1 X Will functional imaging influence treatmentselection in children with Down syndrome and OSA? Obstructive sleep apnea (OSA) is the most severe manifestation Prevalence: 24-79% DS is associated with a high prevalence of sleep disturbances Each year  3,000 to 5,000 are born with Down syndrome (DS) worldwide X OSA: Multifactorial disease, main cause: adenoid/tonsil hypertrophy First line treatment: Adenotonsillectomy (AT) Persistent OSA after treatment in up to 87% Untreated OSA is associated with a range of complications including hyperactivity, attention deficits, persistent bedwetting, night sweating, and cardiovascular problems Introduction Goal: pre-operative evaluation of the upper airway is therefore needed to identify the level and degree of UA obstruction Methods Functional respiratory imaging (FRI) is a technique to calculate flow patterns, upper airway volumes and resistance/conductance. 3D model of the upper airway was extracted from images of a CT-scan and combined with computational fluid dynamics for FRI. Children with DS and OSA diagnosed by polysomnography (PSG) Age: 6 months-10 years old OSA: oAHI ≥ 2 events/hour Gradation: mild 2-5, moderate 5-10, severe > 10 Evaluation in terms of history and clinical examination (tonsil score by Brodsky score) CT-scan upper airway Radiation: mSv 3D model  FRI Choice of treatment Based on history, tonsil score, PSG and drug induced sedation endoscopy 2nd PSG after AT Results Before treatment 33 children with DS and OSA, mean age of 4.3 years old Children with more severe OSA had a smaller minimal passage through UA (19 vs 8 mm², p = 0.03) Less volume in region adenoids/tonsils, lower conductance in upper airway at FRI and higher tonsil score correlated with a lower minimal oxygen saturation during PSG 2284 vs 212 mm³, p = 0.003 3787 vs 1466 mm³, p = 0.003 After treatment children underwent a second sleep study after AT 79% persistent OSA, however 15 children had a decrease > 50% in oAHI after AT Children with more severe OSA had a larger decline of oAHI after treatment (r=0.84, p<0.001) Children with a less favorable response to AT had a smaller volume of zone 4 and 5 which could be caused by enlargement of the lingual tonsils, lymphoid tissue or macroglossia Zone vs mm³, p = 0.003 Zone vs mm³, p = 0.003 Conclusion This study suggest that functional respiratory imaging have an extra value in treatment selection in children with Down syndrome and OSA Slaats Monique (1,2); Loterman Dieter (3); Van Holsbeke Cedric (3); Vos Wim (3); De Backer Jan (3); Van Hoorenbeeck Kim (1,2); De Backer Wilfried (1,2); Wojciechowski Marek (1,2); Boudewyns An (1); Verhulst Stijn (1,2) 1. UZA (Edegem) - 2. LEMP (UA; Edegem) - 3. FLUIDDA (Kontich)