Diagnostic value of high-frequency ultrasound in carpal tunnel syndrome during pregnancy: A case-control study

Carpal tunnel syndrome (CTS) is the most prevalent entrapment syndrome in the upper limbs, for which pregnancy is a known risk factor. CTS diagnosis is confirmed via nerve conduction studies (NCSs), which sometimes is expensive, and the electrical stimulation makes it an unpleasant diagnostic modality, especially for pregnant subjects. Recently, high-frequency ultrasonography (HF-USG) is known as a diagnostic method. This study is concerned with determining the diagnostic value of this modality for CTS among pregnant women.

This cross-sectional case-control study was conducted with 40 CTS cases and 40 matched controls. The HF-USG of wrists was performed bilaterally on all participants with a focus on the median nerve cross-sectional area (MNCSA) at the carpal tunnel (CT) inlet.

Mean MNCSA was statistically different between the CTS group (11.71 ± 1.86 mm2, range: 8 to 18 mm2) and the control group (6.75 ± 1.38 mm2, range: 4 to 11 mm2) (P < 0.001). The receiver operating characteristic (ROC) curve was drawn, and the cross-sectional area (CSA) cut-off point of 8.5 mm2 showed sensitivity and specificity of 98% and 93%, respectively. The positive predictive value (PPV) and the negative predictive value (NPV) were 95% and 98%, respectively, with the mentioned point as the diagnostic threshold.

HF-USG of the median nerve can be utilized as a preferable alternative to NCS (the current gold standard diagnostic method) in pregnant women, due to its convenience and lower cost, or at least, it can be used as a screening tool among pregnant women with suspicious symptoms.