Medical Overview - Brachial Plexus Injury Australia

Overview of Obstetric Brachial Plexus Injuries

Information courtesy of The BC Childrens Hospital in Vancouvr, British Columbia

How do Obstetric Brachial Plexus Injuries Happen?

Difficult childbirth is the most common cause of a brachial plexus injury in infants.

If the baby’s body is large the shoulders can become trapped after delivery of the head. In order to free the shoulders, the head tilts or is pressed to the opposite side, stretching the nerves in the neck. Tension on the brachial plexus may cause one or more fibers of the nerves to stretch or even pull apart. Additional force on the plexus may rupture nerves entirely or unplug them from the spinal cord.

If the brachial plexus is damaged, weakness in the arm shows up immediately as a paralysis of that part of the arm

What Happens?

There are many degrees of severity in brachial plexus injuries. The first consideration is the amount of injury to the nerve. If the fibers have only been overstretched and not torn, your child should recover complete use of the muscle over the course of a few weeks. However, if the nerves have been torn or ruptured, recovery will take longer. Nerves located outside the spinal cord (peripheral nerves) have a special ability to repair themselves. Nerve sprouts from the cut nerve end can grow across a small gap along with nerve scar and then re‐grow down the rest of the nerve at a rate of about 1mm a day or 1 inch per month. It may take many months for re‐growing fibers to reach the muscles of the lower arm and hand. In some cases there is more nerve scar than nerve fibers getting across the gap and the muscle will not be very strong. If the nerve(s) has been completely unplugged from the cord, it cannot heal itself and the muscles associated with that nerve will not work. In some circumstances, ruptured or unplugged nerves in the brachial plexus can be operated on to increase the number of nerve fibers across the gap with grafts, or to connect up the unplugged nerves into places that will allow healing. Sometimes, extra nerves from outside of the brachial plexus can be added to improve muscle strength.

The second consideration is the number of nerves that have been affected. Of the five nerves of the brachial plexus, the highest two (C5, C6) are most often involved. Weakness or paralysis of the muscles served by these two nerves is called Erb’s palsy. This weakness or paralysis can be seen in how a baby holds the effected arm ‐ arm straight, with the shoulder rotated inward. If, as in some cases, all 5 of the nerves are affected by the injury, weakness or paralysis will affect the entire arm and hand. This poses more problems for recovery.

How do we know the severity?

No single test can determine the exact extent of a brachial plexus injury. On each clinic visit, the brachial plexus team will score active and stretching movements of your child’s arm. This will help determine how the nerves are healing and may help to define the location and severity of the injury. If surgery is recommended, other tests may be requested.