Anatomy clinical correlates: Axilla

00:00 / 00:00


Anatomy clinical correlates: Axilla

USMLE® Step 1 questions

0 / 5 complete

USMLE® Step 2 questions

0 / 1 complete


USMLE® Step 1 style questions USMLE

of complete

USMLE® Step 2 style questions USMLE

of complete

A 46-year-old woman presents to her primary care physician to evaluate left-sided shoulder pain and weakness for two weeks. The patient had a recent axillary lymph node dissection for breast cancer surveillance. Vital signs are within normal limits. The patient has normal sensation in the upper extremities on physical exam with 5/5 strength bilaterally. When asked to cross her arms, a notable physical examination finding is demonstrated in the image below. Which of the following anatomic structures is responsible for this patient’s symptoms?  

Image credit: wikipedia  


The axilla, also known as the armpit, is first and foremost, incredibly ticklish. But from an anatomical standpoint, it’s a key location that contains many important structures that may be damaged, causing significant functional deficits. The axilla is like a train station, where a number of vascular, nervous and lymphatic structures pass between the trunk and the upper limb.

One very important structure is the brachial plexus, which can be divided into five roots, three trunks, six divisions, three anterior and three posterior cords, and five terminal branches. The order can be remembered using the mnemonic “Remember To Drink Cold Beer.” But you may want to wait until the end of the video before you act on that!

Now, an upper brachial plexus injury affects the superior roots, namely spinal nerves C5 and C6, and a classic example of an upper brachial plexus injury is Erb palsy, which can happen in adults as a shoulder trauma that results in an increase in the angle between the neck and the shoulder, or in newborns, when excessive stretching of the neck occurs during childbirth.

The clinical consequences reflect the affected nerves, which are the ones that are derived solely from C5 and C6 roots, namely, the musculocutaneous, axillary, and suprascapular nerves. This causes paralysis of muscles like the biceps brachii, which normally allows forearm flexion and supination, and the infraspinatus and teres minor, so lateral rotation of the arm is affected, as well as the deltoid and supraspinatus muscles, which would usually cause arm abduction but would also be affected. So with superior brachial plexus injuries, the classic finding is a “waiter’s tip position”, which reflects arm adduction and medial rotation, and forearm extension and pronation.


  1. "The Encyclopedia of Skin and Skin Disorders" NA (2007)
  2. "D'scent of man: A comparative survey of primate chemosignaling in relation to sex" Hormones and Behavior (2015)
  3. "Principles of Anatomy and Physiology" HarperCollins Publishers (1990)
  4. "The Atlas of the Human Body" NA (2002)
  5. "Thoracic Outlet Syndrome" Journal of the American Academy of Orthopaedic Surgeons (2015)
  6. "Scapular winging: anatomical review, diagnosis, and treatments" Current Reviews in Musculoskeletal Medicine (2007)
  8. "Augusta Déjerine-Klumpke: the first female neuroanatomist" Clin Anat (2007)
  9. "Body contouring of the arms and brachioplasty" Handchir Mikrochir Plast Chir (2007)
  10. "Regional anatomy" Galen (undefined)

Copyright © 2023 Elsevier, its licensors, and contributors. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

Cookies are used by this site.

USMLE® is a joint program of the Federation of State Medical Boards (FSMB) and the National Board of Medical Examiners (NBME). COMLEX-USA® is a registered trademark of The National Board of Osteopathic Medical Examiners, Inc. NCLEX-RN® is a registered trademark of the National Council of State Boards of Nursing, Inc. Test names and other trademarks are the property of the respective trademark holders. None of the trademark holders are endorsed by nor affiliated with Osmosis or this website.