Excerpts from <a href="http://cal.vet.upenn.edu/saortho/chapter_65/65mast.htm">http://cal.vet.upenn.edu/saortho/chapter_65/65mast.htm</a>
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This one says a nerve that is cut in two and the ends are up to 3/4" apart can regrow itself and close the gap:
On occasion, a short irreducible gap may be encountered without immediate provision for graft repair as described above. In these cases, an alternative approach may be to bring the nerve stumps as close as possible in a dry tissue bed and tack the stumps to the tissue bed with two epineurial sutures in each stump. This will create a nerve gap without continuity. This technique may be used for defects not exceeding 1 cm to 2 cm in length. Successful regeneration across nerve gaps has been reported in the dog and in children. However, factors discussed previously must be overcome to obtain success. In addition, increased regeneration time should be expected."
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This one says it is sometimes better to wait 2-6 weeks to do nerve surgery until other traumatic injuries have healed somewhat:
"The timing of surgical repair depends upon the type of injury encountered and the facilities available at the time of initial presentation. Two basic types of surgical repair have been advocated in the literature: immediate (primary) repair in which definitive surgery is performed 8 to 12 hours after injury; and early delayed (secondary) repair, which is performed 2 to 6 weeks after initial injury. * * * Delayed (secondary) repair is preferred in cases in which major trauma and contamination are associated with nerve damage. Abolishment of wound contamination and inflammatory response results in a better environment for nerve regeneration. This delay is also biologically compatible with changes in peripheral nerve metabolism and nerve cell body changes described above. Phagocytosis of neurotubular debris and hypertrophy of connective tissue elements allow for immediate initiation of proximal stump regrowth peripherally. Advantages of delaying definitive repair for 2 to 6 weeks after injury include hypertrophy of the epineurium for easier suturing and greater tensile strength, demarcation of injured nerve elements at the site of injury for easier resection of neuroma, and the above-mentioned changes in cell physiology for initiation of regrowth. Disadvantages of secondary repair are stump retraction and neuroma debridement, both of which contribute to increased tension at the site of the suture line, increased tissue fibrosis and hemorrhage in the surgical field, and later return of function."
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This one explains why they chew on their feet:
"The denervated limb must be protected from mutilation until evidence of reinnervation is apparent. Such protection may be provided by padded bandages, splints, or moldable cast material. In some cases, self-mutilation of the denervated portion may be attempted and may be correlated with early stages of axon growth and reinnervation of sensory-deprived areas. Conservative management, accomplished by a protective bandage, side brace, bucket collar, or muzzling, is usually sufficient to prevent further damage. "