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Radiology ofParanasal Sinuses
UmaisMomin, AhmedShaikh, MashaelAlhail,
HamadAl Saey, SaraAshkanani,
andShanmugamGanesan
21
21.1 Introduction
Imaging of paranasal sinuses forms an important
component of examination and preoperative
planning for any surgical intervention. Evaluation
of the paranasal sinuses involves assessment of
two components: the sinus contents, including
the mucosa, and the bony walls including vessels.
Normal sinus mucosa is very thin and is not seen
on CT or MRI, and CT or MRI readily reveals the
presence of a normally aerated sinus, mucosal
thickening (chronic sinusitis, retention cysts, or
polyps), or an air-uid level.
CT scan is the modality of choice for assess-
ment of normal anatomy and pathology of sinuses
U. Momin
Department of Clinical Imaging, Hamad Medical
Corporation, Doha, Qatar
e-mail: Umomin@hamad.qa
A. Shaikh (*) · M. Alhail · H. Al Saey · S. Ashkanani
Otolaryngology-Head and Neck Surgery Division,
Department of Surgery, Hamad Medical Corporation,
Doha, Qatar
Department of Otolaryngology-Head and Neck
Surgery Division, Weill Cornell Medicine-Qatar,
Doha, Qatar
e-mail: malhail@hamad.qa; Halsaey@hamad.qa;
sashkanani@hamad.qa
S. Ganesan
Otolaryngology-Head and Neck Surgery Division,
Department of Surgery, Hamad Medical Corporation,
Doha, Qatar
e-mail: sganesan@hamad.qa
and is routinely performed prior to any sinus surgeries. With the advent of multidetector computed tomography (MDCT), imaging of paranasal
sinuses prior to functional endoscopic sinus surgery (FESS) has become mandatory. Multiplanar
imaging, particularly coronal reformations, offers
precise information regarding the anatomy of the
sinuses and its variations, which is an essential
requisite before surgery.
The success of functional endoscopic surgery
depends on adequate knowledge of the complicated anatomy of the paranasal sinuses. Certain
anatomic variations are thought to be predisposing factors for the development of sinus diseases,
and thus, it becomes necessary for the surgeon to
be aware of these variations, especially if the
patient is a candidate for functional endoscopic
sinus surgery (FESS).
21.2 Technique ofCT Scan
forFESS
At our institution, we performed the scan with
multidetector computed tomography (MDCT)
with the patient in supine position with 1 mm
thick overlapping axial slices.
Axial images of the sinuses are acquired
with 0.5 mm collimation, and from this raw
data, sagittal and coronal reformations are
obtained using both soft tissue and bone window algorithms.
© Springer Nature Switzerland AG 2021
A. Al-Qahtani et al. (eds.), Textbook of Clinical Otolaryngology,
https://doi.org/10.1007/978-3-030-54088-3_21
231
232
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21.2.1 Anatomy andIts Variation
The lateral nasal wall contains three bulbous projections, namely the superior, middle, and inferior turbinates (conchae), which divide the nasal
cavity into superior, middle, and inferior
meatuses.
The superior meatus drains the posterior eth-
moid air cells.
The middle meatus drains the frontal sinus via
the nasofrontal recess, the maxillary sinus via the
maxillary ostium (Hiatus semilunaris), and the
anterior ethmoid air cells via the ethmoid cell
ostia.
The nasolacrimal duct drains into the inferior
meatus.
Sphenoethmoidal recess is a small area above
superior concha and receives the opening of
sphenoid air sinus.
CT scan is the gold-standard investigation in
all sinus diseases [1, 2].
U. Momin et al.
21.3 Ostiomeatal Unit
The osteomeatal unit (OMU) (Fig.21.1) includes
the
1. Maxillary sinus ostium
2. Ethmoid infundibulum
3. Anterior ethmoid air cells, and
4. Frontal recess
The UP prevents the direct contact of the
inspired air with the maxillary sinus, acting like a
shield, and plays a role in mucociliary activity.
The UP is a thin, semi-circular bony process of
variable length and covered with the mucosa.
21.3.1 Ethmoidal Cells [3–5]
Ethmoidal cells according to pneumatization are
classied as
1. Agger nasi
2. Onodi cells
3. Hilar cells
4. Bulla ethmoidalis
Fig. 21.1 Uncinate Process, UP (arrow), Maxillary
infundibulum (block arrow), and OMU (dotted circle)
Fig. 21.2 AN (agger nasi) cell, deviated nasal septum
(red arrow), and septal spur (red arrow head)
21.3.2 Agger Nasi Cells Fig.21.2
This cell is present in nearly all patients and is an
ethmoturbinal remnant. It is the most anterior
ethmoidal air cell and extends anteriorly into the
lacrimal bone [6, 7]. A good view of frontal
recess [8, 9] is obtained when the agger nasi cells
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21 Radiology ofParanasal Sinuses
are opened. Thus, its size may directly inuence
the patency of the frontal recess and the anterior
middle meatus. It forms the anterior and inferior
wall of the frontal recess, and the surgical access
to recess is via the agger nasi.
21.3.3 Onodi Cells Fig.21.3
These are posterior ethmoidal cells extending
into the sphenoid bone, either adjacent to or
impinging upon the optic nerve [10]. 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.
21.3.4 Haller Cells Fig.21.4
These are also called infraorbital ethmoid cells
and are pneumatized ethmoid air cells. These
cells contribute to the narrowing of the infundibulum and may compromise the ostium of the
maxillary sinus, thus contributing to recurrent
maxillary sinusitis [11–13].
These cells may contribute to narrowing of the
infundibulum (Fig.21.5).
Ethmoid bulla (Fig.21.6) is the largest anterior ethmoid air cells.
It is the roof of the hiatus semilunaris and posterior ethmoid infundibulum.
The relationship of ethmoid bulla with lamina
papyracea in lateral, and the relationship of fron-
233
Fig. 21.4 CT shows right Haller cell (star)
Fig. 21.5 MT (Middle turbinate), LP (lamina papyra-
cea), olfactory cleft (black arrow), and Concha Bullosa
(white arrow)
Fig. 21.3 Onodi cell (blue arrow)
tal cranial fossa in superior with base should be
claried in preoperative CT.
The sphenoethmoidal recess, also called the
posterior ostiomeatal unit, drains the posterior
sinuses (posterior ethmoidal and sphenoid)
(Fig.21.7).
Concha Bullosa [14] (Fig. 21.5):
Pneumatization of middle turbinate by the extension of ethmoid sinus cell.
Paradoxical turbinates (Fig.21.8) occur as the
convexity of the middle turbinate is directed
toward the medial wall of the maxillary sinus.
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Fig. 21.6 Ethmoid bulla, EB (red circle), superior turbi-
nate (arrow head), and inferior orbital nerve (red arrow)
Sphenoethmoidal recess
U. Momin et al.
Fig. 21.8 Paradoxical middle turbinate (arrow)
Fig. 21.7 Red arrow sphenoethmoidal recess
21.4 The Frontalethmoidal (Kuhn)
Cells [15]
Fig. 21.9 Type 3 frontal cell (red arrow) and Agger nasi
(yellow)
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
There are various accessory air cells in the frontoethmoidal region that may or may not be present. It is important to work out the drainage
pathway of the frontal sinus around these cells.
Frontalethmoidal air cells, also known as
that extends into the frontal sinus (Fig.
Type 4: Completely contained in the frontal
sinus.
Radiological characteristics of some diseases
are as follows.
Kuhn air cells, are categorized into four types
depending on their number and degree of extension into the frontal sinus.
21.4.1 Inverted Papilloma
Type 1 (most common): Single cell superior to
the ANC that does not extend into the frontal
sinus (i.e., remains below the “beak”).
• Inverted papilloma are benign tumors of
unknown etiology characterized by strong
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21.9).
ab
21 Radiology ofParanasal Sinuses
235
potential for local destruction, high rate of
recurrence, and malignant potential.
• They display characteristic radiological ndings [16].
CT characteristics include (Fig.21.10)
• Heterogeneous enhancement
• Sclerosis and erosion of the bones
• Periosteal thickening
• Osteoblastic rimming and immature bone formation which helps in prediction of site of
attachment
21.4.2 Osteitis Sign (Fig.21.11)
• Presence of thickening of sinus wall compared
to the contra lateral site
• Osteogenesis and thickening of the bone or
sclerosis
MRI pattern includes (Fig.21.12)
• Convoluted cerebriform pattern on MRI
• T1 and T2
• T1: isointense to muscle
• T2 generally hyperintense to muscle alternating hypointense lines
• T1 C+ (Gd) heterogeneous enhancement
alternating hypointense lines
Fig. 21.10 Osteogenesis marked with arrow
Fig. 21.11 Osteitis sign (white arrow). (a) CT sinus. (b) MRI sinuses
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U. Momin et al.
21.5 Allergic Fungal Sinusitis
21.13) [20–24]
(Fig.
Allergic fungal sinusitis (AFS) represents distinct forms of chronic rhinosinusitis with nasal
polyposis characterized by high recurrence.
Imaging characteristic of AFS includes:
Double-density shadow on CT sinus, and the
high-density shadow is produced by high-density
minerals, that is, manganese, aluminum, and calcium concentrated by fungal concretions.
Fig. 21.12 MRI T2-weighted image showing cribriform
pattern [17]
Expansile destruction of the paranasal sinuses.
MRI characteristic of allergic fungal sinusitis
(Fig.
21.14):
Hypointensity on T1WI and T2WI is the most
common nding.
T1: hypointense inamed mucosal thickness.
It can have multiple T1 appearances.
T2: usually a hyperintense peripheral inamed
mucosal thickness.
Low T2 signal or signal void is due to high
concentration of metals such as iron, magnesium,
and calcium concentrated by fungi and high protein and low water content in allergic mucin.
T1 C+ (Gd):
• An inamed mucosal lining has contrast
enhancement
• No enhancement in the canter
21.5.1 Neoplasms (Fig.21.15a, b) [23, 24]
Various nasal neoplasms include lymphoma,
squamous cell carcinoma, and esthesioneuroblastoma (Fig.21.16).
They all show extensive bony destruction with
enhancement on contrast.
Double Density
Fig. 21.13 Coronal CT scan showing double density (red arrow) allergic fungal sinusitis [17–19]
Double density shadow soft
tissue window
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ab
21 Radiology ofParanasal Sinuses
237
T1
T2
Fig. 21.14 T1 and T2 images of MRI AFS ow void seen in the maxillary sinus (arrow) T2-weighted images with
hyperintense inamed sinus mucosa
Fig. 21.15 (a) Precontrast MRI T1 image showing mass lesion with extensive destruction. (b) Postcontrast enhancing
lesion MRI T1 image with excessive destruction
21.6 Vessels inParanasal Sinuses
21.7 Anterior Ethmoidal Artery
(Fig.21.17)
Major vessels seen on the plane CT scan are
anterior ethoidal artery, posterior ethmoidal
artery, sphenopalatine artery, and carotid
artery.
Anterior ethmoidal artery (AEA) is a branch of
ophthalmic artery given in the orbit. It exists
between the superior oblique and medial rectus.
238
U. Momin et al.
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In its intranasal route, the anterior ethmoid artery
lies inside a bony canal called anterior ethmoidal
canal that leaves the orbit through the anterior
ethmoidal foramen.
Anterior ethmoidal artery is seen at the anterior ethmoidal roof as marked in the image.
21.8 Posterior Ethmoidal Artery
(Fig.
21.18)
Fig. 21.16 Heterogeneous mass with destruction of skull
base and lamina papyracea (Lymphoma)
Fig. 21.17 Anterior ethmoidal artery (AEA, red mark)
with olfactory cleft (yellow) and fovea ethmoidalis (blue)
Fig. 21.18 Image
showing PEA at the
skull base (red dots)
The posterior ethmoidal artery (PEA) is a branch
of ophthalmic artery passes through the posterior
ethmoidal canal and enters the dura at the posterior margin of the cribriform plate and supplies
the dura of the medial third of the oor of the
anterior cranial fossa. PEA is seen at the roof of
posterior ethmoidal cells and most of the time is
covered with bone.
21.9 Sphenopalatine Artery
21.19)
(Fig.
Sphenopalatine artery (SPA) is a terminal branch
of the internal maxillary artery originating from
the external carotid artery system. The SPA is the
major blood vessel to the nasal cavity mucosa:
supplying the superior, middle, and inferior turbinate; lateral nasal wall; and nasal septum. The
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21 Radiology ofParanasal Sinuses
Fig. 21.19 Sphenopalatine artery exiting from the sphe-
nopalatine foramen (red). NLD nasolacrimal duct
239
3. Vidian nerve
4. V2 Division of trigeminal nerve in foramen
rotundum marked
Take Home Messages
• It is important to study the CT sinuses
prior to any surgical intervention for
anatomical variations.
• Allergic fungal sinusitis has characteristic appearance on CT scan and MRI
scan.
• CT sinus in chronic rhinosinusitis forms
one of the criteria for diagnosis.
• Anatomical variations of vessels in the
nasal cavity are common, and dehiscence of vessels should be studied
before FESS.
• The aim of this chapter is to highlight
the clinically relevant sinonasal anatomy and variants.
Fig. 21.20 Optic nerve (blue arrow), carotid artery (red),
Vidian nerve (red arrow), and V2 (white arrow)
sphenopalatine artery travels within the pterygopalatine fossa and enters the nasal cavity through
the sphenopalatine foramen within the superior
meatus between the middle turbinate and the posterior end of the superior turbinate on the lateral
nasal wall.
Lateral sphenoid wall shows following impor-
tant structures (Fig.21.20):
1. Optic nerve
2. Carotid artery
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