Verified on 06/21/2022 by PasseportSanté
Polyneuropathies are diseases of the peripheral nervous system. Motor skills, sensitivity and less often mobility are affected.
The most common cause of polyneuropathy is diabetes. Elimination of the triggering factor and pain management allow for a better quality of life. We take stock.
What is polyneuropathy?
Polyneuropathies, also called polyneuritis, refer to disorders of the peripheral nerves (that is, the nerves that lie between the spinal cord and the muscles of the limbs). In the majority of cases, polyneuropathies are chronic and develop slowly and progressively. Rarely are they acute, i.e. they occurred suddenly.
The causes of nerve damage are very diverse:
- nutritional deficiencies;
- diabetes ;
- autoimmune diseases.
Polyneuropathy of the lower extremities
Sensitivity and strength are impaired. Motor skills are less often reduced. Typically, the disease first affects the extremities and limbs (feet, hands, arms and legs) and sometimes the trunk.
Most often, the first signs leading to a consultation are tingling or even pain in the form of electric shocks. A decrease in muscle volume (amyotrophy) can be added to the clinical picture.
Diagnosis requires an electromyogram, nerve conduction studies, and blood and urine tests. Physical therapy, occupational therapy, medication, and other interventions may be necessary to relieve pain and regain a better quality of life.
What causes polyneuropathy?
The symptoms of polyneuropathies are explained by lesions in different places. A variety of diseases, infections or poisoning can trigger polyneuropathy.
Damage to peripheral nerves
Polyneuropathy can affect one or more peripheral nerves in the body (we also speak of peripheral polyneuropathy).
As a reminder, the peripheral nerves connect the body’s organs (including muscles) to the central nervous system (spinal cord, brain, etc.). It can act on all nerves:
- motor nerves (motor polyneuropathy);
- sensory nerves (sensory polyneuropathy);
- cranial nerves (facial polyneuropathy);
- autonomic nerves (which control involuntary functions such as blood pressure, breathing, heart rate), etc.
Polyneuropathy can result from lesions at various sites. The lesions may be in the myelin sheaths around the nerves (demyelinating polyneuropathy), as seen in Guillain-Barré syndrome.
Sometimes the lesion affects blood vessels that supply nerves, as can occur with vasculitis. Finally, sometimes the axon of the nerves (axonal polyneuropathy) is damaged, as seen in diabetes or kidney failure.
Many risk factors for polyneuropathy
Polyneuropathy can have many causes:
- Diabetes: This is the most common form of chronic polyneuropathy. It usually stems from poor blood sugar control in diabetics. We are talking about diabetic polyneuropathy;
- An infection related to a toxin produced by a bacterium (such as in diphtheria);
- An autoimmune reaction, as in Guillain-Barré syndrome;
- Poisoning with certain toxins or metals (triorthocresyl phosphate (TOCP), thallium, arsenic, mercury, etc.);
- Excessive alcohol consumption (alcoholic polyneuropathy);
- Certain infections (hepatitis C, HIV, Lyme disease, shingles, etc.);
- Certain hereditary neuropathies (such as Charcot-Marie-Tooth disease);
- Certain autoimmune diseases (such as chronic inflammatory demyelinating polyneuropathy, vasculitis, or systemic lupus erythematosus);
- nutritional deficiencies including vitamin B12 (deficiency of vitamin B12 also causes degeneration of the spinal cord and often pernicious anemia) or thiamine (vitamin B1);
- alcoholism (especially if it leads to malnutrition);
- kidney failure;
- cancer (such as multiple myeloma, which damages nerves by directly penetrating or putting pressure on them);
- Taking certain medications (anticonvulsant phenytoin, certain antibiotics (chloramphenicol, nitrofurantoin, sulfonamides, and certain chemotherapy drugs such as vinblastine and vincristine);
- Excessive consumption of vitamin B6 or pyridoxine (rare cause).
What are the symptoms of polyneuropathy?
The onset of symptoms in polyneuropathy can be sudden or, on the contrary, slow and progressive.
Usually the limbs and extremities are the first areas to be affected. One speaks of distal polyneuropathy in particular when the disease affects the foot nerves. It is the most common complication of diabetes. The clinical manifestations that are usually found are:
- muscle weakness;
- loss of sensitivity;
- pain with burning sensation or electric shock;
- loss of sense of vibration and position;
- a loss of thermal sensitivity (the subject no longer feels hot and cold);
- a loss of pain sensation common in diabetic polyneuropathy. It leads to injuries, burns, open wounds caused by sustained pressure and other trauma. It is also the cause of many skin diseases that are complicated without the patient noticing it. The loss of pain sensitivity can also lead to joint damage called neurogenic arthropathy (Charcot joints);
- walking and standing instability;
- an inability to determine the position of the arms and legs in space;
Eventually, the muscles will no longer be stressed enough, leading to:
- muscle wasting (amyotrophy);
- muscle stiffness;
- muscle contractions.
Polyneuropathy can affect the nerves of the autonomic nervous system, which controls involuntary bodily functions (such as blood pressure, breathing, heart rate, digestion, salivation, and urination).
Characteristic symptoms are:
- sexual dysfunctions;
- dry mouth and halitosis (bad breath);
- Fluctuations in blood pressure (particularly responsible for orthostatic hypotension);
- sallow, dry skin from reduced sweating;
- loss of sphincter or bladder control leading to fecal or urinary incontinence;
Individuals suffering from hereditary polyneuropathy often have physical deformities such as:
- hammer toes;
- hollow feet;
- a hunched back (scoliosis);
What are the treatments for polyneuropathy?
Treatment of polyneuropathy begins with the underlying cause such as diabetes, an autoimmune disease, exposure to toxic substances or medications.
Management also consists of reducing pain and optimizing patient mobility and quality of life through medication, physical therapy and occupational therapy.
Treating the cause
The specific treatment for polyneuropathy depends on the cause:
The patient must take care of his lifestyle and take the prescribed treatments (hypoglycemia and other oral antidiabetics, insulin, etc.). Blood sugar should be controlled and stabilized to reduce the risk of polyneuropathy worsening.
Multiple myeloma, liver or kidney failure
Treating these disorders can result in a slow recovery.
Surgical removal of the tumor, chemotherapy/radiation therapy can reduce neuropathy.
The patient must ensure a healthy lifestyle and sufficient iodine intake. Thyroid hormone is administered.
Treatments may include corticosteroids, immunosuppressants, plasmapheresis, and intravenous immunoglobulin.
For medicinal or toxic causes
The causative drug should be stopped as soon as possible, or exposure to the toxin should be avoided. Antidotes are available for some drugs and toxins, which can reverse some toxic effects.
To relieve the pain, the doctor may prescribe:
- analgesics (paracetamol);
- opiates (codeine, morphine);
- Anti-inflammatories (NSAIDs, corticosteroids).
Certain medications that aren’t typically considered pain relievers can relieve pain from nerve damage.
These include the antidepressant amitriptyline, the anticonvulsants gabapentin and pregabalin, and mexiletine (used to treat abnormal heart rhythms).
Lidocaine (an anesthetic applied as a lotion, ointment, or skin patch) may also be prescribed.
Maintaining mobility and quality of life
Physical therapy sometimes reduces muscle stiffness and can prevent muscles from shortening and stiffening. A consultation with a physical therapist and/or an occupational therapist may be recommended to improve the patient’s mobility and quality of life.
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