Neurology-Online

Nerve damage

Synonyms

Nerve damage, nerve lesion, nerve injury

English: nerve damage, nerve injury

definition

Nerve damage is a Injury to nerve tissue, the objectively detectable Failures of the nerve shows. The problem with nerve lesions is that this tissue is only one limited ability to regenerate owns why a permanent damage may remain.

Classification of nerve damage

Nerve damage is classified according to the location of the injury, this is how you distinguish one

central nerve damage in the area of the central nervous system and
peripheral nerve damage that is outside of the skull and spinal canal.

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

Neurapraxia: Here the axon and its shell structures are preserved.
Axonotmesis: The axon is interrupted, its envelope structures are completely preserved.
Neurotmesis: Both the axon is interrupted and the envelope structures are wholly or partially injured. An axon is a tube-like nerve cell extension that lies in a sheath of glial cells. The combination of axon and envelope structure is known as the nerve fiber.

Classification of nerve damage

Another classification is that of

acute and
chronic nerve damage

Both acute nerve damage it is often a matter of direct trauma, i.e. direct effects on the nerves. This can be done mechanically e.g. be injured by a scalpel during an operation or by an injection or knife stab. These are "sharp" injuries.
One speaks of "blunt" injuries when it is a question of nerve compression. For example, a bruise or abscess presses on the nerve.

At chronic nerve compression if there is an external mechanical influence, e.g. in carpal tunnel syndrome. They prevent a good blood flow in the nerve tissue and damage the myelin sheath (covering the nerve).

So-called vibration damage occurs in half of all people who have to work with vibrating objects such as a jackhammer for years. This also includes tingling sensations in the arms and increased fatigue in the hands.
In the nerves there can be a multifocal demyelination come. This means that the myelin sheath that surrounds the nerve decreases and at the same time the nerve conduction speed slows down. Multifocal means that this occurs in several places on the nerves.

By a Injection into an arterial vessel vasospasm (contraction of the vessels) can occur. This clasp prevents blood flow to the nervecausing an acute so-called ischemic injury occurs.

Chronic ischemic nerve damage can lead to the disease Vasculitis occurrence. Damage here Inflammation the vessels supplying nerves. Metabolic disorders like that Diabetes mellitus can also lead to chronic ischemic nerve lesion.

Toxic effects can be acutely caused by a Injection of toxic solutions arise in or next to the nerve. The noxious alcohol can be chronic if it is long-lasting Alcohol abuse to a Polyneuropathy to lead.

Immunologically, for example, nerve damage can result Antibody formation arise that damage the nerve or its envelope structures. Kick often severe pain in one limb on.

Pathogens can cause nerve damage either directly or indirectly through their toxins. Especially the Nerve root is susceptible to the effects of pathogensbecause it is not understandable anywhere in the body with a protective layer.
Herpes viruses for example, in Spinal ganglion remain and one Nerve inflammation cause. Also Myctobacterium leprae, HI virus and Borrelia can damage the nerve.

Radiation can cause acute or chronic damage to the nerves. Usually the symptoms appear with a little delay. Genetic, i.e. hereditary, nerve lesions can, for example, occur in the Multiple sclerosis or at the Amyotrophic lateral sclerosis occurrence. The genetic clinical picture is often neurodegenerative (i.e. the nerve tissue gradually shrinks) and only gets worse with age.

Thermal nerve damage concern above all marrow-free (hull-free) nerve fibers and the small ones nerve-supplying Blood vessels.
In addition to the causes of nerve damage mentioned above, there are still other unexplained reasons that damage the nerve tissue and cause an objectively tangible failure.

Symptoms

Typical signs of a nerve injury are, on the one hand, the impaired sensitivity in the supply area of the nerve and, on the other hand, the loss of motor performance in the muscle, which is only supplied by this one injured nerve. Furthermore, there is a disturbed pain sensation and an inhibited two-point discrimination. Two-point discrimination means that two stimuli placed next to one another are no longer perceived as two different ones, but as one.

Objects can no longer be distinguished as pointed or blunt. Another sign is the defect in depth sensitivity and the sense of position. The vegetative nerve tissue can also have been injured and the skin temperature can change and perspiration is impaired. Pain that is located in a supply area of a nerve and is triggered by this will also be neuralgiform pain.

Also read: These symptoms will help you recognize inflammation of the nerves

Duration of healing of a nerve damage

The healing time of nerve damage depends primarily on the extent of the damage. Minor damage that only caused damage to the nerve envelope usually heals within a few days. If the transection is incomplete, it can also only take a few weeks before the complete neurological function of the nerve is restored. It is more complicated with complete nerve cuts. The basic requirement for nerve generation here is that the nerve cell body is undamaged, which is usually the case.

2-3 days after damage, axons begin to regenerate and grow at an amazing rate of 0.5-2 millimeters per day. The regeneration begins at the severed end of the axon. The independent regeneration of the nerve does not take place through renewed growing together of the two ends, but through a complete new formation of the nerve behind the lesion. In the case of nerve damage in the forearm, for example, it can take 3-6 months for the nerve fibers to grow back completely and to be able to resume their function. For such a new sprouting, however, intact connective tissue nerve sheaths are necessary as a guide structure.

Find out more about the topic here: Numbness

Cause of nerve damage

There are various causes that injure such a delicate structure as nerve tissue and so on permanent damage being able to lead. These include:

mechanical damage or trauma
Vibration damage
Ischemia (Circulatory disorder)
toxic effects
Damage to the immune system (Autoimmune disease)
by Pathogen caused lesions (Infection)
radiotherapy
genetic injuries of the nerves (DNA damage)
Electrotraumas and
Nerve injuries unclear cause
Piercing the tongue (Tongue piercing)

After an operation

Depending on the area of operation, there is a small risk of nerve damage during an operation. This mainly affects larger orthopedic operations on the extremities, but also in the upper neck area. But even smaller operations, such as carpal tunnel syndrome, can lead to nerve damage. It is assumed that approx. 15% of all known nerve damage occurs during an operation.

If it is recognized that a nerve was damaged during the operation, the further course of action depends largely on the extent of the damage. Small damage to the outer sheath of a nerve does not require any further treatment. However, if a nerve is completely severed, it is usually treated surgically or in a follow-up operation.

For all moderate nerve damage that has not been completely severed, a wait-and-see approach is recommended to give the nerves the chance to regenerate independently. If this is unsuccessful, surgical repair of the nerve damage is usually carried out. There are usually no legal claims from the patient's point of view in the event of nerve damage, as this complication is often included in the information provided.

After chemotherapy

Some chemotherapeutic agents can lead to so-called neuropathy. This disease, which usually affects the hands and feet, is usually perceived by those affected as an uncomfortable tingling sensation. However, numbness or muscle weakness can also occur. If several areas of the body are affected by this phenomenon, one speaks of a polyneuropathy.

However, this is usually only temporary and subsides a few weeks after the end of chemotherapy. Overall, around a third of all chemotherapy patients are affected by polyneuropathy. In some cases, however, this clinical picture can also be chronic and the nerve damage permanent. This particularly affects the patients who were already very pronounced during chemotherapy.

Read more about the topic here: Symptoms of polyneuropathy

After a herniated disc

If a prolonged pressure load on the spinal nerves occurs as a result of a herniated disc, the result can be damage to the nerves. In addition to pain, such damage is usually associated with a variable loss of neurological functions. How this loss presents itself depends, in addition to the extent of the damage, primarily on the level of nerve damage. For example, herniated discs in the neck and chest area, the sensitivity and the muscles of the arms and trunk can be affected, whereas in a lower position, the legs can show a loss of function. The extent to which the damaged nerve regenerates depends on the exact damage pattern and the duration of the pressure load. In the area of the spinal nerves, however, a slow regeneration process must be assumed.

Find out more about the topics here:

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

After regional anesthesia

There are various surgical procedures in which regional anesthesia is used, such as that of the arm and shoulder by injecting local anesthetics into the armpit.

The most common nerve damage after regional anesthesia is the ulnar nerve or the entire brachial plexus, a plexus of nerves that supplies the arm with neurological supply. Damage to the nerves occurs here, on the one hand, through contact between the needle tip and the nerve itself.

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

Find out more about the topics here:

Side effects of local anesthesia
Peripheral nerve block

Carpal tunnel syndrome

Carpal tunnel syndrome is a relatively common disease in the population. Women who have to carry out repetitive tasks with their hands at work are particularly affected. With 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 too narrow a limitation of the area in the wrist through which blood vessels, nerves and muscle tendons run. The upper limit, which is relevant for therapy, is called the ligamentum carpi volare.

Symptoms of carpal tunnel syndrome are pain and sensory disorders in the thumb, index finger and above all. of the middle finger. They usually start at night and then appear during the day as the disease progresses. The sensitivity disturbance usually leads to a loss of the "fingertip feeling" and smaller, precise activities are significantly more difficult.

Therapy for carpal tunnel syndrome initially consists of immobilizing the wrist and possibly using steroids or local anesthetics locally. If this does not improve, the ligament described above is surgically split.

Read more on the topic here: Causes of Carpal Tunnel Syndrome

therapy

It is possible to treat nerve damage conservatively or surgically. However, it depends on the type of damage. In the case of diabetes mellitus or other metabolic diseases and vascular disease patterns, conservative measures can lead to a cure. If the nerve is damaged by pressure, surgical relief should be performed.

In chronic nerve compression such as in the case of carpal tunnel syndrome, the area should be immobilized using a splint. In addition, anti-inflammatory drugs are prescribed and physical therapy is recommended. If it continues to deteriorate, the carpal tunnel syndrome must be treated surgically. 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, i.e. no alcohol in alcoholic induced polyneuropathy. Depending on the underlying cause of the nerve damage, you can also intervene with medication. With diabetes mellitus, blood sugar should be well controlled. In the event of a vitamin deficiency, vitamin preparations can remedy the deficiency.

The chances of recovery are, in turn, related to the type of lesion. So it seems pretty logical that a Neuropraxia (here the axon and its shell are preserved) or one Axonotmesis (the axon is interrupted, but its envelope structure is retained) have a better prognosis than one Neurotmesis. If the nerve is completely or partially interrupted, permanent functional impairment is to be expected.

Read more on the topic: What are the chances of recovery after a cerebral hemorrhage?

The longer the nerve lesion lasts and the closer it is to the central nervous system, the worse the prognosis for complete healing. If the nerve damage is long, the risk of one increases Misinervation, i.e. that the nerve no longer grows together with its own nerve, but grows into another supply area.

Diagnosis

Through an accurate clinical examination the doctor can find out if it is a nerve lesion and where it is located. It will be the

sensitive
motor and
vegetative Functions

of the nerve in the area of its supply. It can do that too Hoffmann-Tinel sign being checked. Here you knock on the nerve and wait Paresthesia such as tingling in the innervation area of the nerve. Furthermore, clinical tests such as a Neurography and a Electromyography be performed.

When is the nerve dead?

There are two scenarios that can lead to a nerve no longer being able to regenerate after damage, which means that it is "dead". The "dying" of the nerves is usually expressed in the abrupt subsidence of the previous nerve pain or acute paralysis.

One possible cause of nerve death is damage to the nerve cell body. The energy is provided in the cell body of a nerve cell and the various building blocks for a successful regeneration of the axon are produced. If this cell body is damaged, these functions can no longer be performed, resulting in a lack of regeneration.

The second possibility is grade 5 nerve damage. This describes a complete severing of the nerves including the surrounding connective tissue nerve sheath. Since the latter serves as a lead structure for the regeneration of the axons, a severance of the axon can no longer lead to targeted regeneration of the nerve. Only nerve cell overgrowth is formed, but it has no neurological functions.

Nerve damage in the body

In the legs

Nerve damage in the legs can be caused by many different causes. In addition to nerve damage or severance during an operation, diabetes mellitus, for example, can lead to permanent nerve damage to the legs, especially the feet. Here, nerves are damaged as a result of long-term high blood sugar levels and this leads to sensitivity disorders, a tingling sensation or pain described as burning or boring. However, the feet are one of the most common sites of chemotherapy polyneuropathy. Clinically, this is very similar to neuropathy in diabetes. Another possible cause of damage to nerves that perform neurological functions in the leg is constrictions in the area of the nerve exit from the spine. These include, for example, herniated discs, but also foraminal stenoses, in which the outlet canal on the spine is narrowed. Rarer causes are 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

Various causes can lead to nerve damage in the foot. First of all, a long-standing diabetes mellitus should be mentioned here. As a result of persistent high blood sugar levels, this can lead to chronic nerve damage, which usually begins in the feet. The consequences are pain, sensory disorders and muscle weakness. A polyneuropathy of the feet, which can arise as a result of chemotherapy, is similar.

In addition to these more common causes, there are other more local causes of nerve damage. The interdigital nerves running between the toe bones can be permanently irritated, for example by using the wrong footwear. In response, these can develop so-called neuromas, benign new formation of nerve tissue, which, however, can damage the nerves through pressure. The consequences are pain in the foot, which is exacerbated when wearing tight shoes.

In the hand

There are many different causes of damage to the nerves in the hand. First of all, the carpal tunnel syndrome should be mentioned here. In this clinical picture, the median nerve in the area of the wrist is narrowed, which can lead to pain and malfunctions.

In addition to this well-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 interventions, venipuncture, fractures or sharp cuts. The ulnar nerve in particular is prone to chronic pressure due to its location in the palm of the hand. This includes, for example, using screwdrivers longer every day or holding a bicycle handlebar.

Differential diagnosis

Nerve injury symptoms can also be caused by other medical conditions. A muscle or tendon tear can also be one Muscle palsy (Muscle paralysis) and should not be confused with nerve damage.