Ultrasonography of the Transverse Movement and Deformation of the Median Nerve and Its Relationships With Electrophysiological Severity in the Early Stages of Carpal Tunnel Syndrome

Abstract

BackgroundTo date, there have been conflicting suggestions regarding the initial pathogenesis of carpal tunnel syndrome (CTS). It has been characterized as either inflammation of the median nerve caused by compression or noninflammatory fibrosis of the subsynovial connective tissue (SSCT). ObjectiveTo investigate the initial pathogenesis of CTS, we compared the deformation and displacement of the median nerve in accordance with the electrophysiological severity between patients with CTS (via the Bland scale) and healthy controls. DesignCross-sectional, case-control study. SettingGeneral teaching hospital, rehabilitation unit. PatientsThirteen hands of 10 healthy participants and 39 hands of 27 patients with CTS were recruited and classified into 4 groups (stage 0−3) according to the severity of the electrodiagnostic test results. MethodsUltrasound images of the median nerve in response to the wrist and finger motions were analyzed. Main Outcome MeasureWe measured the deformation of the median nerve (the maximal change values of the median nerve area, and aspect ratio of the minimum-enclosing rectangle [MER]) and movement of the median nerve (the maximal change value of the median nerve displacement) in response to the motions of wrists and finger. The maximal change value of the median nerve displacement was normalized with respect to the width of the wrist. Moreover, the maximal change values of the median nerve area, and the aspect ratio of the MER, were also normalized to the median nerve area and the aspect ratio of the MER in wrist-neutral position with finger extension. ResultCTS patients in stage 3 showed a significantly lower normalized maximal change of the median nerve movement compared with CTS patients in stages 0, 1, and 2 (P <.001). Regarding the deformation of the median nerve, however, there were statistically significant differences among all groups (area, P < .001; MER, P <.001). According to multivariate logistic regression analysis, the normalized maximal change of the aspect ratio of the MER is a meaningful parameter in diagnosing the initial stage of CTS (P < .01). ConclusionThese results showed that the deformation of the median nerve may be associated with the initial pathogenesis; however, further studies are necessary to validate the findings of this study. Level of EvidenceIII