Classification of peripheral nerve injury

Peripheral nerve injury

Peripheral nerve damage is categorized in the Seddon classification based on the extent of damage to both the nerve and the surrounding connective tissue since the nervous system is characterized by dependence of neurons on their supporting glia. Unlike in the central nervous system, regeneration...

 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:

• Neuropraxia (Class 1)
• Axonotmesis (Class 2)
• Neurotmesis (class 3)

Neurapraxia

Neurapraxia

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...

 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:

• Neurapraxia is the mildest type of peripheral nerve injury.
• There are sensory-motor problems distal to the site of injury.
• The endoneurium
  Endoneurium
  The endoneurium, also referred to as an endoneurial channel, sheath or tube, is a layer of delicate connective tissue made up of endoneurial cells that encloses the myelin sheath of a spinal cord nerve fiber. These are bundled up into groups called nerve fascicles, which have a protective sheath...
  
  , perineurium
  Perineurium
  In the peripheral nervous system, nerve fibers are each wrapped in a protective sheath known as the endoneurium. These are bundled together into groups known as fascicles, each surrounded by a protective sheath known as the perineurium. Several fascicles may be in turn bundled together with a blood...
  
  , and the epineurium
  Epineurium
  The epineurium is the outermost layer of connective tissue surrounding a peripheral nerve. It is made of dense irregular connective tissue and usually contains multiple nerve fascicles as well as blood vessels which supply the nerve...
  
   are intact.
• There is no wallerian degeneration.
• In neurapraxia, 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

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
  Wallerian degeneration is a process that results when a nerve fiber is cut or crushed, in which the part of the axon separated from the neuron's cell body degenerates distal to the injury. This is also known as anterograde degeneration, or orthograde degeneration...
  
   occurs below to the site of injury.
• There are sensory and motor deficits distal to the site of lesion.
• There is not nerve conduction distal to the site 0f 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 because of scar tissue
  Scar tissue
  Scar tissue can refer to:*Granulation tissue, a product of healing in major wounds*The tissue of a scar*"Scar Tissue", a Red Hot Chili Peppers song*Scar Tissue , the autobiography of Anthony Kiedis, lead singer of the Red Hot Chili Peppers...
  
   formation is required.

Neurotmesis

Neurotmesis

Neurotmesis

Neurotmesis 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, both the nerve and the nerve sheath are disrupted....

 is a total severance or disruption of the entire nerve fiber .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 below 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 not nerve conduction distal to the site 0f injury (3 to 4 days after lesion).
• EMG and NCV findings are as axonotmesis.
• Because of lack of nerve repair, surgical intervention is necessary.

Sunderland's classification

In 1951, Sunderland expanded Seddon's classification to five degrees of peripheral nerve injury:

First-degree (Class 1):
Seddon's neuropraxia and first-degree are the same.

Second-degree (Class 2):
Seddon's axonotmesis and second-degree are the same.

Third-degree (Class 3):
Sunderland's third-degree is a nerve fiber

Nerve fiber

A nerve fiber is a threadlike extension of a nerve cell and consists of an axon and myelin sheath in the nervous system. There are nerve fibers in the central nervous system and peripheral nervous system. A nerve fiber may be myelinated and/or unmyelinated. In the central nervous system , myelin...

 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 3):
In fourth-degree injury, only the epineurium remain intact. In this case, surgical repair is required.

Fifth-degree (Class 3):
Fifth-degree lesion is a complete transection of the peripheral nerve. Recovery is not possible without an appropriate surgical treatment.

See also

• Peripheral nerve
• Nerve fiber
  Nerve fiber
  A nerve fiber is a threadlike extension of a nerve cell and consists of an axon and myelin sheath in the nervous system. There are nerve fibers in the central nervous system and peripheral nervous system. A nerve fiber may be myelinated and/or unmyelinated. In the central nervous system , myelin...
  
  
• Peripheral nerve injury
  Peripheral nerve injury
  Peripheral nerve damage is categorized in the Seddon classification based on the extent of damage to both the nerve and the surrounding connective tissue since the nervous system is characterized by dependence of neurons on their supporting glia. Unlike in the central nervous system, regeneration...
  
  (Nerve injury
  Nerve injury
  Nerve injury is injury to nervous tissue. There is no single classification system that can describe all the many variations of nerve injury. Most systems attempt to correlate the degree of injury with symptoms, pathology and prognosis...
  
  )
• Connective tissue in the peripheral nervous system
  Connective tissue in the peripheral nervous system
  A peripheral nerve contains two types of tissue: nerve fibers, and connective tissue. Dendrites and axons with schwann cells and myelin sheath are surrounded by connective tissue. A nerve fiber in the peripheral nervous system consists of an axon or long dendrite, myelin sheath and their schwann...
  
  
• Neuroregeneration
• Wallerian degeneration
  Wallerian degeneration
  Wallerian degeneration is a process that results when a nerve fiber is cut or crushed, in which the part of the axon separated from the neuron's cell body degenerates distal to the injury. This is also known as anterograde degeneration, or orthograde degeneration...