Comparison of proximal and distal cross-sectional areas of the median nerve, carpal tunnel, and nerv/tunnel index in subjects with carpal tunnel syndrome

OBJECTIVES: To provide a quantitative analysis of ultrasonographic measurements and possible pathophysiology of carpal tunnel syndrome by comparing cross-sectional areas of the median nerve, carpal tunnel, and nerve/tunnel index and the difference in ultrasonographic findings between affected and nonaffected hands and between sexes. DESIGN: Blinded comparison study. SETTING: Secondary referral and training hospital of institutional practice. PARTICIPANTS: Patients (N=51; 42 women, 9 men) with suspected carpal tunnel syndrome who underwent sonography within 1 week after the electrodiagnostic study. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Electrodiagnostic and ultrasonographic studies were conducted on both upper extremities. Cross-sectional areas of the median nerve and carpal tunnel were measured at 2 separate levels; proximal and distal cross-sectional areas of the carpal tunnel were each measured at the scaphoid-pisiform and trapezium-hamate levels, respectively. RESULTS: Comparison between normative (n=24) and abnormal hands (n=78) revealed the following: the mean proximal cross-sectional areas of the median nerve, carpal tunnel, and nerve/tunnel index of electrodiagnostically normative hands were 10.941mm(2), 192.43mm(2), and 5.635%, respectively, whereas those of abnormal hands were 13.74mm(2), 208.87mm(2), and 6.693%, respectively, showing statistically significant differences for all (P<.05). Distal measurements of the cross-sectional area of the median nerve, carpal tunnel, and nerve/tunnel index were 10.088mm(2), 150.4mm(2), and 6.762%, respectively, in normative hands, and 11.178mm(2), 149.6mm(2), and 7.493%, respectively, in abnormal hands, showing no statistically significant differences (P>.05). In women, proximal cross-sectional areas of the median nerve and nerve/tunnel index of abnormal hands showed statistically significant differences, but no ultrasonographic measurement with a statistically significant difference was observed in men. CONCLUSIONS: Compared with nonaffected ...