Sleep cine magnetic resonance imaging—A dynamic evaluation of the airway

Evaluation of Complex Upper Airway Obstruction in Children Using Cine-MRI: A Single-Center Experience and Literature Review

Introduction Polysomnography (PSG) is considered the gold standard diagnostic test for obstructive sleep apnea (OSA) in children. However, the anatomic location of upper airway obstruction in these patients cannot be determined by PSG, especially in children with complex upper airway obstruction. CT imaging and endoscopic evaluation have been proposed for the evaluation of upper airways in these children. However, cinematic magnetic resonance imaging (Cine-MRI) is a safer, less invasive, and potentially more useful tool for dynamic and anatomical evaluation of upper airways. We here describe the diagnostic outcomes of Cine-MRI in our cohort of children with OSA and suspected complex upper airway obstruction. Methods A retrospective chart review of clinical and radiological data of all children with PSG confirmed diagnosis of OSA and who underwent upper airway evaluation using Cine-MRI. Upper airways were evaluated at three different levels: nasopharynx, oropharynx, and supraglottic, during both inspiration and expiration. Fractional collapse (FC) at different levels was used to evaluate dynamic airway collapse and was defined as the difference between maximum and minimum airway dimensions divided by the maximum dimensions. Results Eight children (five females and three males) were included. Median age was 8.5 months (range: one month to 16 years). Cine-MRIs identified upper airway obstruction in all patients. Additionally, 50% of the patients had more than one level of obstruction, mainly the nasopharynx and oropharynx. There was a positive correlation between the apnea-hypopnea index (AHI) and FC in the anteroposterior dimension at the nasopharyngeal and the oropharyngeal levels, but it did not reach statistical significance. However, there was a statistically significant negative correlation between AHI and FC in the transverse dimension at the oropharyngeal level. Cine-MRI was helpful in continuous positive airway pressure (CPAP) titration in two patients and was helpful in planning surgical intervention in two patients. Conclusion Cine-MRI is a helpful diagnostic tool in evaluating patients with complex upper airway obstruction and can direct potential surgical and non-surgical intervention in pediatric patients with complex upper airway obstruction.

Considerations in Surgical Management of Pediatric Obstructive Sleep Apnea: Tonsillectomy and Beyond

Obstructive sleep apnea (OSA) is an increasingly recognized disorder with a reported incidence of 5.7% in children. Tonsillectomy (with or without adenoidectomy) in pediatric OSA in otherwise healthy non-obese children has a success rate of approximately 75%. However, the cure rate reported for all children undergoing tonsillectomy varies from 51% to 83%. This article reviews the history of tonsillectomy, its indications, techniques, various methods, risks, and successes. The article also explores other surgical options in children with residual OSA post-tonsillectomy.

A novel method to generate dynamic boundary conditions for airway CFD by mapping upper airway movement with non-rigid registration of dynamic and static MRI

Computational fluid dynamics (CFD) simulations of airflow in the human airways have the potential to provide a great deal of information that can aid clinicians in case management and surgical decision making, such as airway resistance, energy expenditure, airflow distribution, heat and moisture transfer, and particle deposition, as well as the change in each of these due to surgical interventions. However, the clinical relevance of CFD simulations has been limited to date, as previous models either did not incorporate neuromuscular motion or any motion at all. Many common airway pathologies, such as obstructive sleep apnea (OSA) and tracheomalacia, involve large movements of the structures surrounding the airway, such as the tongue and soft palate. Airway wall motion may be due to many factors including neuromuscular motion, internal aerodynamic forces, and external forces such as gravity. Therefore, to realistically model these airway diseases, a method is required to derive the airway wall motion, whatever the cause, and apply it as a boundary condition to CFD simulations. This paper presents and validates a novel method of capturing in vivo motion of airway walls from magnetic resonance images with high spatiotemporal resolution, through a novel combination of non-rigid image, surface, and surface-normal-vector registration. Coupled with image-synchronous pneumotachography, this technique provides the necessary boundary conditions for dynamic CFD simulations of breathing, allowing the effect of the airway's complex motion to be calculated for the first time, in both normal subjects and those with conditions such as OSA.

Volume estimation of tonsil phantoms using an oral camera with 3D imaging

Three-dimensional (3D) visualization of oral cavity and oropharyngeal anatomy may play an important role in the evaluation for obstructive sleep apnea (OSA). Although computed tomography (CT) and magnetic resonance (MRI) imaging are capable of providing 3D anatomical descriptions, this type of technology is not readily available in a clinic setting. Current imaging of the oropharynx is performed using a light source and tongue depressors. For better assessment of the inferior pole of the tonsils and tongue base flexible laryngoscopes are required which only provide a two dimensional (2D) rendering. As a result, clinical diagnosis is generally subjective in tonsillar hypertrophy where current physical examination has limitations. In this report, we designed a hand held portable oral camera with 3D imaging capability to reconstruct the anatomy of the oropharynx in tonsillar hypertrophy where the tonsils get enlarged and can lead to increased airway resistance. We were able to precisely reconstruct the 3D shape of the tonsils and from that estimate airway obstruction percentage and volume of the tonsils in 3D printed realistic models. Our results correlate well with Brodsky's classification of tonsillar hypertrophy as well as intraoperative volume estimations.