Examqo › Examqo library › Orthopedic surgery › Nerve injuries · IMLE
Peripheral nerve injury — Seddon and Sunderland classifications
The Seddon classification divides nerve injury into three grades — neurapraxia (conduction block), axonotmesis (axon torn with intact sheath) and neurotmesis (complete division) — and the grade decides whether recovery will be spontaneous and whether surgery is needed.
Why it matters in the exam
Questions present a patient with weakness or numbness after a fracture, dislocation or laceration and ask for the type of injury and the next step. In neurapraxia only the myelin is damaged, the axon does not degenerate, and recovery is complete within weeks to about 3 months. In axonotmesis the axon is torn but the sheaths are intact, the distal part undergoes Wallerian degeneration, and the axon regrows at about 1 mm per day; progress can be followed with a Tinel sign advancing along the nerve. In neurotmesis the nerve is completely divided and there is no spontaneous recovery without repair. The Sunderland classification details five grades by the layers injured. Nerve conduction studies and EMG show signs of denervation only after about 3 weeks, so they are usually done 3–4 weeks after injury and repeated later. The key practical principle: an open, sharp injury with a nerve deficit is explored and repaired early, whereas a closed injury, such as after a fracture or dislocation, is usually neurapraxia or axonotmesis and is observed; if there are no clinical or electrical signs of recovery after about 3 months, surgical exploration is considered. There is a time limit: motor end plates gradually degenerate, and if the muscle is not reinnervated within about 12–18 months, motor recovery will not return, and then tendon transfers or nerve transfers are considered.
Key points
- Neurapraxia — myelin only; full recovery within weeks.
- Axonotmesis — regrowth of about 1 mm per day; an advancing Tinel sign.
- Neurotmesis — no recovery without repair.
- Sharp laceration — early repair; closed injury — observe and explore after about 3 months without improvement.
- EMG is meaningful only after 3–4 weeks.
Summary table
| Seddon | What is injured | Prognosis | Treatment |
|---|---|---|---|
| Neurapraxia | Myelin only, no axonal degeneration | Full recovery within weeks to about 3 months | Observation and protection of the limb |
| Axonotmesis | Axon torn, sheaths intact | Slow recovery, about 1 mm per day | Observation, Tinel sign and electrical studies |
| Neurotmesis | Complete division of the nerve | No spontaneous recovery | Direct repair or nerve graft |
| Sharp laceration with nerve deficit | Usually neurotmesis | Depends on early repair | Early exploration and repair |
| Closed injury without improvement | Axonotmesis or neurotmesis | Poor if delayed | Exploration after about 3 months without improvement |
In the full version for subscribers
- A simple algorithm
- Memory aid
- Exam traps
- 5 review cards
- Enough for IMLE
The full version is open to subscribers of: Orthopedic surgery, Medical licensing exam (IMLE), Neurosurgery, Plastic surgery.
Subscriber? Read the full topic Plans and prices 25 free questions
Sources
- Green's Operative Hand Surgery, 8th ed. (2022) — Nerve Repair and Nerve Grafting
- Seddon HJ; Sunderland S, Brain (1943; 1951) — Classification of peripheral nerve injury
- Campbell's Operative Orthopaedics, 14th ed. (2021) — Peripheral Nerve Injuries
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.