Improvement of sensory function after sequestrectomy for lumbar disc herniation: a prospective clinical study using quantitative sensory testing

Recommendations for terminology and the identification of neuropathic pain in people with spine-related leg pain. Outcomes from the NeuPSIG working group

ABSTRACT

Pain radiating from the spine into the leg is commonly referred to as "sciatica," "Sciatica" may include various conditions such as radicular pain or painful radiculopathy. It may be associated with significant consequences for the person living with the condition, imposing a reduced quality of life and substantial direct and indirect costs. The main challenges associated with a diagnosis of "sciatica" include those related to the inconsistent use of terminology for the diagnostic labels and the identification of neuropathic pain. These challenges hinder collective clinical and scientific understanding regarding these conditions. In this position paper, we describe the outcome of a working group commissioned by the Neuropathic Pain Special Interest Group (NeuPSIG) of the International Association for the Study of Pain (IASP) which was tasked with the following objectives: (1) to revise the use of terminology for classifying spine-related leg pain and (2) to propose a way forward on the identification of neuropathic pain in the context of spine-related leg pain. The panel recommended discouraging the term "sciatica" for use in clinical practice and research without further specification of what it entails. The term "spine-related leg pain" is proposed as an umbrella term to include the case definitions of somatic referred pain and radicular pain with and without radiculopathy. The panel proposed an adaptation of the neuropathic pain grading system in the context of spine-related leg pain to facilitate the identification of neuropathic pain and initiation of specific management in this patient population.

Evolution of somatosensory processing signs after nociceptive targeted surgery in patients with musculoskeletal disorders: a systematic review

ABSTRACT

Surgery is often advised when conservative treatment fails in musculoskeletal pain conditions, but a substantial proportion still suffers chronic pain after surgery. Somatosensory processing system (SPS) signs were previously studied as potential predictors for chronic postsurgical pain, but results are inconsistent. Therefore, studying the evolution of SPS signs could be of added value. The aim was to summarize all studies that measured how SPS signs evolved after nociceptive targeted surgery in musculoskeletal disorders and to find preoperative, perioperative, and postoperative predictors for the evolution of these SPS signs. Data were summarized, and risk of bias and level of evidence and recommendation were determined. Twenty-one studies were included. Five scored a low, 3 a moderate, and 13 a high risk of bias. In general, no consistent evolution of SPS signs comparing preoperative and postoperative values and predictors for this evolution in musculoskeletal disorders could be found. In most cases, static quantitative sensory testing (QST) did not change or conflicting results were found. On the other hand, dynamic QST mostly improved after surgery. Worthfully mentioning is that worsening of SPS signs was only seen at a follow-up of <3 months after surgery, that conclusions are stronger when evaluating dynamic QST with a follow-up of ≥3 months after surgery, and that pain improvement postsurgery was an important predictor. Future high-quality research should focus on the evolution of SPS signs after nociceptive targeted surgery, accounting for pain improvement groups and focusing on preoperative, perioperative, and postoperative predictors of this evolution.

Does preoperative opioid therapy in patients with a single lumbar disc herniation positively influence the postoperative outcome detected by quantitative sensory testing?

The importance of the type of pain medication in spinal disease is an ongoing matter of debate. Recent guidelines recommend acetaminophen and NSAIDs as first-line medication for lumbar disc herniation. However, opioid pain medication is commonly used in patients with chronic pain, and therefore also in patients with sciatica. The aim of this study is to evaluate if opioids have an impact on the outcome in patients suffering from lumbar disc herniation. To assess this objectively quantitative sensory testing (QST) was applied. In total, 52 patients with a single lumbar disc herniation confirmed on magnetic resonance imaging (MRI) and treated by lumbar sequesterectomy were included in the trial. Patients were analysed according to their preoperative opioid intake: 35 patients who did not receive opioids (group NO) and 17 patients, who received opioids preoperatively (group O). Further evaluation included detailed medical history, physical examination, various questionnaires, and QST. No pre- and postoperative differences were detected in thermal or mechanical thresholds (p > 0.05). Wind-up ratio (WUR) differed significantly between groups 1 week postoperatively (p = 0.025). The NRS for low back pain was rated significantly higher in the non-opioid group (NO) after 1-week follow-up (p = 0.026). Radicular pain tended to be higher in the NO group after 12 months of follow-up (p = 0.023). Opioids seem to be a positive predictor for the postoperative pain outcome in early follow-up in patients undergoing lumbar sequesterectomy. Furthermore, patients presented with less radicular pain 1 year after surgery.

Disentangling 'sciatica' to understand and characterise somatosensory profiles and potential pain mechanisms

OBJECTIVES

The study aimed to investigate if patients with lumbar radicular pain only and those with combined lumbar radicular pain + radiculopathy differ in their somatosensory profiles and pain experiences.

METHODS

Quantitative sensory testing (QST) was performed in 26 patients (mean age 47 ± 10 years, 10 females) with unilateral leg pain in the L5 or S1 distribution in their main pain area (MPA) and contralateral mirror side, in the relevant foot dermatome on the symptomatic side and in the hand dorsum. Pain experience was captured on the painDETECT.

RESULTS

Eight patients presented with lumbar radicular pain only and 18 patients with combined radicular pain + radiculopathy. Patients with radicular pain only demonstrated widespread loss of function (mechanical detection) bilaterally in the MPA (p<0.003) and hand (p=0.002), increased heat sensitivity in both legs (p<0.019) and cold/heat sensitivity in the hand (p<0.024). QST measurements in the dermatome did not differ compared to HCs and patients with radiculopathy. Patients with lumbar radiculopathy were characterised by a localised loss of function in the symptomatic leg in the MPA (warm, mechanical, vibration detection, mechanical pain threshold, mechanical pain sensitivity p<0.031) and dermatome (mechanical, vibration detection p<0.001), consistent with a nerve root lesion. Pain descriptors did not differ between the two groups with the exception of numbness (p<0.001). Patients with radicular pain did not report symptoms of numbness, while 78% of patients with radiculopathy did.

CONCLUSIONS

Distinct differences in somatosensory profiles and pain experiences were demonstrated for each patient group, suggesting differing underlying pain mechanisms.

[Entrapment neuropathies: a contemporary approach to pathophysiology, clinical assessment, and management : German version]

Entrapment neuropathies such as carpal tunnel syndrome, radiculopathies, or radicular pain are the most common peripheral neuropathies and also the most common cause for neuropathic pain. Despite their high prevalence, they often remain challenging to diagnose and manage in a clinical setting. Summarising the evidence from both preclinical and clinical studies, this review provides an update on the aetiology and pathophysiology of entrapment neuropathies. Potenzial mechanisms are put in perspective with clinical findings. The contemporary assessment is discussed and diagnostic pitfalls highlighted. The evidence for the noninvasive and surgical management of common entrapment neuropathies is summarised and future areas of research are identified.

A psychophysical study comparing massage to conditioned pain modulation: A single blind randomized controlled trial in healthy participants

INTRODUCTION

Pain-inducing massage results in greater pain inhibition than pain free massage, suggesting a mechanism dependent on conditioned pain modulation (CPM). The purpose of this study was to test the hypothesis that pain inducing massage produces similar magnitude of reduction in pain sensitivity as a cold pressor task and that baseline conditioned pain modulation efficiency predicts pain inducing massage related hypoalgesia.

METHODS

Sixty healthy participants were randomly assigned to receive either pain inducing massage to the neck, cold pressor task to the hand, or pain free massage to the neck. Participants also underwent pre and immediate post-intervention quantitative sensory testing. A repeated measures ANCOVA determined between group differences in pain sensitivity changes.

RESULTS

Pain inducing massage used as a conditioning stimulus resulted in comparable experimental pain sensitivity changes as a cold pressor task (p > 0.05). Pain intensity during the intervention demonstrated a weak correlation (r = 0.20, p = 0.12) with changes in pain sensitivity at a remote site. Individuals with an efficient CPM at baseline who received the pain inducing massage displayed greater increases in pressure pain threshold compared to individuals with a less efficient CPM indicating the potential benefit of treatment stratification by mechanism.

CONCLUSION

Although pain inducing massage resulted in less self-reported pain than a cold pressor task, both resulted in similar magnitude of the CPM response, suggesting shared underlying mechanisms. Understanding mechanisms of interventions can move us closer to mechanistic based treatments for pain which is consistent with a personalized medicine approach to care.

Electrical (Pain) Thresholds and Conditioned Pain Modulation in Patients with Low Back-Related Leg Pain and Patients with Failed Back Surgery Syndrome: A Cross-Sectional Pilot Study

OBJECTIVE

When evaluating sensory dysfunctions and pain mechanisms in patients with low back pain (LBP), a specific subgroup of patients with radicular symptoms is often excluded. Comparative studies that evaluate sensory sensitivity in patients with a dominant nociceptive and neuropathic pain component are rarely performed. Therefore, the goal of this study was to examine differences in electrical thresholds and conditioned pain modulation (CPM) between patients with low back-related leg pain (LBRLP) and patients with failed back surgery syndrome (FBSS).

DESIGN

Cross-sectional study.

SETTING

University Hospital Brussels.

SUBJECTS

Twenty-one patients with LBRLP and 21 patients with FBSS were included.

METHODS

Electrical detection thresholds (EDTs), electrical pain thresholds (EPTs), and CPM were evaluated on the symptomatic and nonsymptomatic sides. Within- and between-group differences were evaluated for all parameters.

RESULTS

No between-group differences were found for EDT and EPT at both sides. On the nonsymptomatic side, a significantly lower CPM effect was found in the FBSS group (P = 0.04). The only significant within-group difference was an increased EDT at the symptomatic side in patients with FBSS (P = 0.01).

CONCLUSIONS

LBP patients with a primary neuropathic pain component revealed altered detection sensitivity at the symptomatic side, without severe indications for altered nociceptive processing, compared with LBP patients without a dominant neuropathic pain component. Endogenous modulation is functioning in LBP patients, although it is possible that it might only be functioning partially in patients with a dominant neuropathic pain component.

Early surgery determines recovery of motor deficits in lumbar disc herniations-a prospective single-center study

Background

Patients with intervertebral disc herniation undergo surgical removal of herniated disc material in cases of persisting symptoms and/or neurologic deficits. While motor deficits often prompt surgery, little is known about the optimal timing of surgery in these cases. The aim of this study was to prospectively evaluate the impact of timing of disc surgery on motor recovery. Does postponing surgical treatment worsen outcome?

Method

In total, 120 patients with sciatica and/or sensorimotor deficits due to a lumbar disc herniation were surgically treated at the authors’ center within a 3-month period. In 60 patients, motor deficits were present at the time of admission. Motor function was assessed using manual muscle testing and subdivided according to the Medical Research Council (MRC) scale. Patient demographics, neurologic deficits, duration of motor deficits, treatment characteristics, and outcome were assessed. At a minimum follow-up of 1 year, functional recovery and complications were collated. Patients were subdivided into groups according to the severity of the paresis (MRC ≤ 3/5 vs. MRC 4/5). Intra-group differences were compared based on the duration of the neurologic deficits.

Results

Patients with moderate and severe paresis (MRC ≤ 3/5) benefit from treatment within 72 h as they were shown to have a significantly higher complete recovery rate at 1-year follow-up (75% vs. 0%; p < 0.001).

Conclusion

Immediate surgery should be offered to patients with moderate and severe motor deficits to increase the likelihood of neurologic recovery. This prospective data may have an impact on emergency triage in these patients.

Molecular and cellular correlates of human nerve regeneration: ADCYAP1/PACAP enhance nerve outgrowth

We only have a rudimentary understanding of the molecular and cellular determinants of nerve regeneration and neuropathic pain in humans. This cohort study uses the most common entrapment neuropathy (carpal tunnel syndrome) as a human model system to prospectively evaluate the cellular and molecular correlates of neural regeneration and its relationship with clinical recovery. In 60 patients undergoing carpal tunnel surgery [36 female, mean age 62.5 (standard deviation 12.2) years], we used quantitative sensory testing and nerve conduction studies to evaluate the function of large and small fibres before and 6 months after surgery. Clinical recovery was assessed with the global rating of change scale and Boston Carpal Tunnel Questionnaire. Twenty healthy participants provided normative data [14 female, mean age 58.0 (standard deviation 12.9) years]. At 6 months post-surgery, we noted significant recovery of median nerve neurophysiological parameters (P < 0.0001) and improvements in quantitative sensory testing measures of both small and large nerve fibre function (P < 0.002). Serial biopsies revealed a partial recovery of intraepidermal nerve fibre density [fibres/mm epidermis pre: 4.20 (2.83), post: 5.35 (3.34), P = 0.001], whose extent correlated with symptom improvement (r = 0.389, P = 0.001). In myelinated afferents, nodal length increased postoperatively [pre: 2.03 (0.82), post: 3.03 (1.23), P < 0.0001] suggesting that this is an adaptive phenomenon. Transcriptional profiling of the skin revealed 31 differentially expressed genes following decompression, with ADCYAP1 (encoding pituitary adenylate cyclase activating peptide, PACAP) being the most strongly upregulated (log2 fold-change 1.87, P = 0.0001) and its expression was associated with recovery of intraepidermal nerve fibres. We found that human induced pluripotent stem cell-derived sensory neurons expressed the receptor for PACAP and that this peptide could significantly enhance axon outgrowth in a dose-dependent manner in vitro [neurite length PACAP 1065.0 µm (285.5), vehicle 570.9 μm (181.8), P = 0.003]. In conclusion, carpal tunnel release is associated with significant cutaneous reinnervation, which correlates with the degree of functional improvement and is associated with a transcriptional programme relating to morphogenesis and inflammatory processes. The most highly dysregulated gene ADCYAP1 (encoding PACAP) was associated with reinnervation and, given that this peptide signals through G-protein coupled receptors, this signalling pathway provides an interesting therapeutic target for human sensory nerve regeneration.

Entrapment neuropathies: a contemporary approach to pathophysiology, clinical assessment, and management

Entrapment neuropathies such as carpal tunnel syndrome, radiculopathies, or radicular pain are the most common peripheral neuropathies and also the most common cause for neuropathic pain. Despite their high prevalence, they often remain challenging to diagnose and manage in a clinical setting. Summarising the evidence from both preclinical and clinical studies, this review provides an update on the aetiology and pathophysiology of entrapment neuropathies. Potential mechanisms are put in perspective with clinical findings. The contemporary assessment is discussed and diagnostic pitfalls highlighted. The evidence for the noninvasive and surgical management of common entrapment neuropathies is summarised and future areas of research are identified.

Association of quantitative sensory testing parameters with clinical outcome in patients with lumbar radiculopathy undergoing microdiscectomy

Background/Aim

This study aimed to establish the somatosensory profile of patients with lumbar radiculopathy at pre‐and post‐microdiscectomy and to explore any association between pre‐surgical quantitative sensory test (QST) parameters and post‐surgical clinical outcomes.

Methods

A standardized QST protocol was performed in 53 patients (mean age 38 ± 11 years, 26 females) with unilateral L5/S1 radiculopathy in the main pain area (MPA), affected dermatome and contralateral mirror sites and in age‐ and gender‐,and body site‐matched healthy controls. Repeat measures at 3 months included QST, the Oswestry Disability Index (ODI) and numerous other clinical measures; at 12 months, only clinical measures were repeated. A change <30% on the ODI was defined as ‘no clinically meaningful improvement’.

Results

Patients showed a significant loss of function in their symptomatic leg both in the dermatome (thermal, mechanical, vibration detection p < .002), and MPA (thermal, mechanical, vibration detection, mechanical pain threshold, mechanical pain sensitivity p < .041) and increased cold sensitivity in the MPA (p < .001). Pre‐surgical altered QST parameters improved significantly post‐surgery in the dermatome (p < .018) in the symptomatic leg and in the MPA (p < .010), except for thermal detection thresholds and cold sensitivity. Clinical outcomes improved at 3 and 12 months (p < .001). Seven patients demonstrated <30% change on the ODI at 12 months. Baseline loss of function in mechanical detection in the MPA was associated with <30% change on the ODI at 12 months (OR 2.63, 95% CI 1.09–6.37, p = .032).

Conclusion

Microdiscectomy resulted in improvements in affected somatosensory parameters and clinical outcomes. Pre‐surgical mechanical detection thresholds may be predictive of clinical outcome.

Significance

This study documented quantitative sensory testing (QST) profiles in patients with lumbar radiculopathy in their main pain area (MPA) and dermatome pre‐ and post‐microdiscectomy and explored associations between QST parameters and clinical outcome. Lumbar radiculopathy was associated with loss of function in modalities mediated by large and small sensory fibres. Microdiscectomy resulted in significant improvements in loss of function and clinical outcomes in 85% of our cohort. Pre‐surgical mechanical detection thresholds in the MPA may be predictive of clinical outcome.

Concurrent validity of a low-cost and time-efficient clinical sensory test battery to evaluate somatosensory dysfunction

Background

This study describes a low‐cost and time‐efficient clinical sensory test (CST) battery and evaluates its concurrent validity as a screening tool to detect somatosensory dysfunction as determined using quantitative sensory testing (QST).

Method

Three patient cohorts with carpal tunnel syndrome (CTS, n = 76), non‐specific neck and arm pain (NSNAP, n = 40) and lumbar radicular pain/radiculopathy (LR, n = 26) were included. The CST consisted of 13 tests, each corresponding to a QST parameter and evaluating a broad spectrum of sensory functions using thermal (coins, ice cube, hot test tube) and mechanical (cotton wool, von Frey hairs, tuning fork, toothpicks, thumb and eraser pressure) detection and pain thresholds testing both loss and gain of function. Agreement rate, statistical significance and strength of correlation (phi coefficient) between CST and QST parameters were calculated.

Results

Several CST parameters (cold, warm and mechanical detection thresholds as well as cold and pressure pain thresholds) were significantly correlated with QST, with a majority demonstrating >60% agreement rates and moderate to relatively strong correlations. However, agreement varied among cohorts. Gain of function parameters showed stronger agreement in the CTS and LR cohorts, whereas loss of function parameters had better agreement in the NSNAP cohort. Other CST parameters (16 mN von Frey tests, vibration detection, heat and mechanical pain thresholds, wind‐up ratio) did not significantly correlate with QST.

Conclusion

Some of the tests in the CST could help detect somatosensory dysfunction as determined with QST. Parts of the CST could therefore be used as a low‐cost screening tool in a clinical setting.

Significance

Quantitative sensory testing, albeit considered the gold standard to evaluate somatosensory dysfunction, requires expensive equipment, specialized examiner training and substantial time commitment which challenges its use in a clinical setting. Our study describes a CST as a low‐cost and time‐efficient alternative. Some of the CST tools (cold, warm, mechanical detection thresholds; pressure pain thresholds) significantly correlated with the respective QST parameters, suggesting that they may be useful in a clinical setting to detect sensory dysfunction.

Perioperative Pain Assessment in a 14-Year-Old Boy with Lumbar Disc Herniation

This case report illustrates the value of a comprehensive perioperative pain assessment composed of quantitative sensory testing and self-reported measures that highlight the impact of pain experienced by a 14-year-old boy suffering from chronic low back pain and sciatica. Before surgery, the pain assessment revealed inefficient endogenous inhibitory pain control with presence of temporal summation of pain. The severe pain was constant and lasted for 18 months. The patient was in a high-anxiety state, and reported significant functional disability and poor sleep quality. Six months after surgery, the patient was pain free. Quantitative sensory testing showed an improvement in his inhibitory pain control with the absence of temporal summation of pain. The patient was no longer anxious, was back to normal functional abilities, and reported good sleep quality. By including neurophysiology and other pain measures, the clinical application of a comprehensive pain assessment can provide objective measurements of treatment efficacy.