Skull & Cranial Vault

Question 1

What is the pterion?

What is its clinical significance?

Answer 1

H-shaped suture between the frontal, parietal, sphenoid & temporal bones

Bone here is thin & susceptible to fracture
Anterior division of the middle meningeal artery grooves it, thus a blow to the petrion can rupture the artery - leading to extradural haematoma

Question 2

What are important cranial sutures?

Answer 2

Coronal - frontal & parietal bones in coronal plane
Sagittal suture - left & right parietal bones
Lamboid - coronal plane, occipital & parietal bones

Question 3

What are the important parts of the temporal bone?

Answer 3

Squamous - anterior & superior flat part of the bone which articulates with sphenoid & parietal bone

Mastoid process - thick, inferior & posterior projection - full of air cells

Styloid process - thin projection from lower medial border - attachment for structures in oropharynx

Zygomatic process - projects laterally & then anteriorly to articulate with the zygomatic bone to form the zygomatic arch

Petrosus part - inward wedge shaped

Question 4

What are features of the occipital bone?

Answer 4

Superior & inferior nucal lines

External occipital protuberance - important land mark, i.e. occipitofrontalis attaches here

Question 5

What are important features of the sphenoid bone?

What separates its greater & lesser wings?

Answer 5

Centrally (within the body) contains the turkish saddle (sella turcica) - where the pituitary gland sits

The greater & lesser wings are separated by the superior orbital fissure

Question 6

What bones make up the anterior cranial fossa?
What lobe of the brain sits in it?
What foramina are found here?

Answer 6

Frontal bone + lesser wing of sphenoid bone + cribiform plate of ethmoid bone

Ventral side of the frontal lobe

Cribiform plate - formaina for projections of olfactory bulb

Only olfactory foramina

Question 7

What bones make up the middle cranial fossa?
What lobe of the brain sits in it?
What foramina are found here?

Answer 7

Greater wing & body of sphenoid + Temporal bone (petrous part - forms border with posterior fossa)

Temporal pole

Superior orbital fissure, orbital canal
Foramen rotundum, ovale & spinosum

Foramina for eye structures + trigeminal divisions & MMA

Question 8

What bones make up the Posterior cranial fossa?
What lobe of the brain sits in it?
What foramina are found here?

Answer 8

Occipital bone (+ part of petrus bone as it forms the border b/w middle & posterior fossa)

Occipital lobe and cerebellum

Foramen magnum (occipital bone)
Hypoglossal canal (occipital bone)
Jugular foramen (between occipital & petrous)
Internal acoustic meatus (petrous part of temporal bone) - DROPS DOWN INTO POSTERIOR FOSSA

Question 9

What is significant about the petrous part of the temporal bone?

Answer 9

Inward, wedge shaped projection making up part of the middle cranial fossa
Contains internal acoustic meatus

Question 10

What structure exits through the cribiform plate?

Answer 10

Afferents from olfactory bulb
CN 1 (olfactory nerve)

Question 11

What structure exits through the superior orbital fissure?

Answer 11

CN3 (occulomotor), CN4 (trochlear), CN5 V1 (opthalmic division of trigeminal) & CN6 (abducens)

All NERVES to the eye (muscles) except optic nerve

Question 12

What structure exits through the optic canal?

Answer 12

CN1 (optic nerve) + opthalmic artery

Nerve + artery to actual EYEBALL

Question 13

What structure exits through the hypoglossal canal?

Answer 13

CN 12 (hypoglossal)

Question 14

What structure exits through the jugular foramen?

Answer 14

CN 9 (glossopharyngeal) , 10 (vagus), 11 (Spinal accessory) 
& internal jugular vein

Question 15

What structure exits through the foramen magnus?

Answer 15

Spinal cord

CN11 (spinal accessory) ENTRES (exists via jugular foramen)

Question 16

What structure exits through the internal auditory meatus?

Answer 16

CN VII (facial) ENTRES + CN VIII (vestibulocochlear)

Question 17

What foramina & canals doesCN VII pass through?

Answer 17

Enters petrousal part of temporal bone at internal acoustic meatus, passes through facial canal, exits through stylomastoid canal

Question 18

What structure exits through the foramen rotundum, ovale & spinosum?

Answer 18

Rotundum - CN5 V1 (maxillary division)
Ovale - CN5 V2 (mandibular division)
Spinosum - middle meningeal artery

Question 19

What fossa within which part of a cranial bone does the pituitary gland sit?

Answer 19

Hypophysial fossa - within the salle turcica of the body of the sphenoid bone

Question 20

Dura Mater

What are their general features?
What potential space do they create?
What can collect in these spaces?

Answer 20

• Touch, fibrous outer meningeal layer
• Has two components - periosteal (adherent to skull) & meningeal (close contact with arachnoid mater & continuous with dura of spinal cord)
• Creates the extradural space (between skull & meningeal dura layer) + subdural space (between menigeal dura & arachnoid mater)
• Extradural - blood from meningeal artery i.e. extradural haematoma
• Subdural - venous blood i.e. subdural haematoma

Question 21

Arachnoid mater

What are their general features?
What potential space do they create?
What can collect in these spaces?

Answer 21

Middle meningeal layer

• More delicate/fine, fibrous
• Lines the meningeal layer of the dura mater

Subarachnoid space - space between arachnoid mater & pia mater
- Real space as CSF flows through it

Question 22

Pia mater

What are their general features?
What potential space do they create?
What can collect in these spaces?

Answer 22

Innermost meningeal layer
Envelopes the brain, difficult to separate
Thin and fragile

No space associated with it as it is adherent to the brain tissue

Question 23

What are dural partitions & their function?

Answer 23

Separation of the periosteal & meningeal layers of dura mater at various points to form inward projections that separate certain structures & form dural venous sinuses

Question 24

What are 4 important dural partitions?

Answer 24

Falx cerebri
Falx cerebelli
Tentorium cerebelli
Diaphragma sellae

Question 25

Falx cerebri

What structures does it attach/arise between?
What structures does it separate?
What dural venous sinus is it associated with?

Answer 25

Falx attaches anteriorly to the frontal crest & crista gali (projection of ethmoid bone)
Attaches posteriorly to the internal occipital protrusion & blends with tentorium

Runs along the longitudinal fissure & attaches superiorly to the sagittal suture

Separates the two cerebral hemispheres

Associated with the superior & inferior sagittal sinuses

Question 26

Tentorium cerebelli

What structures does it attach/arise between?
What structures does it separate?
What dural venous sinus is it associated with?

Answer 26

Runs laterally along the petrous part of the temporal bone and finishes anteriorly at the clinoid process of the sphenoid bone
Superiorly blends with the inferior aspect of the falx cerebri

Separates the posterior aspect of cerebrum from the cerebellum

Associated with the straight sinus, transverse sinuses and petrosal sinuses

Question 27

What veins drain into the dural venous sinuses?

What is clinically significant about this drainage regarding infection?

Answer 27

Cerebral veins - drain the blood supply of the brain
Diploic veins - spongey bone of the cranium
Emissery veins - blood supply from the neurovascular plane of the scalp (dense connective tissue layer)

Communication between scalp & superior sagittal sinus via emissary veins allows transmission of infection from scalp laceration to the brain

Question 28

Falx cerebelli

What structures does it attach/arise between?
What structures does it separate?
What dural venous sinus is it associated with?

Answer 28

In the posterior cranial fossa, attaches to the internal occipital crest posteriorly, superiorly attached to the tentorium and has a free anterior edge

Separates the hemispheres of the cerebellum

Not associated with a sinus

Question 29

Diaphragma salle

What structures does it attach/arise between?
What structures does it separate?
What dural venous sinus is it associated with?

Answer 29

Covers the hypophysial fossa of the salle turcica of the body of the sphenoid

Allows the infundibulm of the pituitary gland to pass through

Associated with the cavernous sinuses