CT ANATOMY OF PARA NASAL SINUSES Normal anatomy & anatomical variations of PNS in CT are discussed in detail...

1. By
Dr.K.PRASANNA
Radiology Resident
RMMCH

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

3. NOSE AND NASAL FOSSA

4.  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

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

7.  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

8.  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
 Inferior conchae

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

10.  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

12. 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

15.  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
infundibulum

16.  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

19. SINUSES

20.  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

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

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

25.  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

27. Sinuses Status at
Birth
First
Radiological
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

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

30.  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)

31. • Facial surface of maxilla and cheek Ant wall
• Infra temporal & pterygopalatine
fossa Post wall
• Middle & inferior meatuses (this
wall is thin & membranous) Med wall
• Floor of orbits Roof
• Alveolar part of maxilla Floor

33.  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

34.  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

36.  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

37.  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.

39.  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

40.  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.

41.  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

42.  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.

44.  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

45.  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

46.  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

48.  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

49.  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 fossa

50.  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)

52.  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

53. 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

54. OSTEOMEATAL COMPLEX

55.  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.

56.  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.

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

59. ANATOMICAL
VARIANTS

60.  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.

61.  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
concha.

62.  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.

63.  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

64.  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.

65.  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.

67.  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

68.  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.

69.  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

71.  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

73.  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.

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

75.  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

77.  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.

78.  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

79.  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

80. IMAGING MODALITIES

81.  X RAY
 CT
 MRI

82.  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

83. CT PROCEDURE &
SECTIONS

84.  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.

85.  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

86.  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

89.  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

92.  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.

93.  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

94.  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.

95.  CT axial section of PNS
- image

96.  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

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

98.  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

100. AGE OF THE PATIENT

104. X RAY SHOULDER JOINT
BY
DR.V.PRIYA
ON SATURDAY