Peripheral Nerve Injury (PNI): Classification & Clinical Features
Neuromuscular Orthopedics: Seddon & Sunderland Classifications
1. Seddon Classification
| Type | Pathology | Prognosis |
|---|---|---|
| Neuropraxia | Conduction block (myelin injury). | Excellent; full recovery in days/weeks. |
| Axonotmesis | Axon damaged; endoneurium intact. | Good; Wallerian degeneration occurs. |
| Neurotmesis | Complete nerve transection. | Poor; requires surgical repair. |
2. NEET High-Yield Pearls
- Wallerian Degeneration: Occurs in both Axonotmesis and Neurotmesis. It is the distal degeneration of the axon and myelin sheath after transection.
- Regeneration Rate: The rule of thumb is approximately 1 mm/day or 1 inch/month.
- Tinel’s Sign: A tingling sensation produced by percussion of a regenerating nerve tip. It moves distally as the nerve regenerates.
- Clinical Assessment: Always test motor function first, followed by sensory testing (two-point discrimination, light touch). Electromyography (EMG) and Nerve Conduction Studies (NCS) are the gold standards for diagnostic localization.
- Surgical Timing: If no clinical improvement is seen, surgical exploration is typically considered after 3 months (in open injuries, it is immediate).