Skin temperature changes following sciatic nerve injury in rats.

In the clinical setting, skin temperature is both easily evaluated and useful in assessments of sympathetic dysfunction. The present study purposed to observe the serial skin temperature changes of both hindlimbs following several types of sciatic nerve injury (complete transection and ligation model [CTL], crush injury model [CRI], and chronic constriction injury model [CCI]) in Sprague-Dawley rats and, further, to delineate the possible mechanisms through various evaluation methods. The temperature differences between the intact and injured areas (ΔT) on the plantar surface and toes varied among the CTL, CRI, and CCI injury models during the acute stage (7 days post-injury). During the subacute to chronic stages (7-28 days post-injury), ΔT on the plantar area and toes of the CCI model were higher than those of the CTL and CRI models. The sciatic functional index was gradually restored in the CRI and CCI models, but was unchanged in the CTL model. The CTL model showed constant hypoesthesia; the CRI model, contrastingly, was restored to normal, and the CCI model showed gradual hyperesthesia until 28 days post-injury. The latency and amplitude of the compound muscle action potential (CMAP) in the involved plantar muscle was not found in the CTL group 4 weeks post-injury, but showed gradual restoration in the CRI and CCI models. Regression analysis revealed that the ΔT in the plantar area and toes were affected only by the CMAP amplitude in the involved plantar muscle; therefore, it can be said that the skin temperature on the injured area after sciatic nerve injury was influenced by the functional status of the involved muscle. Measurement of skin temperature can differentiate mild peripheral nerve injury from moderate-to-severe injuries, although its clinical significance might be limited.