 What Is ALS?
ALS — amyotrophic lateral sclerosis
— is a disorder of the motor neurons, nerve cells in the
brain and spinal cord that control the action of voluntary
muscles. In ALS, for reasons not yet completely understood,
these nerve cells gradually die. As they die, the nerve
fibers that travel from them to the muscles die, too, and
the muscles that normally receive signals from these nerve
fibers can no longer function.
ALS most often strikes adults in
late middle age (the mean age of onset is between 55 and
65). But there are people with ALS ranging from their teens
to their 80s. It usually starts in a leg or arm, with weakness,
stiffness or cramping. Sometimes, the trouble starts in
the mouth or throat, usually as difficulty forming words
with the tongue and lips, or with voice volume or quality.
Motor Neurons
Two kinds of motor neurons are affected
in ALS — the upper motor neurons, which are in the top part
of the brain, and the lower motor neurons, which are in
the brainstem (almost at the spinal cord) and the spinal
cord.
Upper motor neurons affect all of
the body’s voluntary muscles by sending chemical messengers
(neurotransmitters) to the lower motor neurons. They regulate
the activity of the lower motor neurons, which in turn send
neurotransmitters to the muscles.
Lower motor neurons in the brainstem
control voluntary muscles in the face, mouth, throat and
tongue. Lower motor neurons in the spinal cord control all
the other voluntary muscles of the body, such as those in
the limbs, trunk, head and neck, as well as the respiratory
diaphragm and other muscles used in breathing.
Symptoms
Dysfunction of these two types of
neurons can result in different kinds of symptoms. Loss
of lower motor neurons results in muscle weakness, atrophy
(loss of bulk), cramping and twitching.
Loss of upper motor neurons results
in muscle weakness, stiffness, slowness of movement, and
tightness, or spasticity.
|
In ALS, upper and
lower motor neurons degenerate. Upper motor neurons normally
send signals to lower motor neurons, which send signals to muscles. |
Since both kinds of neurons are
lost in ALS, all these symptoms may occur, but not necessarily
at the same time, and not in the same degree in each muscle.
Some muscles may be stiff and tight, while, at the same
time, others may become weak and soft.
Loss of limb strength and mobility
are, of course, serious concerns for the person with ALS
and his caregiver. However, loss of the muscles involved
in speaking, swallowing and breathing will pose the most
serious threats to health and well-being.
Many of the decisions you and the
person with ALS will make will come about because of changes
in these functions.
Unaffected Functions
On a positive note, many functions
remain intact throughout the course of ALS.
The intellect and the ability to
think and feel emotions continue to function throughout
the course of the disease.
In general, the so-called autonomic,
or automatic, functions remain intact. These include heart
function, digestion, urination and defecation, maintenance
of blood pressure and temperature, and so forth.
The senses, including touch, hearing,
vision and smell, also remain intact. Perception of pain
remains normal, but severe pain isn’t commonly a major part
of ALS.
Sexual function generally remains
normal. Bowel and bladder control usually are intact, even
in advanced disease, although constipation may occur because
of weak abdominal muscles and prolonged immobility in the
later stages.
The muscles that move the eyes,
even though classed as voluntary muscles, usually remain
functional throughout the illness.
This guide, and the many resources listed, will help you understand and care for your loved
one with ALS, and have as fulfilling a life together
as possible.
In ALS, upper and lower motor neurons
degenerate. Upper motor neurons normally send signals to
lower motor neurons, which send signals to muscles
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