Preliminary Application Of Shear Wave Elastography For Median Nerve Neuropathy And Diagostic Value In Carpal Tunnel Syndrome

ObjectiveTo explore the feasibility of shear wave elastography(SWE) technology in assessing the median nerve(MN) pathology for clinic, and to further elucidate the value of SWE in Carpal Tunnel Syndrome. MethodsA total of 85 patients in the neurology clinic of our hospital from December 2013 to May 2014 were included in this study. All patients had electrophysiological examination. They were divided into two groups according to electrophysiological findings and the clinical symptoms: Diabetic peripheral neuropathy group(DPN group) and Carpal tunnel syndrome group(CTS group). Seventy-three sex, age-matched healthy adults were selected as control group. Patients with other causes of peripheral neuropathy were excluded.All ultrasound examinations were performed using a 4–15 MHz linear array transducer(Aixplorer; Super Sonic Imagine, France). The forearm was in the supine position and the wrists resting on a flat surface. The median nerve was identified on the transverse plane of the forearm and the transducer was rotated 90° to obtain a sagittal imaging plane. SWE was performed for each subject. The operator kept the transducer stationary during SWE imaging acquisitions. The mean elastic modulus( Young’s modulus)of the median nerve of interest region(Region of interests, ROI) were measured. Two measuring planes were chosen for ultrasound examination. One was at the wrist carpal tunnel entrance---pisiform bone level and the other was on forearm area away from the transverse carpal pattern of 5cm. Three sets of data were recorded: ①The mean elastic modulus within the median nerve on pea level at the wrist(WEmean); ②The mean elastic modulus of the median nerve on forearm area away from the transverse carpal pattern of 5cm(FEmean); ③The ratio of the mean elastic modulus within the median nerve to the mean elastic modulus within the superficial flexor on forearm area away from the transverse carpal pattern of 5cm in the same interest region(FRatio). Calculated data were analyzed and compared. The optimal cut-off value and the area under the curve(AUC) were obtained by using Relative Operating Characteristic(ROC) curve plotting. Non-parametric Z tests were used to compare AUC.Results1. All Elastography images were clear. Every elastography images showed good disperse, and high filling level in Q-BOX. Areas with nerve appeared in blue or blue-green in control and DPN group. However, Areas with nerve appeared in blue-yellow or red in CTS group.2. The elastic parameters of SWE for 261 Median nerves were obtained successfully. The data of WEmean、FEmean and FRatio(CON/DPN/CTS)were 47.37±14.16、44.97±13.37、1.59±0.69;52.08±20.02、48.83±18.61、1.77±0.96;68.24±27.01、59.65±29.90、2.06±1.23, respectively.3. There were significant differences of the elastic parameters between CTS group and healthy control(P<0.001), CTS group and DPN group(P<0.05), respectively. While the difference between DPN group and healthy control was not statistically significant(P>0.05).4. The best cut-off value of elastic paramaters(WEmean 、FEmean and FRatio) for diagnosis of the carpal tunnel syndrome were 61.53Kpa、58.34 Kpa and 2.28,respectively. The sensitivity were 83.12%, 80.26% and 73.31%;The specificity were 76.25%, 80.19% and 65.27%.5. The area under the curve(AUC) of elastic parameters were 0.886、0.845、0.750,respectively. AUC of elastic parameters indicated that WEmean and FEmean were higher than FRatio in diagosis of Carpal tunnel syndrome(Z=2.742, P=0.006; Z=2.131, P=0.033). The sensitivity were 83.12% and 80.26% and the specificity were 76.25% and 80.19%. No significant difference was found between WEmean and FEmean(P>0.05). Conclusions1. SWE technology is feasible in the evaluation of median nerve. It can be used to assess MN stiffness quantitatively.2. The stiffness seems normal in the diabetic peripheral neuropathy group, while the stiffness increases significantly in the carpal tunnel syndrome group.3. Elastic parameters(WEmean、FEmean and FRatio) can be used to evaluate the MN stiffness of the carpal tunnel syndrome, which may provide evidence for clinic diagnosis of this disease.4. WEmean and FEmean show high value in diagnosis of carpal tunnel syndrome. From the perspective of biomechanics, elastic parameters might be used as a new parameter for evaluation of the pathology of median nerve in clinic.