Classification of

peripheral nerve injury Nerve injury is an injury to nervous tissue. There is no single classification system that can describe all the many variations of nerve injuries. In 1941, Seddon introduced a classification of nerve injuries based on three main types of nerve f ...

assists in prognosis and determination of treatment strategy. Classification of nerve injury was described by Seddon in 1943 and by Sunderland in 1951. The lowest degree of nerve injury in which the nerve remains intact but signaling ability is damaged is called neurapraxia. The second degree in which the axon is damaged but the surrounding connecting tissue remains intact is called axonotmesis. The last degree in which both the axon and connective tissue are damaged is called neurotmesis.

Seddon's classification

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

Neurapraxia (Class I)

It is a temporary interruption of conduction without loss of axonal continuity. In neurapraxia, there is a physiologic block of nerve conduction in the affected axons. Other characteristics: *It is the mildest type of peripheral nerve injury. *There are sensory-motor problems distal to the site of injury. *The

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 p ...

are intact. *There is no

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 (i.e. farther from the neuron's cell body) degenerates. A related process of dying back o ...

. *Conduction is intact in the distal segment and proximal segment, but no conduction occurs across the area of injury. * Recovery of nerve conduction deficit is full, and requires days to weeks. *EMG shows lack of fibrillation potentials (FP) and positive sharp waves.

Axonotmesis (Class II)

It involves loss of the relative continuity of the axon and its covering of myelin, but preservation of the connective tissue framework of the nerve (the encapsulating tissue, the epineurium and perineurium, are preserved). Other characteristics: *

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 (i.e. farther from the neuron's cell body) degenerates. A related process of dying back o ...

occurs distal to the site of injury. *There are sensory and motor deficits distal to the site of lesion. *There is no nerve conduction distal to the site of injury (3 to 4 days after injury). *EMG shows fibrillation potentials (FP), and positive sharp waves (2 to 3 weeks postinjury). *Axonal regeneration occurs and recovery is possible without surgical treatment. Sometimes surgical intervention is required, due to

scar tissue Scar tissue may refer to: Medicine * Scar, an area of fibrous tissue that replaces normal skin after injury * Granulation tissue, a product of healing in major wounds Film and television * ''Scar Tissue'' (1975 film), or ''Wanted: Babysitter'' ...

formation.

Neurotmesis (Class III)

It is a total severance or disruption of the entire nerve fiber.Otto D.Payton & Richard P.Di Fabio et al. Manual of physical therapy. Churchill Livingstone Inc. Page: 24. A peripheral nerve fiber contains an axon (Or long dendrite), myelin sheath (if existence), their schwann cells, and the endoneurium. Neurotmesis may be partial or complete. Other characteristics: *Wallerian degeneration occurs distal to the site of injury. *There is connective tissue lesion that may be partial or complete. *Sensory-motor problems and autonomic function defect are severe. *There is no nerve conduction distal to the site of injury (3 to 4 days after lesion). *EMG and NCV findings are as axonotmesis. *Because of lack of nerve, surgical intervention is necessary.

Sunderland's classification

In 1951, Sunderland expanded Seddon's classification to five degrees of peripheral nerve injury: ;First-degree (Class I): Seddon's neurapraxia and first-degree are the same. ;Second-degree (Class II): Seddon's axonotmesis and second-degree are the same. ;Third-degree (Class III): Third-degree is included within Seddon's Neurotmesis. Sunderland's third-degree is a nerve fiber interruption. In third-degree injury, there is a lesion of the endoneurium, but the epineurium and perineurium remain intact. Recovery from a third-degree injury is possible, but surgical intervention may be required. ;Fourth-degree (Class III): Fourth-degree is included within Seddon's Neurotmesis. In fourth-degree injury, only the epineurium remain intact. In this case, surgical repair is required. ;Fifth-degree (Class III): Fifth-degree is included within Seddon's Neurotmesis. Fifth-degree lesion is a complete transection of the nerve. Recovery is not possible without an appropriate surgical treatment.

References