Question

Pathological anatomy of axonotmesis does NOT include

• A. Disruption of myelin sheath
• B. Disruption of perineurium and epineurium
• C. Wallerian degeneration
• D. Axonal regeneration and complete recovery

Hint:

Recall Seddon's three grades of nerve injury and which one promises a full, rapid recovery.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
This is a Seddon's classification of nerve injury question. It asks which listed feature is NOT part of the pathological picture of axonotmesis, the intermediate grade of nerve injury between neurapraxia and neurotmesis.

Step 2: Key Concept or Approach:
In axonotmesis, the axon and its myelin sheath are physically disrupted at the site of injury, and this is followed by Wallerian degeneration of the distal segment. The supporting connective-tissue tubes largely stay in continuity, which is why regenerating axon sprouts can find their way back down the original endoneural tube at roughly one millimetre a day. Recovery in axonotmesis is therefore possible without surgery, but because some sprouts still get misdirected into the wrong tubes and regrowth is slow, the recovery is usually good rather than truly complete. A full, rapid, and complete recovery is the hallmark of the milder neurapraxia, not axonotmesis.

Step 3: Working Through the Options:
Disruption of myelin sheath happens in axonotmesis because the axon itself is interrupted at the injury site. Wallerian degeneration is a defining and expected feature distal to the site of an axonotmesis injury. Disruption of perineurium and epineurium describes the connective-tissue architecture around the nerve fascicles, which is a separate structural point from the outcome being tested here. Axonal regeneration and complete recovery combines two ideas: regeneration does occur, but pairing it with a guarantee of complete recovery overstates what axonotmesis reliably produces, since some regenerating fibres are misdirected and function is often good but incomplete.

Step 4: Conclusion:
The correct answer is axonal regeneration and complete recovery. Axonotmesis allows regeneration and usually a good recovery, but not one that is reliably complete.