Sunderland Grade V nerve injury is equivalent to Seddon's classification of neurotmesis. What histologically defines it?

• A Local demyelination with intact axon — recovers fully without Wallerian degeneration
• B Axonal disruption but intact endoneurium, perineurium, and epineurium — good spontaneous recovery
• C Complete transection of the entire nerve trunk including all connective tissue sheaths — requires surgical repair ✓
• D Disruption of the endoneurium with intact perineurium and epineurium — partial recovery expected

Explanation

Sunderland Grade V (= Seddon neurotmesis) involves complete division of all nerve elements: axons, endoneurial tubes, perineurium, and epineurium. No spontaneous regeneration can occur because the distal tube architecture is disrupted and proximal axon sprouts cannot navigate to target organs. Surgical repair — either primary neurorrhaphy or nerve grafting (when tension-free repair is not possible) — is required. Recovery is always incomplete. Grade I = neuropraxia; Grade II = axonotmesis with intact endoneurium; Grade III = loss of endoneurium; Grade IV = loss of perineurium.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

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