How is spinal muscle atrophy (SMA) diagnosed?

Answer

SMA is often diagnosed clinically on the basis of the child's physical appearance. The diagnosis may be suspected when children are noted to be weak or to have a delay in their developmental milestones, such as holding their head up, rolling over, sitting independently, standing, or walking later than would be expected.

After a thorough medical history is reviewed and a physical examination is performed, the primary care provider may order genetic testing through a blood sample, or the child may be referred to a neurologist who will also perform an examination and then order genetic testing (again through a blood sample) to confirm the diagnosis.

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Media Gallery

Spinal muscle atrophy, Werdnig-Hoffman disease. Small muscle fibers within separate muscle fascicles.
Spinal muscle atrophy, Werdnig-Hoffman disease. Marked variation in muscle fiber size, as well as relative increase in associated connective tissue.
Spinal muscle atrophy, Kugelberg-Welander disease. Marked variation in muscle fiber size, along with increased perimysial connective tissue.
Spinal muscle atrophy, Kugelberg-Welander disease. Muscle-fiber variation with some demonstrating internal nuclei.
Spinal muscle atrophy. At age 4 years, this boy's chest radiograph already reveals presence of significant 32° left thoracic scoliosis. Diagnosis is type I spinal muscle atrophy (Werdnig-Hoffmann disease). This radiograph captures the lumbar curvature incompletely.
Spinal muscle atrophy. By age 6 years, child's curve is starting to decompensate. Note development of right-side truncal shift. He now has 40° thoracic curve and 60° lumbar curve.
Spinal muscle atrophy. Spine anteroposterior view. Spinal curvature is progressing. Lumbar curve now is 70°, and thoracic curve is 35°. It is now clearly apparent that right hip is dislocated. Also note marked pelvic obliquity in this patient.
Spinal muscle atrophy. By age 9 years, this patient with type I spinal muscle atrophy now has thoracic curve of 60° and lumbar curve of 110°. Note that patient has tracheostomy tube and nasogastric tube as well.
Spinal muscle atrophy. Immediate postoperative anteroposterior radiograph of patient at age 9 years. Thoracic curve is now at 18°, and lumbar curve is 35°, which represents more than 67% curvature correction.
Spinal muscle atrophy. Immediate postoperative lateral view with good sagittal balance.
Spinal muscle atrophy. Follow-up radiographs in patient at age 13 years reveal some spinal decompensation. Note so-called coathanger appearance of ribs in dysplastic right hemithorax.
Spinal muscle atrophy. Anteroposterior radiograph of pelvis demonstrating right hip dislocation.
Spinal muscle atrophy. Lauenstein lateral view of hips on patient with spinal muscle atrophy type I. Note near-universal pelvic dysmorphology (eg, widened obturator foramina) in addition to dislocated right hip.

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Author

Ashish S Ranade, MBBS, MS, MRCS Consultant Orthopaedic Surgeon, Columbia Asia Hospital and Deenanath Mangeshkar Hospital, India

Ashish S Ranade, MBBS, MS, MRCS is a member of the following medical societies: Paediatric Orthopaedic Society of India

Disclosure: Nothing to disclose.

Coauthor(s)

Mohan V Belthur, MD, FRCSC, FRCS(Tr&Orth) Clinical Assistant Professor, Departments of Child Health, Orthopedics, and Pediatrics, University of Arizona College of Medicine; Staff Pediatric Orthopedic Surgeon, Center for Pediatric Orthopedics, Phoenix Children’s Hospital

Mohan V Belthur, MD, FRCSC, FRCS(Tr&Orth) is a member of the following medical societies: American Academy for Cerebral Palsy and Developmental Medicine, American Academy of Orthopaedic Surgeons, American College of Surgeons, AO Trauma, Limb Lengthening and Reconstruction Society, Paediatric Orthopaedic Society of India, Pediatric Orthopaedic Society of North America

Disclosure: Serve(d) as a director, officer, partner, employee, advisor, consultant or trustee for: Phoenix Children's Hospital.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Chief Editor

Jeffrey A Goldstein, MD Clinical Professor of Orthopedic Surgery, New York University School of Medicine; Director of Spine Service, Director of Spine Fellowship, Department of Orthopedic Surgery, NYU Hospital for Joint Diseases, NYU Langone Medical Center

Jeffrey A Goldstein, MD is a member of the following medical societies: American Academy of Orthopaedic Surgeons, American College of Surgeons, American Orthopaedic Association, AOSpine, Cervical Spine Research Society, International Society for the Advancement of Spine Surgery, International Society for the Study of the Lumbar Spine, Lumbar Spine Research Society, North American Spine Society, Scoliosis Research Society, Society of Lateral Access Surgery

Disclosure: Serve(d) as a director, officer, partner, employee, advisor, consultant or trustee for: Medtronic, Nuvasive, NLT Spine, RTI, Magellan Health<br/>Received consulting fee from Medtronic for consulting; Received consulting fee from NuVasive for consulting; Received royalty from Nuvasive for consulting; Received consulting fee from K2M for consulting; Received ownership interest from NuVasive for none.

Additional Contributors

James F Kellam, MD, FRCSC, FACS, FRCS(Ire) Professor, Department of Orthopedic Surgery, University of Texas Medical School at Houston

James F Kellam, MD, FRCSC, FACS, FRCS(Ire) is a member of the following medical societies: American Academy of Orthopaedic Surgeons, Orthopaedic Trauma Association, Royal College of Physicians and Surgeons of Canada

Disclosure: Nothing to disclose.

Charles T Mehlman, DO, MPH Professor of Pediatrics and Pediatric Orthopedic Surgery, Division of Pediatric Orthopedic Surgery, Director, Musculoskeletal Outcomes Research, Cincinnati Children's Hospital Medical Center

Charles T Mehlman, DO, MPH is a member of the following medical societies: American Academy of Pediatrics, American Fracture Association, Scoliosis Research Society, Pediatric Orthopaedic Society of North America, American Medical Association, American Orthopaedic Foot and Ankle Society, American Osteopathic Association, Arthroscopy Association of North America, North American Spine Society, Ohio State Medical Association

Disclosure: Nothing to disclose.

Alvin H Crawford, MD, FACS Professor Emeritus of Pediatrics and Orthopedic Surgery, University of Cincinnati College of Medicine; Director, Founding Division of Pediatric Orthopedic Surgery, Department of Orthopedic Surgery, Cincinnati Children's Hospital Medical Center

Alvin H Crawford, MD, FACS is a member of the following medical societies: Ohio State Medical Association, Scoliosis Research Society, Pediatric Orthopaedic Society of North America

Disclosure: Nothing to disclose.

Jose A Herrera-Soto, MD Director of Orthopedic Research, Associate Director of Pediatric Orthopedic Surgery Fellowship Program, Arnold Palmer Hospital for Children, International Hip Dysplasia Institute, Orlando Health

Jose A Herrera-Soto, MD is a member of the following medical societies: American Academy of Orthopaedic Surgeons, North American Spine Society, Pediatric Orthopaedic Society of North America, Scoliosis Research Society

Disclosure: Nothing to disclose.

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