What is the role of imaging studies in the workup of spinal muscle atrophy (SMA)?

Updated: Nov 05, 2018
  • Author: Ashish S Ranade, MBBS, MS, MRCS; Chief Editor: Jeffrey A Goldstein, MD  more...
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Answer

On anteroposterior (AP) and lateral views of the pelvis, most patients with type II SMA are found to have developed hip dislocations. (See the images below.) The dislocations are only temporarily symptomatic and do not influence function in these patients, because they are nonambulatory.

Spinal muscle atrophy. Anteroposterior radiograph Spinal muscle atrophy. Anteroposterior radiograph of pelvis demonstrating right hip dislocation.
Spinal muscle atrophy. Lauenstein lateral view of 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.

A complete spine and scoliosis series is indicated. All patients with type II SMA and most patients with type III SMA develop a long C-shaped scoliotic curve. (See the images below.)

Spinal muscle atrophy. At age 4 years, this boy's 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 cur 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 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 patien 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.

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