In the last few years, a number of therapeutic approaches have targeted a possible increase of the production of SMN protein in target motor neurons by genetic replacement of the defective SMN1 gene or by modifying pre-mRNA splicing in SMN2 to promote exon 7 inclusion by using an antisense oligonucleotide or small molecule drugs. Several clinical studies have focused on the evaluation of patients with SMA, whether they are ambulatory or not, adults, children or infants, treated or untreated.~Depending on the SMA type, age or ambulatory status of the patients, different assessments (motor function scales or questionnaires) have provided consistent results to measure the evolution of the patients, such as HFMSE, MFM, RULM, 6MWT, MRC scale, Chop Intend or HINE.~As these evaluations are generally carried out in a controlled environment, they are likely to present an environmental bias. Even if studies are designed to anticipate and avoid most of these issues, different factors can influence patient test results (fatigue, motivation, stress, day to day variability…). From an economical point of view, the evaluation of patients in a controlled environment also has a significant cost, which heavily impact the global cost of clinical research or standard care (transport, patients' accommodation and care…). This factor is even more important as a significant proportion of the SMA population is non-ambulatory.~New treatments are indicated to treat SMA with a major impact on pre-existing disease standards of care and patients care pathway. In particular, there is no consensus on appropriate measures to monitor disease progression and treatment effect in a real-world setting. Such measures are critically needed to discuss treatment indication (treatment initiation criteria and stopping rules, therapeutic goals) and treatment monitoring. While patient reported outcome measures (PROMs) become more represented, objective functional measures are still required to assess SMA. In spite of the development of digital measures, no validated patient self-reported functional measures can be used as a surrogate. Thus, the objective disease assessment is currently based on validated outcome measures for SMA, similar to those used in clinical studies. As compared to clinical trials, the feasibility to administer these measures to SMA patients is challenging. Major limiting factors are: (1) the high disease-prevalence, (2) time-consuming measures, (3) the need for trained expert evaluators, and (4) limited access to hospital-based resources. In addition, the burden of affected individuals and caregivers has not been evaluated as well as patient treatment monitoring expectations. A refined approach using modern tools and fitting with patient real life environment is needed.
There is no complete cure for SMA yet. However, the discovery of the genetic cause of SMA has led to the development of several treatment options that affect the genes involved in SMA - a gene replacement therapy called Zolgensma, and two drugs, called Nusinersen (Spinraza) and Risdiplam (Evyrsdi). In this context, the evaluation of efficacy and the long term follow-up of patients treated with these innovative treatments in clinical routine is one of the critical points. These evaluations are carried out in a medical context (clinical sites or research unit) using validated measurement tools and outcome measures. Carrying out these evaluations in a controlled environment can be considered from certain aspects as an advantage (reproducibility of measures, neutral environment, etc.), but also raises a certain number of questions regarding the impact on patients, the financial cost, or the relevance of the data obtained in an unnatural environment (stress, fatigue, patient motivation…). Also the regulatory authorities ask for longitudinal data for deciding to reimburse these expensive treatments. As such, the hospital cannot digest all these evaluations due to a lack of resources.