A Personalized Surgical Approach for the Treatment of Children with Obstructive Sleep Apnea and Small Tonsils - Project Summary Obstructive sleep apnea (OSA) is common in children with an estimated prevalence of 1-6%. Untreated pediatric OSA is associated with hypertension, autonomic dysfunction, attention deficit/hyperactivity disorder, neurocognitive deficits, and poor quality of life. Adenotonsillar hypertrophy is the primary risk factor for pediatric OSA, and adenotonsillectomy (AT) is the recommended first-line treatment. However, it is unclear whether children with small tonsils will benefit from AT. Clinic assessments of tonsil size do not consistently correlate with OSA severity or response to AT, resulting in confusion about how best to treat OSA in children with small tonsils. Drug-induced sleep endoscopy (DISE) enables direct observation of the sites and patterns of obstruction during sedated sleep. DISE increasingly helps guide surgical decision-making in adult OSA, and can also be used to guide surgical decisions in pediatric OSA and improve outcomes. The overall objective of this study is to test the effectiveness of a novel personalized approach to the surgical treatment of OSA in children. It is our central hypothesis that a personalized DISE-directed surgical approach in children with small tonsils will be superior to the standard first line treatment of AT. To test this hypothesis, we propose an unprecedented randomized controlled trial of DISE-directed surgery vs AT in children ages 2-18 years with clinically small tonsils with the following specific aims: Aim 1: Compare the physiological outcomes of DISE-directed surgery vs AT in children with small tonsils. Hypothesis 1: DISE-directed surgery will result in a clinically significantly greater improvement in the obstructive apnea-hypopnea index (OAHI) compared to the standard AT intervention. Aim 2: Compare the clinical outcomes of DISE-directed surgery vs AT in children with small tonsils. Hypothesis 2: DISE-directed surgery will result in a clinically significantly greater improvement in disease- specific QOL (OSA18) compared to the standard AT intervention. Aim 3: Determine if OSA severity is associated with specific anatomic endotypes in children with small tonsils. Hypothesis 3: Baseline OSA severity (defined by OAHI) is correlated with increasing severity of obstruction (i.e., number of anatomic sites with complete obstruction on DISE rating scale). Aim 4: Identify potential associations between baseline patient characteristics (e.g. age, obesity) and specific anatomic endotypes (e.g., severe nasal obstruction, severe base of tongue obstruction) in children with clinically small tonsils (exploratory aim). This comparative effectiveness trial will be the first to directly compare a personalized surgical approach to the standard treatment in children where the outcome of AT is uncertain. This novel approach may improve OSA outcomes and reduce the burden of unnecessary AT or secondary surgery for persistent OSA after an ineffective AT.