The brachial plexus is a bundle of nerves that exits the spinal cord at the level of the neck. It travels under the collarbone, passes through the axilla (arm pit), and then separates into the major nerves that supply motor and sensory function to the upper extremity. The brachial plexus is most often injured during childbirth when a large baby travels down a small birth passage, and the baby's shoulder gets stuck on mom's pubic bone. This causes the shoulder to be stretched away from the head. In the process, the nerves of the brachial plexus may be stretched, torn, or avulsed (pulled out of the spinal cord). This results in impaired motor and sensory function of the affected arm.
If nerves are torn or avulsed, microsurgery techniques can be used to repair them.
The oucomes are dependent on the severity of the injury. Stretched nerves often return to normal function with no intervention at all. Torn and avulsed nerves represent a more serious injury, but microsurgery techniques and physical/occupational therapy return more patients to near-normal function than ever before.