الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Rhinosinusitis (RS) is an extremely prevalent disorder that affects an estimated 14% of the adult population. RS is a significant and increasing health problem which results in a large economic burden, especially when recurs. It is thought to be more common in childhood than in adults. It affects all races and socioeconomic backgrounds. The incidence is higher in spring, winter, and fall than it is during the summer months (Anand, 2004).
CRS is an inflammatory disease of the mucosa of the nose and paranasal sinuses that is present for at least 12 weeks. The precise pathophysiology is unclear, many causes have been proposed, including environmental and genetic factors, anatomic variations, microbial colonization, superantigens, biofilms, fungal stimulation, atopic response, immunodeficiency, and disturbances in mucociliary clearance. Whatever the predisposing causes, there is general agreement that the disease process and patient symptoms are exacerbated by bacterial and fungal contamination in the sinuses (Kennedy, 2004).
Diagnosis of CRS is based on the presence of two sinonasal symptoms in association with clinical or radiological evidence for sinonasal inflammation. Two of the following symptoms should be present: nasal secretions, nasal obstruction, facial pain, or smell dysfunction. Nasal endoscopy and imaging are major criteria for every patient suspected of CRS as subjective complaints and objective findings do not always correlate (Fokkens et al., 2007).
Treatment of CRSwNP is a controversial topic. Most of the authors agree on primary medical management. Medical interventions vary and include antimicrobials, topical and systemic steroids, antihistamines, decongestants, leukotriene antagonists and nasal saline irrigation (Soler et al., 2011).
Corticosteroids form the core of medical management. Their effectiveness is due to a combination of anti-inflammatory effects, including the reduction of proinflammatory mediators, increased gene transcription, reduction of airway inflammatory cell infiltrates, and suppression of the production of chemotactic factors. Systemic steroid therapy is effective even on a short-term basis. Oral corticosteroids as single agents have short-term effects on symptoms and polyp size, necessitating repeated treatments, however, short courses of oral steroids should not be given more than 3 or 4 times per year (Lal and Hwang, 2011).
INCs administered by a spray lack systemic side effects, middle meatal penetration appears to be low and their benefits can be further diminished by poor adherence and postoperative edema, discharge, or crusting. MF is the only topical nasal steroid approved by the FDA for the treatment of NP at daily dose of 200 μg. Because the existing topical methods of intranasal delivery of steroids are suboptimal, new ways to deliver corticosteroids and other medications directly to the nasal mucosa in a con¬trolled fashion are actively being investigated (Aukema et al., 2005).
Surgery is adjunctive to medical therapy and considered in those who do not respond or have poor tolerance of medical therapy. The goal of surgical therapy is to improve the drainage and ventilation of the sinuses through their natural ostia (Otto and DelGaudio, 2010).
The Propel mometasone eluting stent is the first FDA approved device for localized, controlled steroid delivery into the eth¬moid cavity following FESS. This implant is composed of MF embedded in a biodegradable polymer in a lattice pattern that expands in a spring-like fashion to conform to the walls of a dissected ethmoid cavity. A total of 370 μg of MF, is embedded in the polymer matrix and gradually released in a controlled fashion over 30 days. The polymer matrix, made of polylactide-co-glycolide (Kennedy et al., 2012).
The bioabsorbable characteristics of the stent have been studied by visual estimation, and have been shown to be resorbed in a predictable fashion. An average of 15% of stent material was present by day 30, and decreased to 0.2% after 60 days, showing successful absorption of the stent. MF is highly lipophilic and has been shown to reside in mucosal tissue for up to 60 days after stent placement. Another MF-eluting sinus implant with higher corticosteroid content releasing 1350 μg over 3 months has been shown to reduce inflammation and reestablish patency of sinuses reobstructed by polyps beyond the perioperative period, without risk of systemic exposure (Forwith et al., 2016).
Propel is able to simultaneously mechanically dilate and deliver topical ste¬roids to the postoperative sinus cavities. The stent is deployed within the middle meatus at the time of surgery or in the early postoperative period, and is designed to maintain the results of sinus surgery by decreasing postoperative inflammation, polyposis, adhesions, and middle turbinate lateralization. As a scaffold, the stent maintains medialization of the middle turbinate and prevents the development of scarring between the middle turbinate and the lateral nasal wall (Murr et al., 2011).