00:02
Now let's talk about some of the
etiologies of motor neuron diseases.
00:05
What causes motor neuron disease?
Well, we can divide this into things
that affect the upper motor neurons,
the lower motor neurons and both.
00:14
And certain conditions have a predilection
for various types of motor nerves.
00:19
In terms of upper motor neuron pathology,
here's a number of conditions that we
consider and include on the
differential diagnosis for those patients.
00:27
Hereditary spastic paraplegia is exactly
what it says, it's a hereditary disorder,
begins in often in middle age, it's
inherited, and patients develop slowly and
gradually progressive spasticity and paraplegia.
00:40
They're weak below the
waist at a certain spinal level,
it's motor predominant, there's not
typically sensory findings which is unique.
00:48
In terms of its spinal cord presentation,
patients become extremely spastic
and acn have difficulty walking and
ultimately often become wheelchair bound.
00:56
And unfortunately, there is no cure and supportive
care is the optimal treatment for those patients.
01:02
Primary lateral sclerosis is a variant
of ALS, it's a motor neuron variant
that presents with primarily
upper motor neuron symptoms.
01:10
Those patients don't have the
lower motor neuron pathology.
01:13
The pathology is primarily
in that first order motor nerve
and so patients present with
upper motor neuron findings.
01:20
Ischemic stroke is in the differential
for an upper motor neuron lesion.
01:23
Strokes affect the brain, that's
where the upper motor neurons are.
01:26
And so stroke patients can look in some respects like
they present with an upper motor neuron pathology
but the timeline of onset
should really give away a stroke.
01:36
It's acute, it's a fixed deficit.
01:38
Whereas in typical motor neuron pathology, we
see gradually progressive symptoms over time.
01:44
Spinal cord transection can present in this
way and typically that would be due to trauma,
which would be present on the history, and the
Brown-Sequard syndrome is a spinal cord disorder
that can present with prominent
upper motor neuron pathology.
01:56
We also see lower motor neuron
predominant conditions that look like
the lower motor neuron
variants of motor neuron disease.
02:03
Spinal muscle atrophy is an inherited disorder.
02:06
There are three types, one affecting
very young children, infants and neonates.
02:10
Other affecting young children and
then sometimes into adolescents or adults.
02:14
This is where there's degeneration of that
second order motor neuron, the lower motor neuron
and it degenerates over time.
02:20
Patients present with severe
weakness, difficulty walking,
fasciculations and atrophy -
lower motor neuron pathology.
02:28
Historically there had not been a
treatment for spinal muscle atrophy
and in the last 5 to 10 years,
there's been a new treatment.
02:34
Gene therapy that have revolutionized
the treatment of this condition
and really changed how we managed those patients.
02:40
In some states, testing for spinal muscle atrophy,
a mutation in the SMN gene is now
standard in terms of neonatal testing.
02:49
Distal hereditary motor neuropathies,
the motor neuropathies can present like
a lower motor neuron disorder.
02:56
Poliomyelitis is an infection that can
affect all of the nerve roots in the spinal cord
and cause a polyradiculoneuropathy
so poly- meaning all of the nerves,
-radiculo- meaning the nerve roots are
affected not the nerves out in the hands,
but the nerves in at the nerve root.
03:12
-neuropathy meaning many nerves are
affected and so patients present with a diffuse
lower motor neuron syndrome.
03:19
CSF testing would suggest a diagnosis of polio
and those patients would be managed symptomatically.
03:25
We don't see a lot of poliomyelitis these days but
in he era of he polio pandemic and epidemic,
this was a common cause of a
lower motor neuron syndrome.
03:34
Multifocal motor neuropathy is an
inflammatory disorder of the motor nerves,
Chronic inflammatory demyelinating
polyneuropathy, is also an inflammatory disorder,
and Guillain-Barre is an acute onset
ascending rapid paralysis that can present with
prominent motor symptoms and
mimic a lower motor neuron disorder.
03:54
And then there's some combined conditions.
03:56
Lesions secondary to trauma can cause upper
motor neuron findings below the level of the trauma.
04:01
Lower motor neuron findings at the
level of the trauma and is a consideration.
04:05
Compression of the spinal cord from malignancy
can again cause upper motor neuron findings
below the level of the tumor.
04:11
Lower motor neuron findings at the level of
the tumor and are important considerations.
04:16
And then we have the myeloneuropathies.
04:18
Vitamin B12 deficiency, copper deficiency and vitamin
E deficiency can present with a myeloneuropathy
or a combination of myelopathy, upper
motor neuron symptoms and neuropathy,
peripheral nerve nervous system symptoms,
but often we see sensory changes in those patients
which suggest alternative diagnoses
other than motor neuron disease