Etiopathogenesis of antrochoanal polyp various theories

Etiopathogenesis: This disease is commonly seen only in non atopic persons. Its etiology is still unknown. Infact this disorder is not associated with nasal allergy.

Proetz theory: Proetz suggested that this disease could be due to faulty development of the maxillary sinus ostium, since it was always been found to be large in these patients. Hypertrophic mucosa of maxillary antrum sprouts out through this enlarged maxillary sinus ostium to get into the nasal cavity. The growth of the polyp is due to impediment to the venous return from the polyp. This impediment occur at the level of the maxillary sinus ostium. This venous stasis increases the oedema of the polypoid mucosa thereby increasing its size.

Bernoulli's phenomenon: Pressure drop next to a constriction causes a suction effect pulling the sinus mucosa into the nose.

Mucopolysaccharide changes: Jakson postulated that changes in mucopolysaccharides of the ground substance could cause nasal polyp.

Infections: Recurrent nasal infections have also been postulated as the cause for nasal polyp

Mill's theory:

Mills postulated that antrochonal polyp could be maxillary mucoceles which could be caused due to obstruction of mucinous glands.

Ewing's theory:Ewings suggested that an anomaly which could occur during maxillary sinus development could leave a mucosal fold close to the ostium. This fold could later be aspirated into the sinus cavity due to the effects of inspired air causing the development of antrochonal polyp.

Vasomotor imbalance theory: This theory attributes polyp formation due to autonomic imbalance

Polypoidal tissue from the maxillary antrum exits out through the accessory maxillary sinus ostium according to some workers. This accessory sinus ostium is placed posteriorly, which could be the reason for the polyp to present posteriorly. The accessory sinus ostium widens progressively, ultimately at one stage merging with the natural ostium of the maxillary sinus forming one huge opening into the maxillary antrum.

Infection / Inflammation:

This theory suggests that acinous mucous glands within the maxillary sinus cavity gets blocked due to infection / inflammtion involving the mucous lining of the sinus cavity. This leads to the formation of a cystic lesion within the maxillary sinus cavity. This cyst gradually enlarges to occupy the whole of the maxillary sinus cavity. It exits the sinus cavity by enlarging the accessory ostium and enters the nasal cavity. Usually these cysts arise from the antero inferior / medial wall of maxillary antrum.

Possible reasons for migration of antrochoanal polyp in to the post nasal space:

1. The accessory ostium through which the polyp gets out of the maxillary antrum is present posteriorly.

2. The inspiratory air current is more powerful than the expiratory air current thereby pushes the polyp posteriorly.

3. The natural slope of the nasal cavity is directed posteriorly, hence the polyp always slips posteriorly.

4. The cilia of the ciliated columnar epithelial cells lining the nasal cavity always beats anteroposteriorly pushing the polyp behind.