Association between electrodiagnosis and neuromuscular ultrasound in the diagnosis and assessment of severity of carpal tunnel syndrome

Background: Neuromuscular ultrasound plays an increasing role in diagnosing carpal tunnel syndrome (CTS). There are limited data supporting the correlation between the electrodiagnostic studies and ultrasound measurements in CTS. Objective: To assess the association between different electrodiagnostic severities and ultrasound measurements of the median nerve in CTS. Design: A retrospective cohort study. Setting: An academic tertiary care center. Patients: Patients 18 years or older evaluated with upper limb electrodiagnostic studies and neuromuscular ultrasound. Main outcome measurement: Ultrasound measurements of the median nerve cross-sectional area (CSA) at the wrist and the calculated wrist-to-forearm ratio (WFR) were compared with the electrodiagnostic severity (normal, mild, moderate, and severe). Mean analysis and analysis of variance test (alpha = 0.05) were performed to assess the association. Results: A total of 1359 limbs were identified. There was a statistically significant association between electrodiagnostic severity of CTS and median nerve CSA at the wrist (p < .001), as well as the WFR (p < .001). The mean median nerve CSA at the wrist and WFR were 7.01 +/- 2.06 mm(2) (95% CI: 6.80-7.20) and 1.24 +/- 0.36 (95% CI: 1.16-1.24) in electrodiagnostically normal median nerves, 10.47 +/- 2.82 mm(2) (95% CI: 10.25-10.75) and 2.06 +/- 0.67 (95% CI: 2.04-2.16) in electrodiagnostically mild CTS, 12.95 +/- 4.74 mm(2) (95% CI: 12.41-13.59) and 2.49 +/- 1.04 (95% CI: 2.37, 2.63) in electrodiagnostically moderate CTS, and 14.69 +/- 5.38 mm2 (95% CI: 13.95-15.44) and 2.71 +/- 1.02 (95% CI: 2.56-2.84) in electrodiagnostically severe CTS, respectively. Conclusion: This study suggests a direct association between electrodiagnostic severity and ultrasound measurements of the median nerve in patients with suspected CTS.