Introduction
Antrochoanal polyps (ACPs) are benign polypoidal lesions originating from the mucosal lining of the maxillary sinus.[1] It is usually found on one side nasal cavity and is solitary in nature. It comes from the maxillary sinus to the nasal cavity through the accessory ostium and extends towards the choana.[1] ACPs usually have two parts such as cystic, which frequently fills the maxillary sinus, and the other solid polypoidal part, which extends into the middle meatus and the nasopharynx.[2] ACP is usually unilateral, although a few patients with bilateral ACPs were documented in the medical literature, mainly among children.[3] The common clinical manifestations in children with ACPs are nasal obstruction and nasal discharge.[4] In severe cases, it may manifest with epistaxis, dyspnea, dysphagia, and weight loss.[4] In children, juvenile nasopharyngeal angiofibroma, encephalocele, nasopharyngeal malignancies, grossly enlarged adenoid hypertrophy, turbinate hypertrophy, and nasal polyposis are considered the differential diagnosis of ACP.[5] Diagnostic nasal endoscopy, CT scan, and MRI are the main diagnostic techniques for ACPs.[6] The treatment of ACP in children is surgical and most surgeons prefer being conservative in the surgery of ACP in children. This review article aims to discuss the epidemiology, etiopathology, clinical presentations, investigations, and treatment of ACPs among children.
Methods of Literature Search
Multiple systematic methods were used to find current research publications on the antrochoanal polyp among children and its epidemiology, etiopathology, clinical manifestations, and management. We started by searching the Scopus, PubMed, Medline, and Google Scholar databases online. A search strategy using PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analysis) guidelines was developed. This search strategy recognized the abstracts of published articles, while other research articles were discovered manually from the citations. Randomized controlled studies, observational studies, comparative studies, case series, and case reports were evaluated for eligibility. There were a total number of articles 88 (27 case reports;23 cases series; 38original articles) [Figure 1]. This paper focuses only on the details of ACP among children. This review article describes the epidemiology, etiopathology, clinical presentations, investigations, and treatment of ACP among children. This analysis provides a better understanding of ACP among children and its clinical profile along with its management. It will also catalyze further study of the etiopathogenesis of ACPs among children and the development of a newer surgical technique for the management of this polyp.
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Figure 1:: Flow chart showing methods of literature search
History
In 1691, Fredrik Ruysch described two cases of nasal polyps arising from the maxillary sinus.[7] In 1891,Zuckerkandl documented a case of a polyp originating from the maxillary sinus and coming out through a wide accessory ostium.[8] ACPs were described by Paefyn in 1713.[8] However, Killian is commonly credited with first documenting this clinical entity in 1906.[9]
Epidemiology
The incidence and prevalence of ACPs have been poorly investigated. In the general population, ACPs are found approximately 4 to 6% of all nasal polyps.[2] ACPs are most commonly found in children and young adults.[10] ACPs constitute around 35% of nasal polyps in children without a clear gender difference.[11]Approximately 48.2% of cases of ACPs are seen in children.[12] Approximately 40% of the patients with ACPs are in the range of 30 to 65 years.[12] Another study showed that ACPs may occur in any age group.[13] ACPs are more common in males than females.[13] There is a slight predominance of the ACPs in the left maxillary sinus among both children and adult age groups.[14] Another study showed that 33% of all nasal polyps are ACPs in children.[15]
Etiopathology
Although different hypotheses have been described, the etiopathogenesis for the ACPs is still unclear. The majority has accepted the “blocked acinus theory”:it is thought that ACPs arise from the antral cysts development occurred by acinar mucus gland blockage as a result of chronic phlogosis (allergic or infectious).[16]Closure of the osteomeatal complex/middle meatus level decides an increase in pressure in the maxillary sinus or High moro antrum forcing the herniation of the polyp into the nasal cavity via the accessory ostium [Figure 2].[13] Others documented that lymphatic obstruction, whether primary(area of higher tissue pressure) or secondary to chronic sinusitis might play an important role inthe development of ACPs.[11] Chronic sinusitis and allergy have been implicated in the development of ACPs. Lee and Huang documented that 65% of the patients with ACP had chronic sinusitis.[17] ACPs are inflammatory polyps originating from the mucosa of the maxillary sinus. It has two components such as the antral part which is cystic and the nasal part is a solid one. The cystic component usually arises from the posterior, inferior, lateral, or medial walls of the maxillary sinus, and it attaches to the solid part of the ACP in the nasal cavity.[18] One study showed that the most common site of origin of ACP is the posterior wall of the maxillary sinus.[19] The most common etiology of ACP in children is chronic inflammatory bacterial diseases and/or cystic fibrosis. Allergy is an uncommon etiology for the development of ACP.ACPs which could develop from an expanding intramural cyst in the maxillary sinus may cause maxillary sinusitis and osteomeatal complex disease when the polyp expands to impede the maxillary sinus ostium or hinder the mucociliary function of the mucosa in the sinus. Chronic maxillary sinusitis, instead of being the cause of ACPs, could be the result of blockage of the maxillary sinus ostium by ACPs.[17] Some authors showed a statistically significant association of ACP with allergic diseases. Cook et al. reported allergic rhinitis in approximately 70% of their patients with ACP.[20] Chen et al. documented that allergic disease plays an important role in ACP.[16] However, other authors found no association between allergy with ACP.[21] There is a possible role of the urokinase type plasminogen activator and inhibitor in the etiopathogenesis of the ACPs.[22] There is also the role of arachidonic acid metabolites in the pathogenesis of the ACP.[23] One recent study showed decreased lipoxygenase pathway products in the pathogenesis of the ACP.[23]
Figure 2:: Flow chart showing development of the ACP
Clinical Manifestations
ACPs are most commonly found in children and young adults.[1] Left-sided ACPs are more common than the right side.[17,24] A study showed a male predominance of ACPs whereas others noted a female preponderance.[24] The common clinical presentations are often similar to several other diseases of the paranasal sinuses such as nasal obstruction, nasal discharge, headache, and snoring.[25] The most common symptom of the patient with ACP is nasal obstruction.[25] The nasal obstruction may be unilateral or bilateral. If the ACP is very large,it may occupy the whole nasopharynx and block both choanae resulting in bilateral nasal obstruction.[26] ACPs are almost always unilateral; there are very few published cases of bilateral ACPs in the medical literatures.[27] Other clinical presentations of children with ACPs are sleep apnea, mouth breathing, post-nasal discharge, epistaxis, dyspnea, and hyposmia.[28] The nasal discharge is usually a mucous or mucous-purulent secretion.[29] Patients of ACPs presenting with epistaxis should be excluded from angiofibroma in male pediatric age and malignancy in adult and elderly age groups.[30] Obstructive sleep apnea is uncommon at an early stage of ACPs among children in contrast to the adult age group. There are three explanations for this issue. First, the higher mean age of pediatric patients has a significantly larger size of the nasopharynx in comparison to the younger age group with adenoid enlargement. Secondly, there is incomplete obstruction of the nose by ACPs. The third explanation is that ACPs of pediatric age present less often with apnea than adult age groups.[7] It may obstruct the eustachian tube opening at the nasopharynx, thus resulting in secretory otitis media.[18] There may be associated with epistaxis in the case of infected ACP.[31,32] Anterior rhinoscopy usually shows ACP as a unilateral polyp.[33] Sometimes is so large that ACP may be seen behind the uvula in the oropharyngeal examination.[34]
Diagnosis
Patients with ACP require a careful history taking, diagnostic nasal endoscopy, and radiological tests to confirm the diagnosis. History of nasal obstruction, nasal discharge, snoring, anosmia and mouth breathing in children often prompt the clinicians to rule out ACP.[25] The diagnostic nasal endoscopy and computed tomography (CT) scan are the gold standard tools for the diagnosis of ACPs.[10] By using a CT scan, the diagnosis of ACP is made when a mass fills the maxillary sinus growing through the accessory or natural ostium into the middle meatus and choana [Figure 3]. In MRI, it shows T1 hypointense and T2 enhanced signals in ACPs. If intravenous contrast with gadolinium is administered during MRI, the intra-sinusal cystic part of the ACP is only peripherally enhanced, whereas the nasal and choanal parts show hypointense images.[34] The ACPs are classified into three patterns in the CT findings such as Stage I(antronasal polyp);stage II(where ACP extends into the nasopharynx and the ostium of the maxillary sinus is blocked fully by the neck of the ACP); stage III(ACP extended into the nasopharynx and the ostium of the maxillary sinus is blocked partially by the neck of the ACP).[35] The biopsy and histopathological study are helpful for the definite diagnosis of the ACPs. Macroscopically, ACP is composed of a cystic part filling the maxillary sinus and a solid part coming out via the maxillary ostium into the middle meatus and extending towards the nasopharynx. Histologically, there is essentially a difference between ACP and nasal polyp. The mucosal surface of the ACP is formed by the respiratory epithelium. The ACP often contains sparse mucous glands and has a myxoid stroma with variable densities of inflammatory cells concentrated near the surface. Sometimes, secondary stromal alterations may occur such as prominent fibrovascularity, neovascularization, and thrombosis, which may result in difficulty in the differential diagnosis.[36] The polyp surface is covered by respiratory epithelium. From per histological point of view, nasal polyps can be classified into four types:(1) edematous, eosinophilic or allergic is the most common type, formed by edematous connective tissue and isolated glands, without the development of cysts with a rich eosinophilic infiltrate and goblet cell hyperplasia;(2) ductal, formed by glands and cysts;(3) fibrous or fibro-inflammatory, with a proliferation of fibroblasts and collagen, and a lymphocyte inflammatory infiltrate; and (4) polyps with stromal atypia, which are very scared and differentiated from genuine neoplasms by the lack of the mitosis.[37]
Figure 3:: CT scan of the paranasal sinus showing left ACP
The differential diagnosis of the ACP includes different causes of unilateral nasal obstruction and ipsilateral nasal masses. The differential diagnosis of ACPs includes juvenile nasopharyngeal fibroma, olfactory neuroblastoma, meningoencephalocele, or hemangioma.[38] Inverted papilloma is usually a unilateral lesion that should be differentiated from the ACP. Other lesions such as lymphoma, Wegner granulomatosis, or rhabdomyosarcoma should also be considered for differential diagnosis.[39,40]
Treatment
The treatment of ACPs in children is essentially surgical. The treatment of ACP is surgery based, and there are several access approaches to the polyp. Historically, surgical treatment has involved two different approaches such as simple avulsion of the polyp or the Caldwell Luc procedure. Simple avulsion of the ACP alone carries a high rate of recurrence.[41] So, the antral portion of the ACP should be excised completely to avoid recurrence. There is controversy regarding the route of removal of the antral part of the ACP. The Caldwell Luc procedure provides good exposure and ensures complete removal of the antral part of the ACP.[42] The Caldwell Luc technique is usually avoided in the pediatric age group because of the risk of injuring anterior dental roots and maxillary growth centers. In children, the Caldwell Luc procedure gives significant risks to the development of teeth and bone growth centers of the maxilla. There are also other possible side effects of the Caldwell Luc procedure are cheek swelling, anesthesia of the cheek and maxillary teeth, and long recovery time.[43] The types of surgical techniques are decided by the endoscopic accessibility for the antral part of the ACPs. Functional endoscopic sinus surgery (FESS) has been shown to be a safe and effective technique for the treatment of ACPs. FESS has been widely accepted for the treatment of ACPs in children.[44] It includes excision of the polyp(trans-nasally or trans-orally depending on the size) and treatment of the obstructed osteomeatal complex. Other external approaches are the Caldwell Luc procedure, mini-Caldwell Luc, or trans-canine sinuscopy can be used alone or associated with endoscopic surgery.[45] FESS consists of endoscopic excision of the nasal part of the polyp and cystic antral part with attachment to the wall of the maxillary sinus via the middle meatus.[13] During performing FESS, the lower part of the uncinate process is removed and then the maxillary ostium is widened for exposure of the maxillary sinus. The antral part of the ACP is excised byan endoscopic approach via the natural ostium after its adequate widening. However, in some cases of ACPs, the antral part of the ACPs is difficult to access endoscopically, so excised through the opening via the canine fossa. Some prefer a combination of FESS and the Caldwell Luc approach for the treatment of ACPs. One study showed that recurrence may be found in a few cases by only the FESS approach yet not found recurrence after the combined FESS and Caldwell Luc or trans-canine sinoscopy approach.[46] Another study used a mini-Caldwell Luc approach with FESS in their study patients.[47] They reported minimal recurrence and a low complication rate, so this technique is helpful to remove the ACPs completely.[47] Hong et al. recommended powered instruments during FESS for the effective surgical outcome and found an improvement rate of 96.4% and no significant complications when powered instrumentation was used.[48] Combined endoscopic middle meatal surgery and trans-canine sinuscopy are helpful for the removal of the residual tissue of the ACPs from the maxillary antrum. Lee and Huang performed a trans-nasal endoscopic approach for ACPs originating from the posterior and inferior walls of the maxillary sinus and they also used a combined endoscopic and trans-canine approach for ACPs originating from the lateral walls of the maxillary sinus and recurrent cases. They reported the success rate of the trans-nasal endoscopic approach and combined endoscopic with the trans-canine approach as 76.9% and 100% respectively.[49] The use of a micro-debrider though canine fossa is helpful to resect a broad attachment of the ACP in the maxillary sinus and it may be indicated as complementary to endoscopic sinus surgery.[49]
Prognosis
There is a risk of recurrence postoperatively in the case of ACPs. Recurrent ACP often occurs depending on the re-growth of the residual polypoidal tissue in the maxillary sinus.[3] One study showed a recurrence rate of 14% in children with ACPs who underwent only endoscopic sinus surgery.[50] In the same study, the combined approach was done in some patients, and the recurrence rate was reduced to 8%.Another study determined that the recurrence rate was 11.1% in children who only underwent endoscopic sinus surgery, and the recurrence rate was 6.9% in adults who had undergone a combined surgical approach.[12] One study showed that Mitomycin-C application on the wall of the maxillary sinus after complete removal of the ACP reduces the chance of recurrence.[51]
Conclusion
Antrochoanal polyp (ACP) should be considered in the differential diagnosis for any child presenting with nasal obstruction and a nasal mass. It requires a careful history, diagnostic nasal endoscopy, and radiological tests to confirm the diagnosis of ACP. Endoscopic sinus surgery with middle meatal antrostomy combined with trans-canine sinoscopy helps the complete removal of the antral part of the ACP. Although more effective and safe surgical techniques have been developed, recurrences of ACPs in children are still high.
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Conflicts of interest
There are no conflicts of interest.
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