# Ultrasound and Magnetic Resonance Imaging of the Tongue in Obstructive Sleep Apnoea
## 4 Discussion  
One of the main objectives of the present study was to analyse the effects of age, sex, and BMI on the tongue parameters in OSA. Furthermore, the prognostication of OSA and tongue-based obstruction using US and MRI measurements were also analysed. The clinical significance of the current study is to screen for previously not diagnosed OSA cases and subjects with tongue-based obstructions who undergo US or MRI examinations with another indication (for instance, salivary gland problems, lymph node pathologies in the neck region, or thyroid gland abnormalities). Improving OSA diagnostic methods is vital due to the high number of undiagnosed cases. MRI of the tongue can measure the parameters of the soft tissues in the coronal, axial, and sagittal planes. Moreover, three-dimensional reconstructions and determination of the volume of cross-sectional area are also possible [11]. In our studied population, MRI only showed a significantly different result for OSA patients in the case of coronal and anteroposterior diameters, midsagittal area, and fat of the midsagittal area parameters, compared to the control group. [PERSON] et al. found higher tongue volume values in the OSA group, although the difference was insignificant compared to the non-OSA group [12]. These findings are in contrast to the results of [PERSON] et al. and [PERSON] et al., who have observed significant differences [13; 14]. Based on our results, Fat% did not differ significantly; however, [PERSON] et al. concluded significant differences also with a correlation between AHI, Fat%, and tongue volume [15]. The correlation between US and MRI diameters and volumes is weak, since US is a subjective method, and there are also differences between the US and MRI parameters calculated by the different imaging softwares. Moreover, the amorphous form of the tongue also makes it difficult to calculate the parameters correctly. US measurements of the tongue were also observed during MM to detect possible changes in the volumes and diameters of the tongue. The effectiveness of MM is questionable in the diagnosis of OSA. Although some authors have not found a significant correlation between obstructions during MM and the results of sleep endoscopy [16], others have observed significant correspondences between multilevel hypopharyngeal obstructions and Epworth Sleepiness Scale values [17]. [PERSON] et al. have detected more retroglossal obstruction during sleep-endoscopy than in the case of MM [18]. [PERSON] et al. have not found a correlation between the severity of obstruction, AHI, BMI, oxygen saturation values, and MM [19]. Using US, significantly higher diameters and tongue volumes were detected in patients with OSA, both at rest and during MM, compared to the control group. [PERSON] et al. examined US and found higher tongue thicknesses in the coronal plane of those involved in OSA, similarly to our findings [20]. [PERSON] et al. concluded that the thickness of the tongue base measured by the US during MM is an essential indicator for OSA severity [21]. [PERSON] et al. detected significantly higher tongue values during MM [22]. Our results did not show a significant correspondence between tongue obstruction detected by sleep endoscopy and tongue volumes during MM, using US measurements. Therefore, MM is unable to detect tongue-based obstructions. It is a well-known fact that the patients' age, sex, and nutritional status significantly influence on the pathogenesis of OSA [1]. Therefore, the effects of these parameters were also investigated. The effect of gender was observed on all US parameters, although a significant difference was only detected in the case of tongue volume during normal breathing and MM and axial tongue diameter during MM. Using MRI, only the diameter of the coronal tongue diameter in male patients differed, in contrast to other investigations, which have observed significantly higher volumes of the tongue and of the cross-sectional area parameters in men [13; 23; 24; 25].