Neurodevelopmental Comorbidities in Early-Onset 5q-SMA Treated with Disease-Modifying Therapies: A Scoping Review

Recent studies have reported possible neurodevelopmental comorbidities in some early onset 5q-spinal muscular atrophy (5q-SMA) patients treated with disease-modifying therapies (DMT). This scoping review aims to determine the current state of the published and grey literature on neurodevelopmental comorbidities in early onset 5q-SMA patients treated with nusinersen, risdiplam, or onasemnogene abeparvovec. Eligible records included primary literature (journal papers excluding review articles), and conference proceedings (abstracts or posters) published in 2016 or later. A total of 6,310 database and grey literature records were screened, of which five primary literature and six conference proceedings were included. Ten records used quantitative approaches (the other mixed methods) while specific outcome measures varied. Mixed findings were reported on association of worse cognitive or developmental outcomes with gender, lower SMN2 copy number, and motor function. Authors most often explained findings by citing unknown brain injury or pathophysiology, use of non-disease specific tests, effect of motor or communicative function on exposure to environmental stimulation, and lack of SMN protein in non-spinal cord neurons. This review underscores the need for research into the longitudinal neurodevelopmental profile of these patients, creation of disease-specific outcome measures, and exploration of the neuropathophysiological characteristics of early onset 5q-SMA patients treated with DMTs.