A 32-year-old woman presents with a 2-week history of nasal congestion, purulent nasal discharge, and facial pain over the maxillary region. CT PNS shows opacification of the maxillary sinus with air-fluid level. Which single feature best distinguishes acute bacterial sinusitis from chronic sinusitis in this patient?

## Distinguishing Acute from Chronic Sinusitis ### Temporal Criterion **Key Point:** The single most reliable discriminator between acute and chronic sinusitis is **symptom duration**. Acute sinusitis is defined as symptoms persisting for ≤4 weeks, while chronic sinusitis is defined as symptoms lasting >12 weeks (or recurrent episodes with symptom-free intervals). ### Comparison Table | Feature | Acute Sinusitis | Chronic Sinusitis | |---------|-----------------|-------------------| | **Duration** | ≤4 weeks | >12 weeks | | **Purulent discharge** | Common | May be present | | **Facial pain** | Prominent | Mild or absent | | **CT findings** | Air-fluid level, opacification | Mucosal thickening, polypoid changes | | **Etiology** | Viral → bacterial superinfection | Multifactorial (obstruction, allergy, biofilm) | | **Response to antibiotics** | Good | Poor | ### Why Duration Matters **High-Yield:** While purulent discharge, facial pain, and imaging opacification occur in both acute and chronic sinusitis, they are **non-specific findings**. Duration is the only feature that definitively separates the two entities according to the American Academy of Otolaryngology–Head and Neck Surgery (AAO-HNS) classification. **Clinical Pearl:** A patient with 2 weeks of purulent discharge and CT opacification still has acute sinusitis; a patient with 14 weeks of mild symptoms and normal imaging has chronic sinusitis. Time is the kingmaker. [cite:Ballenger's Oculomotor Rhinology 17e Ch 8]