Lambert-Eaton myasthenic syndrome.
Before we begin, where are you?
Now, once you’re dealing with
the neuromuscular junction,
then proximal muscles would be
affected more so than the distal.
Now, this one is even
The reason I say that is,
these days are long
with recordings, right?
And these days are long
in general in medicine.
But the way that I function is as
the day progresses, I get stronger.
Well, it’s not that I have
Lambert-Eaton myasthenic syndrome,
but that’s how that patient
is going to be behave.
“Doc, I wake up in the morning
and I feel like crap.”
And then what happens?
As the day progresses, I keep getting
stronger and stronger and stronger.
So, where is my weakness
and what’s my problem?
The problem is presynaptically.
So now, I need you to think about
what happens physiologically
when you’re trying to
release your acetylcholine.
You need action potential to then open
up the voltage-gated calcium channels.
What’s voltage-gated calcium channels?
Bring in the calcium and then you have
fusion of your acetylcholine vesicles
with the presynaptic terminal.
You then release acetylcholine and then you
bind to your acetylcholine receptors.
As the day progresses, the body is going to
find a way to release that acetylcholine.
Listen, your body is going to find a
way to release that acetylcholine,
which means what?
You have no problem with
the receptor, do you?
You don’t have a problem
with the receptor.
So, acetylcholine will bind to the
receptor, and once it does so,
then you’re going to
elicit an action potential.
Seventy five percent have an autonomic
symptom, which are frequent.
For example, dry eyes,
dry mouth, impotence.
Pupils can be involved,
parasympathetic dysfunction, perhaps,
because it’s a problem with the
voltage-gated calcium channels.
That’s the issue.
And that voltage-gated calcium channel
is not going to be as specific, right?
As it was from myasthenia gravis where
it was specifically the autoantibodies
were attacking the acetylcholine
receptors at the neuromuscular junction.
Deep tendon reflexes
reduced or absent.
And muscle facilitation
with brief exercise.
What’s interesting is the fact that
if you’re able to promote movement,
that there’s every possibility that the
patient is actually going to get stronger.
And please don’t forget, it’s
a part of paraneoplastic.
Let’s put everything together.
Autoantibodies directed against the
presynaptic voltage-gated calcium channel.
Strong association with
I’ve mentioned this a few times.
Paraneoplastically, you definitely want
to consider small cell lung cancer.
What does those small cell release
ADH and ACTH, good.
Your nerve conduction test,
with low frequency
The same thing that you would
find with myasthenia gravis.
incremental response with high
frequency repetitive stimulation
or after brief exercise.
That’s an important point.
You get stronger.
Management: Treat the underlying
malignancy if it’s discovered.
Less successful than in myasthenia
gravis, unfortunately: steroids,
steroid-sparing agents, perhaps, and by that
we mean immunomodulators, if necessary,
IVIG, and plasmapheresis, if we’re
getting into more of a crisis mode.
Our topic here very quickly is botulinum
toxin, and we put things into perspective.
I live in Southwest, Florida.
Stereotypically, we have
old people living there.
And for the most part, you walk
around Fifth Avenue in Naples
and you find your patients
pretty much look like this.
All right, they’re walking
around like this,
and they have tons of wrinkles, but
they really -- actually, they don’t.
They’re walking like this because they go
into a clinic to get shot up by Botox.
In other words, you’re getting
shot up by botulinum.
And what are you trying to do?
These patients are trying to get rid
of their wrinkles, aren’t they?
And so therefore, I tell myself,
“You look better with the wrinkles
as opposed to looking like
you have a masked face.”
But whatever, to each their own.
Next, how do you get
rid of the wrinkles?
Well, you’re inhibiting the release of
acetylcholine from the
It’s what the
botulinum toxin does.
But of course, your modification,
you get this Botox.
But keep that in mind though, huh?
What if you had a baby that
was exposed to botulinum?
Floppy baby, right?
Because the acetylcholine
is not being released.
The incubation period is 18 to approximately
38 hours, so a couple of days,
but can be as little
as two hours.
Next, weakness is
diffuse, as I told you,
proximal, once again,
more so than distal.
Here, there could be issues with
dilated pupil as well because why?
So, with botulinum, the toxin itself,
it’s going to inhibit the release
of acetylcholine everywhere, huh?
And the toxin interferes with
presynaptic release of acetylcholine.
That’s your mechanism of
action, either by the toxin or
let’s say cosmetically,