Transection of a mixed (sensory+motor) peripheral nerve causes loss of skin sensation and focal muscle weakness and wasting to an extent determined by the site and severity of nerve injury.
Open nerve injuries may be caused by stabbing or by gunshot wounds. Nerve injuries associated with stabbing require early exploration and repair as lack of continuity can be assumed and spontaneous recovery will not occur. Gunshot wounds, on the other hand may cause loss of nerve function without loss of nerve continuity: if there are not other reasons to explore the wound, it may be reasonable to delay exploration for several months to assess spontaneous recovery. A special class of open nerve injuries consists of iatrogenic injuries following surgery, for example to the spinal accessory nerve after lymph node biopsy in the neck: here also prompt exploration and repair offers the best chance of a satisfactory outcome.
Some examples of nerve injury and their treatment are as follows:
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Closed nerve injuries can be caused by stretch, for example of the peroneal nerve after knee injury or by trauma at a fracture site, for example the radial nerve in association with fracture of the humerus. Assessment by clinical examination plus electrophysiology and/or radiology will determine whether the nerve is likely to be torn in two and requiring repair or in continuity with good prognosis for spontaneous recovery of function. The general principles for surgical treatment are the same for any nerve injury as for brachial plexus injury. The usual method of nerve repair is through nerve grafting. Some nerve injuries are treated better by nerve transfer, for example with use of a branch of the radial nerve to innervate the circumflex axillary nerve. The most important determinant of the outcome following nerve injury and repair is the nerve involved. The results of repair are good to excellent for predominantly motor nerve such as the radial, musculocutaneous, or spinal accessory nerve but much less satisfactory for nerves with complex motor and sensory function such as the median, ulnar, or peroneal nerve. One to two years after such nerve injury, further nerve surgery is usually futile. For nerve injuries which are longstanding or involve problematic nerves, muscles and/or tendons of the functionally intact antagonistic muscle groups can be rerouted to bring back a lost function.
Some examples of commonly occurring and maiming longstanding nerve lesions are, claw hand deformity in ulnar nerve lesion, wrist and finger drop in radial nerve lesion and the foot drop in peroneal palsy.
In such longstanding lesions, it is still possible to restore the lost function through secondary reanimation procedures such as tendon and muscle transfers.
Some examples are depicted as follows:
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