Infantile Spinal Muscular Atrophy

Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disease caused by the degeneration of motor neurons in the anterior horn of the spinal cord, due to the absence of the SMN1 gene and the resulting lack of SMN protein. Some patients with particularly severe forms (types 0 or 1) die before the age of 2 in the absence of treatment, while others retain autonomous walking throughout their lives, with no reduction in life expectancy. Three treatments aimed at restoring SMN (TRS) protein expression have recently been approved by the US Food and Drug Administration and the European Medicines Agency (i.e. Nusinersen / Onasemnogene Abeparvovec / Risdiplam). Patients treated with TRS after the onset of symptoms (symptomatic patients) may show significant motor improvement, but retain difficulties such as muscle weakness and fatigue leading to limitations in activities of daily living. The aim of this study is to adapt a fatigability test, widely validated in its original version in different populations (QIF test), but adapted in this protocol to the motor level and low abilities of certain SMA patients. Our objectives are to determine whether these assessments are feasible in SMA patients, reproducible, and relevant for monitoring this population, either routinely or for future clinical trials.

Spinal muscular atrophy (SMA) is a genetic neurodegenerative disease impacting spinal cord motor neurons, leading to motor and respiratory issues and, ultimately, death. With emerging therapies, a need arises to enhance motor function assessment in severely hypotonic infants (SMA type 1) as traditional scales on examination tables lack completeness due to gravity's influence. The study team has developed a "bath test" to observe infants' motor skills in water, eliminating gravity's effects. This test aims to detect subtle movements using inertial sensors, potentially revealing more active motor neurons in aquatic conditions. It aids in identifying infants with motor improvement potential, even if they show limited mobility outside water, and tracks disease progression and therapy responses. Presently, pediatric neurologists in France use parent-provided bathing videos for evaluations, but these lack standardization and precision. The study aims to establish a standardized evaluation protocol with quantifiable data. The study's key objective is to evaluate severely hypotonic SMA infants using inertial sensors, including accelerometers, gyrometers, and magnetometers. The study will conduct "dry" and "water" assessments using a specially designed bathtub. This method's goal is to quantify water-based movements accurately. Simultaneously, the study seeks to establish semi-quantitative evaluation criteria to create a clinical assessment scale for infant motor function in bathtubs. This scale will aid doctors in therapeutic decisions. The study will not influence the treatment or therapeutic decisions made for the children being tested. Collected data from "dry" and "water" conditions will be statistically analyzed and compared to reference motor assessment scales (e.g., CHOP INTEND and HINE) and electromyography (CMAP-EMG) results, commonly used in diagnosis and monitoring. Blurred video recordings will assist in protocol monitoring and sensor data analysis.