Obstructive sleep apnea (OSA) is defined as repetitive obstruction of the upper airway during sleep and has been estimated to affect 1-6% of the general pediatric population. Untreated OSA in children has been associated with childhood hypertension, autonomic dysfunction, attention-deficit/hyperactivity disorder, neurobehavioral impairment, and poor quality of life. These sequelae contribute to a 226% increase in health care utilization among children with OSA compared to controls, primarily in the form of increased hospitalizations, emergency department visits, and medication use. Adenotonsillar hypertrophy is considered the most common risk factor for OSA in children, and adenotonsillectomy (AT) is the first line treatment.

Although AT is the recommended first line treatment for pediatric OSA in treatment guidelines, multiple studies have demonstrated that AT is not always curative, with estimates of persistent OSA after AT ranging from 25 to 75%. Many risk factors for AT failure have been reported, but the impact of tonsil size on AT outcome remains a controversial topic. Not every child with enlarged tonsils will have OSA, and conversely, there are many children with proven OSA who do not have clinically large tonsils or adenoids. The prevalence of small tonsils (1+ or 2+ on Brodsky tonsil scoring scale of 1+ to 4+) has been reported to be 67-70% among children with symptoms of OSA presenting to either the emergency department or a pediatric pulmonology clinic. Clinic assessment of tonsil size during an awake examination has not consistently correlated with either baseline disease severity or response to AT. The outcome of AT in children with small tonsils (Brodsky 1+ or 2+) remains unknown and clinical decisions in children with small tonsils are not evidence-based.

Patients with Down Syndrome have a higher incidence of OSA than the general pediatric population, with rates of 30-60%, resulting in increased morbidity and decreased quality of life for affected individuals. Children with Down Syndrome often undergo T\&A for obstructive sleep apnea; however 30-50% will have persistent obstructive sleep patterns requiring continuous positive pressure airway support (CPAP) or tracheotomy. Persistent obstruction is attributed to anatomic and physiologic differences in this population, including reduced muscular tone, macroglossia, maxillary hypoplasia, and lingual tonsil hypertrophy.

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 the investigators hypothesize DISE can guide surgical decisions in pediatric OSA and improve outcomes. Towards that end, the study team has developed and validated the DISE Rating Scale in children. Furthermore, the investigators have demonstrated DISE ratings of adenotonsillar obstruction during sedated sleep are strongly associated with both OSA severity and response to AT, unlike clinic assessments of tonsil size. This preliminary data and others' studies have identified non-adenotonsillar obstruction can also occur at the nose, palate, base of tongue, and larynx. DISE findings in surgically naïve children and the outcomes of procedures based on those findings have been reported in mostly small observational case series. The surgical plan may be modified from the standard AT in up to 77% of children based on DISE findings. These alternative procedures can be less invasive (e.g., only isolated adenoidectomy or isolated tonsillectomy) or include procedures to address other anatomic sites in addition to or instead of the tonsils and adenoids. The most commonly reported non-adenotonsillar sites of obstruction are the nose, velopharynx (soft palate), tongue base, and the larynx. DISE-directed surgery at these sites may improve pediatric OSA outcomes, but existing studies are small, uncontrolled case series in heterogeneous study populations. There are no trials directly comparing AT and DISE-directed surgery in the common scenario of surgically naïve children with small tonsils. This study will inform a future randomized trial that has the potential to change the paradigm of treating OSA in children with small tonsils or Down syndrome, thereby improving outcomes, and reducing inappropriate AT and need for secondary sleep surgery.