The brachial plexus is a network of nerves in the shoulder that carries movement and sensory signals from the spinal cord to the arms and hands. Brachial plexus injuries typically stem from trauma to the neck, and can cause pain, weakness and numbness in the arm and hand. Brachial plexus injuries often heal well if they aren’t severe. Mar 01, · Brachial plexus injury (BPI) is a severe peripheral nerve injury affecting upper extremities, causing functional damage and physical disability 55). The most common cause of adult BPI is a traffic accident, such as motorcycle accidents. Most patients are young men between 15 and 25 years of age 2, 21, 29).Cited by: 3.