chronic sinusitis

**Definition:** Symptoms ≥12 weeks (acute <4 weeks; subacute 4–12 weeks; recurrent acute ≥4 episodes/year with symptom-free intervals). Diagnosis requires symptoms plus objective documentation (purulence/edema/polyps on anterior rhinoscopy or nasal endoscopy, or mucosal thickening/opacification on CT).

**Pathophysiology:** - Obstruction of the ostiomeatal complex (drains frontal, maxillary, anterior ethmoid sinuses into the middle meatus) → impaired mucociliary clearance → mucus stasis, hypoxia, and inflammation. - Multifactorial: persistent mucosal inflammation (not simply chronic bacterial infection), epithelial barrier dysfunction, biofilms, allergy, and dysregulated immune responses. - CRSwNP is typically type 2 (Th2) inflammation: eosinophils, IL-4, IL-5, IL-13, and IgE. CRSsNP is more often neutrophilic/Th1-skewed. - Predisposing factors: allergic rhinitis, anatomic variants (deviated septum, concha bullosa), prior viral URI, smoking, dental infection (maxillary sinus), immunodeficiency (CVID, selective IgA deficiency), cystic fibrosis, primary ciliary dyskinesia (Kartagener syndrome), GERD, and aspirin sensitivity.

**Key associations (high-yield):** - **Samter triad / AERD (aspirin-exacerbated respiratory disease):** asthma + aspirin/NSAID sensitivity + nasal polyps (COX-1 inhibition → ↓PGE2, shunting to leukotrienes). - **Cystic fibrosis:** nasal polyps in a child → think CF (CFTR defect, thick mucus). - **Eosinophilic granulomatosis with polyangiitis (Churg-Strauss):** asthma, eosinophilia, sinusitis/polyps, p-ANCA. - **Granulomatosis with polyangiitis:** chronic sinusitis, saddle-nose deformity, c-ANCA, lung and renal involvement. - **Allergic fungal rhinosinusitis:** type I hypersensitivity to fungi (Aspergillus, Bipolaris), thick "allergic mucin," eosinophils, and CT showing hyperattenuating material. - **Kartagener syndrome:** dynein arm defect → chronic sinusitis, bronchiectasis, situs inversus, infertility.

**Microbiology:** - Acute: *S. pneumoniae*, *H. influenzae*, *Moraxella catarrhalis*. - Chronic: often polymicrobial, with *S. aureus*, anaerobes, and coagulase-negative staphylococci. Biofilm formation is common. - Pseudomonas, particularly in CF or immunocompromised patients. - Invasive fungal sinusitis (Mucor/Rhizopus): diabetic ketoacidosis or neutropenia → black necrotic eschar, a surgical emergency (treat with debridement and amphotericin B). Aspergillus is also a cause.

**Clinical features:** nasal congestion, thick discharge, postnasal drip, facial pressure, hyposmia/anosmia, halitosis, cough, fatigue, and sometimes ear fullness. Fever is less common than in acute sinusitis.

**Diagnosis:** Clinical plus anterior rhinoscopy or nasal endoscopy. CT of the sinuses is the imaging modality of choice (not plain films). Consider allergy testing, sweat chloride (CF), immunoglobulin levels, and biopsy/ANCA if vasculitis is suspected.

**Management:** - First-line: saline nasal irrigation + intranasal corticosteroids (mainstay). - Short courses of oral steroids for CRSwNP flares or perioperative use. - Antibiotics only for acute bacterial exacerbations or culture-directed therapy (amoxicillin-clavulanate is first-line for acute bacterial sinusitis). - Treat allergies, GERD, and other contributors. - Biologics for refractory type 2 CRSwNP: dupilumab (anti-IL-4Rα), omalizumab (anti-IgE), and mepolizumab (anti-IL-5). - Functional endoscopic sinus surgery (FESS) if medical therapy fails, to restore ostiomeatal drainage.

**Complications (high-yield):** Spread via thin bone, valveless emissary veins, and the ethmoid lamina papyracea. - Orbital: preseptal (periorbital) cellulitis → orbital cellulitis (proptosis, painful/limited extraocular movements, ↓ vision) → subperiosteal/orbital abscess. Ethmoid sinusitis is the most common source. - Intracranial: cavernous sinus thrombosis (ophthalmoplegia from CN III, IV, V1, V2, VI involvement, chemosis, fever), meningitis, epidural/subdural empyema, brain abscess. - Frontal sinusitis → Pott puffy tumor (subperiosteal abscess with frontal bone osteomyelitis). - Mucocele formation and osteomyelitis.

**Pearls:** Maxillary sinus is the most commonly infected (its ostium is high on the medial wall, so drainage is poor against gravity). Transillumination and plain films have poor sensitivity. Most acute rhinosinusitis is viral and resolves within 7–10 days. Suspect bacterial infection if symptoms persist >10 days without improvement, are severe (high fever, purulence ≥3–4 days), or "double-worsen."