Polyneuropathy: Symptoms, Causes, Therapy

Brief overview

What is polyneuropathy? A group of diseases in which peripheral nerves are damaged.
Symptoms: Depends on which nerves are damaged: Common symptoms include discomfort, tingling, pain and numbness in the legs and/or arms, muscle weakness, muscle cramps and paralysis, bladder emptying disorders, constipation or diarrhea, impotence or cardiac arrhythmia.
Severity: Grade 1 (mild) to grade 4 (life-threatening).
Prognosis: No cure possible in most cases. Existing functional limitations remain. However, progression of the disease can be slowed or – depending on the cause – stopped.
Examinations: Physical examination, electroneurography (ENG), electromyography (EMG), blood tests, etc.
Therapy: If possible, the cause is eliminated or treated. The symptoms can also be treated in a targeted manner (e.g. with medication, TENS, physiotherapy, alternating baths, wraps, orthopaedic aids).

What is polyneuropathy?

Polyneuropathies often develop as a result of an underlying pre-existing condition. Some such triggers include advanced diabetes mellitus (diabetic neuropathy), alcoholism (alcoholic polyneuropathy), certain infectious diseases, exposure to toxins (toxic polyneuropathy), as well as cancer or chemotherapeutic treatment for cancer.

Polyneuropathy is often also described as “peripheral polyneuropathy” or “peripheral neuropathy” (PNP).

Which part of the nerve cells is damaged?

Each nerve cell is made up of a cell body and a nerve extension (axon).

Axons can be thought of as electrically conductive cables. The body has to coat them with an insulating layer for optimum electrical stimulus or signal transmission. This is called the myelin layer or myelin sheath.

In polyneuropathy, different parts of these nerve processes can be damaged. A distinction is made:

Axonal polyneuropathy: The axon itself is affected. Axonal degeneration of the nerves is usually accompanied by more severe symptoms and has a significantly poorer prognosis.

In certain cases, both forms occur in combination, so that the myelin layer and axons are damaged in equal measure.

Forms of polyneuropathy

Depending on the severity and the part of the body where the nerve damage occurs, doctors differentiate between

Symmetrical polyneuropathies: The nerve damage affects both halves of the body.
Asymmetrical polyneuropathies: The nerve damage only affects one side of the body.
Proximal polyneuropathy: A rare form of neuropathy in which the disease is limited to the parts of the body close to the trunk.

How does polyneuropathy manifest itself?

Polyneuropathy can manifest itself in different ways depending on its severity. A distinction is therefore made between sensory, motor and autonomic disorders – which symptoms occur depends on the individually damaged nerves.

Polyneuropathy symptoms: Sensory nerves

Nerves that lead from the skin to the brain are called “sensitive” or sensory nerves. They transmit information from touch stimuli, the sensation of pressure, temperature or pain as well as vibrations to the brain.

The toes are often affected first. If the legs are affected, coordination problems can develop when walking. If the sensation of temperature is impaired, injuries – such as burns – can occur more easily.

People with pronounced polyneuropathy usually only perceive pain to a lesser extent. This can also increase the risk of injury.

Most polyneuropathies are accompanied by sensory disorders.

Polyneuropathy symptoms: Motor nerves

As a result, the affected muscles lose strength. In the worst case, muscle paralysis occurs. Muscle cramps are also possible. In advanced stages, affected patients may be dependent on mechanical aids (e.g. rollator, wheelchair).

As a general rule, if muscle tissue is insufficiently or no longer controlled via the nerves for a long time, it degenerates – it shrinks and shrinks. In severe cases, motor polyneuropathy can lead to muscle wasting (muscle atrophy). This happens particularly quickly in skeletal muscles (especially arm and leg muscles).

Symptoms of polyneuropathy: Autonomic nerves

If such autonomic nerves are damaged, complications can arise that severely restrict quality of life.

For example, if intestinal nerves are damaged in a polyneuropathy, the function of the gastrointestinal tract is impaired, which can lead to diarrhea or constipation. If the nerves that regulate bladder function are affected, urination, i.e. bladder emptying, is impaired.

Polyneuropathy symptoms at a glance

In the following table you will find important polyneuropathy symptoms at a glance:

Sensitive symptoms	Motor symptoms	Autonomic symptoms
Tingling, formication	Pupil disorders
Stinging	Muscle cramps	Water retention (edema)
Feeling of furredness and numbness	Muscle weakness	Ulcers
Feeling of being constricted	Muscle atrophy	reduced sweating
Feeling of swelling	Palpitations at rest
Feeling of uncomfortable pressure	Stomach paralysis (gastroparesis)
Feeling like walking on absorbent cotton	Diarrhea, constipation
Unsteady gait (especially in the dark)	Disturbed bladder emptying
Lack of temperature sensation	Impotence (erectile dysfunction)
painless wounds	Dizziness/fainting when getting up

In the case of polyneuropathy as a result of diabetes mellitus, the symptoms develop gradually. The sensitive nerve fibers are usually damaged first. Those affected then notice, for example, numbness or tingling in the legs. Many also feel a burning pain in their feet (“burning feet syndrome”).

You can find out more about the clinical picture of diabetic neuropathy here.

As blood circulation is often impaired in diabetes, diabetic foot syndrome can also develop. Read more about this here.

Alcoholic polyneuropathy: symptoms

In severe cases, polyneuropathy symptoms also develop in the eye area, such as pupil disorders and paralysis of the eye muscles.

What are the degrees of severity of polyneuropathy?

Doctors differentiate between the following degrees of severity according to the international criteria of the World Health Organization (WHO):

Grade 1: Mild symptoms with mild pain. Usually without the need for therapy. Possibly loss of deep tendon reflexes or abnormal sensations (paraesthesia, including tingling). Physical functions are not impaired. Muscle weakness may only be detectable during special nerve conduction tests.

Grade 3: Severe symptoms accompanied by severe pain. Pain therapy often necessary. Muscle weakness is pronounced at this stage. Mechanical aids such as walking stick, rollator or wheelchair often necessary. Paresthesia clearly pronounced.

Grade 4: Life-threatening symptoms in the final stage, accompanied by extreme pain, general signs of paralysis and deterioration of mental abilities. Internal organs are severely impaired in their function.

Can polyneuropathy be cured?

Basically, the earlier the nerve damage is recognized and treated, the better the prognosis – in some cases, polyneuropathy can even be stopped. Unfortunately, however, polyneuropathy often goes unnoticed and asymptomatic for a long time, so that the first mild symptoms are not taken seriously.

At the time of diagnosis, the disease is usually already well advanced. Often there is already irreversible (irreversible) nerve damage caused by the polyneuropathy. A complete cure is usually no longer possible. However, with the right treatment, attempts can be made to prevent further nerve damage and improve existing symptoms.

Autonomic neuropathies in very advanced stages can also reduce life expectancy, as vital organs are impaired in their function.

Why do you get polyneuropathy?

Polyneuropathy can have a variety of causes. Doctors now know of more than 200 different risk factors that promote the development of polyneuropathy.

The most common causes of nerve damage are diabetes (diabetic polyneuropathy) or alcohol (alcoholic polyneuropathy) – but other causes are also known.

Polyneuropathy with diabetes

Diabetic polyneuropathy is the most common form of polyneuropathy. It can occur in both type 1 and type 2 diabetes. A permanently elevated blood sugar level attacks the nerve cells and irreversibly damages them over time.

This initially impairs their function, and after a certain time the undersupplied nerves can even die. Diabetic polyneuropathy usually sets in gradually.

You can find out more about diabetic neuropathy here.

Polyneuropathy caused by alcohol

Alcohol is the second most common cause of polyneuropathy – especially chronic alcohol consumption. Here too, the exact mechanisms that lead to nerve damage are not yet fully understood, but it is known that certain alcohol breakdown products (including ethanal) directly damage the nerves.

However, this vitamin is very important for the function of the nervous system. A vitamin B12 deficiency could therefore additionally promote nerve disorders in alcoholics. This is because it can also trigger polyneuropathy on its own.

Polyneuropathy as a result of chemotherapy

A special case is polyneuropathy as a typical side effect of cancer treatment. It is also known as chemotherapy-induced neuropathy (CIN).

This disrupts the exchange of information between nerve cells and tissue. This leads to paraesthesia, burning pain and muscle weakness.

The following groups of active substances can promote polyneuropathy:

Platinum derivatives (e.g. cisplatin, oxaliplatin, etc.)
Vinca alkaloids (e.g. vinblastine, vincristine, etc.)
Taxanes (e.g. cabazitaxel, docetaxel, etc.)
Tyrosine kinase inhibitors (e.g. sunitinib, sorafenib, etc.)
Checkpoint inhibitors (e.g.: pembrolizumab, nivolumab, etc.)
Proteasome inhibitors (e.g. bortezomib, thalidomide, etc.)

It is estimated that around three percent of cancer patients are affected by short chemotherapy treatment periods, while up to 30 percent can be affected by multiple treatment cycles.

Of those affected who have developed such chemotherapy-induced polyneuropathy, eight out of ten treated cancer patients still suffer from nerve restrictions two years after treatment.

However, if peripheral neuropathy as a result of cancer treatment is recognized at an early stage and treated specifically, it often regresses.

Other causes of polyneuropathy

Other possible causes of polyneuropathy include

Kidney diseases
Liver diseases
Disorders of thyroid function (hypothyroidism and hyperthyroidism)
gout
Toxins (such as arsenic, lead)
Chemical solvents (e.g.: Hydrocarbons such as benzene or trichloroethene, alcohols such as methanol; therefore, toxic polyneuropathy is recognized as an occupational disease in certain occupational groups such as painters or floor layers – after appropriate testing)
certain acute infectious diseases such as Lyme borreliosis, diphtheria, HIV etc.
Guillain-Barré syndrome (an autoimmune disease)
Fabry disease (a congenital metabolic disorder)
Cancer (polyneuropathy can be the first sign here)

One example of this is dormant viruses that break out again under stress – for example the Epstein-Barr virus (trigger of Pfeiffer’s glandular fever), the varicella zoster virus (trigger of shingles) or herpes simplex (possible trigger of inflammation-related nerve pain).

More rarely, nerve damage is genetic. There are various congenital diseases that are accompanied by polyneuropathy. These include HMSN (hereditary motor-sensitive neuropathy), of which there are several subtypes.

In around 20 percent of all patients, however, the cause of the polyneuropathy remains unexplained. Doctors then speak of idiopathic polyneuropathy.

If nerve toxins such as alcohol, heavy metals or medication damage the nerves, this is known as “toxic polyneuropathy”.

Polyneuropathy: examinations and diagnosis

If you notice any symptoms of polyneuropathy, you should consult a doctor immediately. If the nerve damage is detected early and its cause treated, this will have a positive effect on the course of the polyneuropathy.

Doctor-patient consultation

Your attending physician will ask you the following or similar questions during the initial consultation:

How long has the nerve pain been present?
When did the sensory disturbances begin?
Do the symptoms occur at the same time?
Do you suffer from any previous illnesses?
What medication did you last take?
Have you come into contact with toxic substances?
Have other family members experienced similar symptoms?
Have the tingling, discomfort or pain worsened recently?

Information on drug and alcohol consumption is also important for clarifying polyneuropathy. You should therefore answer your doctors’ questions openly and honestly. This is the only way they can identify the correct cause of the nerve disorders.

Examinations and tests

Following the consultation, the doctor will examine you physically. For example, they will test your reflexes (such as the Achilles tendon reflex, which is the first to weaken). He will also check whether your pupils react correctly to incoming light.

This is followed by further examinations. Some of these are carried out on every patient, others only in certain cases:

Electroneurography (ENG) measures the nerve conduction velocity. To do this, the doctor applies a small electronic impulse to at least two different points on a nerve. He then measures the time it takes for the corresponding muscle to react (contract). In polyneuropathy, this nerve conduction velocity is usually reduced.

During the quantitative sensory examination, the doctor checks how a nerve reacts to certain stimuli such as pressure or temperature. This makes it possible to determine whether the sensitivity of the nerve is impaired – as in the case of polyneuropathy. This is a good way of detecting nerve damage. However, the examination is very time-consuming. In addition, the patient has to concentrate well and cooperate. This is why the method is not routinely used to diagnose polyneuropathy.

Electrocardiography (ECG) can provide information on whether the autonomic nerve fibers of the heart are damaged.

Some examples of such laboratory tests for polyneuropathy are:

Elevated inflammation levels (such as CRP, white blood cells, etc.) may indicate an inflammatory cause of nerve damage.
An oral glucose tolerance test (oGTT) shows how well the body can process sugar. Abnormal test results can indicate undetected diabetes (or a preliminary stage of diabetes). The fasting blood sugar is also very informative in this respect.
If diabetes is known, the HbA1c value (“long-term blood sugar”) is particularly important: it shows how well the diabetes has been controlled in recent months.
If the liver or kidney values are outside the norm, the polyneuropathy may be caused by liver or kidney disease. Liver damage can also be caused by alcohol abuse.
If there is a suspicion that a certain infectious disease is causing the polyneuropathy, special blood tests are useful. For example, suspected Lyme disease can be clarified by testing the patient’s blood for antibodies against the bacteria that cause it (Borrelia).

The same applies if the patient has certain deformities of the foot (claw toes, hollow foot) or other skeletal deformities (such as scoliosis). These are typical of hereditary polyneuropathy. The doctor can then have the patient’s genetic material examined for corresponding changes (mutations).

What helps against polyneuropathy?

The treatment of polyneuropathy is one of the core competencies of neurological specialists. Effective polyneuropathy therapy involves eliminating or treating the cause of the disease, if possible.

Causative therapy

Some examples of the causal treatment of polyneuropathy are

Alcoholics should undergo withdrawal. Diabetes patients must have their blood sugar correctly adjusted. If a vitamin B12 deficiency has been detected, the patient should eat a more balanced diet and compensate for the deficiency with a vitamin supplement.

If toxins or medication are the cause of polyneuropathy, they should be avoided as far as possible. A healthy amount of exercise can also help: Cycling or swimming is good for polyneuropathy as it improves personal fitness.

However, treatment with rituximab – an artificially produced antibody used in cancer immunotherapy and autoimmune diseases – has a good chance of success.

Which medications help with polyneuopathy?

In many polyneuropathy patients, the nerve damage causes burning pain. This can be alleviated with symptomatic therapy. The doctor often recommends painkillers such as ASA (acetylsalicylic acid) or paracetamol. He will select an individually suitable dosage for pain therapy for each patient.

On the other hand, opioids can be addictive. Their use must therefore be carefully monitored by a doctor.

In the case of very persistent polyneuropathy pain, it may be advisable for the patient to be treated by a pain therapist. They specialize in the treatment of chronic pain.

Antispasmodics, such as gabapentin or pregabalin, can also help with nerve pain. They ensure that the nerve cells are less excitable. This reduces the nerve pain.

Mood-lifting agents (antidepressants) such as amitriptyline are often used as part of pain therapy. They inhibit the transmission of pain signals in the spinal cord. Although this does not relieve the patient’s pain, it does make it more bearable.

As with anticonvulsants, it is also recommended to “creep in” to treatment with antidepressants (low dose at first, then gradually increase the dose). This reduces the risk of side effects such as a drop in blood pressure, cardiac arrhythmia or problems urinating.

If necessary, the patient can send gentle electrical impulses to the skin area via the electrode at the touch of a button. This can dampen the pain. It is not clear how this is possible. However, there are various hypotheses. For example, some experts suspect that the electrical impulses could release the body’s own pain-relieving messenger substances (endorphins).

The effectiveness of TENS for nerve pain has not yet been scientifically proven.

Physical therapy

Among other things, these procedures can increase blood circulation and strengthen weakened muscles. Physical therapy also helps polyneuropathy patients to remain mobile despite pain and other limiting symptoms.

Further therapeutic measures

Depending on the type and extent of the symptoms, other therapeutic measures may also be considered. Here are a few examples: In the case of frequent calf cramps, polyneuropathy patients can try taking a magnesium supplement.

If patients are plagued by feelings of fullness, nausea and/or vomiting due to polyneuropathy, it is advisable to change their eating habits: it is better to eat several small meals spread throughout the day than a few large meals.

In addition, nausea and vomiting can be alleviated with prescription medication (metoclopramide or domperidone).

Patients with constipation should drink plenty of fluids, eat a high-fiber diet and exercise regularly. For acute diarrhea caused by polyneuropathy, the doctor may prescribe a medication (such as loperamide).

Support stockings can also help: They prevent the blood from sinking into the legs when standing up and thus triggering the circulatory problems. Regular muscle training is also useful. If necessary, the doctor can also prescribe medication to treat low blood pressure.

If polyneuropathies cause bladder weakness, patients should go to the toilet regularly (every three hours, for example) – even if there is no urge to urinate. This prevents too much residual urine from collecting in the bladder. This encourages a bladder infection.

If this is not possible or the impotence persists afterwards, affected men can help themselves with a vacuum pump. The doctor may also be able to prescribe a sexual enhancer (sildenafil etc.).