ANATOMY OF CRANIAL BASE & NASAL CAVITIES.

Endoscopic Endonasal Removal of Pituitary Tumors.

MS: Milad Basim

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CRANIAL CAVITY:

The cranial cavity is the space within the cranium that contains the brain, meninges, proximal parts of the cranial nerves, blood vessels, and cranial venous sinuses.

CRANIAL BASE (FLOOR):

The skull base forms the floor of the cranial cavity and separates the brain from other facial structures.

The 5 bones that make up the skull base are the Ethmoid. Sphenoid. Occipital. paired frontal. paired temporal bones.

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CRANIAL FOSSA: The cranial base is divided into the following three cranial fossae, with each having numerous foramina (openings) for structures to pass in or out of the neurocranium.

Anterior cranial fossa.

Middle cranial fossa.

Posterior cranial fossa.

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Anterior cranial fossa:composes the roof of the orbits, and accommodates the frontal lobes of the brain (right and left).

Formed by:• orbital plate of the frontal bone.• cribiform plate of ethmoid bone.• lesser wings of the sphenoid bone.

Boundaries:• Anteriorly: posterior wall of frontal sinus• Posteriorly: roof of splenoid sinus• Laterally: frontal bone (paired, both sides)• Centrally: eithmoid bone

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“Anterior cranial fossa and their structures”

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Middle cranial fossa:accommodates the temporal lobes of the brain.

The petro-occipital fissure subdivides the middle cranial fossa into 1 central component and 2 lateral components.

Boundaries:• Anteriorly: Greater wing of sphenoid bone.• Posteriorly: superior borders of petrous part of temporal.• Laterally: squamous part of temporal and some part if parietal

and greater wings of sphenoid.• Centrally: sella tursica (or sella turcica) of body of sphenoid.

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Middle cranial fossa and their structures

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Posterior cranial fossa:accommodates the cerebellum, pons, and medulla oblongata of the brain (occipital lobes).

Boundaries:• Anteriorly: superior border of the petrous part of temporal

bone.• Posteriorly: lesser part of the occipital squamous.• Laterally: Temporal & parietal bone.• Floor: Occipital bone.• Centrally: Foramen magnum.

The anterior cranial fossa is separated from the middle cranial fossa by the lesser wing of the sphenoid, and the middle cranial fossa is separated from the posterior cranial fossa by the petrous part of the temporal bone.

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Posterior cranial fossa and their structures

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NASAL CAVITIES:The nasal cavities extend from the anterior apertures (nares) to the posterior apertures (choanae).

The nasal cavities are separated:• from each other by a midline nasal septum.• from the oral cavity below by the hard palate.• from the cranial cavity above by parts of the frontal,

ethmoid, and sphenoid bones.

Each nasal cavity has: Floor. roof. medial wall. lateral wall.

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Nasal cavities (anterolateral view). Relationship to other cavities.

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Roof:

Formed by:

•Body of sphenoid.•Cribriform plate of ethmoid bone.•Frontal bone.•Nasal bone & cartilage.•vomer.

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Floor:

Formed by the hard palate (palatine process of the maxilla, and the horizontal plate of the palatine bone )

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Medial Wall (Nasal Septum):

Formed by:• Superiorly by the vertical (perpendicular)plate of ethmoid bone.• Posteriorly by the vomer bone.• Anteriorly by the septal cartilage.

• small contributions by frontal, palatine, sphenoid and maxillary bones.

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Lateral wall:The lateral wall of each nasal cavity is complex and is formed by bone, cartilage, and soft tissues.

Bony support for the lateral wall is provided by: the ethmoidal labyrinth and uncinate process. the perpendicular plate of the palatine bone. the medial plate of the pterygoid process of the sphenoid bone. the medial surfaces of thelacrimal bones and maxillae. the inferior concha.

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Lateral wall:The lateral wall is characterized by three curved shelves of bone (conchae), which are one above the other and project medially and inferiorly across the nasal cavity.

The conchae divide each nasal cavity into four air channels: an inferior nasal meatus between the inferior concha and the

nasal floor. a middle nasal meatus between the inferior and middle concha. a superior nasal meatus between the middle and superior

concha. a spheno-ethmoidal recess between the superior concha and the

nasal roof.

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Floor, roof, and lateral walls.Conchae on lateral walls.

The superior and middle conchae are parts of the ethmoid bone, whereas the inferior concha is a separate bone.

The conchae increase the surface area of the nasal cavity

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The recess & meati receive the openings of the:Paranasal sinuses.Nasolacrimal duct.

Sphenoethmoidal recess: Receives the opening of the sphenoidal sinus.

Superior meatus: Receives the opening of the posterior ethmoidal sinus.

Inferior meatus: Receives the opening of the nasolacrimal duct. The opening is guarded by a valve, a fold of mucous membrane

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Middle meatus:

•Shows a rounded eminence, the ethmoidal bulla, caused by the bulging of the underlying middle ethmoidal sinus, which opens on its upper border.

•A curved groove, hiatus semilunaris, lies below the bulla. Hiatus receives the opening of the maxillary sinus.

•Anterior end of hiatus leads to funnel-shaped infundibulum, which receives the openings of the frontal & the anterior ethmoidal sinuses.

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Paranasal sinuses and meatuses

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Regions of the nasal cavities

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Gateways to the nasal cavities

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Blood Supply and Innervation

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Endoscopic Endonasal Removal of Pituitary Tumors:

The endoscopic endonasal transsphenoidal procedure is a new and

minimally invasive approach for the resection of pituitary tumors.

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Who is Dr. Moreland ?

Dr. Moreland has pioneered this technique both locally and internationally. He has one of the largest series in the country utilizing this procedure.

Benefits of endonasal endoscopic surgery:

Results in less pain and a faster recovery than traditional surgery. Does not leave a visible scar on the face or scalp. Allows the patient to start radiation therapy, if needed, almost

immediately, without waiting for incisions to heal.

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Procedure:The procedure involves passing a 4mm rigid endoscope into the nostril to provide illumination and visualization. No incision is made nor is it necessary to break the nose with this new technique. Both of these maneuvers are necessary with the older traditional approach and they are a great source of pain and longer hospital stays. The sphenoid sinus and pituitary fossa are then entered using microsurgical instruments. The anatomy as seen by the endoscope is projected onto a television monitor as the surgeon resects the tumor.

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Sources:

imueos.wordpress.comGray’s anatomy bookNether’s clinical anatomy bookwww.hopkinsmedicine.orgbuffaloneuro.comFrom others presentations

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Thank you for your attention

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