What Is Peripheral Neuropathy?

Peripheral nerves are thin structures located in your arms, legs, and throughout your body. When one or more of these nerves become damaged—as a result of an underlying disease process, medication, or infection, to name a few possibilities—a condition called peripheral neuropathy develops.

The diagnosis of peripheral neuropathy requires a careful and thorough medical history and neurological examination. Various blood or nerve-related tests are also often required. For the treatment of peripheral neuropathy, a healthcare provider will address the underlying cause behind the neuropathy, as well as prescribe medication(s) to ease symptoms like numbness, tingling, and pain.

Peripheral Nervous System

Your nervous system is divided into two parts—your central nervous system and your peripheral nervous system.

Your central nervous system consists of your brain and spinal cord. Your peripheral nervous system consists of all the nerves that are located outside of your brain and spinal cord. The function of peripheral nerves is to relay messages from your brain and spinal cord to the rest of your body, such as your arms, hands, legs, feet, internal organs, skin, and joints.

Since the peripheral nerves are not protected by the skull (as the brain is) or the vertebral spinal canal (as the spinal cord is), they are vulnerable to damage. When this happens to one or more of the peripheral nerves, peripheral neuropathy develops.

Types of Peripheral Neuropathy

Most of the time when you hear the term "peripheral neuropathy," it's in reference to a polyneuropathy—one of many conditions in which multiple peripheral nerves are damaged. There are also localized types of peripheral neuropathies, called mononeuropathies.

Polyneuropathy

The nerves affected by polyneuropathy may include one or more of the following:

• Sensory nerves: These nerves receive input from various locations of the body. They then send messages to the brain about the body’s sensations, such as hot and cold, pain, and touch.
• Motor nerves: These nerves transmit messages from the brain and spinal cord, telling various muscles to move.
• Autonomic nerves: These nerves regulate how your internal organs, such as your blood vessels, stomach, heart, and sweat glands, function.

Polyneuropathies are further classified based on their underlying cause.

For example, diabetic polyneuropathy is one of the most common types of polyneuropathies. It occurs as a result of nerve damage from high blood sugar levels.

While diabetic polyneuropathy predominantly affects sensory nerves, it can affect motor and autonomic nerves. Depending on what nerves are damaged, symptoms like numbness, tingling, pain, weakness, or digestive or urinary system problems may develop.

Another example of a polyneuropathy is vitamin B12 deficiency neuropathy. This disorder is more common in older adults because they are more at risk for gut malabsorption issues.

Since vitamin B12 deficiency neuropathy affects both sensory and motor peripheral nerves, symptoms may include pain, balance problems, numbness and tingling in the hands and feet, and weakness.

A severe but uncommon type of polyneuropathy is Guillan-Barré syndrome, also called acute demyelinating polyneuropathy. This dangerous disease affects both sensory and motor nerve cells and is characterized by a quickly progressing tingling and weakness, usually beginning in the feet with rapidly ascending weakness of the legs. Eventually, weakness of the muscles that control breathing occurs.

Mononeuropathy

Mononeuropathy means that a single peripheral nerve is damaged, usually as a result of trauma, compression, or entrapment.

The most classic example of a mononeuropathy is carpal tunnel syndrome, which refers to compression of the median nerve. This causes numbness and tingling in the thumb, index finger, middle finger, and part of the ring finger. If left untreated or in severe cases, hand weakness and loss of dexterity may develop.

Mononeuritis Multiplex

Sometimes, two or more nerves in different areas are affected. When this happens, the condition is called mononeuritis multiplex.

Blood vessel problems (for example, from an inflammatory condition called vasculitis) are typical culprits of mononeuritis multiplex.

With vasculitis neuropathy, impaired blood flow to at least two peripheral nerves results in asymmetrical pain, muscle weakness, and/or sensory disturbances.

Peripheral Neuropathy Symptoms

Specific symptoms and signs related to a peripheral neuropathy largely depend on the type of peripheral nerve that is affected—sensory (most common), motor, autonomic, or some combination.

Sensory

When sensory nerves are damaged, one or more of the following symptoms or signs may occur:

• Lack of sensation to pain changes in temperature
• Unusual sensations like vibration, numbness and tingling, burning, stabbing, electrical, or crawling
• Pain from a light touch that is normally painless (allodynia)
• Loss of position sense and balance problems
• Change in temperature

Motor

When motor nerves are damaged, the most common symptom is muscle weakness.

Other symptoms and signs may include:

• Muscle cramping and shrinking
• Fasciculations (when a muscle twitches without your control)
• Reflex abnormalities

Autonomic

Common symptoms and signs of autonomic nerve damage include:

• Excess sweating
• Dry skin and body hair loss
• Diarrhea
• Rapid heartbeat
• Bladder problems
• Heat intolerance
• Early satiety
• Impotence
• Orthostatic hypotension (feeling faint or dizzy when sitting from lying down or standing from sitting)

Causes

Anything that damages one or more of the peripheral nerves may result in peripheral neuropathy.

Classic causes of peripheral neuropathy include:

• Diabetes
• Trauma or compression
• Shingles (reactivation of the chicken pox virus that causes a painful rash)
• Alcohol abuse
• Vitamin B12 deficiency
• Hypothyroidism (an underactive thyroid gland)

Medications, especially various chemotherapies, are also potential culprits of peripheral neuropathy, as is heavy metal exposure, HIV (human immunodeficiency virus) infection, kidney failure, chronic liver disease, and rarely, inherited diseases like Charcot-Marie-Tooth disease.

Diagnosis

The diagnosis of peripheral neuropathy begins with a neurological examination. Testing then follows, some of which will depend on what diagnoses your healthcare provider suspects based on your symptoms and medical history.

Neurological Examination

During the exam, your healthcare provider will check your reflexes and evaluate for various sensation disturbances (vibration, temperature, and pinprick), especially on your feet and hands. Your healthcare provider will also evaluate your muscle strength and your gait.

Blood Tests

In order to sort out the root cause of your peripheral neuropathy, your healthcare provider will order a series of blood tests, with some of the most common ones being:

• Complete blood count (CBC)
• Comprehensive metabolic panel (CMP)
• Erythrocyte sedimentation rate (ESR)
• Fasting blood glucose
• Vitamin B12 level
• Thyroid-stimulating hormone

Additional blood tests—for example, genetic testing for Charcot-Marie-Tooth disease or an HIV antibody test for HIV infection—may also be ordered based on your healthcare provider's underlying suspicion.

Nerve-Specific Tests

In some cases, a nerve conduction velocity study (NCV) and electromyography (EMG) (tests to see how fast electrical signals move through your nerves) are used to confirm a diagnosis of peripheral neuropathy.

Likewise, sometimes a nerve biopsy (when a sample of nerve tissue is removed and examined under a microscope) or a neurodiagnostic skin biopsy (when a tiny piece of skin containing nerve fiber endings is removed and examined under a microscope) may be performed.

Autonomic Tests

For peripheral neuropathies with autonomic symptoms, various autonomic tests may be helpful in the diagnostic process, such as measuring a person's heart rate response to tilt (to check for orthostatic hypotension) or tests of sweat function.

Other Tests

Besides various blood and nerve-related tests, sometimes other tests are needed to help confirm the cause of a person's peripheral neuropathy.

For instance, a cerebrospinal fluid analysis via a lumbar puncture (spinal tap) may be performed to support a diagnosis of Guillain-Barré syndrome. A 24-hour urine collection may be ordered for possible heavy metal exposure.

Differential Diagnosis

It's important to note that during the diagnostic process for peripheral neuropathy, your healthcare provider will want to ensure that your symptoms are not due to a condition of the central nervous system (CNS).

CNS conditions that may mimic various peripheral neuropathies include stroke and multiple sclerosis (MS).

The good news is that a careful medical history and neurological exam can usually distinguish central from peripheral nervous system conditions. For example, brisk reflexes and spastic (tight, stiff) muscles may be seen with a central nervous system disease, like MS, but not with peripheral neuropathy.

Likewise, with a stroke—which is caused by inadequate blood flow to the brain—symptoms usually occur suddenly, as opposed to the symptoms of peripheral neuropathy, which develop over a longer period of time.

Treatment

Tackling the "why" behind your peripheral neuropathy is a crucial first step in treatment.

For example, if neuropathy is occurring as a result of diabetes, then obtaining better and tight control of glucose (blood sugar) levels may help preserve nerve function. Likewise, if a nutritional deficiency is the neuropathy culprit, correcting it should help the neuropathy.

For medication or toxin-induced neuropathies, removing the offending agent or lowering/altering the dose may be recommended.

For other types of neuropathy, more urgent, invasive treatments are required. For example, with Guillain-Barré syndrome, people usually require hospitalization and treatment with intravenous immunoglobulin or plasmapheresis in order to improve symptoms and shorten the disease course.

Easing Symptoms

Several medications are available to help ease the symptoms of peripheral neuropathy, such as numbness and pain.

Examples of such medications include:

• Neurontin (gabapentin)
• Lyrica (pregabalin)
• Cymbalta (duloxetine)
• Elavil (amitriptyline)
• Lidoderm (lidocaine 5% patch)
• Zostrix (capsaicin)

Analgesics like tramadol or various opioids, or complementary therapies like acupuncture, may also be added on for pain control.

In addition to medication, physical therapy and the use of walking assistive devices can help people with neuropathy-related weakness and balance problems.

Regular foot care by a podiatrist to prevent the development of foot ulcers and infections is also an important part of a treatment plan, especially for those with diabetic neuropathy.

A Word From Verywell

Peripheral neuropathy is a fairly common condition with a variety of causes. If you or a loved one has been diagnosed with peripheral neuropathy, it may help to know that there are a number of medical treatments that can reduce pain and discomfort. Additionally, treatments tailored to the cause of your neuropathy can help prevent it from getting worse and may, in some cases, reverse it.