T2 relaxometry and cross-sectional area of the median nerve as quantitative MRI biomarkers in carpal tunnel syndrome

Beatriz Elias-Perez, Department of Magnetic Resonance Imaging, Hospital Angeles Lomas, Huixquilucan, State of Mexico, Mexico;
Arturo Hernandez-Medina, Department of Magnetic Resonance, Hospital Angeles Lomas, Huixquilucan, State of Mexico; Biomedical Engineering Area, Faculty of Engineering, Universidad Autonoma de Queretaro, Queretaro, Qro. Mexico;
Juan J. Mariño-Arevalo, Department of Magnetic Resonance Imaging, Hospital Angeles Lomas, Huixquilucan, State of Mexico, Mexico;

Introduction: T2 relaxometry and cross-sectional area (CSA) values of the median nerve, assessed by magnetic resonance imaging (MRI) at various levels of the carpal tunnel have not been sufficiently evaluated in patients with carpal tunnel syndrome (CTS). This study aimed to assess the CSA and T2 relaxometry values of the median nerve at the proximal and distal levels of the carpal tunnel using MRI in Mexican patients with CTS. Material and methods: This case series included patients clinically diagnosed with CTS. Wrist 3.0T MRI scans were performed, and CSA and T2 relaxometry maps of the median nerve were obtained at the proximal (pisiform bone) and distal (hook of hamate bone) levels of the carpal tunnel. Age, weight, height, body mass index (BMI), and clinical severity and functional scores of CTS were recorded. Results: Twelve wrists from 10 patients with CTS were included. The mean CSA of the median nerve at the proximal level (12.7 ± 2.1 mm2) was significantly higher than at the distal level (9.7 ± 1.9 mm2; p < 0.001), with a large effect size (Cohen’s d = 1.43). The mean T2 relaxation time was higher at the proximal level (64.7 ± 7.4 ms) than at the distal level (59.6 ± 7.8 ms; p = 0.034), with a moderate effect size (Cohen’s d = 0.70). No significant correlations were observed between anthropometric measures and CSA, T2 relaxometry, or CTS clinical and functional scores. Conclusion: T2 relaxometry and CSA values of the median nerve on MRI showed regional variation, with significantly higher values at the proximal carpal tunnel level in patients with CTS. T2 relaxometry values at the proximal level were abnormally elevated compared with reference values from healthy Mexican subjects. T2 relaxometry and CSA are complementary biomarkers for assessing median nerve damage in CTS.

Keywords: Magnetic resonance imaging. Relaxometry. Median nerve. Carpal tunnel syndrome.