MSI ANATOMY LAB 9: CLNICAL CASES Axilla, Brachial Plexus, and Posterior Triangle of Neck

Case 1: Several weeks after returning home following surgical dissection of her right axilla for the removal of lymph nodes for staging and treatment of her breast cancer, a 44-year-old woman was told by her husband that her right scapula protruded abnormally when she pushed against the wall during her stretching exercises. She also experienced difficulty in raising her right arm above her head when she was combing her hair. During her return visit with her surgeon, she was told that a nerve was accidentally injured during the diagnostic surgical procedure and that this produced her scapular abnormality and inability to raise her arm normally. What nerve was injured?

Case 2: A 20-year-old man complained that he was unable to raise his right upper limb. He held it limply at his side with his forearm and hand pronated. During questioning by the physician, he stated that he had been thrown from his motorcycle approximately 2 weeks previously and that he had hit his shoulder against a tree. He also recalled that his neck felt sore shortly after the accident. On examination, it was found that the patient was unable to flex, abduct, or laterally rotate his arm. In addition, he lost flexion of the elbow joint. A lack of sensation was detected on the lateral surface of his arm and forearm. What is the diagnosis?

The answers to the cases begin on the next page.

Clinical Case Answers

Answer: Iatrogenic injury of long thoracic nerve

Explanation: The long thoracic nerve to the serratus anterior was obviously injured. During axillary dissection, it is normally identified and maintained against the thoracic wall while the lymph nodes are excised. However, the nerve may be accidentally damaged during removal of nodes. Injury to the long thoracic nerve causes paralysis of the serratus anterior, the muscle that keeps the medial border of the scapula in firm apposition with the thoracic wall. The serratus anterior, also powerful, assists the trapezius in rotating the scapula laterally and superiorly when raising the arm over the shoulder. This explains why the patient had difficulty combing her hair. Injuries to the long thoracic nerve and paralysis of the serratus anterior frequently result from weapons (knives, gunshots); however, they may occur during severe automobile accidents, or when a person is run over by a motor vehicle. Scapular fractures and injury to the long thoracic nerve are usually associated with rib fractures. The thoracodorsal nerve (nerve to latissimus dorsi) is in danger during operations on the inferior part of the axilla. The nerve runs inferolaterally along the posterior wall of the axilla and enters the latissimus dorsi at the level of the 2nd and 3rd ribs. A person with paralysis of latissimus dorsi would have difficulty adducting the arm and rotating it medially. During axillary dissections, care must also be taken to avoid injury to the pectoral nerves supplying the pectoralis major. Paralysis of this muscle would seriously affect adduction and weaken medial rotation of the arm. The intercostobrachial nerves, the lateral cutaneous branches of the 2nd intercostal nerve, sometimes have to be sacrificed in radical axillary dissections because these nerves pass close to the axillary lymph nodes to reach the arm. Injury to these nerves causes anesthesia of the skin of the axilla and the posteromedial aspect of the arm.

Source: Moore KL, Dalley AF. Clinically Oriented Anatomy, 4th ed. Baltimore: Lippincott Williams & Wilkins, 1999, Case 6.3.

Answer: Erb-Duchenne palsy

Explanation: When the young man was thrown from his motorcycle and hit a tree, his right shoulder was pulled violently away from his head. This pulled on the superior trunk of his brachial plexus, stretching or tearing the ventral primary rami of C5 and C6 spinal nerves. As a result, the nerves arising from these rami and the superior trunk are affected and the muscles supplied by them are paralyzed. The muscles involved would be the deltoid, biceps brachii, brachialis, brachioradialis, supraspinatus, infraspinatus, teres minor, and supinator.

The patient’s arm was medially rotated because the infraspinatus and teres minor (lateral rotators of the shoulder) were paralyzed. His forearm was pronated because the supinator and biceps were paralyzed. Flexion of his elbow was weak because of paralysis of the brachialis and biceps brachii. The inability of the patient to flex his humerus resulted from paralysis of the deltoid and coracobrachialis and probably the clavicular head of the pectoralis major. Loss of abduction of the humerus resulted from paralysis of the supraspinatus and deltoid. The paralysis of his limb muscles would be permanent if the nerve rootlets forming the C5 and C6 rami were pulled from the spinal cord and not surgically reconnected in a timely manner. If not, the axons of the nerves would not regenerate and the muscles supplied by them would soon undergo atrophy (wasting). Movements of the shoulder and elbow would be greatly affected; for example, the person will always have difficulty lifting a glass to his mouth with his right arm. The loss of sensation in his arm resulted from damage to sensory fibers of C5 and C6 that are conveyed in the upper lateral brachial cutaneous nerve (from the axillary nerve), the lower lateral brachial cutaneous nerve (from the radial nerve), and the lateral antebrachial cutaneous nerve (from the musculocutaneous nerve).

Source: Moore KL, Dalley AF. Clinically Oriented Anatomy, 4th ed. Baltimore: Lippincott Williams & Wilkins, 1999, Case 6.16.