Thoracodorsal nerve

At a glance

English

Thoracodorsal nerve

Latin (TA2)

Nervus thoracodorsalis

System

Nerve

Region

Upper limb

Side

Paired, left and right

About the thoracodorsal nerve

The thoracodorsal nerve, also known as the middle or long subscapular nerve, leaves the plexus's posterior cord between the upper and lower subscapular nerves. It carries fibres from C6, C7 and C8, which reach the posterior cord by way of the posterior division of each trunk. Although latissimus dorsi lies on the back, its nerve comes from the ventral rami like every other limb muscle, because the muscle migrates onto the trunk from the upper limb during development.

From its origin behind the axillary artery the nerve runs downwards and laterally on the axilla's posterior wall, lying on subscapularis and then teres major. It accompanies the subscapular artery and its continuation, the thoracodorsal artery, forming a neurovascular bundle that enters the deep surface of latissimus dorsi a little below the lower edge of teres major. Inside the muscle it branches widely, and its filaments can be followed almost to the muscle's lower edge.

Latissimus dorsi extends, adducts and medially rotates the arm at the shoulder. It pulls the body up towards a fixed arm in climbing and pull-ups and drives the arm down and back in swimming and chopping. It also helps in forced breathing out and in coughing. Loss of the nerve therefore weakens these movements, so that the patient struggles to push up from a chair with the arms or to reach the back pocket.

The nerve is important to surgeons in two ways. During clearance of lymph nodes from the axilla it lies among the tissue being removed and must be identified and kept intact. And latissimus dorsi is one of the most useful muscles for transfer: with the thoracodorsal nerve and vessels preserved, it can be moved as a flap to cover a defect on the chest wall, to restore elbow flexion, or as a free graft with nerve repair for facial reanimation. Damage to the posterior cord takes the nerve with it, adding weak adduction of the shoulder to the effects of radial and axillary injury.

Course and supply

Arises from

Posterior cord of the plexus (C6 to C8), between the upper and lower subscapular nerves.

Ends in

Enters and branches within the deep surface of latissimus dorsi, reaching almost to its lower border.

Supplies

Motor to latissimus dorsi, for extension, adduction and medial rotation of the arm and for raising the trunk on a fixed arm.