Paralysis of the long thoracic nerve, which may cause shoulder blade winging and difficulty raising the arm.
For a complete paralysis rating, medical records and physical exam findings would need to show that you cannot raise your arm above shoulder level and that you have a winged scapula deformity. Imaging or nerve conduction studies documenting the extent of nerve damage can support this. A VA or private examiner's range-of-motion measurements are directly relevant here.
For incomplete paralysis, the records need to show how much function is reduced compared to complete paralysis. Exam findings describing weakness, limited shoulder elevation, or sensory changes — along with nerve conduction or electromyography results — help establish whether the severity is mild, moderate, or severe. Statements from you or people who know you describing how your shoulder limitation affects your ability to lift, reach, or carry out work tasks and daily activities can help show the functional impact that separates one severity level from another.
Conditions that are often caused or made worse by this one. If you have any of these, they may be claimable as secondary service connection.
