Definition

Peripheral neuropathy is damage to the peripheral nerves. Peripheral nerves are the nerves that connect your spinal cord to the rest of your body.

Peripheral Nerves of the Foot

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Causes

Many diseases and conditions can cause peripheral neuropathy. The damage may occur due to:

  • Lack of oxygen
  • Malnutrition
  • Compression
  • Cancer
  • Trauma
  • Inflammation
  • Toxins
  • Medications
  • Unknown causes

Diseases that can damage peripheral nerves include:

Compression commonly occurs when nerves are pinched or trapped somewhere along their course. Examples include:

Toxins that can damage the peripheral nerves include:

  • Lead
  • Mercury
  • Thallium
  • Organic solvents (hexacarbons)
  • Pesticides (organophosphates)
  • Carbon disulfide
  • Arsenic
  • Acrylamide
  • Diphtheria toxin
  • Alcohol

Many medications can lead to peripheral neuropathy. A partial list includes:

  • Chemotherapeutic agents to treat cancer (vincristine, paclitaxel, cisplatin, suramin)
  • Anti-HIV medications (didanosine, zalcitabine)
  • Antituberculosis medications (isoniazid, ethambutol)
  • Other antimicrobial drugs (dapsone, metronidazole, chloroquine, chloramphenicol)
  • Psychiatric medications (lithium)
  • Miscellaneous (amiodarone, aurothioglucose, phenytoin, thalidomide, colchicine, cimetidine, disulfiram, hydralazine, high levels of vitamin B6)

Other causes of peripheral nerve damage include:

Risk Factors

A risk factor is something that increases your chance of getting a disease or condition. Risk factors for peripheral neuropathy include:

  • Diabetes—about 60% of people with diabetes have peripheral neuropathy
  • Alcohol abuse
  • Autoimmune diseases, such as rheumatoid arthritis or celiac sprue
  • Family member with peripheral neuropathy
  • Exposure to toxins or medications known to cause neuropathy
  • Vitamin deficiency (thiamin and vitamin B12)
  • HIV infection
  • Pressure on a nerve (may occur with repetitive stress injuries)

Symptoms

Damage to the peripheral nerves often results in sensory (feeling) and motor (strength) symptoms in the arms, legs, hands, and feet. However, it can affect any part of the body. Symptoms vary, depending on which nerves are involved.

Symptoms may range from mild to severe and may seem worse at night. Sensations and pain may occur in the upper or lower limbs and progress toward the trunk, for instance from the feet to the calves.

Symptoms include:

  • Numbness or reduced sensation
  • Tingling
  • Pain, often a burning or sharp, cutting sensation
  • Sensitivity to touch
  • Muscle twitches
  • Muscle weakness
  • Muscle cramping
  • Difficulty with walking
  • Loss of coordination or balance

If untreated, peripheral neuropathy can lead to:

  • Loss of reflexes and muscle control
  • Muscle atrophy (loss of muscle bulk)
  • Foot deformities
  • Foot ulcers
  • Injuries to the feet that go unnoticed and become infected
  • Autonomic dysfunction (sweating, bowel and bladder dysfunction, cardiovascular effects)

Diagnosis

The doctor will ask about your symptoms and medical history, and perform a physical exam. The physical exam will include tests of:

  • Muscle strength
  • Reflexes
  • Balance
  • Coordination
  • Ability to feel vibration, temperature, and light touch

Additional tests may also include:

  • Blood tests (including glucose, vitamin B12 level, and thyroid function tests)
  • Electromyography (EMG)—measurement and recording of electrical activity generated in muscle in response to a nervous stimulation
  • Nerve conduction studies
  • Nerve or muscle biopsy (rarely)
  • Evaluation of family members
  • Genetic testing
  • Serum/urine electrophoresis (protein evaluation)
  • Spinal tap for demyelinating disorders

Treatment

Treatment may include:

Treating the Underlying Illness or Exposure

Treating the underlying illness can decrease or eliminate symptoms. For instance, if it is caused by diabetes, controlling blood sugar levels may help. In some cases, neuropathy caused by medications or toxins is completely reversed when these substances are stopped or avoided. Correction of vitamin B12 deficiency often improves symptoms.

Physical Therapy

Certain exercises may help stretch shortened or contracted muscles and increase joint flexibility. In long-standing cases, splinting the joint may be required to protect and rest it, while maintaining proper alignment.

Patients may also benefit from orthotics to help with deformities, balance issues, and muscle weakness. Maintaining physical activity is also key.

Medications

Prescription and over-the-counter (OTC) pain medications are often used to ease discomfort.

Drugs to treat depression and prevent convulsions sometimes relieve neuropathy symptoms. These medications are often given at lower dosages than those prescribed for depression and seizures.

Commonly used antidepressants include:

  • Amitriptyline (Elavil)
  • Nortriptyline (Pamelor)
  • Desipramine (Norpramin)
  • Imipramine (Tofranil)

Commonly used anticonvulsants may include:

  • Gabapentin (Neurontin)
  • Carbamazepine (Tegretol)
    • According to a recent Food and Drug Administration (FDA) bulletin, patients of Asian ancestry who have a certain immune system gene, called HLA-B*1502, and take carbamazepine are at risk for dangerous or even fatal skin reactions (Stevens-Johnson syndrome and toxic epidermal necrolysis). Because of this, the FDA recommends that individuals of Asian descent get tested for HLA-B*1502 before starting carbamazepine treatment.
    • If you have been taking carbamazepine for a few months with no skin reactions, then you are at low risk of developing these reactions. Additionally, you should not stop taking this medication unless told to do so by your doctor. If you test positive for HLA-B*1502, the FDA further recommends that you should not start carbamazepine treatment unless the benefits clearly outweigh the risks.*
  • Pregabalin (Lyrica)—recently approved for peripheral neuropathy

Some peripheral neuropathies that are severe and potentially life-threatening (such as Guillain-Barre syndrome) require treatment with steroids (such as prednisone) and intravenous immunoglobulins.

Other Therapies

These therapies are aimed at reducing symptoms and may include:

  • Relaxation training
  • Biofeedback
  • Walking
  • Exercise
  • Yoga
  • Warm baths
  • Massage
  • Acupuncture
  • Transcutaneous electronic nerve stimulation

Surgery

Surgery can relieve the pressure on nerves caused by compression or entrapment. For example, surgeons commonly release fibrous bands in the wrist to treat carpal tunnel syndrome.

Prevention

  • Manage chronic medical conditions with the help of your physician. If you have diabetes, you should visit a podiatrist for yearly exams.
  • Eat a healthful diet, one that is low in saturated fat and rich in whole grains, fruits, and vegetables.
  • Be sure to get recommended amounts of thiamin and vitamin B12.
  • Avoid excessive consumption of alcohol.
  • Avoid toxic chemicals.
  • Avoid repetitive movements.
  • Avoid prolonged pressure on joints, especially elbows and knees.