Quantitative MRI as a biomarker in Spinal Muscular Atrophy: Mapping of muscle and nerve properties with MRI for disease progression and treatment effects in SMA

Abstract

Spinal muscular atrophy (SMA) is a neuromuscular disease characterized by progressive muscle weakness and is the leading genetic cause of infant death and disability in childhood. Its prognosis is now being altered by multiple treatments. In order to justify the burden and risks of treatment, there is a need for biomarkers that can identify early treatment response, or the lack thereof. Such a potential biomarker is quantitative MR imaging. This thesis describes multiple MR studies performed in children and adults with SMA. First, quantitative MR markers have been used to describe muscle and nerve characteristics in people with SMA of varying disease type, disease severity and age. Subsequently, a longitudinal study showed that MRI is able to track subclinical disease progression. This study is particularly valuable as future imaging studies on natural disease progression in treatment-naïve patients will become increasingly unlikely. Moreover, when used in the monitoring of young children that received treatment with nusinersen, a characteristic pattern in of fat infiltration emerged that seems to match those who improved under treatment. These preliminary findings could be an indicator of treatment response. This thesis concludes that quantitative muscle MRI can serve as a biomarker for natural disease progression and for treatment effects. Together, these studies provide benchmarks for future projects that would further contribute to our understanding of SMA.