Electrically, the nerve shows rapid and complete degeneration, with loss of voluntary motor units. Regeneration of the motor end plates will occur, as long as the endoneural tubules are intact.Axonotmesis involves the interruption of the axon and its covering of myelin, but with preservation of the connective tissue framework of the nerve (the encapsulating tissue, the epineurium and perineurium, are preserved). Because axonal continuity is lost, Wallerian degeneration occurs. Electromyography (EMG) performed 2 to 4 weeks later shows fibrillations and denervation potentials in musculature distal to the injury site. Loss in both motor and sensory spines is more complete with axonotmesis than with neurapraxia, and recovery occurs only through regenerations of the axons, a process requiring time. Axonotmesis is usually the result of a more severe crush or contusion than neurapraxia, but can also occur when the nerve is stretched (without damage to the epineurium). There is usually an element of retrograde proximal degeneration of the axon, and for regeneration to occur, this loss must first be overcome. The regeneration fibers must cross the injury site and regeneration through the proximal or retrograde area of degeneration may require several weeks. Then the neuritis tip progresses down the distal site, such as the wrist or hand. Proximal lesion may grow distally as fast as 2 to 3 mm per day and distal lesion as slowly as 1.5 mm per day. Regeneration occurs over weeks to years. Neurotmesis
Neurotmesis is the most severe lesion with no potential of full recovery. It occurs on severe contusion, stretch, or laceration.
Folliculitis nares perforans is characterized by small pustules near the tip of the inside of the nose, lesions that become crusted, and when the crust is removed it is found that the bulbous end of the affected vibrissa is embedded in the inspissated material. : 774

See also
Skin lesion


== References ==