Neck and Trunk Muscle Strength in Children With Spinal Muscular Atrophy Is Lower Than in Healthy Controls and Depends on Disease Type

Quantitative assessment of muscle atrophy and structural changes in children with spinal muscular atrophy using ultrasound imaging

BACKGROUND

Spinal muscular atrophy (SMA) in children is a hereditary neuromuscular disorder characterized by motor neuron degeneration, which leads to progressive muscle weakness and impaired movement. Ultrasound imaging, owing to its non-invasive, radiation-free, and cost-effective nature, provides an invaluable tool for visualizing muscle morphology. This technique offers a significant advantage in the clinical evaluation of SMA. The aim of this study was to quantitatively assess muscle abnormalities in children with SMA using both conventional ultrasound and shear wave elastography (SWE), and to explore the potential of these imaging modalities in the assessment of the disease.

METHODS

A total of 20 patients with type II or III SMA, who had not received any prior disease-modifying treatment (DMT), were included in the SMA group. These patients were enrolled between May 2022 and January 2024. The control group comprised 20 healthy children matched for age and gender. Muscle thickness (MT) and shear wave velocity (SWV) of the biceps brachii (BB) and quadriceps femoris (QF) were measured using B-mode ultrasound and SWE. Ultrasound parameters were compared between children with SMA and healthy controls. Additionally, motor function in the SMA group was assessed using the Hammersmith Functional Motor Scale Expanded (HFMSE), and the correlation between ultrasound parameters and HFMSE scores was analyzed.

RESULTS

The BB-MT, BB-SWV, QF-MT and QF-SWV in the SMA group, were significantly lower than those in the control group (p = 0.030, 0.000, 0.004, and 0.001, respectively). Correlation analysis revealed a significant positive correlation between QF-MT and QF-SWV in the SMA group and the HFMSE score (r = 0.802, p = 0.000; r = 0.56, p = 0.000, respectively).

CONCLUSIONS

Ultrasound imaging is an effective modality for detecting and quantifying muscle atrophy and structural changes in children with SMA. Moreover, it demonstrates a significant correlation with motor function, providing valuable insights into the clinical assessment of SMA.

Test-Retest Reliability of Cervical Strength Testing Protocols with Handheld Dynamometer in Prepubertal and Pubertal Untrained Boys

Background: The cervical spine plays an important role in several daily activities of children and adolescents, and thus, its evaluation using reliable protocols is of crucial importance. This study examined the test-retest reliability of cervical strength protocols using indices of absolute (standard error of measurement-SEM and 95% limits of agreement-LOA) and relative reliability (intraclass correlation coefficient-ICC). Methods: Twenty prepubertal (9.10 ± 0.61 years old) and twenty pubertal boys (13.6 ± 0.6 years old) participated in two assessment sessions separated by 48 h. During both sessions, maximal isometric strength (forward flexion, extension, and right-left lateral flexion) was assessed using a handheld dynamometer, and then, the cervical flexion-to-extension ratio (cervicalF/E ratio) was calculated. Results: According to our data analysis, good absolute and relative reliability was denoted for prepubertal boys in all cervical movements (ICC = 0.81-0.90; SEM% = 5.82-8.62); conversely, pubertal boys denoted high relative and absolute reliability in all directions of movements (ICC = 0.90-0.96; SEM% = 3.8-5.5). The cervicalF/E ratio showed moderate reliability in prepubertal (ICC = 0.71; SEM% = 9.11) and pubertal boys (ICC = 0.78; SEM% = 7). Conclusions: In conclusion, the isometric strength of cervical muscles, using a handheld dynamometer, showed acceptable reliability in prepubertal and pubertal boys; however, prepubertal boys demonstrated slightly lower reliability. Additionally, the assessment of the cervical F/E ratio should be interpreted with caution. However, it would be important to carry out future studies to strengthen the findings of the present study.

Motor Function of Children with SMA1 and SMA2 Depends on the Neck and Trunk Muscle Strength, Deformation of the Spine, and the Range of Motion in the Limb Joints

The purpose of this study was to investigate the functional relationships between selected ranges of motion of the neck, upper and lower limbs, the strength of the neck and trunk muscles, postural parameters, and the motor function of children with SMA1 and SMA2—27 children, aged 6 months-15 years, with genetically confirmed spinal muscular atrophy type 1 (19 children) and 2 (8 children) undergoing pharmacological treatment. All children were examined, according to the methodology, including the motor function evaluation, measurement of selected ranges of motion, assessment of postural parameters, and measurement of neck and trunk muscle strength. The functional status of 15 children was assessed with the CHOP INTEND (CHOP group) scale and of 12 children with the HFMSE (HFMSE group). The results obtained showed that, in children examined with the CHOP scale, greater limitation of flexion in the shoulder joints was observed. As the deformation of the chest increased, the functional abilities of children deteriorated. In participants examined with the CHOP group, the ranges of neck rotation decreased with the increase of the chest deformity. In the HFMSE group, the ranges of head rotation showed a strong relationship with some parameters of muscle strength and the sum of the R coefficients. Participants showed many significant relationships between the range of motion in the neck and joints of the limbs, with more significant relationships in the CHOP group. The following conclusions were made: motor skills of children with SMA depend on muscle strength, range of motion, and deformities of the spine and chest; the development of scoliosis adversely affects the motor function, ranges of motion, and muscle strength; and movement ranges are related to motor skills and strength values.