85 - Shape and Volume Features of the Upper Airways and the Tongue: Useful Biomarkers to Improve Sleeping Apnea Diagnosis in down Syndrome?

Poster Board Number: 85
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Abstract Body : Introduction and Objective: Development and growth of craniofacial and respiratory structures involve closely integrated processes. Genetic or environmental disturbances in these well-coordinated processes can alter their normal course, causing orofacial dysmorphologies. Down syndrome (DS), a genetic disorder caused by an extra copy of chromosome 21, leads to altered biological systems development, resulting in orofacial anomalies such as midface retrusion, mandibular hypoplasia and macroglossia, which are associated with breathing disorders like Obstructive Sleep Apnea (OSA). The main objective of this study was to analyze the shape and volume of the upper airway passages, exploring the nasal cavity and the pharynx separately, and their relationship with the tongue. We hypothesized that morphological or volumetric alterations of these anatomical structures are associated with comorbid OSA that worsens the well-being of individuals with DS.

Materials and Methods: First, three-dimensional models of the upper airway passages were reconstructed using head magnetic resonances (MR) of 43 adults diagnosed with DS and 19 euploid controls. Then, we recorded 3D coordinates of 25 landmarks located on the upper airway reconstruction, as well as 5 landmarks placed on the midsagittal MR’s slice with the tongue visible to quantify shape changes and extracted volumetric data from the 3D models to analyze volume variations. Finally, we correlated these shape and volume measures with the severity of OSA, measured as the Apnea Hypopnea Index (AHI), available in polysomnography tests, which represents the amount of apnea and hypopnea incidents per hour during sleep. Following this OSA severity criteria, individuals with DS were classified in three categories: a) no OSA (AHI: < 5), mild (AHI: 5-30) and severe (AHI: >30).

Results: Geometric morphometric shape analyses revealed that the whole upper airway passages, the nasal cavity, the pharynx and the tongue are morphologically different in individuals with DS as compared to euploid controls (P-value< 0.0001). Specifically, they showed a constriction of the entire upper airway cavity, accompanied by a change in the pharyngeal angulation and a posteroinferior tongue displacement. However, no significant differences were detected in any comparison between individuals with DS at different OSA level. Moreover, individuals with DS presented a significant volumetric decrease of 30% in the whole upper airway structure and 34% in the nasal cavities, but not in the pharynx. Finally, we observed a progressive reduction of volume in the same structures comparing individuals with DS and no, mild and severe OSA.

Conclusion and Significance: The results showed that the upper airway passages, including the nasal cavity and the pharynx separately, and the tongue of the individuals with DS are morphologically altered and volumetrically reduced compared to euploid individuals. Furthermore, our findings suggest that the volumetric data of the entire upper airways and the nasal cavity can be used as accurate biomarkers which complement classic biomarkers such as the AHI to diagnose OSA. An accurate and earlier OSA diagnosis can delay the cognitive decline associated with this breathing disorder, which in most cases accelerate the onset of dementia.