Signs and Symptoms

Each child with spinal muscular atrophy (SMA) may experience symptoms differently. There are three main types of SMA defined by their symptoms and the time in which they first develop. The three forms of SMA and their symptoms are:

• Acute Infantile SMA (Type I)

  Also known as Werdnig-Hoffman disease, this form of SMA is the most severe. Some children develop the disease before birth. Mothers may notice that during the last three months of pregnancy, fetal movements are very weak. The majority of children with this form of the disease will experience symptoms before eight months of age. The condition primarily affects the muscles that control chewing and swallowing, chest wall muscles, and arm and leg muscles. Symptoms are typically severe and may include hypotonia or diminished muscle tone, muscle weakness, swallowing and feeding difficulties, respiratory problems and pneumonia. Quivering of the tongue, a condition called tongue fasciculation, also may occur. Children with this form of SMA face a difficult battle and many die from recurrent respiratory infections by within the first year of life. However, with new therapies, some children live into their teens or early adulthood.

• Chronic Infantile SMA (Type II)

  This form of SMA is less severe than acute infantile and usually progresses slowly. Symptoms normally develop between 6 to 18 months of age. Children with chronic infantile SMA may sit independently, but need support to walk or stand. Other symptoms may include respiratory problems, hypotonia or diminished muscle tone, decreased or absent deep tendon reflexes and involuntary contractions or twitching of groups of muscles called fasciculations. Some children may need a wheelchair and develop curvature of the spine called kyphoscoliosis and other orthopedic problems.

• Juvenile SMA (Type III)

  This form of SMA is also known as Kugelberg-Welander disease. Symptoms normally appear later than the other two forms, occurring between 2 and 17 years of age. The severity of the condition varies but generally progresses slowly. While some children may not walk or stand on their own, others may walk independently. Children with this form of SMA rarely experience respiratory or swallowing problems but may experience weakness in the shoulders, hips, thighs and upper back.

Diagnosis

Your doctor will conduct a thorough physical exam of your child, as well as a family history. These are very important steps in making a diagnosis of spinal muscular atrophy (SMA) and in understanding your child's pattern of symptoms. To make a definite diagnosis and rule out other disorders, your doctor will recommend tests that may include:

• Genetic Testing

  Over the past decade, the genetic defects underlying SMA have been identified. Two genes that contribute to SMA are the "survival motor neuron gene (SMN)" and the "neuronal apoptosis inhibitory protein gene (NAIP)." In over 95 percent of patients with SMA, changes in the SMN gene are detected. Although we don't fully understand how the gene abnormality produces the disease, the discovery of the SMN gene has allowed doctors to make a definite diagnosis of SMA, provide specific genetic counseling to those affected as well as to SMA carriers, and has led to a number of research projects involving patients to test new treatments.

• Electrodiagnostic Tests

  This test consists of two parts -- nerve conduction studies and electromyography (EMG). During nerve conduction studies, electrodes are placed on the skin over a peripheral motor or sensory nerve. A small electric shock is emitted that may cause mild discomfort. This electrical impulse stimulates sensory and motor nerves and a recording is made from the electrodes to see how much of the impulse reaches the nerve and how fast the electricity is carried.

  EMG involves inserting a needle electrode through the skin to measure the bioelectrical activity of muscles. It also can determine if peripheral nerves have been damaged.

• Muscle and Nerve Biopsy

  A muscle biopsy was commonly used in the past to diagnosis of SMA and may be necessary if genetic testing fails to confirm a diagnosis. During this procedure, a small sample of muscle and nerve tissue is surgically removed from a patient. The sample is examined to see if the tissue shows signs of the disease.

Treatment

Patients with spinal muscular atrophy (SMA) require ongoing, specialized care from our team of experts, including neurologists, orthopedists, pulmonologists and surgeons. Although there is no cure for the disease, its symptoms and complications can be successfully managed to help improve a patient's quality of life. Several medications are being studied for this disease. Treatments may include:

• Medications

  Riluzole blocks certain proteins in the central nervous system that may cause damage to nerve cells. This drug is prescribed for adults with amyotrophic lateral sclerosis (ALS), also called Lou Gerhig's disease, which is similar to SMA. Preliminary studies have suggested a benefit for some children with SMA, but doctors believe that more studies must be completed before the benefits for children are confirmed.

  Hydroxyurea, a chemotherapeutic agent, and valproic acid, also known by the brand name Depakote, are being studied for possible benefits in children with SMA. Due to potentially serious side effects, it is recommended that you discuss these medications with a specialist before they're given to your child.

• Nutrition

  Children with type I and some with type II SMA have special nutrtional needs because of chewing and swallowing problems. A special X-ray study, called a swallowing study and cine esophagram, may help determine the foods that are dangerous to your child. Our therapists will work with you and your child to ensure your child receives adequate nutrition. Children who are unable to swallow liquids and semi-solids may need a gastrostomy tube, which allows nourishing liquids to flow directly to the stomach. These tubes are inserted by a surgeon or gastroenterologist.

• Physical Therapy

  Muscle weakness in the legs and arms may cause a child to experience tightness in the joints, called contractures. Our physical therapists can teach your child special range-of-motion exercises to keep muscles as flexible and mobile as possible. Night splints on ankles and wrist also may help prevent contractures or joint tightness.

• Mobility Aids:

  Children with type I and type II SMA typically are unable to stand or walk independently and require an electric wheelchair for increased mobility. Many children can safely operate a wheelchair by age 2 or 3.

• Respiratory support:

  Children with SMA have a high risk of developing respiratory problems. Many respiratory support therapies are recommended to help prevent complications. Treatments may include:

  • Regular breathing exercises
  • Yearly immunizations to avoid preventable illnesses, such as influenza
  • Supplemental oxygen, usually delivered through a small nasal tube.
  • Breathing support therapies may be necessary when breathing muscles don't function properly. Devices such as "negative pressure" ventilators and external positive airway pressure support systems can help children breathe. Positive airway systems use a gently placed, but snug mask, to deliver air directly to the nostrils.