The document summarizes the anatomy and variations of the paranasal sinuses. It describes the locations and openings of the different sinus groups. Key anatomical structures involved in sinus drainage like the osteomeatal complex are also explained. Common anatomic variations seen on imaging that can affect sinus drainage are discussed. These variations include concha bullosa, Haller cells, Onodi cells and pneumatization of surrounding bones.

1. PRESENTER --- SARBESH TIWARI

2.  Paranasal sinuses are air containing cavities in certain bones of
skull.
 Clinically, Divided into two groups:
1. Anterior group. This includes maxillary, frontal ,
anterior and middle ethmoidal air cells. They all open in the
middle meatus.
2. Posterior groups. This includes posterior ethmoidal
sinuses which open in the superior meatus, and the sphenoid
sinus which open in sphenoethmoidal recess.
Disease of ear, nose & throat 4th edition – PL Dhingra

3.  Paranasal sinuses develop as out-pouchings from the
mucous membrane of lateral wall of nose.
 At birth, only the maxillary and ethmoidal sinuses are present
and are large enough to be clinically significant.
 Growth of sinuses continues during childhood and early adult
life.
 Radiologically, maxillary sinuses can be identified at 4-5
months, ethmoids at 1 year, frontals at 6 years and sphenoids
at 4 years of age.

4. Disease of ear, nose & throat 4th edition – PL Dhingra

5. Function Histology
 They lighten the Facial skeleton
 Air-conditioning of the inspired
air by providing large surface
area over which the air is
humidified and warmed.
 To provide resonance to voice.
 They are lined by
Psuedostratified columnar
epithelium studded with
mucus and serous glands.

6.  Also known as antrum of Highmore
(1651).
 Largest paranasal sinus occupying the
maxilla.
 Pyramidal in shape with base toward the
lateral wall of nose and apex directed
laterally into the zygomatic process.
 Capacity of 15 ml (average).

7.  Anterior wall – facial surface of maxilla and related to the soft
tissue of the cheek.
 Posterior wall – infratemporal and pterygopalatine fossae.
 Medial wall – middle and inferior turbinate
 Floor – alevolar and palatine process of maxilla. Related to all
the molar tooth and sometimes the premolar teeth.
 Roof – Formed by the floor of the orbit. Traversed by
infraorbital nerve and vessels.

9.  Paired sinuses situated deep to the inner and outer table of
frontal bone.
 It drains through the frontal recess to the middle
meatus via the ostiomeatal complex.
 Frontal sinus may be absent on one or both sides or it may
be very large extending into orbital plate in the roof of the
orbit.

10.  Anterior wall -- The skin over the forehead.
 Inferior wall -- The orbit and its contents.
 Posterior wall -- The meninges and frontal lobe of the brain.
 The frontal recess, the drainage pathway of the frontal sinus,
is situated at its floor and usually drains into the middle
meatus (62%) or into the ethmoid infundibilum (38%).

12.  Ethmoidal sinuses are thin-walled air cavities in the lateral masses of
ethmoid bone.
 Clinically, ethmoidal cells are divided into :-
1. Anterior ethmoidal air cells – Up to 11 anterior ethmoidal air cells
drain into either the ethmoidal infundibulum or the frontonasal duct.
2. Bullar cells ( middle ethmoidal air cells) -- usually less than three
middle ethmoidal air cells. Opens in ethmoidal infundibulum.
3. Posterior group :- Up to seven posterior ethmoidal air cells usually
drain by a single orifice into the superior meatus.

13.  Roof -- Anterior cranial fossa. Meninges of the brain form
important relation here.
 Floor – maxillary sinus and hiatus semilunaris.
 Lateral wall – lamina papyracea of the orbit.
 Medially - nasal cavity & medial plate of ethmoid.
 Optic nerve forms close relationship with the posterior ethmoidal
cells and is at risk during ethmoid surgery.

14.  It occupies the body of sphenoid.
 The two, right and left sinuses, are rarely symmetrical and are
separated by a thin bony septum.
 Ostium of the sphenoid sinus is situated in the upper part of
its anterior wall and drains into sphenoethmoidal recess.
 Average size – 2 x 2 x 2 cm.

15. According to Congdon , sphenoid
pneumatization can be as follows
A. Conchal – 5 %
B. Presellar – 23 %
C. Post-sellar – 67%

16. ANTERIOR PART
 Roof – related to the
olfactory tract, optic
chiasma and frontal lobe
 Lateral wall -- related to
the optic nerve, internal
carotid artery and
maxillary nerve
POSTERIOR PART
 Roof -- Related to pituitary
gland in the sella turcica.
 Lateral wall -- related to
cavernous sinus, internal
carotid artery and CN III,
IV, VI and all the divisions
of V

18. Marked by 3 projections:
 Superior concha
 Middle concha
 Inferior concha
 The space below each
concha is called a meatus.

19. 1. Inferior meatus:
nasolacrimal duct
2. Middle meatus:
• Maxillary sinus
• Frontal sinus
• Anterior ethmoid sinuses
3. Superior meatus:
posterior ethmoid sinuses
4. Sphenoethmoidal recess:
sphenoid sinus

20.  The ostiomeatal complex (or unit) is a common channel that
links the frontal sinus, anterior and middle ethmoid sinuses and
the maxillary sinus to the middle meatus.
 The ostiometal complex is composed of five structures:
1. Maxillary ostium - drainage channel of the maxillary sinus
2. Infundibilum - common channel that drains the ostia of the
maxillary and ethmoid sinuses to the hiatus semilunaris

21.  Ethmoidal bulla - usually a single air cell that projects
inferomedially over the hiatus semilunaris
 Uncinate process - hook-like process that arises from the
posteromedial aspect of the nasolacrimal duct and forms the
anterior boundary of the hiatus semilunaris
 Hiatus semilunaris - final drainage passage; a region between the
ethmoidal bulla superiorly and free-edge of the uncinate process

45. Paradoxical curvature:
Normally the convexity of the middle
turbinate is directed medially toward
the nasal septum.
When the convexity is directed
laterally, it is termed a paradoxical
middle turbinate .
Most authors agree that the
paradoxical middle turbinate can be a
contributing factor to sinusitis.

46. Concha bullosa:
This is an aerated turbinate, most often
the middle turbinate.
When pneumatization involves the
bulbous portion of the middle turbinate,
it is termed concha bullosa.
If only the attachment portion of the
middle turbinate is pneumatized, it is
termed lamellar concha .
A concha bullosa may obstruct the
ethmoid infundibulum.

47. The uncinate process may be
medialized, lateralized, or
pneumatized/bent.
Medialization occurs with giant bulla
ethmoidalis.
Lateralization of the uncinate process
may obstruct the infundibulum.
Pneumatization of the uncinate
process (uncinate bulla) can rarely
cause obstruction of the
infundibulum.

48.  They are the most anterior
ethmoidal air cells.
 It lies anterior, lateral, and inferior
to the frontal recess.
 Its size may directly influence the
patency of the frontal recess and
the anterior middle meatus.

49.  Also called infraorbital ethmoid
cells.
 Extramural ethmoidal air
cells that extend into the
inferomedial orbital floor.
 Present in approx. 20 % pateints.
Clinical significance –
 Become infected , with potential
extension into orbit.
 Narrows the maxillary ostium.

50.  These are posterior ethmoidal cells
extending into the sphenoid
bone ,either adjacent to or
impinging upon the optic nerve.
 When these Onodi cells abut or
surround the optic nerve, the nerve
is at risk when surgical excision of
these cells is performed.
 It is also a potential cause of
incomplete sphenoidectomy.

51. The ethmoid roof is of critical importance for two reasons.
 First, it is most vulnerable to iatrogenic cerebrospinal fluid leaks.
 Second, the anterior ethmoid artery is vulnerable to injury.
The depth of the olfactory fossa is determined by the height of the lateral
lamella of the cribriform plate.
In 1962, Keros had classified the depth of the olfactory fossa into three types,
that is,
Keros type I: <3 mm , type II: 4-7 mm ,and type III: 8-16 mm
Kero type III is most vulnerable to iatrogenic injury.

52. Coronal CT scan shows that the ethmoid
roofs are almost in the same plane as the
cribriform plate (double arrow) - Keros
type I
Coronal CT reveals the olfactory fossae
are deeper and the lateral lamellae are
longer (double arrow) - Keros type II
Coronal CT shows that the olfactory
fossae are very deep (double arrow) -
Keros type III

53.  Agenesis of sphenoid sinus

54. Pneumatization of the anterior clinoid process (bent up arrow) and bilateral
pterygoid processes (star), with protrusion and partial dehiscence of bilateral vidian
nerves (arrow).

55. Pneumatized bilateral greater wing of sphenoid (star), with protrusion of maxillary nerve
bilaterally (arrow). The left maxillary nerve is dehiscent. Note also the protuberant vidian
nerves bilaterally (downward curved arrow)

56.  The bulla ethmoidalis is a
prominent anterior ethmoid air
cell.
 A degree of pneumatisation may
vary, and failure to pneumatise is
termed torus ethmoidalis.
 A 'giant bulla' may fill the entire
middle meatus and force its way
between the uncinate process
and the middle turbinate.

57.  The crista galli is normally bony.
 When aerated, it may
communicate with the frontal
recess, causing obstruction of the
ostium and thus lead to chronic
sinusitis and mucocele
formation.

60. 1. Uma Devi Murali Appavoo Reddy, Bhawna Dev. Pictorial essay: Anatomical variations
of paranasal sinuses on multidetector computed tomography-How does it help FESS
surgeons? Indian journal of radiology & imaging 2012, vol -22 pg 317- 324.
2. Ashok K Gupta et.al. Anatomy and its variation for endoscopy sinus surgery . Clin
rhinol An Int J 2012; 5(2)55-62.
3. Multiplanar Sinus CT: A Systematic Approach to Imaging Before Functional
Endoscopic Sinus Surgery Jenny K. Hoang, James D. Eastwood, Christopher L. Tebbit,
and Christine M. Glastonbury American Journal of Roentgenology 2010 194:6, W527-
W536
4. Laurie A. Loevner et al. Imaging of neoplasms of the paranasal sinuses, Neuroimag
Clin N Am 14 (2004) 625 – 646
5. David L. Daniels et.al. The Frontal Sinus Drainage Pathway and Related Structures,
AJNR: 24, August 2003.
6. Disease of Ear, Nose & Throat . P.L Dhingra 4th edition.
7. Interactive Atlas. http://uwmsk.org/sinusanatomy2/axial/axial.html.

61. Thank you..