Neuropathy is characterized by the affection 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 controls the organs. The symptoms depend on the type of nerve affected.
Definition of neuropathy
Neuropathy is a term used to describe a problem related to the nerves, usually the “peripheral nerves” as opposed to the “central nervous system” which includes the brain and spinal cord. We also talk about peripheral neuropathy.
Neuropathy is caused by a number of conditions. Neuropathy can also exist without the cause being diagnosed. It is then called “idiopathic neuropathy”.
The term neuropathy covers a large area and many nerves. The resulting symptoms depend on the type of nerve that is affected:
- The affected sensory nerves (the nerves that control the sensation) cause tingling, burning, throbbing pains, “electric shocks”, numbness, itching, or weakness in the feet and hands. We talk about sensitive neuropathy.
- Affected motor nerves (nerves that allow movement) cause weakness in the feet and hands. We talk about motor neuropathy.
- Affected autonomic nerves (the nerves that control the body’s organs, eg the intestine and bladder) cause changes in heart rate and blood pressure or sweating. We are talking about autonomic neuropathy.
Neuropathy has several causes, which is why the three types of nerve can be affected at the same time: this is called polyneuropathy, as opposed to mononeuropathy that is characterized by the affection of a single nerve.
Examples of mononeuropathies
- The paralysis of the ulnar nerve (or ulnar) following an elbow injury.
- 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 more than a hundred causes of neuropathic pain. About 30% of neuropathies are “idiopathic” or of 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 levels of blood sugar cause damage to the walls of small blood vessels that supply oxygen and nutrients to the nerves that innervate the extremities of the hands and feet and the main organs of 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.
- Vitamin B12 or folic acid deficiencies can cause nerve damage and peripheral neuropathy.
- Medications – such as certain drugs used in chemotherapy or in the treatment of HIV can cause damage to the peripheral nerves.
- Some insecticides and solvents.
- Lymphoma and multiple myeloma type cancers.
- Alcohol abuse.
- Chronic Kidney Disease – If the kidneys are not functioning normally, an imbalance in salts can cause peripheral neuropathy.
- Chronic liver disease
- Injuries, such as a broken bone that can exert pressure on a nerve.
- Some infections such as shingles, HIV infection and Lyme disease.
- The Guillain-Barre syndrome is the name given to a specific type of peripheral neuropathy triggered by an infection.
- Connective tissue diseases: rheumatoid arthritis, Sjögren’s syndrome and systemic lupus erythematosus.
- Certain inflammatory conditions including sarcoidosis and celiac disease.
- Hereditary diseases such as Charcot-Marie-Tooth syndrome and Friedreich’s Ataxia.
Diagnosis of neuropathy
The doctor asks the patient about:
- His symptoms.
- His general health.
- His family history of neuropathy.
- His medications taken now or recently.
- His possible exposure to toxins.
- His possible excessive consumption of alcohol.
- His sexual behavior.
The doctor will:
- Carefully examine the patient’s skin.
- Check the sensation at a vibration using a tuning fork.
- Examine tendon reflexes.
They show the presence of diabetes, thyroid dysfunction or vitamin deficiency.
Nerve conduction studies
Nerve conduction studies check the speed with which the nerves send their messages to the muscles. Special electrodes are placed on the skin at the level of the nerve tested and emit very small electrical impulses that stimulate the nerve. Other electrodes record the electrical activity of the nerve. A reduced rate of nerve impulse indicates the presence of peripheral neuropathy.
Electromyography is used to diagnose muscle weakness caused by neuropathy. This test examines the electrical activity of the muscles. A very fine needle connected to an electrode is inserted into a muscle. That is connected to a recording machine called oscilloscope. Abnormal electrical activity reflects the presence of peripheral neuropathy.
Biopsy of the nerve
A small part of a nerve is removed so that it can be examined under a microscope.
Biopsy of the skin
It is a technique to examine the peripheral nerves. It can be used to look for early peripheral neuropathy and to monitor progression of neuropathy and response to treatment. Among other things, the density of the nerve fibers in the area of the skin is measured. In peripheral neuropathy, peripheral nerve density is reduced.
Symptoms of neuropathy
Neuropathy of the sensory system
- Tingling and numbness in the hands and feet (diabetic neuropathy)
- Increased pain or loss of ability to feel pain
- Loss of ability to detect changes in heat and cold.
- Loss of coordination and proprioception.
- Burn-like pain, the intensity of which can increase at night.
- Changes in the skin, hair or nails.
- Ulcers of the foot and leg, infection, even gangrene.
Neuropathy of the motor system
- Muscle weakness – causing instability and difficulty in small movements such as buttoning of the shirt (especially in diabetic neuropathy).
- Muscular tremor and cramps.
- Muscular paralysis.
Neuropathy of the autonomous 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 retention of urine.
- 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 blood glucose . Studies have shown that glyceric control by injection reduces the risk of developing diabetic neuropathy.