OBJECTIVES: To assess the feasibility of using ultrasound (US) image features 
related to the median nerve echogenicity and shape for carpal tunnel syndrome 
(CTS) diagnosis.
METHODS: In 31 participants (21 healthy participants and 10 patients with CTS), 
US images were collected with a 30-MHz transducer from median nerves at the 
wrist crease in 2 configurations: a neutral position and with wrist extension. 
Various morphologic features, including the cross-sectional area (CSA), were 
calculated to assess the nerve shape. Carpal tunnel syndrome commonly results in 
loss of visualization of the nerve fascicular pattern on US images. To assess 
this phenomenon, we developed a nerve-tissue contrast index (NTI) method. The 
NTI is a ratio of average brightness levels of surrounding tissue and the median 
nerve, both calculated on the basis of a US image. The area under the curve 
(AUC) from a receiver operating characteristic curve analysis and t test were 
used to assess the usefulness of the features for differentiation of patients 
with CTS from control participants.
RESULTS: We obtained significant differences in the CSA and NTI parameters 
between the patients with CTS and control participants (P < .01), with the 
corresponding highest AUC values equal to 0.885 and 0.938, respectively. For the 
remaining investigated morphologic features, the AUC values were less than 
0.685, and the differences in means between the patients and control 
participants were not statistically significant (P > .10). The wrist 
configuration had no impact on differences in average parameter values 
(P > .09).
CONCLUSIONS: Patients with CTS can be differentiated from healthy individuals on 
the basis of the median nerve CSA and echogenicity. Carpal tunnel syndrome is 
not manifested in a change of the median nerve shape that could be related to 
circularity or contour variability.