Spinal muscular atrophy (SMA)
Spinal muscular
atrophy (SMA) most commonly affects infants and children and makes it difficult
to use the muscles. When your child has SMA, nerve cells in the brain and
spinal cord are damaged. The brain stops sending messages that control muscle
movement.
When this happens,
your child's muscles weaken and tighten, and children may have trouble
controlling their head movements, sitting unaided, and even walking. In some
cases, they may have difficulty swallowing and breathing as the condition
worsens.
There are different
types of SMA, and its severity depends on the type of child you have. There is
no cure, but treatment can improve some symptoms and, in some cases, help your
child live longer. Researchers are working to find new ways to fight the
disease.
Keep in mind that
every child or adult with SMA will have a different experience. No matter how
limited your child's movements may be, the disease does not affect his intelligence
in any way. They will still be able to make friends and chat.
Symptoms of SMA
Symptoms vary greatly
depending on the type of SMA:
Type 0.
This is the rarest and most severe form of SMA that develops during pregnancy.
Babies with this type of SMA move less in the womb and are born with joint
problems, weak muscle tone, and weak breathing muscles. Often they do not
survive due to breathing problems.
Type 1.
This is also a severe type of SMA. The child may be unable to support his head
or sit up without assistance. They may have flaccid arms and legs and trouble
swallowing.
What worries me most
is the weakness of the muscles that control breathing. Most children with SMA 1
do not live beyond the age of 2 due to breathing problems.
Stay in touch with
your healthcare team, family members, clergy, and others who can give you the
emotional support you need while your child struggles with this illness.
Type 2.
It affects children from 6 to 18 months. Symptoms range from moderate to severe
and usually affect the legs more than the arms. Your child may be able to sit
and walk or stand with help.
Type 2 is also called
chronic childhood SMA.
Type 3.
Symptoms of this type begin in children between the ages of 2 and 17 years.
This is the mildest form of the disease. Your child will probably be able to
stand or walk on their own, but may have trouble running, climbing stairs, or
getting up from a chair. Later in life, they may need a wheelchair to get
around.
Type 3 is also called
Kugelberg-Welander disease or juvenile SMA.
Type 4.
This form of SMA begins in adulthood. You may have symptoms such as muscle
weakness, muscle twitching, or trouble breathing. Usually only the arms and
legs are affected.
You will have
symptoms throughout your life, but you can keep moving and even improve with
the exercises you do with the help of a physical therapist.
It is important to
remember that there are many variations on how this type of SMA affects people.
For example, many people may continue to work for many years. Ask your doctor
about ways to meet other people with the same condition and find out what
you're going through.
Causes of SMA
SMA is a family
disease. If your child has SMA, it's because they have two copies of the broken
gene, one from each parent.
When this happens,
their body will not be able to produce a particular type of protein. Without
it, the cells that control muscles die.
If your child
receives the defective gene from only one of you, he will not have SMA, but he
will be a carrier of the disease. When your child grows up, he can pass on the
broken gene to his child.
Diagnosis of SMA
SMA can be difficult
to diagnose because the symptoms can be similar to other conditions. To help
you understand what's going on, your doctor may ask you:
- Has your baby missed any developmental milestones, such as holding their head up or rolling over?
- Does your child have trouble sitting or standing on their own?
- Have you seen your child have trouble breathing?
- When did you first notice the symptoms?
- Has anyone in your family had similar symptoms?
Your doctor may also
order tests to help make a diagnosis. For example, they may take a sample of
your child's blood to look for missing or broken genes that can cause SMA. Your
doctor may also order a blood test to check for creatine kinase. This is an
enzyme that is released from weakened muscles. High levels of creatine kinase
in the blood are not always harmful, but indicate possible muscle damage.
Other tests rule out
conditions with similar symptoms:
- Nerve tests such as an electromyogram. Your doctor places small patches on your
child's skin and sends electrical impulses through the nerves to see if they
send signals to the muscles.
- CT scan.
This is a powerful x-ray that takes detailed pictures of the inside of your
baby's body.
- Magnetic resonance imaging. It uses powerful magnets and radio waves to create
images of the organs and structures inside your baby.
- Biopsy of muscle tissue. In this test, the doctor removes muscle cells using a
needle in the muscle or through a small incision in your child's skin.
Questions for the doctor
- Have you treated others with this condition?
- What treatments do you recommend?
- Is there therapy that can help keep my child's muscles strong?
- What can I do to help my child become more independent?
- How can I get in touch with others who have family members with SMA?
Treatment of SMA
There are two drugs
for the treatment of SMA: nusinersen (Spinraza) and onasemnogen
abeparvovec-xyoy (Zolgensma). Both are forms of gene therapy that target genes
involved in SMA. The SMN1 and SMN2 genes instruct your body to make a protein
that helps control muscle movement.
- Nusinersen. This treatment corrects the SMN2 gene and allows it to make more proteins. It is used in children and adults with SMA. Your child's medical team will inject medication into the fluid around his spinal cord. Including preparation and recovery time, this can take at least 2 hours and will need to be done several times and then another dose every 4 months. Studies show that it helps approximately 40% of the people who use it, making them stronger and slowing down the disease.
- Onasemnogene abeparvovec-xioi. This includes replacing the problematic
SMN1 gene. It is used for children under 2 years old. Your child's healthcare
team will insert a small tube called a catheter directly into a vein in your
arm or hand. They will then send a copy of the SMN gene through a tube to a
specific group of motor neuron cells. This will only need to be done once. In
studies, the onasemnogen abeparvovec-xioi helped children with SMA reach
certain developmental milestones faster, such as the ability to control their
heads or sit without support.
In addition to gene
therapy, your doctor may suggest other ways to relieve symptoms:
- Breathing. In SMA, especially types 1 and 2, weak muscles prevent air from moving in and out of the lungs easily. If this happens to your child, they may need a special mask or mouthpiece. For serious problems, your child may use a machine to help them breathe.
- Swallowing and nutrition. When the muscles in the mouth and throat are weak,
babies and children with SMA may have trouble sucking and swallowing. In this
situation, your child may be malnourished and have difficulty growing. Your
doctor may suggest that you work with a nutritionist. Some babies may need a
feeding tube.
- Movement. Physical and occupational therapy, which includes regular daily exercise and activities, can help protect your child's joints and strengthen muscles. The therapist may suggest a leg splint, a walker, or an electric wheelchair. Special tools can control computers and phones, and help you write and draw.
- Back issues. When SMA begins in childhood, children may have a
curvature of the spine. The doctor may suggest that your child wear a back
brace while their spine is still growing. When they stop growing, they may
undergo surgery to fix the problem.
Caring for a child with SMA
There are many things
you can do as a family to help your child with some of the basic tasks of daily
life. A team of doctors, therapists, and support groups can help you care for your
child and give him the opportunity to maintain friendships and activities with
your family.
Your child is likely
to need constant care from different doctors. They may need to see:
- Pulmonologists, doctors who treat lungs
- Neurologists, specialists in nerve problems
- Orthopedists, doctors who treat bone problems
- Gastroenterologists, specialists in stomach disorders
- Nutritionists, experts in the way food affects your child's health
- Physical therapists, people trained in using exercise to improve your child's motion
This team can help
you make decisions about your child's health. It is important not to become
overwhelmed by the task of managing care. Look for support groups that allow
you to share your experience with others in a similar situation.
The prognosis depends
on when the symptoms started and how severe they are. If your baby has type 1,
a severe form of SMA, symptoms may appear from birth up to 6 months of age. In
general, most babies with this type of disease begin to show signs of the
disease at 3 months of age. You will begin to notice that their development is
delayed and they may not be able to sit or crawl.
While children with
this type usually don't make it past 2 years of age, with the help of your
doctors and support group, you can make life easier for them.
For other types of SMA,
doctors can relieve a child's symptoms for years, and in many cases, for life.
Keep in mind that every child or adult with SMA will have a different experience. A treatment plan tailored specifically for your child can help improve their quality of life.