Diabetic neuropathy is a common complication of diabetes mellitus in which nerves are damaged as a result of hyperglycemia (high blood sugar levels).

People with diabetes commonly develop temporary or permanent damage to nerve tissue. Nerve injuries are caused by decreased blood flow and high blood-sugar levels, and are more likely to develop if blood-glucose levels are poorly controlled.

Some diabetics will not develop nerve damage, while others may develop this condition relatively early. On average, the onset of symptoms occurs 10 to 20 years after diabetes has been diagnosed. Approximately 50% of people with diabetes will eventually develop nerve damage.

Peripheral nerve injuries may affect cranial nerves or nerves from the spinal column and their branches. This type of neuropathy (nerve injury) tends to develop in stages. Early on, intermittent pain and tingling is noted in the extremities, particularly the feet. In later stages, the pain is more intense and constant. Finally, a painless neuropathy develops when pain sensation is lost to an area. This greatly increases the risk of severe tissue injury because pain no longer alerts the person to injury.

Autonomic neuropathies affect the nerves that regulate involuntary vital functions, including the heart muscle, smooth muscles and glands. Low blood pressure, diarrhea, constipation, sexual impotence, and other symptoms can be caused by autonomic neuropathies.

• Numbness
• Tingling
• Decreased sensation to a body part
• Loss of sensation to a body part or area
• Diarrhea
• Constipation
• Loss of bladder control
• Impotence
• Facial drooping
• Drooping eyelid
• Drooping mouth
• Vision changes
• Dizziness
• Weakness
• Swallowing difficulty
• Speech impairment
• Muscle contractions

Note: Symptoms vary depending on the nerve(s) affected and may include symptoms other than those listed. Symptoms usually develop gradually over years.

Physical examination, including neurological and sensory tests, may reveal many neuropathies. A common early finding is the absence of ankle reflexes.

The goals of treating diabetic neuropathy are to prevent progression and reduce the symptoms of the disease. Tight control of glucose is important to prevent progression. To reduce the symptoms, topical treatment with Capsaicin or oral medication like amitriptyline, gabapentin, and carbamazepine have been used successfully. Analgesics (pain medications) may work for some patients on a short-term basis. But, in most cases, they usually do not provide much benefit.

Regular foot exams are important to identify small infections and prevent progression. If foot injuries go unnoticed for too long, amputation may be required.

The mechanisms of diabetic neuropathy are poorly understood. At present, treatment alleviates pain and can control some associated symptoms, but the process is generally progressive.

There is an increased risk of injury to the feet because of loss of sensation. Small infections can progress to ulceration (skin and soft tissue breakdown) and require amputation. In addition, motor nerve damage can lead to muscle breakdown and imbalance.

Call your health care provider if signs and symptoms of diabetic neuropathy develop.

It is clear now that tight control of blood sugar level (Hemoglobin A1C < 7.0) prevents the development of neuropathy in 60% of type 1 diabetics and decreases the severity of symptoms. In addition, regular foot care can prevent a small infection from progressing.

Vinik AI. Diabetic neuropathies. Med Clin North Am. 2004; 88(4): 947-99.