INTRACRANIAL CIRCULATION

Question 1

What landmark distinguishes the brain from the spinal chord as it ascends into the skull?

Answer 1

Foramen magnum located in the Posterior cranial fossa.

Question 2

As the dura ascends, it fuses with the endo steam of the skull. At the cranial level, the _______ dura is attached to the skull; whereas, the _________ dura is continuous with that of the spinal cord.

Answer 2

Periosteal dura;

Meningeal dura.

Question 3

Describe the clinical significance of the CSF being continuous in the brain and spinal cord.

Answer 3

Bleeding or increased intracranial pressure can be detected via a lumbar puncture or spinal tap, since the brain is continuous with the spinal cord in this way.

Question 4

The ______ ______ artery supplies the periosteal dura and skull. It’s branches forms grooves on the skull and a tear in this artery can lead to an ______ hematoma.

Answer 4

Middle Meningeal Artery;

Epidural Hematoma

Question 5

The _______ _______ is a double-layer of meningeal dura that separates the right and left cerebral hemispheres. Above that, the ________ ______ sinus contains venous blood that runs posteriorly along the midline of the cerebrum. The ______ _____ sinus is connected with the one above and is entirely surrounded by meningeal dura.

Answer 5

Flax Cerebri (dura septum);
Superior Sagittal Sinus;
Inferior Sagittal Sinus

Question 6

A tear the ______ _______, which is a network of vessels that drain blood into the sagittal sinuses across the subarachnoid space, can lead to a ______ hematoma.

Answer 6

Cortical “Bridging” veins;

Subdural hematoma

Question 7

Define Emissary Veins and their clinical significance.

Answer 7

These superficial veins are valveless and connect venous drainage from outside the skull to the dural sinus inside the skull. Squeezing or not treating infections well on the scalp can lead to meningitis since blood can be pushed into the superior sagittal sinus from these veins.

Question 8

What is the confluens of sinuses?

Answer 8

This is a place where the superior sagittal, inferior sagittal and occipital sinuses intersect to drain cerebral blood into the Transverse sinus.

Question 9

Describe the path of blood after it is drained from the confluens of sinuses and exits the skull.

Answer 9

Confluens of sinuses > Transverse sinus dips down then flows anteriorly towards > Sigmoid sinus > which merges with Inferior Petrosal sinus > becomes Cavernous sinus and exits the skull > via the Jugular foramen > Internal Jugular vein.

Question 10

The internal jugular vein is formed from what 2 veins and where does it exit?

Answer 10

The internal jugular vein is formed from the Sigmoid sinus and Inferior Petrosal Sinus. Once formed, it exits the jugular foramen in the posterior cranial fossa to run down the neck.

Question 11

Define the Cavernous Sinus’ function and what it turns into. What brain structure is located nearby?

Answer 11

The cavernous sinus drains blood from the orbit and anterior aspects of the brain then gives rise to the Superior Petrosal Sinus and the Inferior Petrosal Sinus. The Pituitary gland sits in the sella turcica, between the 2 cavernous sinuses.

Question 12

How does CSF get from the inner ventricles to the outside of the brain, within the skull?

Answer 12

The CSF moves through the lateral foramina at the 4th ventricle and the median foramen at the posterior end of the 4th ventricle to get to the sub-arachnoid space and go anywhere in the CNS from there.

Question 13

What are the 2 main vessels for arterial blood supply to the brain?

Answer 13

1. The vertebral arteries which come off subclavian artery and ascends the neck once it passes through the transverse foramina to pass through the foramen magnum.
2. The internal carotid artery which terminates in the middle cranial fossa and splits into the anterior and middle cerebral arteries.

Question 14

Describe Subclavian Steal Syndrome.

Answer 14

An occlusion of the left subclavian (before the vertebral arteries break off) has blood move upwards from the right vertebral artery through the left vertebral to steal blood away from the brain to supply the working left upper limb. Lightheaded ness and fatigue can occur when the affected upper limb is exerted.

Question 15

What is the Circle of Willis?

Answer 15

The connection of arteries between the carotid system and the vertebra-basilar system. This connection has variable effectiveness from person to person. The main artery that connects the 2 systems is the Posterior Communicating Artery.

Question 16

What does the Posterior Cerebral artery supply and where does it branch from?

Answer 16

Supplies the occipital lobe and midbrain;

It branches off of the Basilar artery of the vertebra-basilar system.

Question 17

What does the Anterior Spinal artery supply?

Answer 17

This is the main blood supply for the medulla. It heads into the 2 vertebral arteries.

Question 18

What is the Posterior-Inferior Cerebellar Artery and what is the clinical significance?

Answer 18

The PICA is an artery that branches off from the vertebral arteries before they merge to form the Basilar artery. It is a common area for a stoke in some patients.

Question 19

What is the Labyrinthine artery?

Answer 19

This is an artery that enters the inner ear and exits off of the Anterior-Inferior Cerebellar artery (AICA).

Question 20

Compare and contrast the types of cranial hematomas and where they occur.

Answer 20

Epidural hematoma results from the tear in the middle meningeal artery. A subdural hematoma is caused by a tear in the cortical cerebral veins. A subarachnoid hemorrhage is caused by a rupture of a cerebral aneurysm.

Question 21

Describe a cerebral aneurysm.

Answer 21

A cerebral aneurysm is a short, round sacule of a cerebral artery caused by a weakness in the arterial wall. It is common at bifurcations (such as anterior communicating artery and anterior cerebral artery).

Question 22

Name the 2 types of treatments for a cerebral aneurysm.

Answer 22

1. Clipping at the root of the aneurysm.
2. Coil embolism involves a platinum wire inserted into the aneurysm via a catheter that provides a surface for blood to clot thus sealing the bulb.

Question 23

What makes an infection within the pterygoid venous plexus dangerous?

Answer 23

Infections in the face can cause clots that lead to the backup of blood into the cavernous sinus. A severe infection can result in meningitis.

Question 24

How does a subdural hematoma differ from an epidural hematoma in a radiograph?

Answer 24

A subdural hematoma can cross suture lines and presents as a “concave-convex” bulge in the skull from a radiograph. An epidural hematoma presents as a big, “bi-convex” internal bulge that does not cross suture lines because the dura is tight against the skull sutures.

Question 25

What cranial nerve, passes through the cavernous sinus and DOES NOT touch the lateral wall of the sella turcica?

Answer 25

CN VI, Abducens nerve

Question 26

The communication between the 3rd and 4th ventricle in the brain’s circulation of CSF is the…

Answer 26

Cerebral Aqueduct (aka Sylvius)

Question 27

What is the significance of the 4th ventricle and the choroid plexus, respectively?

Answer 27

From the 4th ventricle (crossroads between the medulla, pons and cerebellum), CSF can travel by conduits to any structure in the cranium. Choroid plexus is specialized ependymal tissue that secretes cerebrospinal fluid and is located in the Lateral and 4th ventricles.

Question 28

What is communicating hydrocephalus and how does it differ from the non-communicating counterpart?

Answer 28

Communicating hydrocephalus = is a blockage of arachnoid granulations that leads to an enlarged subarachnoid space since CSF is not being resorted into circulation.
The non-communicating hydrocephalus is featured as enlarged ventricles since the conduits between the ventricles can be blocked.

Question 29

What vein would the path of an acne infection cross to get into the cavernous sinus from the anterior tip of the nose?

Answer 29

Ophthalmic vein connects the facial vein of the face to the cavernous sinus. “Popping pimples improperly can be deadly!”

Question 30

A persistent nosebleed from the posterior and inferior aspects of the nasal cavity would result from a rupture of what artery?

Answer 30

Sphenopalatine artery that is a terminal branch of the maxillary artery.

Question 31

What is an indication of reduced infraorbital BP?

Answer 31

An obstruction in the internal carotid artery may be indicated by blood flow that comes from outside the orbit and inward.

Question 32

What vessel serves as a point of anastomoses between the external carotid artery and internal carotid artery? What is the normal direction of bloodflow?

Answer 32

The ophthalmic artery connects the internal carotid artery with branches of the external carotid artery on the skull. Normally, blood should flow from inside the orbit and outward.