Surgical anatomy of nose

DR. PRATHYUSHA PG ENTNARAYANA MEDICAL COLLEGENELLORE

Introduction

embryology

External anatomy

Nasal septum

Lateral wall of nose

Applied anatomy

DEVELOPMENT OF NOSE

The developmental precursors of the nose are the

neural crest cells,

which commence their caudal migration toward the midface around the fourth week of

gestation.

Five facial prominences

1. FRONTONASAL prominence 2. MAXILLARY prominence 3. MEDIAL NASAL prominence 4. LATERAL NASAL prominence 5. MANDIBULAR prominence

Appearance of nasal placodes at the end of 4th week of IUL

NASAL PITS are formed on 5th week of IUL, by invagination of nasal placodes.

Nasal prominence are formed following the formation of Basal pits

NASAL PROMINENCE divided into 2 subdivisions:

1. LATERAL nasal prominence

2. MEDIAL nasal prominence

Medial nasal process

Philtrum

Medial crus of lower lateral cartilage

Lateral nasal process

Upper nasal bones

Upper nasal lateral cartilages

Lateral crus of lower lateral cartilages

Nasal Septum Development

embryo stage (6th week)

Fusion of maxillary to frontonasal process.

Midline ridge from posterior end of frontonasal process forms septum

Development of lateral wall of nose

During 8th week of IUL 6 to 7 ridges appear on the lateral nasal wall,

those ridges are called as ETHMO TURBINALS.

ETHMO TURBINAL 1. ASCENDING portion forms AGGER NASI 2. DESCENDING portion forms UNCINATE

PROCESS

2nd ETHAMO TURBINAL forms MIDDLE TURBINATE.

3rd ETHAMO TURBINAL forms SUPERIOR TURBINATE

4th and 5th ETHAMO TURBINAL forms SUPREME TURBINATE

MAXILLO TURBINAL forms INFERIOR TURBINATE

FURROWS between each ETHAMO TURBINALS forms respective NASAL MEATUSES

1st FURROW :- MIDDLE MEATUS (b/w 1st & 2nd ET)

2nd FURROW :- SUPERIOR MEATUS

3rd FURROW :- SUPREME MEATUS

4th FURROW :- INFERIOR MEATUS

External nose Upper portion

1. nasal bones

2. perpendicular plate of ethmoid

3. frontal process of the maxillary bone

Middle portion:

1. upper lateral cartilages

2. dorsal portion of quadrangular cartilage

Lower portion

1. bilobed alar cartilages (nasal tip detereminant)

2. accessory cartilages

3. fibrofatty tissue

External anatomy

Integrity of the external nose

Keystone area

area overlapped by nasal bones over upper lateral cartilages

Junction of septal cartilage, perpendicular plate of ethmoid, and nasal bone

Critical in the support of the nasal dorsum.

Aponeurotic attachment of upper lateral cartilages to frontal process of the maxilla

Interdomal ligament the lower alar cartilages make it a single unit

Keystone area Fibrous tissue

Nasal bone

Note it is thicker superiorly and tapers inferiorly

Key points on external nose

Nasal bone is thick superiorly and thin below intercanthal line (fracture vulnerability)

Pole and tent relationship between ethmoid and the nasal bones makes ethmoid bone fracture vulnerable

Nasal cartilages absorb significant amount of force.

Avulsion and dislocation of upper lateral cartilages give

“ hollowed out” appearance

External nasal artery a terminal branch of ophthalmic artery exits between nasal bone and upper lateral cartilage is

prone for injury

nasal septum

Columellar septum : formed by medial crura of alar cartilages

Membranous septum : devoid of bone or cartilaginous support

Septum proper

Ethmoid bone

Needs to be understood in a proper way

Forms most of the skeletal framework of the nose

Ethmoid bone

Single delicate bone with horizontal cribriform plate and vertical perpendicular plate of ethmoid

Cribriform plate fits into notch of the frontal bone

It transmits olfactory nerves as well as anterior and

posterior ethmoidal arteries

Crista galli is a projection on cribriform plate

Inferior turbinate Septal view orange is lacrimal process blue ethmoidal process

Inferior turbinate meatal view green is maxillary process

Vomer bone

Blood supply of nasal septum

Woodruffs plexus

anterior and posterior ethmoidal arteries are branches of ophthalmic artery ( ICA )

Sphenopalatine artery, greater palatine artery are branches of maxillary artery ( ECA )

Superior labial artery is a branch of facial artery (ECA)

Important anatomical concepts

the perpendicular plate of ethmoid should NOT be rocked as it may lead to the fracture of cribriform plate and cause CSF leak.

Lateral wall of nose Very important to be anatomically oriented

With the invent of endoscopy landmarks need to

be well versed

Makes radiological interpretation very easy

Lateral wall will be dissected layer by layer to get

familiar with anatomical details

3D view of lateral nasal wall

Lateral nasal wall

Anterior part is covered by skin and has hair (vestibule)

Bulge anterior to the middle turbinate is the agger nasi cell (most anterior ethmoidal cell)

Ridge from agger nasi cells extend to the superior border of

the inferior turbinate ( naso lacrimal duct)

Most anteriorly is a curved ridge called the uncinate process.

Behind this is the well pneumatized and most constant anterior ethmoidal cell, namely the ethmoidal bulla.

These structures are separated by a semilunar groove called the hiatus semilunaris.

The hiatus semilunaris is two-dimensional and leads into a three-dimensional space called the infundibulum.

The uncinate process, the bulla and the intervening infundibulum form the key area or

the osteomeatal unit into which the frontal, the maxillary and anterior ethmoidal sinuses drain.

Osteomeatal unit

Minimal inflammation in the osteomeatal area can block off aeration to the anterior ethmoid,

frontal

maxillary sinus, leading to infection in them.

This concept is the basis of Messerklinger’s functional endoscopic sinus surgery whereby

the clearance of this area alone may reverse changes in the draining sinuses.

applied anatomy Middle turbinate should be manipulated very gently as it attaches directly to the cribriform plate.

A forcible attempt to medialize the middle turbinate in order to get a better view of the middle meatus may lead to a break in the cribriform plate and a CSF leak

While dissecting in the region of the frontal recess, care should be taken to maintain the mucosa over the middle turbinate.

adhesions will form between the lateral nasal wall and the upper attachment of the middle turbinate These adhesions will cause lateralization of the middle turbinate and obliteration of the frontal recess with subsequent iatrogenic frontal sinus disease In extreme cases complete obliteration of the middle meatus may occur.

Middle turbinate excised

The uncinate process is sickle shaped, with vertical and a horizontal limb

The ethmoidal bulla is usually a well pneumatized,

most constant, anterior ethmoidal cell.

Can be absent in 8% of cases

Ethmoidal bulla separated posteriorly from the ground lamella of the middle turbinate by a recess called the retrobullar recess

the bulla does not extend upto the base of the skull and is separated from it by the suprabullar recess. The retrobullar and suprabullar recesses together form a semilunar space above and behind the bulla called the

sinus lateralis of Grunwald.

Ethmoidal bulla orientation

applied anatomy Clearance of the bulla, anterior and posterior ethmoid cells should be done using blunt

instrument to prevent injury to the lamina papyracea and orbital contents.

The anterior wall of the bulla lies just in front of the

anterior ethmoidal artery at the base skull

Frontal recess Lot of anatomical variations

bounded anteriorly by the agger nasi cell .

The posterior wall is formed by the bulla ethmoidalis.

The lateral wall is formed by the lamina papyracea.

The medial wall is formed by the middle turbinate.

Superiorly the frontal recess opens via the frontal ostium into the frontal sinus.

Hour glass configuration of frontal recess

Frontal recess

Applied anatomy

Whilst dissecting in the frontal recess the surgeon

may think he has entered the frontal sinus, when

in fact, he is within a frontal cell (anterior ethmoidal cell )

It is necessary to de-roof this frontal cell so as to

reach the frontal sinus and establish its drainage

Reflected uncinate process

Applied anatomy

A branch of the sphenopalatine artery runs along the lateral nasal wall in the middle meatus.

This branch may be encountered whilst widening the maxillary ostium posteriorly

The normal ostium should be widened in an anteroinferior direction to prevent injury to the nasolacrimal duct, which lies 5 mm anterior to it.

The sphenoid sinus ostium lies high on its anterior wall close to its roof.

It drains into the sphenoethmoidal recess.

The superior turbinate in the sphenoethmoidal recess, may over lie the opening of the sphenoid ostium.

The sphenoid ostium lies 1-1.5 cm above the roof of the

posterior choana and approximately 2-3 mm away from the septum.

Ethmoidal sinus The anterior ethmoidal air cells are variable in number; the posterior ethmoidal air cells are fewer and larger.

Anterior group drains into middle meatus by way of the infundibulum

Middle group drains into the middle meatus

Posterior group drains into superior meatus and some times one or more into sphenoidal sinus

The anterior ethmoidal cells may migrate anterosuperiorly into the frontal recess to produce different types of frontal cells

Type I A single cell above the agger nasi cell

Type II Two or more cells above the agger nasi cell.

Type III A large cell extending well into the frontal sinus mimicking the frontal sinus itself (frontal bulla).

Type IV An isolated “loner cell” separately within the frontal sinus

Anterior ethmoidal cell migrating into frontal recess

posterior ethmoidal cell may extend posterolaterally over the sphenoid called the Onodi

cell.

Thus the Onodi cell insinuates itself between the optic nerve and the sphenoid sinus.

The optic nerve therefore produces a bulge in the Onodi

cell instead of in the sphenoid sinus.

Posterior ethmoidal cell ( onodi cell )

Sphenoidal surgery In approximately 6 percent of cases, the bone over the

optic nerve may be dehiscent

in approximately 25 percent of cases, bone over the internal carotid artery may be clinically dehiscent.

This may be difficult to visualize on CT scan if the sphenoid sinus is full of polyps.

Therefore extreme caution has to be exercised in pulling polyps out from within the sphenoid sinus.

A branch of the sphenopalatine artery runs across the anterior face of the sphenoid to reach the septum may be injured during widening the ostium.

Removed anterior and posterior ethmoidal cell

4 lamellae encountered on endoscopy

These from anterior to posterior are—

the uncinate process,

the anterior wall of the bulla,

the ground lamella

the anterior wall of the sphenoid.

Complete removal anterior and posterior ethmoidal cells

The ethmoidal cells have been completely cleared to expose the lamina papyracea, which appears yellowish due to the underlying orbital fat

The maxillary ostium has been widened to gain a view of the interior of the sinus.

the lamina papyracea and the orbit is just 2-3 mm above the level of the maxillary ostium.

Nasolacrimal duct is split with sac and opening

The nasolacrimal duct opens in the roof of the inferior meatus at this apex.

It is guarded by a valve called the Hasner’s valve.

The canal for the nasolacrimal duct has been dissected. It lies approximately 5 mm anterior

to the normal maxillary ostium.

Lamina papyracea removed

The lamina papyracea has been removed and the orbital periosteum has been cut to expose the orbital

fat.

Anteriorly, a pad of fat separates the vital structures of

the orbit from the nose.

posteriorly the medial rectus is in close relation with the

lamina papyracea

Medial rectus reflected

Blood supply of lateral wall of nose

Take home message With the incorporation of FESS into ENT speciality ( thanks to Dr. Messerklinger ) the anatomical orientation is very important.

The osteocartilagenous framework acts as a single unit and needs to be respected while performing surgery.

Concept of osteomealtal unit could be understood only when the sinus anatomy and their drainage are well versed.

And…. The nose spoke to the children……

Patch Adams ( 1998 )