1 Anatomy of Internal Nose & PNS in relation to Endoscopic Surgery Dr Vishav Yadav ENT

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Anatomy of Internal Nose & PNS in relation to Endoscopic Surgery

Dr Vishav Yadav

ENT

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Introduction

One of the most complex anatomy.The complications – non-familiarity with the

anatomical landmarks Besides clinical judgment and technical skills, a

competent surgeon must also be a good anatomist.

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Clinically two groups :

Anterior : Maxillary, frontal and anterior ethmoidal.

Posterior : Post. Ethmoidal and sphenoid sinuses.

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Developmental Anatomy

Macroscopic Anatomy

Endoscopic Anatomy

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Developmental anatomyNose : 4- 8 wks

4 – 5 wks

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Developmental anatomy

4-5 wks

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Secondary Palate Development - develop from vertical projection from maxillary

process(palatal shelves) - palatal closure progresses from anterior to posterior - the area between the junction of the pre-maxilla and the

palate remains incomplete during the prenatal life and thereafter : the incisive canal

- The posterior choana is repositioned more posteriorly

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Developmental anatomy The nasal capsule (skull base): cartilaginous envelope that

encases the developing nasal structures boundary to the nasal and paranasal sinus development. limited to the bounds of the perichondrium of the nasal capsule

or extends beyond the borders of the perichondrium with reabsorption.

Chondrification start in head mesenchyme at ant aspect of sphenoid bone , later involves lateral ethmoid

Then undergo ossification

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Developmental anatomy Paranasal Sinus Development : -The growth pattern is totally unpredictable -The paranasal sinuses, with the exception of the

sphenoid sinus, arise as evaginations from the lateral nasal wall.

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Paranasal Sinus Development

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During the 7th week the lateral nasal wall starts to develop.

A projection into the nasal capsule just superior to the palatal shelves appears first and is called the maxilloturbinal.

followed by five other ethmoturbinals and the nasoturbinal.

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The maxilloturbinal - inferior turbinate, The first ethmoturbinal originates at either the superior

aspect of the septum or the superior junction of the septum and the lateral nasal wall- middle turbinate.

The furrow between the maxilloturbinal and the first ethmoturbinal - middle nasal meatus. (an evagination of the lateral nasal wall produces a blind diverticulum) the embryonic infundibulum.

The second ethmoturbinal develops shortly after - the superior

turbinate. The furrow between the superior turbinate and the middle

turbinate is the superior meatus.

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The third ethmoturbinal is the precursor of the supreme turbinate (26% of adults) The supreme meatus is the furrow between the superior and

the supreme turbinates. The nasoturbinal is an additional prominence anterior and

superior to the ethmoid furrow or middle meatus and will develop into the agger nasi

Another mesenchymal ridge , uncinate process, develops on the superior and posterior border of the agger nasi.

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The uncinate process may extend superiorly to the roof of the anterior ethmoid bone and posteriorly along the superior surface of the inferior turbinate.

the ethmoturbinals form bony structures that traverse the ethmoid complex to attach to the lamina papyracea of the orbit and skull base. The furrows continue to grow, developing evaginations that contribute to the extensive and complex pneumatization of the ethmoid bone.

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Pneumatization: - Primary pneumatization -The maxillary bone, frontal bone,

ethmoid bone, and nasoturbinate bone (agger nasi) are invaded and filled with air from the ethmoid cells.

-Secondary pneumatization - epithelial-lined pockets expand into the adjacent bony structures for which the sinuses eventually will be named.

Primary pneumatization occurs during the chondrocranial stage. Much of the secondary pneumatization takes place postnatally.

The overall development of the paranasal sinuses is slow for the first 6 years

By age 12 to 14, most of the sinuses reach the adult size

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• Maxllary sinus : Secretion transport occur in a stellete pattern. Ostium opens into the floor of the post third of ethmoidal infundibulam which opens into middle meatus through hiatus semilunaris.

• Frontal sinus : Only sinus in which there is an active inwardly directed transportation of mucous. all the mucous leaves the sinus after one ‘round trip’ , which is the result of a WHORL like formation in the cilliary pattern. after passing through the ostium secretion is transported through a narrow cleft called frontal recess.

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Ethmoidal and Sphenoidal sinus : Secretions are usually transported in Spiral pattern.. Anterior ethmoid cells drain into the middle meatus.

Posterior ethmoid cells and Sphenoid sinus drain via the superior meatus into the spheno ethmoidal recess.

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Maxillary Sinus Development

- first to develop (10th week)- outpouching of the lateral wall of the ethmoid area within the infundibulum and immediately posterior to the developing uncinate process- enlarges slowly during fetal life-appears as a slit b/w the developing ethmoid cells, the inferior turbinate, and the bone of the maxilla.- nasal capsule is resorbed during its ossification,maxillary sinus enters the developing maxillary process. As the maxillary sinus expandsinto the maxilla, it is restricted by dental development.

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Maxillary Sinus Development

In the neonate, is represented by a small cavity whose lower border lies above that of the nasal floor and is encroached upon by the upper dentition.

However, as the development the face progresses and eruption of the permanent dentition occurs, the floor of the sinus migrates to a lower level than that of the nasal cavity (0.5–10 mm).

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Ethmoid Sinus Development

earliest -fourth fetal month multicentric origin. majority :middle meatus as anterior ethmoid cells

(evaginations in the lateral nasal wall) minority develop from the superior and supreme meatus as

posterior ethmoid cells Other primitive structures called ethmoturbinals , the

uncinate process , the agger nasi , and the ethmoid bulla are medial extensions of the lateral wall of the nasal capsule.

The attachments of these structures to the lateral nasal wall of the nasal capsule are the lamellae.

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The ethmoid sinus is well developed at birth. 2nd yr the air cells may grow beyond the confines of the

ethmoid bone into the surrounding bones: maxilla, frontal, lacrimal, and sphenoid.

The growth pattern of the ethmoid sinus is completely unpredictable, and development will continue until 12years

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Ethmoid cells A. that belong to the ethmoid bone ( conchal, bullar, infundibular,

and frontal recess cells) B. that extend beyond the ethmoid bone : - agger nasi cells (anterior ethmoid cells that pneumatize the agger nasi on the medial surface of the frontal process of

the maxilla and lacrimal bone) - frontal sinus cells (anterior ethmoid cells that pneumatize the frontal bone) - orbital cells (anterior ethmoid cells that pneumatize the orbital

roof), and palatine bone -sphenoid bone cells (posterior ethmoid cells that pneumatize

these bones).

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-The superior meatus is the origin of most of the posterior ethmoid air cells. -some cells may also grow laterally into the junction of the nasal capsule and orbit posterior to the maxillary sinus cleft. Expansion of these cells into the posterior, lateral, and superior aspect of the maxilla is the usual origin of the ethmomaxillarycells (Haller’s cells)

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Frontal Sinus Development

-4th fetal month, after the development of the frontal recess.-Initially, this recess is a pocket found medial to the very cephalic or superior aspect of the uncinate process and expands into the thick nasal capsule mesenchyme.-The fetal frontal recess is found between the uncinate process and the anterior attachment of the middle turbinate.

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frontal Sinus Development

The frontal sinus is described as developing in several ways: 1. by direct extension of the whole frontal recess 2. from the laterally placed anterior ethmoid cells within

frontal recess 3. from the ethmoid infundibular cells 4. from one or more of the anterior group of ethmoid cells

arising in the frontal furrows

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Frontal sinus development A frontal sinus that develops from the ethmoid infundibulum

or the first or second frontal furrows may have its drainage pathway restricted into a nasofrontal duct. The growth of the surrounding anterior ethmoid cells may also encroach on the proximal part of the frontal sinus, compressing it into a nasofrontal duct. The diameter of this duct depends largely on the degree of encroachment by the surrounding ethmoid cells.

does not affect the frontal sinus, which develops directly from the wall of the frontal recess and has a distinct ostium named the primary frontal sinus ostium (the point of origin of the frontal sinus)

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Frontal recess

Tract that leads from the frontal sinus into the nasal cavityEthmoid bulla is the posterior border of the frontal sinus outflow tractMedial border is formed by lat surface of most ant portion of middle turbinateAnteriorly tract is bordered by the uncinate process or the agger nasi cells (frontal anterior ethmoid air cells)Frontal ostium is usually found in the most anterosuperior part of frontal recess.

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Frontal sinus development Secondary pneumatization -6 months and 2 yrs Initially, the secondary pneumatization occurs laterally toward the orbital side of

the frontal bone second year - pneumatization has a more vertical direction. However, by

definition, a frontal sinus is not present until the cell enters the vertical (ascending) portion of

the frontal bone.

the superior extremity - midvertical height of the orbit – 4 years - superior orbital rim at 8 years - frontal squama at 10 years -continues its growth at a slow rate into adolescence The expansion into the vertical frontal bone occurs closer to the cranial cavity, and

consequently the external table of the frontal bone is thicker than the inner table.

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Frontal sinus development

The development may be affected by the expansion of the surrounding anterior ethmoid cells.

one or more of these cells begin pneumatizing the frontal bone and may even exceed the primary frontal sinus outgrowth.

The “true” sinus may encroach on the lumen of the second sinus by forming a bulbous projection (bulla frontalis) in the wall of the latter larger sinus.

The left and the right frontal sinuses develop independently,

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Modified kuhn classification of frontal sinus & frontal recess cells

Agger nasi cells - usually a single cell anterior to middle turbinate Supraorbital cells – region of anterior ethmoidal artery Frontoethmoidal cells : Type I : Single frontal cell above agger nasi cell Type II : Tier of cells in frontal recess above agger nasi cell Type III : Single massive cell pneumatizing cephalad into frontal sinus Type IV : A cell pneumatising through into frontal sinus & extending > 50% of vertical height of frontal sinus Suprabullar cells : a cell / cells above bulla ethmoidalis Frontal bulla cells : a suprabulla cell that pneumatises along skull base into frontal sinus which appears on coronal CT as isolated frontal sinus cell Interfrontal sinus septal cell : a cell a/w frontal sinus septum pushing the sinus

drainage pathway laterally & narrowing the frontal ostium

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Sphenoid Sinus Development

The development of the sphenoid sinus is unique because of two factors:

(1) It is the only sinus that does not arise as an outpouching from the lateral nasal wall

(2) there is no primary pneumatization, but rather a constriction of the developing presphenoid recess followed by secondary pneumatization.

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During the third month of fetal development the nasal mucosa invaginates into the posterior portion of the cartilaginous nasal capsule.

This primordium is only a small presphenoid recess,separated incompletely from the nasal cavity by the development of a nasal mucosal fold, inferiorly based, curving upward and anterior to the body of the presphenoid.

As the nasal capsule undergoes chondrification, a cartilaginous concha forms within this fold, developing cartilaginous concavities, which, by the fifth fetal month, enclose the presphenoid recess.

Site of initial sinus rudiment and of initial constriction is preserved in adulthood as the location of the sinus ostium

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After birth, the sphenoid sinus primordium grows inferiorly and posteriorly.

2 – 3 yrs:the intervening cartilage is resorbed, and part of the sphenoid concha fuses to the presphenoid body;

The presphenoid recess becomes the sphenoethmoid recess. Following this fusion, pneumatization of the sphenoid occurs

8 to 10 years - real sinus cavity may be observed, The origin - always identified by the sinus ostium, located

high on the anterior sinus wall, just a few millimeters below the sphenoethmoid recess.

The shape of the sinus is determined by the varying degrees of pneumatization that take place in the secondary pneumatization.

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Macroscopic Anatomy

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The vestibule is limited above and behind by a curved ridge, the limen nasi

The union of the vestibule with the mucosa of the nasal cavity has the shape of a triangular aperture -nasal valve

- superior and lateral limits - upper lateral cartilage - medial wall - the nasal septum - base -by the floor of the nose.

The nasal valve area marks the junction between the lower limit of the upper lateral cartilage and the upper portion of medial and lateral crura of the lower lateral cartilages.

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boundaries

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Middle turbinate

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Osteomeatal complex

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Uncinate process

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There is frequently a small sulcus on the lateral wall of nose at the insertion of the uncinate process. Posterior to this pt.,the uncinate process can be readily incised.

The safest method however is to identify the uncinate process at its free post. margine.

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SUPRABULLAR RECESS

It is a cleft between roof of ethmoid, ground lamella,and bulla. It has only a surface communication with the middle meatus through hiatus semilunaris and anteriorly with the frontal recess.

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Inferior turbinate

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Ethmoid labyrinth

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Sphenoid sinus

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Frontal sinus

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Sphenoid sinus

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Blood supply

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Nervr supply

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Maxilla bone

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orbit

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Ethmoid bone

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Kero classification?

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Anterior ethmoid artery

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Endoscopic anatomy The opening of the nasolacrimal duct : -anterosuperior part of the inferior meatus~1 cm

behind the anterior end of the inferior turbinate. -slitlike opening, often recognized by a

surrounding crescent of mucosal fold.

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Endoscopic anatomy

First narrow point : Nasal valve area

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Endoscopic anatomy

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First pass: floor of nose

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Second pass : medial to middle turbinate

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Third pass : middle meatus

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Endoscopic anatomy The attachment of the posterior insertion of the middle turbinate (situated in the upper third of the posterior choana

just in front of its anterior edge) forms a landmark for the front wall of the sphenoid sinus

can also be palpated 1 cm above the dome of the choana paramedially.

The location of the sphenoethmoid recess and the sphenoid ostium is higher somewhat more medially and posterosuperiorly to the superior turbinate.

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Endoscopic anatomy The middle turbinate is the most important landmark of the nasal cavity. The anterior attachment extends superiorly to articulate with the cribriform

plate of the ethmoid bone. The middle meatus is the most important region for endoscopic nasal surgery

because it is the normal pathway to the maxillary, ethmoid, and frontal sinuses and also provides surgical exposure to those sinuses.

The endoscopic view shows the uncinate process, part of the ethmoid bulla, and the hiatus semilunaris

The ethmoid infundibulum is usually not visible, and therefore the maxillary ostium cannot be inspected.

The infundibulum may be quite shallow when the uncinate process is in close proximity to the lamina papyracea. Also, in the presence of a concha bullosa and/or paradoxical turbinate, the ethmoid infundibulum may be completely obliterated, resulting in recurrent sinus infections.

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Endoscopic anatomy

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Endoscopic anatomy

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Endoscopic anatomy 1-2 mm infront of agger nasi area lies the nasolacrimal canal.

It runs lateral to the lateral nasal wall and parallel to the agger nasi after descending medially under some ethmoid cells.

The agger nasi, the frontal recess, and the nasolacrimal canal lie in roughly the same frontal plane. This proximity explains why the nasolacrimal canal is in

danger in this area during endoscopic dissection, particularly in massive polyposis with bony erosion of the ethmoid cells.

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Documents

1 Anatomy of Internal Nose & PNS in relation to Endoscopic Surgery Dr Vishav Yadav ENT