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What
is MG?
Myasthenia Gravis
is an autoimmune disease.
That
means that your bodies immune system which is supposed to fight bacteria
and viruses has gone a little crazy and has decided to attack itself.
- With
MG your body makes a protein called an antibody which attacks a small
piece of your muscle called the acetylcholine receptor. This receptor
needs to be activated in order for the muscle to contract.
-
With MG, as the attack on the acetylcholine receptor continues, the
number of receptors decreases and people are left with the inability
to move their muscles repeatedly.
- Often
a person with MG can have relatively normal strength in the mornings
or after brief rest, but then the symptoms worsen with repeated activity.
- Weakness
usually affects proximal muscles, such as upper arms and upper thighs
first. In many people the symptoms also involve the eyes with drooping
eyelids and double vision.
- Pain
is not a common symptom of MG and numbness and tingling is never a symptom
of MG.
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How is MG diagnosed?
There are two ways to make the diagnosis. These two tests detect 98% of
patients with MG.
- The
most sensitive and specific way to make the diagnosis is with a blood
test looking for the presence of the antibodies against the acetylcholine
receptor. If these are present you have MG. 10-15% of patients with
MG can still have antibodies that are not detected by our tests. For
these people an EMG/NCS should be performed. This is a test of the way
our nerves and muscles work. This has to be performed with "repetitive
stimulation" if one is concerned about MG. This also needs to be performed
by a person with special training in the test.
- If
one still suspects MG then a very special test called a "single fiber
EMG" can be performed. This is highly sensitive, meaning everyone with
MG will have an abnormal test. However, it is not very sensitive, meaning
that it can be abnormal for reasons other than MG. This test is done
by only a few very specially trained neurologists.
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What
Treatments are there?
-
Since myasthenia is caused by an abnormal protein in the blood, the
acteylcholine receptor antibody (AchR Aby) the best way to treat MG
is to get rid of this antibody. This can be done most rapidly by a process
called plasmaphresis, which is a form of dialysis or blood washing.
This actually removes the AchR Aby from your blood. However, it does
not prevent the antibody from being made again. Plasmaphresis is therefore
used for people who are very sick from their MG and need to get better
quickly.
- The
second line of treatments then are drugs we use to prevent the antibodies
from being made. This involves medications which suppress our immune
system, since antibodies are made by our immune system. There are many
choices of medications but the most widely effective choice is steroids.
Other drugs such as immuran, cyclosporine, or cellcept are used as well.
All of these medications have serious side effects and therefore should
only be used by a neurologist familiar with treating this disease.
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What
is the thymus?
The
thymus is a gland in our chests which allows our immune system to mature
correctly. Some people with MG have a tumor of the thymus gland called
a thymoma. Other people with MG have an overgrowth of their thymus. For
the last twenty years neurologists have believed that removing the thymus
gland, even if it is not cancerous makes the long term treatment of the
disease much easier. There is a well designed trial about to begin to
test this theory. Currently , thymectomy is still considered a very good
option for anyone with moderate or severe disease who is a good surgical
candidate.
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Do we know what causes our bodies to produce antibodies
to attack our muscles?
There is no known cause for MG. There is a link to other autoimmune diseases
such as thyroid disease or diabetes. There may also be a link to the thymus
gland, but as of yet there is no answer to why some people make antibodies
to the acetylcholine receptor.
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How do our muscles recover their strength with no medication
if we rest?
MG is caused when the number of receptors for acetylcholine on the muscle
falls below a certain level. We need acetylcholine to interact with the
receptors to make our muscles move. These receptors are destroyed by the
antibodies which are produced in MG. In some people with MG there are
enough receptors to make your muscles move once or twice but then the
muscles fatigue because the receptors have not gotten ready to be stimulated
again. With rest the acetylcholine receptors can prepare themselves to
be restimulated so symptoms seem better but then there is fatigue again.
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Why do my symptoms come and go?
Symptoms come and go for the reasons mentioned above
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Can Certain Foods trigger MG exacerbation i.e.: salty foods?
There are no foods which we know of that can trigger MG exacerbation.
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Why does daylight or bright light cause my eyelids to "shut
down"?
There should not be any change in symptoms with daylight, although some
people notice a change with temperature. There is another disease cause
blepharospasm which causes involunary forced eye closure and this is triggered
by sunlight. If the eyelids seem to be forced down as opposed to being
weak, then you should consider the possibility of blepharospasm.
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Why does excess Mestinon exacerbate my symptoms and make
my muscles weaker than they had been without it.
Excess Mestinon can make MG worse because it will cause over stimulation
of the acetylcholine receptors which can lead to muscle weakness. If you
believe that excess Mestinon is causing your muscle weakness you should
discuss this with your doctor because this can be serious. Usually if
you have too much Mestinon you will also be sweaty, nauseated, and have
diarrhea.
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I'm now on 3 grams Cellcept and 125 mg Cyclosporine/day;
they seem to control my MG symptoms but my overall strength seems to have
diminished over what it had been when I was first diagnosed. Is this MG
related or just a coincidence?
The main symptom of MG is muscle weakness, so if you are weak I would
be concerned that your MG symptoms are not completely controlled. You
should discuss this with your doctor.
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Sometimes my tongue feels fat and swollen as well as my
throat and everything seems to be closing up and trouble breathing. Am
I really swelling or does it only feel that way? If it is really swelling,
then why wouldn't physicians be able to prescribe drugs such as anti allergy
drugs to fight this problem?
In MG the tongue and throat can feel thick or swollen because they do
not move well. This can be a serious medical problem and so I would say
you need to discuss this with your doctor.
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Are there any known links or research regarding any kind
of connection between MG and Fibromyalgia Syndrome?
There are no known links between Fibromyalgia and MG. MG has a known cause
and treatment. Fibromyalgia has not yet been shown to have a known cause
or a specific pathology or treatment. Some people that I have seen who
have been diagnosed with fibromyalgia are in fact significantly weak and
with the correct diagnostic tools are shown to have MG. So i would say
if there is a lot of weakness then one should look aggresively for MG.
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What do you think about sero-negative MG? Is this widely
accepted or not in the neuro community? What would finally get a neuro
to give an MG diagnosis, with tests being negative but with MG signs/symptoms?
Sero-negative MG is widely accepted. It is believed approximately
10% of patients with MG are seronegative. However new antibodies are being
discovered so this number will decline over the next few years. If you
believe someone has MG but has normal blood tests then you need to do
a good EMG/NCS including repetitive nerve stimulation and possibly single
fiber EMG. If all of these are negative than I don't believe you can make
a diagnosis of MG.
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When I eat a meal, I notice that my sinuses seem to clog
up and I have to blow my nose constantly. I just assumed that it was me,
until I read of another Myasthenic who has the same problem. Is this a
common problem?
In MG if your swallowing muscles are weak then eating or drinking can
cause the food to come out of the nose. This is also a serious problem
because it can be a sign that your breathing muscles are weak. You should
discuss this with your doctor
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