HNN Topic 2 - Vasculature of the Brain and Meninges

Question 1

What is the clinical significance of the sphenoid emissary vein

Answer 1

Root of spread of infection from the upper teeth to the cranial cavity

Question 2

Describe the structural differences between normal veins and the dural venous sinuses

Answer 2

The dural venous sinuses lack smooth muscle and valves

Question 3

Define dural reflections

Answer 3

Areas where infolding of the dura mater occurs, partitioning the cranial cavity

Question 4

Describe the connections of the dural venous sinuses

Answer 4

• The superior and inferior sagittal sinuses anastomose with the straight sinus at the confluence of the sinuses - The transverse sinus comes from the confluence and goes on to form the sigmoid sinuses - The sigmoid sinuses drain into the IJV as they leave the cranium via the jugular foramina

Question 5

Describe the components and drainage of the deep venous system

Answer 5

• Drains the thalamus, hypothalamus, internal capsule, septum pellucidum, choroid plexus, corpus striatum and white matter - Deep cerebral veins = subependymal, medullary - Drain into the trasverse, straight and sigmoid sinuses

Question 6

Describe the drainage and connections of the cavernous sinus

Answer 6

Cavernous sinus is anterior, receives blood from the ophthalmic vein and empties into the superior and inferior petrosal sinuses which drain into the sigmoid sinuses (-> IJV)

Question 7

List the branches given off by the vertebral arteries and describe their functions

Answer 7

1. Meningeal branch - supplies falx cerebri 2. Anterior and posterior spinal arteries - supplies spinal cord 3. Posterior inferior cerebellar a - supplies cerebellum and pons

Question 8

Describe the position of the sellar diaphragm

Answer 8

Forms a partial roof over the hypophysial fossa, covers the pituitary fland, aperture for passage of the infundibulum of the pituitary

Question 9

List the main arteries which supply the brain

Answer 9

1. Vertebral arteries 2. Internal carotid arteries

Question 10

What is the significance of the falx cerebri when considering the dural venous sinuses

Answer 10

The falx cerebri between the L and R cerebral hemispheres (in the longitudinal fissure) contains the superior and inferior sagittal and straight sinuses

Question 11

Describe the position of the tentorium cerebelli

Answer 11

Between the occipital lobe of the cerebrum and the cerebellum, divides the cranial cavity into supratentorial and infratentorial areas

Question 12

Describe the features of the arachnoid mater

Answer 12

• Middle layer - Layers of connective tissue, avascular, no innervation - Subarachnoid space underneath, contains CSF - Projections of arachnoid mater into dura (arachnoid granulations) allow CSF to re-enter the circulation via dural venous sinuses

Question 13

Describe the components and drainage of the superficial venous system

Answer 13

• Primarily drains the cerebral cortex - Cortical veins - superior, middle and inferior groups - Drain into the superior sagittal sinus

Question 14

Describe the arrangement of the arteries which supply the brain

Answer 14

Terminal branches of the vertebral and internal carotid arteries form an anastomotic circle called the Circle of Willis, which gives off branches to supply the majority of the brain

Question 15

Which anatomical landmark marks the confluence of the sinuses

Answer 15

Internal occipital protuberance

Question 16

Describe the path of the internal carotid arteries

Answer 16

1. Move superiorly through the neck in the carotid sheath 2. Enter brain via foramen lacerum (carotid canal), 3. Pass anteriorly through cavernous sinus 4. Give off branches 5. Continue as middle cerebral arteries

Question 17

Describe the function of the meninges

Answer 17

• Provide supportive framework for cerebral and cranial vasculature - Act with CSF to protect the CNS from mechanical damage

Question 18

Describe the features of the pia mater

Answer 18

• V thin, tightly adhered to surface of brain/spinal cord - Follows contours of brain gyri/sucli - Highly vascularised, BVs perforate through to supply the underlying neural tissue - Anchored to brain by processes of astrocytes (glial cells) - Unicellular membrane

Question 19

List the branches given off by the internal carotid arteries and describe their functions

Answer 19

1. Ophthalmic artery - supplies structures of the orbit 2. Posterior communicating artery - connects the circle of Willis posteriorly 3. Anterior choroidal artery - supplies structures in the brain responsible for motor control and vision 4. Anterior cerebral artery - supplies anterior parts of the cerebrum

Question 20

List the dural reflections

Answer 20

1. Falx cerebri 2. Tentorium cerebelli 3. Cerebellar falx 4. Sellar diaphragm

Question 21

Describe the venous drainage of the dura mater

Answer 21

Dural venous sinuses -> IJV

Question 22

Describe the arterial supply of the dura mater

Answer 22

1. Anterior meningeal artery - branch of ethmoidal a 2. Middle meningeal artery - branch of maxillary a 3. Posterior meningeal artery - branch of ascending pharyngeal a 4. Accessory meningeal artery - branch of maxillary a

Question 23

List the layers of the dura mater

Answer 23

1. Endosteal/periosteal layer 2. Meningeal layer

Question 24

Describe the path of the vertebral arteries

Answer 24

1. Ascend the posterior aspect of the neck through the transverse foramen of the cervical vertebrae 2. Enter the cranial cavity through the foramen magnum 3. Give off branches 4. Converge to form the basilar artery which gives of branches to supply the pons and cerebellum 5. Basilar artery terminates by bifurcating into posterior cerebral arteries

Question 25

Describe the location of the dural venous sinuses in relation to the layers of the meninges

Answer 25

Between the outer (endosteal/periosteal) and inner (meningeal) layers of the dura mater

Question 26

Describe the endosteal layer of the dura mater

Answer 26

Lines the inner surface of the cranial bones, only present around the brain (not in the vertebral column)

Question 27

Describe the location of the dura mater

Answer 27

Outer layer of the meninges, lies directly under the bones of the skull and the vertebral column

Question 28

Describe the position of the cerebellar falx

Answer 28

Partially divides the cerebellar hemispheres

Question 29

List the dural venous sinuses

Answer 29

Superior sagittal sinus, inferior sagittal sinus, straight sinus, transverse sinus, sigmoid sinus

Question 30

Describe the features of the dura mater

Answer 30

Thick, tough, inelastic

Question 31

Describe the origins of the vertebral arteries

Answer 31

L and R from subclavian artery

Question 32

List the layers of the meninges

Answer 32

1. Dura mater 2. Arachnoid mater 3. Pia mater

Question 33

Describe the position and attachment of the falx cerebri

Answer 33

Between L + R hemispheres of the cerebrum in the longitudinal fissure Attached anteriorly to the crista galli of the ethmoid bone and posteriorly to the tentorium cerebelli

Question 34

Describe the general venous drainage of the brain

Answer 34

Veins empty into dural venous sinuses which eventually empty into the internal jugular veins

Question 35

Describe the meningeal layer of the dura mater

Answer 35

Lines the endosteal layer, only layer present in the vertebral column

Question 36

Where do the internal carotid arteries originate?

Answer 36

At the bifurcation of the L and R common carotid arteries, at the level of C4