Axonotmesis

Seddon's intermediate grade of nerve injury: the axons are interrupted and undergo Wallerian degeneration, but the connective-tissue framework of the nerve is preserved to a varying degree. Sunderland subdivides it into second, third and fourth degrees according to whether the endoneurium and perineurium survive; recovery ranges from complete (second degree) to poor without surgery (fourth degree).

Related terms

• Condition

  Neurapraxia

  The mildest grade of nerve injury (Seddon; Sunderland first degree): segmental demyelination with the axon and connective-tissue sheaths intact, usually from compression. It produces a focal conduction block with preserved conduction distal to the lesion and no Wallerian degeneration; recovery is complete, typically within about twelve weeks, once remyelination occurs.

• Condition

  Neurotmesis

  Seddon's most severe grade of nerve injury (Sunderland fifth degree): complete transection of the nerve, its axons and all connective-tissue layers. No useful spontaneous recovery is possible; the nerve must be repaired, grafted or bypassed by a nerve transfer.

• Glossary

  Sunderland classification

  Sunderland's 1951 five-degree classification of nerve injury by the connective-tissue layer lost: first degree (neurapraxia), second (axon only, endoneurium intact — full recovery), third (endoneurium disrupted — partial recovery), fourth (perineurium disrupted — usually needs surgery) and fifth (complete transection). Mackinnon and Dellon added a sixth degree for mixed injuries.

Articles mentioning this term

1. FESSH preparation · 26 September 2026

   Peripheral nerve injury and repair

   Peripheral nerve injury for FESSH candidates: degeneration, Seddon and Sunderland grades, electrodiagnosis, timing, grafts, conduits and nerve transfers.

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