Brachial plexus and peripheral nerve injuries

Key points

1. Roots C5–T1 form trunks, divisions, cords and terminal branches.
2. Upper trunk (C5–C6) injury: arm adducted and internally rotated with an extended elbow ('waiter's tip').
3. Lower trunk (C8–T1) injury: claw hand, sometimes with Horner syndrome.
4. Surgical neck of humerus fracture or shoulder dislocation: axillary nerve (deltoid, regimental badge area).
5. Midshaft humerus fracture: radial nerve in the spiral groove (wrist drop).

Image guide

What to look for in each view of this topic.

1. Overview. Roots, trunks, divisions, cords, branches: the plexus runs from the neck through the axilla.
2. Upper trunk lesion. Traction between head and shoulder at birth or in a motorcycle fall.
3. Lower trunk lesion. Traction of an abducted arm; a Pancoast tumour can also involve it.
4. Long thoracic nerve. Serratus anterior paralysis causes medial winging of the scapula.
5. Median nerve at the wrist. Carpal tunnel syndrome: thenar wasting and numbness of the lateral three and a half digits.
6. Ulnar nerve at the elbow. Cubital tunnel: weakness of intrinsic hand muscles and numbness of the little finger.