Cranial Fossae Flashcards
What does the anterior cranial fossa lie over?
Nasal and orbital cavities
Which part of the brain is in the anterior cranial fossa?
Anterior inferior portions of the frontal lobes
Which bones make up the anterior cranial fossa?
Frontal
Ethmoid
Sphenoid
What are the boundaries of the anterior cranial fossa?
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
What is the crista galli?
An upwards projection in the midline of the ethmoid bone
Attachment for falx cerebri (sheet of dura mater that divides the two hemispheres)
What are the two main large foramen in the cribriform plate and what do they transmit?
Anterior ethmoidal foramen - transmission the anterior ethmoidal artery, nerve and vein
Posterior ethmoidal foramen - transmits the posterior ethmoidal artery, nerve and vein
How can fracture of the cribriform plate lead to to rhinorrhoea?
Fragments of the bone can tear the meningeal coverings of the brain, causing the leakage of CSF into the nasal cavity
What are the cranial fossae?
Three depressions which divide the floor of the cranial cavity
What is the shape of the middle cranial fossa and what is contained within it?
Butterfly shaped
Middle has pituitary gland
The two lateral parts have the temporal lobes of the brain
What bones does the middle cranial fossa consist of?
Sphenoid bone and two temporal bones
What are the boundaries of the middle cranial fossa?
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
What supports the pituitary gland?
Sella turicica- saddle-shaped bony prominence of the sphenoid bone. Sits in the pituitary fossa in this
Where are the optic canals situated in the middle cranial fossa and what passes through them?
Anteriorly, on the sphenoid bone
Transmit optic nerves and ophthalmic arteries into the orbital cavities
What connects the optic canals?
The chiasmatic sulcus - a depressed groove
Name the four foramina immediately lateral to the central part of the middle cranial fossa
Superior orbital fissure
Foramen rotundum
Foramen ovale
Foramen spinosum
What passes through the superior orbital fissure
Oculomotor nerve Trochlear nerve Ophthalmic branch of the trigeminal Abducens nerve Ophthalmic veins Sympathetic fibres
What is transmitted through the foramen rotundum?
Opens into the pterygopalatine fossa
-maxillary branch of the trigeminal nerve
What passes through the foramen ovale? Where does it open into?
The infratemporal fossa
Mandibular branch of the trigeminal nerve
Accessory meningeal artery
What passes through the foramen spinosum? Where does it open into?
Infratemporal fossa
Middle meningeal artery
Middle meningeal vein
Meningeal branch of CN V3
What are the three major foramina of the temporal bone?
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
Complications of pituitary surgery?
CSF rhinorrhoea Meningitis Diabetes Diabetes insipidus Haemorrhage Visual disturbances
What are the bones of the posterior cranial fossa?
Occipital
Temporal x2
Boundaries of the posterior cranial fossa?
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
What is the foramen in the temporal bone and what passes though?
The internal acoustic meatus in the petrous part
- facial nerve
- vestibulcochlear nerve
- labyrinthine artery
What are the foramina in the occipital bone?
Foramen magnum
Jugular foramina on either side
Hypoglossal canal
Cerebellar fossae
What passes through the foramen magnum?
Medulla of the brain Meninges Vertebral arteries Spinal accessory nerve (ascending) Dural veins Anterior and posterior spinal arteries
What passes through the jugular foramina?
Glossopharyngeal nerve Vagus nerve Spinal accessory nerve Internal jugular vein Inferior petrosal sinus Sigmoid sinus Meningeal branches of the ascending pharyngeal and occipital arteries
What passes through the hypoglossal canal?
Hypoglossal nerve
What is cerebellar tonsillar herniation?
Downward displacement of the cerebellar tonsils through the foramen magnum - aka coning
What can cause cerebellar tonsillar herniation?
Raised intracranial pressure - varied aetiology
- hydrocephalus
- space occupying lesions
- malformed posterior cranial fossa
What does the cerebellar tonsillar herniation result in?
Compression of the pons and medulla which contain the cardiac and respiratory centres
Could lead to death from cardio respiratory arrest
