What Is Peripheral Neuropathy?
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Medically reviewed by Brigid Dwyer, MD
Peripheral neuropathy refers to a collection of conditions in which the peripheral nervous system, the part of the nervous system outside the brain and spinal cord, has been damaged. Some kind of peripheral neuropathy affects about 2% of people overall, but around 8% of those over age 55.
Many different causes can lead to peripheral neuropathy, but diabetes is the most common. It most often leads to a symmetric pattern of symptoms that begin in the feet. Treatment focuses on addressing the underlying cause and using medication to reduce the pain.
Types
Many kinds of peripheral neuropathy exist, and they are sometimes organized in different ways.
Nerve Type
Motor nerves are the peripheral nerves that send signals from the brain to your muscles, which allow you to move. In contrast, sensory nerves pick up signals of sensations and send that info to the brain.
Peripheral neuropathy will usually affect both sensory and motor nerves, although sensory symptoms may be more dominant. However, some less common conditions can affect one but not the other.
Some peripheral neuropathies affect a different kind of nerve, called autonomic nerves. These are the nerves that bring information to and from your internal organs.
Additionally, some conditions are described as affecting small versus large nerve fibers. Large nerve fibers carry motor, sensory, and some other information, whereas small nerve fibers carry autonomic nerves as well as nerves for pain and temperature.
Length Dependent Vs. Non-Length Dependent
In length-dependent neuropathy, the parts of nerves farthest from the brain are affected first. So, the toes and feet are most likely to be first affected before the symptoms begin moving up the leg, symmetrically.
Some less common neuropathies are “non-length dependent” and don’t appear with this sort of pattern. One example is chronic inflammatory demyelinating polyneuropathy (CIDP), which is a condition characterized by progressive weakness and reduced feeling sensitivity in the arms and legs.
Number and Location of Nerves
Some kinds of peripheral neuropathy are mononeuropathies, meaning that they just affect one nerve. For example, ulnar neuropathy is a type of peripheral neuropathy that affects the ulnar nerve at the wrist, causing pain, weakness, and loss of sensation in the region. A polyneuropathy, in contrast, affects more than one nerve.
Neuropathy can occur in one area of the body (monofocal peripheral neuropathy) or multiple areas (multifocal neuropathy). Monofocal neuropathy affects a nerve or related group of nerves in one part of the body alone, unlike multifocal neuropathy, which causes asymmetric weakness in multiple different parts of the body.
Acute vs. Chronic Neuropathy
Another important distinction is acute versus chronic neuropathy. More commonly, people develop symptoms that develop slowly and worsen over months or years. However, some kinds of neuropathy come on in a few weeks or less. For example, Guillain-Barré syndrome is a rare, acute neuropathy that causes your immune system to attack your peripheral nervous system.
Acute neuropathies are more likely to be inflammatory in nature, and much of the damage occurs from an overactive immune response. Inflammatory neuropathies often need a different treatment approach than neuropathies that cause less inflammation.
Peripheral Neuropathy Symptoms
Most commonly, peripheral neuropathy shows up with a chronic, length-dependent, non-inflammatory pattern affecting the motor and sensory nerves, with sensory problems first. However, symptoms of peripheral neuropathy vary based on which of your nerves are affected and the severity of your condition.
Some potential symptoms include:
Uncomfortable tingling sensation
A burning kind of pain
Loss of sensation
Loss of pain
Inability to sense temperature or vibration
Problems with balance
Muscle weakness
Decreased muscle size (muscle wasting)
Muscle weakness most often affects the furthest parts of the extremities (e.g., the hands and feet). So you may have trouble lifting your foot or performing fine motor movements with your hands.
Some people also experience problems from autonomic nerve dysfunction, such as:
Lack of sweating
Bloating
Lightheadedness or fainting
Bladder problems
Sexual dysfunction
Symptom Examples
In diabetic neuropathy, symptoms most commonly start in both feet, moving to the calves and spreading to the hands about when they reach the knees. It can cause tingling, numbness, and decreased sensation, but weakness isn’t as much of a problem. However, other less common patterns sometimes occur, and autonomic symptoms are also possible.
Importantly, many people with diabetic neuropathy actually don’t have noticeable pain, even though it’s clear that they have reduced sensation. These people are at risk of injuring their feet and then not taking care of them properly, because they can’t feel them normally. Such injuries can even sometimes make amputation necessary.
In contrast, a condition like Charcot-Marie-Tooth disease, the most common genetic cause of peripheral neuropathy, tends to cause more problems with movement. It causes predominant symptoms like weakness or paralysis of the feet and lower leg muscles and hands, foot deformities, and problems with balance, with fewer sensory or pain issues.
What Causes Peripheral Neuropathy?
Damage to the peripheral nervous system causes the symptoms of peripheral neuropathy. This can happen in lots of different ways.
Worldwide, diabetes is the most common cause of peripheral neuropathy. It may affect around half of people with diabetes. Those who have had the condition longer and who haven’t had their blood glucose well-controlled are at higher risk.
However, peripheral neuropathy has many other different potential causes. Some of these include:
Nerve compression or other injury
Excess alcohol consumption
Long-term exposure to toxins
Medications, including chemotherapy
Autoimmune diseases, like lupus
Hereditary diseases
Monoclonal gammopathies, including multiple myeloma
Vasculitis
Nutritional deficiencies (e.g., vitamin B12)
Infectious diseases, such as leprosy, shingles, Lyme disease, or human immunodeficiency virus (HIV)
However, no cause can be found in roughly a quarter of people with peripheral neuropathy.
Diagnosis
Taking a thorough medical history and conducting a physical exam are key parts of diagnosis, and can help your healthcare provider determine the exact nature of the symptoms and how they have evolved. During the exam, your provider will check for signs such as muscle weakness, decreased sensation, and loss of reflexes.
In some cases, such a medical history and physical exam is enough to diagnose peripheral neuropathy. For example, if you have diabetes as well as symptoms that characteristically occur in diabetic neuropathy, your diabetes is the most likely cause.
Testing
Some tests are also helpful in finding the underlying cause of peripheral neuropathy, if not known. These blood tests may include:
Fasting blood glucose and hemoglobin A1c test: Used to screen for diabetes
Complete blood count: Overall health indicator and can show signs of infectious causes
Test for kidney or liver function: Assess the health status of these organs
Tests of inflammation, like C-reactive protein (CRP): May indicate inflammatory cause
Thyroid function tests: Assess thyroid health
Vitamin B12 levels: Can show potential deficiency
Serum electrophoresis: Test for monoclonal gammopathy or multiple myeloma
Tests for specific suspected infections: Can test for pathogens like HIV
Antinuclear antibody: Can give clues of autoimmune origin
Genetic tests: Can identify hereditary forms of peripheral neuropathy
In some cases, it is also helpful to get more detailed information about how your nerves have been affected. Your healthcare provider can do this through electromyography (EMG) and nerve conduction studies. For example, this might be necessary in someone with more atypical symptoms or in someone with sudden or severe symptoms.
The EMG provides information about the electrical signals going through your muscles, and the nerve conduction tests show how the electrical signal is traveling through your nerves. Together, these might help give more information about a specific kind of peripheral neuropathy.
Treatments for Peripheral Neuropathy
A key part of treatment is identifying the underlying cause of the neuropathy and treating it. Sometimes, your symptoms may go away when the underlying cause is addressed. But other times you may be left with residual symptoms, even after this is corrected.
Some people need treatment to help them cope with the burning kind of pain of peripheral neuropathy. Commonly prescribed medications include:
Neurontin (gabapentin)
Elavil (amitriptyline)
Cymbalta (duloxetine)
Effexor (venlafaxine)
Medications directly applied to the skin, such as a lidocaine or capsaicin patch, are also sometimes helpful.
People with certain subtypes of peripheral neuropathy may also need additional treatment. For example, someone with an inflammatory peripheral neuropathy like CIDP might need treatments to tamp down their immune response, such as corticosteroids and Rituxan (rituximab).
Prevention
Not all cases of peripheral neuropathy can be prevented. However, for people with diabetes, maintaining normal blood sugar levels can help prevent the onset of peripheral neuropathy. Work with your endocrinologist (a doctor who specializes in the conditions affecting the adrenal and pituitary glands, like diabetes) to find the best treatment plan to help prevent this and other potential complications of diabetes.
Comorbid Conditions
People with diabetic neuropathy often have other complications from poorly controlled diabetes. For example, someone with diabetic neuropathy is likely to also have signs of retinopathy, or damage to the blood vessels of the retina at the back of the eye. These are also likely to have nephropathy, or deterioration of their kidneys.
Living With Peripheral Neuropathy
The outlook is good for most people with peripheral neuropathy. Usually it is a manageable condition, although sometimes an uncomfortable one.
If you have diabetes, you may be able to keep your symptoms from getting worse by keeping your blood glucose under control. This may be an even more important goal for minority populations in the US, who face greater rates of complications from diabetes.
Foot care is also critical. Anyone with limited sensation in their feet should monitor them regularly and get prompt treatment at any signs of injury.
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