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Diabetic Neuropathy
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Nerve damage or Diabetic Neuropathy
resulting from chronically high blood sugars can be one of the most
frustrating and debilitating complications of diabetes because of the pain,
discomfort and disability it can cause, and because available treatments are
not uniformly successful.
Some patients find some relief from this nerve damage or neuropathy by
keeping blood sugars as closely controlled as possible, getting regular
exercise and keeping their weight under control. Using non-narcotic pain
relievers consistently throughout the day - rather than waiting until
nighttime when symptoms can become more severe - also seems to help if pain
is the major symptom. Surprisingly, clinicians have found that certain
antidepressants may be helpful and can take the edge off the pain of
neuropathy as well.
While pain or numbness in the legs or feet may be the most common
complaint from people diagnosed with neuropathy, it is not the only symptom
of this complication. Neuropathy can cause a host of different types of
symptoms, depending on whether nerves in the legs, the gastrointestinal
tract, or elsewhere in the body are affected. If you have any of these
symptoms, neuropathy may be the culprit:
1 inability to adequately empty the bladder of
its contents, resulting in frequent infections;
2 nausea, vomiting, abdominal fullness or
bloating, diarrhea, or constipation;
3 low blood pressure upon standing that causes
fainting or dizziness;
4 inability to lift the foot or new
deformities of the foot, or foot ulcers;
5 trouble achieving or maintaining an
erection.
While physicians have found some medications and other treatments that
help ease these symptoms in some people, prevention continues to be the key.
"Hemoglobin A1c readings should ideally be at 7.0 or below. Those that are
consistantly near or above 8 percent cause concern that any diabetes
complication, including neuropathy, may develop," says John Hare, M.D.,
medical director of Joslin's Affiliated Center's program. "The good news is
that the Diabetes Control and Complications Trial shows that people who keep
their blood sugars consistently in this healthful range can decrease their
risk of nerve damage by over 50 percent. Getting diabetes under better
control also may help limit the amount of damage caused by neuropathy once
it's developed."
If your doctor has told you that symptoms you have been experiencing are
a result of neuropathy, you certainly have many questions. Here are some
answers that may be helpful to you as you battle this complication.
What are the different types of neuropathy?
There are three broad types of neuropathy: sensory, autonomic and motor:
1 Sensory neuropathy (or peripheral
neuropathy, usually just called neuropathy) affects the nerves that
carry information to the brain about sensations from various parts of
the body - how hot or cold something is, what the texture of something
feels like, the pain caused by a sharp object or heat, etc. This is the
most common form of diabetic neuropathy.
2 Autonomic neuropathy affects the
nerves that control involuntary activities of the body, such as the
action of the stomach, intestine, bladder and even the heart.
3 Motor neuropathy affects the nerves
that carry signals to muscles to allow motions like walking and moving
fingers. This form of neuropathy is very rare in diabetes.
Sensory neuropathy can lead to pain, numbness or tingling in the
extremities and, ultimately, an inability to feel heat, cold, pain or any
other sensation in affected areas. Autonomic neuropathy can lead to
impotence in men, bladder neuropathy (which means the bladder is unable to
empty completely), diabetic diarrhea, or bloated stomach. Motor neuropathy
can lead to muscle weakness.
If you are diagnosed with neuropathy, your physician may use terms to
describe the type that you have based on whether only one side of your body
is affected (asymmetric) or both sides (symmetric). If only one kind of
nerve is affected, your doctor may say you have mononeuropathy. If several
nerves are affected, the term polyneuropathy may be used.
Other terms may be used based on what parts of the body are affected:
1 Distal Neuropathy - is a form of
sensory neuropathy that affects the hands or feet. It can be asymmetric
but is usually symmetric, and is the most frequently diagnosed type of
neuropathy
2 Femoral neuropathy -- is painful
sensory neuropathy that centers in the thigh muscles. It can be
asymmetric or symmetric.
3 Diabetic amyotrophy - is motor
neuropathy that affects the thigh nerves, with resulting weakness often
in addition to or instead of pain. It can be symmetric or asymmetric.
4 Gastroparesis -- is autonomic
neuropathy that affects the stomach, preventing it from emptying
normally. It can result in ulcer-like symptoms, vomiting, bloating, and
poor absorption of food resulting in malnutrition and hypoglycemic
episodes as food fails to be absorbed at the anticipated rate. High
blood sugars can later result when the meal finally makes its way
through the system.
5 Diabetic diarrhea - is autonomic
neuropathy that results in an erratic functioning of the small
intestine. This can cause unformed stools to be passed. If the nerves
which communicate with the sphincter muscles (which control passing a
bowel movement) are not working properly, stool can pass without
warning, and/or without being able to control when it comes out,
resulting in fecal incontinence. Constipation also can result when the
large intestine is involved and the stool remains in the large intestine
too long.
6 Bladder neuropathy - occurs when the
bladder nerves no longer respond normally to pressure as the bladder
fills with urine, and do not enable the bladder to empty completely.
Some urine continually stays in the bladder, leading to urinary tract
infections. Symptoms of this problem include cloudy urine, painful
urination, low back pain and fever.
7 Postural hypotension - is autonomic
neuropathy that results in low blood pressure when standing. In people
with postural hypotension, the pulse does not go up to compensate for
the change in blood pressure, so fainting and dizziness can result.
8 Charcot joint- is also called
neuropathic arthropathy and occurs when the bones in the feet fracture
or "powder" and the foot becomes misaligned. The foot becomes deformed
as a result of the lack of nerve stimulation, which causes the muscles
to lose the ability to support the foot properly. Walking makes it
worse. People who already have neuropathy in their feet and have lost
sensation are at a greater risk of developing this.
9 Unilateral foot drop - occurs when
the foot can't be picked up because a nerve in the leg has been damaged
either by blood vessel disease or compression.
10 Impotence - is caused by autonomic
neuropathy and/or sensory neuropathy, and/or blood vessel disease that
leads to an inability to have and maintain an erection in men.
What is peripheral neuropathy and what causes it?
Peripheral neuropathy (more commonly called neuropathy) is a general term
for diseases that cause damage to the nerves outside of the brain and spinal
cord. While diabetes is a frequent cause of neuropathy, it is not the only
cause. Nutritional deficiencies (B-12 and folate), chemical exposures,
pressure on nerves, or medications (such as some of those used for
chemotherapy or to treat AIDS), can also cause neuropathy.
Theories abound as to why exactly neuropathy occurs in people with
diabetes. In general, diabetic neuropathy is thought to be a result of
chronic nerve damage caused by high blood sugars. "There are many possible
ways this might happen," says Dr. Hare. "Nerves are surrounded by a covering
of cells, just like an electric wire is surrounded by insulation. The cells
surrounding a nerve are called Schwann cells. One theory suggests that
excess sugar circulating throughout the body interacts with an enzyme in the
Schwann cells, called aldose reductase. Aldose reductase transforms the
sugar into sorbitol, which in turn draws water into the Schwann cells,
causing them to swell. This in turn pinches the nerves themselves, causing
damage and in many cases pain. Unless the process is stopped and reversed,
both the Schwann cells and the nerves they surround die."
Another theory is that certain intracellular metabolites, such as
myoinositol, become depleted, leading to nerve damage. Still other theories
hold that pathways such as the protein kinase C pathway, being studied by
George King, M.D., and his colleagues at Joslin, are triggered by chronic
high blood sugars, resulting in several diabetes complications, perhaps
including neuropathy.
"Recent studies have suggested that decreased blood flow to the nerves
can also contribute to the development of diabetic nerve disease," says Dr.
King. There are multiple studies ongoing which are designed to improve blood
flow to the nerves in diabetic animals and in patients. Two new categories
of drugs being examined are called antioxidants and PKC inhibitors.
Preliminary studies using these drugs have shown encouraging results in
animal models of diabetes. Clinical trials are being planned and some are
already in progress.
How is neuropathy diagnosed?
People may seek their doctor's help for treatment of pain, not knowing
exactly what causes it. Men may come to the doctor concerned about a
decreasing ability to have and maintain an erection. Increasingly frequent
urinary tract infections may be another clue, as may be recurring diarrhea
or constipation, or vomiting or symptoms resembling an ulcer. Fainting
spells upon standing may indicate postural hypotension.
A physician may detect early signs of neuropathy. He or she may notice
that knee jerk and ankle jerk reflex tests show nerves aren't as responsive
as normal, or may observe a dip in blood pressure when you go from a
reclining to a sitting position. These are signs that increased attention to
blood sugars are warranted to try and limit further problems.
A variety of tests, including electromyography (a test that measures the
response of muscles to electrical impulses) and nerve conduction studies (a
study of the flow of electrical current through the nerves) combined with
clinical observations may help a physician rule out other possible causes of
pain, and diagnose neuropathy. To diagnose Charcot foot fracture, the doctor
may take an x-ray and possibly do a bone scan.
How is it treated?
Unfortunately, there are no miracle cures or treatments for neuropathy,
although a variety of treatments are often helpful. There is no way to heal
or replace nerves that have been damaged.
The most important thing someone who has neuropathy can do is keep their
blood sugar levels as close to normal as possible, exercise regularly, and
make sure their weight is as close to what it should be as possible. This
will help keep blood sugars closer to normal and limit the damage high blood
sugars can cause to nerves. Exercise will have the added benefit of keeping
muscles that may be weakened by decreasing nerve activity to remain strong
and toned. Dr. Hare says he finds that patients with painful neuropathy say
the pain seems less severe if they get some simple exercise regularly.
Patients with painful neuropathy will try almost any kind of pain
reliever their physicians will give them. "One can try a variety of
non-narcotic pain killers," says Dr. Hare. "But one should stay away from
the more powerful narcotics, which do not work very well for neuropathy, but
will lead to addiction."
Dr. Hare recommends acetaminophen (Tylenol®), aspirin and ibuprofen
(Motrin ® Advil ®:, etc.) first. Pain medicines are best used regularly
throughout the day, rather than waiting for pain to become severe. At that
point, pain medicines are less able to stem the tide, says Dr. Hare. Some
physicians recommend creams that contain capsaicin, an extract of the hot
capsicum pepper (which includes red, cayenne and tabasco peppers) and can be
rubbed on the skin over the pain. It is believed in some circumstances that
these creams block pain signals, although they do not work for everyone -
occasionally, they may even worsen the pain in some patients or cause other
adverse effects, like eye or skin irritation. Be sure to check with your
doctor before trying such products and follow application instructions
carefully. Capsaicin, which has been approved by the Food and Drug
Administration for treating pain, is available in over the counter topical
salves that include ArthiCare®: and Zostrix®:.
Certain antidepressants also seem to be particularly helpful for pain,
says Dr. Hare. Elavil ®: (amitriptyline), Norpramin®: (desipramine) or
Imipramine®: are members of the tricyclic antidepressant category of drugs.
These medications are not prescribed because the patient is depressed -
"although having constant pain for months can be depressing," notes Dr.
Hare. "Rather, it seems that the medications block the pain. Patients take
them at night, and they have the effect of helping patients tune the pain
out. When I prescribe them to patients, I explain that it's kind of like
having a full bladder. If you aren't doing anything, you notice the full
bladder and you feel the need to go to the bathroom right away. But if
you're engrossed in a TV show, you don't notice it as much and can go for
quite a while before going to the bathroom. These anti-depressants have
largely the same effect on pain, helping patients notice it less. Because
the pain is usually worse at night, patients take the medication at night
and it seems to help them sleep. It also helps them with the depression and
insomnia they may be experiencing as a result of the neuropathy."
"Antidepressants can take several weeks to become effective, so I tell
patients to give it a month before deciding whether it is helpful or not,"
says Dr. Hare. "These drugs can also cause dry mouth, which most patients
find not to be much of a problem."
Other types of drugs that sometimes help are anti-convulsants such as
phenytoin (Dilantin®:), carbamazepine (Tegretol®:) or gabapentin (Neurontin®:).
Drugs such as mexiletine (Mexitil®:) normally used to treat irregular heart
rhythm, sometimes relieve neuropathy pain. Drugs like metaxalone (Skelaxin®:)
that generally depress the central nervous system can help reduce muscle
pain. All of these drugs, however, can have such unpleasant side effects as
dizziness or confusion when taken in large doses, especially by elderly
patients.
Many patients will ask their physician about the value of nutritional
supplements or vitamins to ease pain. "If the neuropathy is caused by a
vitamin deficiency, such as a B vitamin deficiency, taking B6 or B12 will
help," notes Dr. Hare. "But if you're body is not deficient in these B
vitamins, the vitamins will just go down the drain in your urine. You'll
notice that your urine is a very bright yellow - but the treatment probably
won't do you any harm. As for other nutritional supplements or vitamin
treatments, there isn't anything that is widely accepted as being
useful-unfortunately. But other vitamins that are not so easily passed
through the urine can lead to vitamin toxicity. So you need to be careful
that you aren't taking too much of any vitamin supplement in the distant
hope of easing the pain."
Some patients have experienced success will other forms of pain
management - biofeedback, meditation, acupuncture, etc. "I don't discourage
a person from trying any safe, non-drug approach to pain relief," says Dr.
Hare. "What may not work for one person may work really well for someone
else."
For gastroparesis, in which the stomach is not emptying properly,
physicians at Joslin may prescribe Reglan ®: (metoclopramide), which will
help the stomach push food and get it through the rest of the digestive
process. These may be used in conjunction with Carafate ®: (sucralfate)
which "helps to sop up extra acid that may be sitting in the stomach," Dr.
Hare says.
For those experiencing bladder neuropathy, which results in the bladder
never completely emptying, Urecholine ®: may be prescribed. "This is a urine
propellant that helps to keep the bladder clear," says Dr. Hare. "Because
patients with this problem will be more likely to develop frequent urinary
tract infections, the physician may also prescribe chronic antibiotic
therapy to try and keep the bacterial count in the bladder and urinary tract
at a manageable level."
Impotence in men that is a result neuropathy or blood vessel damage
(versus psychological causes or due to medications such as anti-depressants
or blood pressure medication) can be treated using certain drugs that are
either inserted into the end of the penis or injected to cause an erection
before intercourse. Vacuum devices that enable an erection to be achieved,
or a surgically implanted prosthesis are also options to be explored with a
physician.
The new drug Viagra is also an option, although patients should be sure
to check closely with their physician before taking the drug. People with
diabetes are more prone to heart and blood vessel disease than
non-diabetics, and the use of Viagra leading to the resumption of sexual
activity in individuals with underlying cardiovascular disease (diagnosed or
undiagnosed) should be reviewed with a physician. Also, the use of Viagra
with nitroglycerine tablets (a treatment for acute heart problems such as
angina or heart attack) has led to several reported deaths. Finally, there
is an unproven suspicion that usage may affect retinal circulation (in
addition to its known side effects).
Patients with postural hypotension may be prescribed certain blood
pressure raising medications or may benefit from support stockings to
prevent pooling of blood in the legs. For patients with diabetes who also
have high blood pressure, the process of balancing blood pressure lowering
medications with medications that will keep blood pressure from dipping too
low while reclining and then sitting up can be particularly tricky, and may
require several adjustments to fine-tune.
Charcot damage is addressed by avoiding putting any weight on the foot
while it heals. The foot is usually put into a cast for a period of weeks to
limit damage. Later, the patient wears special shoes. Surgery may be needed
to restore a more normal shape to the foot.
Some patients may remember a lot of talk in the late 1980s and early
1990s about a new class of drugs called aldose reductase inhibitors, which
it was thought might be a significant breakthrough in treating some types of
neuropathy. "Unfortunately, to date none of these drugs has proven to be
sufficiently effective and side-effects have been a concern. As a result
none have come to market to treat neuropathy yet, although companies are
still working to develop them," says Dr. Hare.
How can further problems be avoided?
One of the major issues with neuropathy, particularly sensory neuropathy,
is that eventually the affected nerves die, and the patient experiences a
complete loss of sensation in the area. For this reason, if you have
developed neuropathy in your feet and legs, you need to check your feet
every day for cuts and other problems that you may no longer feel. You need
to make sure your shoes are in excellent condition and don't have pebbles or
rough spots in them that could damage feet without your knowing about it. If
you have neuropathy, you should not use heating pads or electric blankets -
you could be seriously burned without knowing it. You should be especially
careful when taking baths to ensure that the water is not too hot, as it
would be relatively easy to scald your feet or legs if they have become
desensitized to pain.
When will the pain end?
"There's no easy answer to the question, 'when will the pain end?',"
notes Dr. Hare. "Maybe if a patient gets their blood sugars under good
control, that will be enough to ease the pain. If it doesn't, perhaps a
daily regimen of Tylenol every few hours plus an anti-depressant at night
and regular exercise every day will make the pain manageable. It can take up
to two years for the pain of neuropathy - which is caused by ongoing damage
to the nerve - to be replaced by the numbness that occurs when the nerve
cells are more severely damaged. Our goal in the meantime is to identify
ways to help patients manage the pain and discomfort of neuropathy, and to
help patients lead as normal a life as possible despite the pain or other
side-effects caused by this complication."
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