Abstract:

Objective   To discuss measuring methods and indicators in ultrasonographic anatomy of the median nerve in carpal tunnel.  Methods   60 sides media nerve in carpal tunnel of normal subjects underwent high-frequency ultrasonographic examination. Cross-sectional area of the median nerve at entrance plane, midpoint plane and exit plane were measured.  thethickness of the palmar retinaculum, the flattening ratio of the median nerve at midpoint were measured too. The stiffness of median nerve in carpal tunnels of 30 sides was measured at the proximal 1/3 segment, middle 1/3 segment, and distal 1/3 segment by ultrasonic shear wave elastography. Results：The mean cross-sectional area of the median nerve at entrance plane, midpoint plane and exit plane respectively were（0.09±0.02）cm2，（0.08±0.02）cm2 and （0.10±0.03）cm2; There was no statistical difference among the mean value. The mean flattening ratio of the median nerve at midpoint plane was 3.12±0.29. The mean thickness of palmar retinaculum was（0.33±0.07）cm. The mean value of maximum stiffness at the proximal segment, the middle segment, and the distal segment respectively were （41.3±10.3）kPa,（35.4±5.8）kPa and（38.1±4.3）kPa，there was no statistical difference among the  mean value. Conclusion: High-frequency ultrasonographic examination may provide parameters of the median nerve in carpal tunnel, and shear wave elastography may provide stiffness parameter of the median nerve. Combined application of both examination may provide anatomical gist for clinical diagnosis of carpal tunnel syndrome.

Key words: Carpal tunnel, Median nerve, Shear wave elastography, Ultrasonagraphy