The Diagnostic Values Of High-frequency Ultrasonography For Peripheral Nerve Entrapment Syndrome

Objective:To investigate the diagnostic values of high-frequency ultrasonography for peripheral nerve entrapment syndrome.Methods:48 healthy volunteers, 96 wrists included, as normal control group, were enrolled to have high-frequency ultrasound tests to study the ultrasonographic characteristics of the normal median nerve. 33 patients with suspected carpal tunnel syndrome, 37 wrists involved, as disease group, were examined by ultrasound to evaluate the ultrasound image of the abnormal median nerve. And the cross-sectional area(CSA )of the median nerve at the inlet and outlet of the carpal tunnel was measured both of the normal control group and disease group. 96 elbows of 48 healthy volunteers, as normal control group, were taken ultrasound exam to grasp the ultrasound data of the normal ulnar nerve. 45 patients with possible cubital tunnel syndrome, 45 elbows involved, as the disease group, were accessed by high-resolution sonography. The CSA of the ulnar nerve at the cubital tunnel inlet and outlet was measured by ultrasound both of the two groups. All of the median nerve and ulnar groups were evaluated by EMG routinely, which was blinded to the ultrsonography. The accuracy of the sonography and EMG diagnosis was confirmed by surgery. The swelling rate of median nerve and ulnar nerve was calculated and ROC curve was used to evaluate the specificity and sensitivity of the diagnosis. Variance and t-test statistics were applied to compare the differences in swelling rate CSA of the median nerve and ulnar nerve among the groups.Results:High-frequency ultrasound can not only show the structure of the normal median and ulnar nerve, but also show the morphology of median nerve of the carpal tunnel syndrome and cubital tunnel syndrome. There was no significant difference in the median nerve CSA at the inlet and outlet of carpal tunnel within normal control group (P> 0.05), while there were significant differences in the median nerve CSA between the normal control group and patients group (P <0.001). The diagnostic specificity, sensitivity, and threshold value of median nerve CSA at the carpal tunnel inlet were 91.9%, 87.5%, 8.75mm~2, respectively. The diagnostic specificity, sensitivity, and threshold value of median nerve CSA at the carpal tunnel outlet were 86.5%, 81.2%, 8.15mm~2, respectively. The swelling rate of the median nerve for the normal control group and the disease group was 1.023±0.045 and 1.392±0.361,respectively. There were highly significant differences in swelling rate of median nerve between the normal control group and the disease group(P <0.001). The diagnostic specificity, sensitivity, and threshold value of swelling rate of median nerve were 97.3%, 91.7%, 1.055, respectively. There was no significant difference to be found in the ulnar nerve CSA between the inlet and outlet of cubital tunnel in normal control group (P> 0.05), while there were significant differences in the ulnar nerve CSA between the normal control group and patients group (P <0.05). The diagnostic specificity, sensitivity, and threshold value of ulnar nerve CSA at the cubital tunnel inlet were 86.5%, 86.7%, 8.85mm~2, respectively. The diagnostic specificity, sensitivity, and threshold value of ulnar nerve CSA at the cubital tunnel outlet were 64.6%, 48.9%, 7.85mm~2, respectively. The swelling rate of the ulnar nerve for the normal control group and the disease group was 1.022±0.034 and 1.542±0.481,respectively. There were highly significant differences in swelling rate of ulnar nerve between the normal control group and the disease group(P <0.001). The diagnostic specificity, sensitivity, and threshold value of swelling rate of ulnar nerve were 91.1%, 96.9%, 1.087, respectively. Certain causes of carpal tunnel syndrome and cubital tunnel syndrome could be discovered by ultrasound. The accuracy of ultrasound diagnosis for carpal tunnel syndrome and cubital tunnel syndrome was higher than that of EMG.Conclusion:High-frequency ultrasound can show the normal structure of peripheral nerve. High-frequency ultrasound can not only show morphological changes of the nerve after entrapment, but also can access the severity of nerve compression by quantity. Peripheral nerve CSA measurement and swelling rate correlate well with the presence of peripheral nerve entrapment syndrome and are both sensitive and specific for the diagnosis. And the CSA of the peripheral nerve at the osteofibrous tunnel inlet is much more significant than the CSA of the outlet. In addiction, some of the compression factors may be discovered by the ultrasound.