J Korean Soc Med Ultrasound.  2002 Jun;21(2):145-149.

High-Resolution US Findings of Carpal Tunnel Syndrome

• Chang HW
• Lee JH
• Rhee CS
• Lee SM
• Woo SK

Abstract

PURPOSE: To describe US findings of carpal tunnel syndrome (CTS) and to evaluate the diagnostic value of US in CTS by measuring the cross-sectional area of the median nerve.
MATERIALS and METHODS
Thirty one wrists from 21 patients with CTS diagnosed clinically and by electromyography and thirty two wrists from 16 normal control patients were included. The age of the patients with CTS ranged from 36 to 65 years (mean=51 years); the age of the normal control group, 31 to 62 years (mean=43 years). Axial images of the wrists at the levels of the radiocarpal joint (RCJ), mid-level of the lunate and the capitate in the neutral position were obtained. The cross sectional area (CSA) of the median nerve was calculated at three levels using a indirect method by employing a ellipse tool programmed built in sonographic machine.
RESULTS
In patients with CTS, CSA measured at the radiocarpal joint, mid-level of the lunate and capitate were 12.35 +/-.90 mm2, 14.68 +/-.83 mm2 and 8.48 +/-.88 mm2 , respectively. On the other hand, CSA of the control group, 8.44 +/-.41 mm2, 8.75 +/-.46 mm2, and 8.19 +/-.47 mm2, respectively. CSA at the radiocarpal joint and the mid lunate was bigger (or larger) in patients with CTS than in that of the controls with a statistical significance (p < 0.05) while CSA at the mid capitate was slightly bigger in patients with CTS than that of the controls but without a statistical significance. CSA of the median nerve over 12 mm2 at the mid lunate level was highly predictive of carpal tunnel syndrome (sensitivity=80.6%, specificity=93.8%, positive predictive value = 92.6%, negative predictive value=83.3%, and likelihood ratio = 13).
CONCLUSION
High resolution US can be useful in diagnosis of CTS, and CSA of the median nerve over 12 mm2 at the mid lunate level is highly predictive of carpal tunnel syndrome.

MeSH Terms

Carpal Tunnel Syndrome*
Diagnosis
Electromyography
Hand
Humans
Joints
Median Nerve
Ultrasonography
Wrist