Downloaded from http://jnis.bmj.com/ on June 26, 2015 - Published by group.bmj.com
Spine
ORIGINAL RESEARCH
Spinal cord stimulators in an outpatient interventional neuroradiology practice Jennifer Padwal,1 Mark M Georgy,2 Bassem A Georgy1 1
University of California, San Diego, La Jolla, USA 2 Canyon Crest Academy, San Diego, USA Correspondence to Dr Bassem A Georgy, San Diego Imaging, University of California San Diego, 5458 Coach Lane, San Diego, CA 92130, USA; [email protected] Received 30 July 2013 Revised 24 September 2013 Accepted 27 September 2013 Published Online First 22 October 2013
ABSTRACT Purpose Spinal cord stimulation is a known modality for the treatment of chronic back and neck pain. Traditionally, spine surgeons and pain physicians perform the procedures. We report our experience in performing neuromodulation procedures in an outpatient interventional neuroradiology practice. Methods A retrospective analysis of medical records of all trial and permanent implantation patients over a period of 4 years was performed. 45 patients (32 men) of median age 47 years were included in the study. The primary diagnoses were 23 cases of failed back or neck surgery syndrome, 12 cases of spinal stenosis, 4 cases of axial pain, 3 cases with reflex sympathetic dystrophy, 1 case of peripheral vascular disease, 1 case of phantom limb and 1 case of post-concussion syndrome. Results Thirty-four trials were performed in an outpatient clinic while 11 trials were performed in hospital outpatient settings. Trial periods were 3–7 days. 27 patients (60%) who reported ≥50% pain relief underwent a permanent implantation. An interventional neuroradiologist performed 17 implantations, while spine surgeons performed 10 implantations. 23 implants were epidural (19 lumbar and 4 cervical) and four implants were subcutaneous. During the follow-up period, three patients had infections (13%) and required removal of the device and two cases (8%) reported lead migration. Conclusions Neuromodulation procedures can be performed safely in an outpatient interventional radiology setting. Although the infection rate was relatively higher in this study population, the other complication rates and trial-to-implant ratio are similar to published data.
INTRODUCTION
To cite: Padwal J, Georgy MM, Georgy BA. J NeuroIntervent Surg 2014;6:708–711. 708
Spinal cord stimulation (SCS) is a technique commonly used to treat chronic intractable back and neck pain using coordinated electrical pulses sent through the spinal cord. There is substantial scientific evidence for the efficacy of SCS in the treatment of low back and lower extremity pain, with a success rate between 50% and 70%. Clinical indications include neuropathic pain from failed back surgery syndrome, chronic regional pain syndrome (CRPS-1 and CRPS-2), degenerative back pain with radicular and/or axial symptoms, intractable peripheral neuropathy, peripheral vascular disease not responding to other treatment modalities and intractable angina.1 Patients who are candidates for such treatment usually undergo a trial procedure where one or two leads are percutaneously inserted, traditionally in the epidural space. The leads are then attached to
an external pulse generator. The trial period ranges from a few days to 1 week, during which the patient tests the device and uses different programs to manage the pain. At the end of the trial period the leads are removed by simple retraction. If the trial is deemed successful, a permanent implantation is performed. Electrical leads are placed percutaneously or an electrical paddle is placed via a mini-laminectomy in the epidural space at the desired level. The leads are then tunneled under the skin and attached to the generator that is also placed in a prepared subcutaneous pocket, usually located in the buttocks area. Occasionally, leads can be placed in subcutaneous areas for certain indications such as occipital headache or axial post-laminectomy pain. Traditionally, spine surgeons and interventional pain physicians have performed both trials and implantations as part of their routine practice. Recently, interventional radiologists and neuroradiologists have performed more inpatient and outpatient spinal procedures and SCS has become an important part of this type of practice. The purpose of this work is to report and critique the early experiences of performing such procedures in an outpatient interventional neuroradiology practice focused on spine procedures.
MATERIAL AND METHODS Demographics A retrospective review of patient charts and medical records was performed over a 4-year period after receiving approval from the local Institutional Review Board. Patients were referred from the interventional radiology spine practice or local physicians. Inclusion criteria included patients who had failed all types of conservative treatment before being considered for the procedure. Conservative treatments include physical therapy, different spinal injections and pain medication therapy. The study included all patients who underwent a trial procedure and chose to proceed with or abstain from permanent implantation. Patients who were offered the procedure and opted not to participate in the trial were not included in the study. A post-procedural assessment was conducted for up to 3 years following the implantation. A total of 45 patients were included in the study (32 men), with a median age of 47 years. The primary diagnoses for the study included 23 cases of failed back or neck surgery syndrome (figure 1), 12 cases of spinal stenosis, 4 cases of axial pain, 3 cases of reflex sympathetic dystrophy, 1 case of peripheral vascular disease, 1
Padwal J, et al. J NeuroIntervent Surg 2014;6:708–711. doi:10.1136/neurintsurg-2013-010901
Downloaded from http://jnis.bmj.com/ on June 26, 2015 - Published by group.bmj.com
Spine case of phantom limb and 1 case of post-concussion syndrome and occipital neuralgia.
Trial procedure Both the trial and implantation procedures were performed on an outpatient basis. Thirty-four trials were performed in an outpatient office setting with no sedation except for local anesthesia. Eleven trials were performed in an outpatient hospital setting with conscious sedation. An adequately trained neurointerventional radiologist performed all trials. The patient was prepared and draped in the prone position. The epidural space was accessed, usually at the L1–2 level, angling steeply up from below the vertebral body using a 14 G Touhy needle. The loss-of-resistance technique was used to assess the location of the epidural space. The lead was manipulated under fluoroscopic guidance up to the T7–8 level. All except three patients required a second lead, which was placed parallel or staggered in relation to the first lead. A second lead is placed to ensure adequate coverage of painful areas. Lead positions were adjusted and tested until the patient felt paresthesia covering all the areas of his or her pain. Once the patient was satisfied with the position of the leads and the amplitude of the stimulation, the settings were recorded and the leads secured in position using the anchors provided or sutures to the skin. The lead and connecting wires were covered with a dressing and subsequently connected to the external charger. Anteroposterior and lateral images were taken to document lead locations as a reference for the rest of the patient’s trial period. Patients recovered for about 1 h, during which time they became familiar with the different programs and functions of the external charger. The patients were then sent home with instructions regarding the use of and care for their trial implant. The trial period ranged from 3 days to 1 week, during which time the patient manipulated the different programs and recorded their pain level, activity and use of pain medications. At the end of the trial period the leads were removed by simple retraction and hemostasis was achieved. The trial period was then discussed with the patient regarding pain level, ability to perform different activities with the leads implanted and the use of pain medications. A successful trial was defined as a reduction in pain level of ≥50% calculated on a visual analogue scale. In cases of cervical epidural lead placement, a similar technique was used except that the entry point to the epidural space was around the T1–T2 level. The leads were usually advanced up to the level of the C2 vertebra. In subcutaneous lead implantation, the Touhy needle was used to insert the leads into the subcutaneous tissue at the center of the painful area. It is very important to emphasize that constant patient education and communication with the treating physician and office staff are crucial for the success of this technique, especially during the trial period and shortly after implantation.
Permanent implantation techniques
Figure 1 Typical case of a patient who underwent two back surgeries with residual bilateral radicular pain and failed all types of conservative treatment. (A) Typical epidural leads placed at the T7–T8 level. (B) Charger implanted in the left buttock with the leads tunneled in the subcutaneous tissue. Note the postoperative changes in the lumbar spine.
Placement of a permanent implant can be performed by inserting subcutaneous leads into the epidural space, in a fashion similar to that described in the trial technique. Occasionally a paddle lead is preferred in cases where subcutaneous leads exhibit excessive motion during the trial period or if modification of the coverage is needed for the permanent implant. In such cases, the procedure requires a minor laminectomy to place the paddle leads into the epidural space. This procedure is
Padwal J, et al. J NeuroIntervent Surg 2014;6:708–711. doi:10.1136/neurintsurg-2013-010901
709
Downloaded from http://jnis.bmj.com/ on June 26, 2015 - Published by group.bmj.com
Spine traditionally done by spine surgeons as it requires mini-laminectomy. Twenty-seven implants were performed in this clinical study. Seventeen cases were performed by a trained neurointerventional radiologist as a hospital outpatient procedure in the interventional suite and 10 cases were performed by the referring spine surgeons who preferred to do the implantation procedures themselves. Four of the latter cases were performed using paddle leads after mini-laminectomy and six were performed using subcutaneous leads. The subcutaneous leads were placed in a similar fashion to that described in the trial section. Once a satisfactory position was achieved, the patient was placed under deeper anesthesia and a paramedian incision was made to the skin and subcutaneous tissue. The Tuohy needles were then removed and the leads were anchored with non-absorbable sutures into the first fascial plane. A subcutaneous pocket similar to the size of the charger was created, usually on the buttocks below the belt line. The anchored leads were then tunneled under the skin into the pocket and attached to the charger. All the connections were tested and the position of the leads was confirmed by x-ray. The skin and deep layers of the subcutaneous tissue were then closed using typical surgical techniques. The patient was awakened and recovered in a normal manner, and received instructions on how to use the device. Patients were seen at 7–10 days in the office for typical incision care.
RESULTS A total of 45 trials were performed and 27 patients proceeded to permanent implantation, a trial-to-implant ratio of about 60%. Twenty-three implants were epidural (19 lumbar and 4 cervical) and four cases were subcutaneous. During the follow-up period, three patients had infections (13%) which necessitated removal of the device and two (8%) presented with evidence of lead migration. Regarding the cases of infection, the first case developed 4 days after implantation and the second case was an intravenous drug abuser and developed an infection 6 months after implantation. The third case developed an atypical infection 3 months after implantation at the site of the charger and failed to respond to antibiotics; upon blood testing the patient was found to have leukemia that had not been previously identified. In all three cases the whole device (leads and charger) was removed to avoid the spread of infection into the spine and intravenous antibiotics were administered. During the trial procedures one case developed severe bleeding at the site of the lead entry into the skin that did not respond to pressure for hemostasis. The lead was removed and the trial was continued with the second lead. We also encountered one case of implant malfunction after 2 years of implantation. Eighteen patients failed the trial process and did not proceed for a permanent implantation; 17 reported less than 50% pain relief and one patient did not like the feeling of the leads in his back.
DISCUSSION Although pain physicians and spine surgeons have routinely performed spinal cord stimulator implantation, this work shows that, with sufficient clinical skills and knowledge, trained interventional radiologists may safely perform the procedure in an outpatient setting. The main mechanism of action is based on the original work described by the gate control theory of the relief of pain proposed by Melzack and Wall in 1965.2 The gate hypothesis 710
suggests that excitatory and inhibitory interneurons within the nocioceptive pathway in the spinal cord modulate the processing of pain signals at the ‘gate’ to the brain. It was proposed that activation of the large highly myelinated Aβ fibers proximal to the orthodromic path of stimulation within the spinal cord creates a decrease in the release of excitatory neurotransmitters and an increase in the release of inhibitory neurotransmitters for the C fibers.3 Other mechanisms of action described in the literature include4 blockage of the transmission in the spinothalamic tract, supraspinal pain inhibition, activation of the central inhibitory mechanisms influencing sympathetic efferent neurons that explain the anti-ischemic and anti-angina effect, and activation of the putative neurotransmitters or neuromodulation. At the cellular level, animal studies suggest that SCS promotes the release of substance P, serotonin, noradrenaline, glycine and gamma-aminobutyric acid (GABA) in the dorsal horns. Activation of the GABA-B receptor may be associated with a reduction in the release of glutamate and other excitatory amino acids, leading to pain modulation.5 Generally, patients with radicular pain to the lower extremities seem to respond better to SCS than patients with isolated axial low back pain.1 Chronic and spontaneous afferent activity can be inhibited by electrical stimulation of the proximal portion of the afferent nerve, suggesting another mechanism through which peripheral nerve stimulation may decrease at least neuropathic pain.6 Other proposed mechanisms of pain relief include subcutaneous electrical conduction, dermatomal and myotomal electrical stimulation, partial sympathetic blockage and local blood flow alternation.7 Many complications have been described in the literature,8 the most common of which are infections, lead migration and dislodging and malfunction of the chargers. In our series two cases (8%) reported lead migration. The incidence rate of this complication is lower than the rate reported in the literature of between 11%8 and 21%.9 Three of the cases (13%) developed infection, which is higher than the rate reported in literature of 4.5%.10 However, upon further examination of the cases, one patient was found to be an intravenous drug abuser who developed an infection 6 months after the implantation, and another patient who developed an infection after 3 months was found to have previously undiscovered leukemia. All three patients who developed infection underwent implant removal and treatment with antibiotics. We also encountered a case of uncontrollable bleeding during placement of one of the trial leads, which necessitated removal of the lead and the trial continued with one lead. Of the 45 trial procedures performed, 27 patients chose to receive a permanent implant, creating a trial-to-implant ratio of 60%, which is only slightly below the average trial-to-implant ratio reported in the literature of 65–83%.10 With a larger sample size, the trial-to-implant ratio would most likely rise. Limitations of the study include a relatively small sample size, the retrospective nature of the study and the fact that it was performed in a single-center setting. However, given that there have been no prior studies of this nature, our aim with this retrospective evaluation was to provide an appropriate foundation for the design and implementation of future controlled prospective studies. The main purpose of the study is to stimulate the interventional radiology community—especially those who have skill in spinal injections—to adapt this technique as part of their routine practice and to provide groundwork for prospective evaluation of the safety and efficacy of these techniques in radiology practice.
Padwal J, et al. J NeuroIntervent Surg 2014;6:708–711. doi:10.1136/neurintsurg-2013-010901
Downloaded from http://jnis.bmj.com/ on June 26, 2015 - Published by group.bmj.com
Spine In conclusion, this study shows that SCS could be effectively and safely performed in an outpatient interventional radiology setting with sufficient training and clinical knowledge. Although the infection rate was relatively higher in this study population, the other complication rates and trial-to-implant ratio for this study are comparable to published data in the literature.
2 3
Contributors BAG performed the procedures and reviewed the manuscript. JP collected data and wrote the manuscript. MMG collected data and reviewed the manuscript.
6
4
5
7
Competing interests None. Patient consent Obtained. Ethics approval Ethics approval was obtained from the Palomar Health Investigational Review Committee.
8 9
Provenance and peer review Not commissioned; externally peer reviewed.
REFERENCES 1
10
Stojanovic MP, Abdi S. Spinal cord stimulation: a focused review. Pain Physician 2002;5:156–66.
Padwal J, et al. J NeuroIntervent Surg 2014;6:708–711. doi:10.1136/neurintsurg-2013-010901
Melzack R, Wall P. Pain mechanisms: a new theory. Science 1965;150:971–8. Smits H, van Kleef M, Holsheimer J, et al. Experimental spinal cord stimulation and neuropathic pain: mechanism of action, technical aspects, and effectiveness. Pain Pract 2012;13:154–68. Pinzon E. Spinal cord stimulation: an overview and case study of spinal cord (dorsal column) stimulation in a spine-centered/orthopaedic clinical practice setting. Pract Pain Manag 2005:69–75. Jeon Y, Huh BK. Spinal cord stimulation for chronic pain. Ann Acad Med Singapore 2009;38:998–1003. Burchiel KJ. Effects of electrical and mechanical stimulation on two foci of spontaneous activity which develop in primary afferent neurons after peripheral axotomy. Pain 1984;18:249–65. Bartsch T, Goodsby PJ. Stimulation of the greater occipital nerve induces increased central excitability of dural afferent input. Brain 2002;125:1496–509. Rosenow JM, Stanton-Hicks M, Rezai AR, et al. Failure modes of spinal cord stimulation hardware. J Neurosurg Spine 2006;5:183–90. Kumar K, Hunter G, Demeria D. Spinal cord stimulation in treatment of chronic benign pain: challenges in treatment planning and present status, a 22-year experience. Neurosurgery 2006;58:481–96. Mekhail NA, Mathews M, Nageeb F, et al. Retrospective review of 707 cases of spinal cord stimulation: indications and complications. Pain Pract 2011;11:148–53.
711
Downloaded from http://jnis.bmj.com/ on June 26, 2015 - Published by group.bmj.com
Spinal cord stimulators in an outpatient interventional neuroradiology practice Jennifer Padwal, Mark M Georgy and Bassem A Georgy J NeuroIntervent Surg 2014 6: 708-711 originally published online October 22, 2013
doi: 10.1136/neurintsurg-2013-010901 Updated information and services can be found at: http://jnis.bmj.com/content/6/9/708
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Spine
ORIGINAL RESEARCH
Spinal cord stimulators in an outpatient interventional neuroradiology practice Jennifer Padwal,1 Mark M Georgy,2 Bassem A Georgy1 1
University of California, San Diego, La Jolla, USA 2 Canyon Crest Academy, San Diego, USA Correspondence to Dr Bassem A Georgy, San Diego Imaging, University of California San Diego, 5458 Coach Lane, San Diego, CA 92130, USA; [email protected] Received 30 July 2013 Revised 24 September 2013 Accepted 27 September 2013 Published Online First 22 October 2013
ABSTRACT Purpose Spinal cord stimulation is a known modality for the treatment of chronic back and neck pain. Traditionally, spine surgeons and pain physicians perform the procedures. We report our experience in performing neuromodulation procedures in an outpatient interventional neuroradiology practice. Methods A retrospective analysis of medical records of all trial and permanent implantation patients over a period of 4 years was performed. 45 patients (32 men) of median age 47 years were included in the study. The primary diagnoses were 23 cases of failed back or neck surgery syndrome, 12 cases of spinal stenosis, 4 cases of axial pain, 3 cases with reflex sympathetic dystrophy, 1 case of peripheral vascular disease, 1 case of phantom limb and 1 case of post-concussion syndrome. Results Thirty-four trials were performed in an outpatient clinic while 11 trials were performed in hospital outpatient settings. Trial periods were 3–7 days. 27 patients (60%) who reported ≥50% pain relief underwent a permanent implantation. An interventional neuroradiologist performed 17 implantations, while spine surgeons performed 10 implantations. 23 implants were epidural (19 lumbar and 4 cervical) and four implants were subcutaneous. During the follow-up period, three patients had infections (13%) and required removal of the device and two cases (8%) reported lead migration. Conclusions Neuromodulation procedures can be performed safely in an outpatient interventional radiology setting. Although the infection rate was relatively higher in this study population, the other complication rates and trial-to-implant ratio are similar to published data.
INTRODUCTION
To cite: Padwal J, Georgy MM, Georgy BA. J NeuroIntervent Surg 2014;6:708–711. 708
Spinal cord stimulation (SCS) is a technique commonly used to treat chronic intractable back and neck pain using coordinated electrical pulses sent through the spinal cord. There is substantial scientific evidence for the efficacy of SCS in the treatment of low back and lower extremity pain, with a success rate between 50% and 70%. Clinical indications include neuropathic pain from failed back surgery syndrome, chronic regional pain syndrome (CRPS-1 and CRPS-2), degenerative back pain with radicular and/or axial symptoms, intractable peripheral neuropathy, peripheral vascular disease not responding to other treatment modalities and intractable angina.1 Patients who are candidates for such treatment usually undergo a trial procedure where one or two leads are percutaneously inserted, traditionally in the epidural space. The leads are then attached to
an external pulse generator. The trial period ranges from a few days to 1 week, during which the patient tests the device and uses different programs to manage the pain. At the end of the trial period the leads are removed by simple retraction. If the trial is deemed successful, a permanent implantation is performed. Electrical leads are placed percutaneously or an electrical paddle is placed via a mini-laminectomy in the epidural space at the desired level. The leads are then tunneled under the skin and attached to the generator that is also placed in a prepared subcutaneous pocket, usually located in the buttocks area. Occasionally, leads can be placed in subcutaneous areas for certain indications such as occipital headache or axial post-laminectomy pain. Traditionally, spine surgeons and interventional pain physicians have performed both trials and implantations as part of their routine practice. Recently, interventional radiologists and neuroradiologists have performed more inpatient and outpatient spinal procedures and SCS has become an important part of this type of practice. The purpose of this work is to report and critique the early experiences of performing such procedures in an outpatient interventional neuroradiology practice focused on spine procedures.
MATERIAL AND METHODS Demographics A retrospective review of patient charts and medical records was performed over a 4-year period after receiving approval from the local Institutional Review Board. Patients were referred from the interventional radiology spine practice or local physicians. Inclusion criteria included patients who had failed all types of conservative treatment before being considered for the procedure. Conservative treatments include physical therapy, different spinal injections and pain medication therapy. The study included all patients who underwent a trial procedure and chose to proceed with or abstain from permanent implantation. Patients who were offered the procedure and opted not to participate in the trial were not included in the study. A post-procedural assessment was conducted for up to 3 years following the implantation. A total of 45 patients were included in the study (32 men), with a median age of 47 years. The primary diagnoses for the study included 23 cases of failed back or neck surgery syndrome (figure 1), 12 cases of spinal stenosis, 4 cases of axial pain, 3 cases of reflex sympathetic dystrophy, 1 case of peripheral vascular disease, 1
Padwal J, et al. J NeuroIntervent Surg 2014;6:708–711. doi:10.1136/neurintsurg-2013-010901
Downloaded from http://jnis.bmj.com/ on June 26, 2015 - Published by group.bmj.com
Spine case of phantom limb and 1 case of post-concussion syndrome and occipital neuralgia.
Trial procedure Both the trial and implantation procedures were performed on an outpatient basis. Thirty-four trials were performed in an outpatient office setting with no sedation except for local anesthesia. Eleven trials were performed in an outpatient hospital setting with conscious sedation. An adequately trained neurointerventional radiologist performed all trials. The patient was prepared and draped in the prone position. The epidural space was accessed, usually at the L1–2 level, angling steeply up from below the vertebral body using a 14 G Touhy needle. The loss-of-resistance technique was used to assess the location of the epidural space. The lead was manipulated under fluoroscopic guidance up to the T7–8 level. All except three patients required a second lead, which was placed parallel or staggered in relation to the first lead. A second lead is placed to ensure adequate coverage of painful areas. Lead positions were adjusted and tested until the patient felt paresthesia covering all the areas of his or her pain. Once the patient was satisfied with the position of the leads and the amplitude of the stimulation, the settings were recorded and the leads secured in position using the anchors provided or sutures to the skin. The lead and connecting wires were covered with a dressing and subsequently connected to the external charger. Anteroposterior and lateral images were taken to document lead locations as a reference for the rest of the patient’s trial period. Patients recovered for about 1 h, during which time they became familiar with the different programs and functions of the external charger. The patients were then sent home with instructions regarding the use of and care for their trial implant. The trial period ranged from 3 days to 1 week, during which time the patient manipulated the different programs and recorded their pain level, activity and use of pain medications. At the end of the trial period the leads were removed by simple retraction and hemostasis was achieved. The trial period was then discussed with the patient regarding pain level, ability to perform different activities with the leads implanted and the use of pain medications. A successful trial was defined as a reduction in pain level of ≥50% calculated on a visual analogue scale. In cases of cervical epidural lead placement, a similar technique was used except that the entry point to the epidural space was around the T1–T2 level. The leads were usually advanced up to the level of the C2 vertebra. In subcutaneous lead implantation, the Touhy needle was used to insert the leads into the subcutaneous tissue at the center of the painful area. It is very important to emphasize that constant patient education and communication with the treating physician and office staff are crucial for the success of this technique, especially during the trial period and shortly after implantation.
Permanent implantation techniques
Figure 1 Typical case of a patient who underwent two back surgeries with residual bilateral radicular pain and failed all types of conservative treatment. (A) Typical epidural leads placed at the T7–T8 level. (B) Charger implanted in the left buttock with the leads tunneled in the subcutaneous tissue. Note the postoperative changes in the lumbar spine.
Placement of a permanent implant can be performed by inserting subcutaneous leads into the epidural space, in a fashion similar to that described in the trial technique. Occasionally a paddle lead is preferred in cases where subcutaneous leads exhibit excessive motion during the trial period or if modification of the coverage is needed for the permanent implant. In such cases, the procedure requires a minor laminectomy to place the paddle leads into the epidural space. This procedure is
Padwal J, et al. J NeuroIntervent Surg 2014;6:708–711. doi:10.1136/neurintsurg-2013-010901
709
Downloaded from http://jnis.bmj.com/ on June 26, 2015 - Published by group.bmj.com
Spine traditionally done by spine surgeons as it requires mini-laminectomy. Twenty-seven implants were performed in this clinical study. Seventeen cases were performed by a trained neurointerventional radiologist as a hospital outpatient procedure in the interventional suite and 10 cases were performed by the referring spine surgeons who preferred to do the implantation procedures themselves. Four of the latter cases were performed using paddle leads after mini-laminectomy and six were performed using subcutaneous leads. The subcutaneous leads were placed in a similar fashion to that described in the trial section. Once a satisfactory position was achieved, the patient was placed under deeper anesthesia and a paramedian incision was made to the skin and subcutaneous tissue. The Tuohy needles were then removed and the leads were anchored with non-absorbable sutures into the first fascial plane. A subcutaneous pocket similar to the size of the charger was created, usually on the buttocks below the belt line. The anchored leads were then tunneled under the skin into the pocket and attached to the charger. All the connections were tested and the position of the leads was confirmed by x-ray. The skin and deep layers of the subcutaneous tissue were then closed using typical surgical techniques. The patient was awakened and recovered in a normal manner, and received instructions on how to use the device. Patients were seen at 7–10 days in the office for typical incision care.
RESULTS A total of 45 trials were performed and 27 patients proceeded to permanent implantation, a trial-to-implant ratio of about 60%. Twenty-three implants were epidural (19 lumbar and 4 cervical) and four cases were subcutaneous. During the follow-up period, three patients had infections (13%) which necessitated removal of the device and two (8%) presented with evidence of lead migration. Regarding the cases of infection, the first case developed 4 days after implantation and the second case was an intravenous drug abuser and developed an infection 6 months after implantation. The third case developed an atypical infection 3 months after implantation at the site of the charger and failed to respond to antibiotics; upon blood testing the patient was found to have leukemia that had not been previously identified. In all three cases the whole device (leads and charger) was removed to avoid the spread of infection into the spine and intravenous antibiotics were administered. During the trial procedures one case developed severe bleeding at the site of the lead entry into the skin that did not respond to pressure for hemostasis. The lead was removed and the trial was continued with the second lead. We also encountered one case of implant malfunction after 2 years of implantation. Eighteen patients failed the trial process and did not proceed for a permanent implantation; 17 reported less than 50% pain relief and one patient did not like the feeling of the leads in his back.
DISCUSSION Although pain physicians and spine surgeons have routinely performed spinal cord stimulator implantation, this work shows that, with sufficient clinical skills and knowledge, trained interventional radiologists may safely perform the procedure in an outpatient setting. The main mechanism of action is based on the original work described by the gate control theory of the relief of pain proposed by Melzack and Wall in 1965.2 The gate hypothesis 710
suggests that excitatory and inhibitory interneurons within the nocioceptive pathway in the spinal cord modulate the processing of pain signals at the ‘gate’ to the brain. It was proposed that activation of the large highly myelinated Aβ fibers proximal to the orthodromic path of stimulation within the spinal cord creates a decrease in the release of excitatory neurotransmitters and an increase in the release of inhibitory neurotransmitters for the C fibers.3 Other mechanisms of action described in the literature include4 blockage of the transmission in the spinothalamic tract, supraspinal pain inhibition, activation of the central inhibitory mechanisms influencing sympathetic efferent neurons that explain the anti-ischemic and anti-angina effect, and activation of the putative neurotransmitters or neuromodulation. At the cellular level, animal studies suggest that SCS promotes the release of substance P, serotonin, noradrenaline, glycine and gamma-aminobutyric acid (GABA) in the dorsal horns. Activation of the GABA-B receptor may be associated with a reduction in the release of glutamate and other excitatory amino acids, leading to pain modulation.5 Generally, patients with radicular pain to the lower extremities seem to respond better to SCS than patients with isolated axial low back pain.1 Chronic and spontaneous afferent activity can be inhibited by electrical stimulation of the proximal portion of the afferent nerve, suggesting another mechanism through which peripheral nerve stimulation may decrease at least neuropathic pain.6 Other proposed mechanisms of pain relief include subcutaneous electrical conduction, dermatomal and myotomal electrical stimulation, partial sympathetic blockage and local blood flow alternation.7 Many complications have been described in the literature,8 the most common of which are infections, lead migration and dislodging and malfunction of the chargers. In our series two cases (8%) reported lead migration. The incidence rate of this complication is lower than the rate reported in the literature of between 11%8 and 21%.9 Three of the cases (13%) developed infection, which is higher than the rate reported in literature of 4.5%.10 However, upon further examination of the cases, one patient was found to be an intravenous drug abuser who developed an infection 6 months after the implantation, and another patient who developed an infection after 3 months was found to have previously undiscovered leukemia. All three patients who developed infection underwent implant removal and treatment with antibiotics. We also encountered a case of uncontrollable bleeding during placement of one of the trial leads, which necessitated removal of the lead and the trial continued with one lead. Of the 45 trial procedures performed, 27 patients chose to receive a permanent implant, creating a trial-to-implant ratio of 60%, which is only slightly below the average trial-to-implant ratio reported in the literature of 65–83%.10 With a larger sample size, the trial-to-implant ratio would most likely rise. Limitations of the study include a relatively small sample size, the retrospective nature of the study and the fact that it was performed in a single-center setting. However, given that there have been no prior studies of this nature, our aim with this retrospective evaluation was to provide an appropriate foundation for the design and implementation of future controlled prospective studies. The main purpose of the study is to stimulate the interventional radiology community—especially those who have skill in spinal injections—to adapt this technique as part of their routine practice and to provide groundwork for prospective evaluation of the safety and efficacy of these techniques in radiology practice.
Padwal J, et al. J NeuroIntervent Surg 2014;6:708–711. doi:10.1136/neurintsurg-2013-010901
Downloaded from http://jnis.bmj.com/ on June 26, 2015 - Published by group.bmj.com
Spine In conclusion, this study shows that SCS could be effectively and safely performed in an outpatient interventional radiology setting with sufficient training and clinical knowledge. Although the infection rate was relatively higher in this study population, the other complication rates and trial-to-implant ratio for this study are comparable to published data in the literature.
2 3
Contributors BAG performed the procedures and reviewed the manuscript. JP collected data and wrote the manuscript. MMG collected data and reviewed the manuscript.
6
4
5
7
Competing interests None. Patient consent Obtained. Ethics approval Ethics approval was obtained from the Palomar Health Investigational Review Committee.
8 9
Provenance and peer review Not commissioned; externally peer reviewed.
REFERENCES 1
10
Stojanovic MP, Abdi S. Spinal cord stimulation: a focused review. Pain Physician 2002;5:156–66.
Padwal J, et al. J NeuroIntervent Surg 2014;6:708–711. doi:10.1136/neurintsurg-2013-010901
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Spinal cord stimulators in an outpatient interventional neuroradiology practice Jennifer Padwal, Mark M Georgy and Bassem A Georgy J NeuroIntervent Surg 2014 6: 708-711 originally published online October 22, 2013
doi: 10.1136/neurintsurg-2013-010901 Updated information and services can be found at: http://jnis.bmj.com/content/6/9/708
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