Diabetic neuropathy is a nerve disorder caused by diabetes mellitus. Diabetic neuropathy may be diffuse, affecting several parts of the body, or focal, affecting a specific nerve and part of the body.
The nervous system consists of two major divisions: the central nervous systems (CNS) which includes the brain, the cranial nerves, and the spinal cord, and the peripheral nervous system (PNS) which includes the nerves that link the CNS with the sensory organs, muscles, blood vessels, and glands of the body. These peripheral nerves are either motor, meaning that they are involved in motor activity such as walking, or sensory, meaning that they carry sensory information back to the CNS. The PNS also works with the CNS to regulate involuntary (autonomic) processes such as breathing, heartbeat, blood pressure, etc.
There are two types of diffuse diabetic neuropathy that affect different nervous system functions. Diffuse peripheral neuropathy primarily affects the limbs, damaging the nerves of the feet and hands. Autonomic neuropathy is the other form of diffuse neuropathy and it affects the heart and other internal organs.
Focal—or localized—diabetic neuropathy affects specific nerves, most commonly in the torso, leg, or head.
Diabetic neuropathy can lead to muscular weakness, loss of feeling or sensation, and loss of autonomic functions such as digestion, erection, bladder control, and sweating among others.
The longer a person has diabetes, the more likely the development of one or more forms of neuropathy. Approximately 60-70% of patients with diabetes have neuropathy, but only about 5% will experience painful symptoms.
Causes and symptoms
The exact cause of diabetic neuropathy is not known. Researchers believe that the process of nerve damage is related to high glucose concentrations in the blood that could cause chemical changes in nerves, disrupting their ability to effectively send messages. High blood glucose is also known to damage the blood vessels that carry oxygen and other nutrients to the nerves. In addition, some people may have a genetic predisposition to develop neuropathy.
There is a wide range of symptoms associated with diabetic neuropathy, and they depend on which nerves and parts of the body are affected and also on the type of neuropathy present. Some patients have very mild symptoms, while others are severely disabled.
Common symptoms of diffuse peripheral neuropathy include:
- numbness and feelings of tingling or burning
- insensitivity to pain
- needle-like jabs of pain
- extreme sensitivity to touch
- loss of balance and coordination
Common symptoms of diffuse autonomic neuropathy include:
- impaired urination and sexual function
- bladder infections
- stomach disorders, due to the impaired ability of the stomach to empty (gastric stasis)
- nausea, vomiting and bloating
- dizziness, lightheadedness, and fainting spells
- loss of appetite
Common symptoms of focal neuropathy include:
- pain in the front of a thigh
- severe pain in the lower back
- pain in the chest or stomach
- ache behind an eye
- double vision
- paralysis on one side of the face
In severe diabetic neuropathy loss of sensation can lead to injuries that are unnoticed, progressing to infections, ulceration and possibly amputation.
The diagnosis of neuropathy is based on the symptoms that present during a physical exam. Pain assessment is usually the first step. Patients may have more than one type of pain, and the history helps the doctor determine whether a the pain has a neuropathic cause.
The exam may include:
- a screening test for lost sensation
- nerve conduction studies to check the flow of electric current through a nerve
- electromyography (EMG) to see how well muscles respond to electrical impulses transmitted by nearby nerves.
- ultrasound to show how the bladder and other parts of the urinary tract are functioning
- sometimes a nerve biopsy may be performed.
Specialists who treat diabetic neuropathy include:
- neurologists: specialists in nervous system disorders
- urologists: specialists in urinary tract disorder
- gastroenterologists: specialists in digestive disorders
- podiatrists: specialists in caring for the feet
Treatment of diabetic neuropathy is usually focused on treating the symptoms associated with the neuropathy and addressing the underlying cause by improving the control of blood sugar levels, which may heal the early stages of neuropathy.
There is no cure for the permanent nerve damage caused by neuropathy. To help control pain, the choice of proven drug therapies has broadened during the past decade. Pain medication, such as the topical skin cream capsaicin, is usually no stronger than codeine because of the potential for addiction with long-term use of such drugs. Four main classes of drugs are available for pain management, alone or in combination: tricyclic antidepressants (Imipramine, Nortriptyline), narcotic analgesics (Morphine), anticonvulsants (Carbamazepine, Gabapentin), and antiarrhythmics.
Central nervous system (CNS)— Part of the nervous system consisting of the brain, cranial nerves, and spinal cord. The brain is the center of higher processes, such as thought and emotion, and is responsible for the coordination and control of bodily activities and the interpretation of information from the senses. The cranial nerves and spinal cord link the brain to the peripheral nervous system.
Diabetes mellitus— Disease characterized by the inability of the body to produce or respond properly to insulin, required by the body to convert glucose to energy.
Glucose— The type of sugar found in the blood.
Peripheral nervous system (PNS)— One of the two major divisions of the nervous system. PNS nerves link the central nervous system with sensory organs, muscles, blood vessels, and glands.
Early stage diabetic neuropathy can usually be reversed with good glucose control. Once nerve damage has occurred it cannot be reversed. The prognosis is largely dependent on the management of the underlying condition, diabetes, which may halt the progression of the neuropathy and improve symptoms. Recovery, if it occurs, is slow.
Tight glucose control and the avoidance of alcohol and cigarettes help protect nerves from damage.
American Diabetes Association. 1701 North Beauregard Street, Alexandria, VA 22311. (800) DIABETES (800-342-2383). 〈http://www.diabetes.org/〉.
Juvenile Diabetes Foundation. 120 Wall St., 19th Floor, New York, NY 10005. (800) 533-CURE. 〈http://www.jdf.org/〉.
Diabetic neuropathy is nerve damage caused by diabetes.
Diabetic neuropathy is a common complication of diabetes mellitus . The most common type of nerve damage associated with diabetes is known as peripheral neuropathy because it is a loss of sensation and strength in the hands and feet. Diabetic neuropathy can also affect the nerves that control body functions such as heart rate and digestion. This type of nerve damage is called autonomic neuropathy.
Distal symmetric polyneuropathy is another type of diabetic neuropathy. About 40% of people who have had diabetes for 25 years or longer have this neuropathy, which usually develops in the feet. Pain or pins-and-needles, burning, crawling, or prickling sensations are felt in the feet and lower leg areas that stockings normally cover.
Diabetic neuropathy develops over time as a result of uncontrolled high blood sugar levels. About half of all people with diabetes develop diabetic neuropathy, which ranges from mild to severe. It is more common among people with diabetes who do not control their blood sugar very well than among those who maintain good control. Men are more likely to develop diabetic neuropathy than women.
Causes and symptoms
When nerves are damaged, their ability to convey messages to the brain and other parts of the body is greatly diminished. The nerve damage occurs gradually over time, and is caused by high blood sugar levels and decreased blood flow.
Many people who have peripheral neuropathy do not notice any symptoms initially. When detected, the symptoms of neuropathy generally relate to the type of affected nerve. If a sensory nerve is damaged, then common symptoms include numbness, tingling in the area, a prickling sensation, or pain. Pain associated with neuropathy can be quite intense and may be described as cutting, stabbing, crushing, or burning. In some cases, any stimulus, even the lightest touch, may be perceived as excruciating, or pain may be felt even in the absence of a stimulus. Damage to a motor nerve is usually indicated by weakness in the affected area. If the problem with the motor nerve persists, then atrophy (muscle wasting) or lack of muscle tone may occur.
Among those who experience symptoms, the most frequently occurring symptom is numbness in the fingers and toes. Other symptoms of peripheral neuropathy include:
- tingling, discomfort or pain in the fingers and toes
- loss of feeling in the hands or feet
- sharp pains or deep aches that interfere with sleep and normal activities of daily living
- heightened sensitivity such that the slightest touch is perceived as painful
- balance problems, nighttime falls and slowed reflexes
Symptoms of autonomic neuropathy include:
- low blood pressure and dizziness when quickly rising from sitting or lying down
- balance problems
- rapid or irregular heartbeats
- bloating, nausea, vomiting, constipation or diarrhea
- difficulty swallowing
- erectile dysfunction—difficulty achieving and maintaining an erection
- dry skin, calluses, reddened areas, hair loss on limbs
QUESTIONS TO ASK YOUR DOCTOR
- What can be done to avoid diabetic neuropathy?
- How do I know if I have diabetic neuropathy?
- What happens when the nerves in the legs and arms are damaged?
- How can I prevent foot problems that can result from diabetic neuropathy?
During the medical history and physical examination, the physician obtains detailed information about the location, nature, and duration of symptoms to pinpoint the actual problem or exclude specific potential causes of the neuropathy. The diagnosis of diabetic neuropathy is made on the basis of a thorough medical history, a focused physical examination and diagnostic testing which may include:
- measuring blood pressure while standing and lying down
- listening to the heart and checking pulses in the legs and feet
- examining the skin for changes such as hair loss on the arms and legs, calluses, and red areas, especially between the toes
- examination of the feet for skin changes, loss of arch height or hammer toes
- evaluation of sensation and motor strength
- assessment of heart rate and function using an electrocardiograph (ECG) and other tests
Addressing the underlying cause of the neuropathy can prevent further nerve damage and may allow for some recovery. Gaining and maintaining tight control of blood sugar levels may delay the development of diabetic neuropathies and slow their progression.
Many different drugs may be prescribed to relieve the pain associated with diabetic neuropathy. Over-the-counter (nonprescription) analgesics such as aspirin , acetaminophen and non-steroidal anti-inflammatory drugs (NSAIDs) and prescription pain relievers such as tramadol may be prescribed. Other prescription medications used to relieve pain include:
- tricyclic antidepressants, such as amitriptyline or doxepin
- duloxetine, an antidepressant that inhibits reuptake of the neurotransmitters serotonin and norepinephrine
- pregabilin, gabapentin and valproate, which are anti-convulsant drugs that inhibit certain nerve impulses and thus, may reduce pain
- topical preparations such as creams and patches containing lidocaine (a substance used to relieve pain by blocking signals at the nerve endings in skin) or capsaicin (the active component of hot chili peppers), which are applied directly to the skin over the affected area
Exercise and physical therapy are recommended to combat muscle weakness, prevent atrophy and to strengthen muscles that have not yet weakened. Persons with significant muscle weakness may be given splints or other supportive devices.
When diabetic neuropathy affects the autonomic nervous system, drugs may be prescribed to regulate blood pressure , bladder and bowel functions. Since diabetic neuropathy may impair erectile function, some male patients may be prescribed phosphodiesterase type 5 (PDE-5) drugs such as sildenafil, vardenifil and tadalafil to improve the ability to have and sustain an erection.
There is no single diet that meets the nutritional needs of all persons with diabetes. People with diabetes are often advised to consult with a professional dietician or nutritionist to design a diet customized to their health needs and preferences.
In general, the goals of a diet for persons with diabetes are to:
- achieve and maintain normal or near-normal blood glucose (sugar) levels
- support maintenance of healthy blood pressure and avoid high blood pressure
- achieve and maintain healthy blood lipid (cholesterol and triglyceride) levels
- achieve and maintain a healthy weight and prevent obesity
Autonomic nerves —The part of the nervous system that regulates involuntary functions of organs such as the heart, bladder and bowel.
Gangrene —Death of tissue, frequently caused by a loss of blood flow or wounds that cannot heal, especially in the legs and feet.
Neuropathy —Disease or disorder of nerves.
Peripheral nerves —The nerves that carry information to and from the brain and spinal cord and from all other parts of the body.
Polyneuropathy —A generalized disorder of peripheral nerves.
There is no cure for diabetic neuropathy. Stringent control of blood sugar helps to prevent neuropathy and may help to slow its progress. Left untreated, diabetic neuropathy may promote the development of foot ulcers, which in turn can lead to gangrene and limb loss. Diabetic neuropathy increases the risk of amputation .
Maintaining good control of blood sugar and blood pressure, not smoking and limiting alcohol consumption can help to prevent, delay or slow the progress of diabetic neuropathy. Daily inspection of the feet for dry or cracking skin and prompt foot care are vitally important for preventing complications of diabetic neuropathy. Attentive foot care can help prevent ulceration, infection, and amputation.
All persons with diabetes should be screened for nerve damage by a health professional in an examination that includes a comprehensive foot exam. People with diabetes who have loss of sensation in their feet should have a foot exam every 3 to 6 months to check for ulcers or signs of infections.
People with diabetic neuropathy may be unable to feel heat or other sharp or painful sensations. It is vitally important that they take precautions to avoid such injuries. Examples include wearing protective footwear, even indoors, and maintaining vigilance to avoid burns, cuts, scrapes or other injuries.
Proper foot care is important. Along with checking for injuries on the feet and lower legs, care must be taken when trimming toenails. Skin changes, such as redness, blisters, sores or other wounds should be promptly treated by a health professional.
Kronenberg, H. M., S. Melmed, K. S. Polonsky, and P. R. Larsen. Kronenberg: Williams Textbook of Endocrinology, 11th ed. Philadelphia: Saunders, an imprint of Elsevier, 2008.
Aring, Ann M., David E. Jones, and James M. Falko. “Evaluation and Prevention of Diabetic Neuropathy.” American Family Physician 71, no. 11 (June 1, 2005):2123–8.
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), 31 Center Drive, MSC 2560?, Bethesda, MD, 20892-2560, (301) 496-3583, http://www2.niddk.nih.gov/.
Barbara Wexler MPH