Synonyms
nerve damage, nerve lesion, nerve injury
Classification of nerve damage
Nerve damage is classified according to the location of the injury, so one distinguishes an additional nerve damage can be distinguished according to the type of damage:
- Central nerve damage in the area of the central nervous system and
- Peripheral nerve damage located outside the skull and spinal canal.
- Neurapraxia: Here the axon and its envelope structures are preserved.
- Axonotmesis: The axon is interrupted, its envelope structures remain completely intact.
- Neurotmesis: Both the axon is interrupted and the envelope structures are partially or completely damaged. 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 called nerve fiber.
Classification of nerve damage
A further classification is that of acute nerve damage, which is often direct trauma, i.e. direct impact on the nerves. The nerve can be injured mechanically, e.g. by a scalpel during an operation, or by an injection or a knife thrust. These are “sharp” injuries.
One speaks of “blunt” injuries when it is a nerve compression. For example, a bruise or abscess presses on the nerve. In chronic nerve compression, there is a mechanical influence from outside, such as in carpal tunnel syndrome.
They prevent good blood flow to the nerve tissue and damage the myelin sheath (the nerve sheath). Half of all people who have to work with vibrating objects such as a pneumatic hammer for years suffer so-called vibration damage. These include tingling sensations in the arms and faster fatigue of the hands.
Multifocal demyelination can occur in the nerves. This means that the myelin sheath surrounding the nerve decreases and at the same time the nerve conduction speed slows down. Multifocal means that this occurs at several points in the nerves.
- Acute and
- Chronic nerve damage
Injection into an arterial vessel can cause vasospasm (contraction of the vessels). This occlusion prevents the blood flow to the nerve, resulting in acute so-called ischemic damage. Chronic ischemic nerve damage can lead to the clinical picture of vasculitis.
Here, inflammation damages the vessels supplying the nerves. Metabolic disorders such as diabetes mellitus can also lead to a chronic ischemic nerve lesion. Toxic effects can be acutely caused by an injection of toxic solutions in or near the nerve.
Chronically, the noxious alcohol can lead to polyneuropathy in cases of long-term alcohol abuse. Immunologically, nerve damage can be caused, for example, by the formation of antibodies which damage the nerve or its sheath structures. Severe pain often occurs in one limb.
Pathogens can cause nerve damage either directly or indirectly through their toxins. The nerve root in particular is susceptible to pathogen effects because it is not understood with a protective layer everywhere in the body. Herpes viruses, for example, can remain in the spinal ganglion and cause nerve inflammation.
Myctobacterium leprae, HI virus and borrelia can also damage the nerve. Radiation can cause acute or chronic damage to the nerves. Usually the symptoms appear with some delay.
Genetic, i.e. hereditary, nerve lesions can occur in multiple sclerosis or amyotrophic lateral sclerosis, for example. The genetic clinical picture is often neurodegenerative (i.e. the nerve tissue gradually dies) and only gets worse with age. Thermal nerve damage mainly affects non-marrow (sheath-free) nerve fibers and the small blood vessels supplying the nerves.
In addition to the above-mentioned causes of nerve damage, there are still other unexplained reasons that damage nerve tissue and cause an objectively tangible failure. Typical signs of a nerve injury are on the one hand the disturbed sensitivity in the area supplied by the nerve and on the other hand the loss of motor power in the muscle, which is supplied only by this one injured nerve. Furthermore, a disturbed pain sensation and an inhibited two-point discrimination occur.Two-point discrimination means that two stimuli placed side by side are no longer perceived as two different stimuli but as one.
Objects can also no longer be distinguished as pointed or blunt. Another sign is the defect of depth sensitivity and sense of position. The vegetative nervous tissue may also have been injured and this can lead to altered skin temperatures and disturbed sweating. Pain that is located in a supply area of a nerve and is triggered by it also becomes neuralgiform pain.