L3 CNS Blood Flow PDF

CNS Blood Supply BEN PISARZ, M.S. B E N J A M I N. P I S A R Z @ L M U N E T. E D U 1/10/25 MED NEURO II 2 Brain and Blood Flow- approximately 20% of all circulation is destined for...

CNS Blood Supply BEN PISARZ, M.S. B E N J A M I N. P I S A R Z @ L M U N E T. E D U 1/10/25 MED NEURO II 2 Brain and Blood Flow- approximately 20% of all circulation is destined for the CNS Loss of blood flow to the brain for 10-15 seconds is enough to cause a loss of consciousness. 5 minutes of interrupted flow is enough to cause irreversible damage. While the total flow of blood to the brain is consistent, local areas of the brain that are active have a higher energy requirement and thus blood flow to those areas can be locally increased. Basis for fMRI. 2 Learning Objectives By the end of today’s lecture students will be able to: 1. Trace the major arterial supply to the cerebral hemispheres and the regions of the brain they supply. 2. Illustrate the pathway of major arterial supply to the cerebellum and brainstem. 3. Recognize arterial branches at the base of the brain including the Circle of Willis. 4. Identify the major sinuses and veins and the areas they drain. 5. Assess clinical findings and presentation of symptoms of cranial hematomas. 3 3 LO1 Arteries supplying the CNS Internal Carotid arteries Branch off common carotid Supplies most of cerebrum Cervical and Petrous segment (no branches) Cavernous segment - branches to supply pituitary, dura of the anterior cranial fossa, trigeminal ganglia Vertebral arteries Branch of Subclavian Supply Brainstem, cerebellum and posterior cortex 4 The Circle of Willis refers to the connection of blood flow between the carotid and the vertebral blood supplies. The circle of willis consists of the anterior cerebral arteries and their communicating branch, internal carotid, the middle cerebral, the posterior communicating arteries, the posterior cerebral and the basilar arteries. The system allows for the shunting of blood flow from one side to the other in case of blockage or decreased pressure in any one of the vessels. Under normal conditions there is very little flow in the posterior communicating arteries and the carotid and vertebral blood flow is not mixed. 4 LO1 ICA and VA give rise to numerous branches that separate the blood supply of the brain into an anterior (ICA) and posterior (VA) circulation Ø anterior circulation is derived from the branches of the ICA : o ant. cerebral art. (ACA) o middle cerebral art. ACA (MCA) MCA PCA Ø posterior circulation is BA derived from the branches of the VA : VA o 2 VAs join to form basilar art. (BA) o BA divides into 2 post. cerebral arts. (PCA) 5 The internal Carotid artery then forms two terminal branches, the anterior cerebral artery and middle cerebral artery. Perforating branches (the anterior choroidal is often referred to as the first perforating branch) are small thin-walled branches off of main arteries that will travel deep into brain and supply internal structures 5 LO3 Circle of Willis 6 1. ICA 2. Middle Cerebral A. 3. Anterior Cerebral A. 4. PCOMM 5. Anterior Choroidal A. 6. Vertebral A. 7. PICA 8. AICA 9. Basilar 10. Superior Cerebellar 11. Posterior Cerebral A. 6  FULL SCHEMATIC 7 Draw this in your own time and label the associated structures 7 LO3 Circle of Willis Main Arteries to know - Anterior Cerebral (ACA) x2 - Anterior communicating x1 - Middle Cerebral (MCA) x2 - Posterior communicating x2 - Posterior cerebral (PCA) x2 Not considered Circle of Willis - Anterior Choroidal x2 - Ophthalmic x2 8 ACA: travels medially, entering the longitudinal fissure then traveling posteriorly following along the corpus collosum. This artery supplies most of the medial surface of the frontal and parietal lobes (and some of the superior surface of these lobes). Anterior communicating: connects left and right anterior cerebral arteries before they enter the fissure. MCA: - travels laterally into the lateral sulcus. The middle cerebral artery has two divisions; the superior division supplies the lateral surface of frontal lobe and the inferior division supplies the lateral surface of the temporal lobe and some of the parietal lobe. Before entering the sulcus, the middle cerebral arteries gives off branches called the lenticulostriate arteries. Post comm: connects MCA to PCA very little flow, travels posteriorly and joins the PCA. PCA: the terminal branches of the basilar artery, the posterior cerebral arteries supply much of the medial and inferior surfaces of the occipital and temporal 8 lobes Notes: Anterior Choroidal: slide 11 Opthalamic: slide 11 ***Under normal conditions there is very little flow in the posterior communicating arteries and the carotid and vertebral blood flow is not mixed. 8  Circle of Willis - variation 9 Common variants in Circle of Willis Full complete circle is only present in 34 percent of individuals 9 LO1 Anterior Circulation Lateral View ACA Internal Carotid Artery, Anterior and Middle Cerebral MCA Arteries Superimposed ICA 10 10 LO1 Main branches of the internal carotid (anterior circulation) Middle Cerebral Artery (MCA) Anterior Cerebral Artery (ACA) Posterior communicating artery Ophthalmic artery Anterior choroidal artery (not shown) 11 Opthalamic: - travels with the optic nerve into the orbit to supply the eyeball, retina and other orbit structures Anterior chorodial artery - travels posteriorly, supplying the optic tract and a number of deep structures such as the choroid plexus in the inferior horn, basal ganglia, amygdala, thalamus, hippocampus and posterior limb of internal capsule 11 LO1 Vascular territories of these arteries on the cortex Middle Cerebral Artery territory Primary motor and sensory for upper limb and face Broca’s and Wernicke’s area (left) FEF Parietal cortex spatial processing (right) MCA (superior) supply Lateral frontal lobes MCA (inferior) supply Lateral temporal lobes/lateral parietal lobes Anterior Cerebral Artery territory Primary motor and sensory for lower limb Hippocampus, Medial (and some Midline thalamus superior) frontal and Inferior and parietal lobes medial temporal Cingulate gyri lobes Occipital lobes Posterior Cerebral Artery Territory 12 Occipital lobes: visual deficits 12 LO1 Deep cerebral blood supply Lenticulostriate supply Basal ganglia Superior internal capsule Anterior choroidal supply (not shown) Basal ganglia Thalamus Posterior limb internal capsule Recurrent artery of Huebner (supply) Basal ganglia Internal capsule 13 Anterior Choroidal posterior limb (inf) 13 LO1 1 Supply of: 1) Anterior Cerebral Artery 2 2) Middle Cerebral Artery 3) Lenticulostriate 4) Posterior Cerebral Artery 5) Anterior Choroidal Artery 5 3 (from internal carotid) 4 MCA, ACA and PCA provide superficial (cortical) and deep (central) branches. 14 14 LO1 PQ 1. A 73-year-old female presents to the emergency department with sudden onset of symptoms which consist of loss of pain and fine touch to the right upper limb and right side of her face with loss of motor function in the right upper limb and right-sided cheek. Which artery is most likely affected? A. Left Anterior Cerebral B. Left Middle Cerebral C. Left Posterior Cerebral D. Right Posterior Inferior Cerebellar E. Right Posterior Spinal 15 15 Summary of cerebral blood supply 16 16 LO1 Watershed areas 17 Watershed infarct Bilateral occur with severe drops in blood pressure ACA-MCA typically seen with occlusion of ICA ACA-MCA- proximal arm and leg weakness “man in barrel" syndrome MCA-PCA- disturbances of higher order visual processing MCA deep and superficial territories there can be watershed infarcts as well. 17 LO1 PQ 2. This artery is part of the deep cerebral blood flow and is associated with supplying blood to the basal ganglia, thalamus, posterior limb of the internal capsule. A. Anterior Choroidal B. Anterior Inferior Cerebellar C. Middle Cerebral D. Posterior Communicating E. Opthalamic 18 18 LO2 Cerebellar blood supply Pre-basilar artery branches Anterior spinal arteries - Supplies ventral spinal cord Posterior inferior cerebellar arteries (PICA) - Supply medial inferior cerebellum; 4th ventricle choroid plexus; lateral medulla Posterior spinal arteries - Supply the dorsal medulla and spinal cord (can also branch from PICA) Basilar artery branches Anterior inferior cerebellar arteries (AICA) - Supply anterior inferior cerebellum; flocculus; caudal pons Pontine arteries - Supply pons and midbrain (many branches) Superior cerebellar arteries (SCA) - Superior cerebellum; rostral pons; caudal midbrain 19 Basilar: The Basilar artery is formed by the fusion of the right and left vertebral arteries and lies in the midline groove of the pons. At its anterior end, it branches to form the posterior cerebral arteries from where it also completes the connection from vertebral blood supply to the carotid blood supply via the posterior communicating arteries 19 LO2 Cerebellar blood supply Pre-basilar artery branches Anterior spinal arteries - Supplies ventral spinal cord Posterior inferior cerebellar arteries (PICA) - Supply medial inferior cerebellum; 4th ventricle choroid plexus; lateral medulla Posterior spinal arteries - Supply the dorsal medulla and spinal cord (can also branch from PICA) Basilar artery branches Anterior inferior cerebellar arteries (AICA) - Supply anterior inferior cerebellum; flocculus; caudal pons Pontine arteries - Supply pons and midbrain (many branches) Superior cerebellar arteries (SCA) - Superior cerebellum; rostral pons; caudal midbrain 20 20 LO2 Brainstem blood supply 21 21 LO2 Lateral Medullary Syndrome (Wallenberg’s Syndrome) Key Clinical Features Ipsilateral loss of pain and temperature to face (spinal track V) Contralateral loss of pain (pinprick) and temp to body (STT) Unilateral Horner’s syndrome – ipsilateral eye (hypthalamo-spinal tract). Common Cause; Infarct involving PICA ! -).I()0#1I,%00)('#2'3,(4*I5 !""#$% OTUV:;% Y=:>Y%?@%L IP%F4R OSS C E "# !"#C'$( &'()*+, Sensory loss !"#$% !""#A%C#D!EEF*+I-#A+.A%.E+LFAM% 22 I!NE#!O ! Alternating syndrome Other findings: Hoarseness, difficulty swallowing, loss of gag reflex (nuc. amb) 22 LO2 3. BRAIN STEM LESIONS Lesions of the brain stem typically result in the loss of some sensory information from the face for pain and temperature Since the brainstem contains both the long ascending sensory and descending motor tracts as well as cranial nerve nuclei (CN lll-Xll) lesions of the brainstem will typically involve sensory and motor loss from both the body and face. Xll Descending Spinal Tract of V X STT M STT L PY PY 23 LO2 3. BRAIN STEM LESIONS Since the STT and descending spinal tract of V are close to each other in the medulla lesions at these levels may involve both pathways. Because the DC-ML has already decussated at the junction of the spinal cord and medulla brain stem lesions involving either or both the DC-ML and STT pathways will result in sensory loss contralateral to the site of the lesion. Descending Spinal Tract of V STT STT M L PY PY STT pain and temp with pain and temp in the face (alternating syndrome) 24 LO2 Medial Medullary Syndrome Key clinical features Sensory Contralateral loss or decrease in vibration and position sense (ML) Motor Contralateral loss or weakness in arm and leg (pyramid) Common Causes Infarct of paramedian branches of the ant. spinal or vertebral artery ! -.,+)I#-.,%II)('#0'1,(2*. !""#$% $%#3*4 "# M !"#C'$( L Sensory loss &'()*+, !"#$% !""#A%C#D!EEF*+I-#A+.A%.E+LFAM% I!NE#!O ! Ipsilateral tongue weakness (CNXll) with tongue deviation toward side of lesion 25  Lesions of the Brain Stem Take Home Summary Lesions in the pons and midbrain will include sensory loss from the face Since the brainstem contains both the long ascending sensory tracts and cranial nerve nuclei for CN lll-Xll lesions of the brainstem will typically involve sensory and motor loss from both the body and face. Since the STT and descending spinal tract of CN V lie close to each other in the medulla lesions at these levels may involve both pathways. Because the DC-ML has already decussated at the junction of the spinal cord and medulla brain stem lesions involving either or both the DC-ML and STT pathways will result in sensory loss contralateral to the site of the lesion. 26  Arteries and cranial nerves Arteries and the relationship to cranial nerves are important Neuroanatomically Anatomical landmarks for orientation Clinically Aneurysms at key locations may compress cranial nerves causing dysfunction 27 Cranial nerve 3 palsy (down and out eye at rest) trochlear nerve and abducens intact caused by pcomm anuerysm 27  Anterior spinal artery (ASA) supplies the anterior 2/3 and the posterior spinal arteries supply the posterior 1/3 of the cross section of the spinal cord. Damage to the ASA leads to loss of motor function as well as the sensations of pain and temperature to the body wall. Damage to the PSA leads to loss of fine touch and proprioception. 28 Different then brain stem, won’t ask about spinal cord 28 LO4 VENOUS SINUSES Superior sagittal sinus Inferior sagittal sinus Dural venous sinuses drain ri into the c ereb internal Straight sinus Falx Cavernous sinuses jugular veins. m oriu Tent belli cere Sigmoid sinus Confluence of sinuses Transverse sinus Internal jugular vein 29 The route of most venous drainage is through dural sinuses and ultimately everything drains into the internal jugular veins. There are two types of cerebral veins, superficial (external) and deep (internal). Superficial veins are on the surface of the cerebrum and mostly empty into the superior sagittal sinus that runs along the longitudinal fissure. Deep veins drain deep cerebral structures and mostly empty into the straight sinus. Major venous sinuses are within dura mater Sinus Flow: Superior Sagittal Drains into confluence Confluence to Transverse Transverse to sigmoid Sigmoid to Internal Jugular Vein Inferior sagittal sinus into confluence Confluence to Transverse Transverse to sigmoid Sigmoid to Internal Jugular vein 29 LO4 Superficial cerebral venous drainage Superior sagittal sinus - Superior drainage pathway Transverse sinus Cavernous sinus - Inferior drainage pathway Superficial middle cerebral v. - Drains temporal lobes into cavernous sinus Superior anastomotic cerebral v. - Connects superior sagittal sinus with superficial middle cerebral v. Inferior anastomotic cerebral v. - Connects the superficial middle cerebral v. with the traverse sinus Other superficial veins are highly variable between brains 30 30  Anastomotic Veins (Dawson’s Fingers) 31 Big indicator of MS 31 LO4 Deep cerebral venous drainage Straight sinus - Drains deep veins into transverse sinus - (Inf. Sagittal sinus) Inferior sagittal sinus Internal cerebral v. - Drains internal structures via: Thalamostriate v. – thalamus; caudate nucleus Septal v. – runs with septum pellucidum Choroid v. – choroid plexus of lateral ventricles Basal v. (of Rosenthal) - Fed by Deep middle cerebral vein - Drains orbital frontal cortex, insula, inferior basal ganglia Great cerebral v. (of Galen) - Short unpaired vein connecting internal cerebral veins/basal veins with straight sinus 32 32 LO4 Cerebral and Bridging Veins Superior sagittal sinus Dur Superior sagittal sinus a re flec ted up Cerebral veins drain into the superior sagittal sinus after piercing the arachnoid. Here, they are called bridging veins. Cerebral veins are in the subarachnoid space. 33 33 LO5 Bridging veins are vulnerable to shearing forces where they pass between the dura mater and arachnoid. Sudden changes in head velocity, as in an automobile accident, can tear these thin-walled veins. Arachnoid This leads to a subdural hematoma: Dura “Bridging vein” 34 34 LO5 Clinical correlation: Subdural Hematomas Subdural bleed Dura Subdural symptoms typically take time to develop since the bleed is under venous pressure. 35 Crescent shaped on a CT – key findings 35 LO5 Clinical Correlation: Epidural Hematoma Epidural bleed due to torn middle meningeal artery. The middle meningeal artery and its branches are vulnerable to damage with skull fractures. Middle meningeal artery on surface of dura mater. 36 Skull fractures can occur anywhere but occur most frequently in the temple region where the bone is thinnest, and where 4 bones come together at the pterion. 36 LO5 Clinical correlation: cerebral arteries course within the subarachnoid space. When they rupture, as in an aneurysm, the result is a subarachnoid hemorrhage, also called a “stroke”. Arachnoid Cerebral arteries Cerebral arteries 37 37 LO5 Stroke Clinical correlation: symptoms with a subarachnoid hemorrhage appear quickly due to arterial pressure. Lumbar puncture can be used to diagnose since blood appears within the CSF fluid around spinal cord. Subarachnoid bleed due to ruptured cerebral artery. 38 Due to rupture of arterial aneurysm Clinical presentation: “worst headache of my life” 85% in anterior circulation Most common Acomm 30% Pcomm 25% MCA 20% Risk factors smoking, hypertension 38 LO1 PQ: A lesion at site C could be caused by a blockage of: A B 1. Anterior Choroidal 2. Penetrating branches of the PCA 3. MCA, inferior branch C D 4. ACA 5. Superior cerebellar a. E 39 It will be clear distinction between lenticulostriate vs anterior choroidal 39 LO4 PQ 4. This venous sinus drains directly into the straight sinus. A. Inferior Sagittal sinus B. Internal Jugular vein C. Transverse sinus D. Sigmoid sinus E. Superior Sagittal sinus 40 40