00:02
Here, we’ll take a look at
neuromuscular diseases.
00:04
Let’s begin.
00:06
But first, I want you to get an
orientation of neuromuscular diseases,
but before we do that,
taking a section out
of a spinal cord,
I want you to move
from your left.
00:17
We see a spinal cord.
00:19
And we’re going to amplify, amplify,
amplify, from left to right.
00:23
I want you to orient yourself
to the actual spinal cord
where the anterior is on top.
00:29
Is that clear?
But you knew that already
because the anterior horn represents
motor neuron, doesn’t it?
And so therefore, we’ll talk
about motor neuron diseases.
00:41
Not yet.
00:42
Because our topic here is
neuromuscular disease.
00:46
Now as you move out from the
motor, and you get into the CNS –
or into the PNS, excuse me.
00:52
Then, we’ll start to talk
about peripheral neuropathies
and that’s the other big
bracket that you see there.
00:57
But that’s not the topic yet.
01:00
I want you to move out
from the peripheral nerve
and then finally make
it out to the muscle.
01:04
Ah!
And then at that muscle is
your neuromuscular junction.
01:10
And at that
neuromuscular junction,
we’ll talk about a few of these
issue of neuromuscular diseases.
01:16
And at some point in time,
when the time is right,
we’ll talk about muscle itself undergoing
disease and those are myopathies.
01:23
It’s a beautiful picture to give you
an outline as to topics to come.
01:27
Motor neuron diseases and
peripheral neuropathies,
myopathies or even neuromuscular disease,
which is our specific
topic in this section.
01:38
Under neuromuscular disease, you can
do degenerative as being a category.
01:42
And this is your Lou Gehrig or, a.k.a.,
amyotrophic lateral sclerosis.
01:49
With amyotrophic lateral sclerosis, let
me give you a brief little introduction.
01:53
You’ll have motor issues only.
01:57
Sensory will be intact.
01:59
ALS.
02:00
Hereditary:
a common one, known as spinal
muscular atrophy or SMA.
02:06
And there’s one
called Kennedy’s.
02:08
Under infectious,
poliomyelitis and
West Nile syndrome.
02:15
Let’s begin now our discussion by looking
at amyotrophic lateral sclerosis or
known as Lou Gehrig’s disease.
02:21
What happens?
You only lose your
motor, but of what type?
Loss of upper and
lower motor neuron
in anterior horn of the spinal cord
and in the corticospinal tract.
02:33
So what happens?
You result in muscle
atrophy and hyperreflexia.
02:38
Remember, you’ll have both lower and
upper motor neuron type of lesions.
02:42
Amyotrophic lateral sclerosis.
02:44
What about sensory?
Intact.
02:46
If you want, go back to that picture,
that schematic that I showed you
where we move out from
the anterior horn
and then come out
through the motor,
and then hit the
neuromuscular junction.
02:58
With Lou Gehrig’s disease, the
majority are sporadic and idiopathic.
03:02
There is a familial type that
you want to memorize here,
a genetic locus at your
superoxide dismutase 1
or SOD1 gene on chromosome 21,
which is a copper-zinc
superoxide dismutase.
03:16
And this may account for 5 to
10% of your genetic cases.
03:19
Know that it exists and please make
sure that you memorize a familial form.
03:23
But most, most, are
idiopathic, unfortunately.
03:28
Clinical features:
Remember, motor, motor, motor.
03:31
It’s asymmetrical
weakness of hands.
03:34
So nonsymmetrical, early.
03:36
That’s important.
03:36
Pay attention to early manifestation.
03:39
Decreased muscle
strength and bulk.
03:41
Remember both upper and lower
motor neuron type of lesions.
03:45
Fasciculations, what
does that mean to you?
Involuntary contraction of
individual motor units.
03:51
Progressive muscle or muscular atrophy
to the point where the
patient may not even have
the ability to properly
contract their diaphragm.
04:00
Not good.
04:01
And respiratory arrest.
04:03
Look for a patient who also has
decreased ability to have a gag reflex.
04:09
Decreased muscle bulk especially
noticeable in the thenar eminence.
04:14
That’s an important
clinical feature.
04:17
Clinical features both
mixed upper and lower
motor neuron lesions
that we talked about.
04:22
Some patients have degeneration of lower
brain stem type of cranial nerve issue.
04:27
And may have progressive
bulbar palsy or bulbar “ALS.”
On electrophysiology, what
are we going to find?
Remember now,
you’re going to see as to what the
muscle activity is going to be like.
04:43
There are several disease-modifying treatments used in the management of ALS.
04:47
Riluzole has several potential mechanisms of action and has been shown
to slow functional decline and improve survival by about 2–4 months.
04:54
Edaravone is a free radical scavenger which reduces oxidative stress,
and sodium phenylbutyrate-taurursodiol is a histone deacetylase inhibitor which can reduce neuronal cell death.
05:05
Both of these may also slow the rate of functional decline.
05:09
There is not solid cure here,
just keep this one in mind.
05:12
It is FDA-approved.
05:14
Symptomatic and supportive treatments are
essentially what you’re going to do.
05:19
The course itself can be highly
variable from individual to individual.
05:23
That’s extremely true.
05:26
You can have some patients that have
ALS and you might not even know it
because they’re actually
functioning at a normal level.
05:34
Average lifespan, however,
upon diagnosis is 5 years.
05:39
So that’s extremely grim.
05:42
Summary:
Risk factors:
Male preponderance, genetic.
05:47
Preventive:
Really nothing that
we know of truly.
05:50
Signs and symptoms:
Weakness, atrophy,
fasciculations.
05:54
Motor, motor, motor
dysfunction only.
05:56
Upper and lower.
05:57
Remember fasciculations, individual
muscle fiber type of twitching.
06:02
I shouldn’t use the word
twitching, but contractions.
06:05
Mixed upper and lower motor
neuron type of issues.
06:08
Diagnostic workup, you’re going
to use electrophysiology
to absolute seek
decreased conduction.
06:14
MRI of the brain and spine,
serology, lumbar puncture
just to make sure that you
rule other things out.
06:20
Management:
Disease-modifying medications,
And we have supportive care being
essentially what you’re going to do.
06:29
We’ll come back to this picture
again and this time, once again,
as we go through this section,
you’ll get a better idea as to how
to orient yourself to the different
classifications of
neuromuscular diseases.
06:41
The first that we did was
amyotrophic lateral sclerosis
and there was a problem with
the motor neuron, wasn’t it?
And you had both upper and
lower motor neuron lesions.
06:51
Next topic is going to be peripheral
neuropathy, let’s take a look.
06:56
The pattern classification,
we call this radiculopathy,
involvement of the spinal nerve root.
07:03
Be familiar with the definition.
07:05
Radiculopathy
characteristically is painful.
07:10
At some point, we’ll get into our --
well, you’ve heard of brachial
plexus, obviously, or lumbar plexus.
07:17
So here, we’ll talk about
what’s known as plexopathy.
07:20
It’s a pretty interesting
name, isn’t it?
Either the brachial
or lumbosacral.
07:25
Mononeuropathy, involvement of a single
nerve as the name implies, mono-.
07:32
And then you have mononeuropathy
multiplex, what does that mean?
It’s very important.
07:36
Involvement of one nerve but in multiple,
multiple, locations or systems.
07:42
Mononeuropathy multiplex
versus mononeuropathy.
07:48
Let me give you an example.
07:49
You have a medium to small vessel
disease known as polyarteritis nodosa.
07:53
Polyarteritis nodosa.
07:56
And oftentimes, you’ll
find the complex,
the mononeuropathy multiplex.
08:04
We’ll talk about that
in greater detail.
08:07
Polyneuropathy:
As the name implies, multiple, symmetric
involvement of peripheral nerves.
08:13
Our topic, peripheral
neuropathy.
08:17
Usually in a length
dependent fashion.
08:20
We call this stocking-glove
type of distribution.
08:25
The pathologic classification
for peripheral neuropathy.
08:28
Axonal.
08:29
Characterized by degeneration of axon.
08:31
Demyelinating characterized
by loss of myelin.
08:34
Small fiber symptoms
where there’s neuropathic pain, loss
of pain and temperature sensation
or maybe even autonomic
dysfunction, peripheral neuropathy.
08:43
Or large fiber symptoms and
this then includes weakness,
diminished reflexes, loss of
vibration, joint position.
08:51
So we have small fiber
versus large fiber.
08:54
And here, once again, neuroanatomy
will come in very handy here.
08:58
Two different types of classifications.