Most brachial plexus injuries result from excessive stretching of various degrees. The force applied to the injured nerves determines the extent of damage, and defines whether the injury will heal spontaneously (without surgical intervention). The severity of a brachial plexus injury is determined by the type of nerve damage.
1. Neurapraxia, or stretch injury, is the mildest form of nerve injury. It involves a temporary interruption of the nerve conduction due to an injury of the nerve protective covering, without damage to the nerve underneath. Normally, these injuries heal on their own, usually within three months. Complete recovery is expected.
2. Axonotmesis involves the loss of nerve (axon) continuity with preservation of the nerve sheaths. Wallerian degeneration follows this type of injury. It involves degeneration of severed axons from the site of the injury distally to the muscles and sensory organs. The recovery process requires the regrowth of nerve fibers from the site of the injury supported by the retained nerve sheaths. The nerve recovery is usually observed at a rate of three cm per month. The recovery period in brachial plexus injuries can be excessively long, as the affected organs (muscles and sensory organs in the hand) can be as far as 80 cm from the site of the injury. Denervated muscles undergo changes (atrophy) and can be permanently lost in one or two years. The muscles which are furthest away from the site of the injury might not be functional even after nerve regeneration is completed. A spontaneous recovery of function in cases of axonotmesis depends on the extent of the injury, as well as the distance of the target organs from the site of the injury.
3. The most severe form of injury is a complete disruption of the nerve (neurotmesis) or a detachment (avulsion) of the nerve roots from the spinal cord. In cases of complete rupture or avulsion of nerves, spontaneous recovery is not expected. Surgery is the only available option to return nerve function.
Brachial plexus injuries usually present with a complex pattern. There are often various types of injuries at different levels of the brachial plexus. There is no “typical” brachial plexus patient. In the early stages following the injury, clinical examination is needed to assess the extent and location of the brachial plexus injury. The diagnostic process often involves imaging techniques and electrophysiological tests. Usually the examination has to be repeated at certain intervals to finally decide if an operation is needed as there is no potential for spontaneous improvement. A surgical treatment plan is designed for each individual patient. An appropriate combination of procedures must be chosen and performed in a timely manner to achieve the best possible recovery of function.