Blood Supply of CNS Prof. K. Sivapalan

Inflow of Blood to CNS The internal carotid arteries enter the cranium through the carotid canal in the base of the skull. Vertebral arteries enter the cranium through the foramen magnum. The vertebral arteries unite to form the Basilar Artery at the lower border of pons. The basilar artery bifurcates into posterior cerebral arteries at the upper end of the pons. Posterior communicating artery connects the posterior cerebral arteries and the carotid arteries. Anterior cerebral arteries arise from the carotid arteries. Anterior communicating connects the anterior cerebral arteries completing the circle of Willis. 5/2/2019 Blood Supply

Anastomosis in Brain Blood supply of the different areas of the brain can be taken over by other main arteries if blocked. After the circle of Willis this does not apply. 5/2/2019 Blood Supply

Branches from Internal carotid Internal carotid artery divides into two- anterior cerebral and middle cerebral. Basilar artery divides into posterior cerebral arteries. The cerebral arteries give rise to two sets of branches- cortical branches ramify on the surface of the cerebral hemispheres and supply the cortex. The central or perforating branches supply the deep structures of the hemispheres. They consist of six main groups of arteries. 5/2/2019 Blood Supply

Perforating Branches Perforating branches consist of six main groups of arteries. Anteromedial – from anterior cerebral and anterior communicating arteries Posteromedial- from posterior cerebral and posterior communicating arteries Right and left anterolateral group[striate arteries] – mainly from middle cerebral artery, some from anterior cerebral. Right and left posterolateral – from posterior cerebral artery. 5/2/2019 Blood Supply

Other Branches of Carotid Artery Anterior choroidal artery arises from the internal carotid artery runs backwards in relation to optic tract, enters the inferior horn of the lateral ventricle. Ophthalmic artery also arises from the internal carotid artery. The recurrent branch of the anterior cerebral artery enters the anterior perforated substance. 5/2/2019 Blood Supply

Branches of the Vertibral Artery Each vertebral artery gives off: Anterior and posterior spinal arteries. These supply medulla and spinal cord Posterior inferior cerebellar artery. This supplies medulla and cerebellum. Basilar artery gives off anterior inferior cerebellar arteries and superior cerebellar arteries. 5/2/2019 Blood Supply

Blood Supply to Spinal Cord Three longitudinal arteries supply the spinal cord: two posterior spinal arteriesalong the posterolateral sulcus the anterior spinal artery along the anterior median fissure. Blood from vertibral arteries reaches only up to the cervical segments. Radicular branches that reach the cord along the roots provide blood to the spinal arteries. 5/2/2019 Blood Supply

Venous Sunuses of the Brain Veins draining the brain open into dural venous sinuses. Superior and inferior sagital sinuses are found in the vault and inferior margins of the Flax cerebri. Straight sinus connects the above along the tentorium cerebelli. The transverse sinus travells along the attachment of the tentorium cerebelli to occipital bone up to the petrous bone and continues as sigmoid sinus. It connects the superior petrosal sinus found along the upper border of the petrous bone. 5/2/2019 Blood Supply

Venous Sunuses ctd. The transverse sinus desends as the sigmoid sinus after joining the superior petrosal sinus. The sigmoid sinus opens into the bulb of the internal jugular vein. Inferior petrosal sinus also opens into the bulb. Petrosal sinuses connect with the cavernous sinus found on either side of the sphenoid bone. 5/2/2019 Blood Supply

Venous Drainage of the Brain Cerebral hemisphers are drained by superficial and deep veins. The superficial veins drain into neighbouring venous sinuses. Veins from upper surface of the cerebellum drain into the straight, transverse and superior petrosal sinuses. Veins from the inferior surface open into sigmoid and inferior petrosal sinuses. 5/2/2019 Blood Supply

Deep Veins Internal cerebral vein begins at the inter ventricular foramen. It has numerous tributaries one of which is the thalamostriate vein, lying between the thalamus and caudate nucleus. The basal vein begins at the anterior perforated substance by the union of, Anterior cerebral vein Deep middle cerebral vein Some inferior striate veins 5/2/2019 Blood Supply

Great Cerebral Vein Two internal cerebral veins join to form the great cerebral vein. Two basal veins that wind around mid brain end in the great cerebral vein. Veins from occipital lobe and corpus callosum open into the great cerebral vein. The great cerebral veins pass posteriorly beneath the splenium of the corpus callosum to end in the straight sinus. 5/2/2019 Blood Supply

Blood for Cerebral Hemisphere Middle cerebral artery- insula, overlying opecula, sensory and motor cortices in the superolateral surface, auditory and speech areas. Anterior cerebral artery- orbital surface of the frontal lobe, medial surface above corpus callosam, up to parieto-occipital sulcus. Motor and sensory areas for leg, foot, perineum, micturition and defecation centers are found in this area. Posterior cerebral artery- cerebral peduncle, optic tract, infero medial surface of the temporal lobe, occipital lobe, inferior temporal gyrus, [?macular area of the occipital lobe by middle cerebral] 5/2/2019 Blood Supply

Blood for Internal Cerebrum Branches of the three cerebral vessels supply the subcortical nuclei and anterior choroidal artery entering through the perforated substances. Anterior perforated substance- striate branches that supply the internal capsule, thalamus and basal ganglia. Posterior perforated substance- branches of posterior cerebral artery- supply the thalamus, basal ganglia and posterior part of the internal capsule. Anterior choroidal artery- chroid plexus, optic tract and radiation, lateral geniculate body and posterior part of the internal capsule, basal ganglia and limbic system 5/2/2019 Blood Supply

Blood for Brain Stem Midbrain- posterior cerebral and superior cerebellar arteries. Pons- pontine branches from basilar artery. Superior cerebellar and anterior inferior cerebellar arteries also contribute. 5/2/2019 Blood Supply

Blood Supply of Medulla Ventrally by branches of the basilar and vertebral arteries. Anterior spinal branch of the vertebral supplies the region next to midline containing pyramid, medial leminiscus and hypoglossal nucleus. [block results in medial medullary syndrome]. Lateral parts supplied by posterior inferior cerebellar artery [block results in lateral medullary syndrome- nucleus ambiguous, uncrossed trigerminal and crossed spinothalamic fibers, descending hypothalamospinal fibers, vestibular nuclei]. 5/2/2019 Blood Supply

Blood Supply of Cerebellum Posterior inferior cerebellar artery- chroid plexus of the fourth ventricle, inferior vermis, back of cerebellar hemisphers. Anterior inferior cerebellar artery- inferior surface of the cerebellar hemisphere and flocculus. Superior cerebellar artery- superior surface of the cerebellum. 5/2/2019 Blood Supply