Polyneuropathy

Generality

Polyneuropathy is a form of peripheral neuropathy, in which damaged or malfunctioning peripheral nerves are more than one.

A polyneuropathy can be: sensitive, if the peripheral nerves involved are sensitive nerves; motor, if the nerves involved are motor nerves; finally, mixed, if the peripheral nerves involved are nerves with both a sensory and a motor function.

Polyneuropathies may be acute conditions, or chronic conditions. Among the main causes of acute polyneuropathy, infectious diseases such as diphtheria and autoimmune diseases such as Guillain-Barré syndrome deserve a mention; Diabetes mellitus is one of the typical causes of chronic polyneuropathy.

The symptoms vary depending on whether the polyneuropathy is sensitive, chronic or mixed.

Accurate diagnosis of polyneuropathy requires numerous examinations and tests.

Treatment is based mainly on symptomatic therapy and causal therapy.

Short review of what a nerve is

To fully understand what a nerve is, it is necessary to start from the concept of neuron .

Neurons represent the functional units of the nervous system . Their task is to generate, exchange and transmit all those (nervous) signals that allow muscle movement, sensory perceptions, reflex responses and so on.

Typically, one neuron consists of three parts:

The so-called body, where the cell nucleus resides.
Dendrites, which are equivalent to receiving antennae for nerve signals from other neurons or receptors located in the periphery.
Axons, which are cellular extensions having the function of spreading the nervous signal. The axon covered with myelin (myelin sheath) is also called nerve fiber.

A bundle of axons forms a nerve .

Nerves can carry information in three ways:

From the central nervous system (CNS) to the periphery . The nerves with this property are called efferent. The efferent nerves control the movement of the muscles, so I am in charge of the motor sphere.
From the periphery to the CNS . Nerves with this capacity are called afferent. The afferent nerves signal to the CNS what they detected in the periphery, therefore they cover a sensitive (or sensory) function.
From the SNC to the periphery and vice versa . Nerves with this double capacity are called mixed. Mixed nerves have a dual function: motor and sensory.

What is polyneuropathy?

Polyneuropathy is a form of peripheral neuropathy, characterized by the simultaneous damage or malfunction of multiple peripheral nerves .

Peripheral nerves are the nerves of the peripheral nervous system .

PERIPHERAL NERVOUS SYSTEM

The peripheral nervous system ( PNS ): is the "arm" of the central nervous system ( CNS ). In fact, his job consists in transmitting to the CNS all the informative data captured inside and outside the organism and in spreading all processing with origin in the CNS towards the periphery.

Without the SNP, the central nervous system could not function properly.

SENSITIVE POLINEUROPATHY

Physicians define peripheral polyneuropathy as sensitive, characterized by the simultaneous damage or malfunction of several sensitive nerves.

MOTORY POLINEUROPATHY

The definition of motor polyneuropathy refers to peripheral neuropathy, characterized by the simultaneous damage or malfunction of several motor nerves.

MIXED POLINEUROPATHY

A polyneuropathy is mixed when the simultaneous damage or malfunction of several peripheral nerves affects both sensitive nerve fibers and motor nerve fibers.

Types

Depending on the rapidity of onset of symptoms and their severity, a polyneuropathy can be defined as acute or chronic.

A polyneuropathy is acute when the symptoms that characterize it appear quickly and are very severe.

A polyneuropathy is chronic when the clinical manifestations that characterize it appear gradually and possess a moderate intensity.

Causes

Physicians distinguish the causes of polyneuropathy in two categories: the causes of acute polyneuropathy and the causes of chronic polyneuropathy.

CAUSES OF ACUTE POLINEUROAPATIA

The causes of acute polyneuropathy include:

Some infectious diseases, including Lyme disease, diphtheria, botulism, shingles and AIDS . These are diseases whose origin is bacteria or viruses, capable of invading and destroying nerve cells.
Some autoimmune diseases, including Guillain-Barré syndrome, rheumatoid arthritis, systemic lupus erythematosus, Sjögren's syndrome and chronic inflammatory demyelinating polyneuropathy . Those who suffer from an autoimmune disease have an immune system that attacks healthy tissues and organs through the cells that make it up.
Taking certain medications . Among the medicines incriminated there are chemotherapy for the treatment of cancer (vinblastine and vincristine), some sedatives (barbital and esobarbital), some antibiotics (sulfonamide and nitrofurantoin) and anticonvulsants for the treatment of epilepsy (phenytoin).
Obviously, we are talking about long-term hiring.
Tumors such as lymphoma or multiple myeloma . A lymphoma is a malignant tumor of the glandular apparatus that constitutes the lymphatic system (lymph nodes). Multiple myeloma is a malignant tumor that affects some cells of the immune system; the latter, in fact, begins to produce an abnormal protein that causes kidney problems and damages other organs and body tissues.
Exposure to toxic substances, such as organophosphorus insecticides, tricresile phosphate or thallium .
A physical trauma that causes damage to peripheral nerves . The classic physical traumas that can cause damage to peripheral nerves are those following road accidents, falls (for example from a horse) or bone fractures.

CAUSES OF CHRONIC POLINEUROPATHY

The causes of chronic polyneuropathy include:

Diabetes mellitus. Diabetes mellitus is a metabolic disease caused by a defect in the secretion / action of insulin, a hormone essential for the passage of glucose from the blood to the cells.
Following failure of insulin secretion or malfunction, blood glucose levels (blood glucose) increase and a very dangerous condition for the body, known as hyperglycemia, is established.
According to the latest studies, in the presence of diabetes mellitus, hyperglycemia is the cause of polyneuropathy. In fact, high blood glucose levels would damage the blood vessels supplying peripheral nerves with oxygen and nutrients.
Without oxygen and nutrients, any nerve, tissue or organ in the body undergoes a process of death, more properly referred to as necrosis.
State of serious alcoholism . Alcoholics do not adequately absorb the nutrients of ingested foods and are often subjected to episodes of diarrhea and vomiting. This results in a state of malnutrition, which also affects the vitamins essential for the good health of the peripheral nervous system. These vitamins are B12, B1, B6, niacin and E.
Vitamin deficiencies due to causes other than alcoholism . The exclusion from the diet of the aforementioned vitamins (B12, B1 etc.), by choice or lack of availability, has the same effects, on peripheral nerves, of alcoholism.
State of hypothyroidism . A poorly active thyroid produces insufficient amount of thyroid hormones for the body's needs, including peripheral nerves.
Chronic kidney diseases . The malfunctioning of the kidneys involves an accumulation of toxic substances in the body, which also damage peripheral nerves.
Exposure to toxic substances, such as heavy metals or mercury .
Malignant tumor forms, such as lung cancer .
Excessive intake of vitamin B6 . This is a rare but possible circumstance.

Symptoms, signs and complications

The symptoms of a polyneuropathy depend on the type of damaged or malfunctioning nerves.

As a result, disorders induced by sensory polyneuropathy will be different from disorders caused by motor polyneuropathy or mixed polyneuropathy .

TYPICAL SYMPTOMS OF A SENSITIVE POLINEUOROPATHY

Episodes of sensory polyneuropathy can produce symptoms in the upper and / or lower limbs.

The typical clinical manifestations of a sensitive polyneuropathy include:

Tingling and tingling, in correspondence of the anatomical zones innervated by damaged peripheral nerves.
Sense of numbness and reduced ability to feel pain and temperature changes. Hands and feet are the most sensitive anatomical portions of these disorders.
Burning pain and similar to dense, in correspondence of the anatomical zones innervated by damaged peripheral nerves.
Allodynia, or pain caused by a stimulus that, under normal conditions, would be completely harmless and without consequences.
Loss of balance and coordination skills .

The painful sensation that characterizes sensitive polyneuropathy is a form of neuropathic pain . To be even more precise, it is called peripheral neuropathic pain .

Neuropathic pain is a different feeling from that experienced after a physical insult; in fact, it originates directly in the structures constituting the nervous system (nerves, in the case of SNP, and brain and spinal cord, in the case of the CNS).

TYPICAL SYMPTOMS OF A MOTOR POLYUROPATHY

The typical symptoms and signs of a motor polyneuropathy are:

Spasms and muscle cramps.
Muscular weakness and / or paralysis of a series of muscles.
Reduction of muscle mass due to forced use.
Falling foot. It is a particular condition characterized by the inability to hold up the front of the foot; this leads to considerable problems with walking.
Inability to hold objects.

TYPICAL SYMPTOMS OF A MIXED POLINEUROPATHY

Episodes of mixed polyneuropathy include the typical symptoms of sensory polyneuropathy and the typical symptoms of motor polyneuropathy.

WHEN TO REFER TO THE DOCTOR?

Normally, the identification of a polyneuropathy first occurs and the greater the possibility of limiting the consequences deriving from the aforementioned condition.

Therefore, an individual at risk of polyneuropathy should pay close attention to disorders such as: tingling, numbness, loss of sensitivity, lack of balance, weakness and muscle weakness, etc.

COMPLICATIONS

A polyneuropathy can have numerous complications. The latter depend, first of all, on the factors that caused the deterioration or malfunction of the peripheral nerves.

For brevity, the following are the two main and probably most common complications of polyneuropathy episodes:

Diabetic foot . It is one of the most feared consequences of diabetes mellitus.
Gangrena . Gangrene is defined as the massive putrefaction of one or more body tissues.

Diagnosis

To diagnose polyneuropathy, doctors must resort to different assessments and tests.

In general, the diagnostic procedure begins with an accurate physical examination and a careful medical history . Then, depending on which indications come from the aforementioned assessments, it may continue with: a blood test, a neurological evaluation, diagnostic imaging tests (CT and MRI), an electromyography and / or a biopsy of one or more nerves.

A precise and meticulous diagnostic procedure makes it possible to establish the presence or absence of polyneuropathy, but also the characteristics of the condition in progress (motor polyneuropathy, sensitive polyneuropathy, etc.) and the causes that triggered the latter.

Knowledge of the triggering factor allows the most appropriate therapy planning.

BLOOD ANALYSIS

The analyzes on a blood sample are useful, because they allow to understand if the patient suffers from diabetes, some vitamin deficiency or a thyroid dysfunction.

NEUROLOGICAL EVALUATION

During a neurological evaluation, the doctor analyzes the tendon reflexes and tests for the presence or absence of neuromuscular and coordinative disorders.

TAC and NMR

CT and nuclear magnetic resonance ( NMR ) are very useful and provide discrete information, for example when a tumor or physical trauma to peripheral nerves is suspected.

ELECTROMYOGRAPHY

Electromyography involves the study of the conduction of nerve signals along the symptom manifesting area and, subsequently, the evaluation of the electrical activity of the muscle or muscles, always located in the symptomatic area.

For more information on electromyography, we recommend reading the article here.

BIOPSIA OF ONE OR MORE NERVES

A nerve biopsy consists in the collection and subsequent laboratory analysis of some cells of a nerve considered to be responsible for the ongoing symptoms.

It can be useful to trace the causes of nerve damage.

Therapy

When they talk about the treatment of polyneuropathy, doctors generally refer to treatments for improving the symptomatology ( symptomatic therapy ) and to treating the triggering causes ( causal therapy ).

In fact, it is necessary to specify some aspects:

In most cases, polyneuropathy is a condition from which it is impossible to heal.
The only therapeutic remedy, expected in these situations, is to try to alleviate the most serious symptoms, in the hope of giving relief to the patient.
Regardless of whether polyneuropathy can be cured definitively or only improve from the point of view of symptoms, it is essential to act on the triggering causes.
For example, in the case of diabetes, the only way to delay or avoid the deterioration of peripheral nerve damage is to treat the disease with insulin or hypoglycemic administrations, keeping blood pressure under control, regulating body weight, etc.
Using another example, in the case of drug-induced polyneuropathies, the main therapeutic remedy (sometimes also resolutive) is to stop taking the drug responsible for the deterioration of peripheral nerves.
Currently, there is no cure or remedy to regenerate damaged neurons in the presence of a polyneuropathy.

NEUROPATHIC PAIN TREATMENT

Very often, neuropathic pain requires drugs with an anti-pain action other than those used in the presence of pain caused by trauma. Thus, paracetamol or ibuprofen are usually ineffective.

The medicines used for neuropathic pain include:

Antiepileptics, such as gabapentin and pregabalin.
Antidepressants, such as amitriptyline, doxepin, nortriptyline, duloxetine and venlafaxine.
Opioid-type painkillers, such as tramadol.
Capsaicin in cream.

For doctors, the main problem when prescribing these drugs is the indication of the most appropriate dose. Often, we proceed by trial and error, as each patient responds differently, so it represents a case in itself.