This document summarizes important anatomical variations of the paranasal sinuses that are relevant for sinusitis. It describes variations that can occur in structures like the agger nasi cells, uncinate process, middle turbinate, cribriform plate, and maxillary ostia. These variations include pneumatization of cells or bony structures as well as anatomical abnormalities that can obstruct drainage of the sinuses. Understanding these variations is important for evaluating patients with recurrent sinusitis as certain variations may contribute to obstruction and recurrence.

1. ANATOMIC VARIANTS CT-PNS
-To highlight the clinically relevant
sinonasal anatomy and variants
Susritha.k
Dpt of ENT
ASRAMS.

2.  The significance of anatomic variants is
determined by its relationship with the
osteomeatal channels and nasal air passages.
 The ability of the variation to obstruct the air
passages implies a role in recurrence of sinusitis.

3.  The nasal turbinates are embryologically derived
from a series of outgrowths from the foetal lateral
nasal wall.
 The outgrowths form a series of ridges, referred to
as “ethmoturbinals” which are separated by
furrows.
 Each ridge has an anterior ascending portion
and a posterior descending portion.
 The uncinate process develops from the
descending portion of the first ridge, which is also
known as the “nasoturbinal”

4.  The agger nasi develop from its ascending
portion.
 The second ridge forms the bulla lamella, or the
bulla ethmoidalis when pneumatized.
 The middle turbinate develops from the third
ridge, which is the first permanent ethmoturbinal.
 The fourth ridge, the second permanent
ethmoturbinal, forms the superior turbinate.
 Based upon this, variations in development and
pneumatization of the ethmoturbinals may lead
to anatomical variations within the bony
structures of the ethmoidal complex.

5.  The Agger Nasi Air Cell :
 Its an ethmoturbinal remnant present in nearly all patients.
 The ANC is the most constant and anterior of the
ethmoidal air cells.
 Located anterior to the vertical attachment of the middle
turbinate to the skull base.

8.  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.
 If the ANC is small, then the “beak” of the frontal
process of the maxilla, lying anteriorly and
superiorly, will be prominent and extend
posteriorly into the frontal recess, resulting in a
narrow ostium.
 If the ANC is large, the beak will be small,
resulting in a wider ostium but potentially causing
obstruction more inferiorly.

9. 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 saggital 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.
 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.

10.  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.

12.  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.

13.  A,b)bilateral onodi cells.
 C)sphenoid sinus ostium without connection with the
Onodi cell.

14. ONODI CELL

15. Delano,fun zinreich classification
 Relation b/w posterior group of sinuses with optic
nerve
 Type1: optic nerve adjacent to sphenoid sinus.
 Type2: optic nerve indentation on sphenoid sinus.
 Type3: optic nerve traversing through sphenoid sinus.
 Type4: optic nerve adjacent to sphenoid & post. Eth.
Sinus.

16. Uncinate process
 The uncinate process is a superior extension of
the lateral nasal wall that is anatomically
relevant for draining the frontal recess.
 Variations such as hypertrophy, deviation and
pneumatization may affect the drainage,
generating abnormalities in the osteomeatal
complex.

17.  A)horizontal uncinate
 b)hypertrophy of lt uncinate.
 C)pneumatisation of lt uncinate.
 D)vertical lt uncinate.

18. Table showing types of OMC
abnormalities

19. Variations in the superior insertion of the uncinate process are
classified according to criteria developed by Landsber &
Friedman
 A: Type 1 (insertion into the lamina papyracea).
 B: Type 2 (insertion into the posterior wall of agger nasi cell).
 C: Type 3 (insertion into the lamina papyracea and junction of the
middle turbinate with the cribriform plate).
 D: Type 4 (insertion in to 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)

20. Aerated uncinate

21. VARIATIONS OF THE CRIBRIFORM PLATE
 The cribriform plate may present at variable
levels and, it is classified according to the criteria
developed by Keros.
 It is based on the height of the olfactory fossa in
relation to the roof of the ethmoid sinus as
compared with the length of the lateral lamella
of cribriform plate.
 The higher the Keros grade, the greater the
chance of injury of the cribriform plate and
olfactory fossa.

22.  A: Type 1 (lateral cribriform lamella of 1–3 mm, the
cribriform plate and the ethmoid cell roof are practically
parallel to each other).
 B: Type 2 (lateral lamella of 4-7 mm, cribriform plate is
much below the nasal cavity as compared with the
ethmoid roof).
 C: Type 3 (lateral lamella of cribriform plate of 8–16 mm,
ethmoid cell roof is located much above the plate

24. Haller cell
 Infraorbital ethmoid cells or Haller cellsare
ethmoid air cells located anteriorly 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.

26. VARIATIONS IN MIDDLE
TURBINATE
 Concha bullosa is a variation originated from
pneumatization of the bone plate by extension
of ethmoid sinus cells.
 Such variation may be either uni- or bilateral.
 Varied degrees of pneumatization of the
concha may be observed, possibly causing
middle meatus or infundibulum obstruction.

29. PARADOXICAL TURBINATES
 Paradoxical turbinates occur as the convexity of
the middle turbinate is directed towards the
medial wall of the maxillary sinus.
 Depending on the degree of curvature of the
paradoxical turbinate compression of the
infundibulum and sinusal obstruction may be
observed.

32. 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.

34. Few endoscopic pictures

36. Bulla ethmoidalis

37. Concha bullosa

38. Medialised uncinate

39. Elevated uncinate

40. Pneumatised uncinate

41. Obstructive uncinate

42. Anteriotly bent uncinate

43. Secondary middle turbinate
 Rare anamoly.
 It’s a bone covered by soft tissue arising from
lateral nasal wall.

45. THANK YOU…!