Nerve tissue that has become irritated from tension, compression, or hypoxia may not have permanent damage and shows signs of recovery when the irritating factors are eliminated. When the nerve has been injured, recovery is dependent on several factors including the extent of injury to the axon and its surrounding connective tissue sheath, the nature and level of the injury, the timing and technique of the repair (if necessary), and the age and motivation of the person.

• Nature and level of injury. The more damage to the nerve and tissues, the more tissue reaction and scarring occur. Also, the proximal aspect of a nerve has greater combinations of motor, sensory and sympathetic fibers, so disruption there results in a greater chance of mismatching the fibers, thus affecting regeneration. Regeneration is often said to occur at a rate of 1 inch per day, but rates from 0.5 to 9.0 mm per day have been reported based on the nature and severity of the injury, duration of denervation, condition of the tissues, and whether surgery is required.

• Timing and technique of repair. Laceration or crush injuries that disrupt the integrity of the entire nerve require surgical repair. Timing of the repair is critical, as is the skill of the surgeon and technique used to align the segments accurately and avoid tension at the suture line for optimal nerve regeneration. Different regenerative potential outcomes following nerve repair have also been reported based on groupings of specific nerves.
  • Excellent regenerative potential: radial, musculocutaneous, and femoral nerves
  • Moderate regenerative potential: median, ulnar, and tibial nerves
  • Poor regenerative potential: peroneal nerve

• Age and motivation of the patient. The nervous system must adapt and relearn use of the pathways once regeneration occurs. Motivation and age play a role in this, especially in the very young and the elderly.
Smith described five possible outcomes of nerve regeneration.

• Exact reinnervation of its native target organ with return of function

• Exact reinnervation of its native target organ but no return of function due to degeneration of the end organ

• Wrong receptor reinnervated in the proper territory, improper input

• Receptor reinnervation in wrong territory causing false localization of input

• No connection with an end organ

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