PG

1. Anatomy of the Paranasal
sinus
Presenter:
Dr Raju kafle
1st year resident
ORL-HNS dept 1

2. Paranasal Sinus : Introduction
• Air filled sacs found in the skull bones.
• Includes Frontal ,Maxillary, Ethmoidal and Sphenoid sinuses.
Function of PNS
1. Air conditioniong, humidification and warming
2. Resonance of voice
3. Thermal insulators to delicate structures in orbit and
cranium
4. Lighten skull bones
5. Extended surface for olfaction
6. Local immunologic defense against microbes
7. Buffer against trauma thus protects brain against injury
2

3. PNS BONES AND DEVELOPMENT
3

4. Frontal bone
4
• Develops from 2 center ( 8th week)
• Centre : superciliary ridges
• At birth : 2 halves separated by frontal or metopic
suture
• Development completes by 2 yrs
Parts :
1. Squama: vertical and convex fwd, outer/
temporal surface and inner/cerebral surface)
2. Orbital : horizontal thin plate projecting
backwards, orbital surface
3. Nasal : directed forward and downwards.

5. 5
Orbital part/plates : separated from each
other by wide gap( Ethmoid notch)
• Lacrymal fossa anterolaterally
• Trochlear spine and fossa
anteromedially.
• Ethmoid notch is occupied with cribriform
plate of ethmoid bone
• On each side of notch: small air spaces that
articulates with labyrinth of ethmoid bone
to complete ethmoidal air sinuses.
Nasal part: lies b/w 2 supraorbital margin,
articulates with nasal , frontal process of
maxilla and lacrimal bones

6. Ethmoid bone
Greek- sieve like , very light cuboidal bone situated
in anterior of base of cranial cavity between two
orbits.
Comprises of
1. Cribriform plate
2. Perpendicular plate
3. A pair of labyrinth
• Ossifies in cartilageneous nasal capsule from 3
centres( 5th IUL)
• Each labyrinth:: each centre
• Last one for perpendicular plate of ethmoid
• Perpendicular plate and cristae galli developed
from the same centre during 1st year of life and
fuses with labyrinth during 2nd year .
6

7. Cribriform plate:
• horizontal perforated bony lamina , occupying ethmoidal
notch of frontal bone
• Contains foramena for olfactory nerve rootlets
Cristae galli
• Median tooth like projection in floor of anterior cranial
fossa
• Side of cristea galli : foramen transmitting anterior
ethmoidal nerve to nasal cavity
Perpendicular plate:
• Thin lamina projecting downwards from undersurface of
cribriform plate forming the upper part of nasal septum.
Labyrinth :
• 2 light cubical mass on each side of perpendicular plate ,
suspended from under surface of cribrform plate
• Encloses a large no of air cells arranged in groups(
anterior , middle and posterior )
7

8. • Articulation of perpendicular plate
• Articulation of labyrinth
• Anterior: frontal process of maxilla
• Posterior : sphenoidal conchae
• Superior : orbital plate of ethmoid
• Inferior : nasal surface of maxilla
• Lateral: medial wall of orbit
• Medial :superior nasal conchae,
middle meatus , superior meatus
8

9. Maxillary bone
• 2nd largest facial bone, forming majority of roof
of mouth , lateral wall and floor of nasal cavity
and floor of orbit
• Body and four process ( frontal , zygmotic ,
alveolar and palatine process)
• Maxilla develops from 5 ossification centres( 6th
week of IUL)
• Ossification centre in medial floor of pyriform
aperture forms the premaxilla.
• Premaxilla gives rises to upper incisors and
lower nasal spine.
9

10. Body of maxilla
• Base directed medially at the nasal surface
and apex to the zygomatic process.
Four surfaces:
• Anterior/ facial
• Posterior / infratemporal
• Superior /orbital
• Medial or nasal surface
Ant surface
• Canine fossa : lateral to canine eminence.
• Infraorbital foramen: above the canine
fossa, transmits infraorbital nerve and
vessels.
10

11. 11
• Medially: anterior surface is more concave ( nasal
notch)
• Corresponding process of opposite maxilla
forms anterior nasal spine.
• Posterior surface: forms anterior wall of
infratemporal fossa.
• Centre : posterior superior alveolar nerve and
vessels.
• Above maxillary tuberosities forms anterior wall of
pterygopalatine fossa and curved by maxillary
nerve.

12. • Medial surface: forms the lateral wall of nose
• Posterosuperiorly : large irregular opening :
maxillary hiatus/Ostium
Above hiatus : parts of air sinus, completed by
ethmoid and lacrymal bones
Below hiatus: smooth concave surface, forming a
part of inferior meatus of nose.
Behind hiatus : Articulates with perpendicular
plate of palatine bone
• Encloses Greater palatine canal
Front of hiatus : nasolacrimal groove
12

13. Sphenoid bone
• Resembles bat with outstretched wings
• Develops from presphenoidal and post
sphenoidal portions.
• These portions fuses during 8th IUM
• Central portions: Body and lesser wings
• Lateral portions: Greater wing and pterygoid
process.
• Pre-sphenoid portion: 6 ossification centres
• Continues with lesser wings of sphenoid
• Post-sphenoid portion: 8 ossification centres
• Gives rise to greater wings and
pterygoid process
13

14. • Body in the centre
• 2 lesser wings from anteriosuperior
part
• 2 greater wing from lateral part of
body
• 2 pterygoid processes, directed
downward from the junction of the
body and greater wings.
• Divides inferiorly into medial and
lateral pterygoid plate.
14

15. Greater wings
3 surfaces( superior, lateral and orbital)
Superior/ cerebral surface: Forms floor of
middle cranial fossa and presents from before
backward as:
• Foramne rotundum
• Foramane ovale
• Emissary sphenoidal foramen
• Foramen spinosum
15

16. Embryology of PNS
16

17. • Paranasal sinuses form developmentally through excavation of bone by air-filled
sacs (pneumatic diverticula) from the nasal cavity
• This process begins prenatally (intrauterine life), and it continues through the
course of an organism's lifetime.
• Frontal , maxillary and etmoidal sinuses arises from evagination of lateral wall of nasal
capsule
• Sphenoid sinus arises from posterior evagination of nasal capsule
• At birth: only ethmoid and maxillary sinus are developed.
• Sphenoid() and frontal( )
17

18. Maxillary sinus
• First to appear( 7-10 weeks),
• First radiological evidence 4-5 months of age
• It develops from primitive ethmoidal infundibulum in the mass of maxilla
• Enlarges by absorption and expansion results in cavity at birth( 7*4*4mm)
• Annual rate of 2mm vertically and 3mm/year anteroposteriorly
• At birth: lower border 4mm above nasal floor
• Rapid growth upto 3years then slowly upto 7 years
• 8-9 yrs of age: lower border equals floor of nose
• Adult size: 0.5 to 10mm below nasal floor
• Relatively large in old age as result of reabsorption of alveolus 2” to loss of teeth.
18

19. • Any disruption or abnomality in development :
maxillary sinus aplasia, or hypoplasia. Present
upto 10% of CT-scan
Radiographic diagnostic criteria:
• Enlargement of vertical orbit
• Lateral position of infraorbital neurovascular
canal
• Elevated canine fossa
• Enlargement of superior orbital fissure
• Enlargement of pterygopalatine fissure
19

20. Frontal sinus
• Most variable in size and shape
• It is very rudimentary at birth , develops by upward continuation of embryonic
infundibulum and frontal recess.
• Present at birth as small blind pocket , often difficulty in distinguishing from
ant ethmoidal cells in imaging
• First radiological evidence at 6 year of age
20

21. • Reaches adult size after puberty
• Embryologically it can also develops from anterior ethmoidal air cells
Pneumatization of frontal bone begins during 16th WOG originating from anterior
ethmoid complex
• At birth, frontal sinus appears With gradual pneumatization , seen radiologically at
the age of 8 yrs .
• Significant pneumatization doesn’t occurs until adolescent and continues until 18
yrs of age.
21

22. Ethmoid sinus
• During 9 -10th WOG: series of folds(ethnoturbinals) separated from each other by
corresponding grooves in lateral wall of nasal capsule.
• Fusion of folds leads to development of crests, each with ascending and
descending portion
• All permanent ethmoidal structure at birth are developed from crests and furrows
b/w them
Recognisable at around 3rd month
• At birth cavity of 2*2*1.5mm
• Reaches full size in adolescent and may expand further in old age.
• Pneumatization : 0.25mm each year from the age of 4 yrs but is not always
constant.
22

23. Ethmoturbinals : 4-5 series of lamella that must be removed in order to pass from
sinonasal cavity to the sphenoid sinus.
In order : Anterior to posterior these lamella includes
• First : agger nasi( ascending portion), and uncinate process( descending portion)
• Second : bulla ethmoidalis
• Third : basal lamella of middle turbinate
• Fourth: superior turbinate
• Fifth: supreme turbinate if present
23

24. Sphenoid sinus
• Due to evagination from sphenoethmoid recess at 12th WOG of
gestation.
• A small sphenoid sinus is present at birth with progressive
enlargement starting at age 3 during pneumatization of sphenoid
bone.
• Pneumatization rate 0.25/year from 4yrs+
• In some cases ICA and Optic nerve may lie naked within the sinus
cavity
24

25. • W.r.t sella turcica three types of
pneumatization:
• Sellar (90%)- most common
• Presellar(9%)
• conchal(1%)
(results in exposure of neurovascular
exposure surrounding sphenoid sinus, Imp for
planning of transphenoid approaches to
pituatory tumors)
25

26. Status at birth Growth First radiological
evidence
Maxillary sinus Present at birth
Volume 6-8 ml
Adult ( 14-15ml)
Rapid growth till 7 years
Adult size: 17-18 years
4-5 months after birth
Ethmoid sinus Present at birth
Anterior group ( 5*
2*2mm)
Posterior group( 5
*4*2mm)
Adult size : 12 years 1 year
Frontal sinus present as blind pocket
Difficult to distinguish
Invades frontal bone at
the age of 4 years .
Size increases until teens
and complete
development by 20 years.
6 -8 year
Sphenoid sinus present Sella turcica level: 7 yrs
Dorsum sella: late teens
Basisphenoid: adult
Full size: 15years ---adult
4 year
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27. Paranasal sinuses: overview
• Classified into two groups:
• Anterior group
• Posterior group
• Lined with mucus membrane continuous with that of corresponding nasal fossa
though their ostia.
• Pseudostratified columnar epithelium.
• Epithelium contains : mucinous and serous glands
27

28. Maxillary sinus
( Antrum of highmore)
• Pyramidal, First to appear,
• Largest of all paranasal sinus
(34*25*33mm)
• Reaches adult size by 15 years
• On average capacity of 15ml.
28

29. Boundaries
• Anterior wall: facial surface of maxilla and
cheek
• Posterior wall: infratemporal and
pterygopalatine fossa
• Medial wall : lateral wall of nasal cavity (
middle and inferior meatus- wall is thin
and membranous)
• Roof : major part of floor of
orbits(infraorbital a, and nerve)
• Floor: maxillary alveolus( alveolar part of
maxilla) and part of palatine process.
29

30. Drainage- Ostium
• Seen high up in the medial wall
• Does not open directly into nasal cavity , but
opens into posterior part of ethmoidal
infundibulum , via hiatus semilunaris in middle
meatus
• Infundibulum: air passage that connects
maxillary sinus ostium to middle meatus
• Unfav for natural sinus drainage
• Acessory ostium: 30 % of cases
30

31. Mucociliary clearence of maxillary sinus
• Mucus from all walls (anterior, medial, posterior,
lateral and roof is transported by the cilia to the
natural ostium and then through it into the middle
meatus
• Mucus always drains from the natural ostium, even
though accessory ostia be present in the fontanelle.
• It is also observed that inferior meatal antrostomy
made in Caldwell–Luc operation provides ventilation
to the sinuses, but it does not help in mucociliary
clearance which still takes place through the natural
ostium
31

32. Artery:
• Mainly from inferior orbital artery and greater palatine arteries of third part of maxillary
artery.
Venous: Anterior facial vein and pterygoid plexus.
Lymphatic drainage : relatively poor, into Pterygopaltine fossa and to Submandibular
nodes
Nerve supply:
• Maxillary div of trigeminal via
• Superior alveolar nerve( ant, middle, posterior)
• Infra orbital nerve
Pterygopalatine ganglion ( parasympathetic secretomotor) 32

33. Frontal sinus
• Most complex sinus, great variability in size and septation, rarely symmetrical
• 5% cases: rudimentary or often absent
• Situated b/w outer table and inner table(frontal bone)
• Funnel shaped ,2 sinuses on either side( sometimes absent)
• Intervening bony septum : may be thin or absent
33

34. • Shaped more or less like L
• Posterior wall: related to anterior cranial fossa
• Floor : upper part of orbit
• Drains into anterior part of middle meatus ( hiatus semilunaris) via frontonasal duct or
frontal recess.
• Natural ostium lies into posteromedial floor of the sinus( most dependent part)
• The ethmoidal infundibulum can acts as a channel for carrying the secretions from the
frontal sinus to anterior ethmoid cells and maxillary sinuses or vice versa
34

35. Frontal recess
• Frontal sinus outflow tract/ FSDP
• Hour glass shaped, 3D space
communicating with ethmoidal
infundibulum in middle meatus
• ( prev incorrectly termed as
frontonasal duct)
• Narrowest anterior air channels and are
common site of inflammation
• Obstruction: impairs ventilation and
mucociliary clearance of frontal sinus
35

36. • Anteriorly: agger nasi and frontal process
of maxilla,frontal beak
• Medial border: superior attachment of
middle turbinate, lateral lamella of
cribriform plate.
• Lateral border: lamina papyraceae
• Posterior border: anterior face of bulla( if
absent suprabulla aspace communicates
directly with frontal recess)
• In this situation , ant eth. Artery is not
protected by bulla lamella and at risk
during dissection of frontal recess
36

37. Classification of frontal recess cells
37
Bent and Kuhn classification

38. Posterior cell type:
1. Suprabulla: cells above bulla not pnematizing into frontal sinus
2. Frontalbulla /SBFC: pnematizing from bulla or suprabulla space
• These cells ‘CRAWLS’ along the skull base
3. Supraorbital ethmoid: pneumatizing orbital plate of fontal bone
Medial cell type:
• Intersinus/frontal septal: pnematizing interfrontal sinus septum
38

39. Fronto-ethmoidal cell in frontal recess
• Alters attachment of uncinate
process
• As in figure
39

40. Ostia and Mucocilary clearence
• At the anterior part of hiatus semilunaris
Mucociliary clearance: is unique
• Mucus travels up along the interfrontal septum,
along the roof of the lateral wall, along the floor and
then exits through the natural ostium.
• At two points, one just above the ostium and other
in the frontal recess, part of the mucus recycles
through the sinus( less than 60% exits)
• May carry infection of the frontal recess and sinuses
draining into it, towards the frontal sinus.
40
anticlockwise clockwise

41. • Artery : supraorbital and supratrochlear artery
• Venous: small vein that unites supraorbital and superior opthamic veins
• Lympatic drainage :Submandibular nodes
Nerve supply:
• Supraorbital nerve ( ophthalmic nerve)
• Supratrochlear nerve ( ophthalmic nerve)
41

42. Ethmoid sinus
• Situated close to the anterior skull base
• 2-8 anterior and 1-5 posterior ethmoidal cells in adults
• Anatomically divided into anterior , middle and posterior groups ( a/c to basal
lamella and drainage pattern)
• Anterior and middle group( 24* 23*11mm / ht*L*wd)
• Posterior group( 21*21*12mm)
• Present at birth
• Reaches adult size by 12 years
• First radiological evidence seen at 1st year
42

43. :
Relations
• Roof : anterior cranial fossa
• Lateral wall : orbit
• Medial wall ; nasal cavity
(Thin paper like bony part of ethmoid separating the air cells from the orbit , called lamina
papyraceae—can be easily destroyed leading to spread of ethmodal infections to orbit)
Drainage
• Anterior : a recess of hiatus semilunaris, infundibulum
• Middle meatus : via ethmoid bulla
• Posterior: sup. Meatus
43

44. Ethmoidal cells
• Anterior cells
• Agger nasi cells
• Terminal cells
• Suprainfundibular cells’
• Inferior cells
Agger nasi cells: 90% of individuals
• Opens into superior part of infundibulum
• Can impede drainage of frontal sinus
44

45. Haller cells
• Infraorbital ethmoid cells , arised from ant
ethmoidal cells
• Clinical significance:
• Closely related to infundibulum may
compromise ostium of maxillary sinus—
recurrent maxillary sinusitis
• become infected, with the potential for
extension into the orbit..
• may lead to inadvertent entry into the orbit if
unrecognised at endoscopic surgery
45

46. Onodi cells
• Posterior most cells of ethmoid sinus, optic nerve
and ICA closely related
Clinical significance:
• Potential damage to optic nerve and ICA when
attempt to enter sphenoid sinus endoscopilly
from Onodi cells.
46

47. Blood supply of ethmoid sinus
Artery
• Anterior and post ethmoidal ( ophthalmic a)
• Nasal branch of sphenopalatine artery
venous
Anterior and post ethmoidal veins and nasal veins
Nerve supply
• Anterior and posterior ethmoidal nerve and orbital branches of pterygopalatine
ganglion
• Postganglionic parasympathetic fibers for mucus secretion from facial nerve.
47

48. Drainage and mucociliary clearance
Anterior and middle group of ethmoid sinuses from posterior ethmoidal group
Joins that from the frontal and drains into superior meatus OR maxillary
sinus supreme meatus
Infront of torus tubarius into nasopharynx joins mucus from sphenoid sinus in
sphenoethmoidal recess above and
behind torus tubarius into nasopharynx
It is noted that infected discharge from the anterior group of sinuses, passes behind the
posterior pillars and causes hypertrophy of lateral pharyngeal bands.
Discharge from posterior group of sinuses spreads over the posterior pharyngeal wall.
48

49. Sphenoid sinus
• Occupies the body of sphenoid, in skull base at
junction of and anterior and middle cranial fossa
• 20mm(ht) * 23mm(L)* 17mm (wd)
• Right and left separated by thin strip of bony septm(
like frontal sinus)
• Relations of the sinuses are very important , especially
during the surgical approach of pituatory gland
49

50. Relations
Anterior part
• Roof : olfactory tract , optic chiasma and
frontal lobe
• Lateral : optic nerve , internal carotid artery
and maxillary nerve
50

51. Posterior part
• Roof : pituatory gland in sella turcica
• Lateral – cavernous sinus, ICA and
cranial nerves 3, 4 ,6 and all divisions of
trigeminal( 5th nerve)
51

52. Ostia and mucociliary clearence
• Ostia: 2mm *3mm, lies 10 mm above the floor
of sinus
• Communicates with the superior meatuses
indirectly through the sphenoethmoidal recess.
52

53. Blood supply and nerve
Artery :
• posterior ethmoidal artery ( roof of sinus)
• Sphenopalatine artery( floor of sinus)
Venous drainage : into maxillary vein and pterygoid plexus
Lymphatics : retropharyngeal nodes to upper deep cervical nodes
Nerve supply : trigeminal ( 1 and 2 divs)
53

54. Osteomeatal complex (OMC)
• Also known as osteomeatal unit/ key area/ or
critical area
• Final common pathway for drainage and
ventilation of ethmoid , maxillary and frontal
sinus.
Importance:
• Surgical strategies targets to eliminate the OMC
obstruction and restore sinonasal function.
• For performing FESS the knowledge of OMC
anatomy is important.
54

55. Boundaries
• Anteriorly : open and communication with
ant nasal cavity.
• Agger nasi and atrium of middle meatus in
antero superior and anterior relation to complex
• Superior: Basal lamella
• Posterior: Basal lamella continues along
the length of middle turbinate
• Inferior: Middle meatus
• Medial: Body of middle conchae
• Lateral: lamaina papayracea of ethmoid
55

56. Composition
• Maxillary ostium
• Infundibulum
• Ethmoidal bulla
• Uncinate process
• Hiatus semilunaris
56

57. Common anatomical variations
• Conchae bullosa( 30% of
individuals)
• Paradoxical middle turbinate( 10%
of individuals)
Others:
• uncinate process hypertrophy and
pneumatization
• Hypertrophy of bulla ethmoidalis and
agger nasi cells
• Presence of maxilo-ethmoidal cell(
haller cell)
57

58. Pterygopalatine fossa
• Inverted 'tear-drop’ shape, clinically
inaccessible, fat filled space between bones
on the lateral side of the skull immediately
posterior to the maxilla
• Major neurovascular cross roads between
oral cavity, nasal cavity, nasopharynx,
orbit, masticator space, and the middle
cranial fossa.
• The multiple communications of the PPF
with the deep neck spaces serve as ready
pathways for loco-regional and perineural
spread of disease.
58

59. • Although small in size, the
pterygopalatine fossa communicates
via fissures and foramina in its walls
with:
• the middle cranial fossa;
• infratemporal fossa;
• floor of the orbit;
• lateral wall of the nasal cavity;
• oropharynx;
• roof of the oral cavity
59

60. Gateway
60
7 important foramina and fissures provide apertures that enter
and leave the pterygopalatine fossa.
Posterior wall:
• the foramen rotundum and pterygoid canal middle cranial
fossa
• small palatovaginal canal
Inferior wall: palatine canal
Medial wall: Sphenopalatine foramen
Lateral wall: Continuous with the infratemporal fossa via a
large gap ( pterygomaxillary fissure) between the posterior
surface of the maxilla and pterygoid process of the sphenoid
bone;
Anterior wall: superior aspect opens into floor of the orbit
via the inferior orbital fissure

61. Nerve and ganglion in pterygopalatine fossa
61
Maxillary nerve (v2)
• Origin
• Pass the fossa and exits as infraorbital
nerve through inferior orbital fissure.
While Within fossa
1. post superior alveolar nerve
2. two ganglionic branches
Other Branches
• Orbital : sphenoidal and ethmoid sinus
• Greater and lesser palatine: enter the oral surface
of palate
• Nasal : medially from sphenopalatine foramen
mostly to lateral wall >medial wall of nasal
cavity

62. Nerve to pterygoid canal
62
Nerve of pterygoid canal carrying
• Preganglionic parasympathetic fibers from greater
petrosal branch of facial n
• Post ganglionic sym fibers from deep petrosal
branch of carotid plexus

63. Maxillary artery
63
Artery
Pterygopalatine part :
• Greater palatine artery
• Posterosuperior alveolar artery
• Infraorbital artery
• Pharyngeal branch
Artery of pterygoid canal( from pterygoid part)
Veins
• Adjacent veins with branches traverses via
pterygopalatine fossa and joins the pterygoid
plexus of veins in infratemporal fossa.

64. Infratemporal fossa
64
• Wedge-shaped fossa
• Inferior to the temporal fossa
• Between the ramus of the mandible
laterally and the wall of the pharynx
medially.

65. • Anteriorly: post surface of maxilla.
• Roof: inf surface of greater wing of
sphenoid
• Lateral wall: medial surface of ramus of
mandible
• Medial wall : lateral plate of pterygoid plate
and more posteriorly by pharynx and 2 ms
of soft palate( TVP , LVP)
• Also pterygomaxillary fissure: passage
b/w infratemporal fossa and
pterygopalatine fossa.
65

66. Major Contents:
• Sphenomandibular ligament
• Medial( deep and sup head) and lateral
pterygoid ms
• Maxillary artery
66

67. 67
• Mandibular nerve
• Chorda tympani nerve
• Lingual nerve
• Inferior alveolar nerve
• Pterygoid plexus of veins

68. ……Thank you
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