Paranasal sinus anatomy, normal variants and pathology in a nut shell......Includes almost everything about PNS....sinusitis, tumors,

1. Paranasal sinuses
Presented by: Dr. Bharath Jain
1st year radiology PG
SSIMS& RC

2. Nasal cavity
 Nasal cavity extends from the palate to the skull base and is
divided by nasal septum.
 It opens posteriorly via choana in to nasopharynx.
 Nasal septum comprises the septal cartilage anteriorly and
perpendicular plate of ethmoid and vomer posteriorly.

3. Sinuses
 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.
 Each sinuses have orifices that open into the meatus, covered
by turbinates.

5. Sinuses Status at birth 1st radiological
evidence
Adult size
reached at
Maxillary sinus Present at birth 4-5 months after
birth
15years
Ethmoid sinus Present at birth 1year 15years
Sphenoid sinus Not present 4year 12years
Frontal sinus Not present 6year 18-19years

7. Frontal sinuses.

9. 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
 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

11. Maxillary sinus
 It’s the first sinus to form and is hypoplastic in 10% of people.
 The roof forms the orbital floor and floor is formed by the
maxillary alveolus.
 Its medial wall forms the lateral wall of nasal cavity.
 Its drains in to middle meatus via the infundibulum.

13. Osteomeatal unit:
 It drains the frontal, anterior ethmoid and maxillary sinuses.
 It includes maxillary sinus ostium, ethmoid infundibulum,
hiatus semilunaris and frontal recess.
 It is best demonstrated on coronal CT.

14.  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.

17. Sphenoid sinus
 Sphenoid sinus develops in the body of the sphenoid sinus and
drains via a sinus ostium into spheno ethmoid recess.
 The degree of pneumatisation is variable and may extend into
greater and lesser wing of sphenoid and pterygoid plates.
 There are many important structures in relation to sphenoid
sinus like vidian canal, optic nerve and foramen rotundum.

21. Ethmoid air cells
 Thin walled air cavities in the lateral masses of the ethmoid
bone. Varies from 3 – 18 in number.
 Clinically divided into anterior ethmoidal air cells & posterior
ethmoidal air cells, by basal lamella (lateral attachment of
middle turbinate to lamina papyracea)
 Anterior drain into- Middle meatus.
 Posterior- sup.meatus & spenethmoidal recess.

23. Anatomical variants

24. 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.

27. Concha Bullosa
 It is an aerated turbinate, most often the middle turbinate.
 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 pneumatisation does not extend into
the bulbous segment, it is known as a lamellar concha.

29. Agger Nasi Air Cell
 Its an ethmoturbinal remnant present in nearly all patients.
 Located anterior to the vertical attachment of the middle
turbinate to the skull base.
 The degree of ANC pneumatization varies and has a significant
effect on both the size of the frontal sinus ostium and the shape
of the recess.

31. Fronto-ethmoid/kunh cells/bulla frontalis
 Are the anterior ethmoid cells which invade the
frontal bone, bulging its floor.
 They are more easily demonstrated at sagittal view, where
they appear as ethmoid air cells located above the ethmoid
bulla and as an extension towards the frontal sinus.
 Depending on their size and pneumatization extent, such
cells may affect the frontal sinus drainage.

32.  These air cells, are categorized into four types depending
on their number and degree of extension into the frontal
sinus.
 They are all located superior to the ANC.

33.  Type 1 (most common): Single cell superior to the ANC that
does not extend into the frontal sinus
 Type 2: Two or more cells superior to the ANC that may or
may not extend into the frontal sinus.
 Type 3: Single frontal cell superior to the ANC that extends
into the frontal sinus.
 Type 4: Completely contained in the frontal sinus. This
configuration is rare.

35. Haller cell
 These are ethmoid air cells located anterior to the
ethmoid bulla, along the orbital floor, adjacent to the
natural ostium of the maxillary sinus, which may
cause mucociliary drainage obstruction, predisposing
to the development of sinusitis.

37. Sphenoethmoid cell (Onodi cell)
 This is formed by lateral and posterior pneumatization of the
most posterior ethmoid cells over the sphenoid sinus.
 The presence of Onodi cells increases the chance that the optic
nerve and / or carotid artery would be exposed in the
pneumatized cell.

39. Accessory maxillary ostia
 Accessory maxillary ostia are generally solitary, but
occasionally may be multiple.
 Such variation may be congenital or secondary to sinusal
diseases.
 Possible mechanisms involved in the development of such
variation include:
 main ostium obstruction, maxillary sinusitis or
anatomical/pathological factors in the middle meatus, resulting
in rupture of membranous areas.

42. Variations in uncinate process

46. Imaging modalities

47.  X RAY
 CT
 MRI

48.  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.

49. Parietoacanthial projection: waters view

50.  Part Position:
 Extend neck, placing chin and nose against table/upright Bucky surface.
 Head is adjusted so as to bring the orbito meatal line to a 45 degree
angle to the casette holder.
 Position the median saggital plane is perpendicular to the midline of
grid or table/upright bucky surface.
 Ensure that no rotation or tilt exists.
 Centering is done at acanthion.

51. Waters view

53. Caldwell
Part Position:
 Place patient's nose and forehead against upright Bucky or
table with neck extended to elevate the OML 15° from
horizontal. A radiolucent support between forehead and
upright Bucky or table may be used to maintain this
position.(alternate method if Bucky can be tilted 15°.)
 Align MSP perpendicular to midline of grid or upright
Bucky surface.
 Centering is done at nasion, ensuring no rotation.

54. PA PROJECTION: SINUSES Caldwell Method

55. 1

56. Parietoacanthial transoral projection: Open Mouth
Waters Method

57. CT procedures and techniques
 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.

58.  SCAN LIMITS :
From the ant margin of
frontal sinus to post
margin of sphenoid sinus

59. Coronal section procedure

60. Axial plane
 Axial images complement the coronal study, particularly
when there is severe disease (opacification) of any of the
paranasal sinuses and surgical treatment is contemplated.
 Axial images are particularly important in visualizing the
frontoethmoid junction and the sphenoethmoid recess.

61. Contrast CT
 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.

62.  MRI is helpful in knowing intrcranial or intraorbital
extension.

63.  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

64. Sinusitis
 Sinusitis is the inflammatory condition of the mucous
membrane lining of the sinuses. It may progress to
pus formation.
 Sinusitis may be acute and chronic.

65. Sinusitis may divided into:
 Rhinogenous – infection spreads from the nasal cavity. It is the most
common way for infection and such sinusitis is the complication of
the flu.
 Odontogenic – infection spreads from upper teeth. This way is
typical only for maxillary sinus. The pathologic process may spreads
from 4,5,6 cheek-teeth apex to the inferior wall of the maxillary
sinus
 Traumatic
 Hematogenic
 Allergic.

66. Acute sinusitis
 It is an acute inflammation of the nasal and paranasal sinus
mucosa that last less than four weeks and can occur in any of
the paranasal sinuses.
 It usually follows viral infection.
 X-ray:Opacification of the sinuses and air/fluid level best seen
in maxillary sinus.

67. CT
 Better anatomical delineation and assessment of inflammation
extension, causes and complications. Peripheral mucosal
thickening, air/fluid level, air bubbles within the fluid and
obstruction of the OMC are recognised findings.

69. Chronic sinusitis
 Chronic sinusitis refers to on going long term sinus infection-
inflammation that often develops secondary to prolonged or
refractory acute sinus infection.
 Allergic and fungal sinusitis tend to be usually symmetrical and
involve nasal fossa as well as sinuses. Bacterial sinusitis
involves only single or group of contiguous sinuses.
 Polyps are more common in allergic rather than infected
patients.

71. Fungal diseases
 Invasivse fungal sinusitis:
-Acute/chronic/chronic granulomatus
 Non invasive fungal sinusitis:

72. Acute invasive fungal sinusitis
 It is a rapidly progressing infection seen predominantly in
immunocompromised patients and patients with poorly
controlled diabetes.
 The disease tends to be more rapidly progressing with
relatively high mortality and morbidity.
 Noncontrast CT demonstrates hypoattenuating mucosal
thickening or an area of soft-tissue attenuation within the
lumen of the involved paranasal sinus and nasal cavity

73.  Aggressive bone destruction of the sinus walls occurs rapidly
with intracranial and intraorbital extension of the inflammation.
 These fungi tend to extend along the vessels, and extension
beyond the sinuses may occur with intact bony walls.
 CT is better to assess for bone changes, MR imaging is
superior in evaluating intracranial and intraorbital extension of
the disease.

75. Chronic invasive fungal sinusitis
 Inhaled fungal organisms are deposited in the nasal
passageways and paranasal sinuses. Insidious progression
occurs over several months to years in which fungal organisms
invade the mucosa, submucosa, blood vessels, and bony walls
of the paranasal sinuses.
 Individuals are usually immunocompetent.

76.  A hyperattenuating soft-tissue collection is seen at noncontrast
CT within one or more of the paranasal sinuses.
 Mottled lucencies or irregular bone destruction may be seen in
the paranasal sinuses There may also be sclerotic changes in
the bony walls of the affected sinuses representing chronic
sinus disease .
 Infiltration of the periantral soft tissues about the maxillary
sinus is an indicator of invasive disease

78. Allergic fungal sinusitis
 It is the most common form of fungal sinusitis.
 It is particularly common in warm, humid climates.
 cause is thought to be a hypersensitivity reaction to certain
inhaled fungal organisms

79. Imaging
 There is usually involvement of multiple sinuses. Disease tends
to be bilateral, and there is a frequent nasal component.
 The majority of the sinuses show near-complete opacification
and are expanded.
 Noncontrast CT demonstrates hyperattenuating allergic mucin
within the lumen of the paranasal sinus.

81. Mycetoma- Fungus ball
 Its usually due to deficient mucociliary clearance mechanism in
which fungal organisms deposited in the paranasal sinuses are
inadequately cleared.
 Its common in older individuals.
 The fungus ball represents a tangled collection of fungal
hyphae in the absence of allergic mucin.

82.  Fungus ball appears as a mass within the lumen of a paranasal
sinus and is usually limited to one sinus. The maxillary sinus is
the most commonly involved sinus.
 A fungus ball typically appears hyperattenuating at noncontrast
CT due to dense matted fungal hyphae and may demonstrate
punctate calcifications

83. Sino nasal polyposis
 Polyps are soft tissue pedunculated masses of
oedematous hyperplastic mucosa lining the nasal
cavity and sinuses.
 These are benign mucosal lesions.
 Commonest sites in order of frequency are:
Ethmoids >>Maxillary > Sphenoids

84.  X ray: Opacification of nasal cavity and sinuses.
 Hypodense polypoidal,rounded masses in the nasal
cavity and paranasal sinuses enlarging sinus ostium .
 Expansion of the sinus, thining of sinus walls, nasal
and ethmoid septa.
 Widening of the infundibulum.

86. Antrochoanal polyp
 Benign antral polyp which widens the sinus ostium
and extends into nasal cavity;5% of all nasal polyps.
 Features:
-Well defined mass with mucin density arising within
maxillary sinus.
-Smooth mass enlarging the sinus ostium
-No sinus expansion.

90. Mucocele
 Mucoceles are benign, locally expansile paranasal sinus masses
most commonly found in the frontal sinus.
 Secondary to obstruction of the sinus ostia, there is
accumulation of fluid within a mucoperiosteal lined cavity,
resulting in erosion and remodelling of the surrounding bone.
 The most common causes of mucoceles are chronic infection,
allergic sinonasal disease, trauma and previous surgery.

91.  The most common location of a mucocele is the
fronto-ethmoidal sinus, followed by the sphenoid
sinus.
 The least common location is the maxillary sinus.
 X-ray: will show an expansion of the sinus cavity with
loss of the scalloped margin of the normal sinus.

92.  Soft tissue density mass- having mucoid (15HU)
attenuation.
 Sinus cavity expansion.
 Bone remodeling at late stage but no bone destruction
 Surrounding zone of bone sclerosis/calcification of
edges of mucocele(ch sinusitis).

93.  Protrusion into orbit displacing medial rectus muscle
laterally.
 Expansion into subarachnoid space…. resulting in
CSF leaking.

95. Neoplastic diseases
 Papillomas
 Carcinomas
 Olfactory neuroblastoma.
 Lymphoma

96. InvertedPapilloma
 Occur in middle aged man.
 They arise from lateral wall of nose in the region of
middle turbinate.
 May extend into adjacent paranasal sinuses.

97.  CT: Features are largely non-specific, demonstrating a soft
tissue density mass with some enhancement.
 MRI often demonstrates a distinctive appearance, referred to as
convoluted cerebriform pattern seen on both T2 and contrast
enhanced T1 weighted images. It refers to alternate lines of
low and high signal intensity.

102. Fungiform papilloma
 These make up for half of the papillomas.
 They always arise from nasal septum.
 They are usually solitary and unilateral and may have
an irregular surface.
 They do not have malignant potential.

103. Carcinoma
 Squamous cell carcinoma:
-This is the most common type of PNS carcinoma.
-Most commonly from maxillary sinus.
-6th to 8th decade.
-Most of them are low grade tumors arise from nasal
septum near the mucocutaneous junction.
-These usually go undiagnosed untill they involve oral
cavity or cheek.

104.  Most important feature is bone destruction even in
presence of small demonstrable mass.

106. Adenoid cystic carcinima
 These are the tumors of minor salivary glands.
 They most commonly affects the maxillary sinus
among all the paranasal sinuses.
 They tend to spread along perineural sheaths and tend
to leave skip lesion.

108. Adenocarcinoma
 Arise from seromucinous glands.
 It is common in wood workers.
 Non-specific imaging features- Like bone destruction,
intracranial/ intra orbital extension..
 Predilection for ethmoid sinuses

110. Olfactory neuroblastoma
 Originate from olfactory epithelium.
 Bimodal age distribution with one peak in young adult
patients (~2nd decade) and another in 5th to
6th decades.
 These tumours are slow growing so bony
remodelling is seen rather than bone distruction.

111.  The lesion is very difficult to distinguish from other
malignincies except for its origin.
 Intracranial extension can be seen.

113. Lymphoma
 Majority NHL.
 Nasal cavity and maxillary sinuses are most common
sites.
 These tend to be grossly bulky with good
enhancement.
 They tend to remodel the bone. Bony destruction is
rare.

115. Fibrous dysplasia
 FD is a condition in which medullary bone is replaced
by a poorly organized and loosely wooven bone.
 There will be ground glass appearance of affected
bone.

117. Osteoma
 Mature bony outgrowth.
 Osteomas can be of three types:
- Ivory osteoma
- Mature osteoma.
- Mixed.

119. Kerros classification

120. Kerros clssification

121. FESS
 Its is done to regain the drainage of sinuses.
 Steps:
-Septoplsty.
-Uncinectomy.
-Widening of sinus ostium and infundibulum.
-Unroofing of ethmoid bulla.
-Frontal sinusotomy.

122. Post FESS CT scan
 It has to be interpreted in following ways:
-Anatomical changes that have been made.
-Residual or recurrent disease.
-Any complications -we have to comment on Lamina
papyracea, cribriform plate, roof of ethmoid and all
other sinuses.

124. Granulomatous diseases
 Wegners granulomatosis.
 TB
 Syphilis
 Sarcoidosis.
 Rhinoscleroma.

126. Nasopharyngeal/ Juvenile angiofibroma
 Is a rare benign but locally aggressive vascular
tumour.
 Its is highly vascular and nonencapsulated polypoidal
mass that is histilogically benign but highly
aggressive.
 Males and 2nd decade.
 Site: Nasopharyngeal region at pterygopalatine fossa
or sphenopalatine foramen.

127.  Plain film:
- visualisation of a nasopharyngeal mass
-opacification of the sphenoid sinus
-anterior bowing of the posterior wall of
the maxillary antrum (Holman- miller sign).
-Erosion of the medial pterygoid plate.

128.  CT:
-Typically a lobulated soft tissue mass is
demonstrated centred on the sphenopalatine foramena.
-Typically bowing the posterior wall of the maxillary
antrum anteriorly.
- Marked contrast enhancement.

129. Thank you