Ultrasonographic Median Nerve Cross-Sectional Area and Clinical, Electrodiagnostic, and Laboratory Biomarkers in Electrodiagnostically Confirmed Carpal Tunnel Syndrome: A Single-Center Correlational Study

<b>Objectives:</b> This study aimed to evaluate the relationship between the median nerve cross-sectional area (CSA, mm²) and clinical findings, blood test results, and electrodiagnostic (EDX) measurements in patients with carpal tunnel syndrome (CTS). <b>Methods:</b> This cross-sectional study included 62 patients (111 hands). The median nerve CSA was assessed using ultrasound (US). The clinical assessment included symptom duration, symptom severity, the Boston Carpal Tunnel Questionnaire (BCTQ), and physical examination. Patient-level analyses used the CSA of the most symptomatic hand for clinical and laboratory variables (<i>n</i> = 62 patients). Hand-level EDX analyses accounted for within-patient clustering by reporting right and left hands separately. Associations were summarized with Spearman's ρ and 95% confidence intervals (CIs); multiplicity was addressed using Benjamini-Hochberg false discovery rate (FDR). EDX units: latency ms, amplitude mV/µV, and velocity m/s. <b>Results:</b> CSA was not associated with global symptom burden (Visual Analog Scale; BCTQ). No laboratory marker remained significant after FDR across the full panel. By contrast, CSA correlated with EDX impairment at the hand level with low-to-moderate effect sizes; for example, distal motor latency was positively associated with CSA on the right (ρ = 0.557, 95% CI 0.334-0.733) and left (ρ = 0.318, 95% CI 0.022-0.578). CSA also correlated positively with CTS EDX severity (right: ρ = 0.449, 95% CI 0.223-0.646; left: ρ = 0.354, 95% CI 0.071-0.609). <b>Conclusions:</b> Ultrasonographic CSA was associated with electrophysiologic impairment and was not associated with overall symptom burden; laboratory signals did not survive FDR control. Accordingly, CSA may serve as a complementary morphologic adjunct to clinical assessment and EDX, with limited utility as a stand-alone severity metric.