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Back| Grade | Description |
|---|---|
| First Degree Injury | Conduction block. Continuity of nerve fibers is maintained without Wallerian degeneration. Myelin sheath damage, physiological conduction block along the axon at the injury site, axon not severed. No Wallerian degeneration. No nerve regeneration, no Tinnel's sign (advance of movement). Usually recovers spontaneously within 3-4 weeks. |
| Second Degree Injury | Axon disruption, but the endoneurial tube remains intact, with Wallerian degeneration occurring distally. Axon severed, Wallerian degeneration occurs distally, degeneration of one or more internodes proximally, endoneurial tube remains intact (Schwann cell basement membrane) providing an anatomical pathway for axon regeneration. Can recover spontaneously, axon grows distally at a rate of 1-2mm per day. |
| Third Degree Injury | Transection of nerve fibers (including axons and sheaths), but the fascicular membrane remains intact. Axon and endoneurial tube severed, but the fascicular membrane remains intact. Structural disorganization due to endoneurial tube damage. Possible spontaneous recovery, but often incomplete due to endoneurial scarring. |
| Fourth Degree Injury | Severe damage or transection of the fascicle, but the nerve trunk remains continuous through the epineurium. Fascicular membrane damage, partial preservation of the epineurium and fascicular membrane, preventing nerve trunk transection. Rarely recovers spontaneously, requires surgical repair. |
| Fifth Degree Injury | Complete transection of the entire nerve trunk. Requires surgical repair for recovery. |
Explanation
The third, fourth, and fifth degree injuries in the Sunderland classification correspond to neurotmesis in the Seddon classification, differing only in the extent of nerve damage.