Comparing a new ultrasound approach with electrodiagnostic studies to confirm clinically defined carpal tunnel syndrome: a prospective, blinded study.

OBJECTIVE

The aims of this study were to compare electrodiagnostic (EDX) confirmation of clinical diagnosis of carpal tunnel syndrome (CTS) with ultrasonography (US), using a new set of normal values taking wrist circumference of subjects into account, and to determine whether EDX examination can be replaced by US to confirm CTS.

DESIGN

A prospective cohort of 156 patients with idiopathic CTS underwent US and EDX studies. Upper levels of normal cross-sectional area of the median nerve were established by taking wrist circumference into account and using linear regression equations.

RESULTS

Of the selected patients, 83.3% met the EDX criteria for CTS. The findings from the US were normal in 67 (42.9%) of 156 patients, and within this group, the findings from the EDX were abnormal in 44 patients (65.7%). Of 89 patients with abnormal findings from the US, only 3 patients had normal findings from the EDX.

CONCLUSIONS

US cannot replace EDX for confirmation of clinical diagnosis of CTS. However, an abnormal US test result has a high positive predictive value for abnormal EDX result in clinically defined CTS. US might reveal relevant anatomic information preoperatively that rarely has a direct influence on treatment management of patients with CTS. US testing, taking morphometric data into account, does not have the same diagnostic value as EDX does in confirming CTS.