Sinonasal CT: The basics

anatomy of the paranasal sinusesLuc van den Hauwe1,2 , Simon Nicolay1

Johan W. Van Goethem1, Paul M. Parizel ex1

Depts. of Radiology,Antwerp University Hospital-University of Antwerp, Antwerp/BE

AZ KLINA, Brasschaat/BE

[email protected]

outline

introductionimaging: why, when, and how?normal anatomy– basic anatomy– anatomy in rhinosinusitis– anatomy in the pre-operative setting

take home messages – structured CT report

introduction

introduction - paranasal sinusespaired air-containing spaces, left and rightin the bony structures of the skull (os frontale and sphenoidale) and facial bones (os ethmoidale and maxilla)surrounding the nasal cavity

mucosapseudostratified columnar epitheliumciliated epithelial cells

brush-like projections continually sweep in a beating motion and clear mucus from the sinus chamber through the ostium into the nasal cavity

muco-ciliary clearancemucus is moved from the sinuses to the choanae

according to their drainage pathway, the sinuses may be functionally classified into two subgroups– anterior group:

• anterior ethmoid cells, frontal sinus, maxillary sinus

– posterior group:• posterior ethmoid cells,

sphenoid sinus

introduction - sinusitisacute sinusitis: – < 4 weeks

clinical diagnosis:– fever– headache– postnasal discharge of

thick sputum– nasal congestion– abnormal sense of smell

no imaging needed, unless complications– imaging findings are

nonspecific and can be seen in a large number of asymptomatic patients

imaging: why, when, and how?

imaging: why, when, and how?to confirm the clinical diagnosisto evaluate the extent and localization of the disease: pattern

to describe anatomic variants– that may incite rhinosinusitis– that may raise the risks of endoscopic surgery

to rule out other (tumoral) pathology

to select patients that may benefit from sinus surgery


plain film

CT– standard CT– low-dose CT– cone-beam CT: CBCT

MRI

plain film

simple and quickeasy accesslow-costradiation: low?different projections– lateral view– Water’s view: occipitomental view– Caldwell view: occipitofrontal view– (Hirtz view: submentovertex view)

plain film

plain film

simple and quickeasy accesslow-costradiation: low?different projections– lateral view– Water’s view: occipitomental view– Caldwell view: occipitofrontal view– (Hirtz view: submentovertex view)

usually not appropriate according to the ACR criteria (1)

CT

comparable radiation exposure (low-dose)higher sensitivity and specificityindications– patients who do not respond to medical treatment– chronic/recurrent sinusitis– pre-FESS work-up– complications of sinusitis (MRI)

MDCT

1 4 8 16 64 256 320

multidetector CT

aka multislice CT, spiral CT, helical CT, volume scanning, …

slipring technology, fast computers

3D volumes scanned

– reconstructions in all desired planes

– 3D reconstructions

MDCTDCCTTMM

computer assisted surgery (CAS)

radiation issues – effective dose

plain film: 0.098 mSv‘normal’ or ‘standard’ CT: 0.371 mSvlow-dose CT: 0.045 mSvCBCT: 0.025 mSv

cone-beam CTcone

slice thickness: 0.125 mm; spatial resolution: 125 μm

indications for MR imaging

complications of sinusitis– intracranial– intra-orbital

suspicion of non-infectious lesions– benign lesions

• fibro-osseous lesions• inverted papilloma• …

– malignant tumors

indications for MR imaging

complications of sinusitis– intracranial– intra-orbital

suspicion of non-infectious lesions– benign lesions

• fibro-osseous lesions• inverted papilloma• …

– malignant tumors

inflammatory changes vs tumor

CAVE: unilateral disease: obstructing mass?!

inflammatory changes vs tumor

CAVE: unilateral disease: obstructing mass?!


acute rhinosinusitis


acute rhinosinusitis - complications


chronic or recurrent rhinosinusitis


pre-operative setting

invasive fungal rhinosinusitis


plain film

CT– standard CT– low-dose CT– cone-beam CT: CBCT

MRI

indications?

mainstay of investigationin inflammatory disease

problem-solving tool complications

R/O tumoral pathology

normal anatomy normal anatomy

• basic anatomy• anatomy in rhinosinusitis• pre-operative anatomy

1. basic anatomy

1. nasal cavity

2. maxillary sinus

3. frontal sinus

4. sphenoid sinus

5. ethmoid air cells

nasal cavityinhaled air:

humidify

heat

filter

mucosa

nasal cavity: mucosa inhaled air:

humidify

heat

filter

nasal cavity – turbinates*inhaled air: regulate airflow

humidify

heat

filter

*aka conchae nasalis

nasal cavity – turbinates*inhaled air: regulate airflow

humidify

heat

filter

*aka conchae nasalis

nasal cavity - turbinates• inferior turbinate

inferior meatus• middle turbinate

middle meatus• superior turbinate

superior meatus



middle meatussuperior turbinate

superior meatus




superior meatus




superior meatus

nasolacrimal duct




superior meatusant group of sinuses




superior meatuspost group of sinuses




superior meatusant group of sinuses

nasolacrimal duct

post group of sinuses

drainage pathways

• ostiomeatal complex (OMC)

• frontal recess

• spheno-ethmoid recess

anterior vs posterior ethmoid?

middle turbinatebasal lamella

anterior vs posterior ethmoid?

anteriorethmoid air cells

middle turbinatebasal lamella

posterior ethmoid air cells

2. anatomy in rhinosinusitis

5 patterns of rhinosinusitis 5 patterns of rhinosinusitis

1. spheno-ethmoid pattern2. infundibular pattern3. ostiomeatal pattern4. nasal polyposis5. sporadic pattern

5 patterns of rhinosinusitis

1. spheno-ethmoid pattern

drainage pathways

sphenoid sinus posterior ethmoid

spheno-ethmoid recess

superior meatus

drainage pathways



superior meatus

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drainage pathways



superior meatus

spheno-ethmoidpattern

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1. spheno-ethmoid pattern2. infundibular pattern

drainage pathways

maxillary sinus

(ethmoid) infundibulum

middle meatus

drainage pathways

maxillary sinus


middle meatus

y

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infundibular pattern

drainage pathways

maxillary sinus


middle meatus

y

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infundibular pattern

drainage pathways

frontal sinus

frontal recess

middle meatus

drainage pathways

frontal sinus

frontal recess

middle meatus

drainage pathways

frontal sinus

frontal recess

middle meatus

drainage pathways

anterior ethmoid air cells

ethmoid bulla

middle meatus

drainage pathways

anterior ethmoid air cells

ethmoid bulla

middle meatus

drainage pathways

anterior ethmoid

ethmoid bulla

middle meatus

maxillary sinus frontal sinus

ethmoidinfundibulum

frontal recess

drainage pathways

anterior ethmoid

ostiomeatal complex

middle meatus


drainage pathways

anterior ethmoid

ostiomeatal complex

middle meatus


1. maxillary ostium2. ethmoid infundibulum3. hiatus semilunaris4. middle meatus5. uncinate process6. ethmoid bulla7. frontal recess

1

2

3

4

5

6

7

1

2

3

4

5

6

7


drainage pathways

anterior ethmoid

ostiomeatal complex

middle meatus



drainage pathways

anterior ethmoid

ostiomeatal complex

middle meatus



1. spheno-ethmoid pattern2. infundibular pattern3. ostiomeatal pattern


1. spheno-ethmoid pattern2. infundibular pattern sinus outflow problem3. ostiomeatal pattern


1. spheno-ethmoid pattern2. infundibular pattern3. ostiomeatal pattern4. sinonasal polyposis

sinonasal polyposis

inflammatory polyp formation:

sinonasal polyposis

inflammatory polyp formation:– middle turbinate– uncinate process– ethmoid infundibulum

OMC !ostiomeatal pattern

bilateral


1. spheno-ethmoid pattern2. infundibular pattern3. ostiomeatal pattern4. nasal polyposis5. sporadic pattern

sporadic pattern

mucosal thickeningretention cystsantrochoanal polypsilent sinus syndromeodontogenic sinusitismucocele

mucosal thickening

normal limits:maxillaryethmoid air cellsfrontal sinus: 0 mmsphenoid sinus: 0 mm

retention cysts

no clinical significanceunless sinus outflow problem

mucocele• sinus cavity:

– fully opacified– drainage obstruction– persisting mucus production

• sinus expansion• bone remodelling

rhinosinusitis – CT report rhinosinusitis CT report

1. mucosal thickening – inflammation - polyps?2. acute?3. pattern?4. fluid density?5. calcifications?6. bone?

fluid density & calcifications

high density:• chronic sinusitis• fungus

fluid density & calcifications

high density:• chronic sinusitis• fungus

calcifications:• fungus (ball) – mycetoma• odontogenic material

bone

chronic inflammation

osteitis - bone thickening3. anatomy in the pre-operative setting

Functional Endoscopic Sinus Surgery (FESS)fathers of FESSWalter Messerklinger & Heinz Stammberger, Graz/AT

Storz, endoscopy

Functional Endoscopic Sinus Surgery (FESS)


FESS targets:1. OMC2. (frontal recess)


Functional Endoscopic Sinus Surgery (FESS) Functional Endoscopic Sinus Surgery (FESS)

1

1. uncinectomy + antrostomy


12

1. uncinectomy + antrostomy2. conchectomy3. ethmoidectomy


1. uncinectomy + antrostomy2. conchectomy3. ethmoidectomy

3

111112

1


4. frontal sinusotomy

4

pre-operative CT report

anatomical variants1. narrow/obstruct sinus outflow tracts

- ostiomeatal complex (OMC)- frontal recess

2. increase the risk of surgical complications (FESS)


anatomical variants:1. narrow/obstruct sinus outflow tractsmay impair the OMC outflow

adherent uncinate process& maxillary atelectasis

from: O’Brien WT et al. Radiology 2016; 281:10-21


anatomical variants:1. narrow/obstruct sinus outflow tractsmay impair the OMC outflow

septaldeviation/spurring

concha bullosa Haller cell paradoxicalconcha media


anatomical variants:1. narrow/obstruct sinus outflow tractsmay impair the frontal recess

A

agger nasi cell 1 cell above ANC type 1 type 2

1 cell above ANC,into frontal sinus

type 3

frontoethmoidal cells (Kuhn)frontal recess cells


anatomical variants1. narrow/obstruct sinus outflow tracts

- ostiomeatal complex (OMC)- frontal recess

2. increase the risk of surgical complications (FESS)

O’Brien WT et al. Radiology 2016; 281:10-21


Cribriform plateLamina papyraceaOnodi cellSphenoid pneumatisationEthmoidal artery (anterior)


cribriform plate

1. cribriform plate2. lateral lamella3. fovea ethmoidalis4. crista galli

3

21

4


cribriform plate


depth of the olfactory fossa

II : 4-7 mm

3

21

4

Keros

cribriform plate


depth of the olfactory fossa

II : 4-7 mm

3

21

4

risk injurylateral lamella:CSF leak

cribriform plate• asymmetry!• fovea ethmoidalis position

1. normal• ± horizontal• above upper orbit

2. at risk• ± vertical slope• ½ orbit

lamina papyracea


lamina papyracea

injury may lead to:1. orbital infection2. medial rectus injury3. orbital hematoma

loss of vision!!!

lamina papyracea

check for:• integrity (previous trauma)

lamina papyracea

check for:• integrity (previous trauma)• adherent uncinate process


Onodi cell

normal sphenoidal sinus:• no horizontal septum• no air cells above

sphenoid sinus


Onodi cell

variant posterior ethmoidalair cell• superior of the sphenoid sinus• horizontal septum• CN II dehiscence

CN II CN II

SS


sphenoid sinus pneumatization



optic nerve

ICA

V2

vidian nerve

sphenoid sinus pneumatization sphenoid sinus pneumatization

conchal type presellar type sellar type




ICA dehiscence optic nerve dehiscence septation to ICA canal


vidian canal dehiscence CN V2 dehiscence

(anterior) ethmoidal artery

ophthalmic artery

anterior ethmoidal artery



ophthalmic artery


notch


ophthalmic artery


notch

fovea ethmoidalis


ophthalmic artery


supraorbital pneumatization = risk factor

notch


ophthalmic artery



notch


ophthalmic artery



notch

take home messages

structured CT report


hypoplasia

OMC & FR leftant. sinuses

OMC & FR rightant. sinuses

SERpost. sinuses

nasal cavityseptum & turbinates

C

L

O

S

E

other

impressions



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