Neuromodulation: Technology at the Neural Interface Received: July 31, 2014
Revised: August 29, 2014
Accepted: September 10, 2014
(onlinelibrary.wiley.com) DOI: 10.1111/ner.12254
Spinal Cord Stimulator Explantation for Magnetic Resonance Imaging: A Case Series Susan M. Moeschler, MD; Rebecca A. Sanders, MD; W. Michael Hooten, MD; Bryan C. Hoelzer, MD Introduction: Spinal cord stimulator (SCS) systems are implanted to treat pain conditions such as neuropathic, radicular, and ischemic pain syndromes. Prior to July 2013, SCS systems were not magnetic resonance imaging (MRI) compatible due to the risk of thermal injury at the site of the leads and generator. Although there are some case reports of patients undergoing MRI studies with SCS systems in place, these stimulators are frequently explanted when clinical care has necessitated an MRI. The purpose of this case series is to discuss the role of SCS explantation in order to acquire an MRI. Methods: This study was performed at a tertiary academic pain medicine clinic. After exempt status was obtained via the institutional review board, patients were identified via the use of Common Procedural Terminology codes for implantable devices. A chart review was performed to identify all patients >18 years of age who had a lumbar or thoracic dorsal column SCS implanted during January 2001–December 2011. The charts were then followed to identify any patients who underwent a surgery for explantation of the device. Data collection included the total number of patients undergoing permanent SCS implantation, the total number of explantation of these devices, patient demographic factors, indication for SCS implantation, incidence of revisions and the indication, duration between implantation and explant of the device, and indication for explantation. Results: During the time between 2001 and 2011, 199 patients were identified who underwent a thoracic or lumbar SCS implant after a successful trial. Among 199 implants, 33 devices were explanted, and of these, four were explanted due to the primary need for an MRI scan. Keywords: Case series, contraindications, MRI, spinal cord stimulation, stimulation Conflict of Interest: The authors reported no conflict of interest.
INTRODUCTION
METHODS
Spinal cord stimulator (SCS) systems are implanted to treat pain conditions such as neuropathic, radicular, and ischemic pain syndromes (1–4). SCS implantation comes with known risks, including infection, lead migration, and device malfunction (5–7). Furthermore, prior to July 2013, SCS systems were not magnetic resonance imaging (MRI) compatible (8). Although algorithms have been proposed to perform MRI studies on patients with an indwelling system in the event than an MRI is clinically indicated (9), these practices have not been widely accepted in the United States nor have they been approved by the Food and Drug Administration. Additionally, there are case reports of patients (unintentionally) undergoing MRI studies with SCS systems in place (10). Due to the ferromagnetic materials found in SCS systems, these patients are at risk of thermal injury at the site of the leads and generator (11,12). In the past, these stimulators have been explanted when clinical care has necessitated an MRI study. The introduction of the MRI compatible SCS system has caused a great deal of discussion in the pain community, given the possibility of avoiding explantation of SCS systems in patients who may require an MRI. To our knowledge, there has been no formal publication regarding SCS explantation for the indication of obtaining an MRI. The purpose of this case series is to discuss the need for SCS explantation in order to acquire an MRI.
This study was performed at a tertiary academic pain medicine clinic. After exempt status was obtained via the institutional review board, patients were identified via the use of Common Procedural Terminology codes for implantable devices. A chart review was then performed to identify all patients >18 years of age who had a lumbar or thoracic dorsal column SCS implanted during January 2001–December 2011. The charts were then followed forward to identify any patients who underwent a surgery for explantation of the device. Data collection included the total number of patients undergoing permanent SCS implantation as well as explantation of these
Department of Anesthesiology, Mayo Clinic, Rochester, MN, USA For more information on author guidelines, an explanation of our peer review process, and conflict of interest informed consent policies, please go to http:// www.wiley.com/bw/submit.asp?ref=1094-7159&site=1 Source of financial support: No funding sources were used to support this manuscript.
© 2014 International Neuromodulation Society
Neuromodulation 2015; 18: 285–288
285
www.neuromodulationjournal.com
Address correspondence to: Susan M. Moeschler, MD, Department of Anesthesiology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA. Email: [email protected]
MOESCHLER ET AL. devices. Other data collection included patient demographic factors, indication for SCS implantation, incidence of revisions and the indication, duration between implantation and explant of the device, and indication for explantation. Clinical documents were reviewed, including physician notes, nursing charts, hospital notes, surgical reports, implant programming information, and radiograph studies.
RESULTS During the time between 2001 and 2011, 199 patients were identified who underwent a thoracic or lumbar SCS implant after a successful trial. Among 199 implants, 33 devices were explanted for various reasons including inadequate coverage, limited benefit, infection, battery failure, and need for MRI imaging. Of these 33, four were explanted due to the primary need for an MRI scan (Table 1). Most of the patients who required explantation developed a new pain or a symptom, which necessitated the MRI scan. In these cases, it was noted in the record that though the patient was receiving adequate pain relief, the need for the MRI required that the system be explanted. The duration from SCS implant to explant ranged from five months to 81 months. Devices from all three of the current SCS manufacturers were used over the study period: Boston Scientific, Medtronic, and St. Jude.
DISCUSSION Neuromodulation continues to be an important tool in our armamentarium against difficult to treat pain states (4). This is especially true as the pitfalls of chronic opioid therapy become better understood (13,14). Many of the patients who are good candidates for neuromodulation, such as those with failed back surgery syndrome, complex regional pain syndrome, oncologic origin of pain, as well as neuropathic pain, may develop a new symptom or disease that is monitored or diagnosed with the use of an MRI. Certainly, studies such as CT scans are an alternative in some cases—they become the only option if a patient has an indwelling SCS. Furthermore, an MRI is considered the gold standard for diagnosis or surveillance for a number of disease states including multiple sclerosis (15), central nervous system neoplasms (16), cerebral ischemia (17), and new or worsening headache (16). When clinicians evaluate a patient for SCS implantation, they must weigh the likelihood of needing a future MRI with the benefits that the patient will get from neuromodulation. In our clinical experience, there are some patients who meet the criteria for SCS but choose not to pursue the therapy secondary to the concern that they will be
unable to undergo an MRI scan in the future. In addition, we have noted that some physicians are resistant to refer patients for SCS evaluations due to the need for disease surveillance in the future. Prior to 2013, MRI conditional systems were simply not available and thus there is little mention of it within the pain literature. To date, studies have looked at the rate of explant and revision of SCS systems due to infection, suboptimal coverage, migration, and “other” reasons (5). It is likely that the need for advanced imaging, namely, MRI, falls within this “other” category. Indeed, within our practice, several patients who had an SCS implanted eventually had it explanted at least partially due to the need for an MRI. Of the 199 patient charts that were reviewed, eight patients were identified who underwent explantation and an MRI was listed as a reason for explantation. After further review of these patients, it was evident that several of them had an additional reason for the explant—such as suboptimal pain control—and thus the desire for an MRI was an additional factor. In four of the cases, the patient had a clinical indication that was best assessed by MRI, as determined by the medical provider, and thus the SCS system was removed. It is important to note that there is no way to assess the number of missed patients for whom SCS would have been beneficial. There are patients who have been excluded in the past from an SCS trial due to the need for tumor surveillance via MRI. In addition, some patients are never referred for consideration of an SCS trial simply because their disease or other clinical reasons prohibit non-MRI conditional implants. These numbers cannot be accurately assessed given that it depends not only on the interventionalist but also on the referring provider. When discussing the risks and benefits of neuromodulation to patients, we are obligated to educate the patient regarding the risks and benefits of the procedure, which include the contraindication of an MRI scan once an SCS system has been implanted (or at least until July 2013). Thus, the patient and provider take a calculated risk that the patient is unlikely to require an MRI in the future for any reason. One can argue that SCS is a reversible treatment insofar that it can be safely explanted, but it is a surgical procedure to do so. In addition, this comes with the loss of analgesia as provided by the SCS, which has likely been difficult to attain prior to the SCS, thus its placement. Finally, in the case of an emergent situation, such as a trauma, explantation may not be feasible. Further discussion with the patient regarding the risks of the procedure must be similar to that of any procedure including risk of bleeding, infection, risk to the spinal cord and nerves, and complications of the system. This is not meant to imply that the MRI conditional system is the only factor to be considered for patients but, rather, an additional factor that may be pertinent in a small
Table 1. Summary of All Four Patients Who Underwent SCS Explantation for the Indication of MRI. Patient #
Age/ gender
Year of implant
Indiction for SCS
Length of SCS therapy (months)
Indication for MRI
1 2 3 4
75/F 24/F 24/F 47/M
2005 2007 2004 2004
Phantom limb pain FBSS FBSS Angina
5 32 81 22
Concern for recurrent chest wall fibrosarcomas New onset of visual disturbances and occipital headache New location of back and radicular pain New onset of cervical spine pain and headache
286
SCS, spinal cord stimulator; MRI, magnetic resonance imaging; FBSS, failed back surgery syndrome.
www.neuromodulationjournal.com
© 2014 International Neuromodulation Society
Neuromodulation 2015; 18: 285–288
SPINAL CORD STIMULATOR, EXPLANTATION, MRI subset of patients with known neurologic, oncologic, or other pertinent medical histories. Most patients have not had an explant of the SCS system, and of those who did, it was more likely due to decreased use or limited benefit with time (Table 2). With a growing number of patients undergoing SCS treatment, the need for an MRI conditional system has become more important, though certainly not the only factor to be considered when choosing a system. Currently, one manufacturer has obtained approval for full-body MRI scanning for the labeled conditions (8). As described, at our institution, four patients required explantation for the primary indication of MRI scanning. This is a low percentage of the patients, 2%, who underwent explantation in order to have an MRI. However, for these four patients, it was a significant event in their lives in regard to a surgical procedure, recovery time, and the physical and economic burden as a result of such events. It will be interesting to see if the three major manufacturers of SCS systems will demonstrate a difference, or lack thereof, in explant rates for the primary indication of MRI scanning.
CONCLUSION SCS remains a mainstay therapy for several difficult to treat pain states. Failure of the systems and need for revision and explantation are frustrating for both the patient and the provider. Rates of migration and infection of these systems have improved over the past ten years, making SCS an even more attractive option for patients and providers alike (7). The use of MRI conditional systems may further expand the application of these devices for the benefit of a larger group of patients.
Authorship Statements Drs. Moeschler, Hooten, and Hoelzer designed the study and participated in writing and reviewing the manuscript. Dr. Sanders performed the chart review and assisted in writing the manuscript. Dr. Moeschler submitted the manuscript.
Table 2. Summary of All Patients Who Underwent SCS Explantation. Year of implant
Age/ gender
Indiction for SCS
Length of SCS therapy (months)
Indication for explant
2009 2005 2003 2005 2005 2006 2004 2005 2008
52/F 49/M 65/F 26/M 62/F 53/F 42/F 44/F 68/F
Venous insufficiency with pain Angina Angina FBSS FBSS FBSS CRPS CRPS FBSS
5 67 36 30 13 9 49 11 25
2006
31/F
Refractory interstitial cystitis
6
2006 2002 2005 2008
36/F 44/F 44/F 24/F
FBSS Ilioinguinal neuropathy Abdominal pain FBSS
12 2 9 21
2008 2008 2007 2009 2010 2009 2011 2009 2011 2011
43/F 67/M 50/F 54/F 53/M 27/M 45/F 52/M 21/M 27/M
CRPS FBSS CRPS Venous insufficiency with pain FBSS FBSS CRPS FBSS Neuropathic abdominal pain Lumbosacral avulsion injury
4 12 2 4 39 1 5 3 15 9
2011 2006 2007 2009 2010
44/F 37/F 43/M 70/F 36/M
CRPS FBSS Angina FBSS FBSS
19 41 24 1 2
Inadequate coverage of painful area Underwent heart transplant, no longer needed stimulation Decreased symptoms following EECP* IPG site tenderness, despite good pain relief No pain relief despite adequate coverage No pain relief despite adequate coverage Significant pain improvement, no longer required stimulation Painful stimulation (headache) (1) Decreased use (2) Patient desire for MRI to assess degree of spinal stenosis (1) Painful stimulation (2) Improvement of cystitis pain IPG site tenderness Unable to reposition lead after lead migration Inadequate stimulation (1) IPG site tenderness (2) Patient desire for future MRI to evaluate new cervical back pain Inadequate coverage of pain following lead migration Inadequate stimulation IPG site tenderness Inadequate coverage of painful areas Decreased use of stimulation Adequate coverage but no analgesia benefit Painful stimulation Limited analgesia benefit Limited analgesia benefit (1) Battery failure (2) Improvement of pain Decreased use of stimulation Infection following revision (thoracic epidural abscess) Superficial cellulitis over IPG site, without evidence of device infection Lumbar site drainage Concern for infection
www.neuromodulationjournal.com
© 2014 International Neuromodulation Society
287
*Enhanced external counterpulsation therapy. SCS, spinal cord stimulator; FBSS, failed back surgery syndrome; CRPS, complex regional pain syndrome.
Neuromodulation 2015; 18: 285–288
MOESCHLER ET AL.
COMMENT
How to Cite this Article: Moeschler S.M., Sanders R.A., Hooten W.M., Hoelzer B.C. 2015. Spinal Cord Stimulator Explantation for Magnetic Resonance Imaging: A Case Series. Neuromodulation 2015; 18: 285–288
This paper shows that there is value to MRI conditional spinal cord stimulator technology. It also shows that the majority of patients with stimulator can receive their medical care without the use of MRI, probably because of the many imaging alternatives available. Physicians should choose the device carefully based on patient needs.
REFERENCES 1. North RB, Kumar K, Wallace MS et al. Spinal cord stimulation versus re-operation in patients with failed back surgery syndrome: an international multicenter randomized controlled trial (EVIDENCE study). Neuromodulation 2011;14:330–335, discussion 335–6. 2. Krames ES, Monis S, Poree L et al. Using the SAFE principles when evaluating electrical stimulation therapies for the pain of failed back surgery syndrome. Neuromodulation 2011;14:299–311, discussion 311. 3. Kumar K, North R, Taylor R et al. Spinal cord stimulation vs. conventional medical management: a prospective, randomized, controlled, multicenter study of patients with failed back surgery syndrome (PROCESS study). Neuromodulation 2005;8:213– 218. 4. Kumar K, Taylor RS, Jacques L et al. Spinal cord stimulation versus conventional medical management for neuropathic pain: a multicentre randomised controlled trial in patients with failed back surgery syndrome. Pain 2007;132:179–188. 5. Mekhail NA, Mathews M, Nageeb F, Guirguis M, Mekhail MN, Cheng J. Retrospective review of 707 cases of spinal cord stimulation: indications and complications. Pain Pract 2011;11:148–153. 6. Bendersky D, Yampolsky C. Is spinal cord stimulation safe? A review of its complications. World Neurosurg 2013; e-pub ahead of print. 7. Gazelka HM, Freeman E, Hooten WM et al. Incidence of clinically significant percutaneous spinal cord stimulator lead migration. Neuromodulation 2014; e-pub ahead of print. 8. Neuromodulation MRI Safety Status. http://professional.medtronic.com/wcm/ groups/mdtcom_sg/@mdt/@neuro/documents/documents/mri-safety-status -us.pdf. 9. Mutter U, Bellut D, Porchet F et al. Spinal magnetic resonance imaging with reduced specific absorption rate in patients harbouring a spinal cord stimulation device—a single-centre prospective study analysing safety, tolerability and image quality. Acta Neurochir (Wien) 2013;155:2327–2332. 10. Simopoulos TT, Gill JS. Magnetic resonance imaging of the lumbar spine in a patient with a spinal cord stimulator. Pain Physician 2013;16:E295–E300. 11. Wilkoff BL, Albert T, Lazebnik M et al. Safe magnetic resonance imaging scanning of patients with cardiac rhythm devices: a role for computer modeling. Heart Rhythm 2013;10:1815–1821. 12. Coffey RJ, Kalin R, Olsen JM. Magnetic resonance imaging conditionally safe neurostimulation leads: investigation of the maximum safe lead tip temperature. Neurosurgery 2014; 74:215–224. 13. Mao L, Lin S, Lin J. The effects of anesthetics on tumor progression. Int J Physiol Pathophysiol Pharmacol 2013;5:1–10. 14. Brack A, Rittner HL, Stein C. Immunosuppressive effects of opioids—clinical relevance. J Neuroimmune Pharmacol 2011;6:490–502. 15. McDonald WI, Compston A, Edan G et al. Recommended diagnostic criteria for multiple sclerosis: guidelines from the international panel on the diagnosis of multiple sclerosis. Ann Neurol 2001;50:121–127. 16. Buckner JC, Brown PD, O’Neill BP, Meyer FB, Wetmore CJ, Uhm J. Central nervous system tumors. Mayo Clin Proc 2007;82:1271–1286. 17. Hacke W, Albers G, Al-Rawi Y et al. The Desmoteplase in Acute Ischemic Stroke Trial (DIAS): a phase II MRI-based 9-hour window acute stroke thrombolysis trial with intravenous desmoteplase. Stroke 2005;36:66–73.
Garry Gold, MD Stanford, CA, USA
Comments not included in the Early View version of this paper.
288 www.neuromodulationjournal.com
© 2014 International Neuromodulation Society
Neuromodulation 2015; 18: 285–288
Revised: August 29, 2014
Accepted: September 10, 2014
(onlinelibrary.wiley.com) DOI: 10.1111/ner.12254
Spinal Cord Stimulator Explantation for Magnetic Resonance Imaging: A Case Series Susan M. Moeschler, MD; Rebecca A. Sanders, MD; W. Michael Hooten, MD; Bryan C. Hoelzer, MD Introduction: Spinal cord stimulator (SCS) systems are implanted to treat pain conditions such as neuropathic, radicular, and ischemic pain syndromes. Prior to July 2013, SCS systems were not magnetic resonance imaging (MRI) compatible due to the risk of thermal injury at the site of the leads and generator. Although there are some case reports of patients undergoing MRI studies with SCS systems in place, these stimulators are frequently explanted when clinical care has necessitated an MRI. The purpose of this case series is to discuss the role of SCS explantation in order to acquire an MRI. Methods: This study was performed at a tertiary academic pain medicine clinic. After exempt status was obtained via the institutional review board, patients were identified via the use of Common Procedural Terminology codes for implantable devices. A chart review was performed to identify all patients >18 years of age who had a lumbar or thoracic dorsal column SCS implanted during January 2001–December 2011. The charts were then followed to identify any patients who underwent a surgery for explantation of the device. Data collection included the total number of patients undergoing permanent SCS implantation, the total number of explantation of these devices, patient demographic factors, indication for SCS implantation, incidence of revisions and the indication, duration between implantation and explant of the device, and indication for explantation. Results: During the time between 2001 and 2011, 199 patients were identified who underwent a thoracic or lumbar SCS implant after a successful trial. Among 199 implants, 33 devices were explanted, and of these, four were explanted due to the primary need for an MRI scan. Keywords: Case series, contraindications, MRI, spinal cord stimulation, stimulation Conflict of Interest: The authors reported no conflict of interest.
INTRODUCTION
METHODS
Spinal cord stimulator (SCS) systems are implanted to treat pain conditions such as neuropathic, radicular, and ischemic pain syndromes (1–4). SCS implantation comes with known risks, including infection, lead migration, and device malfunction (5–7). Furthermore, prior to July 2013, SCS systems were not magnetic resonance imaging (MRI) compatible (8). Although algorithms have been proposed to perform MRI studies on patients with an indwelling system in the event than an MRI is clinically indicated (9), these practices have not been widely accepted in the United States nor have they been approved by the Food and Drug Administration. Additionally, there are case reports of patients (unintentionally) undergoing MRI studies with SCS systems in place (10). Due to the ferromagnetic materials found in SCS systems, these patients are at risk of thermal injury at the site of the leads and generator (11,12). In the past, these stimulators have been explanted when clinical care has necessitated an MRI study. The introduction of the MRI compatible SCS system has caused a great deal of discussion in the pain community, given the possibility of avoiding explantation of SCS systems in patients who may require an MRI. To our knowledge, there has been no formal publication regarding SCS explantation for the indication of obtaining an MRI. The purpose of this case series is to discuss the need for SCS explantation in order to acquire an MRI.
This study was performed at a tertiary academic pain medicine clinic. After exempt status was obtained via the institutional review board, patients were identified via the use of Common Procedural Terminology codes for implantable devices. A chart review was then performed to identify all patients >18 years of age who had a lumbar or thoracic dorsal column SCS implanted during January 2001–December 2011. The charts were then followed forward to identify any patients who underwent a surgery for explantation of the device. Data collection included the total number of patients undergoing permanent SCS implantation as well as explantation of these
Department of Anesthesiology, Mayo Clinic, Rochester, MN, USA For more information on author guidelines, an explanation of our peer review process, and conflict of interest informed consent policies, please go to http:// www.wiley.com/bw/submit.asp?ref=1094-7159&site=1 Source of financial support: No funding sources were used to support this manuscript.
© 2014 International Neuromodulation Society
Neuromodulation 2015; 18: 285–288
285
www.neuromodulationjournal.com
Address correspondence to: Susan M. Moeschler, MD, Department of Anesthesiology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA. Email: [email protected]
MOESCHLER ET AL. devices. Other data collection included patient demographic factors, indication for SCS implantation, incidence of revisions and the indication, duration between implantation and explant of the device, and indication for explantation. Clinical documents were reviewed, including physician notes, nursing charts, hospital notes, surgical reports, implant programming information, and radiograph studies.
RESULTS During the time between 2001 and 2011, 199 patients were identified who underwent a thoracic or lumbar SCS implant after a successful trial. Among 199 implants, 33 devices were explanted for various reasons including inadequate coverage, limited benefit, infection, battery failure, and need for MRI imaging. Of these 33, four were explanted due to the primary need for an MRI scan (Table 1). Most of the patients who required explantation developed a new pain or a symptom, which necessitated the MRI scan. In these cases, it was noted in the record that though the patient was receiving adequate pain relief, the need for the MRI required that the system be explanted. The duration from SCS implant to explant ranged from five months to 81 months. Devices from all three of the current SCS manufacturers were used over the study period: Boston Scientific, Medtronic, and St. Jude.
DISCUSSION Neuromodulation continues to be an important tool in our armamentarium against difficult to treat pain states (4). This is especially true as the pitfalls of chronic opioid therapy become better understood (13,14). Many of the patients who are good candidates for neuromodulation, such as those with failed back surgery syndrome, complex regional pain syndrome, oncologic origin of pain, as well as neuropathic pain, may develop a new symptom or disease that is monitored or diagnosed with the use of an MRI. Certainly, studies such as CT scans are an alternative in some cases—they become the only option if a patient has an indwelling SCS. Furthermore, an MRI is considered the gold standard for diagnosis or surveillance for a number of disease states including multiple sclerosis (15), central nervous system neoplasms (16), cerebral ischemia (17), and new or worsening headache (16). When clinicians evaluate a patient for SCS implantation, they must weigh the likelihood of needing a future MRI with the benefits that the patient will get from neuromodulation. In our clinical experience, there are some patients who meet the criteria for SCS but choose not to pursue the therapy secondary to the concern that they will be
unable to undergo an MRI scan in the future. In addition, we have noted that some physicians are resistant to refer patients for SCS evaluations due to the need for disease surveillance in the future. Prior to 2013, MRI conditional systems were simply not available and thus there is little mention of it within the pain literature. To date, studies have looked at the rate of explant and revision of SCS systems due to infection, suboptimal coverage, migration, and “other” reasons (5). It is likely that the need for advanced imaging, namely, MRI, falls within this “other” category. Indeed, within our practice, several patients who had an SCS implanted eventually had it explanted at least partially due to the need for an MRI. Of the 199 patient charts that were reviewed, eight patients were identified who underwent explantation and an MRI was listed as a reason for explantation. After further review of these patients, it was evident that several of them had an additional reason for the explant—such as suboptimal pain control—and thus the desire for an MRI was an additional factor. In four of the cases, the patient had a clinical indication that was best assessed by MRI, as determined by the medical provider, and thus the SCS system was removed. It is important to note that there is no way to assess the number of missed patients for whom SCS would have been beneficial. There are patients who have been excluded in the past from an SCS trial due to the need for tumor surveillance via MRI. In addition, some patients are never referred for consideration of an SCS trial simply because their disease or other clinical reasons prohibit non-MRI conditional implants. These numbers cannot be accurately assessed given that it depends not only on the interventionalist but also on the referring provider. When discussing the risks and benefits of neuromodulation to patients, we are obligated to educate the patient regarding the risks and benefits of the procedure, which include the contraindication of an MRI scan once an SCS system has been implanted (or at least until July 2013). Thus, the patient and provider take a calculated risk that the patient is unlikely to require an MRI in the future for any reason. One can argue that SCS is a reversible treatment insofar that it can be safely explanted, but it is a surgical procedure to do so. In addition, this comes with the loss of analgesia as provided by the SCS, which has likely been difficult to attain prior to the SCS, thus its placement. Finally, in the case of an emergent situation, such as a trauma, explantation may not be feasible. Further discussion with the patient regarding the risks of the procedure must be similar to that of any procedure including risk of bleeding, infection, risk to the spinal cord and nerves, and complications of the system. This is not meant to imply that the MRI conditional system is the only factor to be considered for patients but, rather, an additional factor that may be pertinent in a small
Table 1. Summary of All Four Patients Who Underwent SCS Explantation for the Indication of MRI. Patient #
Age/ gender
Year of implant
Indiction for SCS
Length of SCS therapy (months)
Indication for MRI
1 2 3 4
75/F 24/F 24/F 47/M
2005 2007 2004 2004
Phantom limb pain FBSS FBSS Angina
5 32 81 22
Concern for recurrent chest wall fibrosarcomas New onset of visual disturbances and occipital headache New location of back and radicular pain New onset of cervical spine pain and headache
286
SCS, spinal cord stimulator; MRI, magnetic resonance imaging; FBSS, failed back surgery syndrome.
www.neuromodulationjournal.com
© 2014 International Neuromodulation Society
Neuromodulation 2015; 18: 285–288
SPINAL CORD STIMULATOR, EXPLANTATION, MRI subset of patients with known neurologic, oncologic, or other pertinent medical histories. Most patients have not had an explant of the SCS system, and of those who did, it was more likely due to decreased use or limited benefit with time (Table 2). With a growing number of patients undergoing SCS treatment, the need for an MRI conditional system has become more important, though certainly not the only factor to be considered when choosing a system. Currently, one manufacturer has obtained approval for full-body MRI scanning for the labeled conditions (8). As described, at our institution, four patients required explantation for the primary indication of MRI scanning. This is a low percentage of the patients, 2%, who underwent explantation in order to have an MRI. However, for these four patients, it was a significant event in their lives in regard to a surgical procedure, recovery time, and the physical and economic burden as a result of such events. It will be interesting to see if the three major manufacturers of SCS systems will demonstrate a difference, or lack thereof, in explant rates for the primary indication of MRI scanning.
CONCLUSION SCS remains a mainstay therapy for several difficult to treat pain states. Failure of the systems and need for revision and explantation are frustrating for both the patient and the provider. Rates of migration and infection of these systems have improved over the past ten years, making SCS an even more attractive option for patients and providers alike (7). The use of MRI conditional systems may further expand the application of these devices for the benefit of a larger group of patients.
Authorship Statements Drs. Moeschler, Hooten, and Hoelzer designed the study and participated in writing and reviewing the manuscript. Dr. Sanders performed the chart review and assisted in writing the manuscript. Dr. Moeschler submitted the manuscript.
Table 2. Summary of All Patients Who Underwent SCS Explantation. Year of implant
Age/ gender
Indiction for SCS
Length of SCS therapy (months)
Indication for explant
2009 2005 2003 2005 2005 2006 2004 2005 2008
52/F 49/M 65/F 26/M 62/F 53/F 42/F 44/F 68/F
Venous insufficiency with pain Angina Angina FBSS FBSS FBSS CRPS CRPS FBSS
5 67 36 30 13 9 49 11 25
2006
31/F
Refractory interstitial cystitis
6
2006 2002 2005 2008
36/F 44/F 44/F 24/F
FBSS Ilioinguinal neuropathy Abdominal pain FBSS
12 2 9 21
2008 2008 2007 2009 2010 2009 2011 2009 2011 2011
43/F 67/M 50/F 54/F 53/M 27/M 45/F 52/M 21/M 27/M
CRPS FBSS CRPS Venous insufficiency with pain FBSS FBSS CRPS FBSS Neuropathic abdominal pain Lumbosacral avulsion injury
4 12 2 4 39 1 5 3 15 9
2011 2006 2007 2009 2010
44/F 37/F 43/M 70/F 36/M
CRPS FBSS Angina FBSS FBSS
19 41 24 1 2
Inadequate coverage of painful area Underwent heart transplant, no longer needed stimulation Decreased symptoms following EECP* IPG site tenderness, despite good pain relief No pain relief despite adequate coverage No pain relief despite adequate coverage Significant pain improvement, no longer required stimulation Painful stimulation (headache) (1) Decreased use (2) Patient desire for MRI to assess degree of spinal stenosis (1) Painful stimulation (2) Improvement of cystitis pain IPG site tenderness Unable to reposition lead after lead migration Inadequate stimulation (1) IPG site tenderness (2) Patient desire for future MRI to evaluate new cervical back pain Inadequate coverage of pain following lead migration Inadequate stimulation IPG site tenderness Inadequate coverage of painful areas Decreased use of stimulation Adequate coverage but no analgesia benefit Painful stimulation Limited analgesia benefit Limited analgesia benefit (1) Battery failure (2) Improvement of pain Decreased use of stimulation Infection following revision (thoracic epidural abscess) Superficial cellulitis over IPG site, without evidence of device infection Lumbar site drainage Concern for infection
www.neuromodulationjournal.com
© 2014 International Neuromodulation Society
287
*Enhanced external counterpulsation therapy. SCS, spinal cord stimulator; FBSS, failed back surgery syndrome; CRPS, complex regional pain syndrome.
Neuromodulation 2015; 18: 285–288
MOESCHLER ET AL.
COMMENT
How to Cite this Article: Moeschler S.M., Sanders R.A., Hooten W.M., Hoelzer B.C. 2015. Spinal Cord Stimulator Explantation for Magnetic Resonance Imaging: A Case Series. Neuromodulation 2015; 18: 285–288
This paper shows that there is value to MRI conditional spinal cord stimulator technology. It also shows that the majority of patients with stimulator can receive their medical care without the use of MRI, probably because of the many imaging alternatives available. Physicians should choose the device carefully based on patient needs.
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Garry Gold, MD Stanford, CA, USA
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Neuromodulation 2015; 18: 285–288
