A patient has a lesion of the posterior cord of the brachial plexus. Which combination of deficits is expected?

• A Claw hand, loss of medial two digits sensation, and wasting of hypothenar muscles — ulnar nerve distribution
• B Loss of flexion at elbow, weakness of pronation, and thenar wasting — median nerve distribution
• C Horner syndrome with weakness of all intrinsic hand muscles
• D Wrist drop, deltoid weakness, and loss of sensation over the 'regimental badge' area — involvement of radial and axillary nerves ✓

Explanation

The posterior cord (formed from posterior divisions of all three trunks: C5–C8, T1) gives rise to the axillary nerve and radial nerve (plus thoracodorsal and subscapular nerves). Axillary nerve injury causes deltoid wasting/weakness (shoulder abduction) and loss of sensation over the lower deltoid ('regimental badge' or 'shoulder badge' area). Radial nerve injury causes wrist drop, finger drop, loss of elbow extension (if proximal), and sensory loss over the dorsum of hand. Combined axillary + radial involvement points to posterior cord lesion.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.