In this lecture,
we're going to learn about Neoplastic
or Paraneoplastic causes of
neuromuscular junction disorders.
We're going to focus on
Lambert-Eaton myasthenic syndrome.
A really rare but fascinating syndrome
that you know it when you see it
and say you ought to know
it so you can see it.
Let's start with a case.
This is a 42-year-old man
who presents with weakness.
This 42-year-old man presents
for evaluation of weakness
and new right upper
lobe lung mass.
He reports three months
of blurry vision,
sometimes double vision,
as well as weakness that began in his arms
and have progressed
to include his legs.
He's been unable to ride his
motorcycle due to these symptoms.
He reports a 20-pound weight
loss in the last three months.
He has no fatigable weakness but does
report dry mouth, that is also new.
Examination shows bilateral ptosis,
mild dysarthria, proximal upper
and lower extremity weakness,
normal sensation, and diffuse hyporeflexia.
So, what's the diagnosis?
Well, let's look at those three main features
of a peripheral nervous system disorder.
What's the distribution?
What are the sensory findings?
What's the reflex exam?
And are there any important wildcard
symptoms present in this case?
The distribution here,
involves bulbar weakness.
We see bilateral
ptosis, mild dysarthria,
there are bulbar findings,
in addition to proximal weakness.
That's the distribution that doesn't
support a muscle localization.
This doesn't sound like
peripheral nerve dermatome.
This sounds like a
neuromuscular junction disorder,
proximal weakness with
prominent bulbar findings.
The sensory exam is normal
pointing away from a nerve problem
and the reflexes
Not a reflexia likely would
see with a nerve problem,
but diffuse hyporeflexia that is
supportive of a junctional disorder.
What about wildcard features?
Well, here this patient has a right
upper lobe lung mass, that's concerning.
It needs to be further evaluated
and a 20-pound weight loss.
We're worrying about cancer and a
possible cancer associated condition
like a paraneoplastic disorder.
Let's look at this
patient's chest x-ray.
We see that here.
We see the normal findings
of the lung and the heart,
and this opacity in the right lung,
that's concerning for a new mass
and needs to be further evaluated
in this for a possible lung cancer.
So what's the diagnosis?
Is this myasthenia gravis, organophosphate
poisoning, botulism toxicity
All our neuromuscular junction
disorders, all can present with weakness.
Which one is present
in this case?
Well, myasthenia gravis could
be the case for this patient.
But with a new lung mass,
a 20-pound weight loss,
we have to be concerned for
an alternative etiology.
The patient has not
and organophosphate poisoning
does not sound like,
the likely diagnosis
for this patient.
There's no exposure to botulism toxin to
suggest botulism or botulism toxin toxicity.
This is a case of Lambert-Eaton
And we see a classic presentation of proximal
weakness with prominent bulbar fibers,
prominent bulbar findings
and some other important clinical
features that point us in that direction.
Lambert-Eaton is associated
with certain types of cancer
and we're concerned that this patient
may have a new diagnosis of lung cancer.