Sinus physiology depends on three factors: quality and quantity of secretions, mucociliary transport and ostiomeatal unit’s (OMU) patency. If these functions are normal, sinuses function properly. However, many times, a number of agents affect these functions, causing symptoms-sinus infections. The study of these causes is called etiology. These causes are divided into two groups: local and environmental. Environmental factors include exhaust fumes, cigarette smoke and other air pollutants, and swimming.

There are a number of local factors causing symptoms-sinus infections. Craniofacial anomalies, such as velopharyngeal insufficiency, cleft palate and choanal atresia, may lead to sinusitis.  Nasal obstruction due to rhinitis medicamentosa, tumors, adenoid infection, foreign bodies, polyps and rhinitis cause sinusitis. Ethmoid bulla prominence, atelectatic maxillary sinus, paradoxic middle turbinate, Haller’s cells, concha bullosa and septal deviation are common examples of anatomic aberrations triggering sinusitis. Ciliary dyskinesias, surgery, dental infection and barotrauma may also lead to sinusitis.

The anatomical aberrations reduce the size of bony channels, enhancing the risk of developing the sinus infection. For instance, concha bullosa, a common cause of recurrent sinusitis, compresses the uncinate process, obstructing the infundibulum and middle meatus. As a result, symptoms-sinus infections develop. If convex side of the bent middle turbinate touches the lateral nasal wall, uncinate process compresses and the OMU gets obstructed. Haller’s cells, also called infra-orbital cells, obstruct the maxillary ostium and infundibulum. The ethmoidal cell prominence may impair the drainage of the sinuses.

Mucociliary transport process clears the sinuses and enables proper movement of secretions from sinuses to nose to nasopharynx. Neither bacterial infections nor fall in inspiratory air humidity reduces the transport directed to the ostia of the sinus. However, obstructions, especially that of ostia, initiate a cycle of malfunctioning of sinuses, say secretions are retained within the sinuses, leading to chronic sinusitis.

Cilia, hair like structures on the cell surface of the respiratory tract, are responsible for removing dirt and mucus. Appropriate movement of the mucus lining within the sinuses prevents from infection development. The mucus lining and cilia shall work as a unit for correct movement. Ineffective cilia transportation and movement cause the diseases like dyskinesia, which means uncontrollable symptoms like compulsive or repetitive movements.

Primary ciliary dyskinesia (PCD) means disorders related to the cilia structure.  For example, Kartagener’s syndrome is a type of PCD. The syndrome encompasses the triad of sinusitis, bronchiectasis and situs inversus. The structure defects related to cilia include absence / less amount of the adenotriphosphate required for the cilia movement, cilia of abnormal length, lack of radial spokes and distorted basal apparatus.