TBL28 - Meninges

Question 1

What is the brain covered by and what are these structures continuous with and where? What does CSF fill and what does it function in?

Answer 1

1) The brain is covered by cranial meninges that are continuous with the meninges of the spinal cord at the foramen magnum
2) CSF fills the subarachnoid space where it cushions and nourishes the brain and spinal cord

Question 2

What does the periosteal layer of cranial dura adhere to? How do dural infoldings form?

Answer 2

1) The periosteal layer of cranial dura adheres to the inner surface of the cranium
2) At certain locations, the meningeal layer of cranial dura separates from the periosteal layer to form dural infoldings

Question 3

Which layer of the cranial dura continues through the foramen magnum to join the spinal dura?

Answer 3

Only the meningeal layer of cranial dura continues through the foramen magnum to join the spinal dura

Question 4

What is the smallest meningeal dural infolding called and what does it cover? What is the largest dural infolding? What does this large dural infolding separate?

Answer 4

1) The horizontal sellar diaphragm, the smallest meningeal dural infolding, covers the hypophyseal fossa
2) The vertical cerebral falx is the largest dural infolding
3) It separates the two cerebral hemispheres

Question 5

What forms a cover over the posterior cranial fossa? What does the cerebellar tentorium separate?

Answer 5

1) The horizontal cerebellar tentorium (dura mater) bony attachment forms a cover over the posterior cranial fossa
2) The cerebellar tentorium separates the occipital lobes of the cerebral hemispheres from the cerebellum

Question 6

What does the midbrain traverse to pass from the posterior cranial fossa into the middle cranial fossa?

Answer 6

The midbrain traverses the tentorial notch to pass from the posterior cranial fossa into the middle cranial fossa

Question 7

What do the superior cerebral veins on the surface of the brain empty into? What does this dural venous sinus form between?

Answer 7

1) Superior cerebral veins on the surface of the brain empty into the superior sagittal sinus
2) The superior sagittal sinus is one of the dural venous sinuses that form between the periosteal and meningeal layers of the dura

Question 8

What are the dural venous sinuses lined by? Where does blood from these sinuses ultimately drain into?

Answer 8

1) The dural venous sinuses are lined by endothelium

2) Blood in the sinuses ultimately drains into the IJV

Question 9

Why does endothelium line the dural venous sinuses?

Answer 9

Blood vessels require the anticoagulative properties of endothelium

Question 10

Where are superior and inferior sagittal sinuses found? What forms the straight sinus? Where does the straight sinus run and what does it join? What also drains into these sinuses?

Answer 10

1) The superior and inferior sagittal sinuses are found in the cerebral falx
2) The inferior sagittal sinus unites with the great cerebral vein to form the straight sinus
3) The straight sinus, which runs along the midline attachment of the cerebral falx to the cerebellar tentorium, joins the confluence of sinuses
4) The superior sagittal sinus also drains into the confluence of sinuses

Question 11

What does the confluence of sinuses empty into? Where do these sinuses course along and what do they join?

Answer 11

1) The confluence of sinuses empties into the right and left transverse sinuses
2) These sinuses course along the posterolateral attached margins of the cerebellar tentorium and join the sigmoid sinuses at the posterior aspect of the petrous temporal bones

Question 12

Where do the sigmoid sinuses course within and what do they join at the jugular foramina?

Answer 12

The sigmoid sinuses course within deep grooves in the temporal and occipital bones and join the IJVs at the jugular foramina

Question 13

What forms the cavernous sinuses and where do they reside? What are the primary tributaries of the cavernous sinuses? What drains the cavernous sinuses directly into the sigmoid sinuses?

Answer 13

1) Plexuses of endothelium-lined channels form the cavernous sinuses that reside along the lateral sides of the body of the sphenoid bone
2) The superior ophthalmic veins are the primary tributaries (ignore sphenoparietal sinuses) of the cavernous sinuses
3) The inferior petrosal sinuses drain the cavernous sinuses directly into the sigmoid sinuses

Question 14

How can facial infections spread to the cavernous sinus or pterygoid venous plexus?

Answer 14

1) The facial vein makes clinically important connections with the cavernous sinus through the superior ophthalmic vein, and the pterygoid venous plexus through the inferior ophthalmic and deep facial veins
2) Because of these connections, an infection of the face may spread to the cavernous sinus and pterygoid venous plexus

Question 15

How does thrombophlebitis of the cavernous sinus typically occur?

Answer 15

1) Cavernous sinus thrombosis usually results from infections in the orbit, nasal sinuses, and superior part of the face
2) In persons with thrombophlebitis of the facial vein, pieces of an infected thrombus may extend into the cavernous sinus, producing thrombo phlebitis of the cavernous sinus
3) The infection usually involves only one sinus initially, but it may spread to the opposite side through the intercavernous sinuses

Question 16

What does the inferior petrosal sinus also drain into, where does this plexus traverse and what does it join in the vertebrae? What thereby creates the venous pathway for metastasis from distant tumors to the brain?

Answer 16

1) The inferior petrosal sinuses also drain into the basilar plexus, which traverses the foramen magnum to join the internal vertebral venous plexus of the spinal cord
2) The vertebral venous plexus of the spinal cord thereby creates the venous pathway for metastasis from distant tumors (e.g., prostate cancer) to the brain

Question 17

In the infratemporal fossa, what does the middle meningeal artery branch from and what does it enter the middle cranial fossa via? What creates the foramen spinosum and grooves? Where do veins accompanying these branches empty into?

Answer 17

1) In the infratemporal fossa, the middle meningeal artery branches from the maxillary artery and enters the middle cranial fossa via the foramen spinosum
2) The foramen spinosum and grooves are created by the middle meningeal artery and its anterior and posterior branches
3) Veins accompanying the branches traverse the foramen spinosum and empty into the pterygoid venous plexus

Question 18

Why can a fracture of the pterion be life threatening?

Answer 18

Fracture of the pterion can be life threatening because it overlies the frontal branches of the middle meningeal vessels, which lie in grooves on the internal aspect of the lateral wall of the calvaria

Question 19

What nerves provide sensory innervation to the dura? Where do sensory fibers convey pain from the dura to and what are examples of these areas?

Answer 19

1) CNs V1, V2 and V3 and peripheral fibers from DRG at C2 and C3 provide somatic sensory innervation of the dura
2) The sensory fibers convey pain from the dura to mucosal or cutaneous regions innervated by the nerves i.e., dural pain is not perceived locally but referred to the scalp, the nasal or oral mucosae, or the skin of the face or neck

Question 20

What does CSF in the subarachnoid space hold the fibrous arachnoid against? What is the pia made up of and what does it adhere to?

Answer 20

1) CSF in the subarachnoid space holds the fibrous arachnoid against the dura
2) The pia, several layers of fibroblasts linked by tight junctions and separated by loose connective tissue, adheres to the surface of the brain and follows all its contours

Question 21

How do the sources and locations of extravasated blood differ with an epidural hematoma, dual border hematoma, and subarachnoid hemorrhage? (check if this is right)

Answer 21

1) Extradural (epidural) hemorrhage is arterial in origin. Blood from torn branches of a middle meningeal artery collects between the external periosteal layer of the dura and the calvaria
2) A dural border hematoma is commonly called a subdural hematoma; however, this term is a misnomer because there is no naturally occurring space at the dura– arachnoid junction. Hematomas at this junction are usually caused by extravasated blood that splits open the dural border cell layer
3) Subarachnoid hemorrhage is an extravasation of blood, usually arterial, into the subarachnoid space. Most subarachnoid hemorrhages result from rupture of a saccular aneurysm (sac-like dilation on the side of an artery), such as an aneurysm of the internal carotid artery