## 4 Discussion
In our study group, a higher amount of parapharyngeal fat tissue was associated with higher waist circumference and submental neck fat tissue thickening was correlated with lower body muscle percentage which further proves the importance of detailed body type and body composition analysis in obese patients. This method could be a helpful addition to the screening method for central obesity and risk for OSA development. PVAT plays an important contributing role in the development of atherosclerosis [23; 24]. Several papers showed the role of increased perivascular adipose tissue accumulation in coronary artery disease as a noninvasive imaging biomarker of coronary inflammation which associates with high-risk plaque features and independently predicts cardiac mortality [15; 25]. However, there have been a few studies investigating the possible effects of PVAT surrounding the carotid arteries. [PERSON] et al. found an elevated density of carotid artery PVAT on CT scans in patients with embolic stroke of unknown source [26]. [PERSON] et al. found an independent association between carotid artery PVAT density and intraplaque hemorrhage analyzing CT and MRI scans [27]. In another study, [PERSON] et al. also found a significant correlation between cerebrovascular symptoms and carotid PVAT density during a retrospective analysis of CT images [28]. [PERSON] et al. also found an increased density of carotid PVAT on CT scans in patients with stroke or TIA compared to asymptomatic patients [29]. However, there are no data on the role of PVAT and carotid IMT itself. There have been studies on the role of EMT as a measure of adventitial structure and perivascular adiposity that found a significant correlation between EMT and metabolic syndrome. However, in this study, we only found a significant association between the narrowest point of the posterior airways and EMT on the left carotid artery. Interestingly, in our study, IMT of several arterial segments showed a negative association with higher parapharyngeal fat tissue accumulation. Meanwhile, several studies have investigated the association between OSA and CIMT. A meta-analysis of 16 studies found that individuals with severe OSA had a significantly higher CIMT compared to those without OSA, meanwhile, patients with mild-moderate OSA showed similar IMT values as the control group [30]. Another meta-analysis of 18 studies also found that severe OSA was positively correlated with CIMT thickening, meanwhile, patients with mild to moderate OSA showed similar CIMT values as the control group [31]. The controversy between our results and the current literature could be due to several reasons. First of all, the studies investigating PVAT and carotid artery atherosclerosis mentioned above assessed the density and inflammation of the fat tissue in the small range of the artery on CTA scans, meanwhile, we only measured the axial area of the whole parapharyngeal fat tissue on MRA images. Also, our study subjects were relatively young, in the meantime, CIMT thickening is mainly associated with aging [32]. Furthermore, our study group was relatively healthy based on average BMI, low rate of plaque burden, low number of patients who had hypertension, DM, or dyslipidemia and few subjects had a history of smoking. Therefore, even early atherosclerotic markers are less expected to be present in this study group. We could interpret that CIMT would not be an optimal marker in the early screening of OSA, rather it could be an effective screening method later on after the development and progression of the disease for the detection of resulting atherosclerosis. In conclusion, in the currently available literature, there are limited data regarding carotid and femoral IMT and EMT and their association with risk for cardiovascular events. Our study had a few limitations such as it included a relatively small number of subjects which led to a low number of discordant pairs. Our study group had a 1:2 male-to-female ratio; meanwhile, OSA would be more common in the male population.