health

1. ANATOMY OF PARANASAL
SINUSES
By Dr Kanav Rishi(PGT-1)

2. PARANASAL SINUSES
• Paranasal sinuses, 4 in number, are air
containing cavities in certain bones of
skull.
• Develop as outpouchings from mucous
membrane of lateral wall of nose.
• Lined by ciliated columnar epithelium
with goblet cells which secrete mucus.
• Cilia are more marked near the ostia and
help in drainage of mucus into nasal
cavity.

3. • Divided into 2 groups:
• Anterior:-
- Maxillary sinus
- Frontal sinus
- Anterior ethmoidal sinus
• Posterior:
- Posterior ethmoidal sinus
- Sphenoid sinus

4. Development
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 towards lateral wall of nose.
• Apex towards zygomatic process of
maxilla.
• Approx. 15ml in volume.
• Drains into middle meatus.

6. Relations
• Anteriorly wall - Facial surface of
maxilla, soft tissues of cheek
• Posterior wall - Infratemporal and
pterygopalatine fossa
• Roof - Floor of orbit and is traversed
by infraorbital nerves and vessels.
• Floor - Alveolar and palatine
processes of maxilla, 2nd premolar and
1st molar.

7. • Its Ostium is situated at the superior aspect
of the medial wall.
• The Nasolacrimal duct runs 4-9mm anterior
to the ostium.
• 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

8. Surgical anatomy
• Consistent anatomical landmarks of PNS which
helps during surgery include:
• Maxillary sinus
• Orbit from the maxillary sinus roof / orbital floor
and medial orbital wall(lamina papyracea).
• Skull base identified posteriorly by the sphenoid
sinus.
• These defined anatomical limits establish the
boundaries of the paranasal surgical box including:-
• (a) Horizontal component
• (b) Vertical component

9. • HORIZONTAL COMPONENTS
• Boundaries:-
• Medially - Middle turbinate
• Anteriorly - Medial orbital wall
• Inferiorly - Floor of nose and
• Superiorly - Skull base
• VERTICAL COMPONENTS
• Boundaries:-
• Medially - Middle turbinate
• Laterally - Lamina papyracea
• Anteriorly - Nasofrontal beak
• Posteriorly - Skull base

10. • 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

11. Clinical importance
• Dental caries or infection during tooth
extraction may lead to spread of infection
into the maxillary sinus.
• Infraorbital canal may be dehiscent with
nerve lying submucosally.
• Accessory ostia if neglected during sinus
surgery cause recirculation of mucus into
maxillary sinus.
• Endoscopic Sphenopalatine Artery
Ligation
• Endoscopic Maxillary Artery Ligation

12. 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.
• Begins as frontal recess in 4th month
of IUL.
Frontal sinus

13. •Relations
• 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 into the
frontal recess.
• In sagittal section, the frontal
infundibulum, frontal ostium and the
frontal recess form “hour-glass
configuration”

14. • 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 - 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

15. Frontal recess
• BOUNDARIES:-
• Anteriorly:- Agger nasi and the
frontal process of the maxilla, the
frontal beak.
• Medially:- Middle turbinate, the
lateral lamella of the cribriform plate
• Lateral:- Lamina papyracea
• Posterior:- Upward continuation of
the anterior face of the bulla.

16. • The uncinate process inserts onto the
medial orbital wall in 85% of cases.
• Thus, the frontal recess drainage
pathway is medial to the uncinate
process in 85% of cases.
• An uncinate process with an isolated
attachment to either the skull base or
middle turbinate occurs in only 15%
of cases.
• Frontal drainage pathway located
lateral to the uncinate process

17. Clinical importance
• Acute rhinosinusitis (ARS):- Sudden, follows
an URTI.
• Chronic rhinosinusitis:- obstruct the frontal
sinus outflow tract and lead to frontal
pressure or headache.
• ABRS:- Pott’s puffy tumour - Subperiosteal
abscess of frontal sinus leads to headache,
swelling and discharging frontal fistula.
• Frontal sinus surgery:- The Agger nasi cell is
key to all approaches to the frontal recess.
• Balloon sinuplasty:- The technique
introduces a balloon over a guide wire, in
the sinus to unblock it.

18. • Osteomas:- slow growing tumours occur
most often in the ethmoid followed by
the frontal sinuses.(Gardner’s syndrome-
multiple osteomas, colorectal polyps,
skeletal abnormalities and supernumerary
teeth)
• Inverted papilloma:- After osteoma, the
most frequent benign tumor of the frontal
sinus.
• Frontal pneumosinus dilatans:- An
abnormally large aerated sinus.
• Mucocele- Most common sinus involved
is Frontal sinus.

19. 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
• concha bullosa
• Pneumatisation may
occasionally extend beyond
ethmoid bone

20. • Clinically, ethmoidal cells are
divided by the basal lamella
attachment into:-
• Anterior ethmoid group
• Posterior ethmoid group
• BOUNDARIES:
• Roof - fovea ethmoidalis
• Medially - cribriform plate
• Laterally - Lamina papyracea

21. PNEUMATIZATION PATHS OF ETHMOID AIR CELLS

22. The anterior and posterior ethmoid air
cells may pneumatize surrounding bones
like the lacrimal bone, maxilla, frontal
bone and sphenoid to produce varying
patterns of pneumatization.
PNEUMATIZATION PATHS OF ETHMOID AIR CELLS

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

24. • Supraorbital cells
• Frontoethmoidal cells:-
• Situated- frontal recess, Encroach- the
frontal sinus
• Invasion of ethmoid cell in 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.

25. • POSTERIOR GROUP
• Lies posterior to the basal lamina.
• 1-7 in number.
• Open- superior meatus
• Onodi cell:-
• Posterior most cell
• Supero-lateral to sphenoid sinus
• Optic nerve and carotid artery is
related to it laterally and there’s
risk of injury during FESS.

26. • Bulla Ethmoidalis:-
• Separated posteriorly from ground
lamella by - retrobullar recess.
• Separated from the base of the skull
by -suprabullar recess
• These together form a semilunar
space above and behind the bulla-
sinus lateralis of Grunwald
• This sinus opens into the middle
meatus by a semilunar cleft- hiatus
semilunaris superioris.

27. Olfactory fossa
• Formed by the horizontal lamella of
the cribriform plate, its vertical
lamellae and a part of the orbital plate
of the frontal bone.
• The vertical lamella is thinnest where
the anterior ethmoidal artery
perforates it.
• The depth of the olfactory fossa varies
and has been classified by Keros into:-

28. Kero’s classification
• 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 surgery

29. • ARTERY SUPPLY
• Anterior ethmoidal artery
• Posterior ethmoidal artery
• Sphenoid artery
• VENOUS DRAINAGE
• Anterior ethmoidal vein
• Posterior ethmoidal vein

30. • NERVE SUPPLY
• Anterior ethmoidal nerve
• Posterior ethmoidal nerve
• Orbital branch of pterygopalatine
ganglion

31. Clinical importance
• Acute rhinosinusitis:- Ethmoid sinus is the most common location.
• Tumours:- Usually Adenocarcinomas. Most SCC of the sinonasal tract arises from
the nasal cavity and ethmoid sinuses.
• Aggressive psammomatoid ossifying fibroma (APOF) or juvenile-aggressive OF :-
Most commonly affect the ethmoid sinus.
• Fibrous dysplasia or Osteoma:- Causing secondary obstruction of drainage
pathways, or mucocele of the sphenoid sinus.

32. • Allergic fungal sinusitis with the ethmoid sinuses with expansion of
the sinus causing lamina papyracea remodelling.
• Transcribriform Unilateral Access- The bone of the roof of the
ethmoid sinus is removed to completely expose the dura.

33. Osteomeatal unit
• Anteriorly the uncinate process.
• Behind this is the ethmoidal bulla.
• These structures are separated by a
semilunar groove called the hiatus
semilunaris.
• The hiatus semilunaris leads into
the infundibulum.
• The uncinate process, bulla and
infundibulum form the key area or
the osteomeatal unit into which
the frontal, the maxillary and
anterior ethmoidal sinuses drain.

34. Boundaries
• Anterior: Agger nasi, atrium of middle
meatus
• Superior: Basal lamella
• Posterior: Middle turbinate
• Floor: Inferior concha
• Medial: Middle concha
• Lateral: Lamina papyracea of the
ethmoid sinuses

35. 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
obliquely placed.
• Its ostium - opens into the
sphenoethmoidal recess.
• In some cases pneumatisation may
extend into greater or lesser wing of
sphenoid, pterygoid or clivus.

36. • RELATIONS:
• ANTERIOR PART :-
• Roof - Olfactory tract, optic chiasma
and frontal lobe.
• Laterally - Optic nerve, internal
carotid artery, Maxillary nerve
• POSTERIOR PART :-
• Roof - Pituitary gland
• Laterally - Cavernous sinus, ICA, CN
3,4,5,6
• Floor - Vidian nerve
• This carotico-optic recess is extremely
deep when ant clenoid process is
pnuematised & optic nerve is
dehiscent in such cases.

37. • 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

38. Pneumatization
• Position of sinus depend on
extent of pnuematization
• 3 types:
• Conchal -Small pit in a
predominantly non
pneumatized sphenoid bone
• Pre-sellar -Extending up to ant
wall of sella turcica
• Sellar -MOST COMMON
• Mixed

39. Clinical importance
• Pituitary fossa is present anterior and
inferior to Sphenoid sinus and Intra-
sphenoid sinus septum.
• Visual pathway:- Optic nerves may be
dehiscent of bone as they traverse the
lateral wall of the sphenoid sinuses.
• Removing all bony septations within the
sphenoid sinus maximizes horizontal
exposure, thus, providing access from
lateral wall to lateral wall with clear
visualization of the lateral optico-carotid
recesses.

40. • FRS:-The ethmoid and sphenoid sinuses
are most commonly involved.
• Optic neuropathy is due to direct
compression of the optic nerve in the
posterior ethmoid and sphenoid sinuses.
• Mucoceles- No attempt is made to
remove the lateral sphenoid sinus
mucosa as bony erosion place the
internal carotid artery or optic nerve at
risk of injury.

41. • Juvenile angiofibroma:- Sphenoid
sinus floor are common hallmarks of
JAs. Bony destruction of the sinus
floor is followed by tumour
extension into the sinus.
• Epicenter of endonasal skull base
approaches since it is often the
starting point for endoscopic skull
base experience.

42. THANK YOU