Loss of Strength / Weakness
Weakness refers to loss of muscle strength where people can't move a muscle normally
despite trying as hard as they can. However, the term is often misused when people
with normal muscle strength say they feel weak when they feel tired or when their
movement is limited because of pain or joint stiffness.|
For a person to intentionally move a muscle (called a voluntary muscle contraction),
the brain must generate a signal that travels a pathway from:
||Through nerve cells in the brain stem and spinal cord
||Through nerves from the spinal cord to the muscles (called
||Across the connection between nerve and muscle (called a
Also, the amount of muscle tissue must be normal, and the tissue must be able to contract
in response to the signal from the nerves. Therefore, true weakness results only when one
part of this pathway (brain, spinal cord, nerves, muscles, or the connections between
them) is damaged or diseased.
Weakness may develop suddenly or gradually. Weakness may affect all of the muscles in the
body (called generalized weakness) or only one part of the body. For example, depending on
where the spinal cord is damaged, spinal cord disorders may cause weakness only of the legs.
Symptoms depend on which muscles are affected, like when weakness affects muscles
of the chest, people may have difficulty breathing or when weakness affects muscles that
control the eyes, people may have double vision. Complete muscle weakness causes paralysis.
People may have other symptoms depending on what is causing the weakness. Weakness is often
accompanied by abnormalities in sensation, such as tingling, a pins-and-needles sensation,
Muscle weakness is very common in multiple sclerosis (MS) and can occur in any part of the
body. It can range from specific parts that are always tired or become tired easily to your
entire body. You can have a great nights rest and when you awaken, you feel as if you just
ran a marathon or stayed up all night. There are many factors that can be causing this
but the end result is that you are "wiped out" from the start of the day. When you are
already tired, it becomes very difficult to stay active or even exercise. Just remember
that you have to work hard and stay going because either you use it or loose it.
Causes of Weakness
Because malfunction in the same part of the signal pathway causes similar symptoms
regardless of cause, the many causes of muscle weakness are usually grouped by the
location of the cause. That is, causes are grouped as those that affect the brain,
spinal cord, peripheral nerves, muscles, or connections between nerves and muscles.
However, some disorders affect more than one location.
Causes differ depending on whether weakness is generalized or affects only specific
muscles. The most common causes of generalized weakness are:
||A decrease in general physical fitness (called deconditioning),
which may result from illness and/or a decrease in physical reserves
(frailty), such as muscle mass, bone density, and the heart's and
lungs' ability to function, especially in older people
||Loss of muscle tissue (wasting or atrophy) due to long
periods of inactivity or bed rest, as occurs in an ICU
||Damage to nerves due to a severe illness or injury,
such as severe or extensive burns
||Certain muscle disorders, such as those due to a low
level of potassium (hypokalemia), consumption of too much alcohol,
or use of corticosteroids
||Drugs used to paralyze muscles, like those to keep
people from moving during surgery or while on a ventilator
The most common causes of weakness in specific muscles are:
||Strokes (the most common cause of weakness affecting
one side of the body)
||A pinched nerve, as occurs in carpal tunnel syndrome
||A ruptured or herniated disk in the spine
||Pressure on or compression of the spinal cord, as can
result from cancer that has spread to the spinal cord
Many people report weakness when their problem is actually fatigue. Common causes
of fatigue include a severe illness, cancer, a chronic infection (such as HIV infection,
hepatitis, or mononucleosis), heart failure, anemia, chronic fatigue syndrome,
fibromyalgia, mood disorders (such as depression), and MS.
The first step in managing weakness effectively is to determine what is most likely
of muscles results from lack of use. Often in MS, due to fatigue,
pain, imbalance, or other symptoms, a person's overall activity
level is reduced. Lack of activity will cause the muscles affected
by MS, as well as those that are not affected by the disease, to
become weak. For this type of weakness, progressive resistive
exercise with weights can be very effective. A physical therapist
can recommend a weight-training program that fits abilities and
to the nerve fibers (demyelination) in the spinal cord and brain
that stimulate the muscles can also cause weakness. The muscles
are not receiving the nerve impulses they require in order to work
effectively – which often results in a reduction in endurance.
Because the source of this type of weakness is impaired nerve
conduction, weight training to strengthen the affected muscles isn't
effective and may even increase feelings of weakness and fatigue.
The recommended strategy is to maintain the tone of those muscles
that are not receiving adequate nerve conduction with regular use,
while working to strengthen the surrounding muscles that are
receiving adequate conduction. A physical therapist can work to
identify the sources of your weakness and recommend appropriate
strategies to manage them.
Weakness in the legs, ankles and feet can interfere with walking. Management
strategies to address walking problems include exercise, assistive devices and
medication. Weakness in the upper body and arms can interfere with activities
of daily living and self-care. Occupational or physical therapists can recommend
appropriate exercises for your arms and hands, as well as tools and devices to
assist with activities in the home and at work.
Many will lose muscle strength in the arms and legs as the disease progresses.
Muscle weakness can involve the extremities (arms and legs) on one side of the
body (hemiparesis), both legs (paraparesis), or all four extremities (quadraparesis).
Muscles in the affected area may tighten (spasticity) and contract spontaneously
(spasm or clonus). The loss can range from reduced dexterity to paralysis of an
arm or leg. The loss of muscle strength occurs not only in the for of relapses,
but also as a gradual process without recovery. Depending on the severity, an
assistive devise may be required.
Respiration or breathing is primarily under the control of the autonomic nervous
system (ANS) which is the part of the central nervous system (CNS) that controls
vital functions such as heartbeat and respiration without conscious thought.
It's unusual for MS to affect the ANS and therefore uncommon for breathing
problems to occur in MS as a direct result of loss of autonomic control. If
breathing problems occur suddenly, it's imperative to see your doctor
immediately or go to the emergency room since this may indicate infection or
some other problem.
Weakness of the ventilatory muscles can begin early in the disease. In MS, the
most common cause of respiratory problems is loss of muscle strength and
endurance. Just as a person can experience muscle weakness in the arms or legs,
weakness can occur in the ventilatory muscles of the chest and abdomen that are
involved in breathing. Just like weakness in the other parts of the body,
weakness of the ventilatory muscles can begin to occur early in the disease
course and gradually worsen over time.
Certain medications may also contribute to respiratory problems such as
tranquilizers, muscle relaxants, and opioid analgesics, can depress breathing.
The use of these medications should be carefully monitored in anyone with a
history of respiratory distress or swallowing problems.
Respiratory changes can also contribute to other problems. People with weakened
ventilatory muscles have to work harder to inhale and exhale. This extra effort
can be quite tiring, particularly for people who already experience a significant
amount of MS fatigue. Respiratory problems can also interfere with the process of
speech and voice production making it much more difficult and tiring for people
to carry on a conversation or speak loudly enough to be heard.
Testing Muscle Strength
First, doctors try to determine whether people are weak or simply tired. If people
are weak, doctors then determine whether the weakness is severe enough or worsening
quickly enough to be life threatening.
In people with weakness, the following symptoms are cause for concern:
||Weakness that develops over a few days or less
||Difficulty raising the head while lying down
||Difficulty chewing, talking, or swallowing
||Loss of the ability to walk
Doctors test muscle strength by asking the person to push or pull against resistance
or to do maneuvers that require strength, such as walking on the heels and tiptoes
or rising from a chair. Sometimes weakness is evident when a person uses one limb
more than another (for example, when swinging the arms while walking or when holding
the arms up with the eyes closed). Knowing which body parts are weak (the pattern of
weakness) can help doctors identify what the problem is.
MS can involve the nerves responsible for involuntary actions of the bladder and
intestines. Those with MS may often have constipation and urinary retention.
These symptoms may lead to other complications, such as infections of the
bladder, kidney, or blood. Dysfunction in the workings of the bladder or bowels
occurs in up to 80% of people with MS.|
Bladder dysfunction in MS happens when nerve signals to the bladder and urinary
sphincter (the muscles surrounding the opening to the bladder) are blocked or
delayed because of lesions on the spinal cord. The dysfunction can be for two
reasons: the bladder is spastic, so it isn’t holding the urine, or the bladder
isn’t emptying all the way, because the sphincter is spastic (contracting when
it's supposed to be relaxing to let out the urine, or vice versa).
If bladder dysfunction is left untreated, it can cause permanent damage to the
urinary tract. This happens when there's incomplete emptying of the bladder and
urine is retained, resulting in both urinary tract infections and formation of
stones from minerals which collect. Constantly leaking urine can result in skin
breakdown and infection. In addition, bladder dysfunctions often result in
people avoiding socializing and restricting their normal daily activities.
Bladder symptoms can appear as:
There is an urge to urinate, but it takes a long time to begin to urinate or
it's difficult to keep the urine flowing. Sometimes, the attempt is even "dry,"
meaning no urine is released at all.
The need to urinate comes on suddenly and strongly and may be accompanied by
an uncomfortable "full" feeling in the bladder.
There's a need to urinate much more often than usual. This often happens
at night, causing sleep disturbances.
This can either feel like a sudden urge to urinate, followed by the flow
starting immediately before there's a chance to react, or dribbling or leaking
with no warning or sensation.
Bowel symptoms usually manifest as constipation, although diarrhea and
incontinence can also occur. Many of these types of symptoms can be managed with
medications, combined with modifications in diet, fluid intake and habits.
Dysfunction occurs in almost two thirds of patients during the disease course.