brachial plexus birth injury (Erb palsy)
/ BRAY-kee-al PLEK-sus; URB palsy /
During a difficult birth, especially when a baby's shoulder gets stuck behind the mother's pelvic bone, the baby's neck and shoulder can be stretched apart. The bundle of nerves running from the neck into the arm — the brachial plexus — can be overstretched or torn. The newborn is then noticed to have one arm that does not move normally. This birth-related nerve injury is a brachial plexus birth injury, and its commonest form is Erb palsy.
Which movements are lost depends on which nerve roots are stretched. In Erb palsy the upper roots (around C5 to C6) are affected, so the shoulder and elbow are weak while the hand still works. The arm classically hangs in the 'waiter's tip' posture: held at the side, rotated inward, elbow straight, wrist bent. Less commonly the lower roots are injured, weakening the hand (Klumpke palsy), or the whole plexus is hurt. The injuries range in severity from a mild stretch (neurapraxia) that recovers fully, through axon damage, to the worst — a root torn out of the spinal cord (avulsion) that will not recover on its own.
This matters in rehabilitation because most milder cases recover substantially in the first months, but recovery is not automatic and the window to act is real. The early job is to protect the joint and keep it supple: gentle range-of-motion exercises stop the shoulder from stiffening into a fixed contracture while the nerve recovers, and the family is taught to handle the arm. Babies who do not regain key movements (a common benchmark is biceps function returning by a few months of age) are referred for possible nerve surgery, and later tendon or bone surgery may improve a residual deformity. The honest caveat: gentle therapy guides and protects recovery — it does not heal the nerve, and not every arm recovers fully.
A newborn after a difficult delivery holds his right arm limp at his side in the 'waiter's tip' posture. The team teaches the parents gentle daily stretches to keep the shoulder supple and tracks his biceps. It returns by three months and he recovers well — but had it not, they would have referred him early for surgery.
Upper-root Erb palsy gives a 'waiter's tip' arm; early gentle therapy protects the joint while the nerve recovers.
Most milder stretch injuries recover, but recovery is not guaranteed and is time-sensitive: a baby who has not regained key movements (notably biceps) by a few months should be assessed for nerve surgery before the window closes. Therapy protects the joint and guides recovery — it does not heal the nerve itself.