Anatomical variation in coronal CT

1. Anatomical Variations of
Paranasal Sinuses on Coronal
CT-Scan in Subjects with
Complaints Pertaining to PNS
(concentrated on coronal CT)
Presented by
Dr. Liju Rajan,
2nd year postgraduate
Moderator
Dr. CP DAS
Dr. D Mohanty

2.  The CT scan is the gold standard investigation in Functional Endoscopic Sinus
Surgery preoperative cases and cannot be replaced by the MRI because it
gives detailed bony anatomy of the area and serves as a “road map” for the
operating surgeon
 A very basic paranasal sinus study would include bony and soft tissue windows
of 3 mm cuts taken anterior to posterior in the coronal plane

3. Timing of CT
 Acute sinusitis adequately treated ( 3 weeks after course of antibiotics and NSAIDS)
 Chronic inflammatory diseases- maximised medical therapy
 It is advisable to use topical nasal decongestant before CT, or atleast blow the nose and
clear secretions
 Role of CT
to define PNS anatomy
to identify regional disease in medical non-responders

4. Coronal Scan
 Most of the anatomical details can be seen well in coronal sections.
 Because this plane is almost identical to that approached by endoscopes
 Best displays Osteo-Meatal Unit
 Uncinate Process & Ethmoidal Bulla lie on a vertical plane

5. CT Patient Positioning

6. 1st Cut
Soft tissue over frontal bone
Nasal bone
Nasal Septum
Nasal ala

7. Frontal bone proper
Nasal bone
Nasal Septum bony and
cartilaginous part
Nasal ala

8. Frontal Sinus with septae
Nasal bone
Nasal Septum bony
Frontal process of maxilla

9. Septal tubercle

10.  Well developed frontal sinus with
intact floor
 False frontal septum disappearing
 Inferior turbinates

11.  Maxillary sinus starts appearing.
 Well developed frontal sinus

12.  1st cell appearing in scan. Agger
nasi cell
 Well developed frontal septum
with intact floor
 Middle turbinate starts come into
the view
 Nasolacrimal system comes into
view

13.  Floor of frontal sinus is missing.
 Frontal recess
 Aggar Nasi cell not seen. Frontal recess present
posterior to aggar nasi cells
 First part of middle turbinate in saggital plain getting
attached to the roof
 Concha

14.  Bulla ethmodalis
 Concha bullosa
 Uncinate process
 Hiatus semilunaris inferialis
 Infundibulum
 Triangular shaped maxillary sinus
 Pneumatised crista galli
 Supraorbital cell
 Well developed olfactory fossa
Keros type2

15.  Uncinate insertion and frontal
recess drainage
 Osteomeatal complex

16.  Haller cell or infraorbital cell

17.  Ant ethmoidal artery
 Another land mark for starting of
posterior ethmoidal cells and basal
lamella
 Loss of sharpness of triangular
shape of maxillary sinus

18.  Ground lamella – transcission 2nd part
 Superior turbinate
 Posterior frontanalle

19. Changes while going from ant ethmoid to
post ethmoid
 Orbit – more smaller and squire
 Maxillary sinus- from triangular to oval
 Larger and fewer air cells
 Flatter and thicker skull base
 Past Ground lamella
 Past ant ethmoidal.a
 Presence of sup turbinate

20.  Middle turbinate inserts into medial wall of
maxilla

21.  Inferior orbital fissure

22. Differentiate between posterior
ethmoids and sphenoids
 Posterior ethmoids
Ccomplete septum will be seen
Clear view of inferior and middle
turbnate
 Sphenoid
 Inter sphenoidal septum
 Turbinates not clear

23.  Choana
 Sphenoid sinus
 Greater wing of sphenoid
 Vidian cannal
 Foramen rotendum
 Ptregoid process
 Medial and latral ptregoid plates
 Optic nerve
 Buldge of carotid artery
 Medial ptregoid plates forming
lateral wall of choana

25. Septal Deviations
 There may be gross septal deviations as well as mild
 Bony deviations can be clearly seen and studied
 Sometimes may be associated with concha bullosa , ITH or a pneumatised septum or may be
associated with osteomeatal unit

26. Agger Nasi Cell
 1 to 3 in number and may vary
 Some times these cells may be hypoplastic
 Some times prominent which causes
changes in superior attachment of uncinate
and also bulge in middle turbinate

27. Uncinate Process
 The uncinate process may be hypoplastic or laterally bent. In this case the
infundibulum is a narrow space, which may be difficult to enter
 Sometimes will be well developed and resemble anterior wall of bulla.
Sometimes more medially rotated and present like a duplication of middle
turbinate
 Upper attachment of uncinate process

28. Uncinate getting attached to medial wall of orbit

29. Uncinate getting attached to skull base

30. Uncinate getting attached to middle turbinate

31. Uncinate lying free without attachment

32. Pneumatised Uncinate Process

33. Middle Turbinate
Concha bullosa the
pneumatisation of middle
turbinate
pneumatized from either the
frontal recess,
the agger nasi cell,
anterior ethmoid cells or the
middle meatus
Or a isolated cell
Large concha may impair drainage
of PNS

34.  Pneumatisation of vertical lamella
of middle turbinate

35.  Middle turbinate shows a latral
bent instead of medial bent
 Can block infundibulum

36.  A normally curved middle turbinate
may curl upon itself to produce a
concavity within it. This concavity
is called the turbinate sinus

37. Ethmoidal Bulla
 The ethmoidal bulla is usually the largest and most constantly pneumatized
anterior ethmoid cell
 hypoplastic or rarely even a solid non-pneumatized
 Some cases very prominent and may push uncinate or middle meatus
compromising infundibulum or middle meatus

38.  Usually bulla extend upto skull base if not
the space present is suprabullar recess
 In some cases bulla will not extend up to
ground lamella the space is called
retrobullar recess
 Suprabullar recess and retro bullar resess
togother form sinus latralis grunwald
 It drains into a semilunar space hiatus
semilunaris superioralis

39. Ethmoidal air cells
 Infraorbital cell or haller cell
 Compromise the maxillary sinus
drainage

40.  The anterior ethmoid cells may migrate into the frontal recess area where they are then named
the frontal cells. These are of four types
 — Type I: A single cell above the agger nasi cell.
 — Type II: Two or more cells above the agger nasi cell.
 — Type III: (Frontal bulla) A cell which extends well into the frontal sinus. Single massive cell
pneumatizing cephalad into frontal sinus
 — Type IV: An isolated “loner cell” within the frontal sinus.

45. Ground Lamella
 The ground lamella of the middle turbinate, which separates the anterior and
posterior ethmoid cells, is not always in a coronal plane
 May bulge into anterior ethmoid or posterior ethmoid and have convexity vise
versa
 It may show dehiscences or be partially deficient in which case infection can
pass from anterior to posterior ethmoids

46.  Some times may get pneumatised
to form multiple septae

47.  Some cases the 2nd part of middle
turbinate directly get attached to
medial wall of maxillary sinus.
Thus maxillary sinus behaves as 2
one part as posterior ethmoids and
other as maxillary sinus in terms of
drainage and disease

48. Superior/Supreme Turbinate

49. Olfactory Fossa

52. Sphenoid sinus
 It may be present as a small pit in
a predominantly non-pneumatized
sphenoid bone-conchal type.
 It may extend upto the anterior
wall of the sella turcica—Presellar
type
 It may pneumatize the entire
sphenoid body below and behind
the sella turcica, so that the
pituitary forms a distinct bulge in
its posterosuperior wall—Sellar
type

53.  Inter sphenoidal may not divide
sphenoid equally
 Septum may get attached to vital
structures like Optic Nerve and
Carotid artery

54.  The sphenoid sinus may show
extensive pneumatization laterally
into the pterygoid processes and
the greater wing of sphenoid.
 The maxillary and vidian nerves
can then be seen prominently
within these lateral recesses of the
sphenoid

55. Maxillary Sinus
 The maxillary sinus is fairly constant in its pattern of pneumatization and
drainage. Occasionally it may be hypoplastic or asymmetric.
 Rarely it may be completely absent
 Accessory ostia may be present in the anterior and posterior fontanelle in 25
percent of the cases
 May get pneumatised extensively and encroach on alveolar process of teeth
 Infra orbital nerve is dehesent and lie submucosally

56. Anatomical Variations of
Paranasal Sinuses on
Coronal CT-Scan in
Subjects with Complaints
Pertaining to PNS
Journal Proper
IJARS - Intrenational journal of anatomy radiology and surgery

57. MATERIALs AND METHODS
 This prospective study was performed in the Department of Radiodiagnosis,
Mysore Medical College and Research Institute (KR Hospital) Mysore
 Total 100 patients who were referred form ENT OPD and wards from
December 2013- July 2015 (1/12/2013 to 31/7/2015) with complaints
pertaining to PNS were included in the study
 Patients were subjected to Coronal CT-scans of PNS using GE SYSTEMS-Hi
Speed Dual-Slice CT. For CT examination patient was positioned in prone
position with neck extended and angulation was perpendicular to hard palate.

58.  Imaging was done from posterior margin of sphenoid sinus to anterior margin
of frontal sinus. Thickness was 5mm slices with 3mm retro reconstruction.

59.  The images were reviewed using bone and soft tissue windows and the details were analyzed:
 1. Septum Deviation
 2. Agger nasi pneumatized
 3. Bulla Ethmoidalis
 4. Uncinate process
 5. Middle turbinate: pneumatisation
 6. Maxillary sinus septation
 7. Pneumatized superior turbinate
 8. Supraorbital cell
 9. Haller cell
 10. Onodi cell
 11. Frontal sinus
 12. Cribriform Plate
 13. Extramural sphenoid pneumatization
 14. Other findings: Inflammatory sinus disease acute, chronic or allergic. If present, in which sinus?

60. Statistical Analysis
 Results were cross tabulated.
 Frequencies descriptive statistics were the statistical methods used. Level of
significance of findings was assessed by Chi-square test

67. DISCUSSION
 Nasal cavity and para nasal sinuses together form a single anatomical and
functional unit.
 Congenital anomalies and normal anatomical variations in this region are a
rule rather than exception. Conventional X-rays don’t provide adequate
information because of structural superimposition. There has been
tremendous advances in the surgical treatment of sinusitis in recent years,
particularly in Functional Endonasal Endoscopic Surgery (FESS), which requires
the clinician to have a precise knowledge of nasal sinus anatomy and
anatomical variants, many of which are detectable only by the use of CT.

68. Deviated Nasal Septum
 In a study of 110 subjects by Perez-Pinas J Sabate et al., [1], 80 subjects
showed DNS. Most were non traumatic deviations of the septum (64 cases,
72%); the numbers of left and rightward deviations were similar, with a slight
predominance of the former
 In our study 62% of patients showed deviated nasal septum and also showed
slight predominance to the left side (29%) as compared to right side (23%). On
statistical basis p values were also significant (p<0.001).

69. Occurrence of Special Cells
Presence of agger Nasi cells in this study is 26%

71.  The optic nerve is in close relation with Onodi cells when
present, accurate delineation of optic nerve is important
in preoperative planning. The presence of Onodi cells is
the most important factor limiting posterior extent of
endoscopic clearance.

72. Septations in PNS
 According to John Earwaker , maxillary sinus showed septations in about 19
cases out of 800 patients studied. According to Abdullah BJ et al., out of 70
patients studied 68.9% showed septations in the sphenoid sinus
 In our study frontal sinus showed septations in about 31%.Maxillary sinus
showed septations in about 19%. Sphenoid sinus showed septations in about
49%.

73. Frequency of Variations of Middle
Turbinate
 In our study 43% of the cases
showed concha bullosa [Table/Fig-
14,15] out of which bilateral is the
maximum of about 41% followed by
right side of about 32% and least is
on the left side of about 25%.
 Presence of a concha bullosa does
not suggest a pathological finding.
However, in the setting of chronic
sinus disease, resection of the
concha bullosa should be
considered to improve paranasal
sinus access

74. Orientation of the Uncinate Process
 Earwaker observed horizontal orientation of the uncinate process, unilaterally
or bilaterally in 19% of cases, the variant was associated with an enlarged
ethmoidal bulla and, in some cases, with contralateral septal deviation.
Vertical orientation of the process which appeared enlarged or deformed was
observed in 32% of patients
 In our study 43% of cases showed horizontal orientation [Table/Fig-18] of the
uncinate process (with 82% of the cases associated with enlarged ethmoidal
bulla) and 57% cases showed vertical orientation of the uncinate process(with
8.7% of the cases associated with enlarged ethmoidal bulla

75. Cribriform Plate
 Soraia Ale Souza et al.,[20] study showed Keros type II as the most common
variant (73.3%) followed by type I in 26.3% and type III in 0.5% of cases.
However, in our study Type I is commonest. The type of cribriform plate is
important in predicting the intra operative complications during FESS

76. CONCLUSION
 Direct coronal CT is the imaging modality of choice for the evaluation of the
anatomical variations in paranasal sinuses
 Coronal CT-scan provides more detailed information of the posterior sinus
variations.
 Among the special cells, Aggernasi cell is the most common type
 Septations in paranasal sinuses is most common in sphenoid sinus
 Vertical orientation of uncinate process is the most common variety
 Type I variety of the cribriform plate is the most common type.