The surgical management of gunshot injuries to the brachial plexus differs considerably from the commonly encountered high-speed traction injuries.
Timing of Repair
Patients with missile injuries to the brachial plexus are generally observed for 3 months. These injuries are best treated as delayed repair if there is little or no recovery.
Neurolysis – In gunshot injury lesions in continuity are common. Intraoperative nerve stimulation and recording of compound nerve action potentials (CNAP) have been used to assess the neuronal integrity. When CNAP isfound to traverse the lesion, neurolysis provides good functional results. Performed alone it is very effective in peripheral nerves surrounded by a layer of fibrous tissue. It is not equally effective when nerve elements are surrounded in dense fibrous tissue.
Nerve grafting – When no CNAP is found to traverse the lesions, neuroma resection and nerve grafting are performed.
In upper truncal lesions with complete rupture, sural nerve grafting combined with spinal accessory to suprascapular and ulnar fascicle to biceps branch results in good functional outcomes. Treatment of partial ruptures with neurolysis of intact fascicles and nerve grafting of damaged segment also results in good functional outcomes. In C5,C6, and upper truncal reconstruction nerve grafts (to bridge the nerve defects) supplemented with nerve transfers are preferred. A direct transfer of the spinal accessory nerve to the suprascapular nerve reduces loss of regenerating axons at the coaptation site, which occurs at two places when a nerve graft is used. The addition of ulnar fascicular transfer to the biceps branch results in an early restoration of elbow flexion.
A few patients with missile injuries to the brachial plexus manifest with severe pain. Pain syndrome is present in four distinct patterns: causalgia, neurostenalgia, posttraumatic neuralgia, and central pain. Causalgia results from partial transection of C8,T1 roots, lower trunk, medial cord, or its branches, and is characterized by extensive burning pain, allodynia, and hyperpathia. This pain with associated sympathetic components may be relieved temporarily by sympathetic blockade. Neurostenalgia results from an entrapment of nerve in the fibrous tissue. Posttraumatic neuralgia results from a partial injury to the nerve. Central pain is less common and caused by an injury to proximal roots or the spinal cord.
Best results are obtained following repair of upper trunk, lateral cord, musculocutaneous, and radial nerves. In selected cases limited nerve transfers provide good return of shoulder and elbow functions. Repairs of middle trunk neuroma, posterior cord, and median nerve also result in satisfactory outcomes. Results are highly unsatisfactory following repair of lower trunk, medial cord, and ulnar nerve lesions.