Axillary Nerve

A 45-year-old man, a chronic user of a crutch went to his family physician and complained that he had noticed a loss of shoulder contour on the right side during the last 2 months. He also told me that he feels no sensations in this region and could see the bony projection at the upper end.

On examination, the physician found that the patient could not abduct his arm up to 90° and there was a loss of skin sensation. Over the lower hall of the deltoid muscle. He could also notice the prominence of the greater tubercle of the humerus. He was diagnosed as a case of axillary nerve injury.

Questions

1. Mention the origin and root value of the axillary nerve.
2. What are the three common causes of axillary nerve injury?
3. Mention the cause of loss of skin sensation over the lower half of the deltoid.
4. What is the cause of loss of shoulder contour and prominence of greater tubercule humerus?
5. Name the muscles supplied by the axillary nerve.

Answers

1. The axillary nerve arises from the posterior cord of the brachial plexus (C5 and C6).
2. The axillary nerve can be injured
   • By the pressure of a badly adjusted crutch, pressuring upwards, into the armpit
   • By inferior dislocation of the shoulder joint
   • By the intramuscular injection
3. Due to involvement of the upper lateral cutaneous nerve of the arm.
4. Due to wasting of the deltoid muscle.
5. Deltoid and teres minor.