NB2-2 - Meninges and Arteries and DLAs

Question 1

Describe what forms the denticulate ligaments and their general structure. What is the purpose of these ligaments?

Answer 1

The denticulate ligaments are extensions of the pia mater within the spinal column that attach to the surrounding acrachnoid and dural meningeal layers. These ligaments serve to provide support to and restrict the movement of the spinal cord

Question 2

Describe the changes that occur to the meninges from the skull to the spinal column

Answer 2

Within the skull, there is a layer of pia mater that is closely adhered to the brain, a subarachnoid space, a layer of arachnoid mater, a layer of meningeal dura mater, and a layer of periosteal dura mater that is adhered to the skull.

The periosteal layer of dura mater does not exist within the spinal column

Question 3

List and describe the structure/route of the arteries that supply the spinal cord

Answer 3

The vertebral arteries give off a single anterior spinal artery that runs along the anterior aspect of the spinal column within the groove created by the anterior median fissures. It will give of branches that enter the spinal cord at the anterior median fissures The posterior inferior cerebellar arteries (branches of the vertebral arteries) each give off a posterior spinal artery that runs along either side of the poster median sulcus of the spinal cord. Segmental branches of the vertebral arteries or aorta (depending on spinal level) give off dorsal/ventral spinal medullary arteries that anastomose with the posterior/anterior spinal arteries. The segmental arteries also give of dorsal/ventral radicular arteries that follow the dorsal/ventral roots into the spinal cord. There is also an arterial vasocorona that circumscribe the spinal cord and connects the dorsal and ventral spinal arteries and it gives off branches that enter the spinal cord all along its route. Refer to image

Question 4

Which arteries directly supply the spinal column and which parts of it do they supply. What symptoms are typical of an insufficiency of these arteries?

Answer 4

The posterior spinal arteries via the vasocorona supply the dorsal third of the spinal cord. This means that issues with somatosensation could occur if these arteries were to become occluded

The anterior spinal arteries and the vasocorona supply the anterior two-thirds of the spinal cord. This means that issues with motor functions and some pain/temperature sensations could occur if these arteries were to become occluded

Question 5

Answer 5

Question 6

Describe the types of cranial arteries. Include their distinguishing characteristics and the tissues they supply.

Answer 6

Meningeal Arteries - found between the periosteal layer of dura mater and the skull. These arteries supply the meninges with blood.

Cerebral Arteries - found within the subacarchnoid space. These arteries supply the brain with blood.

Refer to image

Question 7

Describe the convoluted structure of the dura mater, arachnoid mater, and associated spaces in the brain.

Answer 7

The periosteal layer of dura mater remains closely adhered to the skull. However, the meningeal layer of dura will follow sulci down until almost the corpus callosum. The triangular shaped space, at the top of the sulcus, created by the separation of the dural layers is called a superior sagittal sinus and is filled with venous blood. Towards the bottom of the sulcus, where the meningeal dura curves back around, a circular space is formed called the inferior sagittal sinus which also fills with venous blood. This extension of dura into the brain is called the falx cerebri. The arachnoid mater, and therefore the subarachnoid space, will follow the meningeal dura on this route as well. Refer to image

Question 8

What is an arachnoid granulation? What does it do and why does it exist? What are they aka?

Answer 8

An arachnoid granulation is a villus of the archanoid layer (aka - arachnoid villus) that extends into a superior sagittal sinus. This structure is what allows CSF to enter the venous system.

Question 9

Answer 9

Question 10

What vessel(s) have ruptured in an epidural hemorrhage? What typically causes this rupture? How do these injuries appear on a radiograph?

Answer 10

In an epidural hemorrhage, meningeal arteries have ruptured which is usually caused by trauma. The injury appears as a biconcave (lentiform) collection of fluid on a radiograph.

Question 11

What vessels have ruptured in a subdural hemorrhage? What typically causes this rupture? How does this injury appear on a radiograph?

Answer 11

A subdural hemorrhage is typically caused by a rupture of the tiny veins in the subdural space (between the two dural layers) at the point where they enter the superior sagittal sinus. This is usually caused by trauma. Bleeds arising from tearing of the meningeal dura are also considered subdural. This injury appears as a crescent shaped collection of fluid on a radiograph.

Question 12

What vessels have ruptured in a subarachnoid hemorrhage? What typically causes these vessels to rupture? How does this injury appear on a radiograph?

Answer 12

A subarachnoid hemorrhage is typically a rupture of a peripheral cerebral artery which is usually caused by an aneurysm. On a radiograph, this injury appears as a collection of fluid within the sulci of the brain. Refer to image

Question 13

Which vessels are ruptured with an intracerebral hemorrhage? What usually causes this rupture. How do these injuries appear on a radiograph?

Answer 13

Intracerebral hemorrages are typcially caused by ruptures of the intraparenchymal branches of cerebral arteries, most notably the lenticulostriate arteries from the MCA (refer to image). These ruptures are usually caused by an aneurysm as a result of poor lifestyle choices or a tumor. These hemorrhages usually appear as a collection of fluid in the internal portions of the brain with possible spill over into the ventricular system and ventricle dilation (refer to image).

Question 14

Why would an intracerberal hemorrhage cause dilation of the ventricular system?

Answer 14

With an intracerebral hemorrhage, blood can spill into the ventricles. In the ventricles, this blood will clot which can occlude the intraventricular foramen/cerebral aqueduct/central canal. CSF production continues but has no place to go so the venricles dilate.

Question 15

Why do strokes often cause motor issues on one side of the body?

Answer 15

The most common place for a stroke to occur is within the lenticulostriate arteries which supply the caudate nucleus, putamen, and globus pallidus. These nuclei are important for the initiation and organization of movement and regulation of cortical motor activity via the thalamus. Normally, a stroke only occurs on one side of the body.

Question 16

List the types of brain bleeds from most to least dangerous and explain why.

Answer 16

1. Subarachnoid hemorrhage is most dangerous because it has quick onset (arterial instead of venous damage) and is the most difficult to repair before death
2. An epidural hemmorrhage is the next most dangerous because it has quick onset (arterial damage) and if a person goes to sleep before symptoms present they may never wake up.
3. An intracerebral hemorrhage is next most dangerous because it is frequently survivable but likely to leave lasting damage
4. A subdural hemorrhage is least dangerous because it has a very slow onset and is usually easy to fix

Question 17

Answer 17

Question 18

Which arteries are responsible for the majority of the blood supply to the midbrain and thalamus?

Answer 18

Posterior cerebral arteries

Question 19

Where do the superior cerebellar arteries exit the basilar artery?

Answer 19

Near the junction of the midbrain and pons and right next to CN3 (possible clinical correlate)

Question 20

What does the anterior communicating artery do and why is it clinically significant?

Answer 20

The anterior communicating artery connects the two ACAs and forms the most anterior portion of the circle of willis. It is clinically significant because it is a common place to see aneurysms

Question 21

How far back to the ACAs supply typically?

Answer 21

Back to the parietal lobe

Question 22

What structures does the circle of willis surround?

Answer 22

Optic chiasm, optic tract, mamillary bodies, and the remaining ventral hypothalamus

Question 23

What are the striate arteries? What do they arise from and what structures do they supply?

Answer 23

They are early branches of the ACAS and supply the basal ganglia and anterior limb of the internal capsule.

Question 24

Describe the general areas that the PCAs and their branches supply.

Answer 24

• Parts of the thalamus and thrird ventricle
• Medial temporal lobe
• Occipital lobe
• Posterior medial parietal lobe

Question 25

Which lateral regions of the brain (imagine on the picture) are supplied by the ACA, MCA, and PCA?

Answer 25

Question 26

Occlusion of which major cerebral artery would you expect to cause language deficits?

Answer 26

Left MCA

Question 27

Which medial regions of the brain (imagine on picture) are supplied by the ACA, MCA, and PCA?

Answer 27

Question 28

Answer 28

Middle

You know it is middle for sure because the posterior limb of the internal capsule is affected. However, it could also be anterior since it supplies a little of the anterior limb of the internal capsule which is also affected.