Paranasalis

Paranasalis, commonly referred to as the paranasal sinuses, are a group of air-filled cavities within the bones of the skull and face that connect to the nasal cavity. The four paired groups are the maxillary, frontal, ethmoid, and sphenoid sinuses. They are lined with ciliated respiratory epithelium and mucus-secreting glands, producing mucus that drains into the nasal cavity. The sinuses are thought to contribute to several functions, including reducing skull weight, warming and humidifying inhaled air, acting as a resonating chamber for speech, and potentially providing a buffer against facial trauma.

Anatomy and drainage: Each sinus drains to the nasal cavity via narrow ostia. The frontal and maxillary sinuses typically drain into the middle meatus; the anterior and posterior ethmoidal sinuses drain into the middle and superior meatuses, respectively; the sphenoid sinus drains into the sphenoethmoidal recess above the superior concha. There is considerable anatomical variation in size, shape, and drainage patterns among individuals, which can influence susceptibility to infection and symptoms.

Development and variation: The maxillary sinus is present at birth, while the other sinuses develop and pneumatize at different stages of childhood and adolescence. Size, shape, and degree of pneumatization vary widely, with some individuals showing hypoplasia or extensive pneumatization. Anatomic variants can affect drainage routes and risk of obstructive sinusitis.

Clinical significance: Inflammation of the paranasal sinuses, or rhinosinusitis, is common and can be acute or chronic. Obstruction of sinus ostia, allergic inflammation, infections, and structural abnormalities can contribute to symptoms such as facial pain, nasal congestion, and reduced sense of smell. Imaging, particularly CT, is used to evaluate chronic sinus disease and guide surgical management, such as endoscopic sinus surgery to restore drainage.