There are several different imaging methods that are helpful in the diagnosis of carpal tunnel syndrome, including traditional radiography, computed tomography (CT), and magnetic resonance imaging (MRI). CT and MRI offer the advantage of providing direct visualization of the structural abnormality of the carpal tunnel and median nerve, but both of these modalities are expensive and time-consuming. Recently, high-resolution ultrasonography has been reported to be effective in the study of the musculoskeletal system. The authors designed a case-control study to assess the diagnostic value of high-resolution ultrasonography. Forty-eight patients, for a total of 96 hands, whose diagnosis was confirmed by self-administered questionnaire and electrodiagnostic tests, underwent high-resolution ultrasonographic studies. The authors compared the sonographic findings with the electromyographic data and the patients' severity scores on the self-questionnaires. Proximal swelling of the median nerve at the entrance to the carpal tunnel was found to correlate with the nerve conduction data. Also, compression of the median nerve under the transverse carpal ligament was found to correlate with the subjective symptoms. Although ultrasonography is not an ideal method of diagnosis for carpal tunnel syndrome, it may be helpful for estimating the symptom severity and nerve conduction deficit.

The authors evaluated the morphologic changes that follow division of the transverse carpal ligament in patients with carpal tunnel syndrome (CTS) using high-resolution ultrasonography. Ten patients, for a total of 20 hands, underwent high-resolution ultrasonographic studies before the operation and 8 months after the operation. They were all diagnosed with bilateral idiopathic CTS. The authors evaluated the configuration of the median nerve and carpal tunnel at 3 different levels of the wrist: the distal radiocarpal joint level, the pisiform level, and the hook of hamate level. The median nerve gained in thickness to a remarkable extent at 2 distal levels after the operation. The change in morphology of the carpal tunnel at these 2 distal levels was obvious, but the cross-sectional area of the carpal tunnel was increased significantly only at the hook of hamate level. The transverse diameters of the carpal tunnel were not significantly changed. As mentioned, the authors found that the median nerve gained significantly in volume at the distal part of the carpal tunnel postoperatively, and the volumetric increase in the carpal tunnel appears to have resulted from an anterior displacement of newly formed transverse carpal ligament, rather than from a widening of the bony carpal arch.