This presentation includes cross sectional anatomy like axial,saggital and coronal images of paranasal sinuses and most important variation of paranasal sinus.This help alot. Must read topic for radiology resident. Thanks

1. CT Anatomy of
PNS(Paranasal sinuses)
Dr. Pradeep Kumar

2. •
•
•
•
•
NOSE AND NASAL FOSSA
PARA NASAL SINUSES OSTEOMEATAL COMPLEX
ANATOMICAL VARIATIONS IMAGING MODALITIES
CT PROCEDURE & SECTIONS
CONCLUSION

3. Bony part & cartilaginous part covered by muscle & skin
Cartilaginous part – upper & lower lateral cartilages, lesser
alar
cartilages & septal cartilage
Nasal skin
Internal nose divided into the Right and left by the nasal
septum

4. NASAL CAVITY PROPER
Roof – Nasal bone,
sphenoid & ethmoid bone
Floor - Palatine process of
the maxilla & Palatine bone
Medial wall
Lateral wall

6. Mainly by both Internal &
external carotid, both on the
septum & lateral walls
Anterior & posterior
ethmoidal artery
Sphenopalatine artery
Septal branch of greater
palatine
Septal branch of superior
labial artery

7. 



Formed by bony, soft tissue &
cartilage
Bony –
Ethmoid infundibulum &
uncinate
Perpendicular plate of palatine
bone
Medial plate of pterygoid
process of sphenoid bone
Medial surfaces of lacrimal
bones and maxillae

8. Cartilage – In external nose, the
lateral wall of cavity is supported
by cartilage (lateral process of
septal cartilage & major, minor
alar cartilage)

9. Marked by three bony projections, they extend medially across the
nasal cavity separating the nasal cavity into for air channels – the
turbinates or conchae
Superior ,middle & inferior tubinates or conchae. The conchae do
not extend forwards into the external nose
The air space below and lateral to each turbinate is called as
meatus
Superior, middle & inferior meatus & sphenoethmoidal recess
Middle Meatus – much significant

11. Superior Meatus – Limited only to posterior one third of
lateral wall. Posterior ethmoidal sinus opens into it.
Middle
Meatus
Inferior Meatus – Runs along the whole length of lateral wall.
Nasolacrimal duct opens in its anterior part. Largest of all
meatus
Sphenoethmoidal recess – Above the superior turbinate.
It receives the opening of sphenoid sinus

14. Infundibulum – Air passage
connecting the maxillary
sinus ostium to middle
meatus
Hiatus Semilunaris – Gap
between the uncinate
process and bulla
ethmoidalis. Medially it
communicates with middle
meatus. Laterally & inf it
communicates with

15. Frontal sinus – Opens into the
anterior part of hiatus
semilunaris
Maxillary sinus – Opens into
the posterior part of hiatus
semilunaris
Anterior and middle ethmoidal
cells – Opens into the upper
margin bulla ethmoidalis

18. SINUSES

19. Air containing cavity in certain skull bones
Develop as a diverticula/outpouching from the lat wall of nose
& extend into Maxilla, Ethmoid, sphenoid and frontal bones
Four sinuses – Maxillary, Frontal, Ethmoid (Ant & Post) & Sphenoid
Some sinuses are well developed & asymmetrical

20. Each sinuses have
orifices that open into
the meatus, covered
by turbinates

23. Clinically
- two
groups
Anterior –
Frontal,
Maxillary, Ant.
Ethmoidal
Posterior –
Post Ethmoidal,
Sphenoid

24. 


Significance
Lighten the skull & facial bones
Contributes to vocal resonance
Collapsible framework that helps the brain to protect from blunt
trauma
EPITHELIUM
They are lined by mucosa similar to that of the nasal cavity –
pseudo
stratified ciliated columnar epithelium
Epithelium contains – Mucinous & serous glands
Mucoperiosteum

26. Sinuse
s
Status at
Birth
First
Radiologica
l evidence
Reaches
Adult
size by
Maxillary
sinus
Present at
birth
4-5 months
after birth
15
years
Ethmoid
sinus
Present at
birth
1
year
12
years
Sphenoid
sinus
Not
Present
4
years
15 years
– adult
age
Frontal
Sinus
Not
Present
6
years
Size
increases
until teens

28. Largest paranasal sinus
Pyramidal in shape
Base - towards lateral wall of nose
Apex – towards zygomatic process of
maxilla

29. Present at birth as a rudimentary sinus
First radiological evidence is at 4-5 months after
birth
Reaches adult size by 15 years
On average, it has capacity
of 14.75 ml (14-15)

30. • Facial surface of maxilla and
cheekAnt wall
• Infra temporal & pterygopalatine
fossa
Post wall
• Middle & inferior meatuses (this
wall is thin & membranous)
Med wall
• Floor of
orbitsRoof
• Alveolar part of
maxillaFloor

32. 




DRAINAGE – OSTIUM
Seen high up in the medial wall
Does not open directly into the nasal cavity, but opens into post.
part of ethmoidal infundibulum, via hiatus semilunaris into middle
meatus.
The infundibulum is the air passage that connects the maxillary
sinus ostium to the middle meatus.
Unfavourable for natural sinus drinage
Accessory ostium – 30 % cases

33. Arterial supply – Maxillary
artery, infra orbital, facial &
greater palatine
Venous supply – anteriorly
by facial vein & post.by
maxillary vein
Nerve supply – infra orbital,
anterior, middle & posterior
superior alveolar nerves
Lymph nodes – cervical nodes
& submandibular nodes

35. Situated between the outer & inner table of frontal
bone
Funnel shaped
Two sinuses on either side
Asymmetrical
Intervening bony septum which may be thin or
deficiency

36. Not present at birth
First radiological evidence is at 6 years
Reaches adult size after puberty
The natural frontal sinus ostium is usually located in the
posteromedial floor of the sinus (most dependent part).
It opens into the middle meatus
The ethmoidal infundibulum can act as a channel for carrying the
secretions (and infection) from the frontal sinus to anterior
ethmoid cells and the maxillary sinus or vice versa.

38. They develop from a variable site, their drainage will be
either via an ostium into the frontal recess or via a
nasofrontal duct into the anterior infundibulum. The
opening or duct can be distorted by expansion of adjacent
ethmoid cells
Boundaries
Ant wall – Skin over the forehead
Post wall - Meninges & the frontal lobe of brain
Inferior wall - orbit & its contents

39. FRONTAL RECESS
The frontal recess is an
hourglass like narrowing
between the frontal sinus and
the anterior middle meatus
through which the frontal sinus
drains. It is not a tubular
structure, as the term
nasofrontal duct might imply,
and therefore the term recess is
preferred.

40. The frontal recesses are
the narrowest anterior air
channels and are common
sites of inflammation. Their
obstruction subsequently
results in loss of ventilation
and mucociliary clearance
of the frontal sinus

41. AGGER NASI CELL
Anterior, lateral, and inferior to the frontal recess is the
agger nasi cell. It is aerated and represents the most
anterior ethmoid air cell, usually lying deep to the lacrimal
bone.
It usually borders the primary ostium or floor of the frontal
sinus, and thus its size may directly influence the patency
of the frontal recess and the anterior middle meatus.

43. The frontal sinus can pneumatize both the vertical and the
horizontal (orbital) plates of the frontal bone. The deepest
area of the vertical portion of the sinus is near the midline at
the level of the supraorbital ridge, and the medial sinus floor
and the caudal anterior sinus wall are thinnest in this area. As
a result, the sinus is best approached for a trephination at
this level

44. There is a rich sinus venous plexus (Breschet’s canals)
that communicates with both the diploic veins and the
dural spaces.
Arterial supply – supra orbital & supra trochlear
Venous supply – superior opthalmic vein
Lymph – Submandibular lymph node
Sensory innervation – supra orbital & supra trochlear

45. Occupies the body of sphenoid
Right & left, seperated by a thin strip
of bony septum (like frontal sinus)
Ostium opens into spheno
ethmoidal
recess
Relations of the sinus are very
important, esp during the surgical
approach of pituitary gland

47. 



Relations –
Anterior part –
Roof – olfactory tract, optic chiasma
& frontal lobe
Lateral – optic nerve, internal carotid
artery & maxillary nerve
Posterior part
Roof – Pituitary gland in sella turcica
Lateral – Cavernous sinus,ICA &
Cranial nerves III, IV, VI & all divisions
of V

48. Thin strips of bone separate the
sphenoidal sinuses from the nasal
cavities below and hypophyseal fossa
above
The pituitary gland can be surgically
approached through the roof of the
nasal cavities by passing first through
the anteroinferior aspect of the
sphenoid bone and into the sphenoidal
sinuses and then through the top of the
sphenoid bone into the hypophyseal

49. Thin walled air cavities in the lateral masses of the ethmoid
bone
Varies from 3 – 18
Occupy the space between the upper third of the lateral
nasal wall and the medial wall of orbit
Clinically divided into anterior ethmoidal air cells & posterior
ethmoidal air cells, by basal lamella (lateral attachment of
middle turbinate to lamina papyracea)
ETHMOID SINUS

51. DRAINAGE:
•
Anterior - a recess of hiatus semilunaris &
middle meatus via ehmoid bulla
Post- sup.meatus & spenethmoidal recess.
Present at birth
Reaches adult size by 12 years
First radiological evidence seen at 1 year

52. Relations
Roof – formed by the anterior cranial fossa
Lateral wall - orbit
Medial wall – nasal cavity
Thin paper like bony part of the ethmoid separating the air cells
from the orbit, called lamina papyracea, can be easily destroyed
leading to spread of ethmoidal infections into the orbit
Optic nerve forms a close relationship with the posterior
ethmoidal cells & is at risk during ethmoidal surgery

53. The osteomeatal complex is the key anatomic area
addressed by endoscopic sinus surgeons. Blockage of the
osteomeatal complex prevents effective mucociliary
clearance, thus leading to a stagnation of secretions and
therefore leading to recurrent or chronic sinusitis.

54. 



The OMC is bounded
medially by the middle
turbinate,
posteriorly and superiorly by
the basal lamella, and
laterally by the lamina
papyracea.
Inferiorly and anteriorly the
OMC is open.

55. 






This anatomic region
therefore includes
Maxillary sinus ostium
ethmoid bulla
frontal recess
uncinate process
infundibulum
hiatus semilunaris
middle meatus.

57. ANATOMICAL VARIENTS

58. IMPORTANT ANATOMIC
VARIATIONS OF PNS

59. Frontal Recess Cells
•
•
•
•
Variations in pneumatization of anterior ethmoid
air cells.
Broadly divided into anterior and posterior groups.
Anterior group: Agger nasi cells and frontal cells
Posterior group: supraorbital cells, frontal bullar
cells and suprabullar cells

60. Agger Nasi cell
•
•
Constant anteriormost
ethmoid cell seen in up
to 98% patients at CT.
Located anterior to
vertical attachment of
middle turbinate and is
best visualized on
sagittal and coronal CT
sections

61. Frontal Cells (Kuhn’s Cells)
•
•
•
•
•
Four types
Type-1: single anterior ethmoid air cell seen
above ANC
Type-2: two or more anterior ethmoid air cells
above ANC
Type-3: single large cell above ANC that bulges
into frontal sinus
Type-4: isolated air cell located completely within
frontal sinus, simulating a “cell within a cell”
appearance

62. Frontal Cells (Kuhn’s Cells)

63. Paradoxic Curvature
Normally, the convexity of the middle
turbinate bone is directed medially,
toward the nasal septum.
When paradoxically curved, the
convexity of the bone is directed laterally
toward the lateral sinus wall.
The inferior edge of the middle turbinate
may assume various shapes, which may
narrow and/or obstruct the nasal cavity,
infundibulum, and middle meatus.

64. Concha Bullosa
It is an aerated turbinate, most often the
middle
turbinate.
Less frequently, superior & inferior turbinate
aeration can occur.
When the pneumatization involves the
bulbous
segment of the middle turbinate, the term
concha bullosa applies.
If only the attachment portion of the middle
turbinate is pneumatized, and the
pneumatization does not extend into the
bulbous segment, it is known as a lamellar

65. Other Variations
Additional variations of the middle turbinate can occur, including
medial & lateral displacement, lateral bending, L shape, and sagittal
transverse clefts
Medial displacement – due to other middle meatal structures (i.e.,
polypoid disease, pneumatized uncinate process) encroaching
upon the middle turbinate.
Lateral displacement - due to the compression of the turbinate
toward the lateral nasal wall by a septal spur or septal deviation.

66. The nasal septum deviation
may compress the middle
turbinate laterally, narrowing
the middle meatus and the
presence of associated bony
spurs may further compromise
the OMU.
Obstruction, secondary
inflammation, swollen
membranes, and infection can
occur

67. DEVIATION
The course of the free edge of the uncinate process may
either
extend slightly obliquely toward the nasal septum, with the
free edge surrounding the inferoanterior surface of the
ethmoid bulla, or it extends more medially to the medial
surface of the ethmoid bulla. If the free edge of the uncinate
is deviated in a more lateral direction, it may cause narrowing
or obstruction of the hiatus semilunaris and infundibulum.

68. Attachment
Attachment to the lamina papyracea, the lateral surface of the
middle turbinate, or the fovea ethmoidalis in the floor of the
anterior cranial fossa may occur.
If the uncinate process attaches to the ethmoidal roof or
middle turbinate, during uncinatectomy, traction could
inadvertently damage the ethmoid roof and result in CSF
rhinorrhea or other intracranial complications.

70. Sometimes the free edge
of the uncinate process
adheres to the orbital floor,
or inferior aspect of the
lamina papyracea. This is
referred to as an
atelectatic uncinate
process

71. Pneumatization
The pneumatization of the uncinate
process is believed to be due to
extension of the agger nasi cell
within the anterosuperior portion of
the uncinate process.
Functionally, the pneumatized
uncinate process resembles a
concha
bullosa or an enlarged ethmoid bulla.

72. Infraorbital ethmoid cells are
pneumatized ethmoid air
cells that project along the
medial roof of the maxillary
sinus and the most inferior
portion of the lamina
papyracea, below the
ethmoid bulla and lateral to
the uncinate process

74. Two definitions of Onodi cells.
The first defines them as the most
posterior ethmoid cells, being
superolateral to the sphenoid sinus and
closely associated with the optic nerve.
Another, more general description
defines Onodi cells as posterior
ethmoid cells extending into the
sphenoid bone, situated either
adjacent to or impinging upon the
optic nerve

76. Its appearance varies considerably, based on the extent of
pneumatization.
Extensive pneumatization may obstruct the ostiomeatal
complex.
Elongated ethmoid bullae are usually in a superior to
inferior
direction rather than in an anterior to posterior direction.
So, Relatively unlikely to obstruct the ostiomeatal complex.

77. Encountered rarely
extends into the lesser
wing and the anterior and
posterior clinoid processes
Can lead to distortion of
optic cannal configuration

78. May be either congenital or the
result of prior facial trauma.
It occur most often at the site
of
the insertion of the basal
lamella into the lamina
papyracea, thus rendering this
portion of the lamina
papyracea most delicate
Orbit at risk

80. When aeration of the normally bony crista galli occurs the
aerated cells may communicate with the frontal recess, and
obstruction of this ostium.
To avoid unnecessary surgical extension into the anterior
cranial vault, it is important to recognize an aerated crista
galli and differentiate it from an ethmoid air cell.

81. Air cells are commonly found within the posterosuperior
portion of the nasal septum and, when present,
communicate with the sphenoid sinus.
As a result, any inflammatory disease that occurs within the
paranasal sinuses may also affect these cells

82. It is important to note any asymmetry in the height of
the ethmoid roof.
Intracranial penetration during surgery is more likely to
occur on the side where the position of the roof is lower

83. IMAGING MODALITIES

84. X RAY
CT
MRI

85. X ray – Water’s view & caldwell view
Ct – gold standard. Coronal & axial sections
MRI is predominantly used for pre and post operative
management of naso sinus malignancy
The chief disadvantage of MRI is its inability to show the
bony details of the sinuses, as both air and bone give no
signal

86. CT PROCEDURE & SECTIONS

87. CT is currently the modality of choice in the evaluation of
the paranasal sinuses and adjacent structures.
Its ability to optimally display bone, soft tissue, and air
provides an accurate depiction of both the anatomy and the
extent of disease in and around the paranasal sinuses.
In contrast to standard radiographs, CT clearly shows the
fine
bony anatomy of the osteomeatal channels.

88. 

There are few pre requisites in few situations
a course of adequate medical therapy to eliminate or
diminish reversible mucosal inflammation.
pretreatment with a sympathomimetic nasal spray 15
minutes prior to scanning in order to reduce nasal
congestion (mucosal edema) and thus improve the display
of the fine bony architecture and any irreversible mucosal
disease

89. Coronal & axial views
The coronal plane best shows the ostiomeatal unit (OMU),
shows the relationship of the brain to the ethmoid roof.
Coronal plane should be the primary imaging orientation
for evaluation of the sinonasal tract in all patients with
inflammatory sinus disease who are endoscopic surgical
candidates

92. Prone with chin hyperextended
Gantry anglutaion- perpendicular
to hard palate
Section thickness-3mm
contigous
Table increment- 3-4 mmeach
step
Kvp-125
Mas-80
Hanging head technique

95. HEAD HANGING METHOD
Performed in the prone position,
so that any remaining sinus
secretions do not obscure the
OMU
In patients who cannot tolerate
prone positioning (children,
patients of advanced age, etc.),
the hanging head technique can
sometimes be utilized.

96. In this technique, the patient is
placed in the supine position and
the neck is maximally extended.
A pillow placed under the patient’s
shoulders facilitates positioning.
The CT gantry is then angled to be
perpendicular to the hard palate.
It is not always possible to obtain
true direct coronal images with this
technique

97. Axial images complement the coronal study, particularly
when there is severe disease (opacification) of any of the
paranasal sinuses and surgical treatment is contemplated.
The axial studies provide the best CT evaluation of the
anterior and posterior sinus walls
Axial images are particularly important in visualizing the
frontoethmoid junction and the sphenoethmoid recess.

98. CT axial section of
PNS
- image

99. Whenever there is total opacification of the frontal, maxillary, or
sphenoid sinuses, a complete axial and coronal CT
examination should be performed.
And also, if the patient has a suspected neoplasm, a complete
axial and coronal examination need to be performed to provide
the most detailed analysis of the sinonasal cavities and the
adjacent skull base

100. IMAGING PLANE :
REIDS’S LINE – runs b/w infraorbital margin (IOM line)
& EAM. (parallel - axial)
ALEXANDER’S LINE – perpendicular to reids line.
(perpendicular - coronal)

103. Contrast is not required for all cases of CT paranasal
sinus
Used in cases such as vascular lesion, malignancy,
mass
extending intra cranially, acute infections