A 42-year-old woman with a 10-year history of allergic rhinitis and asthma presents with progressive nasal obstruction. Nasal endoscopy reveals multiple polyps. Which is the most common site of origin of nasal polyps in this patient?

Explanation

## Most Common Site of Origin of Nasal Polyps **Key Point:** The **ethmoid sinus** is the most common site of origin for nasal polyps, particularly in chronic rhinosinusitis with nasal polyposis (CRSwNP). Approximately 80–90% of nasal polyps originate from the ethmoid complex. ### Anatomical Origin of Nasal Polyps | Site | Frequency | Polyp Type | Characteristics | |------|-----------|-----------|------------------| | **Ethmoid sinus** | 80–90% | CRSwNP | Bilateral, multiple, pale | | **Maxillary sinus** | 5–10% | Antrochoanal | Unilateral, single, extends to nasopharynx | | **Sphenoid sinus** | <2% | CRSwNP | Rare, usually with extensive disease | | **Nasal septum** | <1% | Septal polyps | Very rare, may be traumatic origin | **High-Yield:** The **ethmoid sinus** is the most common site because: 1. Largest mucosal surface area in the sinonasal complex 2. Highest concentration of mucous glands 3. Most prone to chronic inflammation and edema 4. Anatomically predisposed to stasis and infection ### Anatomical Basis ```mermaid flowchart TD A[Nasal Polyp Origin]:::outcome --> B{Which sinus?}:::decision B -->|Ethmoid 80-90%| C[CRSwNP<br/>Bilateral polyps<br/>Lateral nasal wall]:::action B -->|Maxillary 5-10%| D[Antrochoanal polyp<br/>Unilateral<br/>Extends nasopharynx]:::action B -->|Sphenoid <2%| E[Rare<br/>Advanced disease<br/>Posterior obstruction]:::action B -->|Septum <1%| F[Very rare<br/>Traumatic/post-surgical]:::action ``` **Clinical Pearl:** When you see **bilateral nasal polyps**, think **ethmoid origin** with CRSwNP. When you see a **unilateral polyp extending into the nasopharynx**, think **antrochoanal polyp** from the maxillary sinus. ### Why Ethmoid Sinus? 1. **Largest mucosal surface:** The ethmoid complex has the greatest epithelial area 2. **Chronic inflammation:** Most susceptible to allergic and infectious triggers 3. **Anatomical drainage:** Poor drainage predisposes to stasis 4. **Mucous gland density:** High concentration of mucous glands 5. **Proximity to lateral nasal wall:** Polyps easily protrude into nasal cavity **Mnemonic:** **ETHMOID** = **E**thmoid is most common, **T**ypically bilateral, **H**igh mucosal surface, **M**ost inflammation-prone, **O**rigin of 80–90%, **I**nflammatory disease association, **D**rainage impairment. [cite:Scott-Brown's Otolaryngology Ch 5]