According to Sunderland's classification of peripheral nerve injuries, a Grade 4 injury is distinguished from Grade 3 by:

• A Grade 4 involves axonal loss with intact endoneurium; Grade 3 disrupts the endoneurium
• B Grade 4 is a complete nerve trunk transection; Grade 3 is a partial transection
• C Grade 4 involves demyelination only; Grade 3 involves axonal loss
• D Grade 4 disrupts the perineurium (fascicular disruption) with intact epineurium, while Grade 3 disrupts only the endoneurium ✓

Explanation

Sunderland's 5-grade classification: Grade 1 (neuropraxia — conduction block, no axonal loss), Grade 2 (axonotmesis — axonal disruption, intact endoneurium, good recovery), Grade 3 (endoneurial disruption, perineurium intact — incomplete/poor recovery due to scar), Grade 4 (perineurial disruption, epineurium intact — requires surgery as fascicular architecture lost), Grade 5 (complete nerve transection). Seddon's classification corresponds: neuropraxia = Grade 1, axonotmesis = Grades 2–4, neurotmesis = Grade 5.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

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Written and medically reviewed by the StethoPrep medical team.