ALS is a progressive, degenerative disease of the nervous system. It
is one of a group of diseases, called motor neuron diseases (MND),
in which specialized nerve cells that control movement of the voluntary
muscles gradually cease functioning and die. These nerve cells,
called motor neurons, carry impulses from the brain to the brainstem
and the spinal cord. The impulses are then carried to the muscles.
The muscles respond to these messages by coordinated relaxation
or contraction corresponding to willed movement. In ALS and other
motor neuron diseases, motor neurons gradually deteriorate. Because
the nerve cells that stimulate them have died, the muscle tissues
waste away. This results in progressive muscle weakness, atrophy,
and often spasticity, or excess muscle tone. Only the motor neurons
are affected. Other nerve cells, such as sensory neurons that bring
information from sense organs to the brain, remain healthy.
Are there other names for ALS?
ALS, also known as motor neuron disease (MND), is commonly called Lou
Gehrig's disease for the famous New York Yankee's baseball player
who died of ALS in 1941. ALS is sometimes referred to as Charcot's
disease for the French neurologist Jean-Martin Charcot who identified
the disease in 1869.
Who gets ALS?
Most who develop ALS are between 40 and 70 years of age, although the
disease can strike at any age. Men are affected slightly more frequently
than women. ALS occurs throughout the world regardless of racial,
ethnic or socioeconomic status.
Some studies have identified areas that at certain times have appeared
to have greater than expected numbers of cases. This has occurred
in the past in the western Pacific islands and in parts of Japan
and Australia. Other areas in the continental United States have
been reported but have not stood up to careful epidemiological investigations.
How common is ALS?
More than 5,600 Americans are diagnosed with ALS each year or two new
ALS cases per 100,000 people (incidence). Approximately 35,000 people
at any given time are living with ALS in the United States or six
to eight people per 100,000 population (prevalence). The incidence
of ALS is close to that of multiple sclerosis and four times that
of muscular dystrophy.
What are the symptoms of ALS?
ALS strikes people in different ways and progression of the disease
is often irregular. Some of the early symptoms of ALS are:
- • Weakness or difficulty in coordination in one limb
- • Changes in speaking or swallowing
- • Unusual muscle twitches, spasms, or cramps
- • Unusual weight loss or loss of muscle bulk
The
symptoms and clinical features of the disease depend on the location
of the affected motor neurons. Speech and swallowing impairments
are called bulbar symptoms. They indicate that neurons in the brainstem
are affected. Weakness of the respiratory muscles, muscle weakness,
and loss of mobility in the arms and legs are called somatic symptoms.
They indicate spinal cord involvement. In classical ALS, a mixture
of upper and lower motor neurons are involved, with both bulbar
and somatic symptoms.
- Lower motor neuron symptoms -
Weakness and muscle wasting are common when lower motor neuron
involvement predominates. The patient or physician usually notices
fasciculation, or muscle twitching. Fasciculation is a sign
of muscle irritability, as the normal action of the lower motor
neuron on the muscle is impaired. The sole involvement of lower
motor neurons can be seen in a form of ALS called progressive
muscular atrophy. Fasciculation is described as "benign"
if there is no muscle weakness, atrophy, or impairment of motor
function. Fasciculation is described as "pathologic"
when it occurs in ALS with other symptoms.
- Upper motor neuron symptoms -
Spasticity, or stiffness, in the lower limbs, face, or jaw indicates
upper motor neuron involvement. Spasticity in the legs often
produces severe walking difficulties. The patient may complain
of heaviness, fatigue, stiffness, or lack of coordination of
any affected limb. Reflexes are very brisk, or exaggerated.
Outbursts of laughter or crying with minimal provocation can
occur. This is called emotional lability and is referred to
as a pseudo-bulbar affect. Both brisk reflexes and emotional
lability involve the inability to inhibit reflexes.
The
diagnosis of ALS is a "clinical diagnosis," meaning there
is no specific test that gives a definitive answer. Before a diagnosis
of ALS is confirmed, many tests must be administered to rule out
illnesses with symptoms that may mimic ALS. These may include an
MRI of the brain or spinal cord, an electromyography (EMG) study
of nerve and muscle function and a variety of blood and urine tests.
By evaluating these tests, the patient's medical history and performing
a complete neurological exam, the neurologist can usually reach
a definitive diagnosis.
It
is always recommended that patients seek a second opinion by a neurologist
experienced with ALS in order to decrease the possibility of an
incorrect diagnosis. In some cases a definitive diagnosis can be
made only after several months of observation and retesting.
What is the prognosis of ALS?
ALS progresses at different rates in each individual. The average survival
for someone affected by ALS is three to five years. A small percentage
of people have a very slow progression and live 10-20 years with
the illness at various levels of disability. Weakness of the bulbar
and somatic muscles produces a decline in speech, swallowing, and
limb strength and function. The ALS patient usually remains alert
throughout the course of the illness and retains normal sensation,
vision, and bowel function. Bladder function is impaired in 1% of
patients. Generally, ALS is not a physically painful condition.
Discomfort can result from immobility and joint contractures, a
shortening of muscles resulting in deformity. While most patients
do not have loss of intellectual function, some may have subtle
changes in mood, behavior, or personality. In a small minority of
patients, more significant changes in behavior and judgment suggest
a form of dementia.
Each
ALS patient is unique in regard to the rate and characteristics
of the progression of the disease. Although the clinical progression
can vary greatly, 50 percent of those diagnosed will succumb to
the illness within five years of the onset of symptoms
What causes ALS?
It is likely that there are several different causes of ALS. Two genes
have been identified that cause familial ALS. The causes of sporadic
forms of ALS are still unknown.
One hypothesis is that a group of gene mutations inherited together
predispose one to ALS such that a threshold is formed. Environmental
factors may "push" someone over the threshold so that
ALS symptoms occur. Both the predisposing genes and environmental
factors are unknown at this time.
Is there any treatment for ALS?
Many of the symptoms of ALS are treatable, but there are no drugs available
to cure the disease. Rilutek©, the first FDA-approved medication
for the treatment of ALS, has been shown to modestly increase lifespan.
Since it became available in 1996, two retrospective studies presented
at the 12th International Symposium on ALS/MND in 2001 indicated
that Rilutek© appears to have a greater impact on life expectancy
than was reported in initial drug trials.
The quality of life of patients with ALS can often be improved by various
treatments and interventions. Proper positioning, exercise, physiotherapy,
and medications can help keep patients comfortable. Patients with
significant bulbar involvement may require help to improve communication
or ensure safe and adequate nutrition. A gastrostomy (feeding) tube
may be suggested if there is recurrent pneumonia, high risk of aspiration
(inhaling food or liquids into the lungs), inadequate nutrition,
rapid weight loss, or extended feeding time. A wide range of devices
and techniques can address problems with communication. Ultimately,
ALS may result in respiratory decline, requiring consideration of
respiratory support, including non-invasive ventilation such as
a BiPAP (bilevel positive airway pressure), or a tracheotomy and
a ventilator.
Is ALS inherited?
Familial (genetic) ALS accounts for 10% of all ALS cases. ALS is considered
familial if there are two or more cases within the same bloodline.
If no family history exists, the disease is termed sporadic and
other family members are not thought to be at increased risk for
developing the disease.
Are there diseases similar to ALS?
Although it is the most serious, ALS is one of a number of diseases affecting
the nerve cell, or motor neuron. Some involve only upper motor neurons,
which run from the motor cortex of the brain to the brain stem and/or
spinal cord. Others involve lower motor neurons, which run from
the brain stem and spinal cord to muscles.
- Spinal muscular atrophy (SMA) -
SMA variations include childhood forms and a less frequent adult
form, which involves only the lower motor neurons. Inheritance
of adult SMA is autosomal recessive. Symptoms are generalized
weakness and muscle wasting with muscle twitching. Onset is
over 18 years into adulthood with variable progression and normal
life expectancy.
- Primary lateral sclerosis (PLS) -
PLS, a degenerative disease of the upper motor neurons only,
has symptoms of progressive spasticity, difficulty in walking,
and pseudobulbar affect. PLS affects the trunk, extremities
and bulbar muscles. PLS is not considered to shorten life expectancy
as it has a slow progression over the course of approximately
20 years. Because ALS may initially present with signs of only
upper motor neuron involvement, a diagnosis of PLS has the potential
to be reclassified as ALS if sufficient signs of upper and lower
motor neuron involvement are present.
- Spinal bulbar muscular atrophy (Kennedy's Disease) -
Symptoms are weakness and muscle wasting of the bulbar muscles
(throat and mouth) and skeletal muscles. Facial and muscle jumping
is common; breast development, infertility and testicular wasting
can occur. It usually affects only men. Females are carriers
who are usually asymptomatic or have a mild form. Onset is adulthood
with progression being slow and variable with normal lifespan.
Inheritance is X-linked recessive
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