Erb's Palsy is unusual in that it specifically affects the arms. The C5 and C6 nerves in the brachial plexus are badly damaged or severed completely, which leads to mobility problems in the arms. Different types of nerve damage can occur: Neuropraxia - The nerve is stretched but not torn. Neuroma - The nerve is stretched and damaged, which may lead to scarring. Rupture - The nerve is torn and cannot heal naturally. Avulsion - The nerve is pulled away from the spinal cord completely. The lasting impact is greater with ruptures and avulsions, where natural healing cannot occur, and nerve grafts may be required to prevent total paralysis of the arm muscles.
Cases, where the fingers are also paralysed, are known as global brachial plexus birth palsy or total brachial plexus birth palsy - they are technically not Erb's Palsy, although the causes are the same.