4. OBJECTIVE
1. To illustrate important anatomic variants
and landmarks on pre-operative sinus
CT
2. With a focus on critical variants and
landmarks that predispose patients to
surgical complications
5. Normal Variant
Septal deviation
Nasal obstruction
limiting endoscopic visualization and
access
Implication – may need septoplasty
STEP 1 - NASAL SEPTUM
10. Landmark for access to the posterior ethmoidal air cells
Normal Variants
Concha bullosa
Paradoxical middle turbinate
Implication
Critical attachment to base of skull at cribriform
plate.
Preserved as a landmark for revision surgery
STEP 2 - BASAL LAMELLA of the MIDDLE
TURBINATE
13. Landmark for the osteomeatal complex
(OMC), lying just posterior to it.
The role of the uncinate process is that of
facilitating drainage of the frontal recess.
STEP 3 – UNCINATE PROCESS
14. Landsberg aand Friedman classification of superior uncinate
process insertion.
a) Type 1 - insertion into lamina papyracea, b) Type 2 - insertion into
the posterior wall of the agger nasi cell, c) insertion into the lamina
papyracea and junction of the middle turbinate with the cribriform
plate, e) Type 5 - insertion into the skull base, f) Type 6 - insertion
into the middle turbinate.
15. Normal Variants
Lateral deviation
Implication
There is a high risk of entry into the
orbit
STEP 3 – UNCINATE PROCESS
17. The ethmoid bulla - largest and most constant
anterior ethmoid air cell.
Implication
laterally - risk of penetration especially of a
dehiscent lamina papyracea with risk of
damaging orbital contents,
superiorly - penetration into floor of anterior
cranial fossa.
STEP 4 – ETHMOID AIR CELLS
18. Sagittal CT demonstrating an ethmoid bulla (arrow) complicated by sinusitis
and
an effusion. The ethmoid bulla is bound superiorly by the floor of the anterior
cranial fossa and laterally by the lamina papyracea.
19. AGGER NASI CELL
the most anterior ethmoid air cell lying just
anterior to attachment of middle turbinate and
frontal recess
Implication –
if large may cause medial displacement of the
middle turbinate causing narrowing of the frontal
recess.
STEP 4 – ETHMOID AIR CELLS
21. HALLER CELL
infraorbital cell extending to floor of orbit
Implication
may cause narrowing of maxillary sinus
ostium/ethmoid infundibulum.
STEP 4 – ETHMOID AIR CELLS
23. The frontal sinus drainage pathway
(FSDP) has 2 compartments:
The frontal air cells constitute the
superior compartment.
The inferior compartment is a narrow
passageway formed by either the
ethmoid infundibulum or the middle
meatus
STEP 5 – FRONTAL/KUHN'S AIR CELLS
43. Coronal and axial planes
Remote orbital fracture
Orbital prolapse into ethmoid sinus
Haller cells
Uncinate process contacting orbital wall
STEP 7 – LAMINA PAPYRACEA
52. Sagittal and axial planes
Conchal, presellar and sellar
pneumatization.
Pneumatization into skull base and
anterior clinoid
STEP 9 – SPHENOID SINUS
68. Components of the “CLOSE” Mnemonic
Critical Anatomic
Structure
Ideal Imaging
Plane
Items to Evaluate and Document/Report
Cribriform plate Coronal Keros classification (type I–III)
Asymmetric Keros
Bony dehiscence of skull base
Lamina papyracea Coronal, axial Remote orbital fracture
Orbital prolapse into ethmoid sinus
Presence of Haller cell
Uncinate process contacting orbital wall
Onodi cell Coronal Presence or absence of Onodi cell
Dehiscence of optic nerve within Onodi cell
Sphenoid sinus
pneumatization
Sagittal, axial Pneumatization pattern (conchal, presellar, sellar)
Pneumatization into skull base & anterior clinoid
Dehiscence of carotid canal
Sinus septation inserting onto carotid canal
Optic nerve dehiscence within sphenoid sinus
Anterior) ethmoidal
artery
Coronal Identify ethmoidal notch
Presence of supraorbital pneumatization
69. The radiologist's goal is to report on five
key points:
1. the extent of sinus
opacification/disease
2. opacification of sinus drainage
pathways
3. anatomical variants
4. critical variants
5. condition of surrounding soft tissues of
the neck, brain and orbits
Radiologist’s goal
