Locations Main Campus: Chesterfield, MO 63017   |   Locations
314-434-1500 314-434-1500   |   Contact Us

Multimedia Encyclopedia

BACK
TO
TOP
 
E-mail Form
Email Results

 
 
Print-Friendly
Bookmarks
bookmarks-menu

Spinal muscular atrophy

Werdnig-Hoffmann disease; Kugelberg-Welander disease

 

Spinal muscular atrophy is a group of disorders of the motor neurons (motor cells). These disorders are passed down through families (inherited) and can appear at any stage of life. The disorder leads to muscle weakness and atrophy.

Causes

 

Spinal muscular atrophy (SMA) is a collection of different motor nerve diseases. Grouped together, it is the second leading cause of hereditary neuromuscular disease, after Duchenne muscular dystrophy .

Most of the time, a person must get the defective gene from both parents to be affected. The most severe form is SMA type I, also called Werdnig-Hoffman disease. Infants with SMA type II have less severe symptoms during early infancy, but they become weaker with time. SMA type III is a less severe form of the disease.

In rare cases, SMA begins in adulthood. This is the mildest form of the disease.

A family history of spinal muscular atrophy in an immediate family member (such as brother or sister) is a risk factor for all types of the disorder.

 

Symptoms

 

Symptoms of SMA are:

  • Infants with SMA type I are born with very little muscle tone, weak muscles, and feeding and breathing problems.
  • With SMA type II, symptoms may not appear until age 6 months to 2 years.
  • Type III SMA is a milder disease that starts in childhood or adolescence and slowly gets worse.
  • Type IV is even milder, with weakness starting in adulthood.

Often, weakness is first felt in the shoulder and leg muscles. Weakness gets worse over time and eventually becomes severe.

Symptoms in an infant:

  • Breathing difficulty, leading to a lack of oxygen
  • Feeding difficulty (food may go into the windpipe instead of the stomach)
  • Floppy infant (poor muscle tone)
  • Lack of head control
  • Little movement
  • Weakness that gets worse

Symptoms in a child:

  • Frequent, increasingly severe respiratory infections
  • Nasal speech
  • Posture that gets worse

With SMA, the nerves that control feeling (sensory nerves) are not affected. So, a person with the disease can feel things normally.

 

Exams and Tests

 

The health care provider will take a careful history and perform a brain/nervous system (neurologic) examination to find out if there is:

  • A family history of neuromuscular disease
  • Floppy (flaccid) muscles
  • No deep tendon reflexes
  • Twitches of the tongue muscle

Tests that may be ordered include:

  • Aldolase blood test
  • Erythrocyte sedimentation rate (ESR)
  • Creatine phosphate kinase blood test
  • DNA testing to confirm diagnosis
  • Electromyography (EMG)
  • Lactate/pyruvate
  • MRI of the spine
  • Muscle biopsy
  • Nerve conduction
  • Amino acid blood tests
  • Thyroid-stimulating hormone (TSH) blood test

 

Treatment

 

There is no treatment to cure the weakness caused by the disease. Supportive care is important. Breathing complications are common in the more severe forms of SMA. To help with breathing, a device or machine called a ventilator may be needed.

People with SMA also need to be watched for choking. This is because the muscles that control swallowing are weak.

Physical therapy is important to prevent contractions of muscles and tendons and abnormal curvature of the spine ( scoliosis ). Bracing may be needed. Surgery may be needed to correct skeletal deformities, such as scoliosis.

 

Outlook (Prognosis)

 

Children with SMA type I rarely live longer than 2 to 3 years because of respiratory problems and infections. Survival time with type II is longer, but the disease kills most of those who are affected while they are still children.

Children with type III disease may survive into early adulthood. But, people with all forms of the disease have weakness and debility that gets worse over time. Adults who develop SMA often have a normal life expectancy.

 

Possible Complications

 

Complications that may result from SMA include:

  • Aspiration (food and fluids get into the lungs, causing pneumonia)
  • Contractions of muscles and tendons
  • Heart failure
  • Scoliosis

 

When to Contact a Medical Professional

 

Call your provider if your child:

  • Appears weak
  • Develops any other symptoms of spinal muscular atrophy
  • Has difficulty feeding

Breathing difficulty can rapidly become an emergency condition.

 

Prevention

 

Genetic counseling is recommended for people with a family history of spinal muscular atrophy who want to have children.

 

 

Open References

References

Darras BT, Markowitz JA, Monani UR, De Vivo DC. Spinal muscular atrophies. In: Darras BT, Jones R, Ryan MM, De Vivo DC, eds. Neuromuscular Disorders of Infancy, Childhood, and Adolescence . 2nd ed. Philadelphia, PA: Elsevier; 2015:chap 8.

Rudnik-Schoneborn S, Zerres K. Spinal muscular atrophies. In: Rimoin DL, Korf BR, Connor JM, Pyeritz RE, eds. Emery and Rimoin's Principles and Practice of Medical Genetics . 6th ed. Philadelphia, PA: Elsevier; 2013:chap 128.

 
  • Superficial anterior muscles

    Superficial anterior muscles - illustration

    Superficial muscles are close to the surface of the skin. Muscles which lie closer to bone or internal organs are called deep muscles.

    Superficial anterior muscles

    illustration

  • Scoliosis

    Scoliosis - illustration

    Abnormal curvature in the spine is known as scoliosis, and generally begins just at the onset of puberty and progresses during the period of rapid growth. Most junior high schools routinely screen for scoliosis because, if caught early, progressive spine curvature can be prevented. Scoliosis affects girls much more frequently than boys.

    Scoliosis

    illustration

    • Superficial anterior muscles

      Superficial anterior muscles - illustration

      Superficial muscles are close to the surface of the skin. Muscles which lie closer to bone or internal organs are called deep muscles.

      Superficial anterior muscles

      illustration

    • Scoliosis

      Scoliosis - illustration

      Abnormal curvature in the spine is known as scoliosis, and generally begins just at the onset of puberty and progresses during the period of rapid growth. Most junior high schools routinely screen for scoliosis because, if caught early, progressive spine curvature can be prevented. Scoliosis affects girls much more frequently than boys.

      Scoliosis

      illustration

    A Closer Look

     

      Talking to your MD

       

        Self Care

         

          Tests for Spinal muscular atrophy

           
             

            Review Date: 1/5/2016

            Reviewed By: Joseph V. Campellone, MD, Division of Neurology, Cooper University Hospital, Camden, NJ. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

            The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

             
             
             

             

             

            A.D.A.M. content is best viewed in IE9 or above, Firefox and Google Chrome browser.



            Content is best viewed in IE9 or above, Firefox and Google Chrome browser.