Superior lateral brachial cutaneous nerve

At a glance

English

Superior lateral brachial cutaneous nerve

Latin (TA2)

Nervus cutaneus lateralis posterioris femoris

System

Nerve

Region

Upper limb

Side

Paired, left and right

About the superior lateral brachial cutaneous nerve

This small nerve is the sensory end of the axillary nerve. The axillary nerve leaves the posterior cord of the brachial plexus, passes backwards through the quadrangular space with the posterior circumflex humeral artery, and divides behind the surgical neck of the humerus into an anterior and a posterior branch. The posterior branch supplies teres minor and the back of deltoid, and then, after piercing the deep fascia, continues as this cutaneous nerve. It carries fibres from C5 and C6.

The nerve turns round the posterior border of the deltoid, near the lower part of the muscle, and spreads in the subcutaneous tissue on the lateral side of the arm. Its territory is the skin covering the lower half to two-thirds of the deltoid, the area that would be covered by a regimental badge on a sleeve, and some of the skin over the long head of triceps. Below, its area meets that of the inferior lateral cutaneous nerve of the arm, a branch of the radial nerve, and behind, that of the posterior cutaneous nerve of the arm.

This patch of skin is the standard place to test the axillary nerve, and with it the C5 dermatome. Because the cutaneous nerve is the final part of the axillary nerve, numbness here suggests that the parent nerve has been injured somewhere along its course round the humerus.

The axillary nerve is at risk in dislocation of the shoulder, in fractures of the surgical neck of the humerus and from badly placed injections into the deltoid. After such injuries, a small numb area on the outer upper arm, sometimes called the regimental badge area, is often the first clue, followed by weakness of shoulder abduction from deltoid paralysis. The skin is usually checked before and after reducing a dislocated shoulder. The cutaneous nerve can also be cut directly by incisions on the lateral side of the shoulder.

Course and supply

Arises from

Continuation of the posterior branch of the axillary nerve (C5, C6) once through the deep fascia at the posterior border of deltoid.

Ends in

Ends in the skin over the lower part of deltoid and the upper part of the long head of triceps.

Supplies

Purely sensory: supplies the skin of the lateral shoulder over the lower deltoid (the regimental badge area).