CEREBRAL VASCULAR ANATOMY

DR. MICHAEL THOMAS

Chapter 8Cerebral vascular system

Causes of vascular compromiseInternal carotid systemVertibrobasilar systemArteries and infarctsCircle of WillisVeinsSpinal cord blood flowThe blood-brain barrier

Focus on these aspects:1. Classification of bleeds2. Principal branches and areas supplied by the internal carotid system3. The vertebral and basilar arteries and the associated areas4. Anastomoses between ICS and VBS5. The circle of Willis6. Superficial and deep venous drainage of the brain7. The blood-brain barrier

HEMODYNAMICS

BRAIN REQUIRES 20% OF TOTAL BODY O2

CEREBRAL BLOOD FLOW IS16% OF CARDIAC OUTPUT

CEREBRAL PERFUSION PRESSURE (CPP) –MUST BE GREATER THAN 50mmHg TO MAINTAIN CELLULAR INTEGRETY

IRREVESIBLE BRAIN DAMAGE OCCURS AFTER 4 MIN OF CIRCULATORY ARREST

CPP=MAP-ICP

NORMAL ICP <20 mmHgMAP-mean arterial pressure

ANTERIOR CIRCULATION

ICA –INTERNAL CAROTID ARTERY ACA –anterior cerebral artery Acom – anterior communicating

artery MCA – middle cerebral artery

POSTERIOR CIRCULATION

VERTEBROBASILAR SYSTEM PICA – posterior inferior cerebellar

artery AICA – anterior inferior cerebellar

artery SCA – superior cerebellar artery PCA – posterior cerebral artery

PRIMARY SOURCE OF BLOOD FOR BRAIN STEM AND CEREBELLUM

INTERNAL CAROTID ARTERY SEGMENTS

CERVICAL – common carotid bifurcation to skull base

PETROUS –encased by petrous portion of temperal bone

CAVERNOUS – contained within cavernous sinus (hypophyseal and meningeal branches)

CEREBRAL – cavernous carotid to terminus (opthalmic, posterior communicating, and anterior choroidal arteries)

4 Main Branches of the Internal Carotid Artery and Sub-branches

Posterior communicating artery. Usually small artery that connects to the vertebral system

Anterior choroidal artery. Small artery that supplies the optic track (anterior choroidal artery syndrome), and internal capsule

Middle cerebral artery. The major branch. Supplies most of superolateral surface of the hemispheresM1 + lenticulostriate (sylvian cistern) internal superior and inferiorM2 insular cortexM3 opercular (over the insula)M4 cortical

Anterior cerebral artery. Other major branch. Supplies the medial surface of the frontal and parietal cortex and corpus callosum A1 cistern of the lamina terminalisA2 infracallosal A3 precallosalA4 supracallosalA5 postcallosal

Frontal branches

Parietal branches

Temporal branches

Anterior communicating artery. Short stout channel between the two anterior cerebral arteries near their origin

Frontopolar arteries supply anteromedial frontal lobe.

Pericallosal artery sweeps posterior just superiorly to the corpus callosum

Callosomarginal artery usually in the cingulate sulcus

MCALarger in 70%

ACA

OphthalamicPost communicatingAnterior choroidal

Pierces dura

Hypophysial and meningial

Carotid canal

Coronal section middle cerebral artery

Supply basal ganglia and internal capsule

Dorsal surface branches

Medial surface of hemispheres and inferior surface of temporal lobe

border

MCA M4 surface segments

Regions served by ACA / MCA / PCA

VERTEBRAL ARTERY

4 SEGMENTS V-1 TO V-4 V-1 ORIGIN SUBCLAVIAN TO C-6

TRANSVERSE FORAMEN V-2 C-6 TRANSVERSE FORAMEN TO

C-2 V-3 C2 TO ATLANTO-OCCIPITAL

MEMBRANE V-4 TRAVERSES DURA TO UNITE

WITH OPPOSITE VERTEBRAL ARTERY

The vertebrobasilar artery system. Supply spinal cord, brainstem, cerebellum, and posteroinferior cerebral hemisphere. 1. Spinal arteries branch from the vertebral. Anterior and posterior spinal arteryBasilar2. Posterior inferior cerebellar artery branches from each vertebral artery. Supplies lateral medulla and PI cerebellum3. Basilar artery formed from union of two vertebral arteries

4. Basilar artery ends in bifurcation into paired posterior cerebral arteries

PICA LOCATION CISTERNA MAGNA MAJOR BLOOD SUPPLY TO THE

MEDULLA POSTERIOR SPINAL ARTERY USUALLY

BRANCHES FROM PICA POSITIONED NEXT TO CRANIAL

NERVES 9, 10, AND 11

AICA BLOOD SUPPLY TO VENTRAL-LATERAL

CEREBELLUM, PONS, CHOROID PLEXUS

POSITIONED NEXT TO CRANIAL NERVES 7&8

SUPERIOR CEREBELLAR ARTERYSUPPLIES MEDIAL, LATERAL, AND SUPERIOR CEREBELLAR CORTEX AND CEREBELLAR NUCLEI AND MIDBRAINPASSES JUST CAUDAL TO CN III THROUGH AMBIANT CISTERN

PCA

P-1 – FROM BASILAR BIFURCATION TO PCOM ( GIVES OFF SMALL BRAINSTEM FEEDERS)

P-2 – FROM PCOM TO INFERIOR TEMPERAL BRANCHES ( GIVES OFF SMALL THALAMO-GENICLATE BRANCHES)

P-3 – PORTION THAT GIVES RISE TO TEMPERAL BRANCHES

P-4 – BRANCHES MEDIAL FORMING CALCARINE AND PARIETAL-OCCIPITAL ARTERIES

DORSAL BRAINSTEM VIEW

VENTRAL BRAINSTEM VIEW

The circle of Willis. A series of arteries that provides anastomotic communication between the left and right arterial trees and between the internal carotid and vertebral systems1. Anterior communicating artery2. Anterior cerebral artery3. Internal carotid artery4. Posterior communicating artery5. Posterior cerebral artery

Segments of the anterior and posterior cerebral

arteries

Ganglion arteries (not shown) branch from the circle of Willis and supply diencephalon and base of telencephalon

DEEP GANGLIONIC PERFORATING ARTERIES

Spinal cord blood supply

3 MAIN ARTERIES-ANTERIOR SPINAL ARTERY- 2 POSTERIOR SPINAL ARTERIES- ADAMKIEWCZ- ORIGIN IS LEFT SPINOMEDULLARY ARTERY T-12 – L1 SUPPLIES LOWER THORACIC AND UPPER LUMBAR CORD

Venous Circulation

CEREBRAL VENOUS CHARACTERISTICS

MULTIPLE ANASTOMOTIC CHANNELS MULTIPLE VENOUS SINUSES

CAVERNOUS,PETROSAL, SUPERIOR, INFERIOR, STRAIGHT, TRANSVERSE, SIGMOID

NONVALVULAR SYSTEM 4 UNPAIRED VEINS

SUPERIOR SAGITAL SINUS, INFERIOR SAGITAL SINUS, VEIN OF GALEN, STRAIGHT SINUS

DIVISIONS

1. BASAL VIENS(LATERAL SINUS,ROSENTHAL, PETROSAL SINUS,CAVERNOUS SINUS)

2. CEREBRAL –(SUPERIOR SAGITAL SINUS,ANASTOMOTIC VEINS - TROLARD,LABBE, SUPERIOR MIDDLE CEREBRAL VEIN

3. INTERNAL VEINS – DRAIN INTO THE VEIN OF GALEN

Vein of GalenStraight sinus

VEIN OF GALEN MALFORMATION

Blood Brain Barrier

BLOOD BRAIN BARRIER - PHYSIOLOGIC BARRIER PREVENTS MOVEMENT OF HIGH MOLECULAR WEIGHT MOLECULES - ABSENT FENESTRATIONS - TIGHT JUNCTIONS

REGIONS WITH NO BBB

1. AREA POSTREMA2. PINEAL AND PREOPTIC RECESSES 3. TUBER CINEREUM4. HYPOPHYSIS5. CHOROID PLEXUS

BBB DISRUPTION

GLIOBLASTOMA MULTIFORME WITH VASOGENIC EDEMA

BBB BREAKS DOWN UNDER DISEASE STATES

CEREBRAL SPINAL FLUID PRODUCTION & ABSORPTION

SUPERIOR SAGITAL SINUS OCCLUSION FROM MENINGIOMA

Causes of vascular compromise:A. Aneurysm

small (berry or saccular)large >2cmfusiform (elongated)85% ICA system15% VB system

B. Embolismthrombus – bloodtransient ischemic attackseptic emboli

C. arteriovenus malformationteens and young adultshare some features of neoplasm

1. dynamic2. lead to hemorrhage

SUBARACHNOID HEMORRHAGE CLOSED HEAD INJURY MOST COMMON ETIOLOGY

ANEURYSM RUPTURE ALMOST ALLWAYS CAUSE SAH

TRAUMATIC SAH OCCURS COMMONLY AT CONVEXITIES

ANEURYSMAL SAH OCCURS COMMONLY IN BASILAR CISTRNS

RARELY ANEURYSMAL SAH WILL EXTEND INTO THE VENTRICLE

MAY CAUSE HYDROCEPHALUS

SUBARACHNOID HEMORRHAGE

POSTERIOR COMMUNICATING ARTERY ANEURYSM

CEREBRAL ANEURYSMS

85% ANTERIOR CIRCULATION OCCURS NEAR BRANCHING VESSELS CAN CAUSE COMPRESSIVE CRAINIAL

NEUROPAHTY(pcom aneurysm compressing cn III causing ptosis AND PUPIL DILATION

3 TYPES SACCULAR

FUSIFORMEMYCOTIC

Common patterns of aneurysms: branches and tortuous turns

ICA system

VB system

ANEURYSM TREATMENT

SURGICAL CLIP LIGATION

ENDOVASCULAR COILING

ANEURYSM BYPASS AND CLIP LIGATION

COMBINATION COILING AND CLIPPING

Basilar Artery Apex Aneurysm

Occipital AVM

The cavernous sinus

AneurysmFistula

ARTERIAL VENOUS MALFORMATION

DIRECT CONNECTION BETWEEN ARTERY AND VEIN

CAPILLARY BED IS ABSENT NO INTERVIENING BRAIN TISSUE MEDIUM TO HIGH FLOW USUALLY PRESENTS WITH HEMORRAGE

OR SEIZURE PREGNANCY MAY CAUSE AVM TO GROW

AVM TREATMENT

SURGICAL RESECTION

EMBOLIZATION

RADIATION

COMBINATION THERAPY

INDICATED IF ELEQUENT BRAIN IS NOT INVOLVED

ENDOVASCULAR TECHNIQUES MAY HELP FACILITATE SURGERY. USUALLY REQUIORES MULTIPLE PROCEDURES

STEREOTACTIC RADIATION MAY BE USED FOR SMALL AVMs.

ALL THREE TREATMENT OPTIONS MAY BE USED FOR COMPLEX AVMs

AVM

ARTERIOVENOUS MALFORMATION

SUBDURAL HEMORRHAGE