Electrical injury is known to alter the normal physiological function of nerves. In most cases, the change in function is only minor, but in severe instances the physiological function may be lost entirely. The changes in function involve the ability of the nerve to transmit an impulse, which is a function of the nerve's ability to create and maintain an electrical gradient across its membrane. When the nerve is exposed to an electrical current, the ability to maintain an electrical gradient across the membrane is reduced or lost. This change may be transient or permanent. The changes in the gradient hinder the nerve from propagating the impulse, which is the means of information transfer to and from the CNS (central nervous system). Due to the manner in which human victims are typically exposed to an electric shock, the peripheral axons usually display the greatest change in physiological function.

Indiana University-Purdue University Indianapolis (IUPUI) / Although peripheral motoneurons are phenotypically endowed with robust regenerative capacity, functional recovery is often suboptimal following peripheral nerve injury (PNI). Research to date indicates that the greatest success in achieving full functional recovery will require the use of a combinatorial approach that can simultaneously target different aspects of the post-injury response. In general, the concept of a combinatorial approach to neural repair has been established in the scientific literature but has yet to be successfully applied in the clinical situation. Emerging evidence from animal studies supports the use of electrical stimulation (ES) and testosterone as one type of combinatorial treatment after crush injury to the facial nerve (CN VII). With the facial nerve injury model, we have previously demonstrated that ES and testosterone target different stages of the regeneration process and enhance functional recovery after facial nerve crush injury. What is currently unknown, but critical to determine, is the impact of a combinatorial treatment strategy of ES and testosterone on functional recovery after crush injury to the sciatic nerve, a mixed sensory and motor spinal nerve which is one of the most serious PNI clinical problems. The results of the present study indicate that either treatment alone or in combination positively impact motor recovery. With regard to molecular effects,single and combinatorial treatments differentially alter the expression of regeneration-associated genes following sciatic nerve crush injury relative to facial nerve injury. Thus, our data indicate that not all injuries equally respond to treatment. Furthermore, the results support the importance of treatment strategy development in an injury-dependent manner and based upon the functional characteristics of spinal vs. cranial nerves.