A preliminary comparison of myoelectric and cyclic control of an implanted neuroprosthesis to modulate gait speed in incomplete SCI

OBJECTIVE

Explore whether electromyography (EMG) control of electrical stimulation for walking after incomplete spinal cord injury (SCI) can affect ability to modulate speed and alter gait spatial-temporal parameters compared to cyclic repetition of pre-programmed stimulation.

DESIGN

Single case study with subject acting as own concurrent control. Setting Hospital-based biomechanics laboratory.

PARTICIPANTS

Single subject with C6 AIS D SCI using an implanted neuroprosthesis for walking. Interventions Lower extremity muscle activation via an implanted system with two different control methods: (1) pre-programmed pattern of stimulation, and (2) EMG-controlled stimulation based on signals from the gastrocnemius and quadriceps.

OUTCOME MEASURES

Gait speed, distance, and subjective rating of difficulty during 2-minute walks. Range of walking speeds and associated cadences, stride lengths, stride times, and double support times during quantitative gait analysis.

RESULTS

EMG control resulted in statistically significant increases in both walking speed and distance (P < 0.001) over cyclic stimulation during 2-minute walks. Maximum walking speed with EMG control (0.48 m/second) was significantly (P < 0.001) faster than the fastest automatic pattern (0.39 m/second), with increased cadence and decreased stride and double support times (P < 0.000) but no change in stride length (z = -0.085; P = 0.932). The slowest walking with EMG control (0.25 m/second) was virtually indistinguishable from the slowest with automatic cycling (z = -0.239; P = 0.811).

CONCLUSION

EMG control can increase the ability to modulate comfortable walking speed over pre-programmed cyclic stimulation. While control methods did not differ at the lowest speed, EMG-triggered stimulation allowed significantly faster walking than cyclic stimulation. The expanded range of available walking speeds could permit users to better avoid obstacles and naturally adapt to various environments. Further research is required to definitively determine the robustness, generalizability, and functional implications of these results.

Effects of movement and postural positions in spinal cord stimulation in the new rechargeable systems

BACKGROUND

Despite recent developments in implantable neurostimulation devices, the adjustment of stimulation levels to the patient's postural changes has remained a problem so far.

OBJECTIVE

This study was conducted with the newest rechargeable devices, in order to compare its results with the ones published from conventional systems.

STUDY DESIGN

It is a prospective study.

SETTING

In 46 patients implanted with rechargeable constant current stimulation systems we measured impedance, stimulation thresholds, therapeutic range, as well patients' satisfaction and sensation in 7 different body postures.

RESULTS

Data analysis was performed in 46 patients, whose most frequent pathologies were failed back surgery syndrome (FBSS) and complex regional pain syndrome (CRPS). The lowest amplitude needed to reach the different thresholds was always scored in the supine decubitus position, with no significant changes in the therapeutic range and impedance. For all stimulation thresholds, there is always a difference between the supine position and all other postures. No statistically significant differences with regard to patients' satisfaction and sensation were found for the different postures.

LIMITATIONS

Sample sample size.

CONCLUSION

The findings of the present work are similar to those described in previous publications that showed the relationship between postural changes and several stimulation thresholds and pulse energy. The posture which requires lower energy - and whose corresponding therapeutic range (TR) is narrower--is supine decubitus.

Case series on variable presentation of ligamentum flavum stimulation following percutaneous cylindrical spinal cord stimulator lead implants

BACKGROUND

Stimulation-evoked discomfort secondary to ligamentum flavum stimulation (LFS) is a technological limitation of percutaneous spinal cord stimulator (SCS) lead implants. There is a paucity of literature describing the clinical presentation and time periods at which this side effect may present following insertion of cylindrical lead(s).

OBJECTIVE

To describe a series of 5 patients who presented at varying time periods after SCS lead placement with LFS.

STUDY DESIGN

Retrospective case series.

METHODS

We performed a chart review of online medical records of patients with symptoms consistent with LFS at an academic interventional pain clinic identified over 7 consecutive years (2006 - 2013).

RESULTS

LFS most frequently presented within months of implantation of cylindrical leads. One patient complained of LFS during the temporary trial while another developed LFS after lead revision. All patients were successfully treated when paddle electrodes replaced percutaneous cylindrical leads.

CONCLUSION

LFS may present as a barrier to successful SCS treatment. Clinicians placing percutaneous SCS leads should be aware of the variable time course of LFS presentation. Paddle style electrodes seem to offer an enduring solution to LFS so that patients may continue to benefit from SCS therapy.

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

BACKGROUND

Spinal cord stimulation (SCS) is an accepted treatment in patients with failed back surgery (FBS), complex regional pain syndrome (CRPS) and persistent radicular pain following surgery. In order to avoid patient hazards or device malfunction manufacturers advise to abstain from magnetic resonance imaging (MRI) in patients with implanted electrodes or pulse generators.

METHODS

In a prospective study, 13 patients harbouring an implanted Medtronic Spinal Cord Stimulation (SCS) device underwent MRI (1.5 T) of the lumbar (n=13), the cervical (n=2) or the thoracic spine (n=1) following the development of new spinal symptoms. An adapted MRI protocol was used limiting the transmitted energy and specific absorption rate. Tolerability and safety were assessed by means of a standardized patient evaluation form documenting pain on a visual analogue scale (0-10), neurologic deficit, and discomfort during the scan. In addition, overall satisfaction with the examination procedure was rated on a Likert scale (1-5). Image quality was rated independently and blinded to the presence of a SCS device by the radiologist and the surgeon as equivalent, superior or inferior compared to the standard spine MRI examination.

RESULTS

None of the 13 patients investigated by the modified spinal MRI protocol experienced new neurological deficits, worsening of symptoms or a defect/malfunction of the implant device. Three patients (23.1 %) reported transient warm sensation in the location of the electrode and in one case intermittent slight tingling in the lower extremities. Overall satisfaction with the examination was 1.13 ± 0.34 according to Likert scale (1-5). The image quality was rated - not statistically significant - slightly inferior to standard lumbar spine imaging (0.82 ± 0.54) with a kappa value of 0.68 between the two investigators. MRI examinations detected relevant and new lesions in 9 (69.2 %) patients which affected treatment in 8 (61.5 %) individuals.

CONCLUSION

Using a protocol with a reduced specific energy absorption rate, spinal MRI examinations in patients with SCS can be considered safe. The current view that neurostimulators are a general contraindication to MR examinations has to be reconsidered in patients with new or progressive spinal symptoms.

Spinal cord stimulation for predominant low back pain in failed back surgery syndrome: study protocol for an international multicenter randomized controlled trial (PROMISE study)

BACKGROUND

Although results of case series support the use of spinal cord stimulation in failed back surgery syndrome patients with predominant low back pain, no confirmatory randomized controlled trial has been undertaken in this patient group to date. PROMISE is a multicenter, prospective, randomized, open-label, parallel-group study designed to compare the clinical effectiveness of spinal cord stimulation plus optimal medical management with optimal medical management alone in patients with failed back surgery syndrome and predominant low back pain.

METHOD/DESIGN

Patients will be recruited in approximately 30 centers across Canada, Europe, and the United States. Eligible patients with low back pain exceeding leg pain and an average Numeric Pain Rating Scale score ≥5 for low back pain will be randomized 1:1 to spinal cord stimulation plus optimal medical management or to optimal medical management alone. The investigators will tailor individual optimal medical management treatment plans to their patients. Excluded from study treatments are intrathecal drug delivery, peripheral nerve stimulation, back surgery related to the original back pain complaint, and experimental therapies. Patients randomized to the spinal cord stimulation group will undergo trial stimulation, and if they achieve adequate low back pain relief a neurostimulation system using the Specify® 5-6-5 multi-column lead (Medtronic Inc., Minneapolis, MN, USA) will be implanted to capture low back pain preferentially in these patients. Outcome assessment will occur at baseline (pre-randomization) and at 1, 3, 6, 9, 12, 18, and 24 months post randomization. After the 6-month visit, patients can change treatment to that received by the other randomized group. The primary outcome is the proportion of patients with ≥50% reduction in low back pain at the 6-month visit. Additional outcomes include changes in low back and leg pain, functional disability, health-related quality of life, return to work, healthcare utilization including medication usage, and patient satisfaction. Data on adverse events will be collected. The primary analysis will follow the intention-to-treat principle. Healthcare use data will be used to assess costs and long-term cost-effectiveness.

DISCUSSION

Recruitment began in January 2013 and will continue until 2016.

TRIAL REGISTRATION

Clinicaltrials.gov: NCT01697358 (http://www.clinicaltrials.gov).

Importance of axial migration of spinal cord stimulation trial leads with position

BACKGROUND

Spinal cord stimulation (SCS) is an established treatment option for chronic pain. Prior to permanent implantation, temporary trials are performed to evaluate the SCS treatment. During the trial period, it is common for the patients to experience changes in paresthesias. However, it is unclear what the role of lead migration is, if any, in the changes in paresthesia.

OBJECTIVE

To evaluate the role of lead migration on the effect of postural stimulation changes during SCS trials.

STUDY DESIGN

Case series.

SETTING

University pain management center.

METHODS

X-rays of the patients with successful trials, in sitting and standing position, were obtained at the end of a 7 day SCS trial. Data were collected based on the need for adjustment of the stimulation settings due to changes in paresthesias with postural change of sitting versus standing.

RESULTS

The average lead migration was 3.05 mm inferiorly from a standing to sitting position for all subjects. The average migration was 2.85 mm in subjects requiring adjustment of the SCS setting due to change in paresthesia compared to 3.24 mm for those who did not require adjustment regardless of position. The results were insignificant based on P = 0.17.

LIMITATIONS

Small sample size, case series.

CONCLUSIONS

This case series demonstrates continued support for the role of the width of the cerebral spinal fluid space as the significant factor on paresthesia changes in SCS with respect to postural changes, even during the trial period.

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.

Spinal cord stimulation for non-reconstructable chronic critical leg ischaemia

BACKGROUND

Patients suffering from inoperable chronic critical leg ischaemia (NR-CCLI) face amputation of the leg. Spinal cord stimulation (SCS) has been proposed as a helpful treatment in addition to standard conservative treatment.

OBJECTIVES

To find evidence for an improvement on limb salvage, pain relief, and the clinical situation using SCS compared to conservative treatment alone.

SEARCH METHODS

For this update the Cochrane Peripheral Vascular Diseases Group Trials Search Co-ordinator searched the Specialised Register (last searched January 2013) and CENTRAL (2012, Issue 12).

SELECTION CRITERIA

Controlled studies comparing the addition of SCS with any form of conservative treatment to conservative treatment alone in patients with NR-CCLI.

DATA COLLECTION AND ANALYSIS

Both authors independently assessed the quality of the studies and extracted data.

MAIN RESULTS

Six studies comprising nearly 450 patients were included. In general the quality of the studies was good. No study was blinded due to the type of intervention.Limb salvage after 12 months was significantly higher in the SCS group (risk ratio (RR) 0.71, 95% confidence interval (CI) 0.56 to 0.90; risk difference (RD) -0.11, 95% CI -0.20 to -0.02). Significant pain relief occurred in both treatment groups, but was more prominent in the SCS group where the patients required significantly less analgesics. In the SCS group, significantly more patients reached Fontaine stage II than in the conservative group (RR 4.9, 95% CI 2.0 to 11.9; RD 0.33, 95% CI 0.19 to 0.47). Overall, no significantly different effect on ulcer healing was observed with the two treatments.Complications of SCS treatment consisted of implantation problems (9%, 95% CI 4 to 15%) and changes in stimulation requiring re-intervention (15%, 95% CI 10 to 20%). Infections of the lead or pulse generator pocket occurred less frequently (3%, 95% CI 0 to 6%). Overall risk of complications with additional SCS treatment was 17% (95% CI 12 to 22%), indicating a number needed to harm of 6 (95% CI 5 to 8).Average overall costs (one study) at two years were EUR 36,500 (SCS group) and EUR 28,600 (conservative group). The difference (EUR 7900) was significant (P < 0.009).

AUTHORS' CONCLUSIONS

There is evidence to favour SCS over standard conservative treatment alone to improve limb salvage and clinical situations in patients with NR-CCLI. The benefits of SCS must be considered against the possible harm of relatively mild complications and the costs.

The effectiveness and cost-effectiveness of spinal cord stimulation for refractory angina (RASCAL study): study protocol for a pilot randomized controlled trial

BACKGROUND

The RASCAL (Refractory Angina Spinal Cord stimulation and usuAL care) pilot study seeks to assess the feasibility of a definitive trial to assess if addition of spinal cord stimulation (SCS) to usual care is clinically superior and more cost-effective than usual care alone in patients with refractory angina.

METHODS/DESIGN

This is an external pilot, patient-randomized controlled trial.The study will take place at three centers in the United Kingdom - South Tees Hospitals NHS Foundation Trust (The James Cook University Hospital), Dudley Group of Hospitals NHS Foundation Trust, and Basildon and Thurrock University Hospitals NHS Foundation Trust.The subjects will be 45 adults with refractory angina, that is, limiting angina despite optimal anti-angina therapy, Canadian Cardiovascular Society Functional Classification Class III and IV, angiographically documented coronary artery disease not suitable for revascularization, satisfactory multidisciplinary assessment and demonstrable ischemia on functional testing.The study will be stratified by center, age and Canadian Cardiovascular Society Functional Classification.Interventions will involve spinal cord stimulation plus usual care ('SCS group') or usual care alone ('UC group'). Usual care received by both groups will include consideration of an education session with a pain consultant, trial of a transcutaneous electrical neurostimulation, serial thoracic sympathectomy and oral/systemic analgesics.Expected outcomes will be recruitment and retention rates; reasons for agreeing/declining participation; variability in primary and secondary outcomes (to inform power calculations for a definitive trial); and completion rates of outcome measures. Trial patient-related outcomes include disease-specific and generic health-related quality of life, angina exercise capacity, intake of angina medications, frequency of angina attacks, complications and adverse events, and satisfaction.

DISCUSSION

The RASCAL pilot trial seeks to determine the feasibility and design of a definitive randomized controlled trial comparing the addition of spinal cord stimulation to usual care versus usual care alone for patients with refractory angina.Fifteen patients have been recruited since recruitment opened in October 2011. The trial was originally scheduled to end in April 2013 but due to slow recruitment may have to be extended to late 2013.

TRIAL REGISTRATION

ISRCTN65254102.

[Failed back surgery, spinal cord stimulation and pregnancy: presentation of a case]

Spinal cord stimulation is increasingly used to manage chronic pain syndromes, such as complex regional pain syndrome, chronic back pain, refractory angina pectoris or peripheral vascular diseases, which are unresponsive to other common less aggressive treatment methods. The early use of this technique in the aforementioned diseases makes it suitable in young women of childbearing age and who wish to become pregnant. We report the case of a 33-year-old woman who became pregnant 4 months after having undergone posterior cord stimulation, and we review the approach to this situation and the perioperative management during the perinatal period.