Patient reported outcomes (PROs) instruments are often used to measure meaningful treatment benefit or risk in clinical trials. PROs allow patients voices to be heard in ways that assist healthcare clinicians to address treatment effects and individual patient preferences. Unfortunately, infants and young children, especially those with a debilitating disease, such as neuromuscular disorders (NMD), may be less able to provide clear and concise information about treatment effects. In this case, we often defer to parents and guardians (to be referred to collectively as parents throughout protocol) to provide their perception of their child s overall health and wellbeing. Including parents in the assessment process recognizes the unique knowledge parents have of their child s development, reinforces their central role in implementing interventions, and aids in their ability to make better-informed healthcare decisions [1]. Yet, most parent-reports for young children are confined to overall quality of life (QoL). While QoL is an important area of assessment, its meaning varies among different ages and populations, and its results are often not precise enough to reveal small differences within samples [2]. A more specific area of concern in children with NMD is early-onset muscle weakness leading to difficulties in motor function.