Blood Supply of the CNS PDF

Blood Supply of the CNS Images from Human Anatomy 6th ed., © 2009, by Martini, Timmins and Talitsch, denoted by “Ma”. Images from Human Anatomy, 2nd ed., © 2008 by McKinley & O’Loughlin, denoted by “Mc”. Images from Grant’s Atlas, 11th ed., by A. Agur, © 2009 denoted by “GA” 1 Intracranial Blood...

Blood Supply of the CNS Images from Human Anatomy 6th ed., © 2009, by Martini, Timmins and Talitsch, denoted by “Ma”. Images from Human Anatomy, 2nd ed., © 2008 by McKinley & O’Loughlin, denoted by “Mc”. Images from Grant’s Atlas, 11th ed., by A. Agur, © 2009 denoted by “GA” 1 Intracranial Blood Supply • Ma22.13 intracranial structures receive blood from two sources: the paired internal carotid As and the paired vertebral As 1. the internal carotid As are branches of the common carotid As • they enter the cranium through the carotid canal Internal carotid A External carotid A Vertebral A 2. the vertebral As are branches of the subclavian As Common carotid A Subclavian A • they ascend in the neck through the foramina transversaria and enter the cranium through the foramen Brachiocephalic trunk magnum alongside the spinal cord 2 These Four Major Arteries Anastomose* at the * flow together: capillary beds may Base of the Brain receive arterial blood from > 1 source FRONTAL LOBE ANTERIOR CEREBRAL A. PITUITARY GLAND INTERNAL CAROTID A. (CUT) MIDDLE CEREBRAL A. TEMPORAL LOBE POSTERIOR CEREBRAL A. POSTERIOR CEREBRAL A. BASILAR A. CEREBELLUM VERTEBRAL A. OCCIPITAL LOBE Mc23.11 ARTERIES OF THE BRAIN INFERIOR VIEW 3 The Circle of Willis ANTERIOR COMMUNICATING A. ANTERIOR CEREBRAL A. • at a branch point, blood flow into each artery is determined by their relative resistance • vascular caliber can change over time in response to changes in vascular resistance INTERNAL CAROTID A. POSTERIOR CEREBRAL A. Mc23.11 • blood does not “circle” in the Circle of Willis POSTERIOR COMMUNICATING A. • this may lead to clinically significant changes in the flow pattern of the Circle 4 Cerebral Vascular Territories Medial surface PCA branches If the cerebral hemispheres are considered to have three surfaces (inferior, medial, & superolateral) and three poles (occipital, frontal and temporal), then their vascular supply can be summarized as follows: ACA and branches Basilar A ACA branches Vertebral A Lateral surface MCA branches Basilar A Artery Surface Pole ACA medial frontal MCA superolateral temporal PCA inferior occipital Think about the functional localization within these vascular territories. Stroke in which vascular territory would lead to: PCA branches Vertebral A • aphasia? • paralysis of the contralateral leg? • paralysis of the contralateral face and arm? 5 Vascular Supply of the Brainstem and Cerebellum • the midbrain is supplied by the PCAs • the pons is supplied by the BA PCA • the cerebellum is supplied by branches of the vertebral and basilar As • the medulla is supplied by the VAs and their branches • a stroke in which vascular territory might lead to: BASILAR A. VERTEBRAL As Mc23.11 – strabismus, diplopia, enlarged pupil and ptosis? – difficulty with speech and swallowing? • the vertebral arteries give rise to the unpaired anterior spinal artery and the CEREBELLAR As paired posterior spinal arteries….. 6 Blood Supply of the Spinal Cord POST. SPINAL As Branches of the vertebral arteries form: 1. the single midline anterior spinal artery located in the ventral median fissure • it supplies the ventral and lateral columns of white matter and the ventral grey horns • What pathways would be affected by a stroke in the anterior spinal artery territory? 2. the bilaterally paired posterior spinal arteries located in the dorsolateral sulcus ANT. SPINAL A Mc16.T1 • they supply the dorsal white columns and the dorsal grey horns • What pathways would be affected by a stroke in a posterior spinal artery? 7 Spinal Cord Blood Supply is Reinforced • at cervical levels by branches of the vertebral As • at thoracic levels by branches of the intercostal As • at lumbar levels by branches of the lumbar As B These form: A. radicular As which supply the spinal nerve roots B. anterior and posterior segmental medullary As, which feed into the anterior and posterior spinal As A GA4.47 8 Meninges & Intracranial Bleeds A. Extradural hematoma • torn meningeal A. usually with head trauma • blood btw periosteum & bone GA7.13 B. Subdural hematoma • torn cerebral vein as it crosses from subarachnoid space to dural venous sinus • blood btw dura & arachnoid C. Subarachnoid hemorrhage A B • ruptured cerebral A. • blood in subarachnoid space C 9 Meninges & Intracranial Bleeds: CT extradural hematoma • lens-shaped • respects suture lines Case courtesy of Dr Sandeep Bhuta subdural hematoma subarachnoid hemorrhage • crescent-shaped • gyral enhancement • does not respect suture lines Case courtesy of Dr Andrew Dixon Case courtesy of Prof Peter Mitchell 10 Aneurysm and Embolism Aneurysm: dilation of vessel wall • cerebral aneurysms within skull • may compress adjacent structures (such as a cranial nerve), causing mass effects • ruptured aneurysm 2nd most common cause of subarachnoid hemorrhage • frequently located at branch points Embolism: occlusion of A by material flowing in blood Case courtesy of Dr Bruno Di Muzio (clot, tumor cells, clump of bacteria, air, plaque fragments) • cerebral embolism within the skull • leads to infarction, ischemia, necrosis • deficits reflect location of infarct • thrombus: embolism composed exclusively of blood products • transient ischemic attack (TIA) result in no lasting deficit • ischemic stroke vs. hemorrhagic stroke 11