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Spinal Cord Stimulation: Fundamentals

Interventional pain specialists offer an overview of spinal cord stimulation (dorsal column neuromodulation) fundamentals that referring physicians can use in clinical practice.
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An example of a patient in which the paddle lead is advantageous is one who has undergone previous instrumented fusion for spondylolisthesis. Although there is radiographic evidence of adequate fusion and no evidence of neural compression, the patient has persistent radicular lower extremity pain and disabling axial low back pain.

After a successful percutaneous lead trial, spinal cord stimulator placement using a single paddle lead centered at T9-T10 is performed. The lead consists of two or three rows of several electrodes whose output can be adjusted individually via a transcutaneous programming device. This allows the patient to try, noninvasively, a wide range of programming options postoperatively until optimal stimulation coverage of low back and lower extremities is achieved without uncomfortable paresthesias.

Preoperative and postoperative intravenous antibiotics are administered and following recovery, the patient is discharged with 7 to 10 days of oral antibiotics, or kept for a 23-hour hospital observation (physician/ surgical preference).

Postprocedure Care and Follow-up Protocol
Upon discharge, the patient is given verbal and written instructions to avoid excessive lifting, twisting, or bending, and to sponge bathe only for 2 weeks. The first postoperative visit is 1 week following the permanent insertion. The surgical site is checked and any skin staples or sutures are removed. At that time, there may be slight swelling noted in the pocket. This is probably a normal finding and represents a seroma (a pocket of clear fluid secreted from the serous glands that can develop post-surgery) although the clinician should have appropriate suspicion for infection. A seroma may last for 3 to 4 weeks and may interfere with transmission to the radiofrequency-controlled devices (eg, Eon, Genesis, and Renew devices from St. Jude Medical; Interstim, Prime Advanced, and Restore devices from Medtronic; and Precision device from Boston Scientific). Also during this visit, the spinal cord stimulator is reprogrammed as needed. The patient should be seen 2 weeks later and then again in 1 month. After that, the patient should be seen as indicated. If the patient has a goal of returning to work, then aggressive rehabilitation should be performed.

Potential Complications of SCS

There are rarely any serious complications from the temporary percutaneous trial or permanent procedure for spinal cord stimulator implantation.44 In one study, one nonfatal pulmonary embolism and one case of paraplegia lasting 3 months were reported.45 The latter resulted from a laminectomy that was used to place the stimulating lead. Other rare reported complications include sphincter disturbance and gait abnormality.46

Most complications from the temporary or permanent devices include formation of scar tissue, poor localization of paresthesias, lead migration, lead fracture, pain at the pocket site or connection site, infection, nerve injury, and epidural hematoma. 24,25,29,44,47-52 In a comprehensive summary of different publications, lead migration or displacement varied from 3.7% to 69%, although most studies reported migration between 16% and 25%.44 Rates of lead fractures were reported in various series from <1% to >20% and superficial infections occurred in 2% to 12% of cases. Serious surgical infections were rare, as were clinically apparent epidural hematomas. In one study, cerebrospinal fluid leakage was found in 2% of patients. Avoiding complications in spinal cord stimulation should follow an analytical step-wise approach.

In our clinical experience that has involved >600 lead implants, the clinical practice has experienced only 3 in situ infections with permanent devices.10 One infection resulted from an occult bone stimulator infection due to a previous fusion and presented >6 months following implantation; the second infection occurred 2 ½ months after implantation from an unknown source; and the third infection occurred 18 months following implantation. The latter infection was apparently due to hematogenous seeding when the patient broke an abscessed tooth after he bit down on an apple the week before. In the first two cases of infection, the spinal cord stimulators were removed and the patients were placed on intravenous antibiotics without further sequelae. In the third case, the spinal cord stimulator was not removed and the patient was adequately treated with oral antibiotics and dental care. We have had no complications with any of the trial lead placements.

Clinical Results

The largest study of SCS includes 320 consecutive patients who underwent either temporary or permanent implantation at the Johns Hopkins Hospital between 1971 and 1990.13 This series includes follow up on 205 patients, the majority of whom had the diagnosis of failed back surgery syndrome (FBSS). Permanent spinal cord stimulator implants were placed in 171 of these patients. At follow up (mean interval 7.1 years, SD 4.5), 52% of patients had >50% continued pain relief, and 58% had reduced or eliminated the use of medication. About 54% of patients younger than 65 were working at the time of follow up; 41% had been working preoperatively.

The percentage of patients having long-term pain relief is similar in the majority of large published studies of spinal cord stimulator implants for FBSS. The success rate in most of these studies, which is generally reported as ≥50% pain relief, is approximately 50% to 60%.37,53-57 Some studies report success rates as high as 88% and others as low as 37%.58,59 Although these latter studies differ in implantation technique and screening protocols, the success rate for pain reduction generally remains the same.

More recent published reviews specifically have looked at the reduction in pain, reduction in opioid medication consumption, improvements in activities of daily living function, and return to work status.24,60-63 According to these studies, long-term pain reduction (at least 2 years after implantation) can be expected to range from 50% to 70% in approximately 60% of SCS patients. In 50% to 90% of individuals, there will be an elimination or reduction in the use of opioids. The return to full employment rate after SCS reported by two studies is 25% to 59%, which is very significant when comparing it to the usual return-to-work rate in this population of 1% to 5%.24,6

Reasons for the disparity between pain reduction and return-to-work rates appear to reflect the high percentage of unskilled laborers among this population, the prolonged periods of disability, and the attendant sociobehavioral changes that take place. Despite this disparity, there is a general increase in function and activities of daily living.

Last updated on: June 1, 2015