Gray scale and color Doppler sonography in the diagnosis of carpal tunnel syndrome

Purpose

To determine the diagnostic accuracy of gray scale and color Doppler sonography in the diagnosis of patients with carpal tunnel syndrome.

Patients and methods

A total of 53 wrists in 41 consecutive patients with clinical suspicion of carpal tunnel syndrome, referred from the Department of Physical medicine, Rheumatology & Rehabilitation were examined with ultrasonography using a 12 MHz linear array transducer. The presence of median nerve edema, swelling, and bowing of the flexor retinaculum was evaluated by gray scale sonography, while intraneural hypervascularity was evaluated by color Doppler sonography. Sensitivity and specificity were calculated for each sonographic feature and compared with electrodiagnostic test (EDT) results.

Results

Electrodiagnostic tests confirmed carpal tunnel syndrome in 48 wrists. A median nerve cross sectional area (CSA) of 11 mm² was calculated as a definition of median nerve swelling. In comparison with electrodiagnostic tests, median nerve swelling showed the highest accuracy (89%) among the gray scale sonographic criteria, and the presence of median nerve hypervascularization showed the highest accuracy (94%) among all sonographic criteria. Median nerve edema and bowing of the flexor retinaculum showed accuracies of 81% and 77% respectively.

Conclusion

Median nerve intraneural hypervascularity detected by color Doppler sonography is more accurate in detection of median nerve involvement than gray scale sonography criteria in patients with suspected carpal tunnel syndrome.