Evaluation of the relationship between ultrasonographic muscle thickness measurement and echogenicity assessment with functional scales in patients diagnosed with spinal muscular atrophy

Aim: The aim of the study is to measure the thickness of target muscles in patients diagnosed with SMA using ultrasonography and to assess their echogenicity with the help of computer software, then to compare these values with those of a healthy control group. It is also aimed to reveal the relationship between the obtained ultrasonographic muscle thickness and echogenicity values and the motor functional scale scores. Material and Methods: This cross-sectional case-control study included patients aged 0–18 years diagnosed with SMA and age- and sex-matched healthy children as a control group. The thickness of the biceps brachii/brachialis, forearm flexors, quadriceps femoris, and tibialis anterior muscles was measured using ultrasonography. Furthermore, the echogenicity values of these muscles, along with the triceps brachii, proximal hamstring, gastrocnemius, and soleus muscles, were quantified using the ImageJ software via grayscale analysis. Motor functional status was assessed with the CHOP-INTEND, HFMSE, and RULM scales. Results: In the SMA group, the thickness of the biceps brachii/brachialis, forearm flexors, quadriceps femoris, and tibialis anterior muscles was significantly reduced compared to the control group, while echogenicity values were significantly increased for all muscles examined (p < 0.05). The echogenicity of the tibialis anterior muscle showed a strong negative correlation with CHOP-INTEND and HFMSE scores (r ≈ 0.7, p < 0.001). Additionally, a significant positive correlation was found between the thickness of the biceps brachii/brachialis and forearm flexor muscles and the RULM score (r = 0.412; p < 0.05 and r = 0.425; p < 0.05). Conclusion: This study demonstrates that muscle health in SMA patients can be objectively assessed using ultrasonography and that measurements of muscle thickness and echogenicity are significantly correlated with motor functional status. The findings support the use of ultrasonography as a complementary tool for monitoring disease severity and developing individualized treatment plans for SMA patients.