Brachial plexus lesions indicate a stretching, compression or tear of the brachial plexus. The Mayo Clinic describes the brachial plexus as the system of nerves that transmit signals from the spine to extremities such as the shoulders, arms and hands.
According to the Mayo Clinic, brachial plexus injuries usually occur when the shoulder is pushed downwards with a high degree of force while at the same time the head and neck are pushed away from the shoulder. Medscape states that the injury commonly occurs in high-contact sports like football and can also occur as the result of high-impact accidents or falls. Treatment generally involves rest, but in severe cases surgery is required, according to Medscape.