Ann Rehabil Med.  2012 Feb;36(1):72-79. 10.5535/arm.2012.36.1.72.

Ultrasonography of Median Nerve and Electrophysiologic Severity in Carpal Tunnel Syndrome

• Kang S
• Kwon HK
• Kim KH
• Yun HS

• KMID: 2266783
• DOI: http://doi.org/10.5535/arm.2012.36.1.72

Abstract

OBJECTIVE
To investigate the correlation of the ultrasonographic wrist-to-forearm median nerve area ratio (WFR) and cross sectional area of median nerve at the wrist (CSA-W) to the electrophysiologic severity in patients with carpal tunnel syndrome (CTS). METHOD: One hundred and ten wrists electrophysiologically graded as mild, moderate, and severe CTS and 38 healthy controls underwent ultrasonography of median nerve at the distal wrist crease and mid-forearm. WFR and CSA-W were analyzed according to the severity of CTS.
RESULTS
WFR was 1.12+/-0.14, 1.91+/-0.33, 2.27+/-0.47 and 3.02+/-0.97 and the CSAs-W was 7.23+/-1.67 mm2, 13.51+/-3.72 mm2, 14.67+/-2.93 mm2, and 18.74+/-6.01 mm2 in controls, mild (n=28), moderate (n=46), and severe (n=36) CTS, respectively. CSA-W displayed significant differences between the control and the mild CTS, moderate CTS and severe CTS groups. However, there was no significant difference between mild CTS and moderate CTS groups. WFR revealed significant difference between all groups. The sensitivity and specificity of the WFR in grading the severity of CTS were higher than those of the CSA-W.
CONCLUSION
Ultrasonography is a useful complementary tool for the evaluation of CTS. Both WFR and CSA-W are highly correlated with severity grade of CTS. However, WFR is superior to CSA-W for diagnosis and grading of the severity of CTS.

Keyword

Carpal tunnel syndrome; Ultrasonography; Electrophysiologic severity; Cross sectional area; Ratio

MeSH Terms

Carpal Tunnel Syndrome
Humans
Median Nerve
Sensitivity and Specificity
Wrist

Figure

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  Fig. 1 Placement of ultrasonographic probe at the forearm. Ultrasonographic transverse scan was done at two different levels. The cross sectional areas of median nerve were measured at the distal wrist crease (A) and 12 cm proximal to this level (B). A/B ratio was obtained.

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  Fig. 2 Median nerve images. The nerve is identified by its location and characteristic stippled appearance. DWC: Distal wrist crease.

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  Fig. 3 A receiver operator characteristic (ROC) curve showing the relationship between sensitivity and specificity for each ultrasonographic parameter in diagnosis of carpal tunnel syndrome (A), moderate to severe carpal tunnel syndrome (B), and severe carpal tunnel syndrome (C). CSA: Cross sectional area, WFR: Wrist-to-forearm ratio.

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