Technical Aspects of Spinal Cord Stimulation for Managing Chronic Visceral Abdominal Pain: The Results From the National Survey
Leonardo Kapural MD, PhD 1, Timothy Deer MD 2, Alexandar Yakovlev MD 3, Toula Bensitel MD 4 , Salim Hayek MD, PhD 5, Stephen Pyles MD 6, Yasin Khan MD 7, Alberta Kapural MD 4, Dondre Cooper 8, Lisa Stearns MD 9, and Paulina Zovkic 8
1 Director, Clinical Research, 4 Research Associate and 8 student, Department of Pain Management, Cleveland Clinic, Cleveland, Ohio, 2 CEO, Center for Pain Relief, Charleston, West Virginia, 3 Director, Comprehensive Pain Management of Fox Valley, Appleton, WI; 5 Director, Pain Medicine Division, Department of Anesthesiology, University Hospitals, Cleveland, Ohio 6 Munroe Regional medical Center, Ocala, FL; 7 Comprehensive Pain Center, Betlehem, PA, 9 Private Practice, Scottsdale, AZ
Abstract
Background, Objectives and Methods: A few recent reports suggested that spinal cord stimulation (SCS) effectively suppresses chronic abdominal pain. However, there is no consensus on patient selection or technical aspects of SCS for such pain. That is why we conducted national survey and collected 76 case reports. There were 6 incompletely filled reports, so we analyzed 70 cases.
Results: There were 43 female and 27 male patients. SCS was trialed in an average of 4.7 days (median of 4 days). In most patients, the leads were positioned for the SCS trial with their tips at the level of the T5 vertebral body (26 patients) or T6 vertebral body (15 patients). Four patients failed SCS trial: their average baseline VAS pain score was 7±2.4 cm and did not improve at the conclusion of the trial (6.5±1.9 cm; p=0.759). Pain relief exceeded 50% in 66 of 70 patients reported. Among those, VAS pain score before the trial averaged 7.9±1.8 cm. During the trial VAS pain scores decreased to 2.45±1.45 cm (p<0.001). The opioid use decreased from 128±159 mg of morphine sulfate equivalents a day to 79±112 mg (p<0.017). During permanent implantation most of the physicians used two octrode leads and were positioned midline at T5-6 levels. The average patient follow-up was 84 weeks. VAS pain scores before an implant were 8±1.9 cm, while after the implant 2.49 ±1.9 cm. The opioid use before an implant was 158±160 mg and at the last office visit after the implant 36±49 mg.
Conclusions: In conclusion, it seems that the SCS for the treatment of the abdominal visceral pain may provide a positive patient long-term experience, significant improvements in pain scores and a decrease in opioid use.
Introduction
Each year, 16 million patients in the United States, visit their physician with a chief complaint of abdominal pain. Of these patients about 2 million continue to have persistent severe abdominal pain
despite pharmacological interventions, minimally invasive techniques and surgical interventions 1,2. Pain is the most prevalent symptom in gastroenterology clinics 3. The need for continuous treatment of chronic abdominal pain also causes a significant burden on the healthcare system as well as on the patient due to disability 3.
Spinal cord electrical stimulation (SCS) has been successfully used for the treatment of neuropathic pain of various etiologies 4,5 . In animals, electrical SCS can suppress visceral response to colon distension 6 . A few recent case reports involving human subjects suggested that SCS effectively suppresses severe, long-standing abdominal/pelvic visceral pain 7-12 .
Although a significant number of patients with severe chronic visceral pain will transiently respond to sympathetic blocks and radiofrequency ablation, substantial long-term pain relief is usually lacking 13,14 . SCS, therefore, may be a welcome addition to the treatment of moderate to severe chronic visceral abdominal pain. Recently, we reported pain relief, improvement in functional capacity, and decreased consumption of opioids in 30 patients who underwent SCS implantation for control of chronic epigastric visceral 15 and 6 patients with pelvic visceral pain 10 . Although, there are compelling preliminary data that the SCS may decrease pain and improve functional capacity in patients with various visceral chronic pain syndromes, it may require years to accumulate sufficient supportive clinical evidence.
Previously reported indications for the SCS to treat abdominal pain included mesenteric ischemia, irritable bowel syndrome (IBS) 8 , chronic pancreatitis 9,10,11 , diffuse abdominal adhesions, painful attacks of Familial Mediterranean Fever (FMF) 12 , and chronic visceral pelvic pain after long-standing endometriosis 7 . Currently, pain physicians are using SCS in clinical practice for the treatment of abdominal visceral pain based on their own personal experience in placing epidural electrodes and unpublished experiences of other implanting physicians. There is no consensus on patient selection, appropriate lead placement technique and segmental positioning, number of leads needed or even on lateralization of the leads (eg. dorsal column or dorsal root ganglion stimulation). Additionally, individual pain physicians may trial only a handful of patients with chronic abdominal pain, mainly because of the current issues with payers. Thus, a substantial number of completed SCS cases (either successful or not), may be dispersed across the country and amenable to review only through survey.
Previously reported indications for the SCS to treat abdominal pain included mesenteric ischemia, irritable bowel syndrome (IBS) 8 , chronic pancreatitis 9,10,11 , diffuse abdominal adhesions, painful attacks of Familial Mediterranean Fever (FMF) 12 , and chronic visceral pelvic pain after long-standing endometriosis 7 . Currently, pain physicians are using SCS in clinical practice for the treatment of abdominal visceral pain based on their own personal experience in placing epidural electrodes and unpublished experiences of other implanting physicians. There is no consensus on patient selection,
appropriate lead placement technique and segmental positioning, number of leads needed or even on lateralization of the leads (eg. dorsal column or dorsal root ganglion stimulation). Additionally, individual pain physicians may trial only a handful of patients with chronic abdominal pain, mainly because of the current issues with payers. Thus, a substantial number of completed SCS cases (either successful or not), may be dispersed across the country and amenable to review only through survey.
Methods
The names and E-mail addresses of pain management physicians who use spinal cord stimulation were collected from the various societies’ directories. The practicing physicians were than contacted using current email or telephone numbers and asked to participate in the study. Case Report Forms were available on a protected Internet site to participating physicians for completion.
There have been reported differences in responses between email surveys and written surveys (16). This may make it difficult to assess whether the observed differences are due to factors such as participant deception or actual differences due to characteristics associated with computer and non-computer users. Therefore, we also called or mailed an invitation to those who did not respond to email queries.
The questionnaire used was named: Case Report-Spinal Cord Stimulation for Visceral Abdominal Pain and contained the following data: Physicians name, email address, study code number, age, and sex of the patient. Data points queried included: causes of abdominal pain (diagnosis) which was treated using the SCS. Pain characteristics of the abdominal pain syndromes were described, as well as the location of particular pain area (epigastric, periumbilical or other). Also, previous pain treatments are investigated. Prior treatments and diagnostic blocks administered to patients were queried
to determine patient and pain characteristics that promoted attempt of SCS.
To evaluate the technical details of SCS trialing we inquired whether psychological evaluation for the implantable devices was completed and whether a consensus multidisciplinary committee approved trial of SCS. Thereafter, important details on the lead placement were examined: how many leads were placed, at which vertebral level was the final position of the tip of stimulating lead, which type of leads were used (octapolar vs quadripolar, electrode spacing) and horizontal orientation of the leads (midline, paramedian, lateral). Also, the number of trialing days, before deciding if a permanent implant was indicated, was determined. Pain scores and opioid use before and after the trialing are inquired to obtain a general understanding from each of the physician contributors on which configuration of the leads and general positioning was thought to be advantageous both for trialing and implantation purposes. We collected similar data for the full implantation.
To evaluate differences between the various values, Mann-Whitney Rank Sum Test was used. Statistical tests and graphs were produced using Sigma Plot software (Systat Software Inc., San Jose, CA). Results are presented as means ± SDs unless otherwise specified.
Figure 1. Antero-posterior fluoroscopic view of the two leads positioned in the epidural space. Shown is the most frequent position of the tip of the leads: at the T5 vertebral body and midline.
Results
Collected were 76 case reports from 23 responding interventional pain medicine physicians. There were 6 incompletely filled reports, which were excluded from the analysis, resulting in 70 cases being reported.
The average age of the patients who received SCS for chronic abdominal pain was 47.3 years (median 47) . The age range was from 16 to 85 years of age. There were 43 female and 27 male patients. The most common, identifiable causes of the abdominal pain for which SCS was used were chronic pancreatitis (23 patients) and post-surgical intraabdominal adhesions (20 patients), followed by the gastroparesis (9 patients). Frequently, post-surgical visceral pain included persistent abdominal pain following common abdominal surgeries like cholecystectomy, bowel resection etc, but also after the gastric bypass, endometriosis-related surgical procedures and following the Nissen’s fundoplication. There were 9 patients where the identifiable cause of their pain could not be determined. Described characteristics of the chronic pain were usually burning and aching while throbbing, stabbing, cramping, dull and sharp were described less frequently. The most frequent painful areas were epigastric and secondly, periumbilical.
Most of the patients received opoids; a smaller number were provided membrane stabilizers and/or antidepressants. the previous conservative treatments most of the patients received opoids, but also membrane stabilizers and antidepressants. Among the previous interventional procedures sympathetic blocks prevailed. In addition, a few patients also had pancreatic resection, ileostomy closures, ERCP, gastric pacemakers (5 patients) and multiple laparoscopic adhesiolysis. Only 53 % actually received a diagnostic blocks (either celiac or splanchnic) to characterize their visceral pain.
SCS Trials were conducted as follows;, 62 out of 70 reported patients received psychological evaluation for the implantable devices just before the trial. Only 24 out of 70 cases (34%) were evaluated by a local multidisciplinary committee for appropriateness of implantable devices before the decision was made to proceed with the trial. The majority of the leads were placed in the midline position (Figure 1), however in 21 cases leads were placed paramedially (p=0.99). 50% of the patients received two leads (mainly octrodes) for their trial. There was no difference (by the end of the trial) in percentage of the pain score improvements if one or two leads were used (p=0.11). SCS was trialed on average for 4.7 days (median of 4 days) with the shortest trial duration of only one day and longest of 14 days.
In most patients, the leads were positioned for the SCS trial with their tips at the level of the T5 vertebral body (26 patients, Figure 2) or T6 vertebral body (15 patients). All physicians reported appropriate coverage of the painful area with paresthesias during what was considered above the perception threshold stimulation.
Figure 2. The graph below illustrates the distribution of the leads tip position in 70 cases properly reported in this survey. The most frequent positions of the tip of the leads inserted during the SCS trial where the optimal paresthesias to cover area of the patients pain was achieved were at T5 (26 patients) and T6 (15 patients) vertebral level.
Four patients were reported to have failed SCS trial: their average baseline VAS pain score was 7±2.4 cm and did not improve at the conclusion of the trial (6.5±1.9 cm; p=0.759; Figure 3). They were patients of four different reporting physicians and three of them actually responded to the diagnostic visceral block before the trial.
Pain relief exceeded 50% in 66 of 70 patients reported (94%). Among the 66 patients in whom the trial was deemed successful, VAS pain score before the trial averaged 7.9±1.8 cm. During the trial VAS pain scores decreased to 2.45±1.45 cm (p<0.001; Figure 3).
Figure 3.
IA significant decrease of opioid use from baseline (visit before the trial) was noted during the trial period, but its magnitude was not as profound as that noted when baseline opioid use was compared to the last patient visit after the implantation. In the latter case opioid use decreased from 128±159 mg to 79±112 mg of morphine sulfate (MSO4) equivalents a day (p<0.017; Figure 4).
Figure 4.
During permanent implantation, similar to the trial phase, most of the physicians who responded to the survey would use two octapolar leads and most of which were positioned midline at T5-6 levels (see Figure 2). The average patient follow-up was 84 weeks (median 62 weeks; range from 9 to 436 weeks of stimulation). Majority (56 out of 70 patients) were followed for more than a year. VAS pain scores before an implant were in average 8±1.9 cm, while after the implant dropped to 2.49 ±1.9 cm . This improvement in pain scores was significant (p<0.001; Figure 3). The opioid use before an implant when expressed in MSO4 equivalents was 158±160 mg (median 80 mg) and at the last office visit after the implant 36±49 mg (median 20 mg). Not unexpectedly, the long-term decrease in opioid use noted at the last patient visit was greater than the opioid decrease noted during the trial period (Figure 4).There were 8 spinal cord stimulator revisions, two systems were removed because of patient dissatisfaction (one had diarrhea with SCS and the other headache).
Overall patient satisfaction as reported by the treating physicians was considered very high (Figure 5). 62 out of 70 patients (89%) were perceived by their providing physicians to have a positive opinion regarding such treatment and 35 patients (50%) were extremely satisfied (Figure 5).
Figure 5.
Discussion
This survey was conducted to assess technical and clinical variability among interventional pain medicine physicians using SCS for managing abdominal pain across the United States. Assessed were the most frequently used techniques for the patient selection, trialing and implantation when SCS was attempted for the treatment of visceral abdominal pain. This paper can be considered as the preliminary technical report on specifics of this application of neuromodulation.
Considering the number of SCS cases reported by the physicians responding to this survey, SCS for abdominal visceral pain is still rarely used despite its high therapeutic success rate. Reasons may be very few studies describing basic mechanisms of neuromodulation for long-standing visceral pain, comfort levels by the physicians, and issues with coverage of such treatment by the payors. The currently available systems are not labeled by the Food and Drug Administration for the specific complaint of abdominal pain, but SCS is approved for stimulation of the trunk. The cases reported in this survey suggests great potential for this modality of care.
The technical aspects used to achieve the optimal spinal cord stimulation in this surveys patient group (70 patients) are consistent with the data that we collected in our retrospective study on 35 consecutive patients 15 . The most frequent placement of the lead was posterior epidural midline position and the most frequent vertebral level reached with the lead tip was T5 and T6. Sixty-three percent of the patients in our retrospective study 15 and 56% of the patients in this survey had lead positioned at that vertebral height to achieve optimal paresthesias within the abdominal area and just below the chest.
The proportion of the patients in this survey who received successful trial and went on to have an implant was 94%. Such success rate is very high when compared to success rates of our retrospective study of 35 consecutive patients trialed with SCS for the abdominal, visceral pain (86%). This may imply that non-visceral abdominal pain may respond better to SCS or more likely that trial failures were underreported in this survey, suggesting a bias for pain physicians to participate in the survey if they had positive responses.
Rejection to participate may present a problem with the data. The individual physician who would not participate in this study may have a different experience with the SCS technology when used for the treatment of chronic abdominal pain than those who participated in this survey.
Weakness of this survey is that it is not clear if the sample size of the physicians being surveyed is sufficient enough. Therefore, such sample size of the responding physicians may not adequately represent the population of all of the physicians who trialed SCS for the chronic visceral abdominal pain. We attempted to have an effective survey and collect statistical data useful for the interpretation by acquiring responses from all of the interventional pain physicians and not only those known to use SCS for the treatment of visceral abdominal pain. In this manner, selection bias was limited.
Other common mistake related to the surveys is the failure to analyze some of the answered qualitative assessments because of an individual refusal to answer the question. We try to avoid such a problem by choosing only fully answered survey forms. Accuracy of the answers lies with the interviewed physicians, however biased answers are unlikely as data were copied from the patient charts and questions which could not be answered by reviewing the chart data or subjective answers were avoided.
Finally, the standard for the success of any survey is how the data measures the population being studied. In this case, we are surveying pain physicians as surrogates for their patients and asking for outcome information. We purposefully designed the survey to provide information that would be discernable from the patient’s medical record. The problem inherent in this analysis, however, is relying upon chart reviews by multiple individuals.
Conclusions
In conclusion, it seems that the technical aspects of SCS for the treatment of the abdominal visceral pain are uniform between the physicians who use such technology across the country and is also consistent with the previous larger retrospective study 15 , but also consistent with series of previously published case reports and case-series regarding the lead positioning, choice of leads, days of trialing etc.
Also, interventional pain physicians who used such technology reported largely positive patient long-term experience, significant improvements in patient pain scores and opioid use.
Acknowledgement
We thank the following physicians on submitting their SCS cases : Drs Marshall Bedder, Salim Ghazi, Theresa Dews, Todd Jaffe, Prathima Reddy, Silviu Brill, David Walega, Allen W Burton, Carl Balog, Ross Dickstein, Oscar.Deleon Casasola, Padma Gulur, Gladstone C McDowell, Richard S Epter and Sudhir Diwan.
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