Figure 1. Challenges to successful regeneration with proximal injuries.

Good sensory and motor recovery is likely if surgery is not delayed after a distal nerve injury, such as median nerve injury at the carpal tunnel. However, motor recovery after a more proximal injury, for example, to the ulnar nerve at the cubital tunnel in the elbow, is likely to be slow and incomplete due to the atrophic changes that take place in the distal portions of the nerve. One of the key reasons for this poor recovery of motor function is the slow rate of axonal regeneration; it takes too long for the injured axons to regenerate and connect with Schwann cells and muscle.