Ultrasonographic Findings of Mild and Very Mild Carpal Tunnel Syndrome

Objective: To assess the clinical usefulness of ultrasonography for the diagnosis of mild and very mild carpal tunnel syndrome. Method: Ultrasonographic evaluation was performed in 39 hands of 29 patients with mild and very mild carpal tunnel syndrome according to Bland's neurophysiologic grading scale. Controls included 41 hands of 34 subjects without electrophysiologic evidence of carpal tunnel syndrome. Ultrasonographic findings were evaluated quantitatively with regard to the cross-sectional area, the flattening ratio, the swelling ratio of the median nerve, and palmar displacement of the flexor retinaculum. The analysis of differences between controls and patients group were done by independent t-test. Cut-off values using receiver operation characteristic, were calculated. Results: Patients had significantly increased cross sectional area and flattening ratio of the median nerve at proximal carpal area, palmar displacement of the flexor retinaculum at proximal carpal area. A critical value of equal or higher to 8.5 mm(2) for cross-sectional area at the pisiform level showed a sensitivity 79.5%, a specificity of 95.1%, which had most diagnostic value compared with the value of cross-sectional area at the distal radius level, flattening ratio at the pisiform level and palmar displacement. Conclusion: Ultrasonography was useful in the diagnosis of mild and very mild carpal tunnel syndrome.