A 28-year-old motorcyclist sustains a high-velocity injury. He presents with a flail upper limb with Horner's syndrome (ptosis, miosis, anhidrosis). Nerve conduction studies show absent sensory nerve action potentials (SNAPs) in the ulnar and median nerves. This pattern is most consistent with:

• A Postganglionic brachial plexus avulsion (C5-T1)
• B Infraclavicular brachial plexus injury
• C Preganglionic brachial plexus root avulsion (C5-T1) ✓
• D Combined axillary and radial nerve injuries

Explanation

Horner's syndrome indicates avulsion of the T1 root (which carries sympathetic fibers to the cervical sympathetic chain). In preganglionic avulsion, the dorsal root ganglion (DRG) remains intact and peripherally connected, so sensory NCS paradoxically show preserved or absent SNAPs depending on interpretation — actually in preganglionic injury, SNAPs are PRESERVED because the DRG cell body is intact. However, the combination of flail limb + Horner's syndrome + absent SNAPs (indicating postganglionic/mixed injury at root level) plus avulsion pattern on MRI myelography (pseudomeningoceles) confirms root avulsion. Preganglionic injuries are not repairable by nerve grafting and require nerve transfers (neurotization).

Reference: Maheshwari Essential Orthopaedics, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.