Median nerve small- and large-fiber damage in carpal tunnel syndrome: a quantitative sensory testing study

Concordance between the Stockholm Workshop Scale and the International Consensus Criteria for grading the severity of neurosensory manifestations in hand-arm vibration syndrome in a Swedish clinical setting

OBJECTIVES

Occupational exposure to vibration using hand-held tools may cause hand-arm vibration syndrome (HAVS). Correct diagnosis and grading of severity are crucial in protecting the individual's health and for workers' compensation claims. The International Consensus Criteria (ICC) has been suggested to replace the widely used Stockholm Workshop Scale (SWS). The aims were to, in a clinical setting, assess the concordance between the SWS and the ICC neurosensory severity grading of vibration injury, and to present the clinical picture according to symptoms, type of affected nerve fibres and the relation between vascular and neurosensory manifestations.

METHODS

Data were collected from questionnaires, clinical examination and exposure assessment of 92 patients with HAVS. The severity of neurosensory manifestations was classified according to both scales. The prevalence of symptoms and findings was compared across groups of patients with increasing severity according to the SWS.

RESULTS

Classification with the ICC resulted in a shift towards lower grades of severity than with the SWS due to a systematic difference between the scales. Affected sensory units with small nerve fibres were far more prevalent than affected units with large nerve fibres. The most prevalent symptoms were numbness (91%) and cold intolerance (86%).

CONCLUSIONS

Using the ICC resulted in lower grades of the severity of HAVS. This should be taken into consideration when giving medical advice and approving workers' compensation. Clinical examinations should be performed to detect affected sensory units with both small and large nerve fibres and more attention should be paid to cold intolerance.

Which Psychological and Electrodiagnostic Factors Are Associated With Limb Disability in Patients With Carpal Tunnel Syndrome?

BACKGROUND

It has been observed that patients with carpal tunnel syndrome (CTS) who also experience emotional distress, depression, or anxiety report more severe symptoms. As patients' own perspectives about their health increasingly are guiding treatment decisions, it seems important to study the simultaneous association of psychological distress and neuropathology with hand disability in patients who have CTS, as this may help prioritize and sequence management steps.

QUESTIONS/PURPOSES

What are the relationships among validated scores for (1) depression, (2) anxiety, (3) pain catastrophizing, and (4) nerve electrodiagnostic severity with measures of hand disability in patients with confirmed CTS?

METHODS

Between 2017 and 2019, we evaluated 116 patients for CTS in a referral urban hospital in Mashhad, Iran. Of those, we considered 85% (99) as potentially eligible by considering the following Electromyography-Nerve Conduction Study (EMG-NCS) diagnostic criteria: sensory latency ≥ 3.5 Ms, median-ulnar latency difference ≥ 0.5 Ms, motor latency ≥ 4.2 Ms, and abnormal EMG findings in the opponens pollicis muscle (neurogenic motor unit action potentials, positive sharp waves, or fibrillation). A further 13% (15 of 116) were excluded because of nonidiopathic CTS and prior surgery, and another 12% (14 of 116) were lost because of incomplete datasets, leaving 60% (70 of 116) for final inclusion in this cross-sectional study. In all, 89% of patients were women with total mean age of 47 years. We measured depression and anxiety using the Hospital Anxiety and Depression Scale (HADS) questionnaire (scored from 0 to 21, with a minimum clinically important difference [MCID] of 1.7 points), and we evaluated patients' state of mind regarding pain using the Pain Catastrophizing Scale (PCS) (scored from 0 to 52). Higher scores on these questionnaires represent more distress and pain catastrophizing. Hand disability was assessed with Quick Disabilities of the Arm, Shoulder, and Hand (QuickDASH) questionnaire outcomes (scored from 0 [no disability] to 100 [most severe disability]; MCID of 15 points), Likert pain score (from 0 to 10), and grip/pinch dynamometry results. Correlational analyses were conducted once among HADS and PCS scores and again among EMG-NCS indices with pain and disability variables to answer our first, third, and fourth questions, respectively. Regression analysis was performed to assess the percentage of variance in QuickDASH and pain severity, which could be explained by psychological and electrodiagnostic factors. We did not include grip and pinch in our multivariable model (regression analysis) as dependent variables because they did not correlate with any of psychological or EMG-NCS variables (all p values > 0.1). Significance was set at p < 0.05.

RESULTS

Correlational analysis showed that the scores of all three psychological questionnaires correlated with the QuickDASH score (r = 0.50, 0.42, and 0.53 for HADS-A, HADS-D, and PCS, respectively; p < 0.001 for all three), while EMG-NCS parameters had no correlation with QuickDASH and pain scores. We also found that 37% of the variance in QuickDASH score can be explained by HADS and PCS scores (r2 = 0.37; p < 0.001).

CONCLUSION

Evaluation and treatment of psychological distress before deciding on elective surgery for CTS is important because patient-reported disability-often used as a factor in surgical decision-making-is substantially correlated with emotional distress. Future prospective, controlled studies on this topic are recommended; ideally, these should evaluate psychological interventions specifically to ascertain whether they improve patients' ratings of hand disability.

LEVEL OF EVIDENCE

Level III, prognostic study.

Efficiency of 90-Min Extended EMLA-Induced Stimulated Skin-Wrinkling Test in the Diagnosis of Carpal Tunnel Syndrome

Background:

Previous researchers have used a 30-min eutectic mixture of local anesthetic (EMLA) test, which assesses the sympathetically mediated vasomotor function, in diagnosing carpal tunnel syndrome (CTS). However, its specificity was low, limiting its clinical diagnostic utility. In this study, we assessed the efficiency of 90-min extended EMLA-induced stimulated skin-wrinkling (SSW) test in CTS diagnosis.

Methods:

A cross-sectional study was designed among patients clinically diagnosed with CTS. Hands of healthy volunteers and the asymptomatic hands of selected patients served as control. The Boston symptom severity scale (SSS) and the neuropathic pain severity inventory (NPSI) were used to assess symptom severity, and nerve conduction study (NCS) was used to assess electrophysiological severity. EMLA-induced SSW was visually graded after 90 min of application and correlated with symptom and NCS severities.

Results:

Forty-two symptomatic hands and 30 asymptomatic hands were enrolled as cases and controls, respectively. The diagnostic efficiency of the extended EMLA test was found to be 83.4% for digit 2 and 87.3% for the lateral 4 digits (mean), whereas the diagnostic efficiency of standard NCS was 88.1%. Boston SSS and NPSI were better correlated with EMLA positivity than NCS positivity. A linear regression analysis showed negative correlation of wrinkling grade with NCS grade.

Conclusion:

With its improved diagnostic efficiency, the 90-min extended EMLA test can feasibly be used as an alternative to NCS, especially in general practice settings. Its potential clinical utility should be explored in a large population of CTS patients showing varying clinical and electrophysiological severities.

Pain mechanisms in carpal tunnel syndrome: a systematic review and meta-analysis of quantitative sensory testing outcomes

ABSTRACT

Carpal tunnel syndrome (CTS) is the most common nerve compression in the arm. A mix of peripheral and central contributions on quantitative sensory testing (QST) has been reported in the literature. Thus, this systematic review or meta-analysis aimed to identify the dominant sensory phenotype and draw conclusive evidence about the presence of central sensitization (CS) in CTS. Based on an a priori published protocol and using PRISMA guidelines, 7 databases were searched (Embase, Web of Science, Scopus, PubMed, SAGE, EBSCOhost, and ProQuest). Eligible studies compared the QST findings of individuals with subacute and chronic CTS with those of healthy controls through thermal, mechanical, and vibration detection thresholds; thermal, pressure, and mechanical pain thresholds; mechanical pain sensitivity; presence of allodynia; wind-up ratio; and conditioned pain modulation. Thirty-seven studies were included in the qualitative analysis. Results showed a significant loss of all detection thresholds of hand median nerve territories and hand extramedian areas (little finger and hand dorsum) in CTS (P < 0.05) but no significant difference (P > 0.05) in wind-up ratio, cold, heat, or mechanical pain thresholds of the median nerve territories. Furthermore, there was a significant increase in mechanical pain sensitivity in median nerve territories and remotely in the forearm (P < 0.05) and a significant gain in pressure and heat pain thresholds in the carpal area (P < 0.05). Conditioned pain modulation was impaired in CTS. Hypoesthesia and increased thermal and mechanical pain ratings are the dominant sensory phenotype with inconclusive evidence about CS in CTS due to the heterogenous results of thermal and mechanical pain thresholds.

Application of digital infrared thermography for carpal tunnel syndrome evaluation

We investigated the thermographic findings of carpal tunnel syndrome (CTS). We enrolled 304 hands with electrodiagnostically identified CTS and 88 control hands. CTS hands were assigned to duration groups (D1, < 3 months; D2, 3‒6 months; D3, 6‒12 months; D4, ≥ 12 months) and severity groups (S1, very mild; S2, mild; S3, moderate; S4, severe). The temperature difference between the median and ulnar nerve territories (ΔM-U territories) decreased as CTS duration and severity increased. Significant differences in ΔM-U territories between the D1 and D3, D1 and D4, D2 and D4, and S1 and S4 groups (P = 0.003, 0.001, 0.001, and < 0.001, respectively) were observed. Thermal anisometry increased as CTS duration and severity increased. Significant differences in thermal anisometry between the D1 and D4 as well as the D2 and D4 groups (P = 0.005 and 0.04, respectively) were noted. Thermal anisometry was higher in the S4 group than in the S1, S2, and S3 groups (P = 0.009, < 0.001, and 0.003, respectively). As CTS progresses, skin temperature tends to decrease and thermal variation tends to increase in the median nerve-innervated area. Thermographic findings reflect the physiological changes of the entrapped median nerve.

[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 clinical and neurophysiological analysis of idiopathic carpal tunnel syndrome with respect to gender and occupation

Background:

Carpal tunnel syndrome (CTS) predominantly affects women. Previous studies observed more intense symptoms among women without a corresponding increase in disease severity and attributed it to reporting bias. In this study, we examined whether women are inherently more vulnerable to work related median nerve dysfunction at wrist and whether reported CTS symptoms among women correspond to the degree of median neuropathy at wrist.

Methods:

A cross-sectional study was designed for outpatients (aged 25-59 years) diagnosed with CTS. Occupational categorisation was done based on the analysis of their individual job tasks. Symptom severity (Boston Symptom Severity Scale – SSS), functional disability (Boston Functional Status Scale - FSS), and clinical (Hi – Ob scale) and neurophysiological severity (NCS grade) were determined, compared among occupational groups and were statistically analysed.

Results:

A total of 454 patients (348 women and 106 men; F: M ratio 3.28:1) were included. Among them, 191 were housewives. Female manual workers and housewives reported significantly more intense symptoms with a corresponding increase in clinical and electrophysiological severity (p < 0.001) when compared to female non-manual workers. However, no significant difference in symptoms, clinical or neurophysiological severity was found between male non-manual and manual workers. Among manual workers, women were more symptomatic than men, but clinical and neurophysiological severities were significantly higher only in the older age groups.

Conclusion:

The differential vulnerability of the female population to hand-intensive work predisposes them to severe median nerve dysfunction at wrist with proportionately higher CTS symptoms. Therefore, working women need focussed attention for remedial measures.

Evaluation of Duruöz Hand Index in diagnosis and staging of Carpal tunnel syndrome

Carpal tunnel syndrome (CTS) is a common entrapment neuropathy of the upper limb. In this cross-sectional study our aim is to investigate the value of Duruöz Hand Index (DHI) in diagnosis and staging of CTS patients and comparing it with Boston Carpal Tunnel Questionnaire (BQ) and provocative tests. Among 423 patients who were referred to the EMG laboratory at the physical medicine and rehabilitation unit with the symptoms of CTS, 294 patients were included in the study. Patients' demographic data, weight, height, body mass index (BMI) measurements, physical examinations, Tinel and Phalen provocative test results, visual analog scale for pain, DHI and BQ scores were recorded. Electrophysiological examinations were also performed. The mean age was 45.1 ± 11.6 years and 254 (86.4%) patients were women. Based on the results of EMG, 120 (40.8%) patients were found negative for CTS, 57 (19.4%) patients had mild CTS, 89 (30.3%) patients had moderate CTS and 28 (9.5%) patients had severe CTS. Among the parameters evaluated, DHI scores were found to be significantly higher in the severe CTS group. DHI (r: 0.306, p < 0.001) and Boston functional status scale (FSS) (r: 0.257p = 0.001) were found to be correlated with CTS severity. Tinel positivity (OR: 2.36, p: 0.01), Phalen positivity (OR: 2.22, p: 0.02), Boston symptom severity scale (SSS) scores (OR: 1.76, p: 0.024), increasing age (OR: 1.06, p < 0.001) and increased BMI (OR: 1.07, p: 0.03) were found to be associated with increased likelihood of CTS diagnosis. In conclusion, DHI was found to be correlated with CTS severity similar to Boston FSS.

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.

Subsynovial connective tissue thickness in carpal tunnel syndrome: A systematic review

BACKGROUND

Non-inflammatory thickening of the subsynovial connective tissue is a common histological finding in carpal tunnel syndrome. This subsynovial connective tissue thickening may precede changes in electrodiagnostic testing. Therefore, measuring subsynovial connective tissue thickness may help in detecting early changes in carpal tunnel syndrome.

METHODS

To provide an overview of subsynovial connective tissue thickness characteristics in subjects with and without carpal tunnel syndrome, a systematic review of articles, assessing human subsynovial connective tissue, was performed using MEDLINE, CENTRAL and EMBASE.

FINDINGS

Seven studies were included for qualitative analysis. Measurements were done ex vivo (laser (n = 3), photographic (n = 1), micrometric (n = 1)) and in vivo (ultrasound (n = 3)). All four case-control studies showed a significant difference in subsynovial connective tissue thickness between subjects with and without carpal tunnel syndrome. One study showed good correlation between ultrasound and anatomical measurements. No correlation was found between subsynovial connective tissue thickness and symptom duration, electrodiagnostic changes, age and sex.

INTERPRETATION

Subsynovial connective tissue thickness may be a valuable aid in diagnosing carpal tunnel syndrome. No factors influencing subsynovial connective tissue thickness are identified, although they are not well investigated.

Diagnostic accuracy of upper limb neurodynamic tests for the assessment of peripheral neuropathic pain: A systematic review

BACKGROUND

Upper limb neurodynamic tests (ULNTs) are used to identify a neuropathic pain component in patients' presenting with arm and/or neck pain. Clinical tests with established diagnostic accuracy are required to not only to inform clinical management but also minimise costs associated with expensive medical investigations.

OBJECTIVE

To evaluate the role of ULNTs in assessment of peripheral neuropathic pain and to inform their value in clinical practice when assessing patients with arm and/or neck symptoms.

DESIGN

Systematic review was undertaken according to published guidelines, and reported in line with PRISMA-DTA.

METHOD

Key databases were searched up to 21/11/2017.

INCLUSION CRITERIA

Patient population experiencing arm and/or neck symptoms with suspected peripheral neuropathic involvement, studies that compared ULNT to a reference standard, any study design using primary diagnostic accuracy data. Two reviewers independently assessed risk of bias (ROB) using QUADAS-2. The overall quality of evidence was evaluated using GRADE.

RESULTS

Of eight included studies (n = 579), four were assessed as low ROB, although all had concerns regarding applicability. For carpal tunnel syndrome, ULNT1 sensitivity values ranged 0.4-0.93, specificity 0.13-0.93, positive likelihood ratio 0.86-3.67 and negative likelihood ratio 0.5-1.9. For cervical radiculopathy ULNT1 and the combined use of four ULNTs had sensitivity of 0.97 (95%CI 0.85-1.00) whereas the ULNT3 was the most specific (0.87, 95%CI 0.62-0.98). Positive likelihood ratio ranged 0.58-5.68 and negative likelihood ratio 0.12-1.62.

CONCLUSION

Based on the available evidence ULNTs cannot be utilised as a stand-alone test for the diagnosis of CTS. Limited evidence suggests that ULNTs may be clinically relevant for the diagnosis of CR, but only as a "ruling out" strategy. However, the overall quality of the body of evidence after applying the GRADE approach was low to very low across studies. Further higher quality research is needed to establish firm conclusions.

Preventive skin analgesia with lidocaine patch for management of post-thoracotomy pain: Results of a randomized, double blind, placebo controlled study

Background

To evaluate whether pre‐emptive skin analgesia using a lidocaine patch 5% would improve the effects of systemic morphine analgesia for controlling acute post‐thoracotomy pain.

Methods

This was a double‐blind, placebo controlled, prospective study. Patients were randomly assigned to receive lidocaine 5% patch (lidocaine group) or a placebo (placebo group) three days before thoracotomy. Postoperative analgesia was induced in all cases with intravenous morphine analgesia. The intergroup differences were assessed in order to evaluate whether the lidocaine patch 5% would have effects on pain intensity when at rest and after coughing (primary end‐point) on morphine consumption, on the recovery of respiratory function, and on peripheral painful pathways measured with N2 and P2 laser‐evoked potential (secondary end‐points).

Results

A total of 90 patients were randomized, of whom 45 were allocated to the lidocaine group and 45 to the placebo group. Lidocaine compared with the placebo group showed a significant reduction in pain intensity both at rest (P = 0.013) and after coughing (P = 0.015), and in total morphine consumption (P = 0.001); and also showed a better recovery of flow expiratory volume in one second (P = 0.025) and of forced vital capacity (P = 0.037). The placebo group compared with the lidocaine group presented a reduction in amplitude of N2 (P = 0.001) and P2 (P = 0.03), and an increase in the latency of N2 (P = 0.023) and P2 (P = 0.025) laser‐evoked potential.

Conclusions

The preventive skin analgesia with lidocaine patch 5% seems to be a valid adjunct to intravenous morphine analgesia for controlling post‐thoracotomy pain. However, our initial results should be corroborated/confirmed by larger studies.

Sensory profiles are comparable in patients with distal and proximal entrapment neuropathies, while the pain experience differs

OBJECTIVE

Distal and proximal entrapment neuropathies such as carpal tunnel syndrome (CTS) and cervical radiculopathy (CR) share similar etiologies. Experimental models suggest that, despite comparable etiology, pathomechanisms associated with injuries of the peripheral and central axon branches are distinct. This study therefore compared self-reported and elicited sensory profiles in patients with distal and proximal entrapment neuropathies.

METHODS

Patients with electrodiagnostically confirmed CTS (n = 103) and patients with CR (n = 23) were included in this study. A group of healthy participants served as controls (n = 39). Symptoms and sensory profiles were evaluated using quantitative sensory testing (QST) and a self-reported neuropathic pain questionnaire (painDETECT).

RESULTS

Both patient groups were characterized by a loss of function in thermal and mechanical detection in the main pain area and dermatome compared to healthy reference data (p < .001). There was no significant difference between patients with CTS and CR in pain and detection thresholds except for reduced vibration sense in the main pain area (p < .001) and reduced pressure pain sensitivity in the dermatome in patients with CR (p < .001). However, patients with CR reported higher pain intensities (p = .008), more severe pain attacks (p = .009) and evoked pain by light pressure (p = .002) compared to patients with CTS.

CONCLUSION

While QST profiles were similar between patients with CTS and CR, self-reported pain profiles differed and may suggest distinct underlying mechanisms in these patient cohorts.

Validity of Clinical Small-Fiber Sensory Testing to Detect Small-Nerve Fiber Degeneration

BACKGROUND

Small-nerve fiber, or small-fiber, degeneration commonly occurs in patients with peripheral neuropathies, resulting in a deterioration of nerve function. Currently, the gold standard to identify small-fiber degeneration is through skin biopsy. Simple clinical tests aim to identify small-fiber degeneration, but their validity remains unknown.

OBJECTIVES

To examine the validity of clinical tests to assess small-nerve fiber degeneration, using carpal tunnel syndrome as a model neuropathy.

METHODS

One hundred seven participants (22 healthy, 85 with carpal tunnel syndrome) in this prospective, cross-sectional diagnostic accuracy study underwent pinprick testing of the index finger and were assessed for cold detection threshold and warm detection threshold using quantitative sensory testing. In a subgroup of patients with carpal tunnel syndrome (n = 51), cold and warm sensations were also tested, using coins at room and body temperature, respectively. The validity of these clinical tests was established against intra-epidermal nerve fiber density measured in skin biopsies from the index finger.

RESULTS

Optimal validity occurred with clusters of tests. Specifically, normal warm or cold sensation is highly sensitive to rule out small-fiber degeneration (sensitivity, 0.98; 95% confidence interval [CI]: 0.85, 0.99), but has a low specificity (0.20; 95% CI: 0.03, 0.52). By contrast, a reduction in pinprick is highly specific (0.88; 95% CI: 0.72, 0.95), and so can be used to rule in small-fiber degeneration. For quantitative sensory testing, the highest specificity (0.83) occurs for warm detection threshold and the highest sensitivity (0.84; 95% CI: 0.72, 0.91) for cold detection threshold or warm detection threshold.

CONCLUSION

Pinprick testing, followed by warm and cold tests if pinprick is normal, is a valid and cost-effective method to detect small-fiber degeneration. For quantitative sensory testing, warm detection threshold is useful for ruling in small-fiber degeneration. To rule out small-fiber degeneration, both cold detection threshold and warm detection threshold must be negative.

LEVEL OF EVIDENCE

Diagnosis, level 2. J Orthop Sports Phys Ther 2018;48(10):767-774. Epub 22 Jun 2018. doi:10.2519/jospt.2018.8230.

Entrapment Neuropathies: Challenging Common Beliefs With Novel Evidence

Entrapment neuropathies are the most prevalent type of peripheral neuropathy and often a challenge to diagnose and treat. To a large extent, our current knowledge is based on empirical concepts and early (often biomechanical) studies. This Viewpoint will challenge some of the current beliefs with recent advances in both basic and clinical neurosciences. J Orthop Sports Phys Ther 2018;48(2):58-62. doi:10.2519/jospt.2018.0603.

A novel chronic nerve compression model in the rat

Current animal models of chronic peripheral nerve compression are mainly silicone tube models. However, the cross section of the rat sciatic nerve is not a perfect circle, and there are differences in the diameter of the sciatic nerve due to individual differences. The use of a silicone tube with a uniform internal diameter may not provide a reliable and consistent model. We have established a chronic sciatic nerve compression model that can induce demyelination of the sciatic nerve and lead to atrophy of skeletal muscle. In 3-week-old pups and adult rats, the sciatic nerve of the right hind limb was exposed, and a piece of surgical latex glove was gently placed under the nerve. N-butyl-cyanoacrylate was then placed over the nerve, and after it had set, another piece of glove latex was placed on top of the target area and allowed to adhere to the first piece to form a sandwich-like complex. Thus, a chronic sciatic nerve compression model was produced. Control pups with latex or N-butyl-cyanoacrylate were also prepared. Functional changes to nerves were assessed using the hot plate test and electromyography. Immunofluorescence and electron microscopy analyses of the nerves were performed to quantify the degree of neuropathological change. Masson staining was conducted to assess the degree of fibrosis in the gastrocnemius and intrinsic paw muscles. The pup group rats subjected to nerve compression displayed thermal hypoesthesia and a gradual decrease in nerve conduction velocity at 2 weeks after surgery. Neuropathological studies demonstrated that the model caused nerve demyelination and axonal irregularities and triggered collagen deposition in the epineurium and perineurium of the affected nerve at 8 weeks after surgery. The degree of fibrosis in the gastrocnemius and intrinsic paw muscles was significantly increased at 20 weeks after surgery. In conclusion, our novel model can reproduce the functional and histological changes of chronic nerve compression injury that occurs in humans and it will be a useful new tool for investigating the mechanisms underlying chronic nerve compression.

Facilitatory and inhibitory pain mechanisms are altered in patients with carpal tunnel syndrome

Preliminary evidence from studies using quantitative sensory testing suggests the presence of central mechanisms in patients with carpal tunnel syndrome (CTS) as apparent by widespread hyperalgesia. Hallmarks of central mechanisms after nerve injuries include nociceptive facilitation and reduced endogenous pain inhibition. Methods to study nociceptive facilitation in CTS so far have been limited to quantitative sensory testing and the integrity of endogenous inhibition remains unexamined. The aim of this study was therefore to investigate changes in facilitatory and inhibitory processing in patients with CTS by studying hypersensitivity following experimentally induced pain (facilitatory mechanisms) and the efficacy of conditioned pain modulation (CPM, inhibitory mechanisms). Twenty-five patients with mild to moderate CTS and 25 age and sex matched control participants without CTS were recruited. Increased pain facilitation was evaluated via injection of hypertonic saline into the upper trapezius. Altered pain inhibition through CPM was investigated through cold water immersion of the foot as the conditioning stimulus and pressure pain threshold over the thenar and hypothenar eminence bilaterally as the test stimulus. The results demonstrated that patients with CTS showed a greater duration (p = 0.047), intensity (p = 0.044) and area (p = 0.012) of pain in response to experimentally induced pain in the upper trapezius and impaired CPM compared to the control participants (p = 0.006). Although typically considered to be driven by peripheral mechanisms, these findings indicate that CTS demonstrates characteristics of altered central processing with increased pain facilitation and reduced endogenous pain inhibition.

Negative Neurodynamic Tests Do Not Exclude Neural Dysfunction in Patients With Entrapment Neuropathies

Objective

To examine differences in somatosensory phenotypes of patients with positive and negative neurodynamic tests and compare these with healthy participants.

Design

Case-control study.

Setting

University department.

Participants

Patients with electrodiagnostically confirmed carpal tunnel syndrome (CTS) (n=53) and people without CTS (n=26) participated in this study (N=79). Patients with CTS were subgrouped according to the results of the upper limb neurodynamic tests biasing the median nerve into patients with positive or negative neurodynamic tests.

Interventions

Not applicable.

Main Outcome Measure

All participants underwent quantitative sensory testing in the median innervated territory of their hand.

Results

Only 46% of patients with CTS had positive neurodynamic tests. No differences were identified between groups for pain thresholds (P>.247). However, patients with CTS had increased mechanical (P<.0001) and thermal detection thresholds (P<.0001) compared with people without CTS. Patients with negative neurodynamic tests had a more pronounced vibration detection deficit (mean, 7.43±0.59) than people without CTS (mean, 7.89±0.22; P=.001). Interestingly, warm detection was the only domain differentiating positive (mean, 4.03°C±2.18°C) and negative neurodynamic test groups (6.09°C±3.70°C, P=.032), with patients with negative neurodynamic tests demonstrating increased loss of function.

Conclusions

Patients with negative neurodynamic tests seem to have a more severe dysfunction of the unmyelinated fiber population. Our findings suggest that neurodynamic tests should not be used in isolation to judge neural involvement. Rather, they should be interpreted in the context of loss of function tests of the small fiber domain.

Confirmatory Factor Analysis of the Boston Carpal Tunnel Questionnaire

PURPOSE

Carpal tunnel syndrome (CTS) is one of the most common hand problems and a major cause of work disability. The purpose of this study was to use confirmatory factor analysis (CFA) to assess the factor structure of the Boston Carpal Tunnel Questionnaire (BCTQ) in patients with CTS.

METHODS

One hundred and twenty-three patients with CTS were recruited from two hospitals. Each patient completed the functional status scale and the symptom severity scale of the BCTQ. CFA was used to assess the model fit between the data and pre-established theoretical measurement models.

RESULTS

CFA showed that all three-factor models were better than the original two-factor model. Among the three-factor models, the simplified model, with 11 items assessing daytime pain, nocturnal numbness/tingling, and hand function was the best, for the model fit the data better than did the other models. Specifically, the Comparative Indices were larger than 0.95 (Tucker-Lewis Index and Comparative Fit Index values), and the Absolute Fit Indices and information-theoretic measures were the smallest. Moreover, all factor loadings were significant and high in magnitude (ranging from 0.66 to 0.99), the composite reliabilities exceeded 0.60 (ranging from 0.78 to 0.94), and the average variance extracted exceeded 0.50 (ranging from 0.61 to 0.89).

CONCLUSION

The simplified model showed the highest reliability and validity, and the factor structure was the simplest/clearest one. The simplified model is recommended for clinical use due to its convenience and precision for assessing the problems of patients with CTS.

Older Age as a Prognostic Factor of Attenuated Pain Recovery After Shoulder Arthroscopy

BACKGROUND

Shoulder pain and surgery are common among older adults. However, the extent to which older age affects recovery after shoulder surgery is not well understood.

OBJECTIVE

To assess influence of older age on postoperative recovery factors 3 and 6 months after shoulder arthroscopy.

DESIGN

Prospective cohort study.

SETTING

University-affiliated outpatient orthopedic surgical center.

PATIENTS

A convenience sample of 139 persons between 20 and 79 years of age who experienced shoulder pain, had musculoskeletal dysfunction based on imaging and physician assessment, and were scheduled for an arthroscopic shoulder procedure.

MAIN OUTCOME MEASURES

Postoperative outcomes were compared among younger, middle-aged, and older adults before surgery and at 3 and 6 months after surgery using analysis of variance modeling. Movement-evoked pain and an experimental laboratory correlate of pain processing were assessed at each time point. The influence of older age on 3- and 6-month pain outcomes were determined via multivariate regression analyses after accounting for preoperative, intraoperative, and postoperative prognostic factors.

RESULTS

Older adults had higher movement-evoked pain intensity (F2,108 = 5.18, P = .007) and experimental pain response (F2,111 = 7.24, P = .001) at 3 months compared with young and middle-aged adults. After controlling for key prognostic factors, older age remained a positive predictor of 3-month movement-evoked pain (R(2) = 0.05; standardized [St.] β = 0.263, P = .031) and experimental pain response (R(2) = 0.07; St. β = 0.295, P = .014). Further, older age remained a positive predictor of movement-evoked pain at 6 months (R(2) = 0.04; St. β = 0.231, P = .004), despite no age group differences in outcome. Older age was found to be the strongest predictor of 3- and 6-month movement-evoked pain.

CONCLUSION

Older adults may experience more pain related to movement, as well as endogenous pain excitation, in the first few months after shoulder arthroscopy. Future age-related research should consider use of movement-evoked pain intensity and experimental pain response as pain outcomes, as well as the utility of such measures in clinical care.

The Association between Serum Cytokines and Damage to Large and Small Nerve Fibers in Diabetic Peripheral Neuropathy

Diabetic peripheral neuropathy (DPN) is a frequent complication of type 2 diabetes mellitus (DM) and may involve small and large peripheral nerve fibers. Recent evidence suggests a role of cytokines in DPN. The paper is aimed at exploring whether the serum concentration of cytokines is associated with small and large nerve fiber function and with neuropathic pain (NP). We recruited a group of 32 type 2 DM patients who underwent serum cytokines (TNF-α, IL-2, IL-4, IL-6, and IL-10) dosage as well as electrodiagnostic and quantitative sensory testing (QST) assessment to explore damage to large and small nerve fibers. Raised serum levels of IL-6 and IL-10 correlated with markers of large nerve fiber sensory and motor axonal damage. Raised IL-10 serum level was associated with signs of motor nerve demyelination. No differences were found in pain characteristics and electrodiagnostic and QST markers of small nerve fiber function in relation to cytokines serum levels. IL-6 and IL-10 serum levels were associated with large nerve fiber damage but not to small fibers function or NP. IL-6 and IL-10 cytokines might play a role in the pathogenesis of nerve fiber damage or represent a compensatory or neuroprotective mechanism.

The relationship of nerve fibre pathology to sensory function in entrapment neuropathy

The impact of peripheral entrapment neuropathies on target innervation remains unknown. Using quantitative sensory testing, neurophysiology and skin biopsies, Schmid et al. demonstrate that carpal tunnel syndrome affects large fibres and their nodal complexes, but is also associated with a reduction in the number and functioning of small sensory axons.

Surprisingly little is known about the impact of entrapment neuropathy on target innervation and the relationship of nerve fibre pathology to sensory symptoms and signs. Carpal tunnel syndrome is the most common entrapment neuropathy; the aim of this study was to investigate its effect on the morphology of small unmyelinated as well as myelinated sensory axons and relate such changes to somatosensory function and clinical symptoms. Thirty patients with a clinical and electrophysiological diagnosis of carpal tunnel syndrome [17 females, mean age (standard deviation) 56.4 (15.3)] and 26 age and gender matched healthy volunteers [18 females, mean age (standard deviation) 51.0 (17.3)] participated in the study. Small and large fibre function was examined with quantitative sensory testing in the median nerve territory of the hand. Vibration and mechanical detection thresholds were significantly elevated in patients with carpal tunnel syndrome (P < 0.007) confirming large fibre dysfunction and patients also presented with increased thermal detection thresholds (P < 0.0001) indicative of C and Aδ-fibre dysfunction. Mechanical and thermal pain thresholds were comparable between groups (P > 0.13). A skin biopsy was taken from a median nerve innervated area of the proximal phalanx of the index finger. Immunohistochemical staining for protein gene product 9.5 and myelin basic protein was used to evaluate morphological features of unmyelinated and myelinated axons. Evaluation of intraepidermal nerve fibre density showed a striking loss in patients (P < 0.0001) confirming a significant compromise of small fibres. The extent of Meissner corpuscles and dermal nerve bundles were comparable between groups (P > 0.07). However, patients displayed a significant increase in the percentage of elongated nodes (P < 0.0001), with altered architecture of voltage-gated sodium channel distribution. Whereas neither neurophysiology nor quantitative sensory testing correlated with patients’ symptoms or function deficits, the presence of elongated nodes was inversely correlated with a number of functional and symptom related scores (P < 0.023). Our findings suggest that carpal tunnel syndrome does not exclusively affect large fibres but is associated with loss of function in modalities mediated by both unmyelinated and myelinated sensory axons. We also document for the first time that entrapment neuropathies lead to a clear reduction in intraepidermal nerve fibre density, which was independent of electrodiagnostic test severity. The presence of elongated nodes in the target tissue further suggests that entrapment neuropathies affect nodal structure/myelin well beyond the focal compression site. Interestingly, nodal lengthening may be an adaptive phenomenon as it inversely correlates with symptom severity.

Local and remote immune-mediated inflammation after mild peripheral nerve compression in rats

After experimental nerve injuries that extensively disrupt axons, such as chronic constriction injury, immune cells invade the nerve, related dorsal root ganglia (DRGs), and spinal cord, leading to hyperexcitability, raised sensitivity, and pain. Entrapment neuropathies, such as carpal tunnel syndrome, involve minimal axon damage, but patients often report widespread symptoms. To understand the underlying pathology, a tube was placed around the sciatic nerve in 8-week-old rats, leading to progressive mild compression as the animals grew. Immunofluorescence was used to examine myelin and axonal integrity, glia, macrophages, and T lymphocytes in the nerve, L5 DRGs, and spinal cord after 12 weeks. Tubes that did not constrict the nerve when applied caused extensive and ongoing loss of myelin, together with compromise of small-, but not large-, diameter axons. Macrophages and T lymphocytes infiltrated the nerve and DRGs. Activated glia proliferated in DRGs but not in spinal cord. Histologic findings were supported by clinical hyperalgesia to blunt pressure and cold allodynia. Tubes that did not compress the nerve induced only minor local inflammation. Thus, progressive mild nerve compression resulted in chronic local and remote immune-mediated inflammation depending on the degree of compression. Such neuroinflammation may explain the widespread symptoms in patients with entrapment neuropathies.

Quantitative sensory testing of neuropathic pain patients: potential mechanistic and therapeutic implications

Quantitative sensory testing (QST) is a widely accepted tool to investigate somatosensory changes in pain patients. Many different protocols have been developed in clinical pain research within recent years. In this review, we provide an overview of QST and tested neuroanatomical pathways, including peripheral and central structures. Based on research studies using animal and human surrogate models of neuropathic pain, possible underlying mechanisms of chronic pain are discussed. Clinically, QST may be useful for 1) the identification of subgroups of patients with different underlying pain mechanisms; 2) prediction of therapeutic outcomes; and 3) quantification of therapeutic interventions in pain therapy. Combined with sensory mapping, QST may provide useful information on the site of neural damage and on mechanisms of positive and negative somatosensory abnormalities. The use of QST in individual patients for diagnostic purposes leading to individualized therapy is an interesting concept, but needs further validation.

Neuropathic pain: is quantitative sensory testing helpful?

Neuropathic pain arises as a consequence of a lesion or disease affecting the somatosensory system and is characterised by a combination of positive and negative sensory symptoms. Quantitative sensory testing (QST) examines the sensory perception after application of different mechanical and thermal stimuli of controlled intensity and the function of both large (A-beta) and small (A-delta and C) nerve fibres, including the corresponding central pathways. QST can be used to determine detection, pain thresholds and stimulus-response curves and can thus detect both negative and positive sensory signs, the second ones not being assessed by other methods. Similarly to all other psychophysical tests QST requires standardised examination, instructions and data evaluation to receive valid and reliable results. Since normative data are available, QST can contribute also to the individual diagnosis of neuropathy, especially in the case of isolated small-fibre neuropathy, in contrast to the conventional electrophysiology which assesses only large myelinated fibres. For example, detection of early stages of subclinical neuropathy in symptomatic or asymptomatic patients with diabetes mellitus can be helpful to optimise treatment and identify diabetic foot at risk of ulceration. QST assessed the individual's sensory profile and thus can be valuable to evaluate the underlying pain mechanisms which occur in different frequencies even in the same neuropathic pain syndromes. Furthermore, assessing the exact sensory phenotype by QST might be useful in the future to identify responders to certain treatments in accordance to the underlying pain mechanisms.

Power spectral analyses of index finger skin blood perfusion in carpal tunnel syndrome and diabetic polyneuropathy

The main purpose of this study was to investigate the applicability of frequency domain analysis on laser Doppler flowmetry (LDF) data recorded from the index fingers of patients with carpal tunnel syndrome (CTS) and diabetic polyneuropathy (DPN). Patients with numbness of the palm were recruited and grouped according to the results of electrophysiological examinations into 2×2 groups by the existence or nonexistence of CTS and/or DPN. Skin blood perfusion was recorded by LDF in both the neutral position and the maximally flexed position (the Phalen test). S-transformation was utilized to decompose the recorded data into frequency bands, and the relative band power and power dispersion were calculated. Analysis of variance was used to test the effects of DPN, CTS, and the Phalen test results. The results showed that (1) DPN decreased the absolute power and the relative power in some frequency bands in both positions and CTS increased the power dispersion of some frequency bands only during the Phalen test and (2) there was no difference in the LDF results between patients with positive or negative Phalen test results.