Magnetic resonance imaging study of peripharyngeal mucosal intensity in obstructive sleep apnea patients

Abstract

Introduction Obstructive sleep apnea (OSA) is a common sleep disorder characterized by repetitive episodes of airway closure which usually occur in the retro-palatal region of the oropharynx. It has been known that upper airway mucosa in OSA patients is described as edematous. Recurrent injuries owing to vibration of the upper airway tissues or repetitive negative pressure may contribute to this phenomenon. On the other hand, fluid redistribution from the lower to the upper body during nocturnal recumbency could shift the fluid into neck and tissue around airway. The combination of these might contribute the occurrence or worsening of OSA by compressing the airway. Therefore, this study aims to investigate and establish simple magnetic resonance imaging (MRI) parameters, namely T2 mucous-to- masseter intensity ratio (T2MMIR), to assess the degree of tissue water content at the retro-palatal level and its relationship with sleep parameters in OSA patients. Materials and methods Twenty-seven subjects with OSA underwent polysomnography and cervical MRI with 1.5-tesla during wakefulness (age 55.0 ± 16.5 y, 77.8% male, with apnea-hypopnea index (AHI) 54.1 ± 27.6 and a body mass index (BMI) 29.4 ± 5.5) were included. On the axial T2-weighted images from the epipharynx to the oropharynx, the signal intensities for masseter muscle and peripharyngeal mucosa were measured. T2 mucous-to-masseter intensity ratio was calculated, and was used as an estimate of water content in the retro-palatal region. Pearson correlation analysis was performed to examine the correlation between peripharyngeal T2MMIR and polysomnography parameters. Results T2 mucous-to-masseter intensity ratio had moderate, positive correlation with supine AHI ( r = 0.388, P r = 0.408, P r = 0.411, P r = 0.419, P r = 0.645, P r = −0.401, P Conclusion This is the first report to establish peripharyngeal T2MMIR as one simple parameter representing peripharyngeal mucosal water contents due to inflammatory edema and/or fluid redistribution during recumbency, related to severity of OSA. This finding suggested its potential usefulness in reevaluation of change of peripharyngeal mucosa after OSA treatment to confirm its success.