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Volumetric MRI analysis of Multilevel Upper Airway Surgery effects on pharyngeal structure.

STUDY OBJECTIVES
The Sleep Apnea Multilevel Surgery (SAMS) trial found that modified uvulopalatopharyngoplasty with tonsillectomy (if tonsils present) combined with radiofrequency tongue ablation reduced obstructive sleep apnea (OSA) severity and daytime sleepiness in moderate-severe OSA. This study aimed to investigate mechanisms of effect on Apnoea-Hypopnoea Index (AHI) reduction by assessing changes in upper airway volumes (airway space, soft palate, tongue, and intra-tongue fat).


METHODS
This is a case series analysis of forty-three participants of 51 randomized to the surgical arm of SAMS trial who underwent repeat magnetic resonance imaging (MRI). Upper airway volume, length, and cross-sectional area, soft palate and tongue volumes and tongue fat were measured. Relationships between changes in anatomical structures and apnea-hypopnea index (AHI) were assessed.


RESULTS
The participant sample was predominantly male (79%); mean ± SD age 42.7 ± 13.3 years, body mass index 30.8 ± 4.1 kg.m 2, and AHI 47.0 ± 22.3 events/hour. There were no, or minor, overall volumetric changes in the airway, soft palate, total tongue, or tongue fat volume. Post-surgery there was an increase in the minimum cross-sectional area by 0.1 cm 2 (95% confidence interval 0.04-0.2cm 2) in the pharyngeal airway, but not statistically significant on corrected analysis. There was no association with anatomical changes and AHI improvement.


CONCLUSIONS
This contemporary multi-level upper airway surgery has been shown to be an effective OSA treatment. The current anatomical investigation suggests there are not significant post-operative volumetric changes associated with OSA improvement six-months post-surgery. This suggests that effect on OSA improvement is achieved without notable deformation of airway volume. Reduced need for neuromuscular compensation during wake following anatomical improvement via surgery could explain lack of measurable volume change. Further research to understand the mechanisms of action of multilevel surgery is required.