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BLOOD SUPPLY OF BRAIN BY: DR. IBRAR AHMED HASHMI ARTERIAL SUPPLY OF BRAIN COMMON CAROTID ARTERY • 70% blood is delivered to ICA • Carotid bifurcation is a physiological stenosis due to inertial forces of blood flow divert main flow stream from midvessel to a path along vessel margin at flow divider • CCA divides lateral to upper border of thyriod cartilage: C3-4 intervertebral disc. • ECA arises anterior and medial to ICA(95%) CAROTID VESSELS ARTERIAL SUPPLY OF BRAIN EXTERNAL CAROTID ARTERY 1. 2. 3. 4. 5. 6. 7. 8. ASCENDING PHARYNGEAL ARTERY SUPERIOR THYROID ARTERY LINGUAL ARTERY EXTERNAL MAXILLARY=FACIAL ARTERY OCCIPITAL ARTERY POSTERIOR AURICULAR ARTERY SUPERFICIAL TEMPORAL ARTERY INTERNAL MAXILLARY ARTERY INTERNAL CAROTID ARTERY 1. 2. 3. 4. CERVICAL SEGMENT PETROUS SEGMENT CAVERNOUS SEGMENT SUPRACLINOID SEGMENT INTERNAL CAROTID ARTERY • CERVICAL SEGMENT: – Ascends posterior and medial to ECA: enters carotid canal of petrous bone; – – NO BRANCHES CAROTID BULB= CAROTID SINUS • • • Dilated proximal part of ICA with thinner media and thicker adventitia containing many receptor endings of glossopharyngeal nerve. Baroreceptor responsive to change in arterial BP. Hypersensitive carotid sinus: slight touch or neck movement initiates drop in BP and SA/AV blocks. • PETROUS SEGMENT: – – Ascends briefly in carotid canal ; bends anteromedially in horizontal course(ant to tympanic cavity and cochlea); exits near post portion foramen lacerum;ascends to juxtasellar location and pierces dural layer of cavernous sinus. BRANCHES: (rarely seen on angiograms) 1. CORTICOTYMPANIC A. 2. PTERYGOID (VIDIAN) A.(inconstant) • CAVERNOUS SEGMENT: – – Ascends to posterior clinoid process, then turns anteriorly and superomedially through cavernous sinus: exits medial to ant clinoid process piercing dura. BRANCHES: 1. Meningohypophysial trunk 2. Anterior meningeal artery 3. Cavernous rami for trigeminal ganglia, cavernous sinus and inf. petrosal sinuses. • SUPRACLINOID SEGMENT: – – Ascends posterior + lateral b/w oculomotor and optic nerv. BRANCHES: 1. OPHTHALMIC A. 2. SUPERIOR HYPOPHYSEAL A. (not routinely visualized) 3. PCOM 4. ANTERIOR CHOROIDAL A. 5. MCA 6. ACA • CAROTID SIPHON: (3rd + 4th part of ICA) – FLOW DIRECTION: C4---C1 a) C4 SEGMENT= Before origin of ophthalmic a. b) C3 SEGMENT= Genu of ICA. c) C2 SEGMENT= Supraclinoid segment after origin of ophthalmic a. d) C1 SEGMENT= Terminal segment of ICA b/w pCom + ACA. CAROTID SIPHON ANTERIOR CEREBRAL ARTERY 1. A1 SEGMENT= HORIZONTAL PORTION b/w origin and aCom. • • Inferior branches to optic nerve and chiasma Superior branches to ant hypothalamus, septum pellucidum, ant commisure, fornix, columns, medial lenticulostriate artery to anteroinferior portion of corpus striatum. 2. A2 SEGMENT= INTERHEMISPHERIC PORTION after the origin of aCom. • BRANCHES: 1. 2. 3. 4. • Medial orbitofrontal artery. Frontopolar artery. Callosomarginal artery. Pericallosal artery. SUPPLY: anterior 2/3 of medial cerebral surface and 1cm of superomedial brain over convexity. MIDDLE CEREBRAL ARTERY • Largest branch of ICA, arises lat to optic chiasma, passes horizontal and lateral direction to enter in sylvian fissure and divides into 2/3/4 branches • SUPPLY: – Lateral cerebrum – Insula – Anterior and Lateral temporal lobes • M1 SEGMENT: – Origin to MCA bifurcation – Lateral lenticulostriate • M2 SEGMENT: – Insular branches • M3 SEGMENT: – MCA branches beyond sylvian fissure BLOOD SUPPLY OF BRAIN INTERNAL CAROTID ARTERY INTERNAL CAROTID ARTERY INTERNAL CAROTID ARTERY VERTEBRAL ARTERY • 1st branch of subclavian(95%) • Left vertebral arises directly from aortic arch in 5%. • Left artery is dominant in 50%, in 25% co dominant, in 25% right is dominant. VERTEBRAL ARTERY A. PREVERTEBRAL SEGMENT: Enters transverse foramina at C6, only muscular branches. B. CERVICAL SEGMENT: Anterior meningeal artery. C. ATLANTIC SEGMENT: exits through transverse foramina of atlas till it peierces dura to enter cranial cavity. Branch: Post. Meningeal. D. INTRACRANIAL SEGMENT: INTRACRANIAL SEGMENT • • Ascends anteriorly + laterally around medulla to reach midline at pontomedullary junction and forms basilar artery with other vertebral a at clivus. BRANCHES: 1. 2. ANTERIOR + POSTERIOR SPINAL A. PICA BASILAR ARTERY BRANCHES: 1. 2. 3. 4. 5. AICA INTERNAL AUDITORY A. SUPERIOR CEREBELLAR A. POSTERIOR CEREBRAL A. MEDULLARY AND PONTINE PERFORATING ARTERIES POSTERIOR CEREBRAL ARTERY • Originates from bifurcation of basilar artery, within interpeduncular cistern (in 15% as direct continuation of pCom) lies above occulomotor nerve and circles midbrain above tentorium. • P1 SEGMENT: – Origin to PCOM. – Posterior thalamoperforators • P2 SEGMENT: – Distal to PCOM – Thalamogeniculate – Posterior choroidal arteries. • TERMINAL CORTICAL BRANCHES. ARTERIAL ANASTOMOSES OF BRAIN A. AT BASE OF BRAIN: I. CIRCLE OF WILLIS II. DEVELOPMENTAL ANOMALIES: (3 transient carotid-basilar anastomoses appear in fetal life) • • • Primitive hypoglossal artery Primitive acoustic artery Persistent primitive trigeminal artery CIRCLE OF WILLIS • Complete in 25%, incomplete in 75%. • Made by – Supraclinoid ICAs – A1 segment of ACA – ACOMs – PCOMs – P1 segment of PCAs ARTERIAL ANASTOMOSES OF BRAIN B. VIA SURFACE VESSELS: • • LEPTOMENINGEAL ANASTOMOSES OF CEREBRUM: ACA MCA PCA OF CEREBELLUM: SUP CEREBELLAR AICA PICA. C. RETE MIRABILE: • ECA MIDDLE MENINGEAL/SUP TEMPORAL A. LEPTOMENINGEAL ACA/MCA. NORMAL VARIANTS OF VASCULAR ANATOMY • ICA: – PERSISTENT EMBRYONIC ARTERIES – ABERRANT PETROUS PART ICA: Courses posterolateral • ECA: – MIDDLE MENINGEAL FROM OPHTHALMIC – VARIATION IN ORDER OF BRANCHING. • CIRCLE OF WILLIS: – HYPOPLASTIC PCOM – HYPOPLASTIC OR ABSENT A1 SEGMENT – FETAL PCA(FROM ICA) WITH ATRETIC P1 SEGMENT – HYPOPLASTIC ACOM. ANTERIOR CEREBRAL ARTERY MIDDLE CEREBRAL ARTERY POSTERIOR CEREBRAL ARTERY CEREBRAL VEINS THANK YOU