Peripheral Neuropathy

In the most common form of peripheral neuropathy, symptoms are symmetrical and involve both hands and feet.

Peripheral neuropathy is a disorder of nerve(s) excluding those triggered by the brain and spinal cord. Patients may experience tingling, numbness, unusual sensations, weakness, or burning pain in the affected area. The symptoms are often present in areas covered by gloves or stockings, giving peripheral neuropathy a "glove and stocking" distribution.

Peripheral neuropathy can involve different nerve types, including motor, sensory, and autonomic nerves. It can also be categorized by the size of the nerve fibers involved, large or small.

Neuropathy can present with various symptoms, including numbness, different types of pain, weakness, or loss of balance, depending on the type of nerve involved. Autonomic neuropathy manifests with symptoms that affect bodily functions we do not consciously think of, such as heart rate, digestion, and emptying of the bowel and bladder. Symptoms may include problems with blood pressure, voiding, the passage of stools, heart rate, or sweating.

Cranial neuropathy is similar to peripheral neuropathy, except that it involves the cranial nerves. Any of the cranial nerves can be affected. One common cause of cranial neuropathy is the loss of blood flow from the optic artery to the optic nerve, leading to vision loss. Amyloidosis is a common cause of this rare disorder.

Specific nerves can be affected in neuropathy. When a particular nerve is involved, the symptoms are limited to the distribution of that nerve. For example, the median nerve at the wrist is commonly affected in carpal tunnel syndrome. Essentially any peripheral nerve can become entrapped and cause signs and symptoms of neuropathy. The ulnar nerve is commonly entrapped at the elbow, the peroneal nerve is exposed to the outer part of the knee, and the pudendal nerve can cause pain in the perineum. Entrapment of the lateral femoral cutaneous nerve at the waist, known as meralgia paresthetica, causes numbness in the outer part of the thigh.

Causes of peripheral neuropathy

There are 11 possible causes of peripheral neuropathy:

1. Diabetes mellitus
2. Shingles (postherpetic neuralgia)
3. Vitamin deficiency, particularly B12 and folate
4. Alcohol use
5. Autoimmune diseases, including lupus, rheumatoid arthritis, or Guillain-Barre syndrome
6. AIDS, syphilis, and kidney failure
7. Inherited disorders, such as amyloid polyneuropathy or Charcot-Marie-Tooth disease
8. Toxin exposure, such as heavy metals, gold compounds, lead, arsenic, mercury, and organophosphate pesticides
9. Cancer therapy drugs and other medications, such as antibiotics including metronidazole (Flagyl) and isoniazid
10. Rare diseases such as neurofibromatosis, Fabry disease, Tangier disease, hereditary sensory autonomic neuropathy, and hereditary amyloidosis
11. Statin medications, although only rarely causing symptoms

Main cause of peripheral neuropathy

While diabetes and postherpetic neuralgia are the most common causes of peripheral neuropathy, oftentimes no cause is found. In these cases, it is referred to as idiopathic peripheral neuropathy.

Sometimes, peripheral nerve entrapments, such as carpal tunnel syndrome, are considered peripheral neuropathies. In these cases, pressure on the nerve leads to nerve malfunction.

Four types of peripheral neuropathy

The four types of neuropathies involve:

• Peripheral distal symmetry polyneuropathy: It is the most common form of neuropathy, affecting the nerves in the legs, feet, hands, and arms.
• Autonomic neuropathy: It affects the autonomic nerves that control the majority of the body’s functions.
• Proximal motor neuropathy: This type of neuropathy causes muscle weakness, mainly in the upper part of the legs, buttocks, and hips.
• Focal mononeuropathy: Only one specific type of nerve is affected in this type of neuropathy.

Symptoms of peripheral neuropathy

The symptoms of peripheral neuropathy somewhat depend on the cause. Usually, peripheral neuropathy affects the nerves responsible for sensation. As a result, people develop pain, burning, or tingling in the distribution of the affected nerves. This is most commonly felt in the feet and/or hands, causing tingling, numbness, and/or burning in the toes or fingers.

When shingles cause peripheral neuropathy, the affected nerve causes a localized burning and itching sensation, such as in the side of the chest, face, or buttock.

Diagnosis of peripheral neuropathy

Diagnosing peripheral neuropathy involves performing a thorough medical history and physical examination due to its many causes and presentations. Certain tests are done during the physical exam:

• Vibration and monofilament testing are accurate in diagnosing certain types of peripheral neuropathy.
• Blood tests for exposure to toxins and electrodiagnostic studies, such as nerve conduction studies (NCS) and electromyography (EMG), are also useful but not for diagnosing small fiber neuropathy.
• Skin biopsies or quantitative sudomotor axon reflex testing (QSART) can help diagnose small fiber neuropathy.
• An MRI or CT may be performed to exclude a brain disease.

Treatment for peripheral neuropathy

The treatment for peripheral neuropathy depends on its cause. The first step is to look for the cause.

• Vitamin deficiencies can be corrected.
• Diabetes can be controlled, although control may not reverse the neuropathy.
• Neuropathies associated with immune diseases can improve with treatment of autoimmune diseases.
• Neuropathy caused by nerve entrapment can be treated with physical therapy, injections, or surgery.
• Prompt treatment with sympathetic injections can minimize the chance of shingles progressing to postherpetic neuralgia.

If a specific treatment isn’t available, the pain of neuropathy can usually be controlled with medications.

• Over-the-counter medications such as acetaminophen, ibuprofen, or aspirin can help.
• Tricyclic antidepressants and anti-seizure medications have been used to relieve neuropathic pain.
• Capsaicin, available as a cream, can help relieve the pain of peripheral neuropathy.
• Pregabalin and duloxetine have been approved for treating diabetic peripheral neuropathy.
• Sometimes, opioids can be used to control neuropathic pain.

Vitamin B6 and alpha-lipoic acid have been used to relieve chemotherapy-induced peripheral neuropathy.

Ongoing research is being conducted to find new treatments for peripheral neuropathy, including topical gels and bone marrow treatments.

If you believe you have peripheral neuropathy, contact your healthcare professional, as many causes can be successfully treated.

Prevention of peripheral neuropathy

Certain forms of peripheral neuropathy can be prevented by avoiding alcohol toxicity, getting shingles vaccinations, avoiding heavy metal toxicity, and treating diabetes aggressively.