The axillary nerve supplies the deltoid and teres minor muscles. It is most commonly damaged as a result of dislocation of the shoulder or of its treatment. It may also be involved in a brachial neuritis.
Clinical features include:
- loss of sensation over a small area of skin on the lateral aspect of the upper arm - the so called sergeant's stripes because of their position.
- loss of function of the deltoid muscle, characterised by an inability to initiate abduction of the arm from a position of zero abduction - this is a chronic sign. Wasting is also seen after time - with flattening of the curved shape of the shoulder.
Treatment is by splinting in a position of abduction at the shoulder.