Alteration of Sciatic Nerve Histology and Electrical Function After Compression and After Neurolysis in a Diabetic Rat Model

Abstract

BACKGROUND: Diabetic rats are more sensitive to nerve entrapment. This study was conducted to evaluate nerve function and histological changes in diabetic rats after nerve compression and subsequent decompression. METHODS: A total of 35 Wistar rats were included. The experimental group was divided into diabetic sciatic nerve compression group (DSNC, n = 5) and diabetic sciatic nerve decompression group (DSND, n = 20). The DSNC model was created by wrapping a silicone tube circumferentially around the nerve for 4 weeks, and then the DSND group accepted nerve decompression and was followed up to 12 weeks. The DSND group was equally divided into DSND 3 weeks (DSND3), 6 weeks (DSND6), 9 weeks (DSND9), and 12 weeks (DSND12) groups. Five rats were taken as normoglycemic control group (CR, n = 5), and another 5 rats as diabetic control group (DM, n = 5). The mechanical hyperalgesia of rats was detected by Semmes-Weinstein nylon monofilaments (SWMs) and by motor nerve conduction velocity (MNCV). These 2 physiological indicators and histology of sciatic nerves were compared among different groups. RESULTS: The SWM measurements improved toward normal values after decompression. The SWM value was significantly lower (more normal) in the DSNC groups than in the DSND group (P < 0.05). The MNCV was 53.7 ± 0.8 m/s in the CR group, whereas it was 28.4 ± 1.0 m/s in the DSNC group (P < 0.001). Six weeks after decompression, the MNCV was significantly faster than that in the DSNC group (P < 0.001). Histological examination demonstrated chronic nerve compression, which responded toward normal after decompression, but with degree of myelination never recovering to normal. CONCLUSIONS: Chronic compression of the diabetic sciatic nerve has measureable negative effects on sciatic nerve motor nerve function, associated with a decline of touch/pressure threshold and degeneration of myelin sheath and axon. Nerve decompression surgery can reverse these effects and partially restore nerve function.