To investigate the echo intensity and cross-sectional area of the median nerve in patients with type 2 diabetes mellitus.

Sixty-seven patients with type 2 diabetes mellitus were enrolled in this study at Huangshan City People's Hospital, including 25 patients without diabetic distal symmetrical polyneuropathy (DSPN) and 42 with DSPN. Twenty-five healthy subjects were included as controls. High-frequency ultrasound was used to measure the cross-sectional area (CSA) of five different sites of the median nerve (MN) of the non-dominant hand. Image J software was used to calculate the percentage of the hypoechoic area in the median nerve. The correlation between median nerve CSA and percentage of the hypoechoic area was analyzed.

The overall differences of median nerve CSA and percentage of the hypoechoic area (HA) among the three groups were statistically significant (P＜0.05). The CSA values of patients with DSPN was significantly larger than those of healthy controls [MN1: (9.43±1.79) mm vs (7.23±1.22) mm, t=5.843, P＜0.001; MN2: (10.07±1.74) mm vs (7.49±1.30) mm, t=6.701, P＜0.001; MN3: (7.61±1.23) mm vs (5.94±1.03) mm, t=5.816, P＜0.001; MN4: (7.15±1.03) mm vs (5.24±0.69) mm, t=7.597, P＜0.001; MN5: (13.51±2.85) mm vs (11.03±1.78) mm, t=4.110, P＜0.001]. The percentages of HA of patients with DSPN were significantly higher than those of healthy controls [MN1: (66.61±5.17)% vs (54.66±3.39)%, t=9.209, P＜0.001; MN2: (63.50±6.46)% vs (53.91±3.09)%, t=6.835, P＜0.001; MN3: (58.16±4.20)% vs (49.61±2.64)%, t=8.266, P＜0.001; MN4: (54.84±4.94)% vs (45.63±4.08)%, t=8.284, P＜0.001; MN5: (59.42±4.79)% vs (55.06±3.44)%, t=3.949, P＜0.001]. When 55.64% was used as the cut-off value, the percentage of the HA at MN2 had the highest specificity (91.0%) for identifying DSPN, with a sensitivity of 76.0% and area under the curve of 0.889. There was a positive correlation between CSA and the percentage of the HA at different sites of the MN except the MN5 (r=0.442, 0.554, 0.387, and 0.463, respectively; P＜0.01).

Peripheral nerves are enlarged diffusely in diabetic patients with DSPN, and the percentage of the HA increases. Both of these findings are useful for the identification of DSPN at early stage.