What is polyneuropathy?

Polyneuropathy is the generic term for various diseases in which nerves of the peripheral nervous system are damaged. Literally translated, polyneuropathy means something like "multiple (poly) nerve disease (neuropathy)".

The peripheral (peripheral: on the edge) nervous system includes all nerves that lie outside the brain and spinal cord (both form the central nervous system).

It is nerves that:

• lead from the skin to the brain and perceive sensitive sensations such as touch, temperature, pressure and pain stimuli (sensitive nerves)
• Direct commands from the brain to the muscles and thus regulate muscle activity (motor nerves)
• control and regulate breathing, digestion, metabolism and bladder function (autonomic nerves)
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Which area of ​​the nerve cell is damaged?

Every nerve cell (neuron) consists of a cell nucleus, cell body and tubular extensions. The long appendages (axons) are, so to speak, the electrical cables that transmit information to other cells. In order to ensure faster transmission of the electrical impulses and to avoid short circuits, the nerve processes are covered with a thin layer of fat (the so-called myelin layer).

In polyneuropathy, the nerve damage can affect the nerve process. Doctors call this axonal polyneuropathy . If the surrounding myelin layer is damaged, it is a demyelinating polyneuropathy .

The nerve damage leads to the fact that the exchange of information between the brain, spinal cord and the rest of the body is disturbed. For example, pains signals are sent to the brain for no reason, muscles are no longer properly controlled or temperatures are no longer correctly perceived.

If the nerve disease occurs mainly in areas of the body that are remote from the trunk (hands, feet), doctors speak of distal polyneuropathy . Areas close to the trunk are much less often affected by the polyneuropathy. Proximal polyneuropathy is the name given to it.

How often does polyneuropathy occur?

A polyneuropathy (also "peripheral polyneuropathy" or "peripheral neuropathy" = PNP) is a common nerve disease. It occurs especially in diabetics whose blood sugar level is not well controlled over the long term. Then, due to the increased blood sugar levels, not only the blood vessels but also the nerves are damaged. Up to 50 percent of diabetics are affected by polyneuropathy. Nerve damage also occurs more frequently in alcoholics. In general, men get it twice as often as women. The average age of onset is around 65 years .

Polyneuropathy: causes

Research now knows more than 200 different causes of polyneuropathy. The two most common triggers are: 

• Diabetes mellitus : If the blood sugar level is poorly controlled, there is too much sugar in the bloodstream. The sugar molecules form compounds with various proteins that attack the nerve cells and can permanently damage them. In addition, the permanently increased blood sugar affects the fine blood vessels that surround the nerves. As a result, the nerve cells are no longer adequately supplied with oxygen and nutrients. Because of this undersupply, the nerves no longer function properly and can die over time. Doctors refer to the nerve damage caused by diabetes as diabetic polyneuropathy . It is the most common type of polyneuropathy and can cause bothType 1 and type 2 diabetes can occur.
• Alcohol abuse : Long-standing alcoholism can damage nerves and cause polyneuropathy. On the one hands, this is due to the fact that alcohol and its breakdown products have a toxic effect and attack the nerves. On the other hand, many alcoholic people eat one-sidedly. A deficiency in vitamin B1 (it supports the transmission of stimuli) and a vitamin B12 deficiency are more common. The vitamin plays a central role in the structure of the nerve sheaths.

Diabetes mellitus and alcohol abuse together are responsible for almost half of all neuropathies.

Other causes of the polyneuropathy are:

• Vitamin deficiency - due to a one-sided diet such as veganism
• Diseases such as kidney or liver disease, gout
• Chronic inflammation
• Cancer - a polyneuropathy can be the first sign of cancer
• One form of polyneuropathy - chronic inflammatory demyelinating polyneuropathy (CIDP) - is often associated with other diseases. Examples are diabetes mellitus, hepatitis C , systemic lupus erythematosus or an HIV infection.
• Hypothyroidism or hyperthyroidism
• Autoimmune diseases like Guillain-Barré syndrome - it destroys the nerve sheaths of the peripheral nerves
• Some medications can cause neuropathy as a side effect. Examples: proton pump inhibitors (reduce the production of stomach acid), agents against cardiac arrhythmias , immunosuppressants or preparations against cancer (e.g. cytostatics = chemotherapeutic agents, checkpoint inhibitors or targeted drugs such as tyrosine kinase inhibitors). The nerve damage can persist for years after chemo. 
• Radiation therapy for cancer
• Poisons such as arsenic or lead, solvents (for example benzene)
• Infections with some viruses or bacteria (for example herpes simplex, shingles , glandular fever , HIV, borreliosis , diphtheria, typhoid)
• Polyneuropathy is also inheritable in some cases. An example of this are hereditary motor-sensitive neuropathies (HMSN), in which the motor nerves are primarily affected. Inherited polyneuropathies are rare, however. Most people acquire the nerve damage during their lifetime.

Although stress itself does not cause polyneuropathy, it can promote other diseases such as shingles and thereby promote nerve damage.

Despite detailed medical diagnostics , the cause of the nerve condition remains unclear in every fifth patient . Doctors then speak of an idiopathic polyneuropathy.

Polyneuropathy: disease course and life expectancy

Basically, the earlier doctors recognize and treat a polyneuropathy, the more favorable the prognosis is, as a rule. However, the nerve disease often develops insidiously. Many sufferers rate initial symptoms such as a tingling sensation in the hands or feet as disturbing, but harmless. Only if you have severe symptoms, such as pain, do you consult a doctor. Often the polyneuropathy is already advanced and the nerve damage cannot be reversed (irreversible). With the right therapy, however, the symptoms can usually be alleviated and further nerve damage prevented.

In severe cases, when internal organs are already weakened due to nerve damage, the polyneuropathy can be fatal.

Polyneuropathy: symptoms

The symptoms of polyneuropathy depend on which nerves are damaged in which areas of the body. If, for example, the motor nerves in the leg are damaged, muscle weakness or muscle twitching can result. Some complaints arise because the nerve function fails, others because the nerves overreact.

In the early stages of nerve damage, many people experience tingling or numbness in the extremities (e.g. hands, toes). In later stages of polyneuropathy, serious functional restrictions of muscles or organs can arise. About 50 percent of patients experience nerve pain (neuropathic pain). The reason is that because of the nerve damage, pain signals are sent to the brain for no reason. In addition, the body's own mechanisms for inhibiting pain no longer function properly. 

Usually both arms, legs or feet are affected by the symptoms . Doctors call this  symmetrical polyneuropathy . If they only occur on one side of the body, it is an asymmetrical polyneuropathy .

 

If the sensitive nerves are affected by the polyneuropathy, the following symptoms occur:

• Tingling sensation ("pins and needles"), furry feeling, or numbness (in the toes, fingers, feet, or hands at the onset of the disease)
• the skin is very sensitive to touch, often even when the clothing is pressed lightly
• burning, stabbing pain
• Even the smallest stimuli can trigger pain - people with polyneuropathy perceive this much more strongly than healthy people
• a feeling of "being on cotton wool"
• itching
• Feeling of "being constricted"
• Swelling
• Reduced temperature sensation - those affected no longer perceive heat properly, for example when taking a footbath or when walking on hot sand in summer. Thereby, a combustion arise
• impaired pain perception, painless wounds (especially on the feet)
• Problems with the body balance, unsteady gait (especially in the dark) - it can lead to falls
   

If the motor nerves are affected by the polyneuropathy, the following symptoms arise:

• Muscle weakness - for example, objects fall out of the affected person's hand
• Weak reflexes
• Muscle twitching (fasciculations)
• Involuntary muscle movements, muscle spasms
• In severe cases, muscle paralysis or muscle wasting (muscle atrophy) can occur.
• An early sign of nerve damage can be a weakening of the muscles that are responsible for spreading the toes and the skeletal muscles on the back of the foot (toe extensors).
   

If the autonomic nerves are affected by the polyneuropathy, the following symptoms occur:

• Diarrhea , constipation
• Feeling of fullness , stomach paralysis (gastroparesis)
• Difficulty swallowing (esophageal dystonia)
• Dry, thin skin, decreased perspiration
• Lack of feeling when filling the bladder - difficult or unwanted urination
• Fast heartbeat (even at rest), palpitations , cardiac arrhythmias  
• Erectile dysfunction
• Unusually low blood pressure when you stand up from a sitting or lying position (orthostatic hypotension) - this can cause dizziness and fainting .
• Breathing problems, respiratory failure
• Pupillary disorders (slow pupil reaction, sensitivity to glare, vision problems when entering dark rooms or at night) or paralysis of the eye muscles
   

In diabetic polyneuropathy , there is often a burning, stabbing pain in the feet (“Burning Feet Syndrome”). 

The symptoms are particularly noticeable when you are resting and during the night. In addition, the transmission of stimuli is impaired by stronger nerve damage. Those affected then hardly notice temperature differences and pain, or not at all. For example, they often do not notice small wounds on their feet or only notice them late. The wound can become infected and become more severe. If the infection has progressed to the bone, an amputation may be necessary.

Polyneuropathy: diagnosis

For the diagnosis of polyneuropathy is a detailed Untersuchungsgespräc h between you and your doctor or health care professional is very important. This enables the doctor to find out about your medical history (anamnesis) and to draw initial conclusions about a possible illness. For example, the following questions are important:

• What are your symptoms and when did they first appear?
• How and on which parts of the body do they express themselves?
• How intense are the complaints?
• Do you have an underlying disease such as diabetes or kidney disease that can cause nerve damage?
• Do you have problems getting up from the armchair, squatting or climbing stairs? (Indication of a proximal nerve weakness)
• Do you stumble often? (Indication of distal weakness)
• Do you drink alcohol and if so, in what quantities? (Indication of alcohol-related nerve damage)
• Have you had cancer therapy in the past or are you taking medication that can cause nerve damage?

Many doctors also use a standardized questionnaire for this.

Then a neurologist will do a physical exam and use various tests to check:

• how your reflexes work
• How your motor skills work - do you have muscle weakness, such as lifting your toes?
• whether you have sensory disorders, such as decreased sensitivity to pressure or touch on the skin
• whether your pupils respond more slowly - this may be an indication of damage to the autonomic nerves

In addition, doctors can have the blood values ​​determined in the laboratory. Examples are kidney and liver values, blood sugar or vitamin levels. The blood test provides information on alcohol abuse, among other things.

In addition, doctors can carry out special tests that allow further conclusions to be drawn about polyneuropathy. The most important are:

• Electromyography : The procedure measures electrical tension in the muscle. Neurologists can thus determine a conduction disorder of the nerves.
• Electronurography : In this method, doctors conduct electricity through the peripheral nerve pathways. Delayed transmission of the signals can indicate nerve damage.
• With a tuning fork , the doctor can test how sensitively deeper tissue reacts to vibrations. You tell the doctor when you can no longer feel the vibrations on your skin.
• Thermode: A method that works with computer-controlled temperature stimuli. This is how you can check your perception of temperature. Patients with polyneuropathy usually only perceive heat from temperatures higher than 38 ° C.
• Nerve-muscle biopsies : Doctors take a tissue sample - usually from the shin - and then examine it in the laboratory. The biopsy can help identify the cause of polyneuropathy. For example, it can be determined whether the nerve damage was caused by the nerve itself or its protective covering (myelin layer).
• A lumbar puncture , in which doctors take fluid (CSF) from the spinal cord, is only done if doctors suspect other diseases (such as cancer).

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