Sunderland described a classification of nerve injuries in 1951 that correlates pathological changes with prognosis. The grades are:
- first degree injury:
- demyelinated nerve
- a physiological local conduction block
- neuropraxia in the Seddon scheme
- conservative management
- recovery expected over weeks to months
- second-degree injury:
- some axons disrupted
- endoneurial sheaths and surrounding connective tissue layers remain intact
- Wallerian degeneraiton distally
- equivalent to axonotmesis in Seddon scheme
- treatment is conservative
- regeneration of axons can be followed clinically by an advancing Tinel's sign
- complete recovery can be expected over months
- third-degree injury:
- axons and endoneurial sheaths disrupted
- scarring replaces existing structures
- perineurium and connective tissue layers outside of this remains
- most of these injuries will recover spontaneously but partially
- fourth-degree injury:
- axon, endoneurium and perineurium disrupted
- scarring replaces existing structures
- epineurium remains
- scar blocks all neuronal regeneration
- no recovery likely without operative management
- fifth-degree injury:
- nerve transection
- all structures including epineurium divided
- no recovery expected without operative management
Sixth-degree injury was subsequently added to the scheme by Susan Mackinnon. This describes a nerve injury with features of two or more of the above categories.