Analysis of spinal canal diameter in the placement of thoracic spinal cord stimulator paddle leads.

BACKGROUND: Neurologic deficit is known as a rare complication of thoracic spinal cord stimulator (SCS) paddle lead implantation, but many believe its incidence after SCS paddle lead placement is under-reported. It is possible that imaging characteristics may be used to help predict safe paddle lead placement. OBJECTIVE: This imaging study was undertaken to determine the minimum canal diameter required for safe paddle lead placement. METHODS: Patients who underwent thoracic laminotomy for new SCS paddle lead placement from January 2018 to March 2023 were identified retrospectively. Preoperative thoracic canal diameter was measured in the sagittal plane perpendicular to the disc space from T5/6 to T11/12. These thoracic levels were chosen because they span the most common levels targeted for SCS placement. Patients with and without new neurologic deficits were compared using a Mann-Whitney U-test. RESULTS: Of 185 patients initially identified, 180 had thoracic imaging available for review. One (0.5%) and 2 (1.1%) of 185 patients complained of permanent and transient neurologic deficit after thoracic SCS placement, respectively. Patients with neurologic deficits had average canal diameters of <11 mm. The average canal diameter of patients with and without neurologic deficits was 10.2 mm (range 6.1-12.9 mm) and 13.0 mm (range 5.9-20.2), respectively (p < 0.0001). CONCLUSION: Postoperative neurologic deficit is an uncommon complication after thoracic laminotomy for SCS paddle lead placement. The authors recommend ensuring a starting thoracic canal diameter of at least 12 mm to accommodate a SCS paddle lead measuring 2 mm thick to ensure a final diameter of >10 mm. If canal diameter is <12 mm, aggressive undercutting of the lamina, a second laminotomy, or placement of smaller SCS wire leads should be considered.

Case report: Dorsal root ganglion stimulator lead fracture.

BACKGROUND: One of the unique advances in neuromodulation for chronic pain has been spinal cord stimulators (SCS) and dorsal root ganglion stimulators (DRG-S). These devices have aided in conditions such as neuropathic pain, complex regional pain syndromes, failed back surgery, and peripheral neuropathies. With these benefits, however, complications from implantable stimulators have included lead fractures and migration. The authors reviewed a lead migration, kinking, and subsequent fracture event involving a patient with complex regional pain syndrome (CRPS) II, who was treated with a DRG-S. CASE PRESENTATION: The case report follows this patient, from their past medical history to assessment of appropriate qualifications for neuromodulation, to successful surgical placement, to follow-up care. The authors further monitored assessment of inefficacy of pain relief, and identification of lead migration and kinking through imaging. In the process of removal, due to lead stress, lead fracturing occurred. After lead removal, the leads were fully replaced, and the patient was followed up and experienced improved pain relief. CONCLUSION: The case report assesses probable mechanisms of lead fracture and considerations for physicians for future assessment and triage of neuromodulation efficacy.

Neuromodulation for chronic pain.

Neuromodulation is an expanding area of pain medicine that incorporates an array of non-invasive, minimally invasive, and surgical electrical therapies. In this Series paper, we focus on spinal cord stimulation (SCS) therapies discussed within the framework of other invasive, minimally invasive, and non-invasive neuromodulation therapies. These therapies include deep brain and motor cortex stimulation, peripheral nerve stimulation, and the non-invasive treatments of repetitive transcranial magnetic stimulation, transcranial direct current stimulation, and transcutaneous electrical nerve stimulation. SCS methods with electrical variables that differ from traditional SCS have been approved. Although methods devoid of paraesthesias (eg, high frequency) should theoretically allow for placebo-controlled trials, few have been done. There is low-to-moderate quality evidence that SCS is superior to reoperation or conventional medical management for failed back surgery syndrome, and conflicting evidence as to the superiority of traditional SCS over sham stimulation or between different SCS modalities. Peripheral nerve stimulation technologies have also undergone rapid development and become less invasive, including many that are placed percutaneously. There is low-to-moderate quality evidence that peripheral nerve stimulation is effective for neuropathic pain in an extremity, low quality evidence that it is effective for back pain with or without leg pain, and conflicting evidence that it can prevent migraines. In the USA and many areas in Europe, deep brain and motor cortex stimulation are not approved for chronic pain, but are used off-label for refractory cases. Overall, there is mixed evidence supporting brain stimulation, with most sham-controlled trials yielding negative findings. Regarding non-invasive modalities, there is moderate quality evidence that repetitive transcranial magnetic stimulation does not provide meaningful benefit for chronic pain in general, but conflicting evidence regarding pain relief for neuropathic pain and headaches. For transcranial direct current stimulation, there is low-quality evidence supporting its benefit for chronic pain, but conflicting evidence regarding a small treatment effect for neuropathic pain and headaches. For transcutaneous electrical nerve stimulation, there is low-quality evidence that it is superior to sham or no treatment for neuropathic pain, but conflicting evidence for non-neuropathic pain. Future research should focus on better evaluating the short-term and long-term effectiveness of all neuromodulation modalities and whether they decrease health-care use, and on refining selection criteria and treatment variables.

Improving Limb Salvage for Chronic Limb-Threatening Ischemia With Spinal Cord Stimulation: A Retrospective Analysis.

INTRODUCTION: Chronic limb-threatening ischemia (CLTI) represents the most severe form of peripheral artery disease (PAD). Up to a third of CLTI patients are not eligible to receive first-line treatments such as bypass surgery or endovascular interventions. Epidural spinal cord stimulation (SCS) has been used as a method to improve microcirculatory blood flow and relieve ischemic pain in CTLI patients. The aim of the study was to evaluate limb salvage, ulcer closure, and clinical changes of SCS implanted CTLI patients at 1-year follow-up. METHODS: Eligible patients had end-stage lower limb PAD unresponsive to medical therapy and not amenable to surgical reconstruction. Patients were candidates for amputation, but limb loss was not inevitable (Fontaine stage III and IV). Pain intensity and skin temperature in the ischemic area (visual analogue scale), quality of life (WHOQoL-BREF), and ankle/brachial blood pressure index (ABI) were recorded at routine follow-up visits. Data were analyzed retrospectively. RESULTS: 29 patients underwent SCS implantation at one vascular center. The minimum follow-up period was 30 months. Limb survival at 1-year follow-up was 97% (28/29) and 73% (11/15) had complete closure of limb ulcers. Pain intensity, skin temperature, and quality of life progressively improved up to 12 months after implant, with Fontaine stage III patients improving more substantially than Fontaine stage IV patients. SCS therapy did not affect ABI measurement. No complications related to the device or procedure occurred. CONCLUSIONS: SCS is a valid alternative in patients unsuitable for revascularization. The quality of results depends on both a strict selection of patients by vascular specialists and the frequency of follow-up controls. The therapy may be more beneficial in patients classified as Fontaine stage III.

The relationship between maximum tolerance and motor activation during transcutaneous spinal stimulation is unaffected by the carrier frequency or vibration.

Transcutaneous spinal stimulation (TSS) is a useful tool to modulate spinal sensorimotor circuits and has emerged as a potential treatment for motor disorders in neurologically impaired populations. One major limitation of TSS is the discomfort associated with high levels of stimulation during the experimental procedure. The objective of this study was to examine if the discomfort caused by TSS can be alleviated using different stimulation paradigms in a neurologically intact population. Tolerance to TSS delivered using conventional biphasic balanced rectangular pulses was compared to two alternative stimulation paradigms: a 5 kHz carrier frequency and biphasic balanced rectangular pulses combined with vibrotactile stimulation. In ten healthy participants, tolerance to TSS was examined using both single-pulse (0.2 Hz) and continuous (30 Hz) stimulation protocols. In both the single-pulse and continuous stimulation protocols, participants tolerated significantly higher levels of stimulation with the carrier frequency paradigm compared to the other stimulation paradigms. However, when the maximum tolerable stimulation intensity of each stimulation paradigm was normalized to the intensity required to evoke a lower limb muscle response, there were no statistical differences between the stimulation paradigms. Our results suggest that, when considering the intensity of stimulation required to obtain spinally evoked motor potentials, neither alternative stimulation paradigm is more effective at reducing discomfort than the conventional, unmodulated pulse configuration.

The Use of Spinal Cord Stimulation/Neuromodulation in the Management of Chronic Pain.

Chronic pain causes a tremendous burden on the society in terms of economic factors and social costs. Rates of spinal surgery, especially spinal fusion, have increased exponentially over the past decade. The opioid epidemic in the United States has been one response to the management of pain, but it has been fraught with numerous catastrophic-related adverse effects. Clinically, spinal cord stimulation (SCS)/neuromodulation has been used in the management of chronic pain (especially spine-related pain) for more than two decades. More recent advances in this field have led to new theories and approaches in which SCS can be used in the management of chronic spine-related pain with precision and efficacy while minimizing adverse effects commonly seen with other forms of chronic pain treatment (eg, narcotics, injections, ablations). Narcotic medications have adverse effects of habituation, nausea, constipation, and the like. Injections sometimes lack efficacy and can have only limited duration of efficacy. Also, they can have adverse effects of cerebrospinal fluid leak, infection, and so on. Ablations can be associated with burning discomfort, lack of efficacy, recurrent symptoms, and infection. High-frequency stimulation, burst stimulation, tonic stimulation with broader paddles, and new stimulation targets such as the dorsal root ganglion hold promise for improved pain management via neuromodulation moving forward. Although a significant rate of complications with SCS technology are well described, this can be a useful tool in the management of chronic spine-related pain.

Pocket Pain and Neuromodulation: Negligible or Neglected?

OBJECTIVES: Pain encountered at the site of the implantable pulse generator (IPG) after invasive neuromodulation is a well-known and important complication. The reported incidence of implant site pain is variable, ranging between 0.4 and 35%. Implant site pain has never been systematically studied and no treatment guidelines are available. MATERIAL AND METHODS: We performed an observational study (study registration number mp05728) on the incidence and the determining factors of implant site pain, the subjective rating of intensity by sending questionnaires (n = 554) to our cohort of neuromodulation patients with IPGs. The number of revision surgeries and explants due to implant site pain were also analyzed. RESULTS: Total response rate was 50% (n = 278). Pain patients suffered significantly (p < 0.05) more often from IPG site pain than other patients undergoing neuromodulation therapies. Up to 64% of patients undergoing spinal cord stimulation reported IPG site discomfort or pain. Severe pocket pain was found in up to 8% of patients. No association was found between other variables (age, BMI, duration of follow-up, gender, smoking, number of pocket surgeries) and implant site pain. CONCLUSION: Pocket pain represents an important problem after invasive neuromodulation and is more prevalent in pain patients. We believe further technological improvements with miniaturized IPGs will impact the incidence of pocket pain and could even obviate the need for an IPG pocket.

Is spinal cord stimulation safe? A review of 13 years of implantations and complications.

OBJECTIVE: The aim of this review was to evaluate the complications of spinal cord stimulation (SCS) for chronic pain. METHODS: This was a retrospective case series of 212 patients treated with SCS for chronic lower-limb neuropathic pain between March 2002 and February 2015 in a Reims academic hospital. All patients received a surgically implanted paddle-type electrode. Complications with this technique are here described and analyzed, and other treatment and preventative methods proposed. RESULTS: The major indication was 'failed back surgery syndrome', and 74 (35%) patients experienced complications, of which 57% were benign, while 42% required invasive treatment. Most frequent complications (n=22, 10%) were hardware malfunctions. There were two cases (0.9%) of postoperative neurological deficit and nine (4.2%) with postoperative infections. All patients received the appropriate treatment for their complication. CONCLUSION: Despite the presence of complications, SCS is still a safe technique, although careful patient selection and proper surgical technique can help to avoid major complications.

Complications of Spinal Cord Stimulation and Peripheral Nerve Stimulation Techniques: A Review of the Literature.

OBJECTIVE: Spinal cord and peripheral neurostimulation techniques have been practiced since 1967 for the relief of pain, and some techniques are also used for improvement in organ function. Neuromodulation has recognized complications, although very rarely do these cause long-term morbidity. The aim of this article is to present a review of complications observed in patients treated with neurostimulation techniques. METHODS: A review of the major recent publications in the literature on the subjects of spinal cord, occipital, sacral, and peripheral nerve field stimulation was conducted. RESULTS: The incidence of complications reported varies from 30% to 40% of patients affected by one or more complications. Adverse events can be subdivided into hardware-related complications and biological complications. The commonest hardware-related complication is lead migration. Other lead related complications such as failure or fracture have also been reported. Common biological complications include infection and pain over the implant. Serious biological complications such as dural puncture headache and neurological damage are rarely observed. CONCLUSIONS: Spinal cord and peripheral neurostimulation techniques are safe and reversible therapies. Hardware-related complications are more commonly observed than biological complications. Serious adverse events such as neurological damage are rare.

National Perioperative Outcomes for Intrathecal Pump, Spinal Cord Stimulator, and Peripheral Nerve Stimulator Procedures.

BACKGROUND: There is abundant literature on the long-term complications of intrathecal pumps (ITP), spinal cord stimulators (SCS), and peripheral nerve stimulators (PNS) used in the treatment of chronic pain. There is less information, however, on the perioperative complications of these procedures. OBJECTIVE: Exploration of the perioperative outcomes of implantable pain devices. STUDY DESIGN: Observational study. SETTING: University hospitals, community hospitals, specialty hospitals, attached surgery centers, and freestanding surgery centers METHODS: Data were obtained from the National Anesthesia Clinical Outcomes Registry (NACOR) of the Anesthesia Quality Institute (AQI). Information was collected on patient demographics, procedure information, anesthetic administered, diagnosis linked to the procedure, and perioperative outcomes. RESULTS: The search yielded 12,611 ITP, 19,276 SCS, and 15,184 PNS cases from 2010 to 2014. In this sample, the majority of procedures were performed at community hospitals, not university medical centers. The most common diagnosis cited for an ITP was an implant complication (n = 2,570), followed by spasticity, and non-malignant back pain. For SCS, the most common diagnoses were lower back pain (n = 5,515) or radiculopathy (n = 2,398). For PNS, by far the most common diagnosis related to urinary dysfunction (n = 8,745), with painful bladder syndrome a small minority (n = 133). General anesthetics were more often performed for ITP than for SCS and PNS procedures (60.6% vs. 31.8% and 32.2%, respectively). Hemodynamic instability was a common outcome (13.9% for ITP procedures); other common outcomes for all the procedures included case delays, inadequate pain control, and extended PACU stays. LIMITATIONS: Despite the large sample size in this study, not all medical centers transmit their outcome data to NACOR. Furthermore, some institutions do not report clinical outcomes for every case to NACOR, making the sample size of assessing complications smaller and potentially more biased. Finally, procedures identified in the NACOR database using CPT may be similar but not identical and therefore potentially influence outcomes. CONCLUSIONS: Databases such as NACOR can provide rich information on ITP, SCS, and PNS for physicians performing these procedures. In this sample, ITP procedures, performed on the patients with the most severe cormobidities and often-requiring general anesthesia, were the most likely to be associated with hemodynamic instability, inadequate pain control, and extended PACU stays. Complications relating to the ITP are also the most common reason for an operation. These findings underscore the importance of proper patient selection for ITP and other implantable pain devices, in particular for patients with malignant pain or multiple co-morbidities. To identify the root causes of complications, additional information is needed on the procedure performed (e.g., an implant vs a revision), the surgical technique used, and the device implanted, as well as on specific patient comorbidities. Such information will likely become more available as resources like NACOR expand and as electronic medical record systems and coding become more integrated.

The appropriate use of neurostimulation: avoidance and treatment of complications of neurostimulation therapies for the treatment of chronic pain. Neuromodulation Appropriateness Consensus Committee.

INTRODUCTION: The International Neuromodulation Society (INS) has determined that there is a need for guidance regarding safety and risk reduction for implantable neurostimulation devices. The INS convened an international committee of experts in the field to explore the evidence and clinical experience regarding safety, risks, and steps to risk reduction to improve outcomes. METHODS: The Neuromodulation Appropriateness Consensus Committee (NACC) reviewed the world literature in English by searching MEDLINE, PubMed, and Google Scholar to evaluate the evidence for ways to reduce risks of neurostimulation therapies. This evidence, obtained from the relevant literature, and clinical experience obtained from the convened consensus panel were used to make final recommendations on improving safety and reducing risks. RESULTS: The NACC determined that the ability to reduce risk associated with the use of neurostimulation devices is a valuable goal and possible with best practice. The NACC has recommended several practice modifications that will lead to improved care. The NACC also sets out the minimum training standards necessary to become an implanting physician. CONCLUSIONS: The NACC has identified the possibility of improving patient care and safety through practice modification. We recommend that all implanting physicians review this guidance and consider adapting their practice accordingly.

Spinal cord stimulators in an outpatient interventional neuroradiology practice.

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.

Magnetic resonance imaging conditionally safe neurostimulation leads: investigation of the maximum safe lead tip temperature.

BACKGROUND: Magnetic resonance imaging (MRI) is preferred for imaging the central nervous system (CNS). An important hazard for neurostimulation patients is heating at the electrode interface induced, for example, by 64-MHz radiofrequency (RF) magnetic fields of a 1.5T scanner. OBJECTIVE: We performed studies to define the thermal dose (time and temperature) that would not cause symptomatic neurological injury. METHODS: Approaches included animal studies where leads with temperature probes were implanted in the brain or spine of sheep and exposed to RF-induced temperatures of 37 °C to 49 °C for 30 minutes. Histopathological examinations were performed 7 days after recovery. We also reviewed the threshold for RF lesions in the CNS, and for CNS injury from cancer hyperthermia. Cumulative equivalent minutes at 43 °C was used to normalize the data to exposure times and temperatures expected during MRI. RESULTS: Deep brain and spinal RF heating up to 43 °C for 30 minutes produced indistinguishable effects compared with 37 °C controls. Exposures greater than 43 °C for 30 minutes produced temperature-dependent, localized thermal damage. These results are consistent with limits on hyperthermia exposure to 41.8 °C for 60 minutes in patients who have cancer and with the reversibility of low-temperature and short-duration trial heating during RF lesion procedures. CONCLUSION: A safe temperature for induced lead heating is 43 °C for 30 minutes. MRI-related RF heating above 43 °C or longer than 30 minutes may be associated with increased risk of clinically evident thermal damage to neural structures immediately surrounding implanted leads. The establishment of a thermal dose limit is a first step toward making specific neurostimulation systems conditionally safe during MRI procedures.

Infectious complications related to intrathecal drug delivery system and spinal cord stimulator system implantations at a comprehensive cancer pain center.

BACKGROUND: Intrathecal drug delivery (IDD) and spinal cord stimulator (SCS) systems are implantable devices for the management of both chronic and cancer pain. Although these therapies have favorable long-term outcomes, they are associated with occasional complications including infection. The incidence of infectious complications varies from 2 - 8% and frequently requires prolonged antibiotics and device revision or removal. Cancer patients are particularly susceptible to infectious complications because they are immunocompromised, malnourished, and receiving cytotoxic cancer-related therapies. OBJECTIVE: Determine if cancer pain patients have a higher incidence of infectious complications following implantation of IDD or SCS systems than non-cancer pain patients. STUDY DESIGN: Retrospective chart review. SETTING: Single tertiary comprehensive cancer hospital. METHODS: Following local Institutional Review Board (IRB) approval, we collected data on infectious complications for IDD and SCS systems implanted at MD Anderson Cancer Center for the treatment of cancer and chronic pain. The examined implants were performed from July 15, 2006, to July 14, 2009. In addition, we obtained data regarding patient comorbidities and perioperative risk factors to assess their impact on infectious complications. RESULTS: One hundred forty-two devices were implanted in 131 patients during the examined period. Eighty-three of the devices were IDD systems and 59 were SCS systems. Eighty percent of the patients had a diagnosis of cancer. Four infectious complications were noted with an overall infectious risk of 2.8%. The infection rate was 2.4% for IDD systems versus 3.4% for SCS systems (P = 1). All infections were at the implantable pulse generator (IPG) or pump pocket site. The rate of infection was 2.7% for cancer patients and 3.3% for non-cancer patients (P = 1). Neither the perioperative administration of prophylactic antibiotics (P = 0.4) nor the National Nosocomial Infection Surveillance (NNIS) risk level for individual patients (P = 0.15) were statistically associated with infectious complication. The mean surgical time was longer for cases with infection at 215 ± 93 minutes versus 132 ± 52 minutes for those without infection which was statistically significant (P = 0.02). LIMITATIONS: The major limitation of this study is that it was a retrospective analysis. An additional limitation is that 51(38.9%) of our patients either died or were lost to follow-up during the year following implantation which may have led to an underestimation of our infection rates. CONCLUSIONS: The experience of this tertiary cancer pain center demonstrates that infectious complications following implantation of IDD and SCS systems are relatively rare events in cancer patients. Contrary to our initial hypothesis, no difference was found in the infection rate between cancer and non-cancer patients. The main factor associated with increased risk of infectious complications was increased surgical time, indicating a need to minimize patient time in the operating room. The low infectious complication rate seen in this series compared to previous reports in non-cancer patients is likely multifactorial in nature.

The effect of spinal cord stimulation (SCS) on static balance and gait.

OBJECTIVES: To investigate whether spinal cord stimulation (SCS) has a negative effect on static balance and gait, which is implicated by the increased incidence of falls leading to frequently occurring lead migrations. MATERIALS AND METHODS: A controlled trial is performed with 11 subjects (four female, seven male) with a mean age of 46 years old. A baseline measurement consisting of static balance and gait tests was performed. Within two weeks after implantation of a spinal cord stimulator, subjects performed the same tests with both stimulation switched on and off. Static balance was assessed with eyes open and eyes closed on hard surface and foam surface. The velocity of the center of pressure and weight symmetry were the main outcome parameters. Kinematics and spatiotemporal outcome parameters were used to analyze gait. ANOVAs were used to compare between baseline, stimulation on, and stimulation off. RESULTS: Spinal cord stimulation resulted in significant pain relief as scored on a Visual Analog Scale (p < 0.001). Gait width decreased and this change (indicative of improvement in balance) was significant (p = 0.007). No other significant group differences were found between stimulation baseline and post-surgery measurements. SCS did not influence static balance or gait when group effects were analyzed. Four subjects showed significant differences in static balance between stimulation on and off. CONCLUSIONS: The lack of group differences in normal gait and static balance cannot explain the increased incidence of falls. However, four subjects showed an effect of SCS on static balance. Further research to clarify why only a part of the subjects experienced balance problems is recommended and assessments of more demanding balance and gait tasks are desirable.