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Nose and paranasal sinuses

Normal anatomy, IFA classification& variations relevant for surgery

Bernhard Schuknecht

Medical Radiological Institut Zurich

European Course in Head and Neck Neuroradiology Nov 4-6, 2020

Normal anatomy ? → anatomic variations !frontal sinus –ethmoid - sphenoid

lack of consensus with respect to the clinical significance of anatomic variations !→ uniform acceptance regarding the relevance for  endoscopic surgery !!

frontal beakdepth of frontal sinusposition of ethm. roofOnodi cell

If you go to the mountain often enough, you will meet the tiger

ZH paranasal sinus CT protocoll

how scan axial alveolar process ‐ top of frontal sinus (DLP  ↓) 

→ low dose acquistion,  eff. mAs 90‐120  (dose ~ 0.1 mSV)→ reconstruction of data 0.6mm →  3 planes @ 0.75 mm, → bone window H70h, W 3200/ C 700→ soft tissue window H30s 0.75 →3mm ax/corW 300/ C 100→ navigation data: axial including. nose, front, ears→ correct pat. positioning and plane orientation

•al

coronal axial sagittal

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Zürich paranasal sinus CT protocol 

how :  iv contrast*:

• not required for preop. assessment of anatomy

• acute inflammation with complications

• suspicion of tumor (inverted papilloma, neoplasm)

• vascular lesions (angiofibroma, vascular malformations )

• (unilateral lesions!)

Paranasal sinus – CT      ± navigation !!

When: chron. rhinosinusitisc s symptoms >12 weeks

ff maximal + optimal conservative tx

→ visualize drainage pathways + anatomy 

→ assess persistent/recurrent unilateral disease

acute rhinosinusitis symptoms < 12 weeks

→ identify complications (MR?)

→ verify location and extension

→ reassure diagnosis (insuff tx response) 

neoplasm w. osseus erosion or tu of bone /cartilage origin

suspected inverted papilloma 

persistent mucosal swelling, chronicity of disease?

treatment: culture or empirically driven antibiotics for 2 w topical steroid for 3w  or systemic steroids for 5 days

anterior ostiomeatal complex disease

posterior ostiomeatal complex diseaseLense dose CT 0.1 - 0.5 mSv

CBCT 0.05- 0.3 mSv

Lens protection device Ø navigation

well considered indication + good technique + communication= best radioprotection

Radiologist

Rhinologist

How? 

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the nose and septum are part of the exam ! Nasal cavity→ middle meatus

Concha bullosa Haller cells Maxillary sinus pneumatisation

Anatomy coronal + osteomeatal complexEthmoid roof = fovea ethmoidalisOlfactory fossaCribriform plate – lateral lamellaMiddle turbinate vertical lamellaInferior turbinatePerpendicular laminaOlfactory rimAgger nasiEthmoid bullaFrontal recessHaller – infraorbital ‐ cell

Ostiomeatal complex → middle meatus• frontal recess + frontal sinus ostium• ethmoid infundibulum• hiatus semilunaris

obstruction of ostia→ stasis of secretions→ propagation of infection/inflammation  Frontal sinus beak‐ depth

Frontal recessOlfactory fossaCribriform plateMiddle turbinate vertical/basal lamella

Inferior turbinateOlfactory rimAgger nasiEthmoid bullaUncinate process

posterior ostiomeatal complex• spheno‐ethmoid recess‐ sphenoid sinus• superior meatus ‐ posterior ethmoid –Onodi‐ cells

Anatomy sagittal plane : osteomeatal complex

obstruction of ostia → stasis of secretions→ propagation of infection/inflammation 

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Middle turbinate

Transition of vertical to ground lamella separates  ant. and post. ethmoid 

vertical lamella

ground lamella

8 –point preoperative CT checklist :

• uncinate process

• ethmoid roof

• ant. ethmoid artery

• lamina papyracea

• optic nerve

• internal carotid artery

• bony defects/dehiscences

• ethmoid cells → frontal sinus + sphenoid.

= universal description of anatomic variations irrespective ot the surgery planned

1. attachment of uncinate processtype A  (lateral)       type B1            type B2 medial 

different configuration of fs outflow tract

LT

How to identify uncinate process attachment ? RT

LT

→

direct drainagevia frontal recess

Rt side type Alateral 

Lt side type Bmedial 

indirect drainagevia ethmoid +hiatus semilunaris→ cor plane

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Ouflow of frontal sinusDistancefrontal beak‐ post wall  

Positionof ethmoid roof

Ouflow of maxillary sinusuncinate process⇔ ostium

position of orbital floor+ Haller cells

narrowostium

wideostium

Anatomic features related to maxillary sinus

lacrimal recessus= surgical route free infraorbital nerve ~ zygomatic recess

accessory ostium 

silent sinus (lt), atelectatic ostium

Underwood septum (sinus lift ) ???

2. position of ethmoid roof ⇔3. course of ant. ethmoid artery

right

left

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Identification ant. ethmoidalis artery : „v“ configuration 2. ethmoid roof⇔ cribriform plateStankiewicz JA, Chow JM. The Low Skull Base: An Invitation to DisasterAmerican Journal of Rhinology 2004; 18 35–40

Keros type 1: 1-3mm 2: 4-7mm 3: 8-16mm

susceptible to injury of ethmoid artery susceptible to injury of ethmoid roof‐ dura 

ethmoid roof⇔ cribriform platemarked asymmetry ~ 7% !

Variation? meningocele, arachnoid herniation? MR exam!

meningo‐encephalocele

34. lamina papyracea ethmoid

Posttraumatic bone intact bony dehiscence (= point 7 checklist) 

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5. optic nerve ⇔ ethmoid/sphenoid sinus

„intrasphenoid optic nerve position

sagittal

?

? = internal carotid artery = point 6 checklist

6. internal carotid artery⇔ sphenoid sinus

bony dehiscence = point 7 checklist

7. osseous defectscommonly w ~ polyposis

agger nasi cell supra agger cell supra agger frontal cell

International Frontal Sinus Anatomy Classification (IFAC) Wormald PJ, Hosemann W, Callejas C, Siow JK, et al. The Internationals Frontal Sinus Anatomy Classification (IFAC) and Classification of the Extent of Endoscopic Frontal Sinus Surgery (FSS). Int Forum Allergy Rhinol. 2016

classifying all  cells as either anterior or posterior or medial8. ethmoid cells: 

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International Frontal Sinus Anatomy Classification (IFAC) 

classifying all  cells as either anterior or posterior or medial or lateral 

Suprabulla cell

Supra bulla frontal cell Frontal septal cell

Supraorbital ethmoid cell (lat.) 

Wormald PJ, Hosemann W, Callejas C, Siow JK, et al. The Internationals Frontal Sinus Anatomy Classification (IFAC)  and Classification of the Extent of Endoscopic Frontal Sinus Surgery (FSS). Int Forum Allergy Rhinol. 2016

Supra bulla cell 95%

49%

25%

89%

27%

28%

9%

Sommer F. et al. European Arch Oto‐Rhino‐Larngol 2019;271:39‐46

Preoperative CT checklist :

• uncinate process √

• ethmoid roof √

• ant. ethmoid artery √

• lamina papyracea √

• optic nerve √

• internal carotid artery √

• osseous defects √

• ethmoid cells → frontal s. √

الحفر من يهاب صعود الجبال يعيش دائما وسطWho is afraid to climb mountains will stay in a hole forever (arab proverb

If you go to the mountain often enough, you will meet the tiger chinese proverb

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