main types of nerve injury
Nerves sustain a gradient of injury, which was originally defined by Seddon:
1. Neurapraxia is the functional loss of conduction without anatomic change of the axon, usually due to focal demyelination. With remyelination, conduction returns to normal.
2. In axonotmesis, the axonal continuity is lost. With its loss, Wallerian degeneration occurs in the distal segment. Recovery, which is frequently incomplete, occurs as a result of axonal regrowth at a rate of 1–3 mm/day in otherwise healthy individuals.
3. Neurotmesis results from separation of the entire nerve, including its supporting connective tissue. Regeneration frequently does not occur. Nerves with this degree of trauma may need surgical attention for recovery to occur.