The brachial plexus is a network of nerves that conducts signals from the spine to the shoulder, arm, and hand. Brachial plexus injuries are caused by damage to those nerves. Symptoms may include a limp or paralyzed arm; lack of muscle control in the arm, hand, or wrist; and a lack of feeling or sensation in the arm or hand. Brachial plexus injuries can occur as a result of shoulder trauma, tumors, or inflammation.
There is a rare syndrome called Parsonage-Turner Syndrome, or brachial plexitis, which causes inflammation of the brachial plexus without any obvious shoulder injury. This syndrome can begin with severe shoulder or arm pain followed by weakness and numbness. In infants, brachial plexus injuries may happen during birth if the baby’s shoulder is stretched during passage in the birth canal.
What happens when the brachial plexus is injured?
The network of nerves is fragile and can be damaged by pressure, stretching, or cutting. Stretching can occur when the head and neck are forced away from the shoulder, such as might happen in a fall off a motorcycle. If severe enough, the nerves can actually avulse, or tear out of, their roots in the neck. Pressure could occur from crushing of the brachial plexus between the collarbone and first rib, or swelling in this area from injured muscles or other structures.
Injury to a nerve can stop signals to and from the brain, preventing the muscles of the arm and hand from working properly, and causing loss of feeling in the area supplied by the injured nerve. When a nerve is cut, both the nerve and the insulation are broken. Pressure or stretching injuries can cause the fibers that carry the information to break and stop the nerve from working, without damaging the cover.
When nerve fibers are cut, the end of the fiber farthest from the brain dies, while the insulation stays healthy. The end that is closest to the brain does not die, and after some time may begin to heal. If the insulation was not cut, new fibers may grow down the empty cover of the tissue until reaching a muscle or sensory receptor.
Some brachial plexus injuries are minor and will completely recover in several weeks. Other injuries are severe enough that some permanent disability involving the arm can be expected.
Many brachial plexus injuries can recover with time and therapy. The time for recovery can be weeks or months. When an injury is unlikely to improve, several surgical techniques can be used to improve the recovery. To help decide which injuries are likely to recover, your physician will rely upon multiple examinations of the arm and hand to check the strength of muscles and sensation. Additional testing, such as an MRI scan, or CT scan/myelography, may be used to visually evaluate the brachial plexus.
A Nerve Conduction Study/Electromyogram (NCS/EMG), a test that measures the electrical activity transmitted by nerves and muscles, may also be performed. In some cases, repair of the nerves or transfer of undamaged nerves from other areas of the body can be performed. In other cases, transfer of functioning muscles (tendon transfer) to take over areas of lost function can be performed.