After studying this article, the participant should be able to: 1. Evaluate clinically a patient with brachial plexus paralysis and define the appropriate electrophysiologic and radiographic studies. 2. Differentiate between preganglionic (root) avulsion and postganglionic lesions and identify appropriate motor donors and nerve grafts. 3. Describe various nerve reconstructive strategies and make appropriate selection of secondary procedures for shoulder stability, elbow flexion, and hand reanimation. 4. Anticipate the possible functional outcome.

Posttraumatic brachial plexus palsy is a severe injury primarily affecting young individuals at the prime of their life. The devastating neurological dysfunction inflicted in those patients is usually lifelong and creates significant socioeconomic issues. During the past 30 years, the surgical repair of these injuries has become increasingly feasible. At many centers around the world, leading surgeons have introduced new microsurgical techniques and reported a variety of different philosophies for the reconstruction of the plexus. Microneurolysis, nerve grafting, recruitment of intraplexus and extraplexus donors, and local and free-muscle transfers are used to achieve optimal outcomes. However, there is yet no consensus on the priorities and final goals of reconstruction among the various centers.

End-to-side nerve repair allows for target-muscle reinnervation, with simultaneous preservation of donor-nerve function. Local administration of insulin-like growth factor-I (IGF-I) has been shown to increase the rate of axon regeneration in crush-injured and freeze-injured rat sciatic nerve. The purpose of the current project was to determine the effects of IGF-I in a rat model of end-to-side nerve repair. The left musculocutaneous nerve of 18 adult male Sprague-Dawley rats was fully transected to induce biceps-muscle paralysis. The distal stump of the musculocutaneous nerve was then coapted by end-to-side neurorrhaphy through a perineurial window to the ipsilateral median nerve. All animals were randomly assigned to three groups: Group A received 100 microg/ml IGF-I; Group B received 50 microg/ml IGF-I; and control Group C received 10 mM acetic acid vehicle solution. Infusions were regulated by the Alzet model 2004 mini-osmotic pump, with an attached catheter directed at the coaptation site. Weekly postoperative behavioral evaluations revealed significantly increased functional return over control in both experimental groups as early as 3 weeks. After 28 days, histology evaluations revealed statistically significantly higher musculocutaneous nerve axon counts and myelin thickness/axon diameter ratios in both experimental groups vs. controls. The three groups were not significantly different in motor endplate counts of the biceps muscle. Groups A and B were not significantly different in all parameters tested. This study suggests that local infusion of IGF-I may expedite the functional recovery of a paralyzed muscle, by increasing the rate of axon regeneration through an end-to-side nerve graft.

The functional recovery of a muscle target following nerve repair is inversely related to the denervation time: i.e., the longer the muscle denervation, the poorer the functional outcome following nerve reconstruction. The trophic and protective effects of sensory innervation to a motor nerve, following prolonged denervation (greater than 6 months), have been studied. Following proximal transection of the musculocutaneous nerve (MC) close to its C6 origin in 10 adult male Sprague-Dawley rats, the severed nerve was coapted to supraclavicular purely sensory nerves originating from C3 and C4 (sensory protection [SP] group). In another 10 Sprague-Dawley rats, the transected MC nerve was not protected by coaptation to sensory nerves (control group). After prolonged denervation or "sensory protection" (6 months), the MC nerve was then coapted in both groups to the purely motor medial pectoral nerve. Behavioral testing (grooming test) was performed on a weekly basis during the reinnervation time, which lasted 4 weeks. Statistically significant differences (p<0.05) favoring the SP group, were found at the second week of the reinnervation period, but not at the end of the experiment. Evaluation also included intraoperative electrical stimulation of the MC nerve, biceps muscle dry weights, motor endplate counts, and nerve axon counts of the MC nerve. The biceps muscle dry weights were statistically higher in the SP group, along with a trend for a higher number of motor endplates. No statistically significant difference was found in the nerve axon counts of the MC nerve between the two groups. Statistically better intraoperative electrical stimulation results were also encountered in the sensory protection group. An interpretation of the results favors the hypothesis that sensory reinnervation of a motor target may provide the necessary trophic environment to minimize muscle atrophy, until a motor donor nerve becomes available.