# Oral Appliances for Severe Positional Obstructive Sleep Apnea Syndrome: A Case Report
## 3 Discussion  
The mandibular advancement device (MAD) can be used as first-line therapy in patients with mild-to-moderate OSAS [26] without severe cardiovascular comorbidity and for severe OSA when CPAP treatment fails or is refused by the patient [27]. This case report describes the beneficial effects of MADs in an elderly, non-obese patient with severe positional OSAS who refused CPAP treatment. In the scientific literature, the MAD shows significantly better treatment outcomes in patients with positional OSAS compared to patients with non-positional OSAS, but it does not offer a reduction in the severity of OSAS. This may be due to the unchanged or absent pharyngeal collapsibility in POSAS patients, which allows improved AHI in the supine position but without reducing OSAS symptomatology [28]. In 2004, in a study conducted on a large sample of 263 patients undergoing PSG with and without MADs, [PERSON] et al. demonstrated that the odds ratio for MAD treatment success was six times higher in patients with positional OSAS than in patients not treated with MADs [29]. The beneficial effect of MADs was also demonstrated in a study by [PERSON] et al., who found that patients with POSAS had significantly better treatment outcomes (77.5% success rate) than patients with non-positional OSAS (60.0% success rate) when treatment success was defined as AHI less than 20. In the same study, the authors reported a complete reduction in obstructive events (AHI less than 10) of 57.5% in POSAS patients versus 30.0% in patients without POSAS [30]. [PERSON] et al. demonstrated that mandibular advancement in non-obese patients increases the retropalatal airway space, whereas mandibular advancement in obese patients does not ensure upper airway patency [31]. In our case report, the clinical and PSG results obtained after a two-year follow-up period in the treatment of severe positional OSAS with a MAD showed a significant decrease in the severity of OSAS. Indeed, a 4.7 mm advancement of the mandible, a 58.9% reduction in AHI in the lateral position, a 75.5% reduction in the supine position, and a reduction in the severity of OSAS from severe to mild were observed. The significant reduction in the severity of OSAS represents an important novelty for treatment with MADs. Since the patient in our case had a normal weight from the beginning to the end of the follow-up, the efficacy of the MAD was not affected by changes in body composition, so the achieved mandibular displacement should have allowed the patient to change his sleep position. This change in position could be related to the change in upper airway configuration caused by the advancement of the mandible, which is strongly influenced by the extent of its change in response to the change in body position, which could be exacerbated by gravity [32]. Considering that the mechanism of action of MADs is to maintain the upper airway not only by increasing the retropalatal and retrolingual spaces but also by decreasing pharyngeal collapsibility [33], we can hypothesize that the advantage in maintaining the upper airway may have determined an indirect stimulus for adopting a better and adapted position during sleep. In this case report, the patient complied during the two-year follow-up period, and no signs or symptoms related to the side effects of the MAD occurred. According to [PERSON] et al., who compared the effects of CPAP and MAD therapies for OSAS in the short term (1 month), compliance was higher with MADs, demonstrating significant improvements in sleepiness, driving simulator performance, and disease-specific quality of life [34]. In a recent systematic literature review, [PERSON] et al. showed that compliance was higher with MADs than with CPAP [35]. Oral devices tend to be better tolerated by patients because they are less uncomfortable. Several clinical trials have also shown that compliance is higher with MADs than with CPAP in the long term.