Brachial Plexus Injury

The brachial plexus is the network of nerves running from the neck into the shoulder that controls the shoulder, arm, elbow and hand. When it is damaged the arm loses power, movement reduces and in severe cases the limb hangs still.

In newborns the injury happens during delivery — shoulder dystocia, a prolonged or instrumental delivery, or high birth weight. It is a consequence of the birth process, not of anything a parent did. In adults it usually follows a motorcycle accident, a fall onto the shoulder or a penetrating injury.

The clearest sign in a newborn is asymmetry: the baby moves one arm noticeably less than the other. The arm may lie limp and close to the body, the shoulder may not lift, and grip on that side may be weak.

Any persistent asymmetry of arm movement in a newborn should be assessed rather than watched. Diagnosis is clinical, supported where needed by EMG and imaging.

The underlying problem is a break in the signal between nerve and muscle. Nerves recover slowly, and while they do, the muscles they supply waste and the shoulder joint stiffens. If the joint is allowed to contract, function will be limited later even if the nerve recovers well.

Rehabilitation during this window keeps the joint mobile and the muscles active so that returning nerve signal has something to work with. The first three to six months are the critical period 2, and treatment should begin as soon as the diagnosis is made.

Passive and active range-of-movement work to prevent contracture, muscle stimulation, positioning, and — as recovery allows — active movement training. In children this is play-based and delivered largely by the parents, who are trained at each session.

Progress is reviewed on a schedule. Where recovery stalls at the expected milestones, surgical opinion is sought at the point it is still useful rather than after the window has closed. Surgery is needed only in a minority of cases.

A stretched nerve that remains in continuity often recovers substantially. A nerve torn from the spinal cord does not recover on its own and needs surgical assessment early.

Distinguishing these is what examination and, where needed, imaging and nerve studies achieve — and the distinction changes everything about what is offered.

While the nerve recovers, the shoulder is at risk of losing range and the joint of deforming. In infants this can produce a permanent internal rotation contracture that is harder to treat than the original weakness.

Daily range-of-movement work, positioning and, in adults, support for the shoulder against traction are what protect the joint during the months of waiting.