Brachial plexus: A network of spinal nerves that originates in the back of the neck, extends through the axilla (armpit), and gives rise to nerves to the upper limb. The brachial plexus is formed by the union of portions of the fifth through eighth cervical nerves and the first thoracic nerve, all of which come from the spinal cord.

Injuries to the brachial plexus affect the nerves supplying the shoulder, upper arm, forearm and hand, causing numbness, tingling, pain, weakness, limited movement, or even paralysis of the upper limb. Although injuries can occur at any time, many brachial plexus injuries happen during birth. The baby's shoulders may become impacted during the birth process, causing the brachial plexus nerves to stretch or tear.

There are four types of brachial plexus injuries:

1. Avulsion, the most severe type, in which the nerve is torn from the spine;
2. Rupture, in which the nerve is torn but not at the spinal attachment;
3. Neuroma, in which the nerve has tried to heal itself but scar tissue has grown around the injury, putting pressure on the injured nerve and preventing the nerve from conducting signals to the muscles; and
4. Neurapraxia or stretch, in which the nerve has been damaged but not torn. Neurapraxia is the most common type of brachial plexus injury.

Treatment depends on the site and type of injury to the brachial plexus and may includes occupational and physical therapy and, in some cases, surgery. Certain brachial plexus injuries heal on their own. Children may improve or recover by 3 to 4 months of age.

The prognosis similarly depends on the site and type of brachial plexus injury determine the prognosis. For avulsion and rupture injuries there is no potential for recovery unless surgical reconnection is made in a timely manner. For neuroma and neurapraxia injuries the potential for recovery varies. Most patients with neurapraxia injuries recover spontaneously with a 90-100% return of function.