Effect of median nerve mobilization in subjects with carpal tunnel syndrome: nerve mechanical properties and clinical symptoms

Background and Purpose：Carpal tunnel syndrome (CTS) is one of the most common compression neuropathy in clinical practice. The compression of median nerve within carpal tunnel can result in sensorimotor dysfunction and distortion in nerve morphology, physiology and mechanical properties. Clinically, nerve mobilization technique is believed to relief the clinical symptoms and alter the compliance, circulation of nerve itself as well as the surrounding soft tissue in respond to mechanical stress. The first purpose of the study was to investigate whether the severity of carpal tunnel syndrome can be predicted by the features of median nerve mechanical properties. Second, we want to investigate the effect of manual intervention in patients with carpal tunnel syndrome. The clinical effects like current pain intensity, pressure pain threshold and mechanical properties of median nerve like cross-sectional area, aspect ratio, circularity, transverse mobility and, compliance of carpal tunnel were investigated. Third, the correlation between changes in clinical symptoms and mechanical properties after mobilization were investigated. Methods：This was a randomized control trial with 30 subjects randomized assigned to 2 groups with and without nerve mobilization treatment. All subjects were tested on the mechanical properties of median nerve by Sonography imagine system and clinical symptoms before and after the median nerve mobilization and sham mobilization. Separated Pearson correlation coefficients were calculated to determine the relationships between severities of clinical symptoms and mechanical properties. Paired sample t-test were performed to examine the difference after manual intervention. Separated ANCOVA were used to test the group effects (mobilization versus sham-mobilization) for measures of clinical symptoms and mechanical properties with control the influence of age between groups. Correlation coefficients between changes in clinical symptoms and mechanical properties were conducted. Alpha level was set at 0.05 and adjusted accordingly to achieve significant difference. Results：Low correlations were found between clinical symptoms (Boston carpal tunnel syndrome questionnaire), and nerve properties (cross sectional area, r=.231; mean grey scale, r=-.316). After manual intervention (myofascial release with and without nerve mobilization), significant change were presented in pain (pre: 4.9±1→post: 2.4±1, p<.0005), compliance of carpal tunnel (pre: 4.9±1.0→post: 5.4±1.0, p<.0005), cross sectional area (pre: 11.0±3.2→post: 11.8±4.1, p=.007), circularity (pre: 0.57±0.09→post: 0.59±0.08, p=.029), mean grey scale (pre: 42.14±16.67→post: 45.34±18.12, p=.038) and transverse mobility (pre: 2.1±1.0→post: 2.4±1.3, p=.012). Results of ANCOVA indicated that there were significant difference in median nerve mechanical properties between groups. Transverse mobility of median nerve increased 34% in mobilization group compared to 4% in sham-mobilization group (p<.0005). The correlations, however, between changes in clinical symptoms and mechanical properties were less than 0.17. Conclusion：In patients with carpal tunnel syndrome, the clinical severities were correlated with the enlarged cross section area and diminished echodensity. After receiving manual intervention, both clinical symptoms and mechanical properties of median nerve can be altered while the transverse mobility of median nerve only improved in nerve mobilization group. However, the changes in clinical symptoms cannot be explained by the changes in mechanical properties alone. In order to further understand the behind mechanism of symptom relief, long term follow-up was suggested