Neurapraxia
Encyclopedia
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 derived from the word apraxia
, meaning “loss or impairment of the ability to execute complex coordinated movements without muscular or sensory impairment”. This condition is typically caused by a blunt neural injury due to external blows or shock-like injuries to muscle fibers and skeletal nerve fibers
, which leads to repeated or prolonged pressure buildup on the nerve. As a result of this pressure, ischemia
occurs, a neural lesion
results, and the human body naturally responds with edema
extending in all directions from the source of the pressure. This lesion causes a complete or partial action potential
conduction block over a segment of a nerve fiber and thus a reduction or loss of function in parts of the neural connection downstream from the lesion, leading to muscle weakness. Neurapraxia results in temporary damage to the myelin sheath
but leaves the nerve intact and is an impermanent condition; thus, Wallerian degeneration
does not occur in neurapraxia. 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
. Thus, neurapraxia is the mildest classification of peripheral nerve injury. Neurapraxia is very common in professional athletes, specifically American football
players, and is a condition that can and should be treated by a physician.
. Therefore, distal nerve fibers do not degenerate and the myelin damage can be repaired.
within the first 24 hours after injury follows a general pattern of nerve injury. The first physical manifestation of the injury is focal swelling adjacent to the site of the injury. In the cellular dimension, a fragmentation of neurotubules and neurofilament
s occurs as a result of pressure exerted on the nerve. Axons swell at some sites and are compressed at others, leading to a beaded appearance.
and sudomotor
paralysis
in the region of the affected nerve or nerves, and abnormal sensitivity of the nerve at the point of injury. It has been observed that subjective sensory symptoms include numbness, tingling, and burning sensations at the site of the injury. Objective sensory symptoms are generally minimal in regards to touch, pain, heat, and cold. In cases of motor neuron neurapraxia, symptoms consist of flaccid paralysis
of the muscles innervated by the injured nerve or nerves.
Symptoms are most often transient and only last for a short period of time immediately following the injury. However, in rare but severe cases of neurapraxia, symptoms can persist for weeks or months at a time.
There are two different forms of mechanical nerve injury involving neurapraxia. The underlying causes of transient nerve injury typically include a brief ischemic episode or any form of compression. More persistent forms of nerve injury involve demyelination and axonal constriction. In certain circumstances, diagnosing neurapraxia can be uncomfortable because of the presence of severe neuropathic pain
. Neuropathic pain is an indication that the lesion of the nerve is still in progress. Diagnosis of neurapraxia is almost always followed by a quick and complete recovery period.
is often used in cases of neurapraxia because it is able to maintain a relaxed position of the paralyzed muscle. The splint prevents the paralyzed muscle from being overstretched either by the force of gravity or by other non-paralyzed antagonists. During the recovery period of neurapraxia, it is essential that the joints constantly undergo passive movement in order to preserve proper mobility. If joints are kept mobile, the limb has the best possible chance of benefit from the return of nervous function. Non-steroidal anti-inflammatory medications can also help to reduce swelling at the injury site. In addition to these non-operative remedies, it is suggested that muscles affected by neurapraxia be kept warm at all times. Circulation in the limb is stimulated with the use of heat.
Once voluntary movement has returned to the muscle, recovery and treatment continues by the participation in active exercises. Physical therapy
is a common source of treatment during these early stages of restoration of active movement. Almost all cases of neurapraxia can be completely treated by non-operative means.
. Athletes participating in collision sports most often suffer from cervical cord neurapraxia, also known as transient neurapraxia. Cervical cord neurapraxia is the result of a severe collision in which a blow to the crown of the athlete’s head forcefully extends or compresses the neck. Numbness, stinging, and/or weakness in the arms, legs or both, distinguish cervical cord neurapraxia. Typical episodes of transient nuerapraxia only last a few seconds and symptoms dissipate entirely. Though the severity of the injury can range, transient neurapraxia does not lead to permanent paralysis of the affected muscles. Subsequent spinal cord injury after an episode of cervical cord neurapraxia has not been observed. However, athletes who experience an episode of transient cervical neurapraxia face an approximately 50% chance of a repeat episode if they continue to participate in collision sports.
, once an athlete suffers from an episode of cervical spinal cord
neurapraxia, team physician or athletic trainer first stabilize the head and neck followed by a thorough neurologic inspection. If the injury is deemed severe, injured parties should be taken to a hospital for evaluation. Athletes that suffer from severe episodes of neurapraxia are urged to consult orthopaedic or spinal medical specialists. In mild cases of neurapraxia, the athlete is able to remove themselves from the field of play. However, the athlete is still advised to seek medical consultation.
were first described in 1986 by Joseph S. Torg, M.D., founder of the National Football Head and Neck Injury Registry (established in 1975). As a result of Dr. Torg’s findings the NFL as well as other levels of American football have outlawed the act of spearing, or the lowering of the head and hitting an opponent with the crown of the helmet. The cervical spine cannot properly absorb the force of a collision when the head is even slightly lowered as is the case in spearing. In addition to outlawing acts such as spearing, prevention of neurapraxia on the football field relies on instruction and reinforcement of proper tackling technique by coaches and trainers.
was forced to retire from professional wrestling on April 11, 2011 due to symptoms of neurapraxia. If he wrestles again, he risks worsening his condition possibly to the extent of paralysis.
In 2003, Adam Copeland underwent a two level spinal fusion of the discs between his C5, C6 and C7 vertebrae. After being cleared to compete, he returned to the ring, resulting in stenosis of the spine, or a narrowing of the spinal column, above and below the fused discs. This narrowing resulted in less and less of the vital fluid needed to protect the spinal cord.
Peripheral nervous system
The peripheral nervous system consists of the nerves and ganglia outside of the brain and spinal cord. The main function of the PNS is to connect the central nervous system to the limbs and organs. Unlike the CNS, the PNS is not protected by the bone of spine and skull, or by the blood–brain...
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 derived from the word apraxia
Apraxia
Apraxia is a disorder caused by damage to specific areas of the cerebrum. Apraxia is characterized by loss of the ability to execute or carry out learned purposeful movements, despite having the desire and the physical ability to perform the movements...
, meaning “loss or impairment of the ability to execute complex coordinated movements without muscular or sensory impairment”. This condition is typically caused by a blunt neural injury due to external blows or shock-like injuries to muscle fibers and skeletal nerve fibers
Motor neuron
In vertebrates, the term motor neuron classically applies to neurons located in the central nervous system that project their axons outside the CNS and directly or indirectly control muscles...
, which leads to repeated or prolonged pressure buildup on the nerve. As a result of this pressure, ischemia
Ischemia
In medicine, ischemia is a restriction in blood supply, generally due to factors in the blood vessels, with resultant damage or dysfunction of tissue. It may also be spelled ischaemia or ischæmia...
occurs, a neural lesion
Lesion
A lesion is any abnormality in the tissue of an organism , usually caused by disease or trauma. Lesion is derived from the Latin word laesio which means injury.- Types :...
results, and the human body naturally responds with edema
Edema
Edema or oedema ; both words from the Greek , oídēma "swelling"), formerly known as dropsy or hydropsy, is an abnormal accumulation of fluid beneath the skin or in one or more cavities of the body that produces swelling...
extending in all directions from the source of the pressure. This lesion causes a complete or partial action potential
Action potential
In physiology, an action potential is a short-lasting event in which the electrical membrane potential of a cell rapidly rises and falls, following a consistent trajectory. Action potentials occur in several types of animal cells, called excitable cells, which include neurons, muscle cells, and...
conduction block over a segment of a nerve fiber and thus a reduction or loss of function in parts of the neural connection downstream from the lesion, leading to muscle weakness. Neurapraxia results in temporary damage to the myelin sheath
Myelin
Myelin is a dielectric material that forms a layer, the myelin sheath, usually around only the axon of a neuron. It is essential for the proper functioning of the nervous system. Myelin is an outgrowth of a type of glial cell. The production of the myelin sheath is called myelination...
but leaves the nerve intact and is an impermanent condition; thus, 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...
does not occur in neurapraxia. In order for the condition to be considered neurapraxia, according to the Seddon classification
Peripheral nerve injury classification
Classification of peripheral nerve injury 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...
system of peripheral nerve injury, there must be a complete and relatively rapid recovery of motor and sensory function once nerve conduction
Action potential
In physiology, an action potential is a short-lasting event in which the electrical membrane potential of a cell rapidly rises and falls, following a consistent trajectory. Action potentials occur in several types of animal cells, called excitable cells, which include neurons, muscle cells, and...
has been restored; otherwise, the injury would be classified as axonotmesis
Axonotmesis
Axonotmesis is a disruption of nerve cell axon, with Wallerian degeneration occurring below and slightly proximal to the site of injury. If axons, and their myelin sheath are damaged, but schwann cells, the endoneurium, perineurium and epineurium remain intact is called axonotmesis. Axonotmesis is...
or 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....
. Thus, neurapraxia is the mildest classification of peripheral nerve injury. Neurapraxia is very common in professional athletes, specifically American football
American football
American football is a sport played between two teams of eleven with the objective of scoring points by advancing the ball into the opposing team's end zone. Known in the United States simply as football, it may also be referred to informally as gridiron football. The ball can be advanced by...
players, and is a condition that can and should be treated by a physician.
Anatomy
Neurapraxia occurs in the peripheral nervous system typically in the ulnar, median, radial and brachial plexus nerves of the upper body and in the sciatic and peroneal nerves of the lower body. Peripheral nerves are myelinated, relatively large, spatially complex cells whose size and connectivity typically make them more susceptible to damage and compromise their capacity to self-repair, although this is not the case in neurapraxia. Microscopic evidence has shown that there is damage to the myelin sheath, but not to the axonAxon
An axon is a long, slender projection of a nerve cell, or neuron, that conducts electrical impulses away from the neuron's cell body or soma....
. Therefore, distal nerve fibers do not degenerate and the myelin damage can be repaired.
Order of pathology
The order of pathologyPathology
Pathology is the precise study and diagnosis of disease. The word pathology is from Ancient Greek , pathos, "feeling, suffering"; and , -logia, "the study of". Pathologization, to pathologize, refers to the process of defining a condition or behavior as pathological, e.g. pathological gambling....
within the first 24 hours after injury follows a general pattern of nerve injury. The first physical manifestation of the injury is focal swelling adjacent to the site of the injury. In the cellular dimension, a fragmentation of neurotubules and neurofilament
Neurofilament
Neurofilaments are the 10 nanometer intermediate filaments found specifically in neurons. They are a major component of the cell's cytoskeleton, and provide support for normal axonal radial growth...
s occurs as a result of pressure exerted on the nerve. Axons swell at some sites and are compressed at others, leading to a beaded appearance.
Symptoms
A variety of nerve types can be subjected to neurapraxia and therefore symptoms of the injury range in degree and intensity. Common symptoms of neurapraxia are disturbances in sensation, weakness of muscle, vasomotorVasomotor
Vasomotor refers to actions upon a blood vessel which alter its diameter. More specifically, it can refer to vasodilator action and vasoconstrictor action....
and sudomotor
Sudomotor
Sudomotor is a medical term used to describe something that stimulates the sweat glands.Sudomotor Innervation may refer to the cholinergic innervation of the sympathetic nervous system prominent in sweat glands which causes perspiration to occur via activation of muscarinic acetylcholine receptors....
paralysis
Paralysis
Paralysis is loss of muscle function for one or more muscles. Paralysis can be accompanied by a loss of feeling in the affected area if there is sensory damage as well as motor. A study conducted by the Christopher & Dana Reeve Foundation, suggests that about 1 in 50 people have been diagnosed...
in the region of the affected nerve or nerves, and abnormal sensitivity of the nerve at the point of injury. It has been observed that subjective sensory symptoms include numbness, tingling, and burning sensations at the site of the injury. Objective sensory symptoms are generally minimal in regards to touch, pain, heat, and cold. In cases of motor neuron neurapraxia, symptoms consist of flaccid paralysis
Flaccid paralysis
Flaccid paralysis is a clinical manifestation characterized by weakness or paralysis and reduced muscle tone without other obvious cause .-Polio:...
of the muscles innervated by the injured nerve or nerves.
Symptoms are most often transient and only last for a short period of time immediately following the injury. However, in rare but severe cases of neurapraxia, symptoms can persist for weeks or months at a time.
Causes
The cause of neurapraxia is a neural lesion which causes a temporary block of nerve conduction without transection of the axon. A conduction block is classified as a 40% reduction in action potential amplitude over a short distance on the nerve, or a 50% reduction for a longer distance on the nerve. In neurapraxia, stimulation to the injured nerve results in a greater reduction in the action potential amplitude on the proximal site of the injury as opposed to the distal site.Mechanisms of injury
There are several mechanisms of nerve injury including mechanical lesions, ischemia, immunologic attack, metabolic disorder, toxic agents, and exposure to radiation. The most common mechanism of injury is nerve compression in which external pressure causes decreased blood flow to the nerve and deformation of the nerve fibers. Repeated or prolonged compression of the nerve results in ischemia and ultimately edema above and below the source of the pressure (I). The thinning of myelin sheaths or focal demyelination are the main consequences of the injury that lead to conduction blockage.Seddon’s classifications of peripheral nerve damage
There are three distinct classifications and degrees of nerve injury:- NeurotmesisNeurotmesisNeurotmesis 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 the most serious degree of nerve injury. It involves the disruption of the nerve and the nerve sheath. - AxonotmesisAxonotmesisAxonotmesis is a disruption of nerve cell axon, with Wallerian degeneration occurring below and slightly proximal to the site of injury. If axons, and their myelin sheath are damaged, but schwann cells, the endoneurium, perineurium and epineurium remain intact is called axonotmesis. Axonotmesis is...
occurs when the majority of the supporting structures of the nerve are preserved, but disruption of the nerve fibers is still observed. Wallerian degeneration often occurs in the near the proximity of the injury site. - Neurapraxia is least serious form of nerve injury.
There are two different forms of mechanical nerve injury involving neurapraxia. The underlying causes of transient nerve injury typically include a brief ischemic episode or any form of compression. More persistent forms of nerve injury involve demyelination and axonal constriction. In certain circumstances, diagnosing neurapraxia can be uncomfortable because of the presence of severe neuropathic pain
Neuropathic pain
Neuropathic pain results from lesions or diseases affecting the somatosensory system. It may be associated with abnormal sensations called dysesthesia, which occur spontaneously and allodynia that occurs in response to external stimuli. Neuropathic pain may have continuous and/or episodic ...
. Neuropathic pain is an indication that the lesion of the nerve is still in progress. Diagnosis of neurapraxia is almost always followed by a quick and complete recovery period.
Prognosis
In cases of neurapraxia, the function of the nerves are temporarily impaired or, in rare cases, completely lost. However, the prognosis for recovery from neurapraxia is efficient and quick. Recovery begins within two to three weeks after the injury occurs, and it is complete within six to eight weeks. There are instances when function is not completely restored until four months after the instance of injury. The recovery period of neurapraxia is not an entirely ordered process, but the recovery is always complete and fast.Treatment and recovery
The entire nerve is involved in the response to traumatic injuries. The outcome of nerve repair is dependent on the degree of the nerve injury and the circumstances at the site of injury. Since neurapraxia is the least serious form of peripheral nerve injury, recovery and treatment are not extensive. Once the cause of neurapraxia is eliminated, recovery of the lesions in the nerve occurs within a short time span.Non-operative treatment
Neurapraxia is often treated and cured by non-operative means. The primary goals of treatment are to maintain the proper nutrition of the paralyzed muscles, prevent contraction by the antagonists of the paralyzed muscles, and to consistently keep the joints mobile. A splintSplint (medicine)
A splint is a device used for support or immobilization of limbs or of the spine.It can be used:* By the emergency medical services or by volunteer first responders, to immobilize a fractured limb before the transportation; it is then a temporary immobilization;* By allied health professionals such...
is often used in cases of neurapraxia because it is able to maintain a relaxed position of the paralyzed muscle. The splint prevents the paralyzed muscle from being overstretched either by the force of gravity or by other non-paralyzed antagonists. During the recovery period of neurapraxia, it is essential that the joints constantly undergo passive movement in order to preserve proper mobility. If joints are kept mobile, the limb has the best possible chance of benefit from the return of nervous function. Non-steroidal anti-inflammatory medications can also help to reduce swelling at the injury site. In addition to these non-operative remedies, it is suggested that muscles affected by neurapraxia be kept warm at all times. Circulation in the limb is stimulated with the use of heat.
Once voluntary movement has returned to the muscle, recovery and treatment continues by the participation in active exercises. Physical therapy
Physical therapy
Physical therapy , often abbreviated PT, is a health care profession. Physical therapy is concerned with identifying and maximizing quality of life and movement potential within the spheres of promotion, prevention, diagnosis, treatment/intervention,and rehabilitation...
is a common source of treatment during these early stages of restoration of active movement. Almost all cases of neurapraxia can be completely treated by non-operative means.
Prevalence in collision sports
Neurapraxia is most commonly observed in athletes involved in collision sports, such as American footballAmerican football
American football is a sport played between two teams of eleven with the objective of scoring points by advancing the ball into the opposing team's end zone. Known in the United States simply as football, it may also be referred to informally as gridiron football. The ball can be advanced by...
. Athletes participating in collision sports most often suffer from cervical cord neurapraxia, also known as transient neurapraxia. Cervical cord neurapraxia is the result of a severe collision in which a blow to the crown of the athlete’s head forcefully extends or compresses the neck. Numbness, stinging, and/or weakness in the arms, legs or both, distinguish cervical cord neurapraxia. Typical episodes of transient nuerapraxia only last a few seconds and symptoms dissipate entirely. Though the severity of the injury can range, transient neurapraxia does not lead to permanent paralysis of the affected muscles. Subsequent spinal cord injury after an episode of cervical cord neurapraxia has not been observed. However, athletes who experience an episode of transient cervical neurapraxia face an approximately 50% chance of a repeat episode if they continue to participate in collision sports.
Treating cervical cord neurapraxia on the field
According to medical professionals with the Cleveland ClinicCleveland Clinic
The Cleveland Clinic is a multispecialty academic medical center located in Cleveland, Ohio, United States. The Cleveland Clinic is currently regarded as one of the top 4 hospitals in the United States as rated by U.S. News & World Report...
, once an athlete suffers from an episode of cervical spinal cord
Spinal cord
The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...
neurapraxia, team physician or athletic trainer first stabilize the head and neck followed by a thorough neurologic inspection. If the injury is deemed severe, injured parties should be taken to a hospital for evaluation. Athletes that suffer from severe episodes of neurapraxia are urged to consult orthopaedic or spinal medical specialists. In mild cases of neurapraxia, the athlete is able to remove themselves from the field of play. However, the athlete is still advised to seek medical consultation.
Impact on American football
Cervical cord neurapraxia among American football players is commonly observed in athletes playing positions involving high-speed collisions and open-field tackling. Cases of neuropraxia in the National Football LeagueNational Football League
The National Football League is the highest level of professional American football in the United States, and is considered the top professional American football league in the world. It was formed by eleven teams in 1920 as the American Professional Football Association, with the league changing...
were first described in 1986 by Joseph S. Torg, M.D., founder of the National Football Head and Neck Injury Registry (established in 1975). As a result of Dr. Torg’s findings the NFL as well as other levels of American football have outlawed the act of spearing, or the lowering of the head and hitting an opponent with the crown of the helmet. The cervical spine cannot properly absorb the force of a collision when the head is even slightly lowered as is the case in spearing. In addition to outlawing acts such as spearing, prevention of neurapraxia on the football field relies on instruction and reinforcement of proper tackling technique by coaches and trainers.
Current cases in professional wrestling
WWE Superstar Adam CopelandAdam Copeland
Adam Joseph Copeland is a retired Canadian professional wrestler and actor, better known by his ring name Edge. He is currently signed to WWE under a Legends contract....
was forced to retire from professional wrestling on April 11, 2011 due to symptoms of neurapraxia. If he wrestles again, he risks worsening his condition possibly to the extent of paralysis.
In 2003, Adam Copeland underwent a two level spinal fusion of the discs between his C5, C6 and C7 vertebrae. After being cleared to compete, he returned to the ring, resulting in stenosis of the spine, or a narrowing of the spinal column, above and below the fused discs. This narrowing resulted in less and less of the vital fluid needed to protect the spinal cord.
See also
- AxonotmesisAxonotmesisAxonotmesis is a disruption of nerve cell axon, with Wallerian degeneration occurring below and slightly proximal to the site of injury. If axons, and their myelin sheath are damaged, but schwann cells, the endoneurium, perineurium and epineurium remain intact is called axonotmesis. Axonotmesis is...
- NeurotmesisNeurotmesisNeurotmesis 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....
- Nerve injuryNerve injuryNerve 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...
- Peripheral nerve injuryPeripheral nerve injuryPeripheral 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...
- Neuroregeneration
- Wallerian degenerationWallerian degenerationWallerian 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...
- Seddon's classification