Nerve injury can occur as a result of major acute trauma, such as a gunshot wound, or develop more slowly as a result of milder but continuous trauma. The degree of neurologic deficit and the prospect for recovery depend on several factors. Typically, acute injuries resulting in anatomic disruption of the nerve cause more severe and lasting disability than do slowly developing injuries that leave the nerve in anatomic continuity.
Nerve Severance Results in a Predictable Sequence of Changes in the Nerve and Muscle
If nerve continuity is disrupted as a result of trauma, the nerve segment distal to the injury undergoes Wallerian degeneration. This process involves disintegration of axoplasm and axolemma and ultimately results in the breakdown and phagocytosis of myelin, taking several weeks to complete. Severe degeneration of the nerve implies that any recovery of function will require regeneration of nerve fibers from the intact nerve stump to the appropriate muscle or sensory organ.