Peripheral Neuropathy – Causes, Signs and symptoms

Peripheral Neuropathy

Also called: Distal Sensory Neuropathy, Somatic Neuropathy, Sensory Neuropathy, Somatic Peripheral Neuropathy, Diffuse Neuropathy

Summary

Peripheral neuropathy is a condition in which damage to nerves prevents the peripheral nervous system (PNS) from effectively communicating messages between the brain and rest of the body. It may develop from birth or later in life as the result of an inherited condition. It may also occur due to disease, injury or other factors. In practical usage, the term “peripheral neuropathy” is used interchangeably with the term “neuropathy,” which indicates any type of nerve damage.

Many types of peripheral neuropathy have been identified. Each has its own symptoms and prognosis, which are dependent on the type of nerves that are affected. Some types of peripheral neuropathy occur suddenly and progress rapidly, while others develop more slowly.

Examples of various types of peripheral neuropathy include:

  • Diabetic neuropathy. Neuropathy that occurs as a result of damaged caused by high levels of blood sugar.
  • Guillain-Barré syndrome. Condition in which the body’s immune system attacks the nerves of the PNS.
  • Autonomic neuropathy. Autonomic neuropathy is a collection of symptoms that occurs as a result of damage to the nerves of the autonomic nervous system (ANS).
  • Charcot-Marie-Tooth disease. Group of disorders resulting in flaws in the genes that manufacture neurons or the myelin sheath.
  • Trigeminal neuralgia. Also known as tic douloureux, it involves damage to a large nerve of the head and face, resulting in shooting pain.

When the peripheral nerves are damaged, it causes unusual irritation to occur throughout the body. Each peripheral nerve in the body has a specialized function that involves a specific part of the body, and symptoms that appear are associated with a particular nerve that has been damaged.

Diagnosing peripheral neuropathy can be challenging because symptoms may vary from person to person. In addition, it can be very difficult to determine exactly what type of neuropathy a patient has. Various tests may be performed to pinpoint the cause of a patient’s peripheral neuropathy.

Acquired neuropathies (i.e., those that are not caused by an inherited condition) are usually best treated by addressing the underlying condition causing the nerve damage. There is no treatment for most inherited neuropathies. Medications, surgery and various types of therapy may be helpful in relieving symptoms (e.g., pain or weakness) that are associated with most types of neuropathy. Maintaining good health is often the best defense against the damage of neuropathies. This includes maintaining a healthy weight, engaging in regular exercise and eating a well-balanced diet. People can also reduce their risk of developing peripheral neuropathy by taking measures to prevent accidents that may cause nerve damage.

About peripheral neuropathy

Peripheral neuropathy is nerve damage that affects the peripheral nervous system (PNS). It can cause symptoms such as pain, loss of sensation or inability to control muscles. In practical usage, the term “peripheral neuropathy” is used interchangeably with the term “neuropathy,” which indicates any type of nerve damage. Peripheral neuropathy is very common. As many as 20 million Americans have neuropathy, according to The Neuropathy Association.

The nervous system controls virtually all activity in the body, including breathing, thinking and movement. It is divided into two parts. The brain and spinal cord make up the central nervous system (CNS), which processes information from the senses and responds with commands to the muscles and glands in the body. The second part of the nervous system is called the peripheral nervous system. The PNS includes the autonomic nervous system (ANS), which is not under a person’s conscious control.

The nerves of the PNS are divided into three categories:

  • Autonomic nerves. Regulates activities in the body that are not under a person’s conscious control. Examples include breathing, digesting food, and functions of the heart and glands.

  • Motor nerves. Transmits information from the brain and spinal cord to the rest of the body. These nerves control movements of all muscles under conscious control. This includes grasping things, talking and walking.

  • Sensory nerves. Transmits information about sensory experiences such as the sensation of feeling someone’s touch or the pain that results from a cut.

The nerves of the PNS relay information from the brain and spinal cord (the CNS) to various points in the body. In addition, the PNS relays information from the body back to the CNS. For example, the PNS may send sensory information back to the CNS indicating that a person’s feet are cold, which would then trigger a response from the CNS to take steps to warm the feet. Damage to PNS nerves can short-circuit these messages, preventing them from being sent at all or causing them to be sent at the wrong time or too slowly.

Peripheral neuropathy may occur as a result of damage to a single nerve (mononeuropathy) but is more likely to include multiple nerves (polyneuropathy). In some cases, two or more isolated nerves in separate areas of the body may be affected (mononeuritis multiplex).

Peripheral neuropathy causes various levels of discomfort depending on which nerves are affected and the extent of damage to the nerves. The most common symptoms of peripheral neuropathy are weakness, numbness, tingling and pain, which can be mild to severe. Because motor and sensory axons run in the same nerve bundle, damage to a specific nerve bundle typically affects both motor and sensory functions.

Neuropathies are rarely life-threatening unless other diseases are complicating factors.

Types and differences of peripheral neuropathy

More than 100 types of peripheral neuropathy have been identified. Each has its own symptoms and prognosis, which are dependent on the type of nerves affected – autonomic, motor or sensory.

Peripheral neuropathies are generally classified as being acute or chronic. Acute neuropathies involve symptoms that appear suddenly, that progress rapidly and that subside slowly as the nerves begin to heal. In contrast, chronic neuropathies feature symptoms that emerge subtly and unfold gradually over time. People with chronic neuropathies may see their symptoms progress, or may experience discomfort that eventually plateaus. In other cases, symptoms may go into remission, only to re-emerge in the future.

Types of peripheral neuropathies include:

  • Diabetic neuropathy. Neuropathy that occurs as a result of damaged caused by high levels of blood sugar. Diabetes experts have identified four types of diabetic neuropathy – autonomic, focal, peripheral and proximal. However, it is important to note that many experts consider all of these neuropathies as belonging to the category of peripheral neuropathy.
  • Autonomic neuropathy. Autonomic neuropathy is a collection of symptoms that occurs as a result of damage to the nerves of the autonomic nervous system (ANS). The ANS regulates involuntary functions of the body such as heart rate, blood pressure, digestion and perspiration. Patients with autonomic neuropathy experience discomfort (e.g., bladder and bowel dysfunction, gastrointestinal problems) but the condition is rarely life-threatening.
  • Proximal neuropathy. Nerve damage that can affect the legs, thighs, hips and buttocks – usually on just one side of the body. It causes weakness and pain that usually requires treatment. People with type 2 diabetes have an increased risk of this type of neuropathy.
  • Neuropathy secondary to drugs. Damage to the nerves resulting from the toxic effect of using certain medications. Examples include heart and blood pressure medications, anticonvulsants, cholesterol drugs and others.
  • Alcoholic neuropathy. Decreased nerve function as a result of excessive alcohol consumption. Experts disagree about the cause of this form of neuropathy, but it may be a result of the toxic effect of alcohol on nerve tissue.
  • Guillain-Barré syndrome (GBS). Condition in which the body’s immune system attacks the nerves of the peripheral nervous system (PNS). Two-thirds of all patients with GBS reported having a recent bacterial or viral infection.
  • Charcot-Marie-Tooth disease. Group of hereditary disorders resulting in flaws in the genes that manufacture neurons or the myelin sheath. Symptoms include extreme weakening and wasting of muscles in the lower legs and feet, gait problems, loss of tendon reflexes, and lower-limb numbness.
  • Friedreich’s ataxia. Inherited disease that causes progressive damage to the nervous system. The first symptom may be difficulty walking. Symptoms then spread to the arms and trunk and range from muscle weakness and speech problems to heart disease.
  • Trigeminal neuralgia. Also known as tic douloureux, it involves damage to the large nerve of the head and face. Symptoms include severe pain on one side of the face that has been described as “lightning-like.”

Risk factors/causes of peripheral neuropathy

Peripheral neuropathy results from damage to the body’s peripheral nerves. As these nerves deteriorate, they are less able to communicate with the muscles, organs and tissues of the body.

Some peripheral neuropathies are inherited (e.g., Charcot-Marie-Tooth disease, Friedreich’s ataxia), while many others are acquired later in life. Inherited neuropathies may cause symptoms early in life, or may not appear until later. Inherited neuropathies that appear during infancy are more likely to be severe than those that appear in young adulthood. 

There are many sources of acquired neuropathy. Physical injury is the most common source of damage to nerves. Sources of such injuries include car accidents, falls and athletic injuries. Less severe injuries, such as herniated discs and broken bones, also can damage nerves. Physical injury can lead to crushed, compressed, stretched or severed nerves. Prolonged immobility can also pressure and damage peripheral nerves.

Many different types of systemic diseases also can cause peripheral neuropathy. Systemic diseases affect the entire body. Examples include:

  • Metabolic and endocrine disorders. These include diseases that impair the body’s ability to transform nutrients into energy, process waste products, or manufacture substances that are part of living tissue. Diabetes mellitus, a common metabolic disorder, is a leading cause of peripheral neuropathy in the United States. About one-third of all cases of peripheral neuropathy are caused by diabetes, according to The Neurological Association. Approximately half of all people with diabetes develop nerve damage, according to the National Institutes of Health (NIH).

  • Autoimmune disorders. These conditions cause a person’s immune system to attack the body’s tissues. Conditions such as lupus and rheumatoid arthritis are types of autoimmune disorders.

  • Cancers and benign tumors. These conditions can either infiltrate nerve fibers or place damaging pressure upon the fibers.

  • Kidney and liver disorders.  A majority of patients who require dialysis because of kidney failure develop polyneuropathy, according to the NIH.

  • Vitamin deficiencies. Vitamins E, B1, B6, B9 (folate), B12, and niacin are essential to healthy nerve function. A deficiency in any of these vitamins may lead to nerve damage. An excess of vitamin B6 may also lead to a peripheral neuropathy.

  • Toxins. People exposed to heavy metals (arsenic, lead, mercury, thallium), industrial drugs or environmental toxins often develop neuropathy. Certain medications (e.g., anticancer drugs, anticonvulsants, antiviral agents, antibiotics) also can cause neuropathy when used too long.

  • Alcoholism. Some experts believe that excessive alcohol consumption can lead to a condition called alcoholic neuropathy.

  • Repetitive movements. Often results in entrapment neuropathies, in which the nerves are compressed. This type of injury is more common in pregnancy, when fluid retention and weight gain constrict nerve passageways.

  • Infectious or inflammatory conditions. Viral and bacterial infections and inflammatory disorders can damage nerve tissues. Some examples include:

    • Cytomegalovirus (CMV)

    • Diphtheria

    • Epstein-Barr virus (mononucleosis)

    • Guillain-Barré syndrome
    • Herpes simplex virus

    • Shingles(Varicella-zoster virus)

    • Human immunodeficiency virus (HIV)

    • Leprosy

    • Lyme disease

  • Connective tissue disorders and chronic inflammation. Inflammation of the protective tissues around nerves can spread into the nerves themselves.  Chronic inflammation destroys connective tissue, leading to compression injuries and infections involving nerve fibers.

  • Vascular damage and blood diseases. These conditions can hamper oxygen supply, leading to damage or death of nerve tissues.  Blood vessel inflammation (vasculitis) causes vessel walls to harden, thicken and develop scar tissue. This impedes blood flow.

  • Hormonal imbalances. Underproduction of thyroid hormones slows metabolism, while overproduction of growth hormones can lead to acromegaly (abnormal enlargement of many parts of the skeleton), causing nerves to become entrapped in joints.

Despite the numerous factors and conditions that are known to cause peripheral neuropathy, in approximately one-third of peripheral neuropathy cases the cause remains unknown, according to The Neuropathy Association. Peripheral neuropathy with no known cause is sometimes referred to as being “idiopathic.” Peripheral neuropathy can occur at any age, although it is more common among older adults. People with diabetes have an especially increased risk of developing peripheral neuropathy as they age. The American Diabetes Association (ADA) estimates that, after living with diabetes for 25 years, between 60 and 70 percent of people will have some type of neuropathy. The chance of developing neuropathy increases the longer a person has diabetes.

Signs and symptoms of peripheral neuropathy

When the peripheral nerves are damaged, it may cause unusual irritation to occur throughout the body. However, the type of irritation can vary significantly from person to person. Each peripheral nerve in the body has a specialized function that involves a specific part of the body, and symptoms that appear are associated with the particular nerve that has been damaged.

Polyneuropathy is the most common type of peripheral neuropathy. It involves damage to multiple nerves. In many cases, polyneuropathy initially affects nerves most distant from the brain and spinal cord (e.g., in the arms or legs) before working its way toward the center of the body. Most symptoms affect both sides of the body.

Symptoms associated with peripheral neuropathy include:

  • A burning, prickling or tingling sensation (paresthesia)
  • Weakness
  • Numbness
  • Discomfort or pain
  • Muscle twitching or cramping
  • Sensitivity to touch
  • Dizziness
  • Incoordination or clumsiness
  • Sexual dysfunction
  • Inability to digest food easily
  • Nausea, vomiting
  • Abnormal sweating and heat intolerance
  • Blurred vision

Symptoms may be mild at first but become more severe over time. Less often, symptoms may occur suddenly and start out as severe.

Severe symptoms of peripheral neuropathy may include:

  • Severe pain
  • Fluctuations in blood pressure
  • Organ and/or gland dysfunction
  • Difficulty breathing or swallowing
  • Muscle wasting (atrophy)
  • Paralysis
  • Difficulty detecting pain and other sensations

Symptoms associated with peripheral neuropathy are rarely life-threatening. However, damage to autonomic nerves can be potentially fatal if it impairs functions such as breathing, blood pressure control or normal heartbeat.

Diagnosis methods for peripheral neuropathy

Diagnosing peripheral neuropathy can be difficult, because symptoms can vary so much from person to person. In addition, it can be very difficult to determine exactly what type of neuropathy a patient has. A physician typically will compile a thorough medical history and perform a complete physical examination of the patient. In addition, a neurological examination is often performed.

Various tests may be performed to pinpoint the cause of a patient’s peripheral neuropathy. For example, blood tests may reveal the presence of diabetes, liver or kidney dysfunction, or vitamin deficiencies. A spinal tap may be used to look for abnormal antibodies in a patient’s cerebrospinal fluid that my indicate neuropathy. Imaging tests such as computed axial tomography (CAT scan) and magnetic resonance imaging (MRI) also may be helpful.

Other tests that may be performed include:

  • Nerve conduction velocity (NCV) tests. A nerve fiber is stimulated, which generates an electrical impulse. An electrode further down the nerve’s pathway records the speed of impulse transmission. Abnormal results may indicate nerve damage.
  • Electromyography (EMG). A needle is inserted into a muscle to compare electrical activity in muscles at rest and during muscle contraction.
  • Nerve biopsy. Removes a sample of nerve tissue for analysis, most often from the lower leg.
  • Skin biopsy. Thin skin sample is obtained to examine the endings of nerve fibers.

A physician also may test a patient’s muscle strength or ability to perceive touch, temperature and pain. Underlying conditions responsible for peripheral neuropathy may be revealed through additional testing for cardiovascular disease, connective tissue disorders and malignancies.

Treatment and prevention

Acquired neuropathies (i.e., those that are not caused by inherited conditions) usually are best treated by addressing the underlying condition causing the nerve damage. In some cases, surgery may be helpful, such as when a nerve is compressed due to an entrapment injury. An examples of such a surgery is a carpal tunnel syndrome release. There is no cure for most inherited neuropathies.

If the condition itself cannot be cured, symptoms associated with peripheral neuropathy may be reduced or eliminated through various therapies. Over-the-counter analgesics can be used to treat mild neuropathies. Anticonvulsants, antidepressants and anesthetics also may be used.

Use of certain devices such as wheelchairs, hand or foot braces and splints can either help compensate for muscle weakness or alleviate nerve compression. In some cases, orthopedic shoes can help people with gait problems. Mechanical ventilation can aid the breathing of patients with severe forms of neuropathy.

As long as the nerve cell itself has not been destroyed, peripheral nerves have the ability to regenerate. This may be helped by physical therapy or occupational therapy. Physical therapy includes a mixture of exercises, massage and other treatments to maintain strength and flexibility. Occupational therapy is similar to physical therapy, but it focuses on improving patients’ fine motor skills.

Other steps that can help a person relieve symptoms associated with neuropathies include:

  • Avoiding toxin exposure
  • Limiting alcohol consumption
  • Restoring proper vitamin levels
  • Quitting smoking

Maintaining good health is often the best defense against the damage of neuropathies. This includes maintaining a healthy weight, engaging in regular exercise and eating a well-balanced diet. In addition, patients often are advised to take various measures to increase their safety, which may help prevent certain injuries that can cause peripheral neuropathy. Safety measures may include installing railings and adequate lighting and removing potentially dangerous obstacles (e.g., loose rugs). Patients are urged to avoid placing prolonged pressure on the body’s pressure points, such as elbows and knees. Pressure in these areas can result in additional nerve damage.

Questions for your doctor

Preparing questions in advance can help patients to have more meaningful discussions with healthcare professionals regarding their condition. Patients may wish to ask their doctor the following questions related to peripheral neuropathy:

  1. What are the first symptoms of peripheral neuropathy that I am likely to notice?
  2. How will you diagnose my peripheral neuropathy?
  3. What type of peripheral neuropathy do I have?
  4. Is an underlying condition the likely source of my peripheral neuropathy?
  5. Will treating this condition eliminate my peripheral neuropathy?
  6. What are my treatment options?
  7. What are the risks of these treatments?
  8. Will I require surgery?
  9. How can I reduce symptoms associated with my peripheral neuropathy?
  10. What is my long-term prognosis?
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