Olfactory dysfunction is a cardinal symptom of chronic rhinosinusitis, a disease which affects 12.5% of the adult population across all racial and ethnic groups. Previous research has documented olfactory deficit in 68% of patients with chronic rhinosinusitis and 20% with complete anosmia, suggesting that olfactory dysfunction affects over 25 million individuals in the United States with chronic rhinosinusitis. This proposed investigation will be used to predict olfactory outcomes following treatments for chronic rhinosinusitis and gain insights into mechanisms of olfactory dysfunction in this population.

Inclusion Criteria:

• Adult ( > 18 years of age)
• A diagnosis of medical recalcitrant CRS as defined by 2015 Adult Sinusitis Guidelines outlined by the American Academy of Otolaryngology
• Provide written informed consent and authorization.
• Study participants must be able to complete consent, all study evaluations, olfactory testing, and study-related health questionnaires written in the English language.
• Patients must self-select subsequent treatment option (endoscopic sinus surgery or continued medical therapy) to be dictated by the disease process and judgment and preferences of each individual, following counseling for each treatment option.
• Present to the enrolling site with indication for a CT scan or a CT scan completed, off-site, from another provider
• Complete appropriate standardized medical treatment by the Interim Assessment, 6-week follow-up period including, but not limited to, at least one course of either topical corticosteroids (>21-days) or a 5-day course of oral corticosteroid therapy, and at least one course (>14-days) of culture-directed or broad spectrum antibiotic therapy.

Exclusion Criteria:

• Children (< 18 years of age)
• Any patient unable and/or unwilling to complete questionnaires or clinical testing or cooperate with all study protocols.
• Non-English speaking / English translation services required
• Unwilling or unable to provide informed, written consent.
• Contra-indications for any type of continued medical therapy required for treatment of symptoms related to CRS
• Patients who have not undergone previous prescribed medical therapy as described in Inclusion Criteria.
• Individuals of any vulnerable population including: children, pregnant women, neonates, decisionally impaired adults, or prisoners.

Patients who present in clinic with indications of medically refractory chronic sinusitis.