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Updated: Jun 10, 2026
Measurements of Motor Function and Other Clinical Outcome Parameters in Ambulant Children with Duchenne Muscular Dystrophy
Published on: January 12, 2019
Assessing spinal muscular atrophy with quantitative ultrasound
Jim S Wu1, Basil T Darras, Seward B Rutkove
1Department of Radiology, Beth Israel Deaconess Medical Center, Boston, MA, USA.
Objective:
To assess the value of quantitative ultrasound in patients with type 2 and 3 spinal muscular atrophy (SMA).
Methods:
Twenty-five patients with SMA (15 type 2 and 10 type 3) and 21 normal subjects were enrolled for this observational study. Strength of biceps brachii, wrist extensors, quadriceps, and tibialis anterior were measured with hand-held dynamometry. In addition, these 4 muscles were studied with a standard ultrasound system using a 5-MHz probe, and luminosity values for each muscle and the overlying subcutaneous fat were obtained by subsequent image analysis. A luminosity ratio (LR) for each muscle was calculated by dividing the muscle by the subcutaneous fat luminosity. The LR and strength scores for all 4 muscles were averaged to provide a single summary value for each patient.
Results:
The LRs increased with disease severity: 1.27 +/- 0.26 for normal subjects, 2.43 +/- 0.78 for type 3 SMA, and 3.85 +/- 1.3 for type 2 SMA (p < 0.001). Taking all the normal subject and patient data together, there was a good correlation between strength and LR (r = -0.711, p < 0.001). There was also a moderate relationship between LR and strength in the patients with SMA alone (r = -0.588, p = 0.008), and, as expected, a nonsignificant relationship between LR and strength in normal subjects (r = -0.011).
Conclusions:
Quantitative ultrasound has the potential of serving as a marker of SMA severity and may be useful in future clinical trials.
