ANATOMY OF PARANASAL SINUSES

1. ANATOMY OF PARANASAL
SINUSES
BY DR V RACHIT

2. INTRODUCTION
• Paranasal sinuses are air containing cavities in certain bones of skull
• They are 4 on each side
• Develop as outpouchings from mucous membrane of lateral wall of
nose
• Lined by mucous membrane which is continuous with that of nasal
cavity through the ostia of sinuses
• Lined by ciliated columnar epithelium with goblet cells which secrete
mucus
• Cilia are more marked near the ostia of sinuses and help in drainage
of mucus into nasal cavity

3. • Paranasal sinuses can be divided
into 2 groups
1) Anterior - Open into the middle
meatus and their ostia lie
anterior to the basal lamella of
middle turbinate
Includes
- Maxillary sinus
- Frontal sinus
- Anterior ethmoidal sinus
2) Posterior -
Includes
- Posterior ethmoidal sinus -
Opens into the superior meatus
- Sphenoid sinus - Opens in
sphenoethmoidal recess

4. SINUS STATUS AT BIRTH FIRST RADIOLOGICAL
EVIDENCE
MAXILLARY PRESENT AT BIRTH
4- 5 MONTHS AFTER
BIRTH
ETHMOID PRESENT AT BIRTH 1 YEAR
FRONTAL NOT PRESENT AT BIRTH 6 YEARS
SPHENOID
NOT PRESENT AT BIRTH
4 YEARS

5. MAXILLARY SINUS
• Largest paranasal sinus
• Pyramidal in shape
• Base directed towards lateral wall of
nose
• Apex towards zygomatic process of
maxilla and sometimes zygomatic
bone itself
• 33mm high, 35mm deep and 25mm
wide
• 15ml in volume
• Drains into middle meatus

6. RELATIONS
Anteriorly wall - Facial surface of maxilla
and is related to soft tissues of cheek
Posterior wall - Infratemporal and
pterygopalatine fossa
Roof - Floor of orbit and is traversed by
infraorbital nerves and vessels which
travel through infraorbital foramen
Floor - Alveolar and palatine processes of
maxilla .Usually related to 2nd premolar
and 1st molar
Oroantral fistula can result from
extraction of any of these teeth

7. • Ostium of the maxillary sinus is situated at the superior aspect of the medial
wall of the sinus
• The Nasolacrimal duct runs 4-9mm anterior to the ostium
• Anterior to maxillary ostium is frontonasal process with a groove immediately
behind this which along with lacrimal bone and lacrimal process of inf
turbinate forms canal for NLD
• Posterior to ostium is maxillary tuberosity which contributes to canal for
greater palatine nerves and vessels
• Fontanelles - Areas of bony dehiscence usually covered by mucosa present in
the medial wall of maxillary sinus
Posterior fontanelle is patent in about 30% of cases and is called accessory
ostium
• Arterial supply - Infraorbital A and Greater Palatine A br of Int maxillary A
• Venous drainage - Through pterygoid plexus and facial vein
• Lymphatic drainage - Submandibular lymph nodes
• Nerve supply - Infraorbital, Greater palatine and Superior alveolar nerves

9. CLINICAL IMPORTANCE
• Extensively pnuematized maxillary sinus may encroach upon alveolar
process of maxilla
• Dental caries or infection during tooth extraction may lead to spread
of infection itno the maxillary sinus as it is related to the floor of the
sinus
• Infraorbital canal may be dehiscent with nerve lying submucosally
• Acessory ostia if neglected during sinus surgery cause recirculation of
mucus into maxillary sinus
• Normal ostium is widened in anteroinferior direction to prevent
injury to nasolacrimal duct

10. FRONTAL SINUS
• Situated between inner and outer
tables of frontal bone, above and
deep to supraorbital margin
• Asymmetric and loculated by
incomplete septa
• Two sinuses separated by thin bony
septum which sometimes may be
absent
• About 32mm in height, 24mm
breadth and 16mm deep
• Begins as frontal recess in 4th
month of IUL

11. Boundaries
Anteriorly - Related to skin over forehead
Posteriorly - Related to meninges and
frontal lobe of brain
Inferiorly - Orbit and its contents
• Drainage of the sinus is through frontal
ostium into the frontal recess
• The infundibulum leads directly or
indirectly into the frontal recess
• the anterior wall of the frontal recess is
formed by the anterior wall of the agger
nasi cell
• The posterior wall is formed by the bulla
ethmoidalis

12. • The medial wall is formed by the middle turbinate
• The lateral wall of the frontal recess is formed by the
lamina papyracea
• In sagittal section, the frontal infundibulum, frontal
ostium and the frontal recess together form the “hour-
glass configuration
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

14. ETHMOIDAL SINUS
• Most variable(3-18 cells on each side) and
develop from pneumatisation of ethmoid
bone
• They occupy the space between upper
third of lateral nasal wall medial wall of
orbit
• When pneumatisation of ethmoid extends
into middle turbinate - concha bullosa
• Pneumatisation may occasionally extend
beyond ethmoid bone
a) Orbit bone - supraorbital cell
b) Roof of maxillary sinus - Haller cell
c) Floor of frontal sinus - Frontoethmoidal
cell
d) Superolat to sphenoid sinus - Onodi cell

15. • Clinically,ethmoidal cells are divided by
the basal lamella attachment into
- anterior ethmoid group which opens
into the middle meatus
- posterior ethmoid group which opens
into the superior meatus and
sphenoethmoidal recess
• BOUNDARIES
Roof - fovea ethmoidalis(depressions on
undersurface of orbital plate of frontal
bone)
Medially - cribriform plate
Laterally - Lamina papyracea

16. ANTERIOR GROUP
1. Agger nasi cell
-Present in agger nasi ridge
-Ant most ant ethmoidal air cells
-1st prominent landmark encountered in
FESS
-Located ant-superior to insertion of
middle turbinate
2. Haller cells(Infraorbital cells)
-Situated in the floor of orbit
-Adhere to roof of maxillary sinus forming
lat wall of infundibulum
-Enlargement of this sinus can impede the
maxillary sinus drainage

17. Keros classification
• Length of lateral lamella and
depth of olfactory fossa are
classified by Keros.
• TYPE 1 : 1-3mm
• TYPE 2 : 4-7mm
• TYPE 3 : 8-17mm
• More the length of the lamella,
more is the chance of the injury
during FESS

18. 3.Bulla Ethmoidalis
-The ethmoidal bulla is usually a well
pneumatized, most constant, anterior ethmoidal
cell
-It is separated posteriorly from the ground
lamella of the middle turbinate by a recess called
the retrobullar recess
-Occasionally 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
-This sinus opens into the middle meatus by a
semilunar cleft called hiatus semilunaris
superioris. Thus the hiatus semilunaris inferioris
leads into the infundibulum and the hiatus
semilunaris superioris leads into the sinus
lateralis of Grunwald

20. 4. Supraorbital cells
5. Frontoethmoidal cells
- Situated in frontal recess and encroach into the frontal sinus
- Invasion of ethmoid cell into floor of frontal sinus - FRONTAL BULLA
- Since this bulla is close to frontal recess ,it can impede ventilation and drainage of
frontal sinus
- Commonly involved in frontal mucocele
POSTERIOR GROUP
• Lies posterior to the basal lamina
• 1-7 in number
• Open into superior meatus
• Onodi cell
- Posterior most cell
- Superolateral to sphenoid sinus
- Optic nerve and sometimes carotid artery is related to it laterally and theres risk of
injury during FESS

21. • The anterior ethmoidal artery is an anatomical
landmark; its location is important for
recognizing structuresof difficult access
(frontal sinus)
• The anterior ethmoidal artery exits the orbit
through lamina papyracea
• Later it courses horizontally across the roof of
ethmoid sinus in a thin bony mesentry
• It then enters the cribriform plate anterior
crania cavity via fovea ethmoidalis
• It also penetrates the anterior most aspect of
cribriform plate to enter nasal cavity and
supply nasal septum and anterosuperior nasal
cavity
BLOOD SUPPLY- Anterior and posterior
ethmoidal A br of ophthalmic A and
Sphenopalatine A br of Maxillary A
NERVE SUPPLY - Supraorbital nerve, anterior
ethmoidal and branches from pterygopalatine
ganglion

22. SPHENOID SINUS
• Deepest of the paranasal sinuses
• Occupies body of sphenoid bone
• 2 in number, one on each side
• Separated often asymmetrically by a thin
bony septum which is often obliwuely
placed
• The sphenoid sinus ostium is situated high
up in the anterior wall and opens into the
sphenoethmoidal recess
• In some cases pneumatisation may extend
itno greater or lesser wing of sphenoid,
pterygoid or clivus

24. Pnuematisation
• Position of sinus depend on extend of pnuematization
• 3 types:
• conchal [only a rudementry sinus]
• presellar( extending up to ant wall in pitutary fossa )
• Sellar ( extent back beneath pit.fossa) MOST COMMON
• mixed

25. BOUNDARIES
Laterally - Optic nerve and carotid artery
with carotico-optic recess in between.
Maxillary nerve to the lower part of
lateral wall
Floor - Vidian nerve
Roof - Anteriorly, related to olfactory
tract, optic chiasma and frontal.
Posteriorly, related to the pituitary gland
Laterally - Cavernous sinus
Posteriorly - Clivus
This carotico-optic recess is extremely
deep when ant clenoid process is
pnuematised & optic nerve is dehescent
in such cases

26. ARTERIAL SUPPLY
Sphenopalatine A - Entire sinus except
roof
Posterior ethmoidal A - Roof
VENOUS DRAINAGE
Via Maxillary veins into the jugular
and pterygoid plexus system
NERVE SUPPLY
Nasociliary nerve - Roof
Branches of sphenopalatine nerve -
Remaining sinus

27. Drainage of sinuses
The bulla may drain into the middle
meatus or the hiatus semilunaris
inferioris
• The frontal sinus drains into the
frontal recess and suprabullar recess
if present
• The maxillary sinus always drains into
the infundibulum
• The sphenoid sinus drains into the
sphenoethmoidal recess

28. ENDOSCOPIC ANATOMY
• In the 2nd pass when the scope is moved along
the roof of the posterior choana, the
sphenoethmoidal recess is visualised
• The recess lies between the superior turbinate
laterally and the septum medially
• It is bounded above by the base of the skull
and is continuous inferiorly with the posterior
part of the nasal cavity
• The sphenoid ostium opens into the
sphenoethmoidal recess 1-1.5 cm above the
roof of the posterior choana and a few mms
away fron the septum
• Below the ostium at the roof of the posterior
choana is a mesh of blood vessels, which form
the Woodruff’s plexus

29. • Accessory ostia may be seen in the
region of the anterior fontanelle, i.e.
anteroinferior to the anterior end of the
uncinate process, or in the posterior
fontanelle i.e. above and behind the
posterior end of the uncinate process
• On cutting the uncinate process ,
infundibulum is exposed and the
maxillary ostium can be seen lying in an
oblique or horizontal plane behind the
intermediate attachment of the uncinate
process
• On widening the maxillary ostium , floor
of orbit and infraorbital N can be
visualised

30. • On removing the upper border of
attachment of uncinate process, along
with along with any cells present in the
frontal recess, frontal sinus is exposed
• On reflecting the bulla laterally upto
the lamina papyracea and superiorly
upto the skull base, anterior ethmoidal
artery is seen running obliquely around
skull base
• After removing the uncinate process,
ground lamella is visualised which is
perforated posteroinferiorly to enter
posterior ethmoidal cells
• The posterior ethmoidal cells are
divided from the sphenoid sinus by an
imaginary ridge

31. THANK YOU