Strain and Morphological Changes of Median Nerve After Carpal Tunnel Release

Characterization of the changes of ultrasound parameters after carpal tunnel release may be useful for clarifying the effectiveness or the recovery process of the carpal tunnel syndrome treatment. We evaluated strain and morphological changes of the median nerve before and after carpal tunnel release in carpal tunnel syndrome patients.

Twenty-two wrists of 20 idiopathic carpal tunnel syndrome patients who underwent open carpal tunnel release were evaluated by ultrasound. Cross-sectional images of the median nerve were obtained at the proximal carpal tunnel. The cross-sectional area, perimeter, aspect ratio of the minimum enclosing rectangle, and strain of the median nerve were measured and compared before and after carpal tunnel release. According to the patient's recovery, the areas under the receiver operating characteristic curves (AUCs) were compared among the parameters.

After carpal tunnel release, the area and perimeter significantly decreased, and the strain significantly increased compared with before carpal tunnel release. There were no significant changes in the aspect ratio after carpal tunnel release. The AUCs were 0.663, 0.643, 0.543, and 0.731 for the area, perimeter, aspect ratio, and strain, respectively.

Significant decreases in median nerve area and perimeter as well as significant increases in median nerve strain were observed after carpal tunnel release. The results of this study may be useful when considering how the median nerve recovers after carpal tunnel release.