Nerve injury classification assists in

prognosis Prognosis ( Greek: πρόγνωσις "fore-knowing, foreseeing"; : prognoses) is a medical term for predicting the likelihood or expected development of a disease, including whether the signs and symptoms will improve or worsen (and how quickly) ...

and determination of treatment strategy for nerve injuries. Classification was described by Seddon in 1943 and by Sunderland in 1951. In the lowest degree of nerve injury the nerve remains intact, but signaling ability is damaged, termed

neurapraxia Neurapraxia is a disorder of the peripheral nervous system in which there is a temporary loss of motor and sensory function due to blockage of nerve conduction, usually lasting an average of six to eight weeks before full recovery. Neurapraxia is ...

. In the second degree the

axon An axon (from Greek ἄξων ''áxōn'', axis) or nerve fiber (or nerve fibre: see American and British English spelling differences#-re, -er, spelling differences) is a long, slender cellular extensions, projection of a nerve cell, or neuron, ...

is damaged, but the surrounding

connecting tissue ''Connecting...'' is an American television sitcom co-created and co-executive produced by Martin Gero and Brendan Gall for Universal Television. The series aired from October 8 to October 29, 2020 on NBC. In November 2020, the series was can ...

remains intact –

axonotmesis Axonotmesis is an injury to the peripheral nerve of one of the extremities of the body. The axons and their myelin sheath are damaged in this kind of injury, but the endoneurium, perineurium and epineurium remain intact. Motor and sensory function ...

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

neurotmesis Neurotmesis (in Greek tmesis signifies "to cut") is a complete transection of a peripheral nerve, and is part of Seddon's classification scheme used to classify nerve damage. It is the most serious nerve injury in the scheme. In this type of injury ...

Seddon's classification

In 1943, Seddon described three basic types of nerve injury:

Neurapraxia (Class I)

Neurapraxia is a temporary interruption of conduction without loss of axonal continuity. Neurapraxia involves a physiologic block of nerve conduction in the affected axons. Other characteristics: *mildest type of nerve injury *sensory-motor problems present

distal Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position provi ...

to the site of injury *intact

endoneurium The endoneurium (also called endoneurial channel, endoneurial sheath, endoneurial tube, or Henle's sheath) is a layer of delicate connective tissue around the myelin sheath of each myelinated nerve fiber in the peripheral nervous system. Its comp ...

perineurium The perineurium is a protective sheath that surrounds a nerve fascicle. This bundles together axons targeting the same anatomical location. The perineurium is composed from fibroblasts. In the peripheral nervous system, the myelin sheath of each ...

, and the

epineurium The epineurium is the outermost layer of dense irregular connective tissue surrounding a peripheral nerve. It usually surrounds multiple nerve fascicles as well as blood vessels which supply the nerve. Smaller branches of these blood vessels penet ...

wallerian degeneration Wallerian degeneration is an active process of degeneration that results when a nerve fiber is cut or crushed and the part of the axon distal to the injury (which in most cases is farther from the neuron's cell body) degenerates. A related process ...

not present *intact conduction in the distal and proximal segments, but no conduction across the injury * full nerve conduction recovery, requiring days to weeks *

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potentials (FP) lacking, and positive sharp EMG waves.

Axonotmesis (Class II)

Axonotmesis involves loss of relative axon continuity and

myelin Myelin Sheath ( ) is a lipid-rich material that in most vertebrates surrounds the axons of neurons to insulate them and increase the rate at which electrical impulses (called action potentials) pass along the axon. The myelinated axon can be lik ...

covering, but preservation of the connective tissue framework (including encapsulating tissue, the

and

). Other characteristics: *distal

Wallerian degeneration Wallerian degeneration is an active process of degeneration that results when a nerve fiber is cut or crushed and the part of the axon distal to the injury (which in most cases is farther from the neuron's cell body) degenerates. A related process ...

*distal sensory and motor deficits *nerve conduction distal to the site of injury (3 to 4 days after injury) absent *fibrillation potentials (FP), and positive, sharp EMG waves (2 to 3 weeks post injury). *axonal regeneration and recovery does not typically require surgical treatment, although surgical intervention may be required, due to

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Neurotmesis (Class III)

Neurotmesis is total severance/disruption of the nerve fiber.Otto D.Payton & Richard P.Di Fabio et al. Manual of physical therapy. Churchill Livingstone Inc. Page: 24. Axon, endo-, peri-, and epineurium transected. Neurotmesis may be partial or complete. Other characteristics: *distal Wallerian degeneration *partial or complete connective tissue lesion *severe sensory-motor problems and autonomic function defect *nerve conduction distal to the site of injury absent (3 to 4 days after lesion) *no distal conduction (EMG and NCV (nerve conduction velocity) *surgical intervention is necessary to restore function

Sunderland's classification

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 An axon (from Greek ἄξων ''áxōn'', axis) or nerve fiber (or nerve fibre: see spelling differences) is a long, slender projection of a nerve cell, or neuron, in vertebrates, that typically conducts electrical impulses known as action pot ...

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.

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