Restorative neurostimulation for chronic low back pain indications [Neurosurgery Wiki]

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====== Restorative neurostimulation for chronic low back pain indications ======

//[[J.Sales-Llopis]]//

//Neurosurgery Department, [[General University Hospital Alicante]], [[Spain]]//
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Restorative neurostimulation for chronic low back pain is a treatment modality aimed at improving function and reducing pain by targeting the underlying pathophysiology of the condition. Below are the indications commonly considered for this treatment approach:

===== Primary Indications =====

1. **Chronic Low Back Pain of Neuropathic Origin**
   - Pain persists for more than 6 months, resistant to conservative treatments (physical therapy, medications, and injections).
   - Often associated with nerve dysfunction or sensitization.

2. **Failed Back Surgery Syndrome (FBSS)**
   - Persistent or recurrent low back pain after spinal surgery.
   - No anatomical cause justifying revision surgery.

3. **Mechanical Low Back Pain**
   - Pain due to dysfunction in the intervertebral discs, facet joints, or sacroiliac joints without significant structural deformity requiring surgical correction.

4. **Myofascial Pain Syndrome**
   - Chronic muscular pain that has not responded to other treatments.
   - Often associated with muscle spasm and trigger points.

### **Patient Selection Criteria**
1. **Refractory to Conventional Treatments**
   - Pain persists despite conservative interventions like physical therapy, pain medications, epidural steroid injections, or radiofrequency ablation.

2. **No Significant Anatomical Pathology Requiring Surgery**
   - Imaging excludes conditions such as spinal stenosis, significant disc herniation, or instability that might benefit from surgical intervention.

3. **Functional Disability**
   - Impaired quality of life and activities of daily living due to chronic pain.

4. **Psychological Suitability**
   - Absence of major untreated psychiatric disorders (e.g., severe depression, substance abuse) that could affect treatment adherence or outcomes.

5. **Ability to Participate in Rehabilitation**
   - Willingness and capacity to engage in a rehabilitation program alongside neurostimulation therapy to optimize outcomes.

### **Specific Conditions for Consideration**
- **Multifidus Muscle Dysfunction**:
   - Evidence of muscle atrophy or poor control of spinal stability muscles often seen in chronic low back pain cases.
   - Restorative neurostimulation targets reactivation of these muscles.

- **Neuropathic Pain Components**:
   - Evidence of nerve-related pain, such as burning, tingling, or shooting sensations, may be particularly responsive to neurostimulation.

### **Contraindications**
- Severe spinal deformities or structural pathologies that require surgical correction.
- Active systemic infection or localized infection at the implantation site.
- Pacemakers or other implanted devices incompatible with neurostimulation.
- Cognitive impairment limiting the ability to operate the device.

### **Clinical Goals**
- Restore muscle function, especially in the lumbar multifidus.
- Reduce reliance on opioid or other pharmacological pain management strategies.
- Improve quality of life and physical function. 

Let me know if you need further clarification or a literature review on the topic!

===== Randomized controlled trials =====

A study hypothesized that restorative neurostimulation, a rehabilitative treatment that activates the lumbar multifidus muscles to overcome underlying dysfunction, is safe and provides relevant and durable clinical benefits to patients with this specific etiology.

In this prospective five-year longitudinal follow-up of the ReActiv8-B pivotal trial, participants (N = 204) had activity-limiting, moderate-to-severe, refractory, mechanical chronic low back pain, a positive prone instability test result indicating impaired multifidus muscle control, and no indications for spine surgery. Low back pain intensity (10-cm visual analog scale [VAS]), disability (Oswestry Disability Index), and quality of life (EuroQol's "EQ-5D-5L" index) were compared with baseline and following the intent-to-treat principle, with a supporting mixed-effects model for repeated measures that accounted for missing data.

At five years (n = 126), low back pain VAS had improved from 7.3 to 2.4 cm (-4.9; 95% CI, -5.3 to -4.5 cm; p < 0.0001), and 71.8% of participants had a reduction of ≥50%. The Oswestry Disability Index improved from 39.1 to 16.5 (-22.7; 95% CI, -25.4 to -20.8; p < 0.0001), and 61.1% of participants had a reduction of ≥20 points. The EQ-5D-5L index improved from 0.585 to 0.807 (0.231; 95% CI, 0.195-0.267; p < 0.0001). Although the mixed-effects model attenuated completed-case results, conclusions and statistical significance were maintained. Of 52 subjects who were on opioids at baseline and had a five-year visit, 46% discontinued, and 23% decreased intake. The safety profile compared favorably with neurostimulator treatments for other types of back pain. No lead migrations were observed.

Over five years, restorative neurostimulation provided clinically substantial and durable benefits with a favorable safety profile in patients with refractory chronic low back pain associated with multifidus muscle dysfunction.

Clinical trial registration: The Clinicaltrials.gov registration number for the study is NCT02577354; registration date: October 15, 2016; principal investigator: Christopher Gilligan, MD, Brigham and Women's Hospital, Boston, MA, USA. The study was conducted in Australia (Broadmeadow, New South Wales; Noosa Heads, Queensland; Welland, South Australia; Clayton, Victoria), Belgium (Sint-Niklaas; Wilrijk), The Netherlands (Rotterdam), UK (Leeds, London, Middlesbrough), and USA (La Jolla, CA; Santa Monica, CA; Aurora, CO; Carmel, IN; Indianapolis, IN; Kansas City, KS; Boston, MA; Royal Oak, MI; Durham, NC; Winston-Salem, NC; Cleveland, OH; Providence, RI; Spartanburg, SC; Spokane, WA; Charleston, WV)
((Gilligan C, Volschenk W, Russo M, Green M, Gilmore C, Mehta V, Deckers K, De Smedt K, Latif U, Sayed D, Georgius P, Gentile J, Mitchell B, Langhorst M, Huygen F, Baranidharan G, Patel V, Mironer E, Ross E, Carayannopoulos A, Hayek S, Gulve A, Van Buyten JP, Tohmeh A, Fischgrund J, Lad S, Ahadian F, Deer T, Klemme W, Rauck R, Rathmell J, Maislin G, Heemels JP, Eldabe S. Five-Year Longitudinal Follow-Up of Restorative Neurostimulation Shows Durability of Effectiveness in Patients With Refractory Chronic Low Back Pain Associated With Multifidus Muscle Dysfunction. Neuromodulation. 2024 Jul;27(5):930-943. doi: 10.1016/j.neurom.2024.01.006. Epub 2024 Mar 12. PMID: 38483366.))

===== Retrospective case series =====

Previous studies have excluded patients with prior [[lumbar spine surgery]]. 

Whittle et al. describe outcomes in patients with CLBP after prior lumbar surgery.

This was a single-[[center]], consecutive [[case series]]. The [[primary outcome]] measure was the change from [[baseline]] numeric rating score (NRS) for [[low back pain]] (LBP) and [[Oswestry Disability Index]] (ODI) in the first 12 months after treatment. [[Secondary outcome]]s were several patients having minimal clinically important difference (MCID) in NRS and ODI scores, Short Assessment of Patient [[Satisfaction]] with their management, relationships between type of prior surgery and outcome, and incidence of adverse events.

The cohort comprised 26 patients (12 men; 14 women; mean age 56 years) who had their lumbar surgery a mean of 6.9 years previously; 16 were followed up for 12 months and nine for >six months. One patient (3.6%) had a postoperative infection and required device removal. Both mean ODI and LBP NRS and their 95% CIs decreased serially from baseline 41.8 (36.5-46.5) to 29.3 (22.1-36.6) at six months and 28.1 (21.8-34.4) at 12 months (ODI), and from 6.4 (5.5-7.0), 3.8 (3.1-4.6) and 3.6 (2.5-4.7), respectively, for NRS. Patient levels of satisfaction with treatment were very high. MCIDs were observed in ten patients (40%) who experienced improvement in both their ODI (by >10) and NRS (by >2), and in ten patients who experienced improvement in one of these variables but not the other. The type of prior lumbar surgery did not influence outcomes. There were no device-related complications.

The early outcome profiles after [[restorative neurostimulation]] after [[lumbar spinal surgery]] are similar to those reported in patients without prior surgery. Further prospective clinical studies are required to establish the validity of these findings
((Whittle IR, Yull D, Huang A, Fish S, Chene D, Selby M, Craig K, Clausen E, Yau YH. Restorative Neurostimulation of the Multifidus for Chronic Low Back Pain After Prior Lumbar Spinal Surgery: A Single-Center, Consecutive Case Series. Neuromodulation. 2024 Dec 10:S1094-7159(24)01219-4. doi: 10.1016/j.neurom.2024.10.011. Epub ahead of print. PMID: 39665721.)).
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==== Critical Review ====

**Study Design and Objectives**  
Whittle et al. conducted a single-center, consecutive case series evaluating the outcomes of patients with CLBP who underwent restorative neurostimulation following prior lumbar surgery. The study aimed to assess changes in numeric rating score (NRS) for low back pain (LBP) and Oswestry Disability Index (ODI) over 12 months, as well as secondary outcomes such as patient satisfaction, achievement of minimal clinically important differences (MCIDs), and adverse events. While the design provides valuable insights, the single-center nature and small cohort limit the generalizability and robustness of the findings.

**Strengths of the Study**  

1. **Specific Focus on CLBP Post-Surgery:**  
   The study addresses an important subset of patients—those with persistent pain after lumbar surgery—where effective interventions are often limited. This targeted approach fills a gap in the existing literature.

2. **Multifaceted Outcomes:**  
   The inclusion of both primary (ODI, NRS) and secondary outcomes (MCID achievement, patient satisfaction, and adverse events) allows for a comprehensive evaluation of the intervention.

3. **[[Longitudinal]] Data Collection:**  
   The follow-up period of 12 months enables observation of sustained effects, which is critical in CLBP management.

4. **Patient Satisfaction:**  
   High satisfaction levels reflect positive subjective experiences, an essential aspect often overlooked in surgical outcome studies.

5. **No Device-Related Complications:**  
   The absence of device-related complications is encouraging and suggests safety in this cohort.

**Limitations of the Study**

1. **Small [[Sample Size]]:**  
   The cohort of 26 patients, with only 16 completing 12 months of follow-up, significantly limits statistical power and increases the risk of type II errors. The findings should be interpreted with caution given the potential for overrepresentation of positive outcomes.

2. **Single-Center Design:**  
   The lack of multi-center data reduces the external validity of the results. Variability in surgical techniques, postoperative care, and patient demographics across centers could influence outcomes.

3. **Lack of [[Control Group]]:**  
   Without a control group, it is difficult to ascertain the specific efficacy of restorative neurostimulation compared to other interventions or natural history. A randomized controlled trial (RCT) design would provide stronger evidence.

4. **Potential [[Bias]] in Case Selection:**  
   The consecutive case series design, while useful for capturing real-world data, may introduce selection bias. It is unclear if the cohort represents the broader population of CLBP patients post-lumbar surgery.

5. **Incomplete [[Follow-Up]]:**  
   The incomplete follow-up of 9 patients (approximately 35%) reduces the [[robust]]ness of longitudinal data and raises concerns about potential attrition bias.

6. **Limited Exploration of Subgroup Differences:**  
   Although the study reports no influence of prior lumbar surgery type on outcomes, the small sample size limits the power to detect meaningful differences. Stratified analyses with larger cohorts could provide more insight.

7. **MCID Achievements Not Universally Positive:**  
   Only 40% of patients achieved MCID in both ODI and NRS, and another 40% improved in one but not the other. This suggests a heterogeneous response to the intervention, necessitating further investigation into predictive factors for success.

**Interpretation of Results**

The results indicate that restorative neurostimulation can lead to significant improvements in ODI and NRS scores, with a trend toward sustained benefits at 12 months. The reported decreases in ODI (from 41.8 to 28.1) and NRS (from 6.4 to 3.6) represent clinically meaningful improvements. However, the relatively modest proportion of patients achieving MCIDs suggests variability in effectiveness, warranting further research.

Patient satisfaction and safety outcomes are notable positives. However, these findings should be tempered by the study's limitations, particularly the small sample size and lack of a control group. The absence of device-related complications is promising, but longer-term follow-up is necessary to confirm safety and durability.

**Conclusion and Recommendations**

The study by Whittle et al. provides early evidence that restorative neurostimulation may benefit patients with CLBP after lumbar surgery, with outcomes comparable to those without prior surgery. However, the limitations highlight the need for more rigorous research:

1. Conducting multicenter RCTs with larger, more diverse populations.
2. Exploring predictors of response to identify patient subgroups most likely to benefit.
3. Including longer follow-up periods to assess sustained efficacy and safety.

While the results are encouraging, they should be interpreted as preliminary, underscoring the importance of further validation through well-designed prospective studies.