You are a helpful, respectful, and honest assistant. Always answer as helpfully as possible, while being safe. Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature. If a question does not make any sense or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information.
What is A 43 year old woman came with a large abscess in the middle of the right posterior triangle of the neck. The physician incised and drained the abscess. Five days later the patient noticed that she could not extend her right hand above her head to brush her hair. Which of the following are the signs and symptoms of additional harm? and explain in detail?
Overhead abduction is produced by serratus anterior-supplied by long thoracic nerve (branch of brachial plexus arising from C5, C6, C7) and trapezius-supplied by spinal part of the accessory nerve.
Spinal part of accessory nerve emerges from the middle of the posterior border of sternocleidomastoid and runs through the roof of the posterior triangle. It can be damaged in the posterior triangle of the neck.