143P Swallowing physiology and function in untreated patients with Spinal Muscular Atrophy type 1: establishing natural history reference values

Dysphagia has been a leading source of morbidity in patients with spinal muscular atrophy type 1 (SMA 1). The paucity of investigations has impeded the ability to judge the effect of disease modifying therapies (DMT). We report a natural history dataset characterizing swallowing biomechanics and function in untreated children with SMA 1. Infants with SMA 1 who had not received DMT and underwent a videofluoroscopic swallow study (VFSS) were retrospectively identified from 13 international children's hospitals. Charts were reviewed for oral intake and secretion management. VFSS’ were prospectively evaluated for biomechanics. Differences in swallowing between patients referred for VFSS due to swallowing concerns vs. those referred as part of a routine high-risk referral were tested using paired t-tests. Of the 77 children included, 30% of required suctioning, and 39% received alternative nutrition. Profound deficits were observed in sucking, with the inability to extract a bolus in 25% of children. Impairments in bolus clearance were common, with severe reductions in tongue base retraction (49%), absent pharyngeal stripping wave (23%), and minimal to no upper esophageal segment opening (50%) resulting in a majority-no clearance of the bolus from the pharynx in 40% of children. Pharyngeal constriction ratio (0.41 ± 0.28) and upper esophageal segment opening (0.12 ± 0.09) were consistent with these results. More than trace aspiration (56%) on >1 occurrence was seen in 52% of children. Deficits were significant worse in patients referred due to symptoms than asymptomatic (p < 0.05). Without pharmaceuticals patients with type 1 SMA exhibit profound deficits in swallowing. Although the presence of clinical signs of swallowing impairment may identify those children with the most profound deficits, they are not reliable for identifying a magnitude of other clinically significant impairments.