cerebral vascular lecture
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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
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