Following a closed humeral shaft fracture, a patient develops wrist drop (radial nerve palsy). The clinical feature that most strongly indicates the nerve injury is a neurapraxia (Sunderland grade I) rather than a more severe axonotmesis or neurotmesis is:

• A Complete absence of wrist extension and finger extension at time of injury
• B Spontaneous recovery of motor function beginning within 6–12 weeks, with recovery rate consistent with Tinel's sign progressing distally at 1 mm/day ✓
• C Presence of Wallerian degeneration on nerve conduction studies at 3 weeks
• D Sensory loss in the first web space

Explanation

Neurapraxia (Sunderland grade I / Seddon's neurapraxia) involves focal demyelination without axonal disruption; nerve conduction is blocked at the injury site but axonal continuity is preserved. Recovery occurs within 6–12 weeks as remyelination proceeds; nerve conduction returns proximally to distally at approximately 1 mm/day (regeneration/remyelination rate) and Tinel's sign should not progress distally (since axons are intact). Wallerian degeneration on NCS (seen at 3 weeks post-injury) indicates axonal disruption (axonotmesis/neurotmesis — Sunderland II–V), not neurapraxia. Clinical severity at presentation (complete motor/sensory loss) is the same for all grades and does not differentiate them.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

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Written and medically reviewed by the StethoPrep medical team.