anatomy and relevant anatomical variants in nasal and paranasal sinuses ct scan p. loubeyre 1 md...

Anatomy and relevant anatomical variants in nasal

and paranasal sinuses CT scan

P. Loubeyre1 MD & J.S Lacroix2 MD, PhD1 Radiology Department,

2 Rhinology-Olfactology UnitHôpitaux Universitaires de Genève

CH- 1211 Genève 14Switzerland

CERTIFICATE OFMERIT RSNA 2003

Sinusitis – Imaging technique (3-10)

AnatomyParanasal sinuses (dia 11-12)

Ostiomeatal unit (dia 13-16)

Uncinate process (dia 17-19)

Ethmoid bulla (dia 20-22)

Middle turbinate (dia 23,24)

Ethmoid infundibulum (dia 25)

Frontal recess (dia 26-28)

Sphenoethmoidal recess (dia 29,30)

Posterior nasal fontanel (dia 31)

Posterior choana (dia 32)

Nasal septum (dia 33)

Nasolacrymal duct (dia 34)

Anterior skull base (dia 35-38)

Anatomic variantsSeptal deviation (dia 40)

Septal spurs (dia 41)

Middle turbinate (dia 42-44)

Superior turbinate (dia 45)

Uncinate process (dia 46)

Frontal bulla cell (dia 47)

Frontal sinus extension (dia 48)

Agger nasi cell (dia 49)

Maxillary sinus recesses (dia 50)

Sphenoid sinus recesses (dia 51-53)

Intersinus sphenoid septation (dia 54)

Surgical risksVulnerability of the carotid canal (dia 55-57)

Vulnerability of the optic nerve (dia 58-61)

Vulnerability of the orbit (dia 62-65)

Vulnerability of the nasolacrymal duct (dia 66)

Vulnerability of anterior skull base (dia 67)

Some articles to readMafee MF. Endoscopic sinus surgery: role of the radiologist. AJNR1991;157:855-60Earwaker J. Anatomic variants in sinonasal CT. Radiographics 1993;13:381-415Rao VM, El-Noueam KI. Sinonasal imaging. Radiologic Clinics of North America 1998;36(5):921-39Zeifer B. Update on sinonasal imaging. Neuroimaging Clinics of North America 1998;8(3):607-30

Mucous accumulationincreases the risk of infection or

chronic inflammation

Mucociliary clearance impairment

Mucociliary transport : anatomy of the drainage pathway of the paranasal sinuses

Ostio-meatal complex

Contact of two opposingmucosal surfaces(ex: anatomic variants)

Obstruction

Normal mucosal thickening during nasal cycle

Normal mucociliaryclearance

or

Mucous accumulation

increases risk of infection

The aim of nasal and paranasal sinuses imaging is to provide a The aim of nasal and paranasal sinuses imaging is to provide a

surgical road map delineating the anatomy, defining the obstructive surgical road map delineating the anatomy, defining the obstructive

lesions, and noting the anatomical factors that may predispose lesions, and noting the anatomical factors that may predispose

impaired mucociliary clearance and per operative complicationsimpaired mucociliary clearance and per operative complications

CT CT High spatial resolutionMinute bony details and adjacent soft tissue

structures

Pre-operative investigation for Pre-operative investigation for

patients undergoing patients undergoing

endoscopic sinus surgeryendoscopic sinus surgery

Chronic rhinosinusitis unresponsive to Chronic rhinosinusitis unresponsive to medical managementmedical management

Rhinosinusitis is a medical diagnosis,

not a radiologic diagnosis

Coronal, sagittal or oblique reformationsReal time image-guided anatomic localization during endoscopic surgery

Supine position Confortable position

console

1-mm-thick overlapping axial slices

Nasal lavagesTopical corticosteroidsAntibioticsMucolytic agents CT scan should be CT scan should be

scheduled afterscheduled aftercompletion of medicalcompletion of medicaltreatmenttreatment

Medical treatment should be performed before CT scan

To reduce transient acute inflammatory or To reduce transient acute inflammatory or

infectious mucosal changesinfectious mucosal changes

Contrast-enhanced CT ?

Initial images or clinical symptoms suggest intracranial complications of a chronic inflammatory sinus disease

.Anatomy is adequately assessed without the use of IV injected iodinated contrast material.Iodine injection does not allow for discriminatingan inflammatory disease from a tumoral process

no

yes

MRIMRI

1. Obstruction of the drainage pathways or anatomic variants that may compromise already narrow drainage pathways 2. Identification of critical anatomic areas where anatomic variants pose special risks during sinus surgery

1+2 : Preoperative CT scan as aroad map for endoscopic sinus surgery

CT imagingCT imaging

3. Local extension of disease

4. Complications

Coronal CT

Maxillary sinusesMaxillary sinusesEthmoid sinusEthmoid sinusNasal cavityNasal cavity

Sagittal CT

Frontal sinusesFrontal sinusesEthmoid sinusEthmoid sinusSphenoid sinusSphenoid sinusNasal cavityNasal cavity

Middle nasal meatus(air channel medial to uncinate processand lateral to the middle turbinate)

Ostio-meatal unitOstio-meatal unit

Coronal CT

Sagittal CT

Sagittal view

Ostio-méatal unitOstio-méatal unit

Frontal sinusitisMaxillary sinusitisAnterior ethmoid sinusitis

Drainage from frontal, maxillaryand anterior ethmoid sinuses

ObstructionObstruction

EthmoidEthmoid bulla (EB)bulla (EB)

Axial CT

Coronal CT

Uncinateprocess

Middleturbinate


Middlemeatus

EB

Orbit

Maxillary ostiumEthmoid infundibulum (posterior)Hiatus semilunarisMiddle meatus


Coronal CT

Uncinate processUncinate process

Laminapapyracea

Coronal CT

EB

Supero-anterior attachment to lamina papyracea in 50%

Thin-curved bony lamina of variable height from the lateral side of the ethmoid labyrinth, that forms a portion of the lateral nasal wall.

Inferior attachment to theneck of the inferior turbinate

Postero-lateral attachment to the roof of the maxillary sinus

Uncinate processUncinate process

Sagittal CTCoronal CT

Lacrymal boneLacrymal bone

Uncinate processUncinate processSagittal CT

Anterior-most ethmoid cell:agger nasi cell

EB

Coronal CT

Anterior attachmentof the uncinate process

Ethmoid bulla (EB)Most posterior of all anterior ethmoid air cells, roof of the hiatus semilunaris and posterior ethmoid infundibulum

Anterior ethmoid drainageAnterior ethmoid drainageMiddle meatusMiddle meatus

Sagittal CT

EB

Coronal CT

Anterior ethmoid cells can drain into the middle meatus via the ethmoid bulla

Ethmoid bulla

Normal-sized bullae Large bullae Hypoplasic bullae

Orbit

Uncinateprocess

EB

Acording to John Earwaker. Anatomic variants in sinonasal CT.Radiographics 1993;13:381-415

Coronal CT

Differentethmoidbullae

Middle turbinateMiddle turbinate

It attaches superiorly to thecribriform plate:

Medial lamella

It attaches posteriorly andlaterally to the lamina papyracea:

Basal (ground) lamella

Coronal CT Coronal CT

Bulb

EB

Posteriorethmoid cell

AnteriorAnteriorethmoidethmoid

PosteriorPosteriorethmoidethmoid

Sagittal CT

EB

Coronal CT

Basal lamella

Middle turbinateMiddle turbinate

Anteriorethmoidair cells

Posteriorethmoid air cells

Ethmoid infundibulum

Anterior ethmoid cells drainage

Anterior ethmoid cells can directly drain into middle meatus

Coronal CT

Frontal sinus drainage (25%)Frontal sinus drainage (25%)

Frontal recess

Sagittal CT Coronal CT

Communication between frontal sinus and nasal cavity. Communication between frontal sinus and nasal cavity.

It is not strictly a duct but a channel located between It is not strictly a duct but a channel located between

anterior ethmoid cells. Variety of configurations.anterior ethmoid cells. Variety of configurations.

Anterior middle meatusAnterior middle meatus

Agger nasi cell

Frontal ostiumFrontalsinus

Attachment to the lamina papyraceaAttachment to the lamina papyracea

Frontal drainageFrontal drainage in the medial meatusin the medial meatus

Frontal sinus drainage pathwaysFrontal sinus drainage pathways according to supero-anterior attachment supero-anterior attachment of the uncinate plateof the uncinate plate

Attachment to the skull baseAttachment to the skull base

Frontal drainageFrontal drainage into the ethmoid infundibuluminto the ethmoid infundibulum

50%

25%

Coronal CT

Attachment to the neck of the middle turbinate Attachment to the neck of the middle turbinate

Frontal drainage into the ethmoid infundibulum Frontal drainage into the ethmoid infundibulum

or into an anterior ethmoid cellor into an anterior ethmoid cell

25%

Frontal sinus outflow obstruction

Frontal sinusitis

Sagittal view

Sphenoethmoidal recessPosterior ethmoid and sphenoid sinus drainagesPosterior ethmoid and sphenoid sinus drainages

Superior nasal meatus

Sphenoid sinusostium

Axial CT Sagittal CT

Sphenoidsinus

Posterior ethmoid sinusitisSphenoid sinus sinusitis

Sphenoethmoidal recess obstruction

Posterior nasal fontanel

Area of the lateral wall of the nose immediately behind the posteriorattachment of the uncinate plate. Consists of mucous membrane only, without bony support.

Accessory maxillary ostium is frequently found through theposterior nasal fontanel (15-40%)

coronal

Axial CT

Coronal CT

Posterior choana

Coronal CTSagittal CT

Nasopharynx

Nasal septum

Perpendicular plateof the ethmoid

Septal Septal cartilagecartilagevomer

antpost

Coronal CT

Chondrovomeral junction

Sagittal view

Nasolacrymal duct

1 2

3

Inferior Inferior meatusmeatus

4

Axial CT

CoronalCT

Anterior skull base

Coronal CT

Crista galliCribriform plates Cribriform plates (floor of the olfactive fossa)(floor of the olfactive fossa) Ethmoid roof (fovea ethmoidalis) Ethmoid roof (fovea ethmoidalis)

Axial CT

Ethmoid roofEthmoid roof

Sagittal CTAxial CT

Lateral lamellaLateral lamella(point of structural weakness in (point of structural weakness in the anterior skull base)the anterior skull base)

Dehiscent in 15% of specimensDehiscent in 15% of specimens

Point of structural weakness duringturbinectomy

1-16 mm length1-16 mm length

Middleturbinate

Coronal CT

Mediallamella

Anterior ethmoidal artery

Cribriform plateCribriform plate

Ethmoid roofEthmoid roof

Anterior ethmoidal artery

Olfactoryfossa

The anterior ethmoidal artery - branch of the ophtalmic artery - exits the orbit through the anterior ethmoidal foramen and enters the olfactory fossa at the point of attachment of the middle turbinate to the cribriform plate

Lateral lamellaLateral lamella

Medial lamella ofMiddle turbinate


Very frequently notedVery frequently noted

The presence of anatomic variants, singly or in The presence of anatomic variants, singly or in

combination, does not represent a disease state per secombination, does not represent a disease state per se

Equal prevalence of patients with and without sinus Equal prevalence of patients with and without sinus

disease in the presence of the same anatomic variantdisease in the presence of the same anatomic variant

Anatomic variantsAnatomic variants

Septal deviation

Middle meatusInferior meatus

Largemiddleturbinate

Hypoplasicmiddleturbinate


Septal spurs

May impige on and invaginate the middle or inferior turbinates. When the May impige on and invaginate the middle or inferior turbinates. When the turbinate mucosa swells with the normal nasal cycle or inflammation, it is turbinate mucosa swells with the normal nasal cycle or inflammation, it is impaled on the spur, setting up a cycle of facial pain or headache. A septal impaled on the spur, setting up a cycle of facial pain or headache. A septal spur occasionally produces a complete bridge. spur occasionally produces a complete bridge.

Frequently encountered at the junction of the perpendicular plate of the ethmoid and the vomer

Coronal CTAxial CT

Coronal CT

Bridging spur

Size variations of middle turbinate

Ostio-méatal complex compromise?Ostio-méatal complex compromise?Turbinate septal contact when the turbinate mucosa Turbinate septal contact when the turbinate mucosa swells with the normal nasal cycle or inflammationswells with the normal nasal cycle or inflammation


Pneumatized middle turbinate

Air cell in the bulbous segment: concha bullosa cell

Air cell in the vertical lamella: concha neck air cell

Axial CTCoronal CT

Paradoxical middle turbinate

UsuallyUsuallyConvex configuration medially

Concave configuration laterally

Paradoxical turbinate Paradoxical turbinate Concave configuration medially

Convexe configuration laterally

Coronal CT

Pneumatized superior turbinate

A cause of migraine headache?Enlargement of the superior turbinate due to pneumatization, with accompanying mucosal contact, acts as a mechanical stimulus initiating an axon reflex with resultant referred pain?

Coronal CT

Uncinate process

Pneumatized

Medially rotated uncinate

Coronal CT

Coronal CT

Height : 1-4 mmLength : 14-22 mm

Frontal bulla cell (suprabullar cell) Anterior ethmoid air cell extending upwards (intramural ethmoid air cell)

May be small and impiges only on the floor of the frontal sinus.

May elevate and narrows the frontal recess

May be prominent and bulges into the frontal sinus

sagittal axial coronalFrontal recess

Frontal sinus extensionPneumatization of the orbital plate of the frontal bone

No frontal sinus drainage compromise

Frontal sinus

ant post

Coronal CT

Agger nasi (AN) cellAgger nasi (AN) cell

The most anterior of the ethmoid cells. Forms the floor of the frontal The most anterior of the ethmoid cells. Forms the floor of the frontal recess. It reaches the lacrimal fossa inferiolaterally, and is recess. It reaches the lacrimal fossa inferiolaterally, and is anterolaterally arched by the nasal bone. A large agger nasi can impige onanterolaterally arched by the nasal bone. A large agger nasi can impige onand distort the frontal recess.and distort the frontal recess.

Frontal recess

Sagittal CT

Coronal CT

Its posterior-medial wall usually gives rise to the anterior uncinate process

Lacrymalfossa

AN

Coronal CT

Coronal CT Sagittal CT

Alveolar recesses(roots of the premolar and molar teeth)

Maxillary sinus recesses

Palatine recess

Infraorbital recess ofThe maxillary sinus

Axial CT

Zygomatic recess

Axial CT

Sphenoid sinus recesses

antpost Sphenoid

sinus

RostrumRostrumSeptum, vomerSeptum, vomerSup or inf clivusSup or inf clivusLesser wingLesser wingGreater wingGreater wingPterygoid processPterygoid process

TemporalTemporalbonebone

Maxillarybone

Orbitalwall

Sphenoid sinus

Coronal anterior viewSagittal view

Inferior clival recess

Sagittal CT Sagittal CT

Septal recess


Lesser wing

Greater wing

Ptérygoid process

Anterior clinoid process

Foramen rotundum(maxillairy nerve)

Optic nerve

Coronal CT

Coronal CT


Intersinus septation of sphenoid

Presellar segment of the internal carotid artery

Axial CTCoronal CT

Vulnerability of the carotid canalVulnerability of the carotid canal

Axial CTAxial CT

Internal carotid artery bulges into sphenoid sinus

septum

Sphenoid Sphenoid sinus sinus surgerysurgery


Dehiscent carotid canal

Axial CT Axial CTSphenoid Sphenoid sinus sinus surgerysurgery

Hypoplasia or aplasia of the sphenoid sinusCarotid canal impiges on or bulges into posterior ethmoid


Ethmoid

Normalsphenoidsinus

ETHMOIDEPOST

Normal sphenoidsinus

Axial CTPosteriorPosteriorethmoid ethmoid surgerysurgery

Vulnerability of the optic nerveVulnerability of the optic nerve

1 Onodi cell (bulging of the optic canal into the posterior ethmoid)

2 Pneumatization of the lesser wing of the sphenoid bone

3 Pneumatization of the anterior clinoid process of the sphenoid bone

Sagittal CT


Optic nervesOptic nerves

12 3

Encasement of the optic nerveWithin the sphenoid sinus

PosteriorPosteriorethmoid ethmoid surgerysurgery

SphenoidSphenoidsinus sinus surgerysurgery


Onodi cell

Posterior ethmoid cell, with prominent superior or lateral pneumatization to the sphenoid sinus, and a bulge of the optic optic canalcanal into it.

Axial CT

Sagittal CT

Coronal CT

Sinussphénoide




Coronal CT

Axial CT

11 22

22

1. Bulging of the optic nerve into the sphenoid sinus2. Dehiscent optic canal




Normal-sizedsphenoid sinus

mt

Postethmoid

Sagittal view

Hypoplasia or aplasia of the sphenoid sinus (Optic nerves impinge on or bulge into the posterior ethmoid)

mt

Optic nerve

mt

mt: middle turbinate


Vulnerability of the orbitVulnerability of the orbit

Anterior ethmoid air cells that extend along the medial floor of the orbit

Coronal CT

Haller cells

AnteriorAnteriorethmoid ethmoid endoscopyendoscopy

Axial CT

Uncinate process is very close to infero-medial orbit wall. They can be merged.

Coronal CT

orbitorbite


UncinectomyUncinectomy

Lamina papyracea localized medial to the maxillary sinus ostium

Coronal CT

(Ex :maxillary sinus hypoplasia;reduced ethmoid transverse diameter;children)

Fusion of the uncinate process to theFusion of the uncinate process to themedial orbital wall medial orbital wall (usually associated with ipsilateral hypoplastic maxillary sinus)

orbit

Coronal CT


Dehiscent laminapapyracea

Thin medial orbital wall(lamina papyracea)

Coronal CT Axial CT Axial CT

coronal



Dehiscent laminapapyracea

Agger nasi cell can invade the lacrymal boneand impinge on or encircle thethe nasolacrymal ductnasolacrymal duct

Axial CT

Coronal CT

Vulnerability of the nasolacrymal ductVulnerability of the nasolacrymal duct


Usually associated withUsually associated withhypoplastic middle turbinate(s)

orbit

Coronal CT

Low cribriform plate: below the upper third of the verticalorbital plate

Risk of penetration into theRisk of penetration into theanterior cranial fossa anterior cranial fossa duringduringethmoid endoscopic surgeryethmoid endoscopic surgery

Vulnerability of the anterior skull baseVulnerability of the anterior skull base

anatomy and relevant anatomical variants in nasal and paranasal sinuses ct scan p. loubeyre 1 md...

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orbit dia

nasal septum dia

frontal recess dia

middle turbinate dia

uncinate process dia

superior turbinate dia

ethmoid bulla dia

nasolacrymal duct dia