Metabolic neuropathies

Causes, incidence, and risk factors

Nerve damage can be caused by many different things. Metabolic neuropathy may be caused by:

• A problem with the body's ability to use energy,  often due to a nutritional deficiency
• Dangerous substances (toxins) build up in the body

Diabetes is one of the most common causes of metabolic neuropathies. People who are at the highest risk of nerve damage from diabetes include:

• Those with damage to the kidneys or eyes
• Those with poorly controlled blood sugar

Other common metabolic causes of neuropathies include:

• Alcoholism
• Low blood sugar (hypoglycemia )
• Kidney failure
• Porphyria
• Severe infection throughout the body (sepsis )
• Thyroid disease
• Vitamin deficiencies (including vitamins B12 , E , and B1 )

Some metabolic disorders are passed down through families (inherited), while others develop due to various diseases.

Symptoms

These symptoms occur because nerves cannot send proper signals to and from your brain:

• Difficulty feeling in any area of the body
• Difficulty swallowing
• Difficulty using the arms or hands
• Difficulty using the legs or feet
• Difficulty walking
• Pain, burning, pins and needles, or shooting pains in any area of the body (nerve pain)
• Weakness in the face, arms, legs, or other area of the body

Usually, these symptoms start in the toes and feet and move up the legs, eventually affecting the hands and arms.

Signs and tests

An exam may show:

• Decreased feeling (may affect touch, pain, vibration, or position sensation)
• Reduced reflexes (most common in the ankle)
• Muscles becoming smaller (atrophy)
• Muscle twitches (fasciculations)
• Muscle weakness
• Loss of movement (paralysis)

Tests used to detect most metabolic neuropathies:

• Blood tests
• Electrical test of the muscles (EMG )
• Electrical test of nerve conduction

Treatment

For most metabolic neuropathies, the best treatment is to correct the metabolic problem.

Vitamin deficiencies are treated with diet or injections. Abnormal blood sugar or thyroid function may need medication to correct the problem. Alcoholic neuropathy is treated with alcohol abstinence.

In some cases, pain is treated with medications that reduce abnormal pain signals from the nerves (duloxetine, gabapentin, pregabalin). Lotions, creams, or medicated patches can provide relief in some cases.

Clinical trials of new medications include antioxidants, neuroprotectants, insulin-like drugs, and aldose reductase inhibitors.

Weakness is often treated with physical therapy. You may need to learn how to use a cane or walker if your balance is affected. You may need special braces on the ankles to walk better.

Support Groups

For additional information and support, see www.neuropathy.org and http://diabetes.niddk.nih.gov/DM/pubs/neuropathies .

Expectations (prognosis)

The outlook mainly depends on the cause of the disorder. In some cases, the problem can easily be treated. In other cases, the metabolic problem cannot be controlled and nerves may continue to become damaged.

Complications

• Deformity
• Injury to feet
• Numbness
• Pain
• Trouble walking
• Weakness

Prevention

Maintaining a healthy lifestyle can reduce the risk of neuropathy.

• Avoid excess alcohol use.
• Eat a balanced diet.
• Visit the doctor regularly to find metabolic disorders before neuropathy develops.

If you already have a metabolic problem, regular doctor visits can help control the problem and reduce the chance of further nerve damage.

Patients who already have metabolic neuropathy can reduce the risk of some complications. A foot doctor (podiatrist) can teach you how to inspect your feet for signs of injury and infection. Proper fitting shoes can lessen the chance of skin breakdown in sensitive areas of the feet.

References

Shy ME. Peripheral neuropathies. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 446.

Montfort EG, Witte A, Ward K. Neuropathic Pain: A Review of Diabetic Neuropathy. US Pharm. 2010;35(5):HS8-HS15.