Neonatal brachial nerve injuries can occur during a difficult delivery when the infant's head and neck are pulled toward the side while the shoulders are passing through the birth canal.
The condition can also be caused by excessive traction on the shoulders during a vertex delivery (head first) or by pressure on the raised arms during a breech delivery (feet first).
The infant may have varying degrees of arm paralysis:
- brachial plexus injuries typically affect only the upper arm
- Erb's paralysis affects the upper arm and rotation of the lower arm
- Klumpke paralysis affects the hand (the infant may also have an eyelid droop on the opposite side)
The incidence of brachial palsy has decreased with improved delivery techniques and the more prudent use of C-sections (caesarian birth, where the baby is removed surgically through the abdomen). Risk factors include a larger than average newborn (large for gestational age -- LGA), shoulder dystocia, and breech delivery. Arm and shoulder fractures can also affect this same population of newborns and the symptoms may be very similar, although the long-term prognosis is very different.
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