Cause and Effects of Amyotrophic Lateral Sclerosis
Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease,
is a chronic progressive motor neuron disease with a poor prognosis which
eventually weakens and paralyzes the respiratory muscles. ALS can strike
anyone. It generally occurs between the ages of 20 and 90, with the incidence
normally increasing with age and peaking in the 60's and 70's. ALS causes
its victims to get weaker and weaker until they are completely paralyzed.
Amyotrophic lateral sclerosis attacks motor neurons of the brain which convey
messages throughout the body. When muscles do not receive these messages
they become weak and wither from lack of use, and as a result the patient
ALS may be present for some time before noticeable symptoms occur. The initial
signs and symptoms are usually dependent upon which muscles weaken first.
Early symptoms usually begin with alpha motor neuron involvement and then
progress to include cortical motor neuron involvement (Tidwell, pg 337-42).
Patients may begin tripping or falling, some lose the dexterity in their
hands and legs, and others find it difficult or near impossible to swallow
or breathe. Gradual weakening of muscles causes the disease to go unnoticed
for an extended period of time before visible symptoms become a concern.
As a result of this latent period, nearly all victims in one way or another
are handicapped when they become informed of having ALS. As the disease
continues to progress all voluntary muscles become useless, restricting
the individual from being able to move, eat, communicate, or breathe without
the assistance of a respirator. Involvement of the respiratory system is
inevitable and leads to respiratory failure, the usual cause of death in
this disorder. Treatment consists of preventing respiratory complications
and supporting lung function for as long as possible. In the slim instance
that the patient survives long enough for the disease to run its full course,
usually results in the person succumbing to complete paralysis.
ALS is not known to be a genetically linked disease, and generally strikes
people with no history of the disease in their families. Still there has
been approximately 5% of the patients who have had other family members
with ALS. Recent experiments dealing with genetic analyses of patients with
a familial, chromosome 21-linked form of ALS suggests that mutations in
the cytosolic copper/zinc superoxide dismutase (SOD1) gene is somehow linked
to the development of amyotrophic lateral sclerosis. Even though they have
been unable to identify any functional disturbances of SOD1 activity, it
is believed that altered free radical protection may be a leading contributor
to the destruction of motor neurons (Nutrition Reviews, pg.243-245). Mutations
in the human Cu/Zn SOD1 gene has been discovered in 20% of kindred with
familial ALS, and similar findings have linked a specific SOD1 mutation
with alterations in the neural cytoskeleton of patients with ALS (Tu, pg.3155-3160).
It is these mutations in the SOD1 gene that injures nerve cells by enhancing
the ability of its encoded enzyme to act as a peroxidase. A peroxidase oxidizes
and damages lipids, leading to a degeneration of the cell membrane and eventually
nerve cell death (Marx, pg.446-447). Plans to test antioxidants as a possible
preventative and therapeutic procedure for patients with ALS are in the
The cause of Amyotrophic Lateral Sclerosis is unknown. Presently ALS is
incurable, and only symptomatic treatment is available. There are currently
several major controversies concerning the possible role of immunological
factors, genetic factors, environmental toxins, and viral infection in pathogenesis.
These concepts must be considered in relation to what is known about the
disease in all its aspects, including epidemiological data, information
on the pathology of the disease, as well as the associated involvement of
other systems (Swash, pg.4-16). Scientists have been seeking a cause and
a cure for amyotrophic lateral sclerosis for more than 100 years. Only when
all this information is assimilated can full understanding of the disease,
and hopefully a logical approach to treatment and prevention, be achieved.
Kaplan, LM., Hollander, D. (1994, December). Respiratory dysfunction in
amyotrophic lateral sclerosis. Clinics in Chest Medicine, 15, 675-681.
Marx, J. (1996, January 26). Mutant enzyme provides new insights into the
cause of ALS. Science, 271, 446-447.
Mutations in the copper-and zinc-containing superoxide dismutase gene are
associated with "Lou Gehrig's disease." (1993, August). Nutrition
Reviews, 51, 243-245.
Schwartz, S. (1992, November). What do we really know about amyotrophic
lateral sclerosis? Journal of the Neurological Sciences, 113, 4-16.
Tidwell, J. (1993). Pulmonary management of the ALS patient. Journal of
Neuroscience Nursing, 25, 337-342.
Tu, Pang-Hsien., Raju, P., Robinson, K., Gurney, M. (1996, April 2). Transgenic
mice carrying a human mutant superoxide dismutase transgene develop neuronal
cytoskeletal pathology resembling human amyotrophic lateral sclerosis lesions.
Proceedings of the National Academy of Sciences of the United States of
America, 93, 3155-3160.
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