Rhinosinusitis

FreeMedSite USMLE STEP 1 REVIEW

Definition

Inflammation of the nasal cavity and one or more paranasal sinuses, usually caused by obstruction of drainage.

Pathophysiology

Obstruction → Mucus Stasis → ↓ O₂ Tension → Bacterial Overgrowth

Exam Alert: Maxillary Predilection
The Maxillary sinus ostium is superomedial. Because drainage is against gravity, it is the most common site for infection.

Drainage Anatomy

Meatus	Structures Drained
Superior	Sphenoid + Post. ethmoid
Middle	Frontal + Maxillary + Ant. ethmoid
Inferior	Nasolacrimal duct

💡

Focus: Middle Meatus = High Yield

Etiology

Most Common

Viral (Acute)

e.g., Rhinovirus

Secondary

Bacterial Pathogens

• • S. pneumoniae (MC)
• • H. influenzae
• • Moraxella catarrhalis

Clinical Features

🤕 Facial Pain/Pressure

👃 Purulent Discharge

🚫 Anosmia (↓ Smell)

🤒 Fever (Variable)

Complications

Spread via thin bony walls or venous channels:

👁 Orbital

Cellulitis, proptosis, painful eye movement.

🧠 Intracranial

Cavernous sinus thrombosis, abscess, meningitis.

! EXAM PEARLS

MC SINUS Maxillary

MC DRAINAGE SITE Middle Meatus

MC OVERALL CAUSE Viral

MC BACTERIA S. pneumoniae