What is Neurostimulation?
The use of electrical stimulation to relieve pain began in ancient times with the placement of torpedo fish directly onto painful body parts. Since then, the application of electrical stimulation to the body for pain relief has become much better and more sophisticated. In 1989, spinal cord stimulation (SCS) was approved by the Food and Drug Administration (FDA) as a treatment for chronic pain. Since that time, SCS has become a standard of care for patients with neuropathic chronic back and limb pain (nerve injury with abnormal nerve function producing pain). New technology has allowed for the development of neurostimulators that can allow patients with chronic back pain to reduce or eliminate their need for pain medications and return to comfortable, productive lives.
How does stimulation work?
In spinal cord stimulation, a tiny programmable generator and electrical leads are implanted beneath the skin. Small electrical currents are applied to the areas of the spinal cord involved in pain. These electrical impulses interfere with the transmission of pain signals to the brain and relieve pain without causing the side effects that medications can cause. Acceptable mechanism of action (theory) is stimulation of large pain fibers blocks transmission of small pain fibers which care most of the unpleasant pain signals. This very is called “the gate control theory”. This is similar to the relief felt by rubbing an area after getting an injury. A pleasant tingling sensation is substituted for the pain and blocks the brain’s ability to sense pain in the stimulated areas. The electrical impulses can be targeted to specific locations and, as pain changes or improves, stimulation can be adjusted as necessary.
What is the goal of spinal cord stimulation?
The goal of neurostimulation with SCS is to achieve significant or total relief from back pain and to be able to return to a happy productive lifestyle. While this therapy does not work for everyone, most patients with SCS are able to report a 50-90% reduction in their overall pain and are able to decrease or completely taper off narcotic painkiller medications. With successful SCS, patients can function during normal activities, return to work, and fully participate in family and community life. The current guideline for placement of this technology requires a psychological clearance by most insurances including Medicare. This evaluation is necessary in order to make sure that the patient is psychologically stable to undergo the trial and placement.
What is the SCS trial? How is this done?
In spinal cord stimulation a trial is first performed using temporary epidural leads. It is similar to having a labor or pain management epidural steroid injection with the catheter. Instead of a catheter, electrical leads are placed.
In the trial phase, Dr. Dominguez first numbs the skin using a local anesthetic. Soft, thin wires with electrical leads at the tip are placed through a needle (without any incision) into the back near the spinal column. Dr. Dominguez determines the best location of the electrical leads based on the individual patient’s pain. The leads are then connected to a special external programming device that can be used to program the electrical current in a pattern to exactly target the painful areas for the best relief possible. The generator is similar to a pager or cell phone. If the SCS trial is successful, a complete permanent system with a generator is implanted at another time.
If trial is successful, greater than 50% decrease in pain level and decrease in medication utilization, a permanent generator is placed 2- 4 weeks after the trial. A small generator is surgically implanted beneath the skin in the upper buttock or abdomen. The leads for the permanent system can be inserted the same way as in the trial. The wires are then connected and the entire system is implanted beneath the skin. Nothing is visible on the body.
Why not implant the permanent system immediately?
To make sure the patient will benefit from SCS, a temporary system is implanted and tried for a few days or a week. There is no reason to place a permanent stimulator if it is not going to work. This process will avoid an unnecessary minor surgical procedure.
How long will the system last?
Many systems today have rechargeable batteries that can easily be recharged at home. Battery life time are anywhere from 7 to 10 years depending on the energy requirements.
Using a programming device outside the body, the system can be programmed in a way similar to using a remote control to adjust a television. The area or intensity of stimulation can be changed, and the system can be turned on and off or adjusted to provide the best pain relief. To recharge the batteries, the patient places the recharging unit over the skin where the generator is implanted. Batteries may require recharging several times a month. Programming is initially done at the physician’s office, and patients can learn how to control the stimulation on their own at home to adjust it to their pain.
The latest technology provides coverage of different pain types (sensations) simultaneously (i.e. burning, aching, and stinging). It is referred to as multiple independent constant current technologies (MICC). Using this technology, each electrode lying over the spinal cord can be controlled independently. Currently, this technology is available with an added feature; the patient can program the stimulator with user-friendly software.