00:00
And again,
when we evaluate patients,
we're thinking of the distribution.
00:05
Where are the problems?
Where does this weakness occur?
We should see
presence of bulbar findings.
00:11
And the presence of ptosis,
diplopia, dysarthria, and dysphasia
point towards a
neuromuscular junction etiology.
00:19
Sensory findings are normal.
00:21
Reflex examination often shows
normal reflexes.
00:24
And we're looking for
that wildcard symptom
the presence of fatigability.
00:28
Symptoms that worsen
when muscles are contracted.
00:32
After our first step is, to localize
to the neuromuscular junction,
we move to step two.
00:37
What is this
junctional disorder?
And we can walk through
the types of problems
that pathophysiologic processes
that occur in the body.
00:45
We can look for immune disorders.
00:47
And the immune disorder at the
neuromuscular junction
is called Myasthenia gravis.
00:51
We can look for infections.
00:53
And the primary infection to
effect the neuromuscular junction
is botulism.
00:57
It has a tropism and affinity
for the neuromuscular junction.
01:02
The neoplastic or
paraneoplastic disorder
that affects the
neuromuscular junction
is called Lambert-Eaton
myasthenic syndrome.
01:09
Toxins and metabolic problems
can also affect the
neuromuscular junction.
01:14
And there are specific drugs
that we need to think about
that can cause problems
in the neuromuscular junction.
01:20
And then there are some
inherited and congenital problems.
01:23
Congenital Myasthenia,
and Neonatal myasthenia
that can also affect
the neuromuscular junction.
01:29
We're going to walk through
each of these disorders
in subsequent lectures.
01:33
But right now,
I want you to know
that those are the conditions
that we should focus on
when we're dealing
with a problem or a patient
who presents with
neuromuscular junction
signs and symptoms.
01:43
So let's look at
where those occur.
01:45
We said junctional disorders
should be broken down
into presynaptic
and postsynaptic disorders,
where to each one of those fall.
01:52
Well, Myasthenia gravis
the most common
junctional disorder
and one that we really need to know
is a postsynaptic problem.
01:58
This disorder results from
problems abnormality
with the postsynaptic
acetylcholine receptor.
02:06
Anesthetics affect the
postsynaptic action
of acetylcholine binding to that
postsynaptic acetylcholine receptor
and muscle depolarization.
02:15
Lambert-Eaton Myas Syndrome.
02:17
Myasthenic syndrome
is an important cause
of a presynaptic
junctional disorder.
02:21
Antibodies to the presynaptic
voltage-gated calcium channels
prevent that influx of calcium and
the communication can't proceed
down the presynaptic terminus
into the junction.
02:34
Botulism is a disorder
and infection that affects
the binding of the vesicles
to the presynaptic membrane.
02:40
And so this is also
another important
presynaptic
junctional disorder.
02:44
And then lastly,
cholinestarase inhibitors
affect that cholinestarase enzyme
in the synaptic cleft.
02:51
So again, I want you to know
about the important
presynaptic and postsynaptic
disorders
that affect the
neuromuscular junction.