Axillary Nerve

NEURAL PATHWAY

The axillary nerve originates from spinal roots C5 and C6.

Spinal roots C5 and C6 → Brachial Plexus (Posterior Cord) → Axillary Nerve

Anatomical location of the axillary nerve relative to the brachial plexus (source)
Anatomical location of the axillary nerve relative to the brachial plexus (source)

After leaving the brachial plexus the axillary nerve will wrap around the humerus and innervate the upper arm.

The axillary nerve will innervate structures of the upper arm (source)
The axillary nerve will innervate structures of the upper arm (source)
FUNCTION

Motor Function:

Abduction of the arm: this nerve will innervate the deltoid muscle which controls abduction of the arm.

Sensory Function:

Upper arm sensation: the axillary nerve controls sensory innervation of the upper arm (depicted more below).

Pattern of radial nerve sensory innervation (source)
Pattern of radial nerve sensory innervation (source)
CAUSE OF INJURY

Shoulder dislocation: particularly anterior-inferior dislocations of the shoulder joint can damage this nerve.

Compression of the axilla such as with a crutch.

Humerus fracture: specifically a fracture of the surgical neck of the humerus can damage this nerve.

This X-ray film shows a fracture of the surgical neck of the humorous. It is this type of injury that can often affect the axillary nerve (source)
This X-ray film shows a fracture of the surgical neck of the humorous. It is this type of injury that can often affect the axillary nerve (source)
CLINICAL PRESNENTATION

Sensory loss in the distribution of innervation outlined above (lateral aspect of upper arm)

Inability to abduct the arm between 15-90° (range controlled by the deltoid muscle).

ARCHIVE OF STANDARDIZED EXAM QUESTIONS

This archive compiles standardized exam questions that relate to this topic.

 

 

Page Updated: 08.21.2016