How do you determine if a patient
really has myasthenia gravis
When you get the phone call
and someone asks you about these symptoms,
you're gonna recommend
that they go see a healthcare provider.
But this is what they can expect
when they go see their healthcare provider
if this is a suspected diagnosis.
They'll do a physical
and neurological examination.
They'll do a tensilon test,
a blood test.
They'll do some electro diagnostics,
pulmonary function testing,
and they'll do a ice pack test.
So we've got these options
that we can look at
and that the healthcare provider
is likely to do
to determine the diagnosis.
So, first up, it's a physical
and a neurological examination.
Now you're very familiar with this,
but the physician will review
the individual's medical history
and they'll do
a full physical examination.
Now in the neuro exam, the physician
will look at their muscle strength
and their tone, their coordination,
their sense of touch,
and look for any impairment,
particularly, in eye movement.
are very consistent.
But in this one, they'll be really looking
for any problems with symmetry
and any problems with eyelids
in particular called “ptosis.”
Now this edrophonium test,
that's another fun word as to say,
that's why I call it the tensilon test.
It's a lot easier.
Because this is what we're doing.
If the patient is experiencing
The test uses an injection of tensilon.
It's a lot easier to say
So we use tensilon, it's injected.
And if the weakness in the patient
then we know it's likely
Okay, so how does injecting
something relieve that?
Well, this drug tensilon,
the breakdown of acetylcholine
and it temporarily increases
the levels of acetylcholine
at the neuromuscular junction.
Okay, stop for a minute and think back.
We had that really cool drawing.
In fact, if you want to look back
in your notes at that
as we're talking through,
that's good, too.
But remember as the impulse
travels down the nerve,
it tells the nerve to release
acetylcholine into the junction.
When it releases that acetylcholine
into the junction
in healthy, normal areas,
it would attach
the acetylcholine receptors.
Well, this drug will provide
because in myasthenia gravis,
those receptors are kind of messed up.
So, temporarily, if we use this drug,
there'll be extra acetylcholine available,
you should see a resolution
of those symptoms.
So we usually use it to test
if the patient is having the eye symptoms.
So when you hear tensilon test,
that means we're injecting the patient
with this medication,
and it should help increase
the levels of acetylcholine
at the neuromuscular junction,
and their eye paralysis
or those sagging droopy eyelids
should be resolved temporarily.
Now we can't keep giving this
to the patient,
it's just used for a test.
The test is no longer
used in the US
due to a high number of
Now a blood test is the most
common method for testing
We do have some blood tests,
won't be as dramatic
as what you see with the tensilon test.
But a lot of people
with myasthenia gravis
have some abnormally elevated levels
of acetylcholine receptor antibodies.
So that second antibody we talked about,
sounds like a way
to keep away junior high boys,
but the anti-MuSK antibodies
also been found in about half of the people
who have myasthenia gravis
who don't have
the acetylcholine receptor antibodies.
But here's the bad news,
a blood test can detect
but some individuals with myasthenia gravis
don't have either one
of those antibodies.
So, go back up to the first point,
make sure you underline
acetylcholine receptor antibodies.
Go into the second point
and underline anti-MuSK antibody.
So when you're looking our third point
when we talked about how some patients
don't have either of these antibodies,
always remind yourself
of the two we're talking about:
acetylcholine receptor antibodies
and anti-MuSK antibodies.
These people are called seronegative.
So underline that word,
it means negative antibody myasthenia.
That means we can do
a blood test on these patients,
but they're not going to have either one,
acetylcholine receptor antibodies,
or the anti-MuSK antibodies
that are visible.
So blood test is a shot.
It might tell us something.
But even if it comes back negative,
that wouldn't confirm that the patient
doesn't have myasthenia gravis.
Okay. We're three tests in.
Pause the video for just a second
and see if you can quickly
run through the three tests
we've just talked about,
and what they would tell us
about a patient with myasthenia gravis.
Okay, good job.
We're at the halfway mark.
You've done review
the three first tests.
Now we're gonna go
through four, five, and six.
Now this one is a little unusual.
I don't think I really enjoyed this test
if I had to have it done.
It uses repetitive nerve stimulation.
Okay, so it repeatedly stimulate
a person's nerves
with small pulses of electricity.
Yeah, you heard me,
small pulses of electricity.
I know we call them small,
but it's still not very comfortable.
And the goal is to just wear out
very specific muscles.
That's why they use small pulses
and they use electricity.
They're just gonna wear out the muscle.
Because muscle fibers
in myasthenia gravis,
as well as some other
don't respond as well
to repeated electrical stimulation
as compared to muscles
that have normal--
from normal individuals.
Okay, so first one, got the idea?
We're gonna use
small electrical impulses
and we're gonna hope
that we could just work at it
till we tire that muscle out,
and we'll be able to recognize
if the patient has myasthenia gravis,
their muscles will not respond as well
to the repeated stimulation
because you're just wearing things out.
Remember how the nerve
to muscle works.
Eventually, you're gonna wear,
run out of things,
because they don't have the receptors
to follow along
a normal nerve stimulation.
Well, that's one way we can do it.
Now there's also a single fiber
Now I went to one of these
with my mom
and I really was sure I don't ever want
to have one of these.
It's really not that bad,
but I don't think I want
to sign up for one.
This is the most sensitive test
for myasthenia gravis.
So this one is better
than what we just discussed.
So make sure you star this
and say that this is most likely
what the health care provider
will order if it's available.
So, it's a single fiber EMG.
It is the most sensitive test
from myasthenia gravis.
It detects impaired nerve
to muscle transmission.
So an EMG can be really helpful
in diagnosing mild cases
of myasthenia gravis
when the other tests don't.
So remember, put a star by this one.
If I was concerned
that I had myasthenia gravis,
this would be the test.
Even though I wouldn't like it,
this would be the test
that I would want to see done.
Now we can go to diagnostic imaging.
Okay, before you read the slide,
stop for just a minute,
think about what we know
about myasthenia gravis.
Why would we go
to a CAT scan or an MRI?
What are we gonna look at?
We're not gonna X-ray
their eyelid, right?
Yeah, that's what a cat scan
or an MRI might show us.
That thymoma, right?
Now they may or may not have it,
but this would definitely determine
if they did or did not.
Now where is the thymus gland located?
Right, behind the breastbone.
When is the thymus gland the biggest?
Looking at lifespan,
when is it the largest?
Right, relatively when I'm a little kid,
and then as I as I progress
it keeps getting a little bit bigger.
So, it should get smaller
as an adult
and be replaced with, what?
Yeah, the sad news, fat.
All right, the sixth one,
pulmonary function testing.
Now this one is just gonna help us
give us an idea
of what the patient's
respiratory status is,
how it's doing,
how strong they are.
Because measuring breathing strength
can help predict
if the patient may be leaning
towards a myasthenia crisis
and have trouble with respiratory issues.