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What are Motor Neuron Diseases?
Motor neuron diseases are neurodegenerative diseases that cause selective loss
of the nerve cells that directly connect the brain to muscles.
What
is ALS?
Amyotrophic lateral sclerosis (ALS, commonly called “Lou Gehrig's
disease” in
the U.S.) is the most common motor neuron disease in adults. ALS affects
both upper and lower motor neurons throughout the brain and spinal cord.
There are other forms of motor neuron disease that affect only the upper
motor neurons, affect only the lower motor neurons or have a restricted
distribution.
Demographics
Based on U.S. population studies, a little over 5,600 people
in the U.S. are diagnosed with ALS each year (approximately 15
new cases a day.) It is estimated that as many as 30,000 Americans
have the disease at any given time.Most people who develop ALS
are between the ages of 40 and 70, with an average age of 55 at
the time of diagnosis. However, cases of the disease do occur in
persons in their twenties and thirties. ALS is 20% more common
in men than in women. However with increasing age, the incidence
of ALS is more equal between men and women (www.ALSA.org).
Symptoms/Signs of lower motor
neuron disease
The primary symptom of lower motor neuron disease is weakness. The weakness
usually begins in one hand, one foot, or the tongue. As weakness becomes more
severe, involved muscles become smaller, and weakness spreads to other muscles.
Cramping and twitching of muscles are common; however, these symptoms are also
common in healthy people. Electromyography (EMG) is a test that is very sensitive
in detecting lower motor neuron disease.
Symptoms/signs of upper motor neuron disease
The primary symptoms of upper motor neuron disease are stiffness, slowness,
and clumsiness of movement. The symptoms usually begin in one limb or in
the mouth or throat, later spreading to other parts of the body. There are
no standard laboratory tests for upper motor neuron disease, but spasticity
(a specific type of stiffness), abnormally brisk tendon reflexes, Babinski's
sign, and diminished fine motor coordination are seen as diagnostic signs
on examination.
Physiology
1. Upper motor neuron
involvement in 3 of 4
- BulbarCervical Thoracic
- Lumbosacral
2. Lower motor neuron involvement
in 3 of 4
- Bulbar Cervical Thoracic
- Lumbosacral
3. Spread of symptoms over
time4. Absence of any
other explanation
Only lower motor
neuron involvement
- Kennedy's disease Spinal muscular atrophy Progressive muscular
atrophy variant of ALS Segmental motor neuron disease of
limbs
- Progressive bulbar palsy
Only upper motor neuron involvement
- Primary lateral sclerosis
- Progressive bulbar palsy
Genetics of ALS
The genetic mechanisms that cause ALS are only partially
understood. The only known cause of ALS is a mutation of a specific
gene, called the SOD1 gene. This mutation is believed to make a
defective protein that is toxic to motor nerve cells. The SOD1
mutation, however, accounts for only 1 or 2 percent of ALS cases,
or 20 percent of the familial (inherited) cases.
Relationship
between FTD and ALS
While estimates vary, it is now believed that
approximately 20% of ALS patients also have the signs
and symptoms of frontotemporal dementia. As a result,
patients may lack the ability to fully understand
the meaning of their illness, they may make poor
decisions about their clinical care, or they may
become agitated and difficult for caregivers who
are trying to help them. Other patients may have
trouble understanding language or communicating,
which is a separate problem from the articulation
problems that come with ALS. Some ALS patients have
had changes in their behavior or psychiatric problems
for years before they developed ALS, and only until
a full neuropsychological exam is completed does
the family understand that an FTD disease had begun
several years before. Researchers have found that
in addition to those patients who have a diagnosis
of FTLD, upwards of 50% of ALS patients have mild
changes in their ability to concentrate, focus on
multiple ideas or actions at one time, or make complex
judgments, called ‘executive
functioning’.
Treatment
Physicians have limited choices for treating ALS, and
the options that do exist have come into use within the last
10 years. Studies suggest that patients' length of survival
and quality of life are enhanced by night-time breathing assistance
early in the course of the disease and by aggressive application
of alternate feeding options to assure good nutrition once
swallowing becomes difficult. At this time, Riluzole® is
the only drug that has been approved by the FDA for treatment
of ALS. In clinical trials, Riluzole® has shown a slight
benefit in modestly increasing survival time (The
ALS Association).
Patients with co-morbid FTLD and ALS more often have difficulty
following treatment recommendations, perhaps because agitation,
poor insight and cognitive changes result in a refusal to comply
with physician’s recommendations. As a result, life span
is sometimes shortened in patients with both diseases. Specific
medicines have been found to be helpful to treat the agitation,
apathy and depression commonly seen in FTLD. See Education
section on FTD.
Caregivers
Caregiving for any patient with a debilitating illness can be both fulfilling
and exhausting, and caring for a loved-one with ALS is particularly challenging.
Patients’ needs change rapidly as the disease progresses, and impaired
communication can make caregiving more difficult. Caregivers for ALS patients
are also at increased risk for depression and stress because of the emotional
and economic stress of coping with an illness that requires expensive equipment
and will result in losing their loved one to this terminal disease.
When patients have both FTD and ALS caregiving becomes more difficult
for a variety of reasons. Patients often have poor insight into
their ALS symptoms, and as a result may disagree with family about
clinical changes, treatment recommendations and the need for necessary
equipment. They sometimes have trouble using a communication device
or making decisions regarding PEG and BiPAP, which are significant
life-sustaining measures. All of these problems confound an already
very difficult disease for families and health care providers. Resources
for caregivers can be found at a variety of websites:
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