Understanding Peripheral Neuropathy

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Peripheral neuropathy is a disease caused by damage to the peripheral nervous system, an extensive communication network that carries information from the brain and spinal cord (that is, the central nervous system) to all other parts of the body. Peripheral nerves also send sensory information to the brain and spinal cord, such as a message that your feet are cold or that your toe is burned.

Illustration by Brianna Gilmartin, Get Drug Information

Overview

Damage to the peripheral nervous system disrupts these connections and communications. Like static on a phone line, peripheral neuropathy distorts and sometimes disrupts communication between the brain and the rest of the body. Because each peripheral nerve performs a highly specialized function in a specific part of the body, a wide range of symptoms can occur when nerve damage occurs.

Some people may experience:

  • Temporary numbness
  • Tingle
  • Stitching sensations (paresthesia)
  • Tenderness to touch or muscle weakness .

Others may have more serious symptoms, including:

  • Burning pain (especially at night)
  • Amyotrophy
  • Paralysis
  • Dysfunction of an organ or gland.

In some people, peripheral neuropathy can affect the ability to:

  • Easy to digest foods
  • Maintain a safe blood pressure level
  • Sweat well
  • Experience normal sexual function

In the most extreme cases, breathing can be difficult or organ failure can occur.

Forms

Some forms of neuropathy involve damage to a single nerve and are called mononeuropathy. More often, multiple nerves are affected, affecting all extremities, which is called polyneuropathy. Sometimes two or more separate nerves in different parts of the body are affected, which is called mononeuritis multiplex .

In acute neuropathies such as Guillain-Barré syndrome ( also known as acute inflammatory demyelinating neuropathy), symptoms appear suddenly, progress rapidly, and resolve slowly as the damaged nerves heal.

In chronic neuropathies, symptoms begin faintly and progress slowly. Some people may have periods of relief followed by a relapse. Others may reach a plateau stage, where symptoms remain unchanged for many months or years. Some chronic neuropathies get worse over time, but very few forms are fatal unless complicated by other conditions. Sometimes neuropathy is a symptom of another disorder.

In the most common forms of polyneuropathy, nerve fibers (the individual cells that make up the nerve) are further from the brain and disrupt the spinal cord. Pain and other symptoms usually appear symmetrically, for example, in both feet, followed by gradual progression in both legs. Fingers, hands, and arms can be affected and symptoms can progress to the central part of the body. Many people with diabetic neuropathy experience this pattern of ascending nerve damage.

Classifications

More than 100 types of peripheral neuropathy have been identified, each of which has a characteristic set of symptoms, developmental patterns, and prognosis. Functional impairment and symptoms depend on the type of nerve damaged: motor, sensory, or autonomic. :

  • The motor nerves control the movements of all muscles under conscious control, such as those used when walking, grasping things, or talking.
  • Sensory nerves convey information about sensory sensations, such as being lightly touched or pain from a cut.
  • Autonomic nerves regulate biological activities that humans do not consciously control, such as respiration, digestion of food, and heart and glandular function.

While some neuropathies can affect all three types of nerves, others mainly affect one or two types. Therefore, when describing a patient's condition, doctors can use terms such as:

  • Predominantly motor neuropathy
  • Predominantly sensory neuropathy
  • Sensory motor neuropathy
  • Autonomic neuropathy

Symptoms

The symptoms of peripheral neuropathy are associated with the type of nerve affected and can appear for days, weeks, or even years. Muscle weakness is the most common symptom of motor nerve injury . Other symptoms can include:

  • Painful cramps and twitching (uncontrolled muscle spasms visible under the skin)
  • Loss of muscle mass
  • Bone degeneration
  • Changes in skin, hair and nails .

The more general degenerative changes can also result from the loss of sensory or autonomic nerve fibers. Sensory nerve damage causes a more complex spectrum of symptoms because sensory nerves have a broader and more specialized spectrum of functions.

Larger sensory fibers

Larger sensory fibers encapsulated in myelin (a fatty protein that covers and insulates many nerves) register vibration, light touch, and positional sensation. Damage to large sensory fibers reduces the ability to feel vibration and touch, causing a general feeling of numbness, especially in the arms and legs.

People may feel like they are wearing gloves and stockings, even if they are not wearing them. Many patients are unable to feel the shapes of small objects or to distinguish their shapes by touch. This damage to sensory fibers can contribute to loss of reflexes (as can damage to motor nerves). Loss of sense of position often makes it impossible for people to coordinate complex movements, such as walking or buttoning, or balancing when their eyes are closed.

Neuropathic pain is difficult to control and can seriously affect emotional well-being and overall quality of life. Neuropathic pain is often worse at night, severely disturbing sleep, and exacerbating the emotional toll of sensory nerve damage .

Smaller sensory fibers

The smallest sensory fibers have practically no myelin sheath and are responsible for the transmission of pain and temperature sensations. Damage to these fibers can affect the ability to feel pain or changes in temperature.

People may not feel that they have been injured by a cut or that the wound is infected. Others may not find the pain that warns of an impending heart attack or other acute conditions. (Loss of pain is a particularly serious problem for people with diabetes, contributing to the high rate of lower limb amputation in this population. )

Pain receptors in the skin can also become hypersensitive, so people may feel severe pain (allodynia) due to irritants that are generally painless (for example, some may experience pain due to a sheet that covers their body lightly) .

Autonomic nerve damage

Symptoms of autonomic nerve damage are varied and depend on which organs or glands are affected. Autonomic neuropathy (autonomic nerve dysfunction) can be life-threatening and may require emergency medical attention if breathing is impaired or the heart begins to beat irregularly. Common symptoms of autonomic nerve damage can include:

  • Inability to sweat normally (which can lead to heat intolerance)
  • Loss of bladder control (which can lead to infection or urinary incontinence )
  • Failure to control the muscles that expand or contract blood vessels to maintain safe blood pressure levels.

Loss of blood pressure control can cause dizziness, dizziness, or even fainting when a person suddenly changes from sitting to standing (a condition known as postural or orthostatic hypotension).

Gastrointestinal symptoms often accompany autonomic neuropathy. The nerves that control the contraction of the intestinal muscles often fail, causing diarrhea, constipation, or urinary incontinence. Many people also have trouble eating or swallowing if certain autonomic nerves are affected.

Causes

Peripheral neuropathy can be acquired or inherited. Causes of acquired peripheral neuropathy include:

  • Physical damage (trauma) to a nerve
  • Tumors
  • Toxins
  • Autoimmune reactions
  • Lack of nutrients
  • Alcoholism
  • Vascular and metabolic disorders.

Acquired peripheral neuropathies fall into three broad categories:

  • Caused by systemic disease
  • Causes of trauma by external factors.
  • Those caused by infections or autoimmune diseases that affect the nervous tissue.

An example of acquired peripheral neuropathy is trigeminal neuralgia ( also known as tic pain), in which damage to the trigeminal nerve (a large nerve in the head and face) causes episodic attacks of excruciating lightning-like pain in the a side. faces.

In some cases, the cause is a previous viral infection, pressure on the nerve from a tumor or an inflamed blood vessel, or, rarely, multiple sclerosis .

However, in many cases, a specific cause cannot be established. Doctors commonly refer to neuropathies without a known cause as idiopathic neuropathies.

Physical trauma:   Physical injury (trauma) is the most common cause of nerve damage. Sudden trauma or injury to:

Traumatic injury can partially or completely break, crush, compress, or stretch the nerves, sometimes so violently that they partially or completely detach from the spinal cord. Less serious injuries can also cause serious nerve damage. Fractures or displaced bones can put damaging pressure on adjacent nerves, and sliding discs between vertebrae can compress nerve fibers where they exit the spinal cord.

Systemic diseases: Systemic diseases, including many disorders that affect the whole body, often cause metabolic neuropathies. These disorders can include metabolic and endocrine disorders. Nerve tissues are highly vulnerable to damage from diseases that affect the body's ability to convert nutrients into energy, recycle waste products, or produce the substances that make up living tissues.

Diabetes:   Diabetes mellitus, characterized by chronically elevated blood glucose levels, is the leading cause of peripheral neuropathy in the United States. About 60 to 70 percent of people with diabetes have mild or severe damage to the nervous system .

Kidney and liver diseases:   Kidney disease can cause excessive amounts of toxic substances in the blood, which can seriously damage nerve tissue. Most patients who require dialysis due to kidney failure develop polyneuropathy. Certain liver diseases also lead to neuropathies as a result of chemical imbalances.

Hormones:   Hormonal imbalances can disrupt normal metabolic processes and cause neuropathy. For example, inadequate production of thyroid hormones slows down metabolism, leading to fluid retention and tissue inflammation, which can put pressure on peripheral nerves.

Growth hormone overproduction can lead to acromegaly, a condition characterized by abnormal enlargement of many parts of the skeleton, including the joints. Nerves running through affected joints are often pinched.

Vitamin deficiency and alcoholism: Vitamin deficiency and alcoholism can cause extensive damage to nerve tissue. Vitamins E, B1, B6, B12, and Niacin are essential for healthy nerve function. Thiamine deficiency, in particular, is common among people with alcoholism because they often have poor eating habits as well. Thiamine deficiency can cause painful neuropathy in the extremities.

Some researchers believe that excessive alcohol consumption in itself may directly contribute to nerve damage, a condition called alcoholic neuropathy.

Damage to blood vessels and blood diseases:   Vascular damage and blood disorders can reduce oxygen supply to peripheral nerves and quickly lead to serious damage or death of nerve tissue, just as a sudden lack of oxygen to the brain can lead to stroke . Diabetes often damages the blood vessels .

Various types of vasculitis (inflammation of the blood vessels) often cause hardening, thickening of the walls of the blood vessels, and the formation of scar tissue , reducing their diameter and obstructing blood flow. This category of nerve damage (called multiple mononeuropathy or multifocal mononeuropathy) occurs when isolated nerves are damaged in different areas.

Connective tissue diseases and chronic inflammation:   Connective tissue diseases and chronic inflammation cause direct and indirect nerve damage. When several layers of protective tissue that surround the nerves become inflamed, the inflammation can spread directly to the nerve fibers.

Chronic inflammation also leads to progressive destruction of connective tissue, making nerve fibers more vulnerable to compression injuries and infections. Joints can become inflamed and swollen and pinch nerves, causing pain .

Cancers and tumors:   Cancer and benign tumors can invade nerve fibers or put damaging pressure on them. Tumors can also arise directly from cells in nervous tissue. Generalized polyneuropathy is often associated with neurofibromatosis, a genetic disorder in which multiple benign tumors grow in nerve tissue. Neuromas, benign formations of overgrown nerve tissue that can develop after any penetrating injury that breaks nerve fibers, generate very strong pain signals and sometimes invade adjacent nerves, resulting in more damage and more pain.

Neuroma formation can be one of the elements of a more common neuropathic pain condition called complex regional pain syndrome or reflex sympathetic dystrophy syndrome, which can be caused by traumatic injury or surgical trauma.

Paraneoplastic syndromes, a group of rare degenerative diseases that are triggered by the response of the human immune system to cancer, can also indirectly cause extensive nerve damage.

Repetitive stress:   Repetitive stress often leads to entrapment neuropathy, a special category of compression injury. Cumulative damage can result from repetitive, vigorous, and uncomfortable activities that require flexing of any group of joints for a long period of time. The resulting irritation can cause inflammation and swelling of ligaments, tendons, and muscles, narrowing the narrow passages through which some nerves pass. These injuries become more common during pregnancy, probably because weight gain and fluid retention also constrict nerve canals.

Toxins:   Toxins can also damage peripheral nerves. People who are exposed to heavy metals (arsenic, lead, mercury, thallium), industrial drugs, or environmental toxins often develop neuropathy.

Some anticancer drugs, anticonvulsants, antivirals, and antibiotics have side effects that can cause neuropathy secondary to the drugs, limiting their long-term use.

Infections and autoimmune diseases:   Infections and autoimmune disorders can cause peripheral neuropathy. Viruses and bacteria that can attack nerve tissue include:

  • Herpes zoster (shingles )
  • Epstein- Barr virus
  • Cytomegalovirus (CMV )
  • Herpes simplex

These viruses severely damage sensory nerves and cause episodes of sharp pain like lightning. Post-herpetic neuralgia often occurs after a shingles attack and can be particularly painful.

The human immunodeficiency virus (HIV), which causes AIDS, also causes serious damage to the central and peripheral nervous systems. The virus can cause several different forms of neuropathy, each of which is closely related to a specific stage of active immunodeficiency disease. Painful and rapidly progressing polyneuropathy affecting the feet and hands may be the first clinical sign of HIV infection.

Bacterial diseases such as Lyme disease, diphtheria , and leprosy are characterized by extensive peripheral nerve damage.

  • Diphtheria and leprosy are rare in the United States.
  • Lyme disease is on the rise. Lyme disease can cause a wide range of neuropathic disorders that can develop weeks, months, or years after a tick bite if left untreated.

Viral and bacterial infections can also cause indirect damage to the nerves, triggering conditions called autoimmune disorders, in which specialized cells and antibodies of the immune system attack the body's own tissues. These attacks usually cause destruction of the myelin sheath or axon of the nerve.

Some neuropathies are caused by inflammation caused by the activity of the immune system rather than by direct damage from infectious organisms .

Inflammatory neuropathies can develop quickly or slowly, and chronic forms can show an alternation of remission and relapse.

  • Guillain-Barré syndrome (acute inflammatory demyelinating neuropathy) can damage motor, sensory, and autonomic nerve fibers. Most people recover from this syndrome, although severe cases can be life-threatening.
  • Chronic inflammatory demyelinating polyneuropathy (CIDP) is usually less severe, usually damaging the sensory and motor nerves, leaving the autonomic nerves intact.
  • Multifocal motor neuropathy is a form of inflammatory neuropathy that exclusively affects the motor nerves; it can be chronic or acute.

Hereditary neuropathies:   Hereditary peripheral neuropathies are caused by inborn errors in the genetic code or new genetic mutations.

  • Some genetic errors lead to mild, symptomatic neuropathies that begin in early adulthood and lead to minor disabilities.
  • The most serious inherited neuropathies often appear during infancy or childhood.

The most common inherited neuropathies are a group of diseases collectively called Charcot-Marie-Tooth disease (arising from defects in the genes responsible for the production of neurons or the myelin sheath). Symptoms include:

  • Severe weakening and atrophy of the muscles of the legs and feet.
  • Gait abnormalities
  • Loss of tendon reflexes
  • Numbness in the lower extremities

Watch out

There are currently no medications that can cure inherited peripheral neuropathy. However, there are treatments for many other ways. These are the key points of peripheral neuropathy treatment.

  • Usually any underlying disease is treated first, followed by symptomatic treatment.
  • Peripheral nerves have the ability to regenerate if the nerve cell itself has not died.
  • Symptoms can often be controlled and addressing the causes of specific forms of neuropathy can often prevent further damage.
  • Positive changes and healthy habits often create conditions conducive to nerve regeneration.
  • Prompt treatment of injuries can help prevent permanent damage.

In general, the treatment of peripheral neuropathy involves adopting healthy habits to reduce physical and emotional stress, such as:

  • Maintain an optimal weight
  • Avoid exposure to toxins .
  • Follow an exercise program under the supervision of a doctor.
  • Eat a balanced diet
  • Correction of vitamin deficiency.
  • Limit or avoid alcohol consumption.

Other treatments for peripheral neuropathy include:

  • Exercise: Active and passive exercise can reduce cramps, improve muscle strength, and prevent muscle wasting in paralyzed limbs.
  • Diet and nutrition: Various dietary strategies can improve gastrointestinal symptoms.
  • Quitting smoking: Quitting smoking is especially important because smoking constricts the blood vessels that carry nutrients to the peripheral nerves and can make neuropathic symptoms worse.
  • Self-care skills: Self-care skills, such as careful foot care and careful wound care in people with diabetes and others with pain problems, can relieve symptoms and improve quality of life .

Systemic diseases

Systemic diseases often require more complex treatment. Tight blood glucose control has been shown to reduce neuropathic symptoms and help people with diabetic neuropathy avoid further nerve damage.

The inflammatory and autoimmune conditions that lead to neuropathy can be controlled in a number of ways, including immunosuppressants, such as:

  • Prednisone
  • Cyclosporine (Neoral, Sandimmune)
  • Imuran (azathioprine)

Plasmapheresis – Plasmapheresis, a procedure in which blood is drawn, immune cells and antibodies are removed, and then returned to the body, can limit inflammation or suppress the activity of the immune system. High doses of immunoglobulins, proteins that act like antibodies, can also suppress abnormal activity of the immune system.

Anesthesia:   Neuropathic pain is often difficult to control. Sometimes mild pain can be relieved with over-the-counter pain relievers. Several classes of drugs have been shown to be beneficial for many patients with more severe chronic neuropathic pain. This includes:

  • Mexiletine, a medicine designed to correct irregular heart rhythms (sometimes associated with serious side effects).
  • Various antiepileptic drugs, including Neurontin (gabapentin), Lyrica (pregabalin), phenytoin, and carbamazepine.
  • Certain classes of antidepressants, including tricyclic medications such as amitriptyline (Elavil, Endep)

Injections of local anesthetics such as lidocaine or topical patches that contain lidocaine can relieve more severe pain.

In the most severe cases, doctors can surgically destroy the nerves; however, the results are usually temporary and the procedure can cause complications.

Assistive Devices: Mechanical assistive devices and other assistive devices can help reduce pain and reduce the impact of physical disability.

  • Arm or leg braces can compensate for muscle weakness or relieve nerve compression.
  • Orthopedic shoes can improve gait disturbances and help prevent foot injuries in people with loss of pain.
  • If breathing is severely impaired, mechanical ventilation can provide life support.

Operation:   Surgery can often provide immediate relief from mononeuropathy caused by compression or entrapment.

  • Repairing a slipped disc can relieve pressure on the nerves leading from the spinal cord.
  • Removal of benign or malignant tumors can also reduce harmful pressure on nerves .
  • A pinched nerve can often be corrected by surgically releasing the ligaments or tendons.
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