Muscle Weakness,
Fatigue and
Spasticity
INDIRECT CAUSE
Physiology
Anatomy
There is no cure for ALS
and is normally fatal within
3-7 years. Cause of death
mostly respiratory failure
due to muscle atrophy
Patient suffers from Amyotrophic
Lateral Sclerosis (ALS)
Patient likely suffers from familial ALS
Only 5-10% of ALS patients have this type
Brother was a confirmed ALS sufferer and
father likely had the disease as well
Most common type of ALS is sporadic
(90-95% of cases)
Can affect anyone, anywhere
Environmental factors may affect sporadic ALS
- smokers are at higher risk
- environmental toxins (more research required here)
- miliary service. Patient served in Gulf War
While not completely understood, military service
affects likelihood of contracting ALS. Suspected
due to chemicals, injuries or intense exertion.
DIRECT CAUSE
Descending tracts of spinal cord
Motor neurons (found in descending tracts)
are deteriorating and are no longer sending
messages to muscles and therefore
the muscles cannot function.
Photo above shows a good overview
of neural messages between
the brain, spinal cord and muscles.
Please focus on the red line. Upper
motor neuron begins in the brain and
travels to spinal cord. Lower motor
neuron travels from spinal cord to
skeletal muscle.
Both Upper and lower motor
neurons appear to be affected by
ALS.
Brain's Largest and uppermost
portion is called cerebrum
Cerebrum is divided into two
hemispheres left and right
divided in the middle by a
longitudinal fissure
Cerebrum is also comprised of
raised bumps called gyri and
indentations called sulci
Gyri and Sulci increase the
surface area of the brain which
is very important as it allows
more neurons to be packed
inside the brain and process
more information
An important sulcus that separates frontal
and parietal lobes of the brain and is called
the central sulcus
Anterior to central sulcus is
precentral gyrus and posterior is
the postcentral gyrus
Cerebrum divided into 5 lobes
frontal lobe
parietal lobe
occipital lobe
insula
Photo above shows locations
of lobes with the exception of
insula which is deep to the
other lobes and not shown.
Lobes will be described in further
detail in physiology section
Spinal cord
White Matter
Superficial areas of
spinal cord are filled with
white matter. These are the
myelinated axons of
the neuron cells
Grey Matter
Gray Matter in the spinal
cord is organized into
butterfly shaped patterns
known as gray horns.
Dorsal Gray Horns
Found on the posterior
side of the spinal cord
Contains interneurons
Ventral Gray Horns
Found on the anterior
side of the spinal cord
Contains motor neurons
(somatic)
Lateral Gray Horns
These are lateral to the
dorsal and ventral gray
horns
Contains autonomic
motor neurons
Central Canal
found in the center
of the gray horns and
contains the cerebrospinal
fluid
Dorsal Root
bundle of sensory nerves
Dorsal Root Ganglion
Enlargement along the dorsal
root where sensory neuron cell bodies
are found
Ventral Root
bundle of motor neurons
WHITE MATTER
Structures of Spinal Cord
made up of myelinated
axons
ADDITIONAL ANATOMY
INVOLVED IN THE PROCESS
OF MOVEMENT
Neuron Structures of
Spinal Cord
GRAY MATTER
Interesting facts about ALS
Approximately 2 out of every 100,000
people in the US have ALS.
Cowboys stadiums holds 100,000
people as a point of reference.
Amyotrophic Lateral Sclerosis got it name as follows:
A - (not), Myo (muscle) trophic (nourishment)
Lateral - for the parts of the spinal cord where the
white matter tracts are found
Sclerosis - scarring or hardening of the nerves affected
In the US, ALS is also known as
Lou Gehrig's Disease after a famous
hall of fame baseball great who played
17 seasons with the New York Yankees.
Sadly, Mr. Gehrig contracted and
died from this disease.
Stephen Hawking a world famous
physicist lived with ALS for 55
years and is considered to most
certainly be an outlier in life
expectancy for this disease
To raise awareness for this fatal
and cruel disease, Pete Frates, who had ALS
began an ice bucket challenge in 2014.
Through this campaign, $220 million
was raised for ALS research. In July
2019 he and his family attended
a dedication at Boston College to the
Pete Frates Center, Indoor Training
Facility.
Eventually muscles die away
because they are not activated
Lateral Gray Horns
Contain Visceral motor neurons
which send instructions to non
voluntary muscles
Ventral Gray Horns
Contain somatic motor
neurons controlling skeletal muscles
Dorsal Gray Horn
Interneurons that process information
received by both somatic and sensory
neurons
Ascending Tracts
These neurons travel UP
to the brain. These are always
sensory neurons
Descending Tracts
These neurons travel down
from the brain and are
(skeletal) motor tractsRE
Some ascending tracts
have only 2 orders as they do not
go beyond the thalamus such as the
Spinocerebellar tract
Spinothalamic tract
is a good example of an
ascending neuron with 3 orders
3 neurons
2nd order Neurons
- live in spinal cord. These
are the interneurons in the
dorsal horn in the gray matter and
send information to the thalamus
3rd order Neurons
- neuron in the thalamus
that connects with the cerebral
cortex (to the relevant sensory
homonculus in the post central
gyrus of the parietal lobe)
1st order Neurons
- has receptors and collects
information and sends to spinal cord
2 neurons
Upper Motor Neuron
- in the brain or brainstem
Lower Motor Neuron
- the neuron that synpses
with the muscle
Through studies, it
has been determined that
ALS causes progressive
degeneration in both the
upper and lower motor neurons
Example #2 is the Vestibulospinal
Tract. Known as an INDIRECT motor tract
as the decision to move comes from brain
stem and is involved in more basic
involuntary functions to keep you breathing
and balanced (alive)
Example of a descending
tract is the Corticospinal tract.
Known as a DIRECT motor
tract as the movement directions
come from the brain and are therefore
voluntary.
Basal Nuclei
Grey matter areas found
deeper in the brain than cerebral
cortex gray matter. They smooth out
unwanted movements
The Cerebellum
Assists with skeletal
muscle movement and
enables smooth coordinated
movements by comparing what
should be happening (from brain)
with what is happening (from sensory
information) and making adjustments
Precentral Gyrus
This is the primary motor
area of the brain and regulates
many of the body's motor functions.
Contains the motor
homunculus which is a
motor map of the body.
The size of the body part
in the motor homunculus
dictates how many motor
neurons leave the brain
to go to that part of the
body. This dictates
the variety of movements
of that body part.
This picture gives a
good visual of the various
sizes of body parts found in
the motor homunculus
Two basal nuclei disorders
include:
- Parkinson's disease leading to
tremors - Tourette's syndrome due to
shorter-lived inactivation of the
basal nuclei leading to short muscle
spasms often seen has quick unwanted
contractions of facial muscles. Can be vocal
Muscular System
Patients of ALS suffer
from muscle cramps, spasms,
spasticity and pain
Digestive System
Due to difficulties swallowing
which development because of
muscular impacts, patients
nutritional intake and digestive
system functions are affected
Nervous System
ALS is a nervous system
disorder that manifests as
degeneration of motor neurons
Limbic system
This cruel disease is likely
to cause depression in ALS
patients since there is no
cognitive degeneration and
the patient is fully aware of the
muscular death of their body
Rilutek can be prescribed
to slow the progression of neuron
degeneration.
Radicava is a second
drug prescribed and known
to slow the progression of the
disease
Muscle relaxants
are typically prescribed
to control muscular issues
and anti-epileptic drugs have
been found beneficial in pain
management of ALS patients
Some medications otherwise
used to treat depression,
Parkinson's disease and
GI ulcers have shown some
effectiveness in mitigating
some swallowing difficulties
Respiratory System
Since the muscular
system directly impacts the
respiratory system
(ie. diaphgram and both internal
and external intercostal muscles)
ALS patients will eventually lose
their ability to breath on their own.
Eventually the patient will
require a ventilator to
assist with breathing.
Specifically the amygdala
(controls fear and anger), the
hippocampus and parts of the
thalamus are involved in depression.
Anti-depressants are
prescribed and these will
often help with sleep disorders
as well.