Cranial Fossae

Question 1

What does the anterior cranial fossa lie over?

Answer 1

Nasal and orbital cavities

Question 2

Which part of the brain is in the anterior cranial fossa?

Answer 2

Anterior inferior portions of the frontal lobes

Question 3

Which bones make up the anterior cranial fossa?

Answer 3

Frontal
Ethmoid
Sphenoid

Question 4

What are the boundaries of the anterior cranial fossa?

Answer 4

Anteriorly and laterally - inner surface of the frontal bone

Posteriorly and medially - limbus of the sphenoid bone

Posteriorly and laterally - lesser wings of the sphenoid

Floor - frontal, ethic and anterior aspects of the body and lesser wings of the sphenoid bones

Question 5

What is the crista galli?

Answer 5

An upwards projection in the midline of the ethmoid bone

Attachment for falx cerebri (sheet of dura mater that divides the two hemispheres)

Question 6

What are the two main large foramen in the cribriform plate and what do they transmit?

Answer 6

Anterior ethmoidal foramen - transmission the anterior ethmoidal artery, nerve and vein

Posterior ethmoidal foramen - transmits the posterior ethmoidal artery, nerve and vein

Question 7

How can fracture of the cribriform plate lead to to rhinorrhoea?

Answer 7

Fragments of the bone can tear the meningeal coverings of the brain, causing the leakage of CSF into the nasal cavity

Question 8

What are the cranial fossae?

Answer 8

Three depressions which divide the floor of the cranial cavity

Question 9

What is the shape of the middle cranial fossa and what is contained within it?

Answer 9

Butterfly shaped
Middle has pituitary gland
The two lateral parts have the temporal lobes of the brain

Question 10

What bones does the middle cranial fossa consist of?

Answer 10

Sphenoid bone and two temporal bones

Question 11

What are the boundaries of the middle cranial fossa?

Answer 11

Anteriorly and laterally - lesser wings of the sphenoid bone

Anteriorly and medially - limbus of the sphenoid bone

Posteriorly and laterally - superior border of the petrous part of the temporal bone

Posteriorly and medially - dorsum stellate of the sphenoid bone

Floor - body and greater wing of the sphenoid, squamous and petrous parts of the temporal bone

Question 12

What supports the pituitary gland?

Answer 12

Sella turicica- saddle-shaped bony prominence of the sphenoid bone. Sits in the pituitary fossa in this

Question 13

Where are the optic canals situated in the middle cranial fossa and what passes through them?

Answer 13

Anteriorly, on the sphenoid bone

Transmit optic nerves and ophthalmic arteries into the orbital cavities

Question 14

What connects the optic canals?

Answer 14

The chiasmatic sulcus - a depressed groove

Question 15

Name the four foramina immediately lateral to the central part of the middle cranial fossa

Answer 15

Superior orbital fissure
Foramen rotundum
Foramen ovale
Foramen spinosum

Question 16

What passes through the superior orbital fissure

Answer 16

Oculomotor nerve
Trochlear nerve
Ophthalmic branch of the trigeminal 
Abducens nerve 
Ophthalmic veins
Sympathetic fibres

Question 17

What is transmitted through the foramen rotundum?

Answer 17

Opens into the pterygopalatine fossa

-maxillary branch of the trigeminal nerve

Question 18

What passes through the foramen ovale? Where does it open into?

Answer 18

The infratemporal fossa
Mandibular branch of the trigeminal nerve
Accessory meningeal artery

Question 19

What passes through the foramen spinosum? Where does it open into?

Answer 19

Infratemporal fossa
Middle meningeal artery
Middle meningeal vein
Meningeal branch of CN V3

Question 20

What are the three major foramina of the temporal bone?

Answer 20

Hiatus of the greater petrosal nerve - greater p. nerve (branch of facial) and petrosal branch of middle meningeal artery

Hiatus of the lesser petrosal nerve - l.p. nerve (branch of glossopharyngeal)

Carotid canal - internal carotid artery coming in to supply the brain. Deep petrosal nerve

Question 21

Complications of pituitary surgery?

Answer 21

CSF rhinorrhoea
Meningitis
Diabetes
Diabetes insipidus
Haemorrhage
Visual disturbances

Question 22

What are the bones of the posterior cranial fossa?

Answer 22

Occipital

Temporal x2

Question 23

Boundaries of the posterior cranial fossa?

Answer 23

Anteriorly and medially - dorsum sellae of the sphenoid

Anteriorly and laterally - superior border of petrous part of the temporal bone

Posteriorly - internal surface of the squamous part of the occipital bone

Floor - mastoid part of the temporal bone and squamous, condylar and basilar parts of the occipital bone

Question 24

What is the foramen in the temporal bone and what passes though?

Answer 24

The internal acoustic meatus in the petrous part

• facial nerve
• vestibulcochlear nerve
• labyrinthine artery

Question 25

What are the foramina in the occipital bone?

Answer 25

Foramen magnum
Jugular foramina on either side
Hypoglossal canal
Cerebellar fossae

Question 26

What passes through the foramen magnum?

Answer 26

Medulla of the brain 
Meninges
Vertebral arteries
Spinal accessory nerve (ascending)
Dural veins
Anterior and posterior spinal arteries

Question 27

What passes through the jugular foramina?

Answer 27

Glossopharyngeal nerve 
Vagus nerve
Spinal accessory nerve
Internal jugular vein
Inferior petrosal sinus
Sigmoid sinus
Meningeal branches of the ascending pharyngeal and occipital arteries

Question 28

What passes through the hypoglossal canal?

Answer 28

Hypoglossal nerve

Question 29

What is cerebellar tonsillar herniation?

Answer 29

Downward displacement of the cerebellar tonsils through the foramen magnum - aka coning

Question 30

What can cause cerebellar tonsillar herniation?

Answer 30

Raised intracranial pressure - varied aetiology

• hydrocephalus
• space occupying lesions
• malformed posterior cranial fossa

Question 31

What does the cerebellar tonsillar herniation result in?

Answer 31

Compression of the pons and medulla which contain the cardiac and respiratory centres
Could lead to death from cardio respiratory arrest