Spinal Cord Stimulation versus Reoperation for Failed Back Surgery Syndrome (2008)

In Reply: We thank Dr. Wilkinson for his attention to our study (6). Indeed, in this economic analysis, we did not reiterate the reasons for excluding patients but instead merely referenced the clinical trial report (5), which notes that treatment of 1) gross spinal instability and 2) predominantly axial low back pain involves issues beyond the scope of the study. Axial low back pain often has a significant nociceptive component that spinal cord stimulation (SCS) is not expected to treat, and coverage of the low back with SCS paresthesia is difficult to achieve in many patients. Among the subset of patients included in the economic report, the success rate of SCS for patients randomized to SCS was 37% (7 of 19 patients), but for those who passed the screening trial, the rate was 50% (7 of 14 patients), if we count the “lost” patient as a failure, although, in fact, he was an SCS success but died during the study period. In contrast, for those randomized to reoperation, the randomized treatment success rate was 9.5% (2 of 21 patients). In this group, the SCS crossover treatment success rate was 38% (5 of 13 patients), and 100% (5 of 5 patients) for those who passed the screening trial. Our definition of “success” (at least 50% pain relief and patient satisfaction with treatment) was rigorous. In clinical practice, it is not unusual for patients to be satisfied with less. Dr. Wilkinson states that we did not report what became of the patients who did not achieve success with either SCS or reoperation, although we report results beyond the crossover endpoint, notably that all 5 who failed SCS and went on to reoperation failed, whereas 5 of 13 patients who failed reoperation went on to achieve success with SCS. We agree that it would be wonderful if all studies of this sort could follow patients indefinitely. We should note, however, that our SCS failures have an opportunity for a later successful therapeutic intervention, as they have simply undergone a reversible neuromodulation procedure. In our clinical study of ganglionectomy (4), we not only observed no long-term “successes” by the same outcome measure used in our current study, we also observed that the yield of SCS in patients with FBSS who failed ganglionectomy was much lower than would normally be expected (only one screening trial among 6 patients was successful, which is far below our usual rate of success). This suggests that ganglionectomy destroys the substrate for SCS. Thus, in our study, the ablative procedure produced disappointing results and apparently compromised further treatment. We presume that Dr. Wilkinson's patients who failed ganglionectomy likewise had only limited further options for successful treatment. Contrary to Dr. Wilkinson's assertion, we are not averse to ablative surgery per se; for example, radiofrequency facet denervation has a useful role (3) and is supported by randomized controlled trial evidence (2). In the article Dr. Wilkinson references (8), on the other hand, he notes that “other patients selected ganglionectomy in preference to trials of DCS [dorsal column stimulation] implantation because of their awareness of the limited success overall of good long-term pain relief from these devices and because they hoped to experience pain relief while avoiding permanent DCS implantation.” From whom would his patients have acquired this awareness and hope? He also reports, “In 10 of the 19 patients, TENS [transcutaneous electrical nerve stimulation] or DCS [dorsal column stimulation] implantation failed to achieve pain relief …” In fact, only 2 of his patients had an SCS screening trial; the other 8 merely had a trial of TENS. Among Dr. Wilkinson's 7 FBSS patients with radicular pain who made more than one follow-up visit after an initial ganglionectomy, pain increased from one visit to the next in 4 patients, decreased in 2 patients, and stayed the same in 1 patient (8). This loss of pain relief is similar to our experience at Johns Hopkins with dorsal root ganglionectomy (4), in which the percentage of patients who reported 50% pain relief decreased from 38% at the 24-month follow-up to 23% at the 5.5-year follow-up. This contributed to the 0% “success” (50% pain relief and patient satisfaction) at the 5-year follow-up (see Table C1 for further comparison).TABLE 1: Comparison of outcomes in North and Wilkinson ganglionectomy studiesaFinally, temporary relief by a local anesthetic block does not reliably contribute to a diagnosis or predict the result of ablation (1,7). In fact, if selective nerve root block were predictive, ganglionectomy would have been successful in all of Dr. Wilkinson's patients (8), instead of only 10 of 19 patients (two of whom needed repeat procedures to regain lost success), because all “underwent a successful diagnostic selective nerve root block.” Quite simply, we cannot “try out” ablative or anatomic reconstructive spine surgery. In contrast, as an augmentative (neuromodulation) procedure, SCS can be tested with a minimally invasive screening trial that emulates the definitive procedure, and even this remains reversible. We can all agree, however, that there is no ideal treatment for chronic pain, and we feel confident that an SCS screening trial should be offered to appropriate FBSS patients before they undergo ganglionectomy, which is an irreversible ablative procedure. Richard B. North Jane Shipley Baltimore, Maryland