1. IMAGING OF PARANASAL SINUSES
PRADEEP KUMAR

2. Anatomy
• PNS are extensions of air filled nasal cavities.
• During fetal development, the paranasal sinuses originate as invagination
of the nasal mucosa into the lateral nasal wall.
• Two groups:
Anterior- frontal, maxillary, anterior ethmoid
Posterior- posterior ethmoid and sphenoid
• Lighten the skull and add resonance to the voice

5. FRONTAL SINUS
• Each frontal sinus begins during the fourth
month of fetal life in the regions of the frontal
recess.
• At birth, they are indistinguishable from the
anterior ethmoid cells. Postnatal growth is slow.
Visible after the first or second year of life and
are well-developed by 7-8 years but reach their
full size only after puberty.
• They are larger in males.
• Each frontal sinus opens into the anterior part
of the corresponding middle meatus of the nose
through the frontonasal duct (frontonasal
recess).

6. SPHENOID SINUS
• It occupies the body of the sphenoid.
The two sinus, right and left are rarely
symmetrical and are separated by a thin
bony septum.
• Ostium of the sphenoid sinus is situated
high up in the anterior wall and opens
into the sphenoethmoid recess, medial
to the supreme or superior turbinate.

7. <1%→ sphenoid sinus does not reach ant
wall of sella (transsphenoidal
hypophysectomy not possible)
RELATIONS OF SPHENOID SINUS

8. ETHMOIDAL SINUS
• They are thin walled air cavities in the lateral
masses of the ethmoid bone. Their number
varies from 3-18.
• They occupy the space between upper third of
lateral nasal wall and the medial wall of orbit.
• Clinically, they are divided by the basal lamina
into an anterior ethmoid group that opens
into the middle meatus and the posterior
ethmoid group that opens into the superior
meatus.

10. • Facial surface of maxilla and cheekANT
WALL
• Infra temporal & pterygopalatine
fossaPost wall
• Middle & inferior meatuses (this
wall is thin & membranous)Med wall
• Floor of orbits
Roof
• Alveolar part of maxillaFloor

12. DRAINAGE PATHWAYS OF THE PARANASAL
SINUSES
Paranasal sinuses are broadly divided into two major groups: the
anterior sinuses and the posterior sinuses. The anterior sinuses comprise the
frontal sinus, anterior ethmoid air cells, and maxillary sinus.
These drain into a common area centered in the middle meatus, the
osteomeatal unit (OMU). The posterior sinuses are the posterior
ethmoid air cells and the sphenoid sinuses. These drain into the
sphenoethmoid recess.

13.  Osteomeatal Unit. The OMU is the common drainage pathway
of the anterior sinuses, the key area in the pathophysiology of
chronic sinusitis and the center of interest since the advent of
FESS.

14. OSTIOMEATAL UNIT
◻ Region where frontal, anterior
& middle ethmoid & maxillary sinuses drain.
▪ Hiatus semilunaris (oval)
▪ Uncinate process (arrowhead)
▪ Ethmoid bulla (arrow)
▪ Infundibulum (dotted line)
▪ Frontal recess,
▪ Maxillary ostium
▪ Middle meatus
◻ Coronal plane:
▪ best for assessing the OM unit

15. IMPORTANT ANATOMIC VARIATIONS
 Frontal Recess Cells
 Onodi Cell (Sphenoethmoid Cell)
 Haller Cell (Orbitomaxillary Or Infraorbital
Ethmoid Cell)
 Uncinate Process Variations
 Nasal Septal Variations
 Middle Turbinate Variations
 Variations of the Ethmoid Roof
 Variations Related to Sphenoid Sinus

16. 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

17. 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

21. ONODI CELL (SPHENOETHMOID CELL)
 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

23. HALLER CELL
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
Clinical significance –
 Become infected , with potential
extension into orbit.
 Narrows the maxillary ostium

24. UNCINATE PROCESS
VARIATIONS
• Type I uncinate process is the
commonest type and attaches to the
lamina papyracea, separating the
ethmoidal infundibulum and the frontal
recess
• Type II uncinate attaches to the skull
base, and type III turns medially and
attaches to middle turbinate
• In type II and III uncinate processes,
the frontal recess opens into the
ethmoid infundibulum.

26.  DEVIATION
 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
 Uncinate bulla

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

28. MIDDLE TURBINATE VARIATIONS
 Paradoxic Curvature
 Concha Bullosa
 Additional variations of the middle
turbinate can occur, including
medial & lateral displacement,
lateral bending, L shape, and
sagittal transverse clefts

29. VARIATIONS OF THE ETHMOID ROOF
 Kero’s classiication describes three types of
ethmoid roofs, depending on the depth of the
olfactory fossa, determined by measuring the
height of the lateral lamella of the cribriform
plate.
 Type I ethmoid roof has a depth of 1 to 3 mm
 Type II a depth of 4 to 7 mm
 Type III a depth of 8 to 16 mm . Type III is
associated with more potential damage from
iatrogenic injury.

30. VARIATIONS RELATED TO SPHENOID
SINUS
Type I OC is the commonest type and runs
immediately adjacent to the sphenoid sinus,
without indentation of the wall or contact with
posterior ethmoid air cell.
Type II OC courses like the type I but indents the
sphenoid sinus wall.
Type III OC runs through the sphenoid sinus, with
at least 50% of the nerve being surrounded by air
Type IV OC lies immediately adjacent to the
sphenoid sinus and the posterior ethmoid air cells

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

32. X RAYS
• Lateral view
• Caldwell View( PA Axial)
• Water’s View (Occipitomental view or nose
chin position)

34. Role of CT and MRI
CT:
• Coronal +/- axial sections
✓ Anatomic landmarks and variants
✓ Requested when inflammatory or neoplastic processes suspected
& suspected inflammatory is not responding to conservative
therapy
✓ Identify erosive processes & acquired developmental deficiencies
of bone.
✓ Intraorbital extension of sinonasal disease in ventral 2/3 of the orbit

35. • The real value of unenhanced CT is the following: if you see an
opacified sinus with hyperdense contents, it is usually a sign of
benign disease. Tumor is not hyper-dense.
The hyperdensity is due to one or a combination of the following:
• inspissated secretions
• fungus
• blood

36. MRI:
▪ T1 & T2WI axial & coronal
▪ +/- Sag or off-sag parallel to optic nerve
▪ +/- Gd enhanced
▪ Extension into orbit & cranial cavity
▪ Invasion of skull base (replacement of high signal of
fatty marrow on T1WI by low signal of tumor)
▪ Foraminal extension, whether by perineural spread
or direct invasion of the tumor.

37. Signal characteristics of secretions
 Depends on the ratio of water to
protein and the viscosity.
 Fungus usually has a high protein
content of more than 28% and can
mimic an aerated sinus because it is
low on T1- and T2WI.
 You need CT to make the distinction!

38. Enhancement
• In general bright signal on T2 is a sign of
benign disease, since fluid and mucosal
disease usually have a high water content.
Secretions do not have solid enhancement.
If you have an enhancing mass, you must rule
out tumor.
Page 38

39. Pathology: Inflammatory
• Sinusitis
• Polyp
• Cyst
• Mucocele
• Fungal dis
• Granulomatous dis

40. Acute Sinusitis
• Most common sinus involved is maxillary sinus followed by ethmoid, frontal and
sphenoid.
• Duration is 4 weeks or less.
• Organism most commonly involved are Strept. Pneumoniae, H.influenza,
Moraxella catarrhalis….etc
• Viral URTI→ secondary bacterial infections
• X ray:
Fluid level: Hallmark of acute bacterial sinusitis; most commonly seen in
maxillary sinus
• Total loss of translucence in affected sinus

41. Demonstration of air fluid level in acute maxillary sinusitis
If doubt: tilted view (few moments later for viscid fluid to asssume new level)→ new
horizontal level

44. Chronic sinusitis
▪ Following acute infection
▪ Infection as Tuberculosis or Actinomycosis
▪ Mucosal thickening (no fluid level unless acute exacerbation)
▪ Patterns of Chronic sinusitis: Sonkens et al (importance of ant & post
draining pathway)
1. Infundibular pattern- limited to maxillary sinus & infundibulum .
Cause- polyp/mucosal thickening in that location or haller cells.
2. OMU pattern- obstruction in MM produce changes in frontal ,
ant. ethmoid & maxillary sinus. Cause- mucosal thickening,
polyp, choncha bullosa, deviated septum or nasal tumour

45. 3. Sphenoethmoidal recess pattern- Sphenoethmoid recess is
blocked & changes seen in ipsilateral sphenoid & posterior
ethmoid cell.
4. Sinonasal polyposis- both nasal cavities & sinuses are filled with
polyps & resultant chr inflammatory changes are mixture of above
3 patterns.
5. Sporadic /unclassified pattern- when no specific kind of obstr. is
seen & when mucocele ,retention cyst or postoperative changes
seen.

49. Allergic sinusitis
• Difficult to distinguish from infective sinusitis
• Even two coexist
Allergic sinusitis Bacterial sinusitis
Symmetrical sinus involvement Isolated or contiguous sinus
involvement
Turbinate thickening is characteristic Air fluid level (hallmark of acute
bacterial sinusitis)
Mucosa polypoid with convex inner
border
Mucosa follows contour of and is
parallel to wall of sinus
Nasal polyp associated Rarely

50. SILENT SINUS SYNDROME

52. Complications of sinusitis
• When assessing the complications of sinusitis, CT is excellent
for imaging of subperiostial abscesses or orbital extension into
the ventral 2/3 of the orbit.
• MRI is necessary for assessing intracranial complications, such
as brain or epidural abscesses, subdural empyema or sinus
thrombosis.

53. Orbital
• 1. Edema
• 2. Preseptal cellulitis
• 3. Postseptal cellulitis
• 4. Subperiosteal abscess
• 5. Orbital abscess
• 6. Cavernous sinus
thrombosis
Subgaleal
• 1. Pott’s puffy tumor
• 2. Osteomyelitis
Intracranial
• 1.Epidural empyema
• 2.Subdural empyema
• 3.Meningitis
• 4.Cerebritis
• 5. Parenchymal abscess
• 6.Mycotic aneurysm
• 7.Brain infarction
Complications of sinusitis:

55. POTT PUFFY TUMOR

58. Polyp
• Pedunculated section of edematous upper
respiratory mucosa; well defined dome shaped
homogenous lesions
• Commonest site of origin: ethmoid air cell
mucosa; much less common in maxillary
antrum
• Findings s/o nasal polyposis:
✓ BILATERAL homogenous rounded masses
within nasal cavities,
✓ +/- expanded sinuses/ part of nasal cavity,
✓ enlargement of sinus ostia,
✓ thinning of bony trabeculae

59. Antrochoanal polyp
▪ Unilateral polyp→ unilateral nasal blockade
▪ Arises in maxillary antrum, passes out
through ostium which it enlarges→ pass
posteriorly through choana
▪ Radiological hallmark is the enlarged
ostium
▪ DDx: Inverted papilloma
Juvenile angiofibroma
Retention cyst
▪occurs due to obstruction of duct of gland of
mucosa
▪indistinguishable from polyp on CT & MRI.

62. Mucoceles
• Obstruction of sinus ostium→ If infection
does not supervene, sinus fills with mucus→
mucus acts then as a slow-growing mass
lesion→ expands sinus & thins sinus wall→
remodelling of bony margins
• Commonest sinus involved
-frontal sinus-60%, ethmoidal sinus-25%,
maxillary sinus-10%
• symptoms usu d/t mass effect as:
✓ Post ethmoid mucocoeles→ encroach upon
optic nerve→ visual failure.
✓ Frontal/ ant ethmoid mucocoeles→ extend
orbit→ proptosis.
• Pain is rare but may occur if infected –
mucopyocele
• Prone to recurrence→ thus all loculi be
drained adequately

63. X ray:
◻ Expanded sinus with LOSS OF
SCALLOPED MARGIN (when vertical
section is involved; not seen if only
horizontal part is expanded as in 25%-
can be easily missed)
◻ Depression or erosion of supraorbital
ridge
◻ Extension across midline through
septum to opposite frontal sinus
◻ Loss of translucence.

64. CT:
• expanded sinus with intact wall filled
with homogenous material of low
attenuation (15HU)
• Ring enh after IV contrast→ Pyocele

65. MR:
• T1W- isointense to soft tissue such as
brain
• T2W- increased signal intensity due to
high water content
• Peripheral rim enhancement in C+ MRI
• Signal changes if infected or contain blood
break down products

66. Fungal disease
• Most common fungi :
✓ Mucormycosis
✓ histoplasmosis
✓ candidiasis
✓ Aspergillosis
• Types of fungal sinusitis:
✓ non-invasive: hyphae do not invade mucosa: mycetoma,
allergic
✓ Invasive: hyphae seen invading mucosa +/- beyond:
acute, chronic, chronic granulomatous
• Radiographic features: non specific
• Opacification of sinus and sclerotic bony reaction
• bony destruction- may mimic squamous cell carcinoma

67. Mucormycosis:
-exclusively in immunocompromised,
(50-75% uncontrolled DM)
-invasive, tend to spread from nasal
cavity to PNS
-invade blood vessels, denude the
endothelial lining and initiate
thrombosis- leads to venous cerebral
infarcts
-Invasion of orbits, C. sinuses,
ophthalmic veins is common
-intracranial extension via emissary
veins may extend to meninges and
cause cerebral abscess
-Progression rapid within few days
-Bind Ca, Mn & heavy metals→
hyperdense on CT & low SI on MR
Cavernous sinus thrombosis or
thrombophlebitis:
✓ most often secondary to sinus infection
✓ opacification of lt posterior ethmoid and
sphenoid sinus
✓ secondary enlargement & enhancement
of left cavernous sinus & optic nerve

69. The CT clearly shows the opacified sinus, which is slightly hyperdense.
The signal characteristics on MRI and the attentuation on CT are a result of the
high protein content of fungus.
This is a good example of the pitfall of the 'pseudo-pneumatized sinus' .

70. Granulomatous disease
• Etiology:
✓ Organisms: Nocardia, aspergillosis,
actinomycosis, tuberculosis and syphilis.
✓ Autoimmune: Wegener’s
granulomatosis, sarcoidosis
✓ Irritant exposure: Be, Chromium
• Nonspecific inflammatory rxn with
mucosal thickening & increased
secretion
• Nasal septum thickening and septal
erosions
• Bony changes of nasal cavity and PNS
may include thickened and sclerotic
walls and septa
Wegener's granulomatosis.
Granulomatous disease within the
paranasal sinuses may be
manifested as linear enhancement
(arrow) or nodule enhancement.
Destruction of osseous structures
out of proportion to soft tissue
thickening should lead one to think
of a granulomatous process or
lymphoma.

71. Pathology: Tumours
• Neoplastic:
✓ Papilloma
✓ Carcinoma
✓ Olfactory neuroblastoma
✓ Lymphoma
• Benign:
✓ Angiofibroma
✓ Neurogenic: Schwannoma, neurofibroma
✓ Fibroosseous: osteoma, fibrous dysplasia, ossifying
fibroma, GCT, odontogenic tumor,

72. • Polypoid lesions with irregular verrucose surface
• Imp to DD from cyst/polyp→ malignant degeneration in
papilloma
• Types: (Imp to DD these two papillomas)
✓ Fungiform papilloma (50%)- from nasal septum, solitary,
unilateral, non premalignant
✓ Inverted or endophytic papilloma (50%)- from lateral nasal wall,
premalignant (15%), presents as a unilateral nasal polyp with
non-specific symptoms like nasal congestion or epistaxis
Papilloma

73. •Inversion of neoplastic epithelium into underlying stroma
•Arises from lateral nasal wall centered at middle meatus ± extension into
antrum
•CT findings
– 40% show "entrapped bone"
– Focal hyperostosis of adjacent bone may indicate point of tumor
attachment
– Thinned or eroded bony wall
Inverted papilloma:

74. MR FINDINGS
– T2: Predominantly hyperintense to skeletal muscle
– T2 & T1C+: Curvilinear striations or "convoluted, cerebriform pattern" is
distinctive
– If portion of tumor appears invasive or necrosis present→ consider synchronous
SCCa
•Biopsy is necessary to make the diagnosis and because more than 10% of inverted
papillomas harbor a squamous cell carcinoma.

76.  Looking at the pre-contrast study, contents of the
ethmoidal and maxillary sinuses are hyperintense
as opposed to the mass in the nasal cavity (the
middle meatal region), because the sinuses are
filled with inspissated secretions.
 This solidly enhancing mass is a tumor until proven
otherwise.
 The imaging findings are non-specific and the
differential diagnosis includes a polyp or a
carcinoma.
 Biopsy revealed an inverted papilloma

78. Squamous cell carcinoma
• Most common malignancy of sinonasal area
• Risk factors: Inhaled wood dust, metallic
particles, chemicals, HPV, inverted papilloma
• Symptoms mimic chronic sinusitis & delay
diagnosis
• Age: 50-70 years
• M>F
• 75% arise in sinuses; ≈ 30% arise primarily in
nose
• Maxillary antrum (85%), ethmoid (10%),
frontal/sphenoid (< 5%)
• 15% maxillary sinus SCCa have malignant
adenopathy
• Combined surgery & XRT most common
treatment
• Overall 5-year survival:25-30%
• Local recurrence common

79. CT:
CECT
•Solid, moderately heterogenously enhancing mass
with aggressive bone destruction (Propensity to
destroy bone in presence of relatively small
demonstrable mass)
•Nonenhancing areas may represent necrosis

80. •T1WI: Intermediate signal
mass, similar to muscle signal;
Areas of intratumoral
hemorrhag→ ↑ T1 signal
•T2WI: Intermediate to high
signal compared to muscle but
lower than other sinonasal
malignancies.
•T1WI C+: Enhancement
typically mild to moderate;
diffuse, but heterogeneous:
Enhances to lesser
degree than adenocarcinoma,
esthesioneuroblastoma,
melanoma
MR:

84. Adenoid cystic carcinoma:
• Glandular in origin i.e. from minor salivary glands
• Tend to recur
• perineural spread & leaves normal skip areas
between primary lesion & local metastatic site
along a nerve

85. Olfactory neuroblastoma
• Aka esthesioneuroblastoma
• Origin: olfactory mucosal neural crest cell
• Bimodal: 2nd & 6th decades
• Intracranial extension through cribriform plate (25-30% at dx)
• CT: lobulated; relatively slow growing: bony margins often
remodelled & resorbed, rather than being aggressively
destroyed

86. • MR: heterogenous SI in T1 & T2;
When intracranial extension is
present, peritumoural cysts
between it & overlying brain are
often present. This may be helpful
in distinguishing it from other
entities.
• Attention be paid to presence of
cervical & retropharyngeal nodal
metastases
• Rx: Cranifacial resection (cure 90%)

87. Lymphoma
• Most are NHL
• Commonest site: nasal cavity and
maxillary sinus
• Imp to differentiate from SCC: distinct
clinical course & marked radiosensitivity
• Tend to be bulky soft tissue mass that
enhance following gadolinium inj; tend to
remodel bone and occasionally erode
bone rather than destroying

88. Opacified sinus with bone destruction
Inflammatory
Fungal infection Mucormycosis
Aspergillosis
Granulomatous disease Wegeners granulomatosis
Midline destructive granuloma
Neoplastic
Benign Inverted papilloma
Juvenile angiofibroma
Malignant Squamous cell carcinoma
Adenoid cyst/ adenocarcinoma
lymphoma
Metastasis

89. Benign, slowly growing tumors containing mature
compact or cancellous bone
frontal sinus (80%)→ethmoid (15%) and maxillary (5%)
usu asymptomatic (incidental)
May block sinus→ recurrent infection & mucocele
Erode skull→ CSF leak
Multiple osteomas in skull & mandible: Gardner’s syn
Osteoma
3 types:
✓ Ivory osteoma: commonest, dense; CT: well circumscribed very dense
mass; MR: low SI in all sequences
✓ Mature osteoma: normal bone, marrow; CT: ground glass appearance;
MR: some marrow SI
✓ Mixed osteoma:

90. Juvenile nasopharyngeal angiofibroma
• Highly vascular, non-encapsulated
polypoid mass
• Histologically benign but highly
aggressive
• Occurs exclusively in males in 2nd
decade
• Et: Hormonal theory (♂)
• Presents with nasal obstruction and
epistaxis, facial deformity and
proptosis
• Biopsy is contraindicated

91. • Origin: sphenopalatine foramen
• Route of spread:
• Medial: nasal cavity, nasopharynx
• Lateral: pterygopalatine fossa (superiorly thru IOF→ orbit),
infratemporal fossa (superiorly into pituitary, Cavernous sinus
thrombosis)

92. • Widening of sphenopalatine foramen
• Involvement of pterygopalatine fossa seen in
90% (“Dumb-bell”)
• Asymmetry in size or widening of this
structure
• Absence of normal fat plane betn pterygoid
plate and back of maxillary sinus
• Anterior bowing of post wall of antrum-
‘Holman-Miller’ sign
• Widening of pterygomaxillary fissure

93. • Homogenous enhancement after IV Contrast
• MR:
T1WI: Heterogenous intermediate SI with flow
voids s/o enlarged vessels; intense enh with
Gd
T2WI: heterogenous inter to high SI
• Angiogram: to demonstrate feeding artery-
internal maxillary and ascending
pharyngeal artery and for embolization
before surgery

94. Radkowski JNA Staging