For neurotmesis, it is better to use a new more complete classification called the Sunderland System.

The last degree in which both the axon and connective tissue are damaged is called neurotmesis.

In order of degree of severity, injury to a nerve can be described as neuropraxia, axonotmesis, or neurotmesis.

Seddon classified facial nerve injuries into three broad categories: neuropraxia, neurotmesis, and axonotmesis.

In Seddon's Classification, nerve injury is described as either neurapraxia, axonotmesis, or neurotmesis.

More severe nerve injury like axonotmesis or neurotmesis warrant the repair of the epineurium because the connective tissue is damaged.

Neurotmesis: The most severe form of nerve injury, in which the nerve is completely disrupted by contusion, traction or laceration.

Depending on the type of injury (i.e. Seddon classification: neuropraxia, axonotmesis, and neurotmesis) they can be prolonged or permanent.

With Seddon's classification of nerve injuries it is often tough to identify whether a particular nerve injury is neurotmesis, or axonotmesis, which has damage to the nerve fibres but preservation of the nerve trunk.

In electrodiagnostic testing with nerve conduction studies, there is a normal compound motor action potential amplitude distal to the lesion at day 10, and this indicates a diagnosis of mild neuropraxia instead of axonotmesis or neurotmesis.

The most extreme degree of neurotmesis is transsection, although most neurotmetic injuries do not produce gross loss of continuity of the nerve but rather, internal disruption of the nerve architecture sufficient to involve perineurium and endoneurium as well as axons and their covering.

In order for the condition to be considered neurapraxia, according to the Seddon classification system of peripheral nerve injury, there must be a complete and relatively rapid recovery of motor and sensory function once nerve conduction has been restored; otherwise, the injury would be classified as axonotmesis or neurotmesis.