acute sinusitis

**Definition/Classification:** Acute <4 weeks; subacute 4–12 weeks; chronic >12 weeks; recurrent ≥4 episodes/year with symptom-free intervals.

**Pathophysiology:** Obstruction of the sinus ostia (ostiomeatal complex, which drains the maxillary, anterior ethmoid, and frontal sinuses) from mucosal edema, impairs mucociliary clearance. This causes mucus stasis, low oxygen tension, and bacterial overgrowth. Predisposing factors: viral URI (most common), allergic rhinitis, nasal polyps, deviated septum, cystic fibrosis, primary ciliary dyskinesia (Kartagener), immunodeficiency, dental infection (maxillary sinus), barotrauma, and intubation/nasogastric tubes (nosocomial).

**Etiology:** - Viral (90–98%): rhinovirus, influenza, parainfluenza - Bacterial: *S. pneumoniae*, non-typeable *H. influenzae*, *M. catarrhalis* (also *S. aureus* and anaerobes in dental-source disease) - Fungal: Think *Mucor/Rhizopus* in diabetic ketoacidosis or neutropenia. This is a medical emergency (rhinocerebral mucormycosis: black necrotic eschar, broad non-septate hyphae with right-angle branching). Treat with amphotericin B and surgical debridement. *Aspergillus* is another cause in immunocompromised patients. - Hospitalized/ventilated patients: gram-negative rods, *Pseudomonas*, *S. aureus*

**Clinical presentation:** Nasal congestion/obstruction, purulent nasal discharge, facial pain/pressure (worse bending forward), hyposmia, maxillary tooth pain, cough, and fever. Maxillary sinus is most commonly affected.

**Diagnosis:** Clinical. Imaging is NOT routinely indicated. CT is reserved for suspected complications, recurrent/chronic disease, or surgical planning. Bacterial criteria (any one): 1. Persistent symptoms ≥10 days without improvement 2. Severe symptoms: fever ≥39°C (102°F) with purulent discharge or facial pain for ≥3–4 consecutive days 3. "Double worsening": initial improvement followed by worsening within 10 days

**Management:** - Viral/mild: supportive care (saline irrigation, intranasal corticosteroids, analgesics, decongestants short-term). Avoid prolonged topical decongestant use (rhinitis medicamentosa). - Bacterial: watchful waiting is an option in uncomplicated cases. Otherwise, first-line is amoxicillin ± clavulanate (amox-clav favored if resistance risk). Penicillin-allergic: doxycycline or a respiratory fluoroquinolone (levofloxacin, moxifloxacin). Avoid macrolides and TMP-SMX because of resistance. Duration is typically 5–7 days.

**Complications (high-yield):** - Orbital cellulitis (most common complication, especially from ethmoid sinusitis via the lamina papyracea): proptosis, ophthalmoplegia/pain with eye movement, decreased vision. Needs CT and IV antibiotics. - Cavernous sinus thrombosis: bilateral ocular findings, CN III, IV, V1, V2, VI palsies, fever, headache. Spread via valveless facial/ophthalmic veins. - Meningitis, epidural/subdural empyema, brain abscess (frontal lobe from frontal sinusitis) - Pott puffy tumor: frontal bone osteomyelitis with subperiosteal abscess, causing forehead swelling - Chronic sinusitis

**Differential:** Allergic rhinitis, viral URI, dental abscess, migraine/cluster headache, temporal arteritis, trigeminal neuralgia, and nasal foreign body (unilateral purulent discharge in children).

**Boards pearls:** - Most cases are viral and need no antibiotics. - Transillumination and plain films have poor sensitivity/specificity. - Aspirin-exacerbated respiratory disease (Samter triad): asthma, nasal polyps, aspirin sensitivity. - Chronic rhinosinusitis with nasal polyps in a child → test for cystic fibrosis. - Unilateral sinusitis with ethmoid/orbital involvement in a diabetic or neutropenic patient → think mucormycosis.