Neuropathy is a collective term for many diseases of the peripheral nervous system , as it has been naturalized purely symptomatically, especially in the case of polyneuropathies . But the term is also used for central diseases of the nervous system, such as a constitutionally anchored tendency to vegetative dysfunction , so u. a. in pediatrics . Historically, this term was also used for neurosis and neurasthenia . Primary diseases of the peripheral nerves are rather rare. However, neuropathies secondary to other diseases (e.g. diabetes mellitus ) or neurotoxic substances (e.g. alcohol ) are common.
In polyneuropathy several nerves are affected , in mononeuropathy or neuralgia only one nerve of the peripheral nervous system is affected.
Etiology of the primary neuropathies
Primary, d. H. Diseases originating from the nerve itself are usually inherited . This includes the following diseases:
- Hereditary motor-sensitive neuropathies (HMSN I-VII)
- Hereditary sensory neuropathies (HSN)
- Hereditary sensory-autonomic neuropathies (HSAN IV)
- Hereditary Motor Neuropathies (HMN IV)
- Hereditary Motor Neuropathies (HMN VX)
- Hereditary neuropathy with a tendency to pressure lesions (HNPP)
Constitutional functional symptoms in paediatrics with vegetative symptoms are referred to as neuropathies, which are associated with laziness to drink, habitual vomiting, defecation disorders, sweating, a tendency to rise in temperature, etc. An increased sensitivity to stimuli with an excessive response to stimuli is assumed.
Etiology of secondary neuropathies
This group includes v. a. Pathogen- related diseases. Infections by varicella , Mycobacterium leprae and Borrelia burgdorferi lead to an infection of the peripheral nerve or the neuron. The body's own immune system tries to eliminate the pathogens and thereby usually destroys the neuron or the myelin sheath.
In this group is v. a. to name the Guillain-Barré syndrome . With autoimmunological diseases, the immune system attacks the body's own components, here the nerves or the myelin sheaths . Today it is assumed that the cause of the disease was caused by an infection by a pathogen against which the immune system cross-reacts , i.e. H. the body's own cells also form defensive substances that attack them. Campylobacter jejuni in particular seems to induce cross-reacting antibodies with gangliosides of the myelin . Usually only the myelin sheath is affected, so that in the neurographs v. a. a reduction in nerve conduction velocity can be found. Clinically, in Guillain-Barré syndrome v. a. flaccid paralysis that is reversible. It is dangerous, however, that the disease can also affect the nerves supplying the diaphragm ( phrenic nerve ). Do you have Guillain-Barré syndrome v. a. If the cranial nerves are affected, one also speaks of the Miller-Fisher syndrome .
A subgroup of HIV-positive patients develop immune complex-mediated peripheral neuropathy. The working group around Robert Miller / San Francisco, which in 1988 essentially described four variants of clinically differentiated clinical pictures of HIV neuropathy:
- distal sensorimotor polyneuropathy,
- chronic inflammatory demyelating polyneuroradiculitis,
- Multiplex mononeuropathy
- Progressive polyradiculitis.
The histological evidence of circulating antibodies against myelin and therapeutic approaches using plasmapheresis were successful.
This group includes metabolic disorders of the neuron or the myelin sheaths ( Schwann cells ). The cause for this come z. B. intestinal diseases , diabetes mellitus , sprue and the resulting vitamin deficiency states such as thiamine deficiency ( beriberi ), liver and kidney diseases , Refsum's syndrome and thyroid disorders . By far the most common is diabetes mellitus as a (secondary) trigger or companion of neuropathy. Here there are often distally stressed polyneuropathy , but also a painful multiplex mononeuritis . The autonomic nervous system is often involved. This can result in vegetative disorders .
This group includes impairments of the neuronal metabolism or the metabolism of the myelin sheaths caused by so-called neurotoxins :
- Cyclic hydrocarbons (e.g. benzene , phenol ) and other solvents (VOC)
- Mycotoxin (mold toxins)
- Fluoroquinolone antibiotics
- Chemotherapy drugs
- Heavy metals
- Methanol and formaldehyde
- Ethanol could have a direct neurotoxic effect, although it is difficult to distinguish it from the vitamin deficiencies that are common in alcoholics
Localization of the damage
- Axonopathy : Here one finds an axonal death with an initially preserved nerve sheath. If the number of neurons decreases, the total nerve potential decreases . This form of damage is found in inherited, toxic, and metabolic neuropathies.
- Neuronopathy : This is the location of the damage in the cell body of the neuron (e.g. inherited metabolic diseases ). Strictly speaking, neuronopathy does not count among the peripheral neuropathies.
- Demyelination : Here the damage is not in the neuron, but in the myelin sheath. This reduces the nerve conduction speed. Etiologically, metabolic diseases and disorders in the synthesis of myelin are often found .
- History : The patients report a lack of perception ( negative symptoms ) or sensory disorders such as tingling, pins and needles, burning (positive symptoms)
- Inspection: Noticeably dry skin can be an indication of neuropathy if the infection is symmetrical.
- Reflex test of the patellar tendon and Achilles tendon reflex. In the absence of ASR, polyneuropathy is suspected.
- Differentiation between cold and warm: the patient should be able to differentiate between a cold metal surface of approx. 1.5 cm in diameter and a plastic surface of the same size when touching the sole of the foot.
- Sensitivity test with the Semmes-Weinstein monofilament : this is a nylon thread that exerts a defined pressure of 0.1 Newton by bending. The filament is z. B. placed on the ball of the foot between the 1st and 2nd metatarsophalangeal joint. The patient is first asked to close his eyes and indicate the location of the contact. If there are 5 points of contact, at least three should be specified correctly.
- Investigation of the vibration sensation with the tuning fork according to Rydel and Seiffer : The solid metal tuning fork according to Rydel and Seiffer has a frequency of 128 Hz, which is reduced to 68 Hz by 2 screw-on metal blocks. There are two acute-angled triangles on the metal blocks, which intersect when the fork is swinging and, using a scale with 8 subdivisions, allow the strength of the vibration to be determined up to which the patient can still perceive the vibration. During the oscillation, a virtual triangle moves from 0/8 to 8/8. Normal is over 6/8 up to the age of 50, over the age of 50 up to 5/8. If there is less or no awareness, a polyneuropathy is suspected.
- Electronurography : Measurement of the nerve conduction velocity and the total nerve potential on subcutaneous nerves. Reduction of the nerve conduction speed is found in diseases of the myelin sheath ( demyelination ). In contrast, with axonal damage patterns, the total nerve potential is reduced.
- Pathological diagnosis: Removal of a piece of the sural nerve . This lies relatively superficially under the skin of the lower leg and after removal has only a slight loss of sensitivity in the area of the lower leg. Investigations are usually carried out on normal paraffin sections , semi-thin sections and with the help of electron microscopy .
Autonomous neuropathy typically occurs in diabetes mellitus and affects the autonomic nervous system . It can affect almost any organ system and is characterized by a variety of symptoms. Pronounced complaints are relatively rare. They often only appear after a long period of diabetes. The most important organs and the associated symptoms include:
- Cardiovascular system: increased resting heart rate , dizziness and drop in blood pressure when standing up, heart attack without typical pain
- Esophagus, stomach: difficulty swallowing, nausea, vomiting, feeling of fullness, feeling of fullness early after meals, hypoglycaemia after meals ( gastroparesis )
- Small intestine, large intestine: diarrhea, especially at night, constipation, gas, bloating
- Urinary tract and genital organs: belated urge to urinate, bladder overcrowding , weak urine stream, erectile dysfunction
- Hormonal balance: decreased or no awareness of hypoglycaemia ( hypoglycaemia perception disorder )
- Sweat glands: dry, chapped skin in the area of the feet and lower legs, increased sweating during meals
- Foot: swelling of the lower legs (neuropathic edema), deformities and loss of bones
- Autonomous neuropathy (see above)
- Mononeuritis multiplex
Therapy of neuropathy
- The therapy of neuropathies depends on the underlying disease.
- In the case of congenital neuropathies (see above), causal therapy is often not possible.
- If the cause is bacterial infection , antibiotics are used .
- Immune complex-mediated autoimmune neuropathies (e.g. Guillain-Barré or HIV-associated neuropathies) can be improved significantly with immunapheresis.
- If the cause is viral, a causal therapy of the neuropathy is usually not possible.
- If the cause is toxic, omitting the noxious agent (e.g. alcohol, medication) can lead to a recovery of the nerve function.
- In metabolic neuropathies such as B. diabetic polyneuropathy, a normal blood sugar control can lead to a recovery of the nerve function, but sometimes only a further deterioration can be prevented.
- In the case of symptomatic neuropathies (burning sensation, pain, etc.), therapy with medication may be necessary (e.g. alpha-lipoic acid , vitamins of the B group, opioids , opiates , amitriptyline , carbamazepine , gabapentin , pregabalin, etc.)
- Spinal cord stimulation can be effective for neuropathies that do not respond to causal therapy .
- There are positive individual case descriptions about naturopathic, homeopathic and alternative methods such as acupuncture , magnetic field therapy or high-tone therapy .
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- Gesundheitpro.de An explanation of polyneuropathy that is understandable for laypeople at Gesundheitpro.de
- Neuropathy in Adult Diabetes National Care Guideline, 2011 (PDF) on the AWMF website
- Neuromuscular Disease Center - excellent Washington University (USA) web site, especially the Neuropathy - Differential Diagnosis section
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- deutsche-diabetes-gesellschaft.de (PDF; 3.4 MB) Diagnosis, therapy and follow-up of neuropathy in diabetes mellitus type 1 and type 2, guideline DDG 2004.