?
When trial screening has been successful, appropriate candidates undergo permanent placement of spinal cord stimulator. The pain management physician places the leads and adjusts the stimulation. Intravenous sedation is administered. After it has been determined that the stimulation pattern is adequate to cover the patient's area of pain, the lead(s) is secured into place by the surgeon. It is then connected by another wire to a long life internal battery or radiofrequency receiver. The battery or receiver is usually placed below the beltline just under the skin of the buttocks. The unit is checked in the recovery area. Patients are given pain medications for incisional pain following the procedure.
Who should get the battery or receiver?
The implanted Lithium battery is generally preferred by most patients because they do not have to wear an external generator with battery over the receiver. However, the drawback to the implanted battery and generator is that it can become depleted with heavy stimulator use. Fortunately, replacement of the battery is a minor surgical procedure. Patients who require coverage of two extremities or show high usage of stimulation during the trial may be better candidates for the external system. Patients should discuss this decision throughly with their physician before proceeding as newer batteries have recently been developed and there are many options.
What are the results of outcome studies for spinal cord stimulation?
The following is a list of outcome studies on the success of SCS:
1. Kumar, 1991. 60 patients implanted for failed back surgery, 66% had greater than 50% pain relief. Follow up to 10 months.
2. Devulder, 1991. 69 patients implanted for failed back surgery, 55% had greater than 50% pain relief. Follow up to 8 years.
3. Richardson, 1991. 136 patients implanted for failed back surgery, 67% had greater than 50% pain relief. Follow up average was 45 months.
4. North, 1991. 50 patients implanted for failed back surgery, 53% had greater than 50% pain relief. Follow up was 2.2 years.
5. LaPorte, 1993. 64 patients implanted for failed back surgery, 55% had greater than 50% pain relief. Follow up average was 4 years.
What are the potential risks for spinal cord stimulation?
SCS has historically been a very safe procedure. A study by North etal, Neurosurgery vol. 32, No. 3, March 1993 indicated no major morbidity (spinal cord compression, meningitis, systemic infection). Extraspinal wound infection occurred 5% of the time. Antibiotics are given prior to placement of the leads and strict sterile conditions are employed. Aside from infection, other potential complications include spinal fluid leak, bleeding, migration of the lead, hardware failure, battery discharge and need for replacement, nerve damage and the risks associated with anesthesia and sedation.
What are the restrictions following permanent lead SCS placement?
To reduce the chance for lead migration, for 8 weeks following the procedure, patients should not do the following:
- put arms over head
- bend, stretch, lift more than 5 lbs.
- sleep on your stomach
- climb too many stairs
- sit too long in a chair
- operate riding mowers, power tools or equipment while stimulator is on
- spinal manipulation
Patients should do the following after the permanent placement:
Are there any long term precautions patients with SCS should take?
- sleep with a firm mattress on your back
- log roll out of bed
- physical therapy and walking recommendations under physician supervision
- report any temperature more than 100F, increased back or neck pain, increased pain down an extremity, swelling or redness around the incision site, or changes in stimulator pattern to your physician
- keep appointments so that the stimulator can be checked periodically as determined by our physician
Patients should not subject themselves MRI scanning, ultrasound or diathermy treatment.
They should turn the stimulator off at times when undergoing surgery and when driving a motor vehicle; if electrocautery is used, during radiation therapy, or when near theft detectors, airport security and communications systems. Special consideration is also required for patients who work with high voltage electrical systems or equipment. Spinal manipulation should be avoided because it can cause lead migration, which usually results in stimulator failure.
Is SCS covered by insurance?
SCS is an approved procedure covered by most insurance companies. Pre-authorization is often required. Patients should be aware that Medicare and Medicaid reimbursement may not fully cover the costs to provide the service.