# Median Nerve Diameter Ratio on Ultrasound as a Complementary Tool to Electrodiagnostic Testing in Carpal Tunnel Syndrome

## TL;DR

This study explores whether ultrasound measurements of the median nerve can complement electrodiagnostic tests for diagnosing carpal tunnel syndrome.

## Contribution

The study evaluates the correlation between median nerve diameter ratio and electrodiagnostic parameters in carpal tunnel syndrome patients.

## Key findings

- No significant correlation was found between carpal tunnel ratio and distal motor latency.
- A weak, non-significant correlation was observed between carpal tunnel ratio and sensory nerve conduction velocity.

## Abstract

Background: Carpal tunnel syndrome is a common entrapment neuropathy of the upper limb that has a significant clinical and socioeconomic impact. Sonographic short-axis measurement of the median nerve cross-sectional area is a well-established complement to clinical examination and neurography. This study aimed to evaluate the correlation between the median nerve diameter ratio, distal motor latency, and sensory nerve conduction velocity. Methods: A total of 74 patients (94 hands and 93 evaluations) with carpal tunnel syndrome were examined. Ultrasound was performed using a Siemens Acuson X300 with a 10 MHz linear probe. Median nerve diameters proximal and within the carpal tunnel were measured in a longitudinal scan. The carpal tunnel ratio (proximal diameter/intratunnel diameter) was then calculated and correlated with distal motor latency. Results: No significant correlation was found between distal motor latency and the carpal tunnel ratio (r = 0.018, p = 0.8655). However, a weak, non-significant positive correlation was observed between sensory nerve conduction velocity and carpal tunnel ratio (r = 0.238, p = 0.326). Conclusions: Ultrasound cannot replace electrodiagnostic testing. In this cohort, no statistically significant association was observed between the carpal tunnel ratio and distal motor latency. While our findings do not support the use of this ultrasound parameter as a standalone diagnostic measure, sonographic assessment of the median nerve may still provide complementary information in selected clinical contexts.