The
brachial plexus is a network of
nerves that conducts signals from the
spinal cord, which is housed in the
spinal canal of the
vertebral column (or spine), to the
shoulder, arm and hand. These nerves originate in the fifth, sixth, seventh and eighth cervical (C5-C8), and first thoracic (T1) spinal nerves, and innervate the muscles and skin of the chest, shoulder, arm and hand. Brachial plexus injuries, or lesions, are caused by damage to those nerves
"The brachial plexus may be injured by falls from a height on to the side of the head and shoulder, whereby the nerves of the plexus are violently stretched....The brachial plexus may also be injured by direct violence or gunshot wounds, by violent traction on the arm, or by efforts at reducing a dislocation of the shoulder joint".
Signs and symptoms may include:
- limp or paralyzed arm
- Lack of muscle control in the arm, hand, or wrist
- Lack of feeling or sensation in the arm or hand.
Although several mechanisms account for brachial plexus injuries, the most common is nerve compression or stretch.
Infants, in particular, may suffer brachial plexus injuries
during delivery and these present with typical patterns of weakness, depending on which portion of the brachial plexus is involved.
The most severe form of injury is
nerve root avulsion, which results in complete weakness in corresponding muscles. This usually accompanies high-velocity impacts that occurs during
motor vehicle or bicycle accidents 
