Study note

Brachial plexus blood supply and Erb's paralysis

THE CONTEXT

The passage describes arterial supply to the brachial plexus and the mechanism, muscle involvement and limb posture of upper trunk injury.

•

The vertebral artery and the thyrocervical trunk contribute to the blood supply of the brachial plexus.

•

The contributing thyrocervical branches are the suprascapular and transverse cervical arteries.

•

Erb's point is a region of the upper trunk where six nerves meet. Upper trunk injury causes Erb's paralysis.

•

The injury results from undue separation of the head from the shoulder, as may occur during birth injury, a fall on the shoulder or anaesthesia.

•

Biceps brachii, deltoid, brachialis and brachioradialis are mainly paralysed. Supraspinatus, infraspinatus and supinator are partly affected.

•

The arm hangs by the side in adduction and medial rotation, while the forearm is extended and pronated.

•

This posture is called waiter's tip hand, policeman's tip hand or porter's tip hand.

•

Abduction and lateral rotation of the arm at the shoulder are lost.

•

Flexion and supination of the forearm are lost.

•

Biceps and supinator jerks are lost.

•

Sensation is lost over a small area covering the lower part of the deltoid.

NEETx

Learn. Practise. Remember.