Brain Vasculature Study Notes

• Study notes generated from text

Arterial Vasculature

• Blood supply via arteries

Examples of CVA

• CVA stands for cerebrovascular accident
• Aneurysms are one example
• Atherosclerosis is a cause
• Dissections may cause CVA
• Arteriovenous malformation is a cause
• Infarction and ischemia may cause CVA

Venous Vasculature

• Blood drainage via veins

Blood-Brain Barrier

• A selective barrier protecting the brain from harmful substances

Arterial Cerebrovascular System - Main Branches

• The cerebrovascular system has vertebral and basilar arteries
• Cerebellar and cerebral arteries arise from the vertebral and basilar arteries
• Spinal and pontine arteries arise from vertebral and basilar arteries
• The system has internal carotid arteries that supply other cerebral arteries
• The Circle of Willis forms an anastomosis between vessels

Circle of Willis

• The vertebral and basilar arteries compose the vertebrobasilar system
• The circle includes the posterior cerebral artery (PCA)
• The circle includes the superior cerebellar artery (SCA)
• The circle includes the anterior inferior cerebellar artery (AICA)
• The circle includes the posterior inferior cerebellar artery (PICA)
• The circle includes the anterior and posterior spinal arteries
• The internal carotid artery system has a circle of Willis
• This includes the posterior communicating artery
• This Circle includes the middle cerebral artery (MCA)
• This Circle includes the anterior communicating artery
• This Circle includes the anterior cerebral artery (ACA)
• This Circle includes the ophthalmic artery

Internal Carotid and Vertebrobasilar Systems

• The internal carotid system provides blood to the following:
• Internal carotid artery
• Ophthalmic artery
• Posterior communicating artery
• Anterior communicating artery
• Anterior cerebral artery (A1, A2)
• Middle cerebral artery
• M1 proximal branch
• M2 segments
• Lenticulostriate arteries
• Anterior choroidal arteries
• The vertebrobasilar system provides blood to the following:
• Vertebral Artery
• Basilar Artery
• Spinal Artery
• Posterior Inferior Cerebellar Artery
• Anterior Inferior Cerebellar Artery
• Superior Cerebellar Artery
• Posterior Cerebral Artery (P1, P2)

Internal Vascular Supply

• The anterior choroidal artery supplies basal ganglia, hippocampus, and posterior limb of internal capsule
• The lenticulostriate arteries (from M1 proximal branch of MCA) supply basal ganglia, posterior limb of internal capsule
• The recurrent artery of Heubner (from proximal ACA) supplies basal ganglia, limbic structures, and anterior limb of internal capsule
• The thalamoperforator, thalamogeniculate, and posterior choroidal arteries supply the thalamus and posterior limb of internal capsule

Ischemia

• Lack of blood flow to the brain region

Hypoxia

• Lack of oxygenated blood in the brain region

Infarction

• Death of brain parenchyma due to circulatory failure

Occlusive Stroke

• Thrombolytic or embolytic closure of a vessel

Hemorrhagic Stroke

• Rupture of blood vessels

Global Cerebral Ischemia

• Diffuse hypoxic/ischemic encephalopathy which can result from:
• Cardiac arrest
• Shock
• Hypo-perfusion

Focal Cerebral Ischemia

• Occlusion from:
• Embolism
• Thrombus
• Vasculitis

Intracerebral Hemorrhage

• Can be caused by lacunar infarction or Charcot-Bouchard micro-aneurysm
• Penetrating arteries to the thalamus are end arteries with no collateral perfusion of basal ganglia, internal capsule
• Small lacunes occur in areas such as the posterior limb internal capsule (descending motor deficit), ventral posterior nucleus of thalamus (ascending sensory loss)
• Etat lacunaire is progressive dementia, cranial nerve palsies, dysarthria, dysphagia, (+) gag reflex, emotional imbalance

Venous System

• Superficial veins include superior sagittal sinus and cavernous sinus
• Deep veins drain into the great vein of Galen
• Superior sagittal, transverse, and sigmoid sinuses drain the venous system
• Cavernous, superior petrosal, and inferior petrosal sinuses drain the venous system
• Internal cerebral veins, basal veins of Rosenthal, and the great cerebral vein of Galen drain the venous system
• All veins eventually drain into the Internal Jugular vein
• Other veins that participate in venous drainage: inferior sagittal sinus, superior anastomotic vein of Trolard, inferior anastomotic vein of Lobe, torcula, confluence of sinuses
• Superior sagittal thrombosis can cause the "empty delta sign"

Blood-Brain and Blood-CSF Barriers

• Astrocytes induce endothelial tight junctions forming the BBB
• Pericytes maintain the BBB
• MAO serves as a metabolic barrier
• CSF provides:
• Shock absorption
• Removal of metabolites
• pH buffering
• The blood-CSF barrier involves:
• Capillary filtration
• Active epithelial transport
• CSF has low protein and low ionic concentrations
• Increased CSF protein indicates meningitis
• Red blood cells in CSF indicate infarction or infection

Parkinson's Treatment

• Oral L-DOPA crosses bloodbrain barrier
• Combine L DOPA with carbidopa to decrease L-DOPA metabolism
• L-DOPA is converted to dopamine