Nerve injury classification (MRI)

Last revised by Henry Knipe on 21 May 2022

Nerve injury classification describes the various features of nerve injury on MRI with respect to pathological events.


  • neuropraxia
    • grade I:
      • there is increased T2/STIR signal in the nerve, however, the muscle appears normal
      • recovery occurs within a few days to 3 months
  • axonotmesis
    • grade II:
      • increased T2/STIR signal in nerve and muscle (pathologically there is myelin and axonal injury but the endoneurium is intact)
      • full recovery can occur but at a slower rate
    • grade III: 
      • enlargement of nerve fascicles which corresponds pathologically to myelin and axonal injury with involvement of endoneurium but intact perineurium
      • recovery can be slow and depends on the amount of scarring and fascicular involvement
    • grade IV:
      • neuroma in continuity, disruption of nerve fascicles results in the inability of regenerating nerve to reach distal targets, pathologically there is myelin and axonal injury with the involvement of endoneurium and perineurium but epineurium is intact
      • spontaneous recovery does not occur and surgical intervention with grafting is required
  • neurotmesis
    • grade V:
      • complete disruption of continuity of nerve with or without hemorrhage and fibrosis in the gap, the muscle shows hyperintensity but with time atrophies and undergoes fatty replacement
      • prognosis is considered poor and surgical intervention is required

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