The duration of this acute illness is generally 7 to 10 days, with subsequent total resolution. However, a patient with exaggerated symptoms in that early period may have acute bacteria sinusitis. If the initial acute upper respiratory infection does not resolve after 21 days, a subacute sinusitis can be diagnosed. Disease persisting after 6 weeks is classified as a chronic sinusitis. Sphenoid sinuses are present by 2 years, and frontal sinuses start forming by 6 years of age.
Adolescent patients have more completely developed sinuses.
The maxillary drainage involves a cilia-dependent upward movement that joins the drainage of the anterior ethmoid air cells in a functional unit called the ostiomeatal complex. This area is thought to be a focus of edema during a viral illness, resulting in obstruction of the maxillary, frontal and anterior ethmoid drainage. The ostiomeatal unit is also susceptible to obstruction because of anatomic problems or local noninfectious inflammation, especially with allergic rhinitis. The presence of these bacteria within the nasal cavity is common in children, especially those exposed to day care centers. Sinusitis occurring during the first week of upper respiratory infection is usually viral in origin.