Per-operative PNS CT by Dr. Furqan Ahmad

1. PRE-OPERATIVE PNS CT
A 10-STEPS EVALUATION
Dr. FURQAN AHMAD
Radiologist
CT and MRI Department
Doctors Hospital & Medical Centre

2. STAGES OF FESS

3. POST-FESS

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

6. DNS and ENLARGED IT

7. OSTIOMEATAL COMPLEX ANATOMY

8. CORONAL CT OF OMC

9. OSTIOMEATAL COMPLEX ANATOMY

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

11. CONCHA BULLOSA

12. PARADOXICAL CURVE of MT

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

16. INFUNDIBULAR NARROWING by 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

20. AGGER NASI

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

22. HALLER CELLS and INFUNDIBULAR NARROWING

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

24. FRONTAL RECESS ANATOMY

25. FRONTAL and SE RECESSES

26. SAGITTAL CT FRONTAL RECESS

27. AGGAR NASI CELLS

28. TYPE 1 FRONTAL CELL

29. TYPE 2 FRONTAL CELLS

30. TYPE 2 FRONTAL CELLS

31. TYPE 3 FRONTAL CELLS

32. TYPE 3 FRONTAL CELLS and FRONTAL BULLA

33. TYPE 4 FRONTAL CELL

34. TYPE 4 FRONTAL CELL

35. Coronal plane
Bone integrity
Keros classification
 Keros I - 1 - 3mm
 Keros II - 3 - 7mm
 Keros III - 7 - 16mm
Asymmetric Keros
STEP 6 – CRIBRIFORM PLATE

36. Implication
 Higher risk of intracranial penetration
with increasing depth
 Damaging the anterior and/or
posterior ethmoidal artery.
STEP 6 – CRIBRIFORM PLATE

37. KEROS TYPE 1

38. KEROS TYPE 2

39. KEROS TYPE 3

40. ASYMMETRIC OLFACTORY FOSSAE

41. DEHISCENT CRIBRIFORM PLATE

42. DEHISCENT CRIBRIFORM PLATE

43. Coronal and axial planes
Remote orbital fracture
Orbital prolapse into ethmoid sinus
Haller cells
Uncinate process contacting orbital wall
STEP 7 – LAMINA PAPYRACEA

44. LP DEHISCENCE

45. LP UP APPOSITION

46. ONODI CELL - posterior ethmoid air cell
(5%)
Implication
 Potential damage to
 (a) optic nerve (in 5%), and less
commonly,
 (b) the internal carotid artery
STEP 8 – ONDOI CELLS

47. ONODI CELLS

48. ONODI CELLS and OPTIC NERVES

49. SPHENOID BONE and SKULL BASE

50. AXIAL CT SPHENOETHMOIDAL RECESS

51. SAGITTAL CT SPHENOETHMOIDAL RECESS

52. Sagittal and axial planes
Conchal, presellar and sellar
pneumatization.
Pneumatization into skull base and
anterior clinoid
STEP 9 – SPHENOID SINUS

53. CHONCHAL SS

54. PRESELLAR SS

55. SELLAR SS

56.  Dehiscence of carotid canal
 Sinus septation inserting onto carotid
canal
 Optic nerve dehiscence within sphenoid
sinus
STEP 9 – SPHENOID SINUS

57. DEHISCENT CAROTID CANAL

58. DEHISCENT CAROTID CANAL

59. DEHISCENT OPTIC NERVE

60. DEHISCENT OPTIC NERVE CANAL

61. DEHISCENT SS and CEPHALOCELE

62. CT CISTERNOGRAM

63.  Coronal plane
 Identify ethmoid notch
 Supraorbital pneumatization
STEP 10 – ANTERIOR ETHMOIDAL ARTERY

64. ANTERIOR ETHMOIDAL NOTCH

65. VULNERABLE ANTERIOR ETHMOIDAL ARTERY

66. SUPRAORBITAL ETHMOIDAL CELL

67. DEHISCENT LEFT POSTERIOR ETHMOIDAL ARTERY

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

70. THANK YOU