Surgery to Implant the Neuromodulator
The permanent implantation of a neurostimulator system is different in some ways relative to the trial stimulation procedure.
Although percutaneous leads are commonly employed for permanent implants with the spine for pain treatment, Dr. Barolats' preference has been, over the years, to implant the so called "paddle leads". Our team's experience has been that, even though in many instances percutaneous leads can provide a very acceptable stimulation, paddle leads provide a superior (although surgically more involved) construct for long-term stimulation.
The difference in performance lies in the physical characteristics of the two types of leads. The leads that are threaded through the needle in the trial (percutaneous leads) are round and thin about 2 mm wide. Their electrical contacts are circumferential around the lead. This means the electrical energy is dissipated 360 degrees around the lead which can disperse energy in nonessential directions. This will waste energy in stimulating tissue unnecessarily for the desired pain treatment effect (spinal cord, nerve roots). The paddle shaped electrode is used in permanent spinal cord stimulation, as opposed to the percutaneous lead that is shaped like a wire. The silastic coated paddle electrode is insulated on one side to prevent discharge of current to tissues on that side. This allows the energy to be uni-directional so the energy is more precisely focused on the target nerves.
There is another advantage of the paddle electrode over the wire lead and that is stability. Due to the fact that the paddle has a wider shape, there is a greater surface area for scar to form over it. This reduces the chance of the electrode migrating. Lead migration, a known untoward event in neurostimulation procedures, occurs more frequently with percutaneous leads than with paddle leads. When this occurs the stimulation may stop or be greatly reduced. Anything we can do to prevent this increases the chance for long-term success for pain treatment using the neurostimulator (neuromodulation treatment).
Since the paddle lead is wider, it requires a slightly longer incision, and a small amount of bone must be removed to gain access to the spinal canal where the paddle is inserted. After it is place the wires from the electrode are hooked up to an external stimulation unit. The patient is then awakened during the surgery with the incisions open and anesthetized. During that intraoperative wake up time, we ask the patient questions to insure the stimulation is perceived in the correct region of their body. Once that is established, the electrode is stimulating correctly then the wire is tunneled under the skin with a hollow device (not unlike "fishing wire"). When the wires reach the implanted pulse generator (IPG), they are connected. The IPG is then checked to insure the wires have good current flowing. An incision is made as wide as the IPG and a pocket is formed under the skin. The IPG connected to the electrode wires is then placed into the pocket. The IPG can be located in several different locations on the body. It is most commonly placed near the waist line in the back depending on what the patient prefers. Other common areas of implant are the abdomen or the anterior chest area, just below the collar bone. The decision for the IPG location on the body is made in the preoperative planning phase. After the IPG is placed, the incisions are closed with dissolvable sutures and a small dressing.
In the recovery room the stimulator representative checks the connection again to see if the stimulation is in the correct area. The following day when the patient is more alert, the representative will come in to program the stimulator settings and educate the patient on the use of the remote control device. These settings control the intensity and the pattern of stimulation customized to the patient's needs. The patient is educated on the remote control use to control the choice of their programs and the stimulation intensity of those programs. As long as the patient has a stimulator, they have technical support available by a company phone number. After all this, hopefully this will provide long-lasting reduction in pain for the patient. Dr. Barolat has patients who have had their implants for over 20 years.
At Barolat Neurosciences in Denver, we are here to provide our patients with leading care and expertise in the use of neuromodulation for the treatment of chronic debilitating pain. We also are here to provide answers to frequently asked, common questions.
In regards to pain, when should a person consider neurostimulation surgery for pain treatment?
When a person has had debilitating pain for more than 6 months despite many other treatments, then one can be considered for neurostimulation surgery. These other treatments may include physical therapy, medications, spine surgery, cortisone injections, transcutaneous nerve stimulation and acupuncture.
What other testing has to be done to be a candidate for neurostimulation procedures?
Most insurance companies and neurostimulation pain professionals require a screening psychological exam to rule out any serious psychological issues that could interfere with the success of the procedure. The majority of people who suffer from chronic pain have experienced depression, frustration, and anger. The goal of the psychological evaluation is to make sure that these issues are not of such a magnitude to jeopardize the outcome of the neurostimulation procedure. Of course we also want to make sure that there are no significant psychiatric disorders or cognitive issues that would nullify the efficacy of the modality.
How do we know it will work?
A patient will undergo a 7-10 day trial with a temporary stimulator inserted. This will be powered by an outside generator source. If the patient experiences a good response, which we consider greater than 50% reduction in pain, then a permanent stimulator lead or electrode with an IPG (implantable pulse generator) are implanted for permanent use. The reports of satisfactory pain relief vary from 40-80% success rates. What determines the success is highly variable from patient to patient. That is the reason for a trial to be performed first.
How big is the IPG (device) or battery unit?
The smallest IPG is about the size of 3 silver dollars stacked on top of each other.
How long does the battery last and how do you replace it?
The batteries are rechargeable through the skin and may last 5-7 years, depending on the power demand for that patient's stimulation requirements. To replace the battery is a minor outpatient procedure performed under local anesthetic and sedation. That procedure takes about 30 minutes.
How do I control the stimulator?
You may have 2-5 different stimulator programs to choose from. In addition the intensity of the stimulation is controlled by the patient with a remote control device. The different programs give you flexibility to change the stimulation patterns based on your areas of pain. For example, some patients do not require their legs to be stimulated at night, so they shut that region off at night.
What are the limitations of having a stimulator implanted in my body?
There are limitations to having an implantable generator. These limitations include the inability to obtain MRI's, or therapeutic ultrasound. Your physical activities may be restricted from contact sports. Patients have downhill skied and returned to running after stimulator implantation. Again, you must remember if there a significant problem or the stimulator is not effective any longer, it can always be removed.