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Autonomic neuropathy
Small fiber neuropathy
Overview by M.C.
Autonomic neuropathy is caused by damage to the nerves that regulate your heart rate, blood pressure, perspiration and
digestion, among other functions. Neuropathy means damage to your nerves. Autonomic
neuropathy is are often
due to diabetes, autoimmune diseases, infections or toxic
conditions. Your nerves transmit messages between your brain and your organs. Damage to your
autonomic nerves results in faulty communication with your brain
and the affected parts of the body .
Signs and symptoms are variable on which nerves are affected
but can range from dizziness to trouble with digestion and urination
to sexual difficulties. Treatment involves addressing the underlying
cause, if possible, and managing the signs and symptoms.
Signs and symptoms
Signs and symptoms of autonomic neuropathy depend on which parts
of your autonomic nervous system are most affected. They may
include:
- A drop in blood pressure on standing
(orthostatic hypotension), which can cause dizziness and
fainting
- Trouble with urination, including
diminished sensation, overflow incontinence and inability to
empty your bladder completely, which can lead to urinary tract
infections
- Male impotence
- Vaginal dryness and difficulties with
arousal and orgasm in women
- Difficulty digesting food (gastroparesis),
which can cause diarrhea, constipation, abdominal bloating,
nausea, vomiting, heartburn, feeling full after eating little
and loss of appetite
- Cardiovascular problems, such as heart
rate abnormalities
- Heat intolerance, especially during
exercise, and abnormal — usually decreased — sweating
- Sluggish pupil reaction to light and
dark
- Exercise intolerance, which causes your
heart rate to remain unchanged instead of increasing and
decreasing in response to your activity level
- Lack of the usual warning signs of low
blood sugar (hypoglycemia), which include shakiness, sweating
and palpitation
Severe drop in blood pressure on standing: What causes this?
Urinary incontinence
Urinary tract infection (UTI)
Erectile dysfunction
Erectile dysfunction in diabetes: Keys to prevention
Vaginal dryness
Diabetic gastroparesis
Constipation
Diarrhea
Cardiovascular disease 101: Know your heart and blood vessels
Hypoglycemia
Causes
Your nervous system is made up of two parts. The core is your
central nervous system — your brain and spinal cord. The rest of
your nervous system, branching off from your spinal cord to the rest
of your body, is your peripheral nervous system.
Part of the peripheral nervous system involves nerves that you
consciously control — such as nerves you use to move your voluntary
muscles. Part is your autonomous nervous system — the nerves that
regulate the part of your nervous system that you can't control,
such as your heart rate, blood pressure and digestion.
Damage to your peripheral nerves is called peripheral neuropathy.
Autonomic neuropathy is a type of peripheral neuropathy in which the
very small nerves are damaged.
A number of conditions can lead to damage of the autonomic
nerves. The most common cause is diabetes. About half of the people
who have diabetes eventually develop some type of neuropathy.
Other causes may include:
- Alcoholism, a chronic, progressive
disease that can lead to nerve damage
- Abnormal protein buildup in organs (amyloidosis),
which affects the organs and the nervous system
- Autoimmune diseases, in which your
immune system attacks and damages parts of your body, including
your nerves
- Some tumors, which can press on nerves
and cause direct or remote damage (paraneoplastic syndrome)
- Multiple system atrophy, a degenerative
disorder that destroys the nervous system
- Surgical or traumatic injury to nerves
- Other chronic illnesses such as
Parkinson's disease and HIV/AIDS
Risk factor
Having diabetes puts you at high risk of developing nerve damage,
including autonomic neuropathy. The longer you have diabetes, the
higher your risk. Risk is highest for people who've had the disease
for more than 25 years, who are older than 40 and who have
difficulty controlling their blood sugar.
Researchers don't yet understand how having diabetes can cause
nerve damage, but they suspect that high blood sugar plays a role.
In fact, the higher the blood sugar, the greater chance you have of
nerve damage. Controlling blood sugar — keeping it as close to the
normal range as possible — decreases the risk of developing nerve
damage or helps keep it from progressing.
When to seek medical advice
If you have diabetes, a compromised immune system or other
chronic medical condition, see your doctor regularly. Seek medical
care promptly if you begin experiencing any of the signs and
symptoms of autonomic neuropathy.
Screening and diagnosis: Small Fiber Neuropathy can be tested by
a skin biopsy.EMG.NCV is useless
test for small fiber neuropathy.
SSEP: somatosensory evoked responses can be abnormal.
Because autonomic neuropathy isn't a single disease, it can be
difficult to diagnose. Often, determining the diagnosis is a matter
of ruling out other causes of the symptoms. Your doctor is likely to
take a medical history, ask for a thorough description of your
symptoms and do a physical exam.
Your doctor also may use a number of tests to aid in diagnosis.
These may include:
- Autonomic tests. These
tests measure what happens to your heart rate and blood pressure
and how much you sweat in response to certain maneuvers.
- Electrocardiogram. This
test can measure the electrical impulses of your heart while you
exhale forcibly into an instrument (Valsalva maneuver). This
maneuver increases the pressure in the blood vessels in your
head.
- Tilt-table test. This
test monitors your blood pressure and heart rate as you lie flat
on a table that is tilted to raise the upper part of your body.
The tilting places stress on your autonomic nervous system,
which regulates your blood pressure and heart rate. Your doctor
can see how you respond to a situation that's similar to what
occurs when you stand up from lying down. Normally, your body
compensates for the drop in blood pressure that occurs when you
stand up by narrowing your blood vessels and increasing your
heart rate. However, this process may not occur properly in
autonomic neuropathy.
- Quantitative sudomotor axon
reflex test (QSART). A small electrical current passes
through four capsules placed on your forearm, foot and leg to
activate the nerves that supply your sweat glands. You'll feel a
slight burning sensation during this test.
- Thermoregulatory sweat test.
During this test, you're coated with a powder that changes color
when you sweat. You then enter a chamber with slowly increasing
temperature. It causes your body temperature to increase 1 to
1.5 degrees Celsius, which makes most people sweat. Digital
photos document the results. Your sweat pattern may help confirm
a diagnosis of autonomic neuropathy or other causes for
decreased sweating.
- Ultrasound. For those
with bladder symptoms, high-frequency sound waves create an
image of the bladder and other parts of the urinary tract, which
your doctor can check for abnormalities.
Complications
The possible complications of autonomic neuropathy are many. They
may include:
- Injuries from falls caused by lowered
blood pressure when you stand
- Mental and physical fatigue due to low
blood pressure
- Malnutrition and weight loss from
digestive system difficulties
- Fluid or electrolyte imbalance from
excessive vomiting or diarrhea, a condition in which your body
loses minerals you need
- Relationship problems due to sexual
dysfunction
- Urinary tract infections
- Cardiovascular complications, such as
irregular heartbeat (arrhythmia)
- Kidney failure from bladder problems
that aren't treated properly
Treatment
Treatment for autonomic neuropathy depends on the underlying
cause and the particular signs and symptoms you're experiencing. For
example, if the underlying cause is diabetes or an autoimmune
disease, treatment will focus on modulating your immune system and
decreasing inflammation. By using IVIg both autonomic and diabetic
neuropathy can be treated.
The goal of treatment is to manage the underlying condition,
repair nerve damage, if possible, and provide symptom relief.
Medications
The type of medication your doctor may prescribe depends on your
symptoms.
- Gastrointestinal symptoms.
Your doctor may prescribe metoclopramide (Reglan, Metoclopramide
HCL), which helps your stomach empty more rapidly by increasing
the contractions of the stomach and intestines. Possible side
effects include diarrhea when taken in high doses, drowsiness
and restlessness. Other medications include fiber supplements
such as psyllium (Metamucil) or methylcellulose (Citrucel) to
relieve constipation and tricyclic antidepressants such as
imipramine (Tofranil) and amitriptyline for diarrhea and
abdominal pain. Possible side effects of tricyclic
antidepressants include orthostatic hypotension, drowsiness,
urinary retention, constipation and dry mouth.
- Sexual dysfunction.
Your doctor may prescribe sildenafil (Viagra), vardenafil (Levitra)
or tadalafil (Cialis) for erectile dysfunction. Possible side
effects include flushing, indigestion and headache. Don't take
these medications if you've had a heart attack, stroke or
life-threatening heart rhythm in the previous six
months.Treatmentsfor vaginal dryness include vaginal estrogen
cream (Premarin, Estrace), which you insert into your vagina
with an applicator two or three times a week, and vaginal
estrogen rings (Estring), which releases estrogen for 90 days.
- Bladder problems.
Bethanechol (Urecholine) helps cause urination and emptying of
the bladder. Possible side effects include dizziness,
lightheadedness or fainting. Your doctor may prescribe an
antibiotic to clear up a urinary tract infection.
- Postural hypotension.
If you get dizzy or feel faint from a drop in blood pressure
when you get up, your doctor may prescribe medication, a
high-salt diet or support stockings. He or she may prescribe
fludrocortisone acetate (Florinef) to help your body retain salt
or recommend a blood pressure regulator such as midodrine (ProAmatine).
Possible side effects of midodrine include blurred vision,
headache and pounding in the ears. Recently, pyridostigmine
(Mestinon) has shown promising results for treating postural
hypotension without causing high blood pressure while lying down
(supine hypertension), a common problem with midodrine.
- Sweating. If autonomic
neuropathy affects sweating, it usually causes a decrease. But
if you experience excessive sweating, your doctor may prescribe
a drug that inhibits sweating, such as belladonna alkaloids
(scopolamine, glycopyrrolate) or botulinum toxin type A (Botox).
Possible side effects of belladonna alkaloids include blurred
vision, drowsiness, dizziness and dryness of the mouth, nose and
throat. Botox, given by injection, can cause a skin rash or
reaction at the injection site.
Therapies and procedures
If you have trouble emptying your bladder fully, your doctor may
recommend intermittent urinary catheterization, a procedure in which
a tube is threaded through your urethra to empty your bladder.
Psychotherapy or counseling may be appropriate if you're depressed.
Sex therapy or couples counseling might be helpful if you're
experiencing relationship problems as a result of sexual
dysfunction.
Prevention
Taking good care of your health in general and managing any
medical condition that puts you at risk of autonomic neuropathy is
the best prevention. Unfortunately, however, there's no way to
prevent degenerative diseases, such as multiple system atrophy, that
increase the risk of developing autonomic neuropathy. Ways to help
prevent autonomic neuropathy may include:
- Control your blood sugar if you have
diabetes.
- Get help if you have a problem with
alcohol.
- Get appropriate treatment if you have an
autoimmune disease.
- Achieve and maintain a healthy weight.
- Exercise regularly.
Self-care
If you have trouble digesting food and your symptoms are mild,
your doctor might recommend eating small, frequent meals, avoiding
fats and reducing intake of dietary fiber. For a drop in blood
pressure when you stand up, wearing elastic stockings and sleeping
with your head elevated may help.
Coping skills
Living with a chronic illness or disability presents daily
challenges. Some of these suggestions may make it easier for you to
cope:
- Set priorities. Decide
which tasks you need to do on a given day, such as paying bills
or shopping for groceries, and which can wait until another
time. Stay active, but don't overdo.
- Seek and accept support.
Having a support system and a positive attitude can help you
cope with the challenges you face. Ask for or accept help when
you need it. Don't shut yourself off from family and friends.
- Prepare for challenging
situations. If something especially stressful is coming
up in your life, such as a move or a new job, knowing what you
have to do ahead of time can help you cope.
- Talk to a counselor or
therapist. Depression and impotence are possible
complications of autonomic neuropathy. If you experience either,
you may find it helpful to talk to a counselor or therapist in
addition to your primary care doctor. There are treatments that
can help.
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