Peripheral Neuropathy

The nervous system is divided up into the central nervous system and the peripheral nervous system.  The nervous system consists of the brain and the spinal cord.  The peripheral nervous system is located outside of the brain and spinal cord.  The peripheral nervous system consists of the following:

  • sensory nerves which transmit messages about sensations such as heat, pain or touch; 
  • motor nerves which transmit messages that control movement; 
  • autonomic nerves which are responsible for involuntary functions such as blood pressure, digestion, breathing and sexual function. 

Damage to the nerves in the peripheral nervous system is called peripheral neuropathy.

Causes

  • inherited disorders;
    • amyloid polyneuropathy
    • Charcot-Marie Tooth disease
  • diabetes;
  • disorders of metabolism;
  • excessive alcohol use;
  • uremia (secondary to kidney failure);
  • cancer;
  • vitamin deficiency (especially vitamin B-12);
  • hypothyroidism (underactive thyroid);
  • infectious diseases;
    • hepatitis
    • diphtheria
    • Colorado tick fever
    • AIDS
    • leprosy
    • lyme disease
    • HIV Infection
    • syphilis
  • autoimmune diseases;
    • lupus
    • rheumatoid arthritis
    • Guillain-Barré syndrome
    • Sjögren’s disease
  • liver disease;
  • drugs;
    • Certain cancer chemotherapy drugs,
    • Certain antibiotics such as ciprofloxacin (Cipro) or metronidazole (Flagyl), and
    • isoniazid (Nydrazid, Laniazid).
  • carpal tunnel syndrome;
  • Bell’s palsy;
  • post herpetic neuralgia (shingles);
  • exposure to toxins;
    • heavy metals (arsenic, lead, mercury etc.),
    • nitrous oxide,
    • certain industrial agents such as solvents,
    • sniffing glue,
    • gold compounds, and
    • organophosphate pesticides.
  • miscellaneous causes; and
    • prolonged hypothermia (exposure to cold temperatures),
    • prolonged hypoxia (decreased oxygen), and
    • prolonged ischemia (decreased blood flow).
  • nerve pressure or trauma.
    • repetitive movements,
    • tight cast, and
    • tumor.

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Symptoms

The symptoms depend on whether sensory, motor, and/or autonomic nerves are affected. One, two or all three types of nerves can be affected. The symptoms also depend on whether one nerve is involved or whether, in addition, a large part or whole part of the body is affected. 

Sensory Nerves

  • Nerve pain, tingling, numbness, burning sensations, changes in sensation or incoordination may occur with damage to sensory fibers.  Often, the sensation changes begin in the feet and progress toward the center of the body. 

Motor Nerves

  • Weakness, atrophy, cramps, paralysis, muscle twitching, lack of muscle control and lack of dexterity can occur when damage occurs to motor nerves. 

Autonomic Nerves

  • Involuntary or semi-voluntary functions are controlled by autonomic nerves.  As a result, damage to these nerves can result in the following: impotence, nausea or vomiting after meals, abdominal bloating, diarrhea, constipation, decreased ability to sweat, blurred vision, dizziness, incomplete bladder emptying, and/or loss of bladder control.

Diagnosis

Your doctor will take a complete medical history and perform a physical examination.

The patient history will include symptoms, social habits, exposure to any toxins, risks of infectious disease, work environment and any family history of neurological disease.

The physical examination may include testing of light touch, reflexes, body position, vibration, pain, and temperature.  Comparing blood pressures in the sitting and standing position may also provide important information.

Additional Testing

  • lumbar puncture - examination of cerebrospinal fluid that surrounds the brain and spinal cord may reveal abnormalities; 
  • blood tests to check vitamin B-12 levels, folate levels, thyroid function, fasting glucose, etc.; 
  • electromyograph (EMG), a recording of electrical activity in muscles;
  • nerve conduction velocity (NVC) tests;
  • nerve biopsy; and
  • skin biopsy.

Treatments

  • Correct vitamin deficiencies.
  • Correct blood glucose levels in diabetes as strict control of blood glucose levels can lessen further nerve damage and reduce neuropathic symptoms. 
  • Treat bacterial infections such as Lyme disease.
  • Treat nerve compressions with physical therapy, injections or surgery.
  • Treat autoimmune conditions with immunosuppressant drugs, plasmapheresis, high doses of immunoglobulins.
  • Avoid exposure to toxic chemicals.
  • Avoid repetitive movements which are contributing to nerve damage.
  • Minimize or eliminate alcohol consumption.
  • Use dialysis in kidney failure.
  • Immediately treat patients with shingles using antiviral medication and sympathetic nerve blocks to prevent post-herpetic neuralgia.
  • Foot braces can allow nerves to heal when a foot drop is present.

Pain Management

  • acetaminophen (Tylenol), but avoid if you have a history of liver disease or kidney disease; 
  • non-steroidal anti-inflammatory medications (ibuprofen, aspirin, naprosyn, etc.), but avoid if you have a history of gastritis, peptic ulcer disease, or kidney disease;
  • tricyclic antidepressants such as amitriptyline (Elavil) and nortriptyline (Pamelor);
  • anti-seizure medication such as gabapentin (Neurontin); 
  • topical lidocaine patches;
  • capsaicin cream;
  • pregabalin (Lyrica);
  • duloxetine (Cymbalta);
  • careful footcare and wound care in people with diabetes;
  • wrist braces to alleviate nerve compression in carpal tunnel syndrome;
  • surgical release of ligaments, tendons, muscles or bones to relieve nerve entrapment;
  • cold laser therapy; and
  • spinal cord stimulation.

Jose Veliz MD is the medical director of Palomar Spine & Pain, in Escondido, CA (North San Diego County).

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