Peripheral Nerve Injury Classification

What is neurapraxia?

Mildest peripheral nerve injury

What is primarily disrupted in neurapraxia?

Conduction/myelin, while axonal continuity remains intact

Does Wallerian degeneration occur with neurapraxia?

No

What is the prognosis for neurapraxia?

Rapid and complete recovery, typically within weeks

What commonly causes neurapraxia?

Pressure/compression injury

What is damaged in axonotmesis?

Axon is damaged, but supporting connective-tissue structures are preserved enough to allow regeneration

Does Wallerian degeneration occur with axonotmesis?

Yes — distal to lesion

Can axonotmesis regenerate?

Yes

What is the approximate rate of peripheral nerve regeneration?

~1 mm/day

Common causes of axonotmesis?

• Traction
• Compression
• Crush injury

What is neurotmesis?

Most severe peripheral nerve injury

What structures are damaged in neurotmesis?

Axon + myelin + connective tissue are severely disrupted/transected

Does neurotmesis spontaneously recover?

No

What clinical findings occur distal to neurotmesis?

Complete motor and sensory loss

What is generally required for neurotmesis?

Surgical repair/reattachment

Compare neurapraxia, axonotmesis, and neurotmesis.

Neurapraxia
→ Myelin/conduction block
→ Axon intact
→ No Wallerian degeneration
→ Best recovery

Axonotmesis
→ Axon disrupted
→ Supporting structures relatively preserved
→ Wallerian degeneration
→ Regeneration ~1 mm/day

Neurotmesis
→ Complete nerve disruption
→ Worst injury
→ No spontaneous recovery
→ Usually requires surgery

Think:

N → A → N = Mild → Moderate → Severe