Trauma of peripheral nerves - Brachial plexus injury

Peripheral nerve regeneration

A severed or stretched nerve undergoes a phenomenon of so called Wallerian degeneration, followed by a regrowth called Wallerian regeneration. The fourth month marks a limit not to be exceeded to perform a nerve suture. Axonal regrowth appears 4 to 5 days after section at a rate of 1 to 2 mm per day (about 30 to 60 mm per month). The distance between the site of injury and the targeted muscle is of great importance insofar neurotization of a fibrotic muscle is functionally ineffective. This finding explains the poor results obtained on the plexus in which long distance of regrowth has to be consider.

Lesion classification and surgical indication

Three elementary lesions can be encountered in the peripheral nerve according to the microscopic classification proposed by Seddon (and changed by Sunderland):

• Neurapraxia is a functional impairment of nerve conduction, a conduction, block without histological lesion of the nerve. There not be axonal degeneration nor regrowth.
• Axonotmesis is a section of the axons without rupture of the nerve sheaths surrounding them. Each severed axon can regrow in its initial environment (basal membrane is intact) to its initial target.
• Neurotmesis is a complete section of NP structures. The axon cannot regrowth normaly. The Wallerian regeneration process is inhibited by the scar tissue.

[...]