Laser evoked potentials in carpal tunnel syndrome

Ultrasound improves motor distal latency on patients with carpal tunnel syndrome: systematic review and meta-analysis

INTRODUCTION

Is the application of ultrasound effective on pain, the severity of the symptoms, physical function, strength, and neurophysiological parameters of the median nerve conduction in patients with carpal tunnel syndrome?

EVIDENCE ACQUISITION

A systematic review and meta-analysis of randomized controlled trials was performed by using a structured search strategy in Scopus, CINAHL, Web of Science and PEDro databases. All the primary studies included samples with carpal tunnel syndrome treated by: ultrasound versus no treatment, therapeutic ultrasound versus sham ultrasound, ultrasound and usual care versus usual care, or ultrasound and other intervention versus the same intervention. The outcomes measures registered were pain, severity of symptoms, function, strength, and neurophysiological parameters (motor distal latency and sensory distal latency) of the median nerve. Methodological quality was evaluated by PEdro Scale.

EVIDENCE SYNTHESIS

Ten clinical trials met the inclusion criteria for the systematic review. Eight trials were meta-analyzed, which included a total of 2069 patients with carpal tunnel syndrome. The methodological quality of the included studies ranged among limited (5 trials), moderate (3 trials), and high (2 trials). In one of the electrophysiological parameters (motor distal latency), a significant difference between groups after the use of ultrasound was observed (MD=-0.10; fixed 95% CI=-0.20, -0.01; P=0.04). No significant differences between groups were observed at post-treatment for pain (P=0.29), severity of symptoms (P=0.99), function (P=0.54), strength (P=0.27) and for the rest of the electrophysiological parameters evaluated (P>0.05).

CONCLUSIONS

The use of ultrasound on patients with carpal tunnel syndrome seems to improve motor distal latency. This finding implies a partial improvement at the neurophysiological level, representing a reduction in the grade of clinical severity. Additional clinical trials with a high methodological quality are needed to investigate the doses at which ultrasound are most effective.

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.

Peripheral nerve injuries, pain, and neuroplasticity

INTRODUCTION

Peripheral nerve injuries (PNIs) cause both structural and functional brain changes that may be associated with significant sensorimotor abnormalities and pain.

PURPOSE OF THE STUDY

The aim of this narrative review is to provide hand therapists an overview of PNI-induced neuroplasticity and to explain how the brain changes following PNI, repair, and during rehabilitation.

METHODS

Toward this goal, we review key aspects of neuroplasticity and neuroimaging and discuss sensory testing techniques used to study neuroplasticity in PNI patients.

RESULTS

We describe the specific brain changes that occur during the repair and recovery process of both traumatic (eg, transection) and nontraumatic (eg, compression) nerve injuries. We also explain how these changes contribute to common symptoms including hypoesthesia, hyperalgesia, cold sensitivity, and chronic neurogenic pain. In addition, we describe how maladaptive neuroplasticity as well as psychological and personality characteristics impacts treatment outcome.

DISCUSSION AND CONCLUSION

Greater understanding of the brain's contribution to symptoms in recovering PNI patients could help guide rehabilitation strategies and inform the development of novel techniques to counteract these maladaptive brain changes and ultimately improve outcomes.

Bilaterally prolonged latencies of pain-related evoked potentials in peripheral nerve injuries

OBJECTIVE

Cross-sectional study to test the applicability of pain-related evoked potentials (PREP) for the diagnosis of peripheral nerve injuries (PNI).

INTRODUCTION

Patients with generalized polyneuropathies show prolonged latencies and decreased amplitudes of PREP indicating an impairment of A-delta fibers. Although these fibers are frequently affected in PNI, it is unclear, if PREP-testing detects PNI comparable to Nerve Conduction Studies (NCS).

METHODS

23 patients with PNI of one upper limb underwent bilateral PREP-testing (using concentric surface electrodes) and NCS. 41 healthy controls underwent PREP-testing only. We determined pain thresholds, N1-latencies and N1P1-amplitudes of PREP and analyzed them for group and side-to-side differences. Small-fiber function was evaluated using thermal detection thresholds of Quantitative Sensory Testing (QST). N1-latencies above a cut-off calculated by ROC-analysis were defined as abnormal in order to compare detection rates of PREP and NCS.

RESULTS

Patients with PNI showed bilaterally prolonged N1-latencies (ipsilateral: 167.0 ± 40.7 ms vs. 141.2 ± 20.5 ms / contralateral: 160.0 ± 41.0 ms vs. 140.2 ± 23.9 ms) without a significant side-to-side difference. Pain thresholds were increased on the affected side only (4.6 ± 5.2 mA vs. 2.4 ± 1.4 mA (controls)). N1P1-amplitudes did not differ between patients and controls. 7 (32%) patients showed prolonged N1-latencies (>176 ms) of PREP. NCS were abnormal in 16 (73%) cases. 13 (59%) patients showed thermal hypoesthesia in QST.

CONCLUSION

Contrary to our expectations, we found bilaterally prolonged N1-latencies and normal N1P1-amplitudes in patients with PNI. Our findings support the hypothesis of a bilateral generation of PREP and indicate that PREP are not suitable for the diagnosis of PNI.

Relationship between electrodiagnostic severity and neuropathic pain assessed by the LANSS pain scale in carpal tunnel syndrome

OBJECTIVE

The aim of the study was to investigate the relationship between the presence of neuropathic pain assessed by the Leeds Assessment of Neuropathic Symptoms and Signs (LANSS) scale and electrophysiological findings in patients with carpal tunnel syndrome (CTS).

METHODS

We studied 124 hands with idiopathic CTS with pain complaints involving hand and wrist. All hands were assessed by the LANSS with which a score of 12 or more is defined as pain dominated by neuropathic mechanisms. These hands were assigned to minimal, mild, moderate, severe, or extreme severe groups according to the results of the median nerve conduction studies.

RESULTS

A LANSS score ≥ 12, suggestive of pain dominated by neuropathic mechanisms, was defined in 59 (47.6%) CTS hands. Pain intensity was significantly higher in CTS hands with a LANSS score ≥ 12 (P < 0.001). Among electrophysiological findings, compound muscle action potential amplitude was significantly lower in hands with a LANSS score ≥ 12 compared with hands with a LANSS score < 12 (P = 0.020). Severity of CTS was not significantly different between LANSS ≥ 12 and LANSS < 12 groups. Electrophysiological severity was significantly higher in CTS hands with evoked pain (P = 0.005) and allodynia (P < 0.001) in LANSS subscore analysis.

CONCLUSION

We suggest that the presence of pain dominated by neuropathic mechanisms in CTS is not related to electrophysiological CTS severity. Neuropathic pain should be assessed carefully in patients with CTS, and an appropriate treatment plan should be chosen, taking into account the clinical and electrophysiological findings together with the true pain classification.

Evidences for antinociceptive effect of 17-α-hydroxyprogesterone caproate in carpal tunnel syndrome

Growing evidence of neuroprotective and analgesic effects by progesterone (PROG) has been obtained in experimental animal models of neuropathy. In this paper, we report the results of the first experimental study to test the efficacy of PROG in a human neuropathy. The effects of a local administration of 17-alpha-hydroxyprogesterone caproate (17HPC) has been studied in patients with carpal tunnel syndrome (CTS) and compared with those of a local administration of corticosteroid (CS) in a analogous CTS group. Sixteen women affected by mild CTS were selected. Clinical, electrophysiological and ultrasonographic data of the median nerve were quantified at 0 (pre-injection), 1 and 6 months after CS or 17HPC injection. One month after injection, both 17HPC and CS groups exhibited similar reduction in pain scores, whereas only the 17HPC-treated group still manifested symptoms relief 6 months after. Only in CS-treated patients, improvement of the clinical data correlated with ultrasonographic and electrophysiological changes of the median nerve. The present study indicates that intra-carpal injection with a long-acting PROG derivative is effective for relief of symptoms in CTS. This effect is apparently mediated by a mechanism distinct from that of the CS.

The genetic influence on the cortical processing of experimental pain and the moderating effect of pain status

BACKGROUND

Research suggests that the COMT Val(158)Met, BDNF Val(66)Met and OPRM1 A(118)G polymorphisms moderate the experience of pain. In order to obtain experimental confirmation and extension of findings, cortical processing of experimentally-induced pain was used.

METHOD

A sample of 78 individuals with chronic low back pain complaints and 37 healthy controls underwent EEG registration. Event-Related Potentials were measured in response to electrical nociceptive stimuli and moderation by COMT Val(158)Met, BDNF Val(66)Met and OPRM1 A(118)G polymorphisms was assessed.

RESULTS

Genetic variation did not have a direct effect on cortical processing of experimental pain. However, genetic effects (COMT Val(158)Met and BDNF Val(66)Met) on experimental pain were moderated by the presence of chronic pain. In the presence of chronic pain, the COMT Met allele and the BDNF Met allele augmented cortical pain processing, whilst reducing pain processing in pain-free controls. No significant effects were found concerning the OPRM1 A(118)G polymorphism.

CONCLUSIONS

The current study suggests that chronic experience of pain enhances genetic sensitivity to experimentally induced mildly painful stimuli, possibly through a process of epigenetic modification.

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

We explored the contribution of median nerve small (Aδ, C)-and large (Aβ)-fiber damage to the severity and topographic distribution of sensory symptoms in carpal tunnel syndrome (CTS) and the timing of fiber damage across CTS stages. We recruited 106 CTS patients. After selection, 49 patients were included. They underwent electrodiagnostic and quantitative sensory testing (QST) study and were asked on the severity of Boston Carpal Tunnel Questionnaire (BCTQ) Symptoms Severity Scale, daytime pain (DP), night pain and paresthesia, on the distribution of hand symptoms, and the presence of proximal symptoms. BCTQ Symptoms Severity Scale and DP severity was significantly correlated with Aδ-fiber damage. Small-fiber QST measures were impaired in electrodiagnostic-negative CTS patients and did not change across CTS neurographic stages. QST findings were not correlated to the topographical distribution of symptoms. Aδ-fiber damage contributes to CTS symptoms and in particular to DP. Night pain and paresthesia might be ascribed to ectopic fiber discharges secondary to median nerve enhanced mechanosensitivity. Small-fiber damage takes place earlier than large fiber. Median nerve fiber involvement does not directly contribute to extraterritorial symptoms spread. Our data may help understanding CTS pathophysiology and explain the well-known discrepancy between CTS symptoms and electrodiagnostic findings.

PERSPECTIVE

We explored the involvement of median nerve small and large fibers in carpal tunnel syndrome (CTS). We found a significant correlation between Aδ-fiber function and CTS symptoms. Small-fiber involvement took place in milder disease stages. These findings could help reconcile the discrepancy between CTS symptoms and electrodiagnostic data.

Ulnar nerve impairment at the wrist does not contribute to extramedian sensory symptoms in carpal tunnel syndrome

OBJECTIVE

Extramedian spread of sensory symptoms is frequent in carpal tunnel syndrome (CTS) but its mechanisms are unclear. We explored the possible role of subtle ulnar nerve abnormalities in the pathogenesis of extramedian symptoms.

METHODS

We recruited 350 CTS patients. After selection, 143 patients (225 hands) were included. The hand symptoms distribution was graded with a diagram into median (MED) and extramedian (EXTRAMED) pattern. We tested the correlation of ulnar nerve conduction measures with the distribution and the severity of symptoms involving the ulnar territory. The clinical significance of ulnar nerve conduction findings was explored with quantitative sensory testing (QST).

RESULTS

EXTRAMED distribution was found in 38.7% of hands. The ulnar neurographic measures were within normal values. Ulnar nerve sensory measures were significantly better in EXTRAMED vs MED hands and not significantly correlated to ulnar symptoms severity. Ulnar and median nerve sensory measures were significantly correlated. QST showed normal function of ulnar nerve alphabeta-fibers.

CONCLUSIONS

Ulnar nerve sensory abnormalities do not contribute to the spread of sensory symptoms into the ulnar territory.

SIGNIFICANCE

Our data favour the hypothesis that spinal and supraspinal neuroplastic changes may underlie extramedian spread of symptoms in CTS.