Comparison of vibration perception thresholds in individuals with diffuse upper limb pain and carpal tunnel syndrome

Carpal Tunnel Syndrome: Neuropathic Pain Associated or Not with a Nociplastic Condition

Carpal tunnel syndrome (CTS) has been traditionally classified as primarily a neuropathic condition with or without pain. Precision medicine refers to an evidence-based method of grouping patients based on their susceptibility to biology, prognosis of a particular disease, or in their response to a specific treatment, and tailoring specific treatments accordingly. In 2021, the International Association for the Study of Pain (IASP) proposed a grading system for classifying patients into nociceptive, neuropathic, or nociplastic phenotypes. This position paper presents data supporting the possibility of subgrouping individuals with specific CTS related-pain into nociceptive, neuropathic, nociplastic or mixed-type phenotypes. Carpal tunnel syndrome is a neuropathic condition but can also be comorbid with a nociplastic pain condition. The presence of extra-median symptoms and the development of facilitated pain processing seem to be signs suggesting that specific CTS cases can be classified as the nociplastic pain phenotype. The clinical responses of therapeutic approaches for the management of CTS are inconclusive. Accordingly, the ability to identify the predominant pain phenotype in patients with CTS could likely be problematic for producing efficient treatment outcomes. In fact, the presence of a nociplastic or mixed-type pain phenotype would explain the lack of clinical effect of treatment interventions targeting the carpal tunnel area selectively. We propose a clinical decision tree by using the 2021 IASP classification criteria for identifying the predominant pain phenotype in people with CTS-related pain, albeit CTS being a priori a neuropathic pain condition. The identification of a nociplastic-associated condition requires a more nuanced multimodal treatment approach to achieve better treatment outcomes.

Evaluation of Cold Sensitivity in Patients With Upper Extremity Nerve Compression Syndromes: A Scoping Review

PURPOSE

The aim of this study was to review the literature to determine the prevalence of cold sensitivity in upper extremity nerve compression syndromes and the impact of treating nerve compression syndromes on cold sensitivity.

METHODS

Following a standardized scoping review protocol, this study included interventional and observational study designs assessing patients with cold sensitivity and upper extremity nerve compression syndromes. Review articles, case reports, and small case series (n < 5) were excluded. The abstracts and eligible full texts were screened by 2 independent reviewers. Data were extracted and reported according to PRISMA extension for scoping reviews statement.

RESULTS

Three databases were searched (Ovid MEDLINE, Ovid EMBASE, and CINAHL on EBSCO); 274 references were reviewed. Fifteen studies from the database search and 8 studies from the reference search were eligible for this review (n = 23). Two interventional and 21 observational studies were identified. The most common method for assessing cold sensitivity was cold pain threshold testing (n = 12), followed by subjective patient reporting (n = 4). The Cold Intolerance Symptom Severity questionnaire was the most common validated patient-reported outcome questionnaire used in the studies (n = 3). Cold sensitivity was most commonly reported in carpal tunnel syndrome (96% of the studies). The prevalence of cold sensitivity in nerve compression syndromes ranged from 20% to 69%. Nerve decompression improved the severity of cold sensitivity in 5 of 6 studies where cold sensitivity was studied.

CONCLUSIONS

There is heterogenicity in the studies assessing cold sensitivity in nerve compression syndromes. Despite moderate prevalence in patients with carpal tunnel syndrome, cold sensitivity is understudied. Within the limitations of eligible studies reviewed, surgical decompression improved the severity of cold sensitivity in some studies.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Vibration Sensitivity Is Associated With Functional Balance After Unilateral Transtibial Amputation

Objectives

To evaluate differences in vibration perception thresholds between adults with transtibial amputation and age-matched adults without amputation and to examine associations between vibration perception thresholds and balance performance. We hypothesized that adults with transtibial amputation would demonstrate lower thresholds compared with adults without amputation and that lower thresholds would be associated with better functional balance.

Design

Prospective cross-sectional study.

Setting

National conference, clinical practice, and university laboratory.

Participants

Adults (N=34) with a nondysvascular, unilateral, transtibial amputation and 43 age-matched controls without amputation.

Interventions

Participants' vibration perception thresholds were evaluated bilaterally by applying a vibration stimulus to the midpatella and recording their verbal response to conscious perception of stimulus. Functional balance was assessed with the Berg Balance Scale and the Four Square Step Test.

Main Outcome Measures

Residual and sound limb (right and left for controls) vibration perception thresholds, Berg Balance Scale, and Four Square Step Test.

Results

For participants with transtibial amputation and controls, there were no significant between-group (P=.921) or interlimb (P=.540) differences in vibration perception thresholds. Overall, robust regression models explained 35.1% and 19.3% variance in Berg Balance Scale scores and Four Square Step Test times, respectively. Among adults with transtibial amputation, vibration perception thresholds were negatively associated with Berg Balance Scale scores (P=.009) and positively associated with Four Square Step Test times (P=.048). Among controls, average vibration perception thresholds were not significantly associated with functional balance (P>.050).

Conclusions

Adults with nondysvascular, transtibial-level amputation demonstrated similar vibration detection compared with adults with intact limbs, indicating that vibration detection is preserved in the amputated region postamputation. These findings suggest a unique relationship between vibration perception and functional balance post-transtibial amputation.

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.

Influence of centrally mediated symptoms on functional outcomes after carpal tunnel release

Patients with carpal tunnel syndrome (CTS) often show bilaterally increased pain sensitivity and widespread symptoms. We evaluated the influence of centrally mediated symptoms on functional outcomes of carpal tunnel release (CTR). A total of 120 patients with surgically treated CTS were enrolled. Centrally mediated symptoms were preoperatively measured by administering a self-reported central sensitization inventory (CSI) questionnaire and peripheral sensitization was measured by assessing patient's pressure pain thresholds (PPT) in the forearm. Boston Carpal Tunnel Questionnaires (BCTQ) were assessed preoperatively and postoperatively at 3 and 12 months. CSI scores slightly correlated with symptom duration and moderately correlated with preoperative BCTQ scores, while PPT slightly correlated with the BCTQ scores. At 3 months, BCTQ symptom and function scores moderately correlated with lower PPTs and higher CSI scores. At 12 months, only severe electrophysiological grade was associated with BCTQ function scores. Multivariable analysis revealed that preoperative PPT, CSI, and female gender were associated with BCTQ scores at 3 months; these factors failed to be associated for 12-month outcomes. Centrally mediated symptoms measured by CSI and peripheral sensitization measured by PPTs correlated with symptom severity and duration. They were associated with poorer functional outcomes after CTR up to 3 months. However, they did not show persistent effects in the long term.

Carpal tunnel syndrome: just a peripheral neuropathy?

Carpal tunnel syndrome (CTS) is considered just a peripheral neuropathy of the upper extremity associated to the compression of the median nerve. There is evidence suggesting the presence of complex sensitization mechanisms in CTS. These processes are manifested by symptoms in extra-median regions and the presence of bilateral sensory and motor impairments. These sensory and motor changes are not associated to electrodiagnostic findings. The presence of sensitization mechanisms suggests that CTS should not be considered just as a peripheral neuropathy. The presence of altered nociceptive gain processing should be considered for therapeutic management of CTS by considering the application of therapeutic interventions that modulate nociceptive barrage into the CNS.

Carpal tunnel syndrome impairs index finger responses to unpredictable perturbations

The fine-tuning of digit forces to object properties can be disrupted by carpal tunnel syndrome (CTS). CTS' effects on hand function have mainly been investigated using predictable manipulation tasks; however, unpredictable perturbations are commonly encountered during manual tasks, presenting situations which may be more challenging to CTS patients given their hand impairments. The purpose of this study was to investigate muscle and force responses of the index finger to unpredictable perturbations in patients with CTS. Nine CTS patients and nine asymptomatic controls were instructed to stop the movement of a sliding plate by increasing index finger force following an unexpected perturbation. The electrical activity of the first dorsal interosseous muscle and forces exerted by the index finger were recorded. CTS patients demonstrated 20.9% greater muscle response latency and 12.0% greater force response latency compared to controls (p<0.05). The duration of plate sliding was significantly different between groups (p<0.05); the CTS group's duration was 142.2±5.8ms compared to the control group's duration of 133.1±8.4ms. Although CTS patients had increased muscle and force response durations comparatively, these differences were not statistically significant. Findings from this study suggest CTS-induced sensorimotor deficits interfere with accurate detection, processing and response to unpredictable perturbations. These deficits could be accounted for at multiple levels of the peripheral and central nervous systems. Delayed and decreased responses may indicate inefficient object manipulation by CTS patients and may help to explain why CTS patients tend to drop objects.

Vibration sensibility of the median nerve in a population with chronic whiplash associated disorder: Intra- and inter-rater reliability study

Whiplash Associated Disorders (WAD) grade II are the most prevalent group of whiplash patients seen on a regular basis by musculoskeletal physiotherapists. Impairment of vibration sensibility may be an early indicator of nerve pathology and it has previously been demonstrated in individuals with chronic WAD symptoms utilising vibrameters. A less expensive option, such the tuning fork (TF) may assist with these measures, but research regarding its measurement properties is lacking.

OBJECTIVES

To investigate the intra- and inter-rater reliability of vibration sensibility of the median nerve in chronic WAD II (CWAD II).

METHODS

A double blinded, within day intra- and inter-rater reliability study was undertaken. A convenience sample of 26 individuals (8 males, 18 females, age mean 29.9 ± 10.0 years) with CWADII was recruited.

EXCLUSION CRITERIA

WAD I, III & indications of neuropathic pain. Vibration attenuation times were recorded from skin innervated by the median nerve (thenar eminence).

RESULTS

Descriptive statistics (mean scores) and reliability statistics [intraclass correlation coefficient (ICC2,1) and Bland and Altman limits of agreement] were undertaken with p = 0.05. Almost perfect intra-rater reliability (Intraclass Correlation Coefficiency (ICC): 0.972-0.955) and inter-rater reliability (ICC: 0.983) were identified. Confidence Intervals (CI) for inter-rater reliability were 95% CI: -1.461 to -0.056.

CONCLUSIONS

Almost perfect reliability scores across intra- and inter-rater reliability were found. This provides evidence that, with a standardised testing protocol the TF can be a highly reliable means of vibration sensibility testing. Future studies assessing the validity of the TF in different WAD populations may provide further information about the usefulness of this protocol.

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.

The construct validity and responsiveness of sensory tests in patients with carpal tunnel syndrome

Background and Purpose :

Sensory evaluation is fundamental to evaluation of patients with Carpal Tunnel Syndrome (CTS). The purpose of this study was to determine the construct validity and responsiveness for sensory threshold tests in patients with CTS.

Methods :

Sixty-three patients diagnosed with CTS were evaluated prior to orthotic intervention and again at follow up at 6 and 12 weeks. Sensory tests included touch threshold PSSD (Pressure Specified Sensory Device) and vibration threshold (Vibrometer). Construct validity was assessed by comparing sensory tests to hand function, and dexterity testing using Spearman rho (r_s). Patients were classified as either responders or non-responders to orthotic intervention based on the change score of the Symptom Severity Scale (SSS) of 0.5. Responsiveness of the sensory tools was measured using ROC (receiver operating characteristic) curves, SRM (Standardized Response Mean), and ES (Effect Sizes).

Results :

The PSSD had low to moderate correlations (r_s ≤ 0.32) while Vibrometer scores had moderate correlations (r_s = 0.36 - 0.41) with dexterity scores. The Clinically Important Difference (CID) for the PSSD was estimated at 0.15 g/mm² but was not discriminative. The Vibrometer demonstrated moderate responsiveness, with a SRM = 0.61 and an ES = 0.46 among responders. The PSSD had a SRM = 0.09 and an ES = 0.08 and showed low responsiveness for patients with a clinically important improvement in symptoms.

Conclusion :

Measurement properties suggest that the Vibrometer was preferable to the PSSD because it was more correlated to hand function, and was more responsive. Clinicians may choose use the Vibrometer opposed to the PSSD for determining important change in sensation after orthotic intervention.

Functional deficits in carpal tunnel syndrome reflect reorganization of primary somatosensory cortex

Carpal tunnel syndrome, a median nerve entrapment neuropathy, is characterized by sensorimotor deficits. Recent reports have shown that this syndrome is also characterized by functional and structural neuroplasticity in the primary somatosensory cortex of the brain. However, the linkage between this neuroplasticity and the functional deficits in carpal tunnel syndrome is unknown. Sixty-three subjects with carpal tunnel syndrome aged 20-60 years and 28 age- and sex-matched healthy control subjects were evaluated with event-related functional magnetic resonance imaging at 3 T while vibrotactile stimulation was delivered to median nerve innervated (second and third) and ulnar nerve innervated (fifth) digits. For each subject, the interdigit cortical separation distance for each digit's contralateral primary somatosensory cortex representation was assessed. We also evaluated fine motor skill performance using a previously validated psychomotor performance test (maximum voluntary contraction and visuomotor pinch/release testing) and tactile discrimination capacity using a four-finger forced choice response test. These biobehavioural and clinical metrics were evaluated and correlated with the second/third interdigit cortical separation distance. Compared with healthy control subjects, subjects with carpal tunnel syndrome demonstrated reduced second/third interdigit cortical separation distance (P < 0.05) in contralateral primary somatosensory cortex, corroborating our previous preliminary multi-modal neuroimaging findings. For psychomotor performance testing, subjects with carpal tunnel syndrome demonstrated reduced maximum voluntary contraction pinch strength (P < 0.01) and a reduced number of pinch/release cycles per second (P < 0.05). Additionally, for four-finger forced-choice testing, subjects with carpal tunnel syndrome demonstrated greater response time (P < 0.05), and reduced sensory discrimination accuracy (P < 0.001) for median nerve, but not ulnar nerve, innervated digits. Moreover, the second/third interdigit cortical separation distance was negatively correlated with paraesthesia severity (r = -0.31, P < 0.05), and number of pinch/release cycles (r = -0.31, P < 0.05), and positively correlated with the second and third digit sensory discrimination accuracy (r = 0.50, P < 0.05). Therefore, reduced second/third interdigit cortical separation distance in contralateral primary somatosensory cortex was associated with worse symptomatology (particularly paraesthesia), reduced fine motor skill performance, and worse sensory discrimination accuracy for median nerve innervated digits. In conclusion, primary somatosensory cortex neuroplasticity for median nerve innervated digits in carpal tunnel syndrome is indeed maladaptive and underlies the functional deficits seen in these patients.

Increased pain sensitivity is not associated with electrodiagnostic findings in women with carpal tunnel syndrome

OBJECTIVE

To determine the differences in widespread pressure pain and thermal hypersensitivity in women with minimal, moderate, and severe carpal tunnel syndrome (CTS) and healthy controls.

METHODS

A total of 72 women with CTS (19 with minimal, 18 with moderate, and 35 with severe) and 19 healthy age-matched women participated. Pressure pain thresholds were bilaterally assessed over the median, ulnar, and radial nerves, the C5 to C6 zygapophyseal joint, the carpal tunnel, and the tibialis anterior muscle. In addition, warm and cold detection thresholds and heat and cold pain thresholds were bilaterally assessed over the carpal tunnel and the thenar eminence. All outcome parameters were assessed by an assessor blinded to the participant's condition.

RESULTS

No significant differences in pain parameters among patients with minimal, moderate, and severe CTS were found. The results showed that PPT were significantly decreased bilaterally over the median, ulnar, and radial nerve trunks, the carpal tunnel, C5 to C6 zygapophyseal joint, and the tibialis anterior muscle in patients with minimal, moderate, or severe CTS as compared with healthy controls (all, P<0.001). In addition, patients with CTS also showed lower heat pain threshold and reduced cold pain threshold compared with controls (P<0.001). No significant sensory differences between minimal, moderate, or severe CTS were found.

CONCLUSIONS

The similar widespread pressure and thermal hypersensitivity in patients with minimal, moderate, or severe CTS and pain intensity suggests that increased pain sensitivity is not related to electrodiagnostic findings.

Specific mechanical pain hypersensitivity over peripheral nerve trunks in women with either unilateral epicondylalgia or carpal tunnel syndrome

STUDY DESIGN

Case-control study with blinded examiner.

OBJECTIVE

To investigate if pressure pain sensitivity is related to specific nerve trunks in the upper extremity of patients with either unilateral lateral epicondylalgia (LE) or carpal tunnel syndrome (CTS).

BACKGROUND

In the clinical setting, patients with LE tend to exhibit radial nerve trunk tenderness, whereas patients with CTS exhibit median nerve tenderness. No studies have investigated if specific nerve pressure pain hypersensitivity exists in patients with either LE or CTS.

METHODS

Sixteen women with unilateral LE (mean±SD age, 43±7 years), 17 women with unilateral CTS (43±6 years), and 17 healthy women (43±6 years) were included in this study. Pressure pain thresholds (PPT) were bilaterally assessed over the median, ulnar, and radial nerve trunks, as well as over the C5-6 zygapophyseal joints, by an examiner blinded to the subjectsí condition. A mixed-model analysis of variance was used to evaluate differences in PPT among groups (LE, CTS, or controls) and between sides (affected/nonaffected or dominant/nondominant).

RESULTS

The individuals in both the LE and CTS groups demonstrated lower PPT bilaterally over the median (group, P<.001; side, P=.437), radial (group, P<.001; side, P=.556), and ulnar (group, P<.001; side, P=.938) nerve trunks as compared to controls. Additionally, radial (P<.001) and ulnar (P=.005) nerves were more sensitive bilaterally in patients with LE than in patients with CTS. The median nerve was more sensitive bilaterally in patients with CTS than patients with LE (P=.002). Lower PPT over the cervical spine (group, P<.001; side, P=.233) were found bilaterally in both the LE and CTS groups. Further, patients with CTS exhibited lower cervical PPT than patients with LE (P<.001). PPT was negatively correlated with both pain intensity and duration of symptoms in both the LE and CTS groups (P<.001).

CONCLUSIONS

Bilateral mechanical nerve pain hypersensitivity is related to specific and particular nerve trunks in women with either unilateral LE or CTS. Our results suggest the presence of central and peripheral sensitization mechanisms in individuals with either LE or CTS.

Central sensitization does not identify patients with carpal tunnel syndrome who are likely to achieve short-term success with physical therapy

The aim of the current study was to identify whether hyperexcitability of the central nervous system is a prognostic factor for individuals with carpal tunnel syndrome (CTS) likely to experience rapid and clinical self-reported improvement following a physical therapy program including soft tissue mobilization and nerve slider neurodynamic interventions. Women presenting with clinical and electrophysiological findings of CTS were involved in a prospective single-arm trial. Participants underwent a standardized examination and then a physical therapy session. The physical therapy sessions included both soft tissue mobilization directed at the anatomical sites of potential median nerve entrapment and a passive nerve slider neurodynamic technique targeted to the median nerve. Pressure pain thresholds (PPT) over the median, radial and ulnar nerves, C5-C6 zygapophyseal joint, carpal tunnel and tibialis anterior muscle were assessed bilaterally. Additionally, thermal detection and pain thresholds were measured over the carpal tunnel and thenar eminence bilaterally to evaluate central nervous system excitability. Subjects were classified as responders (having achieved a successful outcome) or non-responders based on self-perceived recovery. Variables were entered into a stepwise logistic regression model to determine the most accurate variables for determining prognosis. Data from 72 women were included in the analysis, of which 35 experienced a successful outcome (48.6%). Three variables including PPT over the C5-C6 joint affected side <137 kPa, HPT carpal tunnel affected side <39.6º and general health >66 points were identified. If 2 out of 3 variables were present (LR + 14.8), the likelihood of success increased from 48.6 to 93.3%. We identified 3 factors that may be associated with a rapid clinical response to both soft tissue mobilization and nerve slider neurodynamic techniques targeted to the median nerve in women presenting with CTS. Our results support that widespread central sensitization may not be present in women with CTS who are likely to achieve a successful outcome with physical therapy. Future studies are now necessary to validate these findings.

Chronic pain has a small influence and mood has no influence on vibrotactile perception thresholds among working women

In chronic diffuse upper limb pain physical abnormalities are usually absent. The aims of our study were to investigate: (1) the function of somatosensory pathways and (2) the influence of mood on vibration perception. Measurements were made of: (i) vibrotactile perception thresholds (VPTs) and nerve conduction in working women with (n = 35) and without (n = 65) chronic diffuse upper limb pain, and (ii) perceived stress and energy using a two-dimensional mood adjective checklist. The groups did not differ in any nerve conduction measurements. Women with chronic pain had raised VPTs in the radial and ulnar nerve areas, but not in the median nerve area. Neither perceived stress nor energy appeared to influence the VPT. Increases of VPTs in chronic diffuse upper limb pain may be due to peripheral nerve affliction, but our findings support the idea that they may also be secondary to pain and may be related to a central nervous mechanism.

An investigation of somatosensory profiles in work related upper limb disorders: a case-control observational study protocol

Background

Work related upper limb disorders constitute 45% of all occupational diseases and are a significant public health problem. A subgroup, non specific arm pain (NSAP), remains elusive in terms of understanding its pathophysiological mechanisms with its diagnosis based on the absence of specific clinical findings. One commonly proposed theory is that a neural tissue disorder is the primary dysfunction in NSAP and findings from previous studies lend some support to this theory. However, it is not clear if changes identified are simply a consequence of ongoing pain rather than due to specific neural changes. The presence of neuropathic pain has been investigated in several other musculoskeletal conditions but currently, there is no specific diagnostic tool or gold standard which permits an unequivocal diagnosis of neuropathic pain. The purpose of this study is to further describe the somatosensory profiles in patients with NSAP and to compare these profiles to a group of patients with MRI confirmed cervical radiculopathy who have been previously classified as having neuropathic pain.

Methods/Design

Three groups of participants will be investigated: Groups 1 and 2 will be office workers with either NSAP or cervical radiculopathy and Group 3 will be a control group of non office workers without upper limb pain. Participants will undergo a clinical assessment, pain questionnaires (LANSS, Short Form McGill, DASH and TSK) and quantitative sensory testing comprising thermal detection and pain thresholds, vibration thresholds and pressure pain thresholds.

Discussion

The spectrum of clinically suspected neuropathic pain ranges from more obvious conditions such as trigeminal neuralgia to those with vague signs of nerve disorder such as NSAP. A thorough description of the somatosensory profiles of NSAP patients and a comparison with a more defined group of patients with evidence of neuropathic pain will help in the understanding of underlying neurophysiology in NSAP and may influence future classification and intervention studies relating to this condition.

Regional pain syndrome: clinical characteristics, mechanisms and management

Regional soft-tissue complaints are commonplace, and they usually relate to a disease process, such as strain, inflammation or degeneration of a muscle, tendon or related muscle-tendon unit. The clinical features and investigations of the causative processes of these complaints are characteristic, and outcomes to treatments are usually predictable and satisfactory. Regional pain syndromes are different: these syndromes present with regional pain and tenderness, and other sensory symptoms unaccounted for by a simple musculoskeletal mechanistic explanation. Approved classification criteria for regional pain syndromes are lacking, and these syndromes are poorly understood and frequently misdiagnosed. Regional pain syndromes often occur after injury and overlap extensively with other musculoskeletal pain syndromes, in terms of clinical signs and symptoms. The clinician and patient are often confused about the nature of the problem and routine treatments directed to putative tissue damage will fail. Review of the epidemiology of regional pain syndromes combined with knowledge of other similar pain syndromes has enabled an evolving understanding of the condition. The musculoskeletal and central nervous systems both contribute to regional pain syndromes, through spine-related pain mechanisms and central sensitization, respectively. The patient's emotional state, particularly the effect on pain modulation, links these two systems.