Nerve injuries — upper limb

Exercise 4 covers the brachial plexus: definition, formation, trunks, cords and major branches. Exercises 5–6 add the topography of the ulnar, median and radial nerves. These lesions are where that anatomy gets examined.

The plexus, in the order it forms

Roots      C5   C6   C7   C8   T1        (rami of spinal nerves)
            \   /     |     \   /
Trunks      UPPER    MIDDLE   LOWER
            /   \    /   \    /   \
Divisions  ant  post ant post ant post     (each trunk splits)
             \    \___\___\___/    /
Cords      LATERAL   POSTERIOR   MEDIAL    (named for the axillary artery)
              |          |          |
Branches   Musculocut.  Axillary   Ulnar
           + lat. root  Radial     + med. root
                \____ MEDIAN ____/

Every posterior division goes to the posterior cord, and the posterior cord supplies extensors. That single fact predicts most of the motor findings below.

The five terminal nerves

Plexus lesions

Diagnosis drill

A presentation, five nerves. This is how the clinical MCQs are framed.