Role of Median Nerve Cross-Sectional Area in the Diagnosis of Carpal Tunnel Syndrome

Carpal tunnel syndrome (CTS) is the most common chronic neuropathy of the upper limb, characterized by compression of the median nerve within the carpal tunnel. It typically results from repetitive hand movements or trauma and leads to pain, numbness, and weakness, making it a significant occupational health concern. Increased intracarpal pressure causes venous stasis, edema, and ischemic damage, which slow nerve conduction and are detectable through electrodiagnostic (EDX) studies. Recently, ultrasonographic measurement of the median nerve cross-sectional area (CSA) has been proposed as a noninvasive diagnostic option. This study aimed to evaluate the diagnostic accuracy of ultrasound-based CSA measurement compared with EDX findings in CTS patients. The research was conducted at Al-Imamain Al-Kadhimain Medical City in Baghdad from November 2024 to March 2025 and included 100 patients (200 hands). All individuals underwent both EDX and high-resolution ultrasonography using a 5–13 MHz linear probe, with CSA calculated by the direct tracing method. CTS was confirmed in 102 hands (51%). Affected hands demonstrated significantly prolonged distal motor and sensory latencies, reduced amplitudes, and lower conduction velocities (p < 0.001). Mean CSA was significantly larger in CTS hands (13.75 ± 3.95 mm²) than in non-CTS hands (10.15 ± 3.33 mm², p < 0.001). ROC analysis produced an AUC of 0.776 and an optimal cutoff of 11.5 mm² (72% sensitivity, 76% specificity). CSA also increased with CTS severity. Moderate accuracy was observed when differentiating mild from moderate CTS at a 12.5 mm² cutoff, and moderate from severe CTS. In conclusion, median nerve CSA measurement by ultrasound is a reliable, noninvasive, and rapid tool for diagnosing and grading CTS, complementing EDX assessment.