Use and Effectiveness of Spinal Cord Stimulation
There have been multiple studies that show the efficacy and cost-effectiveness of spinal cord stimulation in the treatment of chronic pain. In particular, a study by the American Society of Interventional Pain Practitioners (ASIPP) has shown this treatment to be effective and cost-effective. The study, printed in the journal Pain Physician, completed a comprehensive view of multiple studies of the efficacy and cost-effectiveness of spinal cord stimulation for the treatment of chronic pain. “This review study found spinal cord stimulation to be effective in the treatment of chronic pain and cost effective…Initial health care acquisition costs were offset by a reduction in post-implant health care resource demands.”1 In addition to spinal cord stimulation, additional neuromodulation treatments include peripheral nerve stimulation, which is an emerging use of neurostimulators. Implantation of spinal cord stimulation systems should be completed only by pain practitioners who are intimately aware of implantation techniques and spinal anatomy. Additionally, they should have specific training in the area of spinal cord stimulation and be familiar with all complications and risks of spinal cord stimulation implantation procedures.
It is important that all practitioners identify specific and appropriate patients as candidates for spinal cord stimulation therapy. Spinal cord stimulation systems are currently used to treat a variety of different pain conditions. The current primary use of spinal cord stimulation systems is for pain in the origin of the lumbar and cervical spine areas. The most common indications for spinal cord stimulation include failed back surgery syndrome (FBSS), peripheral neuropathy of any etiology, chronic regional pain syndrome (CRPW), phantom pain, facial neuropathy, radiculitis, and post-herpetic neuralgia. Most of the cases of spinal cord stimulation system implantation have been in the lumbar spine, primarily because there are more patients with lumbar conditions than cervical conditions. Cervical spine implantation poses some specific clinical hurdles, but once a practitioner becomes familiar with implantation in that area, it can be very effective and useful. Note that emerging uses of spinal cord stimulation include chronic pancreatitis and chronic pelvic pain. In addition, it appears from our clinic experience that spinal cord stimulation is most effective in treating extremity pain, though we have had significant success in treating pain in the paracervical and paralumbar areas. Achieving stimulation in those areas at a spinal cord target has proven difficult.
While this article is primarily directed to practitioners who implant percutaneous spinal cord stimulation systems, it may also appeal to referring pain practitioners and physicians who see pain patients but do not do this interventional procedure themselves. This article will discuss the use and effectiveness of spinal cord stimulation, general implantation concepts and identify a group of patients who provide particular challenges for spinal cord stimulation leads. Some of these patients—who are often also a clinical challenge—include obese patients, patients with spinal rotoscoliosis, patients with spinal arthrosis, and patients with pre-epidural adhesions. We will discuss each of these four patient categories separately, as they present some specific challenges and will provide some recommendations we have identified that have made it easier to implant percutaneous spinal cord stimulation leads in each category.
Spinal cord stimulation systems placement is completed in a two-phase process. Phase one is a trial phase that is typically completed percutaneously by using a special needle called a touhy needle to access the epidural space. Once the needles are in place, guidewires with multiple contacts or electrodes are advanced into position, depending on the patient’s primary pain location. The Holsheimer and Barolat study entitled “Spinal Geometry and Paresthesia Coverage in Spinal Cord Stimulation” is an excellent reference for identifying placement of spinal cord stimulation leads in chronic pain patients.2 This extensive study on the placement of spinal cord stimulation leads identifies patient response and pain reduction as a result of stimulation at various spinal levels. This study is therefore very helpful for practitioners in identifying particular locations of lead placement. The Holsheimer/Barolat study has basically mapped outsensory responses to stimulation at various spinal levels and can be used as an effective guideline for practitioners.
Phase One: Trial Phase
During phase one, and once the guidewire has been placed, an external generator is attached to the leads. Stimulation is then turned on. Direct communication with the patient is imperative at this time, and repositioning of the lead may be necessary to provide effective coverage of the patient’s pain. Again, at this point, reference to the Holsheimer/ Barolt study could be helpful in determining where the lead needs to be repositioned in terms of a cephalad-caudad approach. If the lead is too far lateral, the patient will have stimulation around the parathoracic or into the abdominal area. Positioning to the right or left is determined by where the patient perceives the sensation of the stimulator. For example, the lead may appear just left of midline, but the patient may receive stimulation on both sides. If that is not desirable in this particular patient, it may be helpful to move the stimulator slightly left.
As mentioned, it is important to communicate with the patient during this part of the procedure. However, we frequently use some minimal IV sedation with Versed, and have a nurse anesthetist monitoring and administering sedation to the patient. With careful monitoring of the patient and good communication and training by all involved in the procedure, we have not had any problems with patients being overly sedated to a point where it has interfered with placement. I also have found it helpful to use judicious local anesthesia (Lidocaine with epinephrine) in the subcutaneous area and 2% Lidocaine elsewhere. I use a Quincke needle and advance under fluoroscopic guidance toward the epidural entry site to provide additional anesthesia.
Phase Two: Implantation
Phase two is the permanent implantation and can be done percutaneously or through cutdown. In either case, many of the recommendations that we are making for complex patients can be effective in helping to place the leads and overcome some of the situations that prove difficult for the placement or manipulation of the leads.