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Nafisa parveen Jawaharlal nehru medical college Aligarh muslim university India Anatomy Of Paranasal Sinuses 7/30/2012 www.nayyarENT.com 1

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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 19 th century Emil Zukerkandl published 1 st detailed anatomic and pathologic description of paranasal sinus. Father of modern sinus anatomy. 7/30/2012 www.nayyarENT.com 2

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Paranasal sinus Divided in two groups- Anterior group Frontal Maxillary Anterior ethmoid Posterior group posterior ethmoid sphenoid 7/30/2012 www.nayyarENT.com 3

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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. 7/30/2012 www.nayyarENT.com 4

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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. 7/30/2012 www.nayyarENT.com 5

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Maxillary sinus It has biphasic growth. The 1 st phase of growth occur during the 1 st 3yrs of life. The 2 nd 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. 7/30/2012 www.nayyarENT.com 6

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Maxillary sinus Base(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. 7/30/2012 www.nayyarENT.com 7

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Natural ostium Located at the superior aspect of the medial wall of 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 8

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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% 7/30/2012 www.nayyarENT.com 9

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Maxillary sinus Anterior 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. 7/30/2012 www.nayyarENT.com 10

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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 7/30/2012 www.nayyarENT.com 11

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Maxillary sinus Posterior 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. 7/30/2012 www.nayyarENT.com 12

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Maxillary sinus Roof 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. 7/30/2012 www.nayyarENT.com 13

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Maxillary sinus Floor Formed by the alveolar process of the maxilla and the hard palate. The roots of the 1 st and 2 nd 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 1 st and 2 nd molars may involve the maxillary sinus. 7/30/2012 www.nayyarENT.com 14

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Arterial supply Branches of the internal maxillary artery i.e. Infraorbital artery Lateral branches of the sphenopalatine Greater palatine artery Alveolar artery 7/30/2012 www.nayyarENT.com 15

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Venous supply Venous drainage runs anteriorly into the facial vein. Posteriorly into the maxillary vein and jugular and dural sinus system. 7/30/2012 www.nayyarENT.com 16

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Nerve supply Innervated by branches of V2. Greater palatine nerve Infraorbital nerve 7/30/2012 www.nayyarENT.com 17

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Ethmoid sinus Situated in the anterior skull base. Made up of complex bony labyrinth of thin walled 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 18

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Ethmoid sinus Well-delineated. Ant cells form 1 st, 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. 7/30/2012 www.nayyarENT.com 19

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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. 7/30/2012 www.nayyarENT.com 20

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Roof Formed by the frontal bone anteriorly Posteriorly by the sphenoid and orbital process of 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.. The post aspect of the ethmoid cells borders on the sphenoid sinus. 7/30/2012 www.nayyarENT.com 21

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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. 7/30/2012 www.nayyarENT.com 22

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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. 7/30/2012 www.nayyarENT.com 23

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Agger nasi air cells Anterior most anterior ethmoid air cells. 1 st prominent anatomical landmark encountered 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 Laterallynasal and lacrimal bone 7/30/2012 www.nayyarENT.com 24

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Agger nasi air cells Since these cells lie in close proximity to the 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 1 st 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 25

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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. 7/30/2012 www.nayyarENT.com 26

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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. 7/30/2012 www.nayyarENT.com 27

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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. 7/30/2012 www.nayyarENT.com 28

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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. 7/30/2012 www.nayyarENT.com 29

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

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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. 7/30/2012 www.nayyarENT.com 31

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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 7/30/2012 www.nayyarENT.com 32

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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. 7/30/2012 www.nayyarENT.com 33

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Nerve supply Innervated by branches of V1. Supraorbital and supratrochlear branches. 7/30/2012 www.nayyarENT.com 34

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Sphenoid sinus It is located in the skull base at the junction of the 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 35

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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% 7/30/2012 www.nayyarENT.com 36

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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. 7/30/2012 www.nayyarENT.com 37

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Sphenoid sinus ostia Drains into the sphenoethmoidal recess. The ostium is located 1-1.5cm above the posterior 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 7/30/2012 www.nayyarENT.com 38

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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 www.nayyarENT.com 39

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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. 7/30/2012 www.nayyarENT.com 40

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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. 7/30/2012 www.nayyarENT.com 41

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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. 7/30/2012 www.nayyarENT.com 42

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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. 7/30/2012 www.nayyarENT.com 43

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Microscopic anatomy Sinuses are lined with pseudostratified ciliated 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 cells 7/30/2012 www.nayyarENT.com 44

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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 7/30/2012 www.nayyarENT.com 45

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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. 7/30/2012 www.nayyarENT.com 46

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Goblet cells Basal cells function is unknown. Goblet cells produce glycoproteins which are 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 mucosa. Maxillary sinus has the highest density of goblet cells. 7/30/2012 www.nayyarENT.com 47

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Microscopic anatomy The epithelial layer is supported by a thin basement membrane, lamina propria and periosteum. 7/30/2012 www.nayyarENT.com 48

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