Which of the following statements are true?

C. Secondary repair of a lacerated nerve 3 to 8 weeks after injury has several advantages.

DISCUSSION: The Hoffmann-Tinel sign identifies the most distal point of small nerve fiber regeneration. As nerve regeneration progresses, this point moves farther away from the level of the nerve injury. Causalgia is a specific severe pain syndrome that may accompany a partial injury to a mixed peripheral nerve. As compared with primary repair, the extent of damage to a nerve can be better assessed and the correct amount trimmed off, with a secondary repair 3 to 8 weeks after the injury; the epineurium and perineurium are stronger and can be sutured more easily; optimal operating room conditions can be arranged; and there is no time for wallerian degeneration (i.e., the involved neurons are capable immediately of regenerating new distal segments, and the regenerating axons can penetrate the repair site before a significant amount of scar forms). If a clinically nonfunctioning nerve is in continuity when it is explored some weeks after the initial injury the surgeon may find it helpful to stimulate the nerve electrically proximal to the injury and to look distally for evidence of muscle contraction or transmission of nerve action potentials. If there is no evidence of transmission across the area of injury, the injured portion of the nerve should be excised and the cut ends sutured together. If there is transmission across the area of injury, surgical treatment should be limited to external neurolysis. A disrupted nerve should be reapproximated surgically, but only after each end has been trimmed back to healthy fascicles. The trimmed nerve ends must not be under tension when they are sewn together.