nerve damage

Synonyms

Nerve damage, nerve lesion, nerve injury

Nerve damage, nerve injury

definition

Nerve damage is an injury to nerve tissue that shows objectively detectable nerve damage. The problem with nerve lesions is that this tissue has limited ability to regenerate, so permanent damage can be left behind.

Classification of nerve damage

Nerve damage is classified according to the location of the injury, so one differentiates one

  • central nerve damage in the area of ​​the central nervous system and
  • peripheral nerve damage located outside the skull and spinal canal.

In addition, a nerve damage can be differentiated according to the type of injury:

  • Neurapraxia : Here, the axon and its envelope structures are preserved.
  • Axonotmesis : The axon is interrupted, its envelope structures are completely preserved.
  • Neurotmesis : Both the axon is broken and the enveloping structures are completely or partially injured. An axon is a tubular nerve cell process located in a sheath of glial cells. The combination axon and sheath structure is called nerve fiber.

Classification of nerve damage

Another classification is the one of

  • acute and
  • chronic nerve damage

The acute nerve damage is often direct trauma, that is to say direct effects on the nerves. This can be injured mechanically, eg by a scalpel during an operation, or by an injection or a knife cut. These are "sharp" injuries.
It is called "blunt" injuries when it comes to a nerve compression. For example, a bruise or abscess presses on the nerve.

In chronic nerve compression, there is a mechanical effect from the outside, such as the carpal tunnel syndrome. They prevent a good blood circulation of the nerve tissue and damage the myelin sheath (envelope of the nerve).

Half of all people who have to work with vibrating objects such as a jackhammer for years experience so-called vibration damage. These include tingling sensations on the arms and faster fatigue of the hands.
In the nerves this can lead to a multifocal demyelination . That is, the myelin sheath surrounding the nerves decreases, and at the same time, the nerve conduction velocity slows down. Multifocal means that this occurs in several places of the nerves.

An injection into an arterial vessel can lead to a vasospasm (contraction of the vessels). This closure prevents blood flow to the nerves, causing acute so-called ischemic damage .

Due to a chronic ischemic nerve damage, it can occur to the clinical picture of vasculitis. Here, inflammation damages the nerves supplying vessels. Metabolic disorders such as diabetes mellitus can also lead to a chronic ischemic nerve lesion.

Toxic effects can be acute by injection of toxic solutions in or next to the nerve. Chronic Noxa Alcohol can lead to polyneuropathy during prolonged alcohol abuse.

Immunologically, a nerve damage, for example, by antibody formation, which damage the nerve or its envelope structures. Often there is severe pain on one limb.

Pathogens can cause nerve damage either directly or indirectly through their toxins. Above all, the nerve root is susceptible to pathogens, because it is not everywhere in the body with a protective layer.
For example, herpesviruses may remain in the spinal ganglion and cause nerve inflammation. Myctobacterium leprae, HI virus and Borrelia can also damage the nerve.

Radiation can cause an acute or chronic injury to the nerves. Most of the symptoms occur with some delay. Genetic, ie hereditary, nerve lesions can occur, for example, in multiple sclerosis or in amyotrophic lateral sclerosis. The genetic picture is often neurodegenerative (ie, the nerve tissue is gradually absorbed) and becomes worse with age.

Thermal damage to the nerves mainly affects the non-marrow (sheath-free) nerve fibers and the small nerve-supplying blood vessels.
In addition to the above-mentioned causes of nerve damage, there are still other unexplained reasons that damage the nerve tissue and cause an objectifiable failure.

symptoms

Typical signs of a nerve injury are on the one hand the disturbed sensibility in the supply area of ​​the nerve and on the other hand the failure of the motor power in the muscle, which is supplied only by this one injured nerve. Furthermore, a disturbed pain sensation as well as an inhibited two-point discrimination occur. Two-point discrimination means that two juxtaposed stimuli are not perceived as two different but as one.

Objects can no longer be distinguished as pointed or obtuse. Another sign is the defect of the depth sensitivity and the sense of position. Likewise, the vegetative nerve tissue may have been injured and altered skin temperatures and disturbed perspiration may occur. Pain in and around a nerve supply area also causes neuralgia pain.

Healing duration of a nerve damage

The healing time of a nerve damage depends primarily on the extent of the damage. Minor damage, which only resulted in damage to the nerve sheath, usually heals within a few days. In case of incomplete transection, it may also take only a few weeks for the complete neurological function of the nerve to be restored. It is more complicated with complete nerve partings. The basic requirement for nerve generation here is that the nerve cell body is unhurt, which is usually the case.

2-3 days after injury, axons begin to regenerate and grow at a staggering rate of 0.5-2 millimeters per day. The regeneration begins here at the severed end of the axon. However, the autonomous regeneration of the nerve does not occur by re-growing the two ends, but by a complete re-education of the nerve behind the lesion. For example, nerve damage to the forearm may take 3-6 months to fully regrow the nerve fibers and resume function. However, intact connective tissue nerve sheaths, as a lead structure, are necessary for such a replenishment.

Find out here on the topic: Numbness

Cause of a nerve damage

There are several causes that can damage such a delicate structure as the nerve tissue and thus lead to permanent damage. These include:

  • mechanical damage or trauma
  • vibration damage
  • Ischemia (circulatory disorder)
  • toxic effects
  • Damage caused by the immune system (autoimmune disease)
  • pathogenic lesions (infection)
  • radiotherapy
  • Genetic injury to the nerve (DNA damage)
  • Electric trauma and
  • Nerve injuries of unknown cause
  • Piercing the tongue (tongue piercing)

After an operation

Depending on the operating area, there is a low risk of nerve damage during surgery. This mainly affects major orthopedic operations of the extremities, but also in the upper neck area. But even minor operations, such as a carpal tunnel syndrome, can lead to nerve damage. It is believed that circa. 15% of all known nerve damage occurs during surgery.

If it is recognized that a nerve has been damaged during the operation, the further course of action initially depends largely on the extent of the damage. Thus, minor damage to the outer shell of a nerve requires no further treatment. However, if there is a complete transection of a nerve, this is usually supplied directly surgically or in a subsequent operation.

For all moderate nerve damage, in which no complete transection has taken place, a wait and see approach is recommended to give the nerve the chance of autonomous regeneration. If this is unsuccessful, an operative repair of the nerve damage is usually carried out. Legal claims from the point of view of the patient usually do not arise with nerve damage, since this complication is often part of the explanation.

After chemotherapy

As a result of some chemotherapeutic agents, so-called neuropathy can occur. This disease, which usually occurs on the hands and feet, is usually perceived by those affected as an unpleasant tingling sensation. However, it can also lead to a feeling of numbness or muscle weaknesses. If several areas of the body are affected by this phenomenon, it is called polyneuropathy.

Most of the time, however, this is only temporary and stops already a few weeks after completion of the chemotherapy. Overall, about one third of all patients with chemotherapy are affected by polyneuropathy. In some cases, however, this condition may also be chronic and the nerve damage permanent. This applies above all to the patients, who already showed a very high level of chemotherapy.

After a herniated disc

If a spinal disc prolapse results in prolonged pressure on spinal nerves, the result may be nerve damage. Such damage is in addition to pain, usually associated with a variable loss of neurological functions. How this loss presents depends, in addition to the extent of the damage, above all on the amount of nerve damage. For example, in herniated discs of the neck and chest, the sensibility and musculature of the arms and torso may be affected, whereas in the lower position, the legs may lose function. To what extent the damaged nerve is regenerated depends on the exact damage pattern and the duration of the pressure load. In the area of ​​the spinal nerves, however, one must assume a slow regeneration process.

Find out more about the topics here:

  • Herniated disc in the cervical spine
  • Herniated disc in the thoracic spine

After regional anesthesia

There are several surgical procedures that use regional anesthesia, such as arm and shoulder, by injecting local anesthetics into the armpit.

Nerve damage after regional anesthesia most commonly affects the ulnar nerve or the entire brachial plexus, a network of nerves for the neurological supply to the arm. Damage to the nerves takes place on the one hand by contact of the needle tip with the nerve itself.

However, this risk has now been significantly reduced by performing on awake patients. Serious nerve damage can especially occur if the local anesthetic is injected directly into the nerves. But even this risk is significantly reduced nowadays, since the position of the nerves can be well determined by electrical stimulation. If, despite these measures, nerve damage occurs while performing regional anesthetics, these usually have a good prognosis.

Find out more about the topics here:

  • Side effects of local anesthesia
  • Peripheral nerve block

Carpal Tunnel Syndrome

The clinical picture of the carpal tunnel syndrome is relatively common in the population. Above all, women are affected who have to perform repetitive tasks with their hands while working. In the carpal tunnel syndrome, there is a permanent pressure load on the median nerve in the area of ​​the wrist. The increased pressure is due to a too narrow limitation of the area in the wrist through which vessels, nerves and muscle tendons run. The upper limit, which is relevant for therapy, is called the ligament carpi volare.

Symptoms of the carpal tunnel syndrome are pain and sensory disturbances on the thumb, forefinger and especially of the middle finger. Most of them start at night, during the course of the disease then occur during the day. The sensory disturbance usually leads to a loss of "instinct" and smaller precise activities are much more difficult.

The therapy of the carpal tunnel syndrome consists initially of an immobilization of the wrist and possibly the local application of steroids or local anesthetics. If there is no improvement, an operative splitting of the ligament described above is performed.

therapy

There is the possibility to provide nerve damage conservatively or surgically. However, it depends on the type of injury. Thus, in diabetes mellitus or other metabolic diseases and vascular diseases, conservative measures can lead to healing. Surgical relief should be provided in the event of pressure damage to the nerve.

In the case of chronic nerve compression, such as in carpal tunnel syndrome, the area should be immobilized by splinting. In addition, anti-inflammatory drugs are prescribed and physiotherapy is recommended. If a further deterioration occurs, the carpal tunnel syndrome must be surgically treated. This is followed by another immobilization for about three weeks and additional physiotherapy.

In the case of toxic nerve damage, the noxa should be avoided, ie no alcohol in alcoholically induced polyneuropathy. Depending on the cause of the nerve damage, it is also possible to intervene medically. In diabetes mellitus, the blood sugar should be adjusted well. With vitamin deficiencies, vitamin supplements can remedy the deficiency.

The chances of recovery are in turn related to the type of lesion. So it seems quite logical that a neuropraxia (where the axon and its sheath are preserved) or an axonotmesis (the axon is interrupted, but its envelope structure is preserved) have a better prognosis than a neurotmesis . In case of complete or partial interruption of the nerve, a permanent functional restriction is to be expected.

The longer the nerve lesion lasts and the closer it is to the central nervous system, the worse the prognosis for a complete cure. If the nerve damage is quite long, the danger of a false innervation increases, ie: the nerve no longer grows together with its own nerve, but grows into another supply area.

diagnostics

Thorough clinical examination will help the doctor to find out if it is a nerve lesion and where it is located. It will be the

  • sensitive
  • motor and
  • vegetative functions

of the nervous in the area of ​​its supply checked. It is also possible to test the Hoffmann-Tinel mark. In doing so, one taps on the nerve and waits for paresthesias such as tingling in the innervation area of ​​the nerve. Furthermore, clinical tests such as neurography and electromyography can be performed.

When is the nerve dead?

There are two scenarios that can cause a nerve to be unable to regenerate after injury, so it is "dead". The "dying" of the nerve usually manifests itself in the abrupt disappearance of the previously existing nerve pain or acute paralysis phenomena.

A possible cause of the death of a nerve is the damage to the nerve cell body. In the cell body of a nerve cell the energy is provided and the different building blocks for a successful regeneration of the axon are produced. If this cell body is damaged, these functions can no longer be performed with the result of a lack of regeneration.

The second option is grade 5 nerve damage. This describes a complete nerve transection along with the surrounding connective tissue nerve sheath. Since the latter serves as a guiding structure for the axon regeneration, it can no longer result in a targeted regeneration of the nerve when it is transected. It only forms a nerve cell proliferation, which, however, has no neurological functions.

Nerve damage in the body

In the legs

Nerve damage in the legs can be triggered by many different causes. In addition to nerve damage or transection during surgery, for example, a diabetes mellitus lead to permanent nerve damage to the legs, especially the feet. This causes damage to the nerves due to long-lasting high blood sugar levels and causes sensory disturbances, a tingling sensation or burning or burning pain. However, the feet are one of the most common sites of polyneuropathy due to chemotherapy. This is clinically very similar to neuropathy in diabetes. Another possible cause of damage to nerves that perform neurological functions in the leg are constrictions in the area of ​​spinal nerve exudate. These include, for example herniated discs, but also Foraminalstenosen, in which the outlet channel is narrowed at the spine. Rarer causes include tumors, shingles or neurodegenerative diseases such as amyotrophic lateral sclerosis (AML) or multiple sclerosis (MS), which, however, usually cause symptoms in several parts of the body.

In the foot

Different causes can lead to nerve damage in the foot. First and foremost, a long-standing diabetes mellitus should be mentioned here. This can lead to chronic nerve damage due to long-lasting high blood sugar levels, which usually begins in the feet. The consequences are pain, sensory disturbances and muscle weakness. Similarly, a polyneuropathy of the feet, which may arise as a result of chemotherapy.

In addition to these more common causes, there are other more local causes of nerve damage. The interdigital nerves that run between the toe bones can be permanently irritated, for example due to incorrect footwear. In response, these so-called neurinomas can form, benign neoplasm of nerve tissue, which, however, can damage the nerves by pressure. The consequences are pain in the foot, which increases when wearing tight shoes.

In the hand

Numerous different causes are involved in damage to nerves in the hand. First and foremost, here is the carpal tunnel syndrome. In this condition, the median nerve is narrowed around the wrist, which can lead to pain and loss of function.

In addition to this known syndrome, however, all three major nerves of the hand: median nerve, radial nerve and ulnar nerve can be damaged by various causes. These include surgical procedures, venipunctures, fractures or sharp cuts. The ulnar nerve in particular is susceptible to chronic pressure due to its position in the inner palm of the hand. These include, for example, the daily longer use of screwdriving or holding a bicycle handlebar.

differential diagnosis

The symptoms of a nerve injury can also be caused by other disorders. A muscle or tendon tear can also cause muscle paralysis (muscle paralysis) and should not be confused with nerve damage.

Nerve damage and repair (December 2019).


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