Vessels of CNS PDF

Vessels of Central Nervous System  Brain is 2% of the body weight. It requires the 17% of the cardiac output and 20% of the oxygen utilized by the body. The brain receives it’s blood from two pairs of arteries, the internal carotid and vertebral. About 80% of the brain’s blood supply com...

Vessels of Central Nervous System  Brain is 2% of the body weight. It requires the 17% of the cardiac output and 20% of the oxygen utilized by the body. The brain receives it’s blood from two pairs of arteries, the internal carotid and vertebral. About 80% of the brain’s blood supply comes from the internal carotid, and the remaining 20% from the vertebral.  Arteries of the Brain Internal carotid arteries Vertebral arteries Internal carotid 4 segments; – Cervical – Intrapetrosal – Intracavernous – Cerebral(supraclinoid) Intracavernous and cerebral portion are called carotid siphon by neuroradiologists.  ICA Ascends in the neck Perforates the base of the skull Passes through the carotid canal of temporal bone Runs forward through the cavernous sinus Emerges on the medial side of anterior clinoid process by perforating dura. In subarachnoid space, pierce arachnoid and turn posteriorly to medial end of lateral sulcus  Branches of ICA Cervical No branch Petrosal and Small branches to tympanic cavity,cavernous Intracavernous and inferior petrosal sinuses,trigeminal ganglion,meninges of middle cranial fossa segment Ophtalmic Cerebral Posterior communicating Anterior choroidal segment Terminal branches: anterior and middle cerebral arteries  Internal carotid artery Ophtalmic artery Anterior cerebral artery Middle cerebral artery Anterior choroidal artery Posterior communicating artery Ophtalmic artery arises as the ICA emerges from the cavernous sinus Enters the orbit through the optic canal Supplies eye and orbital structures Terminal branches supply the frontal area of scalp, ethmoid and frontal sinuses and dorsum of the nose. Anterior cerebral artery Smaller terminal branch Runs forward and medially superior to the optic nerve and enters longitudinal fissure Joined the ant. cerebral artery of the opposite side by the anterior communicating artery Anterior cerebral artery Cortical branches: supply all medial surface of the cerebral cortex as far back as the parietooccipital sulcus and superior border of the suprolateral surface of the cerebral hemisphere, 2.5cm of strip of cortex on the lateral surface. Leg area of the precentral gyrus  Central branches: supply caudate nucleus, anterior part of lentiform nucleus and anterior limb of internal capsule Branches of anterior cerebral artery Medial striate artery (recurrent artery of Heubner) Orbital branches Frontopolar artery Callosomarginal artery Branches of anterior cerebral artery Medial striate artery – Supplies caudate nucleus, internal capsule, putamen, septal nuclei, inferior surface of frontal lobe Orbital branches – Supplies orbital and medial surfaces of frontal lobe Frontopolar artery – Supplies medial part of frontal lobe Callosomarginal artery – in callosomarginal sulcus; supplies paracentral lobule and parts of cingulate gyrus, leg area Pericollosal artery – Terminal branch; supplies medial surface of parietal lobe, precuneus Occlusion of anterior cerebral artery Unilateral occlusion (distal to Ant. Comm. origin) of Anterior Cerebral Artery – contralateral sensorimotor deficits mainly involving the lower extremity with sparing of face and hands. – Inability to identify objects correctly, apathy, personality changes (frontal & parietal lobes) Middle cerebral artery Largest branch, runs in the lateral sulcus Cortical branches: supply the entire lateral surface of the hemisphere except the narrow strip supplied anterior cerebral artery, occipital lobe, and the inferolateral surface of the hemisphere which are supplied by posterior cerebral artery. – All motor area except Leg area (supplied by anterior cerebral artery). – The occipital pole (macula) is supplied by MCA Middle cerebral artery Central branches: supply lentiform and caudate nuclei, genu and posterior limb of internal capsule (lenticulostriate artery)  Branches of Middle cerebral artery Sphenoidal part – Thalamostriate arteries Insular part – Orbitofrontal artery – Anterior temporal artery – Posterior temporal arteries – Insular artery Terminal part – Pre-Rolandic (precentral) and Rolandic (central) branches – Angular artery – Ant&post. parietal arteries Occlusion of Middle cerebral artery Contralateral hemiparesis and hemisensory loss, mainly face & arm Aphasia if left hemisphere is affected Contralateral homonymus hemianaopia (optic radiation) Anosognosia (not being aware of impaired function ) if right hemisphere is affected. Anterior choroidal artery Posterior communicating artery passes backward, enters runs backward inferior horn of lateral and above ventricle, and ends in choroid plexus. oculomotor nerve It supplies lateral to join posterior geniculate body, posterior cerebral artery. limb of internal capsule, middle 3/5 of crus form part of cerebri,and globus pallidus Circle of Willis.  Vertebral artery Branch of 1st part of subclavian artery Passes through foramina of transverse processes of upper 6 vertebrae Enters skull through foramen magnum Pierces dura and enters subarachnoid space Passes upward,forward and medially on the medulla oblongata Joins the vessel of the opposite side to form basilar artery Vertebral artery Cranial branches Anterior and posterior spinal arteries Posterior inferior cerebellar artery Meningeal branches Medullary arteries Branches of basilar artery Anterior inferior cerebellar artery Labyrinthine artery Pontine arteries Superior cerebellar artery Posterior cerebral artery  Branches of the Vertebral Artery 1. Posterior Inferior Cerebellar Artery (PICA), the largest branch of the vertebral, arises at the caudal end of the medulla on each side. Runs a course winding between the medulla and cerebellum Distribution: a. posterior part of cerebellar hemisphere b. inferior vermis c. central nuclei of cerebellum d. choroid plexus of 4th ventricle e. medullary branches to dorsolateral medulla Branches of the Vertebral Artery 2. Anterior Spinal Artery, formed from a Y-shaped union of a branch from each vertebral artery. Runs down the ventral median fissure the length of the cord. Distribution: a. supplies the ventral 2/3 of the spinal cord.  Branches of the Vertebral Artery 3. Posterior Spinal Arteries (2), originate from each vertebral artery or Posterior Inferior Cerebellar on each side of the medulla. Descends along the dorsolateral sulcus. Distribution: supplies the dorsal 1/3 of the cord of each side. Branches of the Vertebral Artery 4. Posterior meningeal a., one or two branches that originate from the vertebral opposite the foramen magnum. This branch moves into the dura matter of the cranium. 5. Medullary branches, composed of several smaller arteries which originate from the vertebral and it’s branches. These branches supply the pons, medulla and cerebellum.  Branches of the Basilar Artery: Posterior cerebral artery Curves laterally and backward around the midbrain and is joined by the posterior communicating branch of ICA Cortical branches: supply medial and inferior surfaces of temporal lobe and occipital lobe The pole of occipital lobe recieves collateral blood supply from MCA Branches of the Basilar Artery: Posterior cerebral artery Central branches: supply dorsal thalamus, lateral geniculate body, lentiform nucleus, pineal body, hypothalamus and subthalamus Choroidal branch, enters inferior horn, supplies choroid plexus, and also that of 3rd ventricle.  Branches of the Basilar Artery 1. Anterior Inferior Cerebellar Arteries (AICA), originates near the lower border of the Pons just past the union of the vertebral arteries. Distribution: a. supplies anterior inferior surface and underlying white matter of cerebellum b. contributes to supply of central cerebellar nuclei c. also contributes to upper medulla and lower pontine areas  Branches of the Basilar Artery 2. Pontine arteries, numerous smaller branches. Distribution: pons and middle cerebellar peduncle, floor of fourth ventricle and pontine tegmentum  Branches of the Basilar Artery 3. Superior Cerebellar arteries, originates near the end of the Basilar artery, close to the Pons-Midbrain junction. Runs along dorsal surface of cerebellum Distribution: a. cerebellar cortex, white matter and central nuclei b. Additional contribution to rostral pontine tegmentum, superior cerebellar peduncle and inferior colliculus  Branches of the Basilar Artery 4. Posterior cerebral arteries, the terminal branches of the Basilar artery. They appear as a bifurcation of the Basilar, just past the Superior Cerebellar arteries and the oculomotor nerve. Curves around the midbrain and reaches the medial surface of the cerebral hemisphere beneath the splenium of the corpus callosum Distribution: mainly neocortex and diencephalon Branches of the Basilar Artery 5. Labyrynthine arteries, may branch from the basilar, but variable in its origin. Supplies the region of the inner ear  Cerebral arterial circle ( circle of Willis ) Formation: formed by anterior communicating artery, both anterior cerebral arteries, internal carotid arteries, posterior communicating arteries, and posterior cerebral arteries Position: lies on sella turcica around optic chiasma, tuber cinereum and mamillary bodies  Area of oxygendeprives brain Blockage Thrombus Plaque  Microaneurysm Lenticulostriate arteries Subarachnoid hemorrhage Intracerebral hemorhage Arteriovenous malformation Blood vessels of spinal cord Arteries of spinal cord Two sources – Anterior and posterior spinal arteries – Branches of segmental arteries: radicular arteries of posterior intercostals arteries, lumbar arteries, and lateral sacral arteries Posterior spinal arteries Branch directly from vertebral arteries or indirectly from PICA. each descends along the dorsolateral surface of the spinal cord close to the posterior nerve roots. Supply posterior 1/3 of spinal cord. Anterior spinal artery union of 2 small branches from each vertebral artery in the anterior median fissure of the spinal cord Anterior 2/3 of spinal cord Spinal Cord Blood Supply There are several arteries that reinforce the spinal cord blood supply and are termed segmental arteries 1. The Vertebral arteries, spinal branches which are present in the upper cervical (~C3-C5) levels 2. Ascending Cervical arteries, present in the lower cervical areas 3. Posterior Intercostal, present in the mid-thoracic region 4. First Lumbar arteries, present in the mid-lumbar regions Spinal Cord Blood Supply Ventral Dorsal Artery of Adamkiewicz Great anterior artery of Adamkiewicz; – branch from aorta – Lower thoracic and upper lumbar vertebrae levels (T9-T12 75%) – Unilateral, usually left – Major blood supply to the lower 2/3 of spinal cord  3 arteries; 2 posterior and anterior spinal arteries Segmental spinal arteries: enter vertebral canal through the intervertebral foramina, sends branches into the white and gray matter of spinal cord T1-T3 levels are more prone to ischemia due to poor blood supply Cerebral veins Deep and superficial groups No muscle tissue No valve Veins of brain Superficial cerebral veins Drain blood from cortex and subcortical medullary substance and empty into adjacent sinuses of dura mater Veins of brain Deep cerebral veins: drain deeper parts of hemispheres, basal nuclei, internal capsule, diencephalon and choroid plexus, ultimately form great cerebral vein which enter straight sinus Superficial Cerebral Veins Superior cerebral veins Blood from convex and medial surfaces of the hemisphere, Drain into superior sagittal sinus Inferior cerebral veins Basal hemispheric surfaces, ventral parts of lateral surfaces Drain into basal sinuses (cavernous, transverse,petrosal) Superficial middle cerebral vein Lateral surface of hemisphere In the lateral sulcus Anastomotic branches; superior anastomotic (Trolard), inferior anastomotic (Labbe) Deep cerebral veins Internal cerebral veins Unite and form Great cerebral vein Near the midline in the tela choroidea of the roof of 3rd ventricle Basal veins (Rosenthal) Near medial part of anterior lobe Great cerebral vein (Galen) Beneath the splenium of corpus callosum Drains into straight sinus Veins of Spinal Cord The spinal veins arranged in an irregular pattern. The anterior spinal veins run along the midline and the ventral roots. The posterior spinal veins run along the midline and the dorsal roots. These are drained by the anterior and posterior radicular veins. These in turn empty into an epidural venous plexus which connects into an external vertebral venous plexus, the vertebral, intercostal and lumbar veins.