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10 Articles in Volume 10, Issue #1
An Overview of CRPS
Balancing Evidence, Efficacy and Stakeholder Values in Practical Pain Care
Biopsychosocial Approach to Management of Total Joint Arthroplasty Patients
Dextrose Prolotherapy Injections for Chronic Ankle Pain
Genetic Influences on Pain Perception and Treatment
Headache in Children and Adolescents
Hormone Replacements and Treatments in Chronic Pain: Update 2010
Opioid Treatment 10-year Longevity Survey Final Report
Therapeutic Laser in the Treatment of Herpes Zoster
Use and Effectiveness of Spinal Cord Stimulation

Use and Effectiveness of Spinal Cord Stimulation

Spinal cord stimulation has been one of the major advances in the efficacious and cost-effective treatment of chronic pain patients with multiple different pain processes—particularly of cervical and lumbar spinal origin.

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.

Two-phase Process

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.

General Overview

It is important to identify all anatomical markers prior to attempting percutaneous implantation. Initially, the fluoroscope should be positioned to the planned point of implantation and the epidural space (EES). Also, we need to specifically identify the skin entry site (SES). This is the location on the patient’s skin where we intend to apply local anesthesia and advance the needle toward the EES. It is important to position the fluoroscope so that the EES is exactly squared on anterior-posterior (AP) and oblique views. Oblique positioning is important so that the entry site is anatomically correct when visualized on the fluoroscopy. The facets are the next most important anatomical marker for the skin entry site. You need to go down two facet levels below the EES and mark the midline inferior margin of the facet joint. A mark on the patient’s skin should be made there as well, and a line is then drawn between those two points. Of course, if bilateral implantation is anticipated, then the opposite side should be completed. A determination to enter right or left in a patient without any significant anatomical deformities is not relatively important. Another line is then drawn on the patient by marking down the spinous process and forming a cephalad-caudad line down the tips of the spinous process. You should then measure, or estimate, the angulation that you have formed between the line from the skin entry site to the point of entry and this angle should be less than 15 to 25 degrees. The angle of approach from the lateral view—in other words, the angle of the needle from the skin—should remain in the 15 to 25 degree range as well. Too sharp of an angulation on either of these entries can make it very difficult to advance the leads appropriately.

I have found it beneficial to use the stiffer stylets with curved tips which results in a curving of the lead as well. This is very effective in positioning and manipulating the lead wires. Figure 1 illustrates the line (identified as Line A in the figure) that would be drawn on the patient’s skin along the spinous process to demonstrate a cephalocaudad linear point of reference. Line B is drawn through Point 1, which is the EES and Point 2, which is the SES and at an angle to Line A. Please note that the angle formed using these reference points is less than 30 degrees.

Our normal point of entry for low back and lower extremity pain is the T12 spinous process. For cervical entry, it is normally at the T2 level. Patient positioning is very important and wedges and pillows should be positioned under the patient’s upper abdomen and lower chest to reduce the kyphosis as much as possible.

Obese Patients

The challenge of implanting spinal cord stimulation systems in obese patients is that the extra subcutaneous tissue often changes the angulation of the lateral AP approach. Therefore, this alters the skin entry site, making the AP angulation substantially steeper.

Figure 2a presents a lateral view that demonstrates the effect of excessive subcutaneous tissue. Point 1 identifies the skin entry site on this patient with a reasonable normal body habitus and a linear lateral line through Point 1 (SES) to Point 3 (EES). Line B demonstrates a similar line through where the SES point would be with additional subcutaneous tissue and a line is then drawn through Point 3 (EES). Note that the angulation of the angle of entry on Line B is increased to an acute level making it difficult to advance stimulator leads. In Figure 2b, we have extended the EES site caudally, forming a new Line A that is longer and maintains a more flat plane of entry to allow an easier implantation and advancement of spinal cord stimulator leads.

The remedy for dealing with the obese patient is relatively simple. The line that you have drawn between the anticipated EES and the SES should be extended beyond the normal SES. The practitioner at this point simply advances in a caudad manner along that line. The amount that you need to go caudally depends obviously on the amount of subcutaneous fat tissue and varies anywhere from 1 cm to 4 cm. This will change the angulation so that you maintain a shallow and appropriate AP angle of 15 to 30 degrees, and also makes the advancement of the spinal leads much easier. At the same time, you will be maintaining both your lateral angulations and oblique angulations discussed above. Companies that manufacture spinal cord stimulation systems make extended length needles and extended length lead wires with contacts, which are frequently necessary when you have to go back along that line a substantial amount in order to maintain the angulation. Outside of this relatively minor adjustment, the obese patient may obviously require some additional local anesthetic because of the depth of penetration of the stimulator needle. We frequently will use a longer Quincke needle to provide deeper subcutaneous local anesthetic in these patients. After trying this method on a few patients, you will find that it is an effective and easy way to overcome the additional challenge of implantation in the patient with additional subcutaneous fatty tissue.

Figure 1. Illustration of Line A that would be drawn on the patient’s skin along the spinous process to demonstrate a cephalocaudad linear point of reference and Line B drawn through Point 1 (EES) and Point 2 (SES). Please note that the angle formed using these reference points is less than 30 degrees. Figure 2A. Presents a lateral view that demonstrates the effect of excessive subcutaneous tissue. Point 1 identifies the skin entry site on this patient with a reasonable normal body habitus and a linear lateral line from Point 1 (SES) to Point 3 (EES). Line B demonstrates a similar line through where the SES point would be with additional subcutaneous tissue and a line is then drawn through Point 3 (EES).

Rotoscoliosis of the Spine

If you encounter a patient who has substantial rotoscoliosis, it is important to identify the side of convexity and concavity and the amount of spinal rotation. We emphasize the importance of identifying the EES and squaring the images at that location. Prior to implantation on all patients, it is also important to move the fluoroscope cephalad and preoperatively mark the anticipated final placement position (FPP) of the lead contacts. You will need to make some adjustments in the initial implantation angulation by recognizing the angle of curvature. The basic concept is to change the angulation of an oblique nature so as to reduce the acuity of advancement into the concave side of the scoliosis and to compensate for the convex side as well. This process is completed first by identifying the scoliosis and then identifying the severity and rotation. At this point, anticipate the variances in the EES and the FPP. Try to picture where the spinous process is when viewed on a direct AP view, which necessitates manipulating obliquely right and left to get an idea of the amount of rotation. By determining the amount of angulation right or left, you simply need to flatten out your approach angle and approach further to the left or right of the anticipated spinous process at the EES on the side of the concavity. What this will do is shorten the angulation and make it easier to manipulate the lead wire. On the side of the convexity, it is helpful to increase the angle just slightly in both cases, probably just 10 to 15 degrees.

I find it substantially helpful to use the stiffer stylets with curved tips. This will help to manipulate on the curvature. Another observation in these patients is that trying to align along the right or left of the midline in the spinous process is distorted despite the adjustments that we have made to the fluoroscope in order to position this to an AP view. I find frequently that a lead placed slightly to the right on the convex side is going to stimulate more to that side than anticipated. In other words, the leads need to be positioned more toward the concave side than what we are seeing anatomically on the AP positioning. This varies with all patients and is affected by the amount of spinal rotation. These simple suggestions can help to provide appropriate placement in the patient with rotoscoliosis.

Results for Those Told No Other Treatment Options Were Available or Surgery Was Their Only Treatment Option

As previously noted, prior to prolotherapy 14 (45%) patients were told no other treatment options were available for their wrist pain. As a group they suffered with pain an average of 66 months. Analysis of these patients revealed a starting average pain level of 6.2 and a post-prolotherapy pain level of 1.5. Wrist stiffness averaged 4.0 prior to prolotherapy treatments and improved to 1.5 after completing the treatments. Eleven out of fourteen (78%) achieved 50% or greater pain relief. Prior to prolotherapy only 36% of the patients could exercise longer than 30 minutes, but this increased to 78% after prolotherapy.

Five patients (16%) were told that surgery was the only option available to eliminate their wrist pain. Their average pain duration prior to prolotherapy was 39 months. Their starting average pain level was 4.8 before prolotherapy, which declined to 1.2 after prolotherapy. Reported wrist stiffness was 1.8 prior to prolotherapy and 1.0 after completing their prolotherapy treatments. All five patients (100%) exhibited 50% or greater pain relief. One out of five of the patients could exercise longer than 30 minutes prior to prolotherapy, but this number increased to four out of five after prolotherapy (see Table 2).

Spinal Arthrosis

Patients who have significant spinal arthrosis can present particular challenges as well. First, when identifying the EES, observation for substantial arthrosis can be helpful. One of the best things we can do to help our patients here is to note that if there is substantial arthrosis, then we may need to change our anticipated EES above or below by an appropriate number of levels. I suggest that if you have all of your angulations and specific alignment completed, and you are not able to find entry into the epidural space after a reasonable period of trial, then you should go to another level. It frequently does take a significant amount of manipulation and angulation of the needle in various directions in order to work through and weave your way through a patient with a significant amount of arthritis. It is not necessary to give up immediately, but be gentle and make sure that you slightly advance and then slightly withdraw and then advance the needle again. Also make sure that, if necessary, you provide additional subcutaneous local anesthesia so that the patient does not become overly apprehensive and uncomfortable and may want to abort the procedure. There is no specific recommendation that I can give in terms of how to manipulate a needle around an arthritic patient, other than to try angulating a little steeper on the AP and a little left or right on the oblique. In talking to other practitioners, I think the feeling is that you are kind of working your way through an area of arthritis. It is important that you do not force the needle when you contact bony material, but rather gently change angulation. I have found it also effective in many patients with arthritis that the SES is dropped down three levels below the EES, decreasing significantly the oblique angulation of approach. Again, you may need to use a longer needle and a longer lead. Basically, observe the spine on fluoroscopy prior to placement. Pick the best possible EES and gently manipulate the needle to achieve loss of resistance. If you have major resistance and difficulty, do not spend an excessive amount of time but, instead, try another level. You may have to go up or down quite a few levels to find an area where you can obtain access to the epidural space. Also, on occasion in an arthritic patient, I have found good loss of resistance in the epidural space, but have been unable or had difficulty advancing the leads. In many cases, the guidewire will pass, but the leads do not advance. What is occurring in these cases is that there is some arthritic bony obstruction to the epidural space—either posteriorly or anteriorly on the spine—that is inhibiting advancement of the lead. I find that intrusion can be overcome by simply manually manipulating the angulation of the needle. A gentle posterior movement half a centimeter or two while, at the same time, gently advancing the leads typically overcomes this arthritic obstruction. I frequently find that in order to advance or more easily manipulate the wire on arthritic patients, a similar gentle manual traction is necessary. The patient should not experience any increased pain or discomfort with this manipulation based on my experience.

Pre-epidural Adhesions

I have identified a group of patients who have what I feel to be pre-epidural adhesion formation. There has been some speculation that the formation of these adhesions occurs in patients who have had previous surgeries or simply chronic pain conditions. There are some additional theories and thoughts on how chronic pain relates to the formation of these adhesions. I have identified these patients in the following manner. I get a clear loss of resistance that identifies the epidural space. When I try to advance the leads, even though they do advance beyond the tip of the needle, it is not a smooth advance and/or the needle makes immediate turns to the right or left together with some additional resistance. I have found that by taking a shallow angle and advancing minimally, just a millimeter or so at a time, I can advance beyond this section of the pre-epidural adhesions. I have done this on numerous occasions and have found that this simple advancement allows for easy flow of the leads and much easier positioning of the needle distally. This phenomenon may be similar to cases where we enter the epidural space easily, advance without problem, and then suddenly run into “a brick wall.” These are probably some form of the same pre-epidural adhesions. The tap method is used, and I have found it to be effective in advancing beyond these impairments for successful lead placement. This is frequently done with a stiff stylet and I find I can frequently accomplish this with my favorite stiff stylet. Simply advance the needle until it is at the point of impediment and then slightly withdraw about one-half to one centimeter and gently but quickly advance the guidewire, tapping through the adhesions. Typically it is quite easy and only causes the patient any significant discomfort in a select few cases. Fre-quently, when advancing leads through the epidural space, a patient will describe some immediate, but very temporary radiating discomfort, which I believe is due to some form of epidural adhesion causing a pulling or tugging on the nerve roots. The key takeaway here is that whatever discomfort the patient has, it is very temporary. If the patient has persistent pain with either the tap method or advancing through the epidural space, in my opinion, the procedure should be discontinued.

Additional Pearls

Frequently, upon implantation and for a variety of different reasons, the lead will want to angulate right or left. If a patient can tolerate it and you cannot get the needle back to midline, I sometimes use what I refer to as a “bounce” method, which is basically bouncing off a lateral position in the epidural space and letting the lead curve back towards the midline. Following this manipulation, lateral x-rays should be done to assure a posterior position of the lead. Though it has not been previously stated, lateral x-rays are used at various points and routine positioning to assure appropriate posterior positioning. As long as the patient does not experience any significant pain or discomfort toward the abdomen or chest wall—and lateral imaging does not reveal that the lead has moved into the anterior space—I think this is a reasonable approach.

Additionally, to achieve minor adjustments in placement, I have found that the easiest and most effective method, in addition to using a stiff, curved stylet, is manipulating the end of the needle from the stylet tip by turning and twisting so that the stylet points into the desired direction. Twist until the fluoroscopy shows the tip of the lead pointing in the desired direction, then slowly advance and re-fluoroscope. If this is ineffective, an additional method can be used and that is gentle manual manipulation of the needle with the lead completely with-drawn proximal to the tip in the desired direction. While applying gentle manual rotation of the tip, gently advance the needle. Re-fluoroscope and see if you have now achieved the desired effect.

Summary

Spinal stimulation is one of the most important advancements in the treatment of chronic pain patients and has quickly become a key therapy chronic pain treatment for all pain practitioners. Any physician who has a patient with chronic leg or arm pain from multiple etiologies or chronic back or neck pain, should refer their patients to a trained, knowledgeable, and experienced interventional pain practitioner who has substantial experience with spinal cord stimulation.

Appropriate identification of anatomical markers and familiarization with the appropriate approach angulations will help ensure a successful implant procedure. The key points identified for some challenging patient categories might provide you with some helpful techniques and aid in overcoming a few of these challenges. If you have not reviewed the Holsheimer/Barolat study, I highly recommend it as an excellent reference for lead placement.

Disclosure

Dr. Donnini does not have affiliations, sponsorships, or grants from any equipment companies or drug companies.

Last updated on: January 5, 2012
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