The Cerebrovascular System

THE CEREBROVASCULAR SYSTEM

CEREBROVASCULAR SYSTEM • Brain makes up only of about 2% of total body weight in adults • It receives 15% - 17% of the total cardiac output • It consumes about 20% of the oxygen used by the entire body (3.5 ml/100 gm/min) • Cerebral blood flow at rest is 50-55 ml/100 gm /min)

CEREBROVASCULAR SYSTEM • PaO2 < 45 mm Hg – difficulty with complex task learning & short term memory • PaO2 = 30 mm Hg – cognitive disturbance & incoordination • PaO2 < 20 mm Hg – comatous • Loss of consciousness if brain deprived of blood for 10=12 seconds; after 3-5 min. irreparable damage or death may result

CIRCLE OF WILLIS BRANCHES

PERFORATING

INTERNAL CAROTID ARTERY - Cerebral part – where it penetrates the dura coming out from the cavernous sinus; ophthalmic, posterior communicating, anterior choroidal arteries, MCA, ACA - Cavernous part – passes thru the cavernous sinus; gives rise to hypophysial & meningeal

A5 segment

Callosal cistern

A4 segment

A3 segment

A2 segment

A1 segment (not seen Lamina terminalis cistern

ANTERIOR CEREBRAL ARTERY (ACA) - 5 segments: precommunicating A1, infracallosal A2, precallosal A3, supracallosal A4, & postcallosal A5 - serves the LE area of the primary somatomotor & somatosensory cortices - 30% - 35% of all intracranial artery aneurysms are found in the

MCA: - M2-M4 divides into superior and inferior trunks that supplies the insular cortex, inner aspects of opercula, & lateral surface of the cerebral hemisphere - serves the face, UE, & trunk areas of the primary somatomotor & somatosensory cortices

BASILAR ARTERY - located in the basilar sulcus on the anterior surface of the pons in prepontine cistern - 1st major br. AICA ( br of AICA is labyrynthine artery) - pontine arteries: paramedian br., short circumferential br., long circumferential br - last major br. – superior cerebellar arteries which divides into medial & lateral br

POSTERIOR CEREBRAL ARTERY - Basilar artery bifurcates in the interpeduncular cistern giving rise to posterior cerebral arteries - divided into 4 segments P1 – P4; supply along the occipitotemporal distribution, to regions of the brain controlling visual input and higher level visual processing

External Cerebral Veins: - Superior cerebral veins - Middle cerebral veins SSS, TS - Medial cerebral veins - Inferior cerebral veins SPetS - Basal veins of Rosenthal CVGalen, TS

SSS CavS, ISS SSS,

Internal Cerebral Veins: - Thalamostriate vein ICV - Anterior septal vein ICV - Internal cerebral veins (ICV) CVGalen

Cerebellar Veins: - Superior (Galenic) group TS, PetS

StS,

- Aneurysm of the cavernous portion of ICA - Carotico-Cavernous Fistula

Main tributaries of Cavernous Sinus - intercavernous sinuses - drains into the superior & inferior petrosal sinuses and the basilar plexus

Deep veins Ant. Cerebral & Deep Middle veins Basal vein of Rosenthal Internal Cerebral Vein Vein of Galen Straight Sinus Confluence of sinus Transverse sinus Sigmoid sinus *Cerebral Venous Thrombosis Int. Jugular vein -severe dehydration -birth control pills -hypercoagulable condition

ARTERIES OF THE SPINAL CORD - Anterior Spinal artery - Posterior Spinal arteries - Spinal branches of segmental (sulcal) arteries: - posterior (dorsal) - anterior (ventral) radicular a. and spinal medullary arteries all contribute to the arterial vasocorona - At level T12, L1 or L2, one spinal medullary artery, usually the left, is especially large and is known as Artery of Adamkiewicz