Neuropathy is characterized by the condition of one or more types of motor and sensory nerves that control the feet and hands, as well as the nerves of the autonomic nervous system that control organs. Symptoms depend on the type of nerve affected.

Neuropathy, what is it?

Definition of neuropathy

Neuropathy is a term used to describe a problem with nerves, usually the “peripheral nerves” as opposed to the “central nervous system” which includes the brain and spinal cord. We also speak of peripheral neuropathy.

Neuropathy is caused by a number of conditions. Neuropathy can also exist without the cause being diagnosed. It is then qualified as “idiopathic neuropathy”.

The term neuropathy covers a large area and many nerves. The resulting symptoms depend on the type of nerve that is affected:

• Affected sensory nerves (the nerves that control sensation) cause tingling, burning, throbbing pain, “electric shocks”, numbness, pain. itching or weaknesses in the feet and hands. We speak of sensory neuropathy.
• Affected motor nerves (the nerves that keep you moving) cause weakness in your feet and hands. We are talking about motor neuropathy.
• Affected autonomic nerves (the nerves that control organs in the body, eg, the gut and bladder) cause changes in heart rate and blood pressure or sweating. We talk about autonomic neuropathy.

Neuropathy has several causes, which is why all three types of nerve can be affected at the same time: this is called polyneuropathy, as opposed to mononeuropathy which is characterized by the affection of a single nerve.

Exemples by mononeuropathies

• La paralysis ulnar (or ulnar) nerve following an injury to the elbow.
• Carpal tunnel syndrome, caused by compression of the median nerve.
• Paralysis of the peroneal nerves, caused by compression of a nerve in the leg.
• Paralysis of the radial nerve, the nerve that innervates the muscles of the elbow, wrist and fingers.
• Bell’s palsy, which affects a nerve that innervates the muscles of the face.

Causes of neuropathy

There are over a hundred causes of neuropathic pain. About 30% of neuropathies are “idiopathic” or of an unknown cause.

Many diseases can lead to peripheral neuropathy:

• Diabetes, which is the most common cause of chronic peripheral neuropathy. We are talking about diabetic neuropathy. High blood sugar levels cause damage to the walls of small blood vessels that deliver oxygen and nutrients to the nerves that supply the ends of the hands and feet and major organs in the body (eyes, kidneys, heart) . As a result, the skin becomes damaged and the loss of sensitivity makes the skin of the feet more vulnerable.
• Deficiencies in vitamin B12 or folic acid can cause nerve damage and peripheral neuropathy.
• Medicines – such as some medicines used in chemotherapy or to treat HIV can cause damage to peripheral nerves.
• Certain insecticides and solvents.
• Lymphoma and multiple myeloma cancers.
• Alcohol abuse.
• Chronic kidney disease – if the kidneys are not functioning normally, an imbalance of salts can cause peripheral neuropathy.
• Chronic liver disease.
• Injuries, such as a broken bone that can put pressure on a nerve.
• Certain infections such as shingles, HIV infection and Lyme disease.
• Le Guillain-Barré syndrome is the name given to a specific type of peripheral neuropathy triggered by infection.
• Connective tissue diseases: rheumatoid arthritis, Sjögren syndrome and systemic lupus erythematosus.
• Certain inflammatory conditions including sarcoïdose and celiac disease.
• Hereditary diseases such as Charcot-Marie-Tooth syndrome and Friedreich’s ataxia.

Diagnosis of neuropathy

The doctor asks the patient about:

• its symptoms.
• His general health.
• His family history of neuropathy.
• His medications taken now or recently.
• Its possible exposure to toxins.
• His possible excessive alcohol consumption.
• His sexual behavior.

The doctor will:

• carefully examine the patient’s skin.
• Check the sensation of a vibration using a tuning fork.
• Examine tendon reflexes.

Blood tests

They can highlight the presence of diabetes, thyroid dysfunction or vitamin deficiency.

Nerve conduction studies

Nerve conduction studies check how fast nerves send their messages to muscles. Special electrodes are placed on the skin at the level of the tested nerve and emit very small electrical impulses that stimulate the nerve. Other electrodes record the electrical activity of the nerve. A reduced speed of the nerve impulse indicates the presence of peripheral neuropathy.

Electromyography

Electromyography is used to diagnose muscle weakness caused by neuropathy. This test examines the electrical activity of muscles. A very fine needle connected to an electrode is inserted into a muscle. This is connected to a recording machine called an oscilloscope. Abnormal electrical activity reflects the presence of peripheral neuropathy.

Nerve biopsy

A small part of a nerve is removed so that it can be examined under a microscope.

Skin biopsy

It is a technique to examine the peripheral nerves. It can be used to check for early peripheral neuropathy and to monitor neuropathy progression and response to treatment. Among other things, the density of nerve fibers in the skin area is measured. In peripheral neuropathy, the density of peripheral nerves is reduced.

Symptoms of neuropathy

Neuropathy of the sensory system

• Tingling and numbness in the hands and feet (diabetic neuropathy)
• Hypersensitivity.
• Increased pain or loss of ability to feel pain.
• Loss of ability to detect changes in heat and cold.
• Loss of coordination and proprioception.
• Burning-type pain, the intensity of which may increase at night.
• Changes to the skin, hair or nails.
• Foot and leg ulcers, infection, even gangrene.

Neuropathy of the motor system

• Muscle weakness – causing instability and difficulty making small movements such as buttoning the shirt (especially in diabetic neuropathy).
• Muscle tremor and cramps.
• Muscular paralysis.

Neuropathy of the autonomic system

• Dizziness and fainting (due to sudden changes in blood pressure).
• Reduction of perspiration.
• Inability to tolerate heat.
• Loss of control over bladder function resulting in incontinence or urine retention.
• Swelling, constipation or diarrhea (especially in diabetic neuropathy).
• Difficulty achieving or maintaining an erection (especially in diabetic neuropathy).

How to prevent neuropathy?

The prevention of neuropathy in people with diabetes is based in particular on good food hygiene and strict monitoring of glucose. Studies have shown that glyceric control by injection reduces the risk of developing diabetic neuropathy.