Anatomy Of Paranasal SinusesNafisa parveen Jawaharlal nehru medical college Aligarh muslim university India

1

www.nayyarENT.com

7/30/2012

Paranasal sinus Air-filled pockets within the cranium which

communicate with the nasal cavity and lined with the same type of ciliated mucous membrane. Late 19th century Emil Zukerkandl published 1st detailed anatomic and pathologic description of paranasal sinus. Father of modern sinus anatomy .

2

www.nayyarENT.com

7/30/2012

Paranasal sinus Divided in two groups-

Anterior group

Frontal Maxillary Anterior ethmoid Posterior group posterior ethmoid sphenoid

3

www.nayyarENT.com

7/30/2012

Development of PNS All except sphenoid sinus develop as

outpouchings from the mucous membrane of lateral wall of nose. Sphenoid sinus arises within the nasal capsule of the embryonic nose.

4

www.nayyarENT.com

7/30/2012

Maxillary sinus Antrum of highmore

These paired sinuses lie under the cheek. Largest and most constant pns. First sinus to develop. These structures are usually fluid-filled at birth. Appears slit like in fetal life. Adult maxillary sinus is pyramidal in shape. Volume of maxillary sinus approximately 15ml.

5

www.nayyarENT.com

7/30/2012

Maxillary sinus It has biphasic growth.

The 1st phase of growth occur during the 1st 3yrs

of life. The 2nd phase occur btw 7-18yrs . During the later phase pneumatization spreads more inferiorly as the permanent teeth take their place. Pneumatization can be so extensive as to expose tooth roots with only a thin layer of soft tissue covering them.6 www.nayyarENT.com 7/30/2012

Maxillary sinusBase(medial wall) The base of the pyramid corresponds to the lateral nasal wall. This wall has its convexity facing the sinus. The central portion of the base is very thin, in some areas could even be membranous. The natural ostium of this sinus is present in this wall.

7

www.nayyarENT.com

7/30/2012

Natural ostium Located at the superior aspect of the medial wall of

8

the maxillary sinus. Intranasally ,natural ostium is in anterior fontanelle. The posterior edge of the ostia is continuous with the lamina papyracea. Size averages 2.4mm but can vary from 1 to 17mm. The ostium is much smaller than actual bony defect,as mucosa fills this area. 88% of maxillary ostium are hidden behind the uncinate process. Cannot visualised endoscopically. Seen after uncinectomy. Opens in the post part of ethmoidal infundibulum into the middle meatus.7/30/2012

www.nayyarENT.com

Accessory ostia Usually found in the posterior fontanelle.

Circular in shape. Easily seen unlike the natural ostia. They are nonfunctional ostia. Serve to drain the sinus only if the natural ostium

is blocked and intrasinus pressure moves material out of the ostium. Incidence varies from 15%-45%,an average of 25%

9

www.nayyarENT.com

7/30/2012

Maxillary sinusAnterior wall Wall corresponds to the facial surface of the superior maxilla. Over canine fossa it is only 2mm in thickness. Through this fossa maxillary antrum is entered during caldwell luc surgery.

10

www.nayyarENT.com

7/30/2012

Boundaries of canine fossa Inferiorly-bounded by the alveolar ridge.

Laterally-bounded by the canine eminence which

is caused by the canine tooth. Superiorly infra orbital foramen which located at the midsuperior portion with the infra orbital nerve running over the roof of the sinus and exiting through the foramen.this nerve can be dehiscent in 14% Medially- pyriform aperture

11

www.nayyarENT.com

7/30/2012

Maxillary sinusPosterior wall Also known as temporal surface. It is very thick. Formed by the body of the superior portion of the maxilla. Behind this wall is the pterygomaxillary fossa with the internal maxillary artery, sphenopalatine ganglion and the vidian canal, the greater palatine nerve and the foramen rotundum.

12

www.nayyarENT.com

7/30/2012

Maxillary sinusRoof Formed by thin orbital wall. Which is traversed by the infra orbital foramen containing the infra orbital vessels and nerves. This wall is very fragile. Any disease process involving the maxilla is likely to affect the orbit through this wall. This wall is further thinned out where the infra orbital canal is present.

13

www.nayyarENT.com

7/30/2012

Maxillary sinusFloor Formed by the alveolar process of the maxilla and the hard palate. The roots of the 1st and 2nd molar reach upto the floor of the maxillary sinus. From birth to age 9yrs the floor of the sinus is above the level of nasal cavity. At 9yrs the floor lies at the same level as that of the nasal cavity. In adult it lies 5-10mm below the nasal cavity. Dental infections involving the 1st and 2nd molars may involve the maxillary sinus.14 www.nayyarENT.com 7/30/2012

Arterial supplyBranches of the internal maxillary artery i.e. Infraorbital artery Lateral branches of the sphenopalatine Greater palatine artery Alveolar artery

15

www.nayyarENT.com

7/30/2012

Venous supply Venous drainage runs anteriorly into the facial

vein. Posteriorly into the maxillary vein and jugular and dural sinus system.

16

www.nayyarENT.com

7/30/2012

Nerve supplyInnervated by branches of V2. Greater palatine nerve Infraorbital nerve

17

www.nayyarENT.com

7/30/2012

Ethmoid sinus Situated in the anterior skull base.

Made up of complex bony labyrinth of thin walled

18

cells. A few ethmoid cells may be present at birth. At birth it is filled with fluid. In adult 3-14 ethmoid cells may be present. During primary pneumatization ethmoids develop from dimple like depression on nasal mucosa, deepen and become air cells. The common infections affecting the pediatric age group occur in this sinuses.7/30/2012

www.nayyarENT.com

Ethmoid sinus Well-delineated.

Ant cells form 1st, followed by the posterior cells. The cells grow gradually and are adult size by

age 12. They are not seen on radiographs until age one. Ant and post combined volume is 15ml. Pyramidal in shape Divided into multiple cells by thin septa.

19

www.nayyarENT.com

7/30/2012

Lateral wall Formed by the orbital plate of the ethmoid,known

as the lamina papyracea. this wall could be dehiscent(normal variant) Infections involving the ethmoid air cells may spread to the orbit through this wall.

20

www.nayyarENT.com

7/30/2012

Roof Formed by the frontal bone anteriorly Posteriorly by the sphenoid and orbital process of

21

palatine bone. The roof slopes both posteriorly(angle of 15 degrees) and medially. Ant 2/3 of the roof is thick and strong and composed of the frontal bone and the foveolae ethmoidalis. The post 1/3 is higher laterally and slopes down medially to the cribiform plate. The difference btw the lat and medial roof is variable,but can be as much as 15-17mm.. www.nayyarENT.com The post aspect of the ethmoid cells borders on the 7/30/2012 sphenoid sinus.

Ethmoid cells The ant cells drain into the infundibulum of the

middle meatus. Post cells drain into the superior meatus. The anatomy of the ethmoidal cells are highly variable. A cell above the orbit is called a supraorbital cell. found in 15% of pt. Invasion of an ethmoid cell into the floor of the frontal sinus is called a frontal bulla.

22

www.nayyarENT.com

7/30/2012

Concha bullosa Sometimes the middle turbinate may contain an air

cell known as concha bullosa. An enlarged concha bullosa may impede drainage from the middle meatus.

23

www.nayyarENT.com

7/30/2012

Agger nasi air cells Anterior most anterior ethmoid air cells. 1st prominent anatomical landmark encountered

24

in FESS. Located antero-superior to insertion of middle turbinate. Endoscopically seen as a ridge ,prominence on lateral wall. Boundaries Anteriorlyfrontal process of maxilla Posteriorly-- ethmoidal infundibulum Superiorlyfrontal recess and frontal sinus Infero-mediallyuncinate process www.nayyarENT.com 7/30/2012 Laterallynasal and lacrimal bone

Agger nasi air cells Since these cells lie in close proximity to the

25

frontal recess area, they could impede ventilation and drainage of the frontal sinus. Commonly involved in the pathogenesis of the formation of frontal mucocele. At 1st the frontal sinus enlarges in size by expansion of its bony walls. At a later stage bone erosion can occur. Commonly the post table of the frontal sinus is eroded. Ant.table also can be eroded in rare cases.7/30/2012

www.nayyarENT.com

Haller cells Ethmoidal air cells belonging to the anterior

ethmoidal group. Also known as the infra orbital cells. best studied on ant and post coronal ct images. Adhere to roof of maxillary sinus forming the lat wall of infundibulum. Incidence 10-40% Enlargement of these cells can impede the maxillary sinus drainage.

26

www.nayyarENT.com

7/30/2012

Onodi cells Post group of ethmoidal air cells.

Supero-lateral to the sphenoid sinus. Incidence 9-12% Optic nerve and medial rectus muscle lie in close

relation with the lateral wall of this cells. making them at risk during fess surgeries.

27

www.nayyarENT.com

7/30/2012

Vascular supply The sphenopalatine artery as well as the

ophthalmic artery which branches into the anterior and posterior ethmoid arteries supply the sinus. Venous drainage follows arterial supply.

28

www.nayyarENT.com

7/30/2012

Nerve supply Both V1 and V2 innervate this region.

V1 supplies the more superior aspect . V2 supplies the inferior regions. Parasympathetic innervation is via the vidian

nerve. Sympathetic innervation is via the cervical sympathetic ganglion.

29

www.nayyarENT.com

7/30/2012

Frontal sinus Formed by the upward movement of the anterior most 30

ethmoid cells. Pyramidal in shape. The volume of the sinus is approximately 6-7ml. Rudimentary at birth. True growth begins at age five and continues into the late teens. Among the paranasal sinuses this sinus shows the maximum variations. Sinuses are unique in each and every individual Asymmetry btw the two sinuses. It may be absent in 5% of cases.7/30/2012

www.nayyarENT.com

Frontal sinus Both the anterior and posterior walls of this sinus

are composed of diploe bone. The post wall separates the frontal sinus from the anterior cranial fossa, is much thinner. Floor is formed by the upper part of the orbits. Both frontal sinuses have their ostia at the most dependant portion of the cavity(posteriomedially) So these sinuses are rarely involved with infectious disease.

31

www.nayyarENT.com

7/30/2012

Frontal recess Space btw the frontal sinus and the hiatus

semilunaris into which the frontal sinus drains. Bounded Anteriorly-agger nasi cell Superiorly-frontal sinus Medially- middle turbinate Laterally- lamina papyracea

32

www.nayyarENT.com

7/30/2012

Vascular supply Ophthalmic artery via the supra orbital and supra

trochlear arteries. Venous drainage is via superior ophthamic veins to the cavernous sinus and via small venulae in the posterior wall which drain to the dural sinuses.

33

www.nayyarENT.com

7/30/2012

Nerve supply Innervated by branches of V1.

Supraorbital and supratrochlear branches.

34

www.nayyarENT.com

7/30/2012

Sphenoid sinus It is located in the skull base at the junction of the

35

anterior and middle cranial fossa. Bilateral and asymmetry very common. Adult volume of the sinus is 7.5ml. Extensive variation in pneumatisation. Pneumatisation can extend as far as the clivus, the sphenoid wings and the foramen magmum. The walls of the sphenoid vary in thickness with the anterosuperior wall and roof being the thinnest(.1 to 1.5mm) The other wall are thicker.7/30/2012

www.nayyarENT.com

Pneumatisation The position of the sinus depend on the extent of

pneumatisation. 3 types of pneumatisation seen Conchal(fetal)2% Presellar(juvenile)10-24% Sellar(adult)86%

36

www.nayyarENT.com

7/30/2012

Pneumatisation These sinuses arise from within the nasal

capsule of the embryonic nose. They remain undeveloped until age three. By age seven the pneumatisation has reached the sell turcica. By age 18 the sinuses have reached full size.

37

www.nayyarENT.com

7/30/2012

Sphenoid sinus ostia Drains into the sphenoethmoidal recess. The ostium is located 1-1.5cm above the posterior

38

end of choana. A 30degree angle drawn from the ant nasal floor approximates the location of the ostium on the posteriosuperior nasal wall. It is close to the midline at the junction of the upper 1/3 and the lower 2/3 of the anterior sinus wall. medial to the supreme/superior turbinate,and only few mm from the cribiform plate. The ostium is very small.5-4mm . Has a much larger bony dehiscence which is narrowed by a membranous septum. Below the ostia is the mesh of blood vessels forming the woodruffs plexus www.nayyarENT.com 7/30/2012

Spheno-ethmoidal recess Recess is a space behind and above the most

superior turbinate. The ant wall of the sphenoid sinus forms the posterior aspect. The nasal septum and cribiform plate form the medial and superior aspects . The anterolateral extent is determined by the most superior turbinate. The space opens into the nasal cavity inferiorly. The posterior ethmoid cells and sphenoid sinus empty into this region.7/30/2012

39

www.nayyarENT.com

Related structure Pituitary gland lies above the sphenoid sinus.

Optic nerve and internal carotid arteries traverse

its lateral wall. The nerve of pterygoid canal lie in thefloor of the sinus.

40

www.nayyarENT.com

7/30/2012

Vascular supply Posterior ethmoid artery supplies the roof of the

sphenoid sinus. Rest of the sinus is supplied by the sphenopalatine artery. Venous drainage is via maxillary veins to the jugular and pterygoid plexus system.

41

www.nayyarENT.com

7/30/2012

Nerve supply Supplied by branches from both V1 and V2.

The nasociliary nerve (V1) supplies the roof. The branches of the sphenopalatine

nerve(V2)supply the floor.

42

www.nayyarENT.com

7/30/2012

Lymphatic drainage of pns The lymphatics of maxillary,ethmoid,frontal and

sphenoid sinuses form a capillary network in their lining mucosa and collect with lymphatics of nasal cavity. Then they drain into lateral retropharyngeal and /or jugulodigastric nodes.

43

www.nayyarENT.com

7/30/2012

Microscopic anatomy Sinuses are lined with pseudostratified ciliated

44

columnar epithelium which is continuity with the mucosa of the nasal cavities. The epithelium of the sinuses is thinner than that of the nose. There are four basic cell types. Ciliated columnar epithelial cells Nonciliated columnar cells Basal cells Goblet cells7/30/2012

www.nayyarENT.com

Ciliated columnar epithelium The ciliated cells have 50-200 cilia per cell.

Usual structure of 9+2 microtubules with dynein

arms. These cells beat at 700-800 times a minute. Moving mucus at a rate of 9mm/minute

45

www.nayyarENT.com

7/30/2012

Non ciliated columnar cells Characterized by microvilli which cover the apical

aspect of the cell Serve to increase surface area Likely to facilitate humidification and warming of inspired air. There is an increased concentration upto 50% at the sinus ostium.

46

www.nayyarENT.com

7/30/2012

Goblet cells Basal cells function is unknown.

Goblet cells produce glycoproteins which are

47

responsible for the viscosity and elasticity of mucus. They are innervated by the parasympathetic and sympathetic nervous system. The parasympathetic stimulation induces thicker mucous . Sympathetic stimulation leading to more watery mucous secretion. Goblet cells are less in sinuses than nasal www.nayyarENT.com 7/30/2012 mucosa.

Microscopic anatomy The epithelial layer is supported by a thin

basement membrane, lamina propria and periosteum.

48

www.nayyarENT.com

7/30/2012

Thank youFor more topics, visit www.nayyarENT.com

49

www.nayyarENT.com

7/30/2012