Nerve injury classification assists in prognosis and determination of treatment strategy for nerve injuries. Classification was described by Seddon in 1943 and by Sunderland in 1951.[1] In the lowest degree of nerve the nerve remains intact, but signaling ability is damaged, termed neurapraxia. In the second degree the axon is damaged, but the surrounding connecting tissue remains intact – axonotmesis. The last degree, in which both the axon and connective tissue are damaged, is called neurotmesis.
In 1943, Seddon described three basic types of nerve injury:[2]
See main article: Neurapraxia. Neurapraxia is a temporary interruption of conduction without loss of axonal continuity.[3] Neurapraxia involves a physiologic block of nerve conduction in the affected axons.
Other characteristics:
See main article: Axonotmesis. Axonotmesis involves loss of relative axon continuity and myelin covering, but preservation of the connective tissue framework (including encapsulating tissue, the epineurium and perineurium).[5]
Other characteristics:
See main article: Neurotmesis. Neurotmesis is total severance/disruption of the nerve fiber.[6] Axon, endo-, peri-, and epineurium transected. Neurotmesis may be partial or complete.
Other characteristics:
In 1951, Sunderland expanded Seddon's classification to five degrees. The first two are the same as Seddon's.
Sunderland's third-degree and fourth-degree are included within Seddon's axonotmensis. Sunderland's third-degree is nerve fiber interruption. Includes an endoneurium lesion, with an intact epineurium and perineurium. Recovery from a third-degree injury may require surgical intervention. In fourth-degree injury, only the epineurium remain intact, requiring surgical repair.
Sunderland's fifth-degree is included within Seddon's neurotmesis. Fifth-degree lesion is a complete transection of the nerve, including the epineurium. Recovery requires appropriate surgical treatment.