A patient with a penetrating wound to the axilla has the following findings: inability to abduct the arm past 90° (deltoid and supraspinatus paralysed), loss of arm external rotation, loss of forearm flexion (biceps), and lateral forearm sensory loss. Which component of the brachial plexus is injured?

• A Upper trunk (C5–C6) of the brachial plexus (Erb–Duchenne palsy)
• B Posterior cord and lateral cord of the brachial plexus ✓
• C Lower trunk (C8–T1) of the brachial plexus (Klumpke's palsy)
• D Medial and lateral cords of the brachial plexus

Explanation

The findings — deltoid paralysis (axillary nerve from posterior cord), external rotation loss (suprascapular nerve from upper trunk/posterior cord), biceps loss (musculocutaneous nerve from lateral cord), and lateral forearm sensory loss (lateral cutaneous nerve of forearm from musculocutaneous) — indicate combined posterior cord and lateral cord injury. The posterior cord gives axillary and radial nerves; the lateral cord gives musculocutaneous and lateral root of median nerve. Upper trunk (Erb) palsy would also affect suprascapular nerve but is a trunk-level injury; at axilla level, cord lesions are more precise. Lower trunk (Klumpke) affects intrinsic hand muscles and C8–T1 sensory territory.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.