CH 4 Cranial Vascular: Anatomy and Physiology

Question 1

Vascular structure of the brain includes:

Answer 1

Carotid arteries, vertebral arteries, the circle of willis and the venous sinuses.

80% of blood supply from the carotid artery.
20% from vertebral artery.

cerebral arterial blood supply is predominantly directed to the basal ganglia at the early stages of development and then to the white matter later.

Question 2

Internal carotid arteries (ICA) course along each side of the neck, bifurcate to form

Answer 2

the anterior (ACA) and middle cerebral arteries (MCA) at the medial end of the sylvian fissure.

Question 3

The anterior cerebral arteries supply:

Answer 3

the medial cortex, the medial portions of the frontal lobes and the superior medial parietal lobes.

ACA is seen curving around the corpus callosum.

Question 4

Pericallosal artery

Answer 4

is the terminal end of the ACA and arches around the genue of the corpus callosum and runs along the longitudinal fissure anterior to posterior.

Question 5

Heubner’s artery

Answer 5

important branch of the ACA supplies the anteriomedial part of the head of the caudate nucleus.

*main nutrient vessel of the caudate

Question 6

ACA and pericallosal arteries best seen

Answer 6

in mid-sagittal plane through the anterior fontanelle.

*power doppler is best for evaluating the ACA because it provides a more accurate image.

Question 7

Direction of flow in anterior cerebral artery (ACA) when performing TCD

Answer 7

is away from transducer

Question 8

TCD is done in children when

Answer 8

child with sickle cell

Question 9

Middle cerebral arteries

Answer 9

largest and most terminal branches of the ICA and the longest branch which helps form the circle of willis. the MCA supply the majority of the cerebrum.

Question 10

MCA runs

Answer 10

laterally in the sylvian fissure as a continuation of the intracranial ICA and carries 80% of blood flow to the cerebral hemispheres. supplies a major part of the basal ganglia and its branches and lateral surface of the cerebral hemispheres.

Question 11

MCA visualized

Answer 11

*the one intracranial vessel that can be evaluated most accurately

is seen at the level of the cerebral peduncles running anteriolaterally toward the lateral edge of the orbits.

Question 12

MCA branches

Answer 12

tree-like small branches that bring blood to entire lateral aspect of each cerebral hemisphere, including the areas of speech (brocas area)

*small branches M3 branches “stroke arteries” because damage to them can cause major disabilities including paralysis.

Question 13

Transtemporal position for TCD

Answer 13

best approach to image MCA

window is parallel to MCA and the blood flow is seen flowing towards the transducer.

Question 14

Medial and lateral branches of the MCA supply

Answer 14

the basal ganglia and thalamus and are very thin, thus more prone to hemorrhage.

Question 15

Posterior cerebral arteries supply

Answer 15

the occipital lobe of the brain and inferior aspects of the temporal lobes, the midbrain and thalami

Question 16

Anterior communicating artery (AcomA) and Posterior communicating artery (PcomA) arise from

Answer 16

ICA

Question 17

Anterior communicating artery (AcomA)

Answer 17

joins the anterior cerebral arteries (aca) which are branches of the ICA of each hemisphere

Question 18

Posterior communicating artery (PcomA)

Answer 18

joins the MCA’s to the posterior cerebral arteries, which are part of the basilar artery system. Runs from the posterior cerebral arteries(PCA) to ICA

Question 19

ECA

Answer 19

supply face, high resistance

Question 20

ICA

Answer 20

supply the brain along with the verts, which help to form the circle of willis. low resistance.

Question 21

Circle of willis

Answer 21

brains own collateral pathway and decrease blood pressure in brain. Important role in the pressure equilibrium of the cerebral vasculature.

Question 22

Circle of willis formed by

Answer 22

blood carried by 2 ICA’s and basilar system come together and redistributed by the ACA, MCA, and PCA, with 2 AcomA and 2 PcomA.

formed by the anterior comm. artery, 2 anterior cerebral arteries, 2 ICA’s, 2 posterior comm arteries and 2 posterior cerebral arteries.

Question 23

Basilar and MCA supply the brain…

Answer 23

they are not considered part of the circle of willis

Question 24

Vertebral arteries

Answer 24

enter through the foramen magnum into the brain. just inferior to pons they join to become the basilar artery

Question 25

Basilar artery

Answer 25

give off to R and L posterior cerebral arteries at superior level of the pons. It can be seen pulsating in the notch of the cerebral peduncles.

Question 26

Chorodial arteries

Answer 26

arise from the basilar and ICA *supply the choroid plexes. damage to these arteries can affect the CSF production

Question 27

cerebral bloodflow autoregulation

Answer 27

brainstem better at autoregulation pressures ranging from 50mmHg - 160 mmHg * the cerebral cortex suffers at low pressures. * the cerebral vasculature dilates when oxygen content is reduced, but this is limited.

Question 28

Venous drainage of brain

Answer 28

superficial and deep drainage through veins and venous sinuses. veins in brain have thin walls and no valves.

Question 29

cerebral veins

Answer 29

superficial and deep. superficial lie on surface and drain into SSS and deep veins drain internal structures of the brain into the straight sinus.

Question 30

Superior cerebral veins

Answer 30

drain the superior, lateral and medial surfaces of the brain and open into the SSS

Question 31

Middle cerebral vein

Answer 31

runs along the lateral cerebral fissure and is *connected with the SSS and transverse sinus

Question 32

Internal cerebral vein formed:

Answer 32

from choroid vein and terminal or thalmostriate vein.

Question 33

Terminal vein runs..

Answer 33

between thalmus and caudate nucleus.

Question 34

Choroid vein runs...

Answer 34

along the choroid plexus and receives blood from the corpus callosum.

Question 35

Internal cerebral veins

Answer 35

are paired and fuse posterior to pineal gland to form the great cerebral vein (vein of galen) and then course posterior to empty into the straight sinus.

Question 36

Great cerebral vein (vein of Galen) runs

Answer 36

superiorly and joins the inferior sagittal sinus to form the straight sinus.

Question 37

Venous thrombosis of the internal cerebral vein

Answer 37

thought to be due to trauma, may be a cause of thalamic edema.

Question 38

Dural venous sinuses

Answer 38

are superficial and large, composed of dura mater, and responsible for deep drainage of the brain. blood is drained into the internal jugular vein via dural sinuses.

Question 39

The most prominent sinus?

Answer 39

Superior sagittal sinus

Question 40

Main sinuses of brain:

Answer 40

``` Superior sagittal sinus (SSS) Inferior sagittal sinus straight sinus (vein of galen) transverse sinus (R&L) occipital sinus ```

Question 41

Superior sagittal sinus (SSS)

Answer 41

seen within the falx and exhibits low amplitude cardiac pulsations. High amplitude saw-tooth pattern is abnormal and indicative of cardiac abnormalities arachnoid granulations dump into SSS too much pressure with scanning may compress SSS

Question 42

Superior sagittal sinus (SSS) thrombosis should be considered in neonates with:

Answer 42

severe dehydration, sepsis, ECMO

Question 43

Paired Transverse sinuses

Answer 43

large in size. the R trv sinus is a continuation of the SSS and L is a continuation of the straight sinus.

Question 44

Inferior sagittal sinus

Answer 44

difficult to see, superimposed in the pericallosal artery Joins the vein of galen to form the straight sinus.

Question 45

Straight sinus

Answer 45

junction of the falx cerebri and the tentorium cerebelli. Internal cerebral veins are paired and fuse to form the great cerebral vein (vein of galen) then joins the inferior sagittal sinus to form the straight sinus.

Question 46

watershed areas

Answer 46

area of brain at the end of vascular distribution, distant from the circle of willis, where cerebral arteries meet and form anastamoses. -tertiary brain area located peripheral to primary distribution area for the anterior, posterior, and middle cerebral arteries; it derives blood via the branches of all 3 cortical arteries (ant,post, mid) because of the extreme ends, they are particularly vulnerable to ischemia and infarction in those who have circulation problems.

Question 47

2 major areas of the brain that can be affected by an asphyxia event ant the resultant hypoxia/ischemia are:

Answer 47

cortical "watershed" areas, and the deep structures; the basal ganglia "germinal matrix"

Question 48

Resistive Index (RI)

Answer 48

systolic velocity - diastolic velocity / systolic velocity

Question 49

Pulsatility index (PI)

Answer 49

systolic velocity - diastolic velocity / mean velocity

Question 50

time average mean velocity (TAMV)

Answer 50

average of the mean blood flow over a period of time *mean blood flow velocity is the most informative predictor of cerebral blood flow.

Question 51

Infants with hydrocephalus, doppler studdies of the ACA and MCA

Answer 51

with and without pressure on the fontanelle and a change in RI is a good predictor for the need for shunt placement. compression of anterior fontanelle when examining the ACA results in little or no change in normal child. With hydrocephalus, compression of the fontanelle increases the intracranial pressure resulting in an increase in arterial pulsatility.

Question 52

Increased vasoliatation

Answer 52

decreases cerebrovascular resistance

Question 53

increased vasoconstriction

Answer 53

increases cerebrovascular resistance which decreases cerebral blood flow

Question 54

increase in intracranial pressure results in

Answer 54

decrease in diastolic flow in the intracranial vessels. resitive indices correlate well with rising intracranial pressure.

Question 55

stable ventriculomegaly should have _______ pulsatility (PI) and resistive indices (RI)

Answer 55

NORMAL pulsatility and resistive indices; an elevated RI may imply the need for shunt. ventriculomegaly - normal intracranial pressure hydocephalus- increased intracranial pressure

Question 56

ECMO

Answer 56

exhibit an absence of intracranial arterial pulsation altogether due to being placed on non-pulsatile cardiopulmonary bypass after ligation of the R common carotid artery and jugular vein. venous drainage is also affected which puts the infant at higher risk of infarctions while being treated.

Question 57

severe hypocarbia

Answer 57

lower than normal carbon dioxide levels in the blood, induced by hyperventilation can result in ischemia and PVL in preterm infants

Question 58

changes in arterial carbon dioxide (CO2)

Answer 58

tension result in changes in cerebral blood flow. with extreme elevations of CO2, a decrease in the cardiovascular resistance occurs along with transmural pressure in the capillaries of the brain and can lead to SEH.

Question 59

Asphyxia results in

Answer 59

injury of cerebral autoregulation producing an increase in diastolic blood flow and a decrease in cerebrovascular resistance.

Question 60

Cerebral edema

Answer 60

swelling after hypoxic- ischemic events, vessels compressed, and increased cerebrovascular resistance, with dampening of the diastolic blood flow.

Question 61

TCD findings consistent with vasospasm following a sucharachnoid hemorrhage include

Answer 61

* greatly increased mean velocities in the cerebral arteries. another finding in child with brain atrophy would be a low RI * asymmetric pulsations in the brain are the first indication of ischemia and potential unilateral cerebral infarction.

Question 62

Increased RI seen in

Answer 62

intracranial bleeds, PVL, brain edema, subdural hematoma, hydrocephalus

Question 63

Decreased RI seen in

Answer 63

asphyxia (decreased acutely), ECMO, AVM, brain atrophy, term infants

Question 64

TCD in infants/children for:

Answer 64

AVM, hydrocephalus, subdural fluid, asphyxia, cerebral edema, brain death, and to asses for stroke prediction in sickle cell anemia.

Question 65

4 natural cranial windows

Answer 65

transtemporal transorbital transforaminal submandibular

Question 66

transtemporal window

Answer 66

MCA, ACA, PCA, anterior and posterior communication arteries, and terminal portion of the ICA. communicating arteries are only seen by TCD whern they are collateral routes. MCA - towards transducer MCA/ACA bifucation- bi directional; MCA towards, ACA away from transducer PCA- circles around and shows flow towards

Question 67

transorbital window

Answer 67

evaluate the ophthalmic artery and the 3 segments of the carotid siphon; parasellar genu and supraclinoid

Question 68

transforaminal window

Answer 68

evaluate the intracranial portions of the basilar and verterbral arteries. direction from this window is away

Question 69

submandibular window

Answer 69

evaluate extradural portion of the ICA. direction from this window is away.

Question 70

relative flow velocities in the intracranial arteries :

Answer 70

MCA > ACA > PCA = BA = VA

Question 71

most common AV malformation

Answer 71

vein of Galen aneurysm

Question 72

Vein of Galen malformation

Answer 72

vascular irregularity characterized by a fistula between the cerebral arteries and the vein of Galen.

Question 73

2 types of vein of galen aneurysm

Answer 73

* chorodial AVM - consist of multiple abnormal vessels in the midbrain with drainage into a dilated vein of Galen and the straight sinus. * Infundibular AVM - one or more arterial feeders draining directly into the vein of Galen.

Question 74

Vein of Galen malformation sono

Answer 74

cystic structure with arterial and venous flow within it is seen posterior to the foramen of Monro and superior to the 3rd vent.

Question 75

Sub-axial fluid

Answer 75

CFD to determine between subarachnoid vs subdural. * subarachnoid space- lifts cortical vessels, vessels float * subdural space- fluid pushes vessels towards brain surface, vessels compressed

Question 76

Sickle cell anemia

Answer 76

hereditary, abnormal hemogloin in RBC. sickles or half-moon shaped, "stuck" in vessels, die sooner than healthy RBC causing anemia. high velocities due to luminal narrowing. cerebral infarction due to vessel occlusion. major complication- brain disease, "silent" strokes

Question 77

TCD for Sickle cell anemia

Answer 77

screening tool to evaluate risk of stroke. | doppler MCA, ICA, ACA for an increase in mean flow velocity in children between 2-16 years.

Question 78

TCD sickle cell anemia Mean flow velocities

Answer 78

* greater than 200 cm per second in the MCA, distal ICA, or ACA/MCA bifur ar indicative for high risk of stroke. * drs treat pediatric patients with and increased flow velocity in the MCA with transfusions.

Question 79

Factors influencing cerebral blood flow (CBF)

Answer 79

Age: CBF decreases with age Hematocrit: decreased hematocrit= increased CBF CO2: increased CO2 = increased CBF Oxygen: hypoxia results in incresed CBF Hypoglycemia: increases CBF = to get more glucose to the brain Fever: CBF increases 10% for every increase in degree of the normal temperature

Question 80

normal brain RI

Answer 80

.6-.8

Question 81

HIE (hypoxic ischemis encephalopathy) RI

Answer 81

decreases RI = poor neuro outcome

Question 82

brain edema due to HIE: RI

Answer 82

low TI initially increased edema = increased RI diastole may be reversed