Dr. MJ Bazos MD,
Neuropathy: The Nerve Damage of Diabetes
What Is Diabetic Neuropathy?
Diabetic neuropathy is a nerve
disorder caused by diabetes. Symptoms of neuropathy include numbness and
sometimes pain in the hands, feet, or legs. Nerve damage caused by diabetes can
also lead to problems with internal organs such as the digestive tract, heart,
and sexual organs causing indigestion, diarrhea or constipation, dizziness,
bladder infections, and impotence. In some cases, neuropathy can flare up
suddenly, causing weakness and weight loss. Depression may follow. While some
treatments are available, a great deal of research is still needed to understand
how diabetes affects the nerves and to find more effective treatments for this
Neuropathy Be Prevented?
clinical study that involved 1,441 volunteers with insulin-dependent diabetes
(IDDM) was recently completed by the National Institute of Diabetes and
Digestive and Kidney Diseases. The study proved that keeping blood sugar levels
as close to the normal range as possible slows the onset and progression of
nerve disease caused by diabetes. The Diabetes Control and Complications Trial
(DCCT) studied two groups of volunteers: those who followed a standard diabetes
management routine and those who intensively managed their diabetes. Persons in
the intensive management group took multiple injections of insulin daily or used
an insulin pump and monitored their blood glucose at least four times a day to
try to lower their blood glucose levels to the normal range. After 5 years,
tests of neurological function showed that the risk of nerve damage was reduced
by 60% in the intensively managed group. People in the standard treatment group,
whose average blood glucose levels were higher, had higher rates of neuropathy.
Although the DCCT included only patients with IDDM, researchers believe that
people with noninsulin-dependent diabetes would also benefit from maintaining
lower levels of blood glucose.
Common Is Diabetic Neuropathy?
with diabetes can develop nerve problems at any time. Significant clinical
neuropathy can develop within the first 10 years after diagnosis of diabetes and
the risk of developing neuropathy increases the longer a person has diabetes.
Some recent studies have reported that:
•60% of patients with diabetes have some
form of neuropathy, but in most cases (30 to 40%), there are no symptoms.
•30 to 40% of patients with diabetes have
symptoms suggesting neuropathy, compared with 10% of people without diabetes.
Diabetic neuropathy appears to be more
common in smokers, people over 40 years of age, and those who have had problems
controlling their blood glucose levels.
What Causes Diabetic Neuropathy?
Scientists do not know what causes
diabetic neuropathy, but several factors are likely to contribute to the
disorder. High blood glucose, a condition associated with diabetes, causes
chemical changes in nerves. These changes impair the nerves' ability to transmit
signals. High blood glucose also damages blood vessels that carry oxygen and
nutrients to the nerves. In addition, inherited factors probably unrelated to
diabetes may make some people more susceptible to nerve disease than others.
How high blood glucose leads to nerve
damage is a subject of intense research. The precise mechanism is not known.
Researchers have discovered that high glucose levels affect many metabolic
pathways in the nerves, leading to an accumulation of a sugar called sorbitol
and depletion of a substance called myoinositol. However, studies in humans have
not shown convincingly that these changes are the mechanism that causes nerve
More recently, researchers
have focused on the effects of excessive glucose metabolism on the amount of
nitric oxide in nerves. Nitric oxide dilates blood vessels. In a person with
diabetes, low levels of nitric oxide may lead to constriction of blood vessels
supplying the nerve, contributing to nerve damage. Another promising area of
research centers on the effect of high glucose attaching to proteins, altering
the structure and function of the proteins and affecting vascular function.
Scientists are studying how these
changes occur, how they are connected, how they cause nerve damage, and how to
prevent and treat damage.
the Symptoms of Diabetic Neuropathy?
The symptoms of diabetic neuropathy
vary. Numbness and tingling in feet are often the first sign. Some people notice
no symptoms, while others are severely disabled. Neuropathy may cause both pain
and insensitivity to pain in the same person. Often, symptoms are slight at
first, and since most nerve damage occurs over a period of years, mild cases may
go unnoticed for a long time. In some people, mainly those afflicted by focal
neuropathy, the onset of pain may be sudden and severe.
What Are the Major Types of
The symptoms of neuropathy
also depend on which nerves and what part of the body is affected. Neuropathy
may be diffuse, affecting many parts of the body, or focal, affecting a single,
specific nerve and part of the body.
The two categories of diffuse
neuropathy are peripheral neuropathy affecting the feet and hands and autonomic
neuropathy affecting the internal organs.
Peripheral Neuropathy. The most
common type of peripheral neuropathy damages the nerves of the limbs, especially
the feet. Nerves on both sides of the body are affected. Common symptoms of this
kind of neuropathy are:
- Numbness or insensitivity to pain or temperature
- Tingling, burning, or prickling
- Sharp pains or cramps
- Extreme sensitivity to touch, even light touch
- Loss of balance and coordination.
These symptoms are often worse
The damage to nerves often
results in loss of reflexes and muscle weakness. The foot often becomes wider
and shorter, the gait changes, and foot ulcers appear as pressure is put on
parts of the foot that are less protected. Because of the loss of sensation,
injuries may go unnoticed and often become infected. If ulcers or foot injuries
are not treated in time, the infection may involve the bone and require
amputation. However, problems caused by minor injuries can usually be controlled
if they are caught in time. Avoiding foot injury by wearing well-fitted shoes
and examining the feet daily can help prevent amputations.
Autonomic Neuropathy (also called
visceral neuropathy) Autonomic neuropathy is another form of diffuse
neuropathy. It affects the nerves that serve the heart and internal organs and
produces changes in many processes and systems.
Urination and Sexual Response
Autonomic neuropathy most often affects the organs that control urination and
sexual function. Nerve damage can prevent the bladder from emptying completely,
so bacteria grow more easily in the urinary tract (bladder and kidneys). When
the nerves of the bladder are damaged, a person may have difficulty knowing when
the bladder is full or controlling it, resulting in urinary incontinence.
The nerve damage and circulatory
problems of diabetes can also lead to a gradual loss of sexual response in both
men and women, although sex drive is unchanged. A man may be unable to have
erections or may reach sexual climax without ejaculating normally.
Digestion. Autonomic neuropathy
can affect digestion. Nerve damage can cause the stomach to empty too slowly, a
disorder called gastric stasis. When the condition is severe (gastroparesis), a
person can have persistent nausea and vomiting, bloating, and loss of appetite.
Blood glucose levels tend to fluctuate greatly with this condition.
If nerves in the esophagus are
involved, swallowing may be difficult. Nerve damage to the bowels can cause
constipation or frequent diarrhea, especially at night. Problems with the
digestive system often lead to weight loss.
Autonomic neuropathy can affect the cardiovascular system, which controls
the circulation of blood throughout the body. Damage to this system interferes
with the nerve impulses from various parts of the body that signal the need for
blood and regulate blood pressure and heart rate. As a result, blood pressure
may drop sharply after sitting or standing, causing a person to feel dizzy or
light-headed, or even to faint (orthostatic hypotension).
Neuropathy that affects the
cardiovascular system may also affect the perception of pain from heart disease.
People may not experience angina as a warning sign of heart disease or may
suffer painless heart attacks. It may also raise the risk of a heart attack
during general anesthesia.
neuropathy can hinder the body's normal response to low blood sugar or
hypoglycemia, which makes it difficult to recognize and treat an insulin
neuropathy can affect the nerves that control sweating. Sometimes, nerve damage
interferes with the activity of the sweat glands, making it difficult for the
body to regulate its temperature. Other times, the result can be profuse
sweating at night or while eating (gustatory sweating).
Focal Neuropathy (Including
diabetic neuropathy appears suddenly and affects specific nerves, most often in
the torso, leg, or head. Focal neuropathy may cause:
- Pain in the front of a thigh
- Severe pain in the lower back or pelvis
- Pain in the chest, stomach, or flank
- Chest or abdominal pain sometimes mistaken for
angina, heart attack, or appendicitis
- Aching behind an eye
- Inability to focus the eye
- Double vision
- Paralysis on one side of the face (Bell's palsy)
- Problems with hearing.
This kind of neuropathy is
unpredictable and occurs most often in older people who have mild diabetes.
Although focal neuropathy can be painful, it tends to improve by itself after a
period of weeks or months without causing long-term damage.
People with diabetes are also prone to
developing compression neuropathies. The most common form of compression
neuropathy is carpal tunnel syndrome. Asymptomatic carpal tunnel syndrome occurs
in 20 to 30% of people with diabetes, and symptomatic carpal tunnel syndrome
occurs in 6 to 11%. Numbness and tingling of the hand are the most common
Muscle weakness may also
Parts of the Body Affected
by Diabetic Neuropathy
- Digestive System
- Sexual organs
- Urinary tract
- Sweat glands
- Facial muscles
- Pelvis and lower back
How Do Doctors Diagnose
diagnoses neuropathy based on symptoms and a physical exam. During the exam, the
doctor may check muscle strength, reflexes, and sensitivity to position,
vibration, temperature, and light touch. Sometimes special tests are also used
to help determine the cause of symptoms and to suggest treatment.
A simple screening test to check point
sensation in the feet can be done in the doctor's office. The test uses a nylon
filament mounted on a small wand. The filament delivers a standardized 10-gram
force when touched to areas of the foot. Patients who cannot sense pressure from
the filament have lost protective sensation and are at risk for developing
neuropathic foot ulcers.
conduction studies check the flow of electrical current through a nerve. With
this test, an image of the nerve impulse is projected on a screen as it
transmits an electrical signal. Impulses that seem slower or weaker than usual
indicate possible damage to the nerve. This test allows the doctor to assess the
condition of all the nerves in the arms and legs.
Electromyography (EMG) is used to see
how well muscles respond to electrical impulses transmitted by nearby nerves.
The electrical activity of the muscle is displayed on a screen. A response that
is slower or weaker than usual suggests damage to the nerve or muscle. This test
is often done at the same time as nerve conduction studies.
Ultrasound employs sound waves. The
sound waves are too high to hear, but they produce an image showing how well the
bladder and other parts of the urinary tract are functioning.
Nerve biopsy involves removing a
sample of nerve tissue for examination. This test is most often used in research
If your doctor suspects
autonomic neuropathy, you may also be referred to a physician who specializes in
digestive disorders (gastroenterologist) for additional tests.
How Is Diabetic Neuropathy Usually
Treatment aims to relieve
discomfort and prevent further tissue damage. The first step is to bring blood
sugar under control by diet and oral drugs or insulin injections, if needed, and
by careful monitoring of blood sugar levels. Although symptoms can sometimes
worsen at first as blood sugar is brought under control, maintaining lower blood
sugar levels helps reverse the pain or loss of sensation that neuropathy can
cause. Good control of blood sugar may also help prevent or delay the onset of
part of treatment involves special care of the feet, which are prone to
A number of medications and
other approaches are used to relieve the symptoms of diabetic neuropathy.
Relief of Pain
For, burning, tingling, or numbness,
the doctor may suggest an analgesic such as aspirin or acetaminophen or
anti-inflammatory drugs containing ibuprofen. Nonsteroidal anti-inflammatory
drugs should be used with caution in people with renal disease. Antidepressant
medications such as amitriptyline (sometimes used with fluphenazine) or nerve
medications such as carbamazepine or phenytoin sodium may be helpful. Codeine is
sometimes prescribed for short-term use to relieve severe pain. In addition, a
topical cream, capsaicin, is now available to help relieve the pain of
The doctor may also prescribe
a therapy known as transcutaneous electronic nerve stimulations (TENS). In this
treatment, small amounts of electricity block pain signals as they pass through
a patient's skin. Other treatments include hypnosis, relaxation training,
biofeedback, and acupuncture. Some people find that walking regularly or using
elastic stockings helps relieve leg pain. Warm (not hot) baths, massage, or an
analgesic ointment such as Ben Gay may also help.
Indigestion, belching, nausea, or
vomiting are symptoms of gastroparesis. For patients with mild symptoms of slow
stomach emptying, doctors suggest eating small, frequent meals and avoiding
fats. Eating less fiber may also relieve symptoms. For patients with severe
gastroparesis, the doctor may prescribe metoclopramide, which speeds digestion
and helps relieve nausea. Other drugs that help regulate digestion or reduce
stomach acid secretion may also be used or erythromycin may be prescribed. In
each case, the potential benefits of these drugs need to be weighed against
their side effects.
diarrhea or other bowel problems, antibiotics or clonidine HCl, a drug used to
treat high blood pressure, are sometimes prescribed. The antibiotic tetracycline
may be prescribed. A wheat-free diet may also bring relief since the gluten in
flour sometimes causes diarrhea.
Neurological problems affecting the
urinary tract can result in infections or incontinence. The doctor may prescribe
an antibiotic to clear up an infection and suggest drinking more fluids to
prevent further infections. If incontinence is a problem, patients may be
advised to urinate at regular times (every 3 hours, for example) since they may
not be able to tell when the bladder is full.
Sitting or standing slowly may help
prevent light-headedness, dizziness, or fainting, which are symptoms that may be
associated with some forms of autonomic neuropathy. Raising the head of the bed
and wearing elastic stockings may also help. Increased salt in the diet and
treatment with salt-retaining hormones such as fludrocortisone are other
possible approaches. In certain patients, drugs used to treat hypertension can
instead raise blood pressure, although predicting which patients will have this
paradoxical reaction is difficult.
Muscle weakness or loss of
coordination caused by diabetic neuropathy can often be helped by physical
Urinary and Sexual
Nerve and circulatory
problems of diabetes can disrupt normal male sexual function, resulting in
impotence. After ruling out a hormonal cause of impotence, the doctor can
provide information about methods available to treat impotence caused by
neuropathy. Short-term solutions involve using a mechanical vacuum device or
injecting a drug called a vasodilator into the penis before sex. Both methods
raise blood flow to the penis, making it easier to have and maintain an
erection. Surgical procedures, in which an inflatable or semirigid device is
implanted in the penis, offer a more permanent solution. For some people,
counseling may help relieve the stress caused by neuropathy and thereby help
restore sexual function.
In women who
feel their sexual life is not satisfactory, the role of diabetic neuropathy is
less clear. Illness, vaginal or urinary tract infections, and anxiety about
pregnancy complicated by diabetes can interfere with a woman's ability to enjoy
intimacy. Infections can be reduced by good blood glucose control. Counseling
may also help a woman identify and cope with sexual concerns.
Why Is Good Foot Care Important for
People with Diabetic Neuropathy?
People with diabetes need to take
special care of their feet. Neuropathy and blood vessel disease both increase
the risk of foot ulcers. The nerves to the feet are the longest in the body, and
are most often affected by neuropathy. Because of the loss of sensation caused
by neuropathy, sores or injuries to the feet may not be noticed and may become
At least 15% of all people
with diabetes eventually have a foot ulcer, and 6 of every 1,000 people with
diabetes have an amputation. However, doctors estimate that nearly three
quarters of all amputations caused by neuropathy and poor circulation could be
prevented with careful foot care.
prevent foot problems from developing, people with diabetes should follow these
rules for foot care:
- Check your feet and toes daily for any cuts,
sores, bruises, bumps, or infections–using a mirror if necessary.
- Wash your feet daily, using warm (not hot) water
and a mild soap. If you have neuropathy, you should test the water temperature
with your wrist before putting your feet in the water. Doctors do not advise
soaking your feet for long periods, since you may lose protective calluses. Dry
your feet carefully with a soft towel, especially between the toes.
- Cover your feet (except for the skin between the
toes) with petroleum jelly, a lotion containing lanolin, or cold cream before
putting on shoes and socks. In people with diabetes, the feet tend to sweat less
than normal. Using a moisturizer helps prevent dry, cracked skin.
- Wear thick, soft socks and avoid wearing slippery
stockings, mended stockings, or stockings with seams.
- Wear shoes that fit your feet well and allow your
toes to move. Break in new shoes gradually, wearing them for only an hour at a
time at first. After years of neuropathy, as reflexes are lost, the feet are
likely to become wider and flatter. If you have difficulty finding shoes that
fit, ask your doctor to refer you to a specialist, called a pedorthist, who can
provide you with corrective shoes or inserts.
- Examine your shoes before putting them on to make
sure they have no tears, sharp edges, or objects in them that might injure your
- Never go barefoot, especially on the beach, hot
sand, or rocks.
- Cut your toenails straight across, but be careful
not to leave any sharp corners that could cut the next toe.
- Use an emery board or pumice stone to file away
dead skin, but do not remove calluses, which act as protective padding. Do not
try to cut off any growths yourself, and avoid using harsh chemicals such as
wart remover on your feet.
- Test the water temperature with your elbow before
stepping in a bath.
- If your feet are cold at night wear socks. (Do
not use heating pads or hot water bottles.)
- Avoid sitting with your legs crossed. Crossing
your legs can reduce the flow of blood to the feet.
- Ask your doctor to check your feet at every
visit, and call your doctor if you notice that a sore is not healing well.
- If you are not able to take care of your own
feet, ask your doctor to recommend a podiatrist (specialist in the care and
treatment of feet) who can help.
Are There Any
Experimental Treatments for Diabetic Neuropathy?
Several new drugs under study may
eventually prevent or reverse diabetic neuropathy. However, extensive testing is
required by the U.S. Food and Drug Administration to establish the safety and
efficacy of drugs before they are approved for widespread use.
Researchers are exploring treatment
with a compound called myoinositol. Early findings have shown that nerves in
diabetic animals and humans have less than normal amounts of this substance.
Myoinositol supplements increase the levels of this substance in tissues of
diabetic animals, but research is still needed to show any concrete lasting
benefits from this treatment.
area of research concerns the drug aminoguanidine. In animals, this drug blocks
cross-linking of proteins that occurs more quickly than normal in tissues
exposed to high levels of glucose. Early clinical tests are under way to
determine the effects of aminoguanidine in humans.
One approach that appeared promising
involved the use of aldose reductase inhibitors (ARIs). ARIs are a class of
drugs that block the formation of the sugar alcohol sorbitol, which is thought
to damage nerves. Scientists hoped these drugs would prevent and might even
repair nerve damage. But so far, clinical trials have shown that these drugs
have major side effects and, consequently, they are not available for clinical
Some General Hints
•Ask your doctor to suggest an
exercise routine that is right for you. Many people who exercise regularly find
the pain of neuropathy less severe. Aside from helping you reach and maintain a
healthy weight, exercise also improves the body's use of insulin, helps improve
circulation, and strengthens muscles. Check with your doctor before starting
exercise that can be hard on your feet, such as running or aerobics.
- If you smoke, try to stop because smoking makes
circulatory problems worse and increases the risk of neuropathy and heart
- Reduce the amount of alcohol you drink. Recent
research has indicated that as few as four drinks per week can worsen
- Take special care of your feet.