Ultrasonographic assessment of carpal tunnel syndrome of mild and moderate severity in diabetic patients by using an 8-point measurement of median nerve cross-sectional areas

Background: Using high-resolution ultrasonography (US) to measure the median nerve cross-sectional areas (CSAs) such as in the "inching test" conducted in nerve conduction studies is a valuable tool to assess carpal tunnel syndrome (CTS). However, using this US measurement method to assess the median nerve CSA in diabetic patients with CTS has rarely been reported. Therefore, we used this US measurement method in this study to measure median nerve CSAs and to compare the CSAs of idiopathic, diabetic and diabetic polyneuropathy (DPN) patients with CTS. Methods: 124 hands belonging to 89 participants were included and assigned into four groups: control (32), idiopathic (38), diabetic (38) and DPN (16) CTS. In the latter two groups, only patients with mild and moderately severe CTS were included. The median nerve CSAs were measured at 8 points marked as i4, i3, i2, i1, w, o1, o2, and o3 in the inching test. The measured CSAs in each group of participants were compared. Results: Compared with the CSAs of the control group, enlarged CSAs were found in the idiopathic, diabetic and DPN CTS groups. The CSAs were larger at i4, i3 and i2 in the diabetic CTS group compared to the idiopathic CTS group. The CSAs measured at the i1 and w levels of the DPN CTS group were smaller than those of the diabetic CTS group. In the diabetic CTS group, the cut-off values of CSAs measured at the inlet, wrist crease, and outlet were 15.3 mm(2), 13.4 mm(2) and 10.0 mm(2), respectively, and 14.0 mm(2), 12.5 mm(2) and 10.5 mm(2), respectively, in the DPN CTS group. Conclusions: Compared with the median nerve CSAs of the control and idiopathic CTS groups, the median nerve CSAs of the diabetic patients with CTS were significantly enlarged. However, compared with the diabetic CTS group, the CSAs were significantly smaller in the DPN CTS group. This US 8-point measurement method can be of value as an important complementary tool for CTS studies and diagnosis among diabetic patients.