Abstract
Sinusitis is defined by inflammation of the mucosa of the paranasal sinuses. In addition to the sinuses, the inflammation almost always involves the nasal cavity, and thus the term rhinosinusitis is often used interchangeably with sinusitis [1]. For the remainder of this chapter, the term rhinosinusitis will be used. Rhinosinusitis is further separated into three classifications based on duration and recurrence of symptoms [2].