A 28-year-old motorcyclist sustains a high-velocity shoulder injury. Examination reveals complete flail upper limb. Horner's syndrome is present on the ipsilateral side. Electromyography shows preserved paraspinal muscle activity. The most likely injury is:

• A Post-ganglionic C5–C8 brachial plexus rupture
• B Pan-plexus avulsion (C5–T1 nerve root avulsions) ✓
• C Infraclavicular brachial plexus injury with subclavian artery rupture
• D Preganglionic C5–C6 with postganglionic C7–T1 injury

Explanation

Horner's syndrome (ptosis, miosis, anhidrosis) indicates T1 root involvement at the stellate ganglion level — a preganglionic (avulsion) pattern. Preservation of paraspinal EMG activity would be expected in post-ganglionic injuries; when paraspinal muscles are denervated, this confirms root avulsion because these muscles are innervated by the dorsal primary rami proximal to the plexus formation. A flail limb with Horner's, absent paraspinal signal, and high-velocity mechanism indicates pan-plexus avulsion.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

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Written and medically reviewed by the StethoPrep medical team.