Cerebral Hemispheres & Blood Supply

What % of problems in cranial cavity are related to a vascular cause?

50%

What % of total body weight is the brain?

about 2%

Brain received about ... of total cardiac output

20%

Brain uses almost ... of total oxygen used by the body

20%

When does Loss of Consciousness (LOC) occur?

when brain is deprived of oxygen for about 10 seconds

When will brain damage start to occur?

about 3 min. without oxygen

When will brain death occur?

after 10 min. without oxygen

Blood supply to Anterior Cerebral Hemispheres

bilateral Internal Carotid Arteries (ICA)

Blood supply to Posterior Cerebral Hemispheres

bilateral Vertebral arteries

Anterior Circulation of Cerebral Blood Supply

Aorta/Brachiocephalic Artery > Common Carotid Artery > Internal Carotid Artery > Anterior Cerebral Artery (anastomose anteriorly at Anterior Communicating Artery) > Middle Cerebral Artery

What artery is the most common artery affected by strokes?

Middle Cerebral Artery (MCA)

Posterior Circulation of Cerebral Blood Supply

Aorta > Subclavian Artery > Vertebral Arteries (ascend thru Transverse Process Foramen in CS vertebrae; enter Foramen Magnum to join Basilar Artery) > Basilar Artery > Posterior Cerebral Artery (PCA)

Where do the Anterior & Posterior Circulation meet?

anastomotic ring - Circle of Willis

In what % of people is the Circle of Willis complete?

25%

What vessel links the Anterior & Posterior Circulations?

Posterior Communicating Arteries - connect ICA to PCA

Anterior Cerebral Artery

passes forward to travel in the Inter-hemispheric Fissure as it sweeps back & over the Corpus Callosum

What is the ACA called along the Corpus Callosum?

Pericallosal Artery

What is the ACA called along Cingulate Sulcus?

Callosomarginal Artery

What does the ACA supply?

cortex on Anterior-Medial surface

Where does the Middle Cerebral Artery (MCA) travel?

Lateral/Sylvian Fissure

Superior Division of MCA

Supplies cortex above sylvian fissure

Inferior Division of MCA

supples cortex below sylvian fissure

Lenticulostriate Artery (MCA)

- supplies large portions of the Basal Ganglia & Internal Capsule

- particularly prone to narrowing

- tends to stroke by 40-50; can lead to Hemiparesis

Up to what amount of brain tissue may dies if there is a blockage of MCA?

about 1/2

Posterior Cerebral Artery

branches over & supplies the Inferior & Medial Temporal Lobes, Medial Parietal Cortex & Occipital Lobes

What Brodmann Areas are supplied by ACA?

8, 9, 10

What Brodmann Areas are supplied by MCA?

- 4, 6 (Pre-Central Gyrus, Primary Motor Cortex)

- 3, 1, 2 (Post-Central Gyrus, Primary Somatosensory Cortex)

- 5, 39, 40

- 22 (Wernicke's Area, speech perception)

- 41, 42 (Herschl's Gyrus, hearing)

- 44, 45 (Broca's Area, speech production)

What Brodmann Areas are supplied by PCA?

- 7

- 17, 18, 19 (Primary Visual Association Cortex)

Anterior Choroidal Artery (ICA)

supplies portions of the Globus Pallidus, Putamen, Thalamus, Posterior Internal Capsule

Recurrent Artery of Heubner (ACA)

supplies the Head of Caudate, Anterior Putamen, Globus Pallidus, & Internal Capsule

Thalamoperforating Arteries

supplies Thalamus & sometimes the Posterior Limb of Internal Capsule

Where do the Superficial Veins lie?

Subarachnoid Space

Where does the Upper part of the Cerebral Hemispheres drain?

Superior Sagittal Sinus

Where does the Middle part of the Cerebral Hemispheres drain?

Cavernous Sinus

What is the Cavernous Sinus?

- a plexus of veins located on either side of the Sella Turcica

- surrounds portions of CN III, IV, V, VI

Where does the Cavernous Sinus drain?

- via the Superior Petrosal Sinus into the Transverse Sinus

- the Inferior Petrosal Sinus into the IJV (Internal Jugular Vein)

Where does the Lower part of the Cerebral Hemispheres drain?

into the Transverse Sinus, then into IJV

Where do the Deep Structures of the Cerebral Hemispheres drain?

into Internal Cerebral Veins & Basal Veins of Rosenthal to reach the Great Cerebral Vein of Galen

How is the Straight Sinus formed?

by the joining of the Great Cerebral Vein of Galen w/ the Inferior Sagittal Sinus

Where does the Straight Sinus empty?

into the Transverse Sinus & into the IJV