Correlation Between Ultrasound and Nerve Conduction Study Findings in Evaluating Carpal Tunnel Syndrome

TL;DR

This study compares ultrasound and nerve conduction tests for diagnosing carpal tunnel syndrome, finding them to be moderately consistent in severity grading.

Contribution

The study provides new evidence on the correlation and agreement between ultrasound and nerve conduction studies for evaluating carpal tunnel syndrome severity.

Findings

Ultrasound cross-sectional area correlated strongly with sensory and motor nerve conduction parameters.

Ultrasound and nerve conduction studies showed moderate agreement in grading carpal tunnel syndrome severity.

Ultrasound is proposed as a reliable alternative in settings where nerve conduction studies are not feasible.

Abstract

Background

Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy, caused by median nerve compression within the carpal tunnel, leading to pain, numbness, and functional impairment. Nerve conduction studies (NCS) remain the diagnostic gold standard, while ultrasonography (US) offers a non-invasive complementary modality. This study evaluated the correlation and agreement between US and NCS in CTS.

Methodology

In this cross-sectional study conducted at Dhaka Medical College Hospital from August 2021 to September 2022, 48 symptomatic patients (one hand per patient) underwent standardized NCS (motor distal latency (mDL), amplitude (mAMP), velocity (mCV), sensory distal latency (sDL), amplitude (sAMP), velocity (sCV)) and US at the inlet using a 16-MHz linear probe, with the sonographer blinded to clinical and NCS findings. CTS severity was graded by Bland’s scale (NCS) and cross‑sectional area (CSA) thresholds (US). Spearman correlation assessed associations and Cohen’s kappa quantified inter-modality agreement, with significance set at p-values <0.05.

Results

According to the NCS, 4 (8.3%) patients were normal, 12 (25.0%) were mild, 21 (43.7%) were moderate, and 11 (22.9%) were severe. CSA was positively correlated with mDL (r = 0.667, p < 0.001) and sDL (r = 0.670, p < 0.001) and negatively correlated with sAMP (r = -0.624, p < 0.001) and sCV (r = -0.536, p < 0.001); correlations with mAMP and mCV were not significant. The US and NCS grades were strongly correlated (r = 0.810, p < 0.001). Overall agreement between US and NCS severity was moderate (κ = 0.60, p < 0.001).

Conclusions

US appears to be a practical and reliable adjunct to NCS for evaluating and grading CTS, particularly in resource-limited settings or when NCS are not readily feasible. Larger multicenter studies are needed to further validate its role and refine diagnostic thresholds.

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