Brachial plexus injury occurs during birth, causing paralysis or decreased movement and sensation of the arm muscles. The cause is due to the rupture or dilation of one or all of the ulnar, radial, and median nerves from the brachial plexus due to the procedure of pulling the arm or shoulder when removing the baby.

Electrodiagnostics (commonly known as electromyography, electromyography, neuromuscular electrophysiology) is a functional examination method based on recording the electrical activity of peripheral nerve cells and muscle cells, thereby assessing the functional integrity of the peripheral nervous system and muscles.