Ultrasound Imaging in the Diagnosis of Carpal Tunnel Syndrome and Its Relevance to Clinical Evaluation

Unlabelled: In ultrasound evaluation, median nerve can be measured quantitatively with a high reproducibility. In this study we looked for the diagnostic role of ultrasound in the carpal tunnel syndrome and its correlation with some clinical tests as Phalen and Tinnel sign.

Methods: Twenty-four patients with signs and positive EMG results of CTS along with 14 age and sex matched healthy subjects were evaluated with ultrasound. The flattening ratios, cross-sectional areas of the nerve were calculated. The ultrasonographic results of the patient and control groups were compared with t-test. The correlations between clinical tests were investigated.

Results: Mean cross-sectional area of the median nerve in the carpal tunnel was 10.29 +/- 3.39 mm(2) proximally, 15.28 +/- 6.16 mm(2) in the middle, 13.78 +/- 4.76 mm(2) distally. Mean flattening ratio in the carpal tunnel was 2.20 +/- 0.36 proximally, 2.61 +/- 0.54 in the middle, 3.07-0.69 distally. In the control group the cross-sectional areas were as follows: 6.46 +/- 0.72 mm(2) proximally, 6.94 +/- 0.72 mm(2) in the middle, 6.65 +/- 0.64 were mm(2) distally; mean flattening ratios were 1.76 +/- 0.18 proximally, 2.00 +/- 0.21 in the middle, 2.36 +/- 0.23 distally. At all of the levels the cross-sectional areas were significantly different between the two groups (p < 0.001). The sonographic signs were found correlated with both Phalen test (r = 0.80, p < 0.001), and Tinnel sign (r = 0.70, p < 0.001). The sensitivity and specificity of ultrasound was 89% and 100%, respectively.

Conclusion: The combination of typical clinical symptoms and at least one pathologically increased sonographic measurement of median nerve is highly predictable for diagnosis of carpal tunnel syndrome.