--- title: "Endoscopic Anatomy of the Nose for FESS" description: "ENT notes on the Endoscopic Anatomy of the Nose for FESS." source: "The ENT Resident" author: "Dr. Mausumi Das" canonical_url: "https://www.theentresident.com/ent-notes-lectures/endoscopic-anatomy-nose-fess" categories: ["Rhinology"] video: "https://www.youtube.com/watch?v=cDBmYHE2zEE" image: "https://media.theentresident.com/og-images/endoscopic-anatomy-nose-fess.png" --- # Endoscopic Anatomy of the Nose for FESS ENT notes on the Endoscopic Anatomy of the Nose for FESS. Watch the full video lecture on YouTube: https://www.youtube.com/watch?v=cDBmYHE2zEE ## 👃 Endoscopic Anatomy of the Nose This post covers the anatomy that is relevant while performing **Functional Endoscopic Sinus Surgery (FESS)**. ### 🔍 Middle Turbinate ⭐ The middle turbinate is a **boomerang shaped structure**, bending in different planes. It has **three parts**, each lying in a different plane with a different attachment. | Part | Location | Plane | Attachment | | --- | --- | --- | --- | | **First part** | Anterior one-third (vertical) | **Sagittal** | Cribriform plate, at the junction of the medial and lateral lamella; sometimes also the frontonasal process of the maxilla | | **Second part** | Middle one-third (oblique) | **Coronal** | Lamina papyracea (medial orbital wall) | | **Third part** | Posterior one-third | **Horizontal (axial)** | Lamina papyracea and the perpendicular plate of the palatine bone | > What is Basal Lamella or Ground Lamella? What is the clinical significance of Basal Lamella? --- ### 🔍 Osteomeatal Complex (OMC) ⭐ A key structure in the endoscopic anatomy of the nose. It is the area into which the **frontal sinus, maxillary sinus and anterior ethmoidal sinus** drain. #### Structures Forming the Osteomeatal Complex 1️⃣ **Uncinate process** A **sickle shaped bone** running from an **anterosuperior** to a **posteroinferior** direction. > What are the different variations of the Superior Attachment of the Uncinate Process? How does this impact the drainage of the Frontal sinus? > What is Recessus Terminalis? 2️⃣ **Bulla ethmoidalis** An **anterior ethmoidal cell** lying just **behind the uncinate process**. ⭐ It is the **largest and most constant** anterior ethmoidal cell, and is usually well pneumatized. > What are the variations of the Bulla Ethmoidalis seen? 3️⃣ **Hiatus semilunaris Inferioris** A **semilunar groove** between the **uncinate process** in front and the **bulla ethmoidalis** behind. ⭐ It is a **two dimensional space**, about **1 to 2 mm** wide. ⭐ The hiatus semilunaris **leads into the infundibulum**. 4️⃣ **Ethmoidal infundibulum** ⭐ A **three dimensional space**. > What are the boundaries of Ethmoidal infundibulum? > Which sinuses drain into the Ethmoidal infundibulum? --- ### 🔍 Ethmoidal Complex ⭐ The **basal lamella** divides the ethmoidal complex into anterior and posterior ethmoidal cells. | Ethmoidal Cells | Drain Into | | --- | --- | | **Anterior ethmoidal cells** | Middle meatus | | **Posterior ethmoidal cells** | Superior meatus | > Name the ethmoidal cells extending towards Maxillary, Frontal & Sphenoid sinuses. --- ### 🔍 Sinus Lateralis of Grunwald Formed by two recesses around the bulla ethmoidalis: | Recess | Location | | --- | --- | | **Suprabullar recess** | Space **above** the bulla ethmoidalis, between the bulla and the skull base | | **Retrobullar recess** | Space **behind** the bulla ethmoidalis, between the bulla and the ground lamella | 👉 Together these form a **semilunar space**, the **Sinus Lateralis of Grunwald**. > Where does the Sinus Lateralis of Grunwald open into? > What are the Boundaries of the Sinus Lateralis of Grunwald? --- ### 🔍 Agger Nasi Cell A **bony mound** on the ethmoid, situated at the point where the **middle turbinate attaches to the lateral nasal wall**. 👉 When this bony mound becomes **pneumatized**, it forms the **agger nasi cell**. > What does the Agger nasi cell look like on endoscopy? > What is the clinical significance of Agger nasi cell? --- ### 🔍 Haller Cell An **anterior ethmoidal cell** pneumatizing into the **floor of the orbit**, just **above the maxillary ostium**. Also known as **Infraorbital Ethmoid Cell**. > What is the clinical significance of Haller cell? --- ### 🔍 Supraorbital Ethmoid Cell An **anterior ethmoidal cell** extending **superiorly and laterally over the orbital roof**. ⭐ On a coronal view, it gives the appearance of a **septated frontal sinus**. > What is the clinical significance of Supraorbital Ethmoid cell? #### Two Openings in the Frontal Recess When a supraorbital cell is present, the frontal recess shows **two openings**: | Opening | Structure | | --- | --- | | **Medial** | Frontal sinus opening | | **Lateral** | Supraorbital cell opening | --- ### 🔍 Onodi Cell (Sphenoethmoidal Cell) A **posterior ethmoidal cell** pneumatizing **superior and lateral to the sphenoid sinus**. ⭐ Unlike the other cells discussed, the Onodi cell is a **posterior** ethmoidal cell. > What is the location of Sphenoid sinus in relation to Onodi cell? > What is the clinical significance of Onodi cell? #### Radiological Identification 👉 On the **coronal view** of a CT scan, the Onodi cell gives the appearance of a **horizontal septation**. ⚠️ It may be mistaken for the true sphenoid sinus, leading to an **incomplete dissection**. --- ### 🔍 Frontal Recess #### 🔍 Definition A **narrow, funnel shaped space** forming the **drainage pathway connecting the frontal sinus to the middle meatus**. #### ⭐ Hourglass Configuration On a **sagittal section**, three structures form an **hourglass configuration**: | Part | Position | | --- | --- | | **Frontal infundibulum** | Above | | **Frontal ostium** | Constricted middle part | | **Frontal recess** | Below | ⭐ The **frontal ostium** lies **posteriorly**, at the **medial end of the floor of the frontal sinus**. > What are the Boundaries of the Frontal Recess? --- ### 🔍 Frontal Cells ⭐ The presence of frontal cells can impact the **drainage of the frontal recess**. **Classifications** | Classification | Description | | --- | --- | | **Kuhn's classification** | Four types of frontal cells; later modified by **Wormald** | | **IFAC classification** | The classification **currently followed**, based on the **anatomic origin** of the cells | > [What is Kuhn's Classification of frontal cells?](https://www.theentresident.com/ent-notes-lectures/modified-kuhn-classification-frontal-cells.md) > What is Modified Kuhn's Classification of frontal cells? > [What is the IFAC classification of frontal recess cells?](https://www.theentresident.com/ent-notes-lectures/international-frontal-sinus-anatomy-classification-frontal-recess-cells.md) --- ### 🔍 Maxillary Sinus Ostium Two ostia are described: 1️⃣ **Natural ostium** * Drains into the **inferior part of the ethmoidal infundibulum**, at a **45 degree angle** * Lies **just below the orbital floor**, in the **medial wall** of the sinus * Lies **halfway between the anterior and posterior walls** of the sinus ⭐ Maxillary sinus mucociliary flow is **always towards the natural ostium**. > What is the position of natural maxillary ostium within the Ethmoidal Infundibulum? > What are the Relations of the natural maxillary ostium? What is the clinical importance of knowing the relations? 2️⃣ **Accessory ostium** 👉 **Accessory ostia** lie in the anterior and posterior fontanelles. > What are fontanelles? Where do the anterior and posterior fontanelles lie? > How will you differentiate between Natural maxillary Ostium and Accessory maxillary Ostium? ⚠️ An ostium seen **before uncinectomy** is most likely an **accessory ostium**, and must not be mistaken for the natural ostium. > What is Mucus Recirculation Phenomenon? --- ### 🔍 Sphenoid Ostium * Drains into the **sphenoethmoidal recess** * The sphenoethmoidal recess lies **medial to the inferior third of the superior turbinate** * The ostium lies **medial and posterior to the superior turbinate** * Located about **halfway to two-thirds up the anterior wall** of the sphenoid sinus > What are the Landmarks to locate the Sphenoid Ostium? --- ### 🧠 Viva Pearls * The middle turbinate is boomerang shaped and has three parts in three different planes. * The first part lies in the sagittal plane and attaches to the cribriform plate. * The second part lies in the coronal plane and attaches to the lamina papyracea; it is the basal or ground lamella. * The basal lamella separates the anterior from the posterior ethmoidal cells. * The third part lies in the horizontal plane and attaches to the lamina papyracea and the perpendicular plate of the palatine bone. * The osteomeatal complex consists of the uncinate process, bulla ethmoidalis, hiatus semilunaris and ethmoidal infundibulum. * Bulla ethmoidalis is the largest and most constant anterior ethmoidal cell. * Hiatus semilunaris is a two dimensional space; the infundibulum is a three dimensional space. * Maxillary sinus drains into the inferior aspect and frontal sinus into the superior aspect of the infundibulum. * The uncinate process is sickle shaped, running anterosuperiorly to posteroinferiorly. * Anterior ethmoidal cells drain into the middle meatus; posterior ethmoidal cells into the superior meatus. * Suprabullar and retrobullar recesses together form the sinus lateralis of Grunwald. * Agger nasi is a bony mound at the attachment of the middle turbinate to the lateral nasal wall. * Agger nasi cell is the most anterior ethmoidal cell and the first landmark in frontal sinus surgery. * Haller cell is an infraorbital ethmoid cell. * Onodi cell is a posterior ethmoidal cell. * Onodi cell appears as a horizontal septation on the coronal CT. * Frontal infundibulum, frontal ostium and frontal recess form an hourglass configuration. * An ostium visible before uncinectomy is most likely an accessory ostium. --- ## About This Note This free ENT note on Endoscopic Anatomy of the Nose for FESS was written by Dr. Mausumi Das and is paired with a corresponding video lecture. 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