Effects of Steroid on the Development of Neuropathic Pain with an Experimental Model of Peripheral Neuropathy

Lee, Sang Heon

Abstract

OBJECTIVE
The purpose of this study was to evaluate the anti-inflammatory effect of steroid in the neuroma plays a key role in the development of neuropathic pain. METHOD: Materials consisted of 21 male Sprague-Dawley rats (8 weeks old, 180~200 g), which were divided into a steroid (n=9) and control group (n=12). Neuropathic pain was produced by unilateral transection of the superior caudal trunks at the level between the S3 and S4 spinal nerves. We compared two groups of rats, the steroid group injecting 1 ml (40 mg) of Methylprednisolone (Depo-Medrol), and the control group injecting 1 ml of nomal saline on operation site just after operation. Behavioral reactions to mechanical allodynia were checked using a von Frey hairs of 2.0 g (19.6 mN) bending force at pre-operation, post-operative 1, 4, 7, 10 & 14 day to evaluate the steroid effect on the development of neuropathic pain.
RESULTS
The steroid group exhibited less tail-flick frequencies to mechanical stimulation: 14.8+/-17.0%, 28.1+/-18.3%, 38.1+/-28.3% at post-operative 4, 7, 10 days respectively in control group; 30.3+/-21.2% 43.6+/-21.3%, 47.2+/-20.8% at post-operative 4, 7, 10 days, respectively. But there was no significant difference between both groups at post-operative 14 days. The steriod reduced the pain at early stage of neuropathic pain development, but failed to decrease the pain level in late stage.
CONCLUSION
These results suggest that the steroid induced anti-inflammatory effect in the injured neuroma is not a key factor in the development of neuropathic pain.