Spinal muscular atrophy

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Superficial anterior muscles

Werdnig-Hoffmann disease

Infants with SMA type I are born with very little muscle tone, weak muscles, and feeding and breathing problems. With SMA type III, symptoms may not appear until the second year of life.

Often, weakness is first noted in the shoulder muscles and proximal leg muscles. Weakness gets worse over time and will eventually become severe.

Symptoms in an infant:

• Breathing difficulty
• Feeding difficulty
• Floppy infant (poor muscle tone)
• Lack of head control
• Little spontaneous movement
• Progressive weakness (older infant to toddler)
• Very weak infant

Symptoms in a child:

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• Frequent, increasingly severe respiratory infections
• Nasal speech
• Worsening posture

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 (muscle fasciculation) of tongue muscle

Tests:

• CPK levels
• DNA testing to confirm diagnosis
• Electromyography
• MRI of the spine
• Muscle biopsy

Review Date: 03/09/2010
Reviewed By: Neil K. Kaneshiro, MD, MHA, Clinical Assistant Professor of Pediatrics, University of Washington School of Medicine; Daniel B. Hoch, PhD, MD, Assistant Professor of Neurology, Harvard Medical School, Department of Neurology, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org).