Relation between distal motor latency delay and sensory action potential absence of the median nerve in carpal tunnel syndrome

Electrophysiological characteristics of neuropathic pain model in mice and a technique to evaluate peripheral nerve damage in the sciatic nerve

Background

Experimental neuropathic pain (NP) models were developed from peripheral injuries and are widely used for pain research. However, previously published methods and outcomes in the evaluation of sciatic nerve dysfunction vary widely across each report. In this study, we established the electrophysiological analysis of sensory nerve action potentials (SNAPs) and compound motor action potentials (CMAPs) as objective methods for evaluating sciatic nerve dysfunction and revealed the electrophysiological characteristics of NP mice models.

Methods

We used male C57BL/6 J mice, C57BLKS/J lar- + Leprdb/+Leprdb (db/db) mice, and mouse models of paclitaxel-induced NP and spared nerve injury (SNI) surgery (10 mice in each group). For nerve conduction studies, we used evoked potential/electromyography apparatuses and bipolar electrodes as stimulating and recording electrodes for SNAPs and CMAPs. SNAPs were recorded from the sciatic nerve. For the distal motor latency and CMAPs amplitude measurements, we placed the cathode of the recording electrode on the gastrocnemius muscle.

Results

In electrophysiological assessments, the SNI model showed the most severe sensory disturbance in SNAP with allodynia in the sciatic nerve. The db/db model showed moderate sensory disturbance with allodynia, whereas the paclitaxel model showed slight sensory disturbance but also with allodynia. Only the SNI model showed significantly lower amplitudes of CMAPs than those of normal mice, whereas the paclitaxel and db/db models showed sensory disturbance but no loss of motor function.

Conclusions

We focused on the detailed methodology of electrophysiological assessment in experimental NP models. Our method of electrophysiological analysis of SNAPs and CMAPs of the sciatic nerve was well reflected in the pain withdrawal tests performed in each NP model and may be useful for future research of NP in experimental NP models.

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.