Sinonasal Anatomy

– Development of the maxillary sinus begins with the invagination of the middle meatus. – Uncinate process & the bulla ethmoidalis form a narrow groove : hiatus semilunaris
Ethmoidal sinuses and lateral nasal wall
• Bulla ethmoidalis
– – – – Largest ant. ethmoid air cell Lat.：lamina papyracea Post.： basal lamella Sup.：roof of the ethmoid
• Ant. ethmoid artery
– The weakest portion :
• Enters the anterior cranial fossa through the lateral lamella .
– 1/10 as strong as the roof.
Very near skull base at the junction of ethmoid roof & posterior border of frontal recess.
– Post. end of superior meatus. – Draining the posterior ethmoid & sphenoid sinuses separately,
Ethmoidal sinuses and lateral nasal wall
• Ant. ethmoid sinus, maxillary sinus, & frontal sinus
Maxillary Sinus
• Within maxillary bone • Largest
– – – – – Ant：facial surface Post：infratemporal fossa Medial：lateral wall of nasal cavity Floor：the alveolar process Superior：Orbital floor
• Frontal recess：
– Drains the frontal sinus
• Sinus lateralis：
– retrobullar recess – Exists if the post. wall of the bulla ethmoidalis doesn’t contact basal lamella.
• Form the posterior wall of frontal recess.
• Minimal or absent pneumatization of the ethmoid bulla
– 8% of individuals
Ethmoidal sinuses and lateral nasal wall
• Haller cell：
– Pneumatizes laterally – Between maxillary sinus & floor of the orbital – Potentially impairing sinus drainage.
– Nasal cavity and nasopharynx oral cavity and oropharynx.
• Descending septum merges with the fused palate
– Two nasal cavities .
• Fusion failure
– Cleft lip or palate deformity. – Extend into the nose
• Posterior：sphenoid • Superior：
– Skull base of ant. cranial fossa
Ethmoidal sinuses and lateral nasal wall
• Midline vertical plate
– In the anterior cranial fossa
– Type 2：4-7mm – Type 3：8-16mm
• Lower cribriform
– Greatest risk for CSF leak during FESS
Ethmoidal sinuses and lateral nasal wall
• From anterior to posterior
• Fully develop：
– Ethmoid -> Maxillary -> Sphenoid -> Frontal sinuses.
Anatomy
Ethmoidal sinuses and lateral nasal wall
• Central structures of nose with complex anatomy
• 4-8th weeks：
– As frontonasal & maxillary processes join. – Develops separate nasal cavities
Embryology
• Upper maxilla & philtrum of the upper lip.
– Fusion of medial prominence with the maxillary process
• Thicker, more lateral
– Anterior cranial fossa ethmoid
Ethmoidal sinuses and lateral nasal wall
• Lateral lamella of the plate,
– Thinnest bone in the skull base. – Length
Sinonasal Anatomy
Embryology
• Embryo’s head
• Structure with two distinct nasal cavities.
• Lateral nasal walls
• Create complex folds
• Turbinates & sinuses.
– – – – – Uncinate process Bulla ethmoidalis Basal / (Ground) lamella Superior turbinate Supreme turbinate
• The aeration projects anterior to the attachment of the middie T.
• Box-like structure with open anterior & inferior faces.
Ethmoidal sinuses and lateral nasal wall
• Lateral：Lamina papyracea
– the medial walls of the orbits
• Basal lamella
– Dividing line :
• Ant. post. ethmoid sinus.
– Inf.：connects the middle T. to the lateral wall stabilize
Ethmoidal sinuses and lateral nasal wall
• Posterior ethmoid cell
– Larger – Onodi cell : developmental variant
• 9% to 12% • Exposure the optic nerve within the ethmoid sinus lumen.
Four recesses
• Position of the cribriform plate ethmoid roof.
Ethmoidal sinuses and lateral nasal wall
• Keros type skull base
– Type 1：
• Cribriform plate 1 ~ 3 mm below fovea ethmoidalis, • Making the lateral lamella short or nonexistent.
• Septum:
– Posterior midline growth of the frontonasal process – mesoderm from the maxillary processes.
Embryology
• Primary & secondary palatal shelves
– Agger nasi cells
Ethmoidal sinuses and lateral nasal wall
• Uncinate process：
– L-shaped bone – AS to PI direction. – Posterosuperior margin：
• Paralle to the inferior border of the bulla ethmoidalis
– Posterior
• Palatine bone and the Inf. T.
– Superior：
• Lamina papyracea : most commonly • Also attach to agger nasi cell, the skull base, or the middle T.