Cerebrovascular Anatomy and CVA Examples

Lecture 021125

• Covered in this lecture are Arterial and Venous Vasculature, the Blood Brain Barrier, and examples of CVA

Examples of CVA (Cerebrovascular Accident)

• Examples can include Aneurysm, Atherosclerosis, Dissection, Arterio-Venous Malformation, and Infarction and Ischemia

Arterial Cerebro-Vascular System Branches

• Vertebral and basilar arteries supply cerebellar and cerebral regions and spinal and pontine regions
• Internal carotid arteries supply the cerebral regions
• Circle of Willis facilitates anastomosis of vessels

Circle of Willis

• The vertebrobasilar system includes vertebral and basilar arteries

• key arteries in the vertebrobasilar system consist of:

  • PCA (posterior cerebral artery)
  • SCA (superior cerebellar artery)
  • AICA (anterior inferior cerebellar artery)
  • PICA (posterior inferior cerebellar artery)
  • anterior and posterior spinal arteries

• The internal carotid system includes the internal carotid artery itself

• Key arteries in the internal carotid artery consist of: -posterior communicating artery

  • middle cerebral artery MCA
  • anterior communicating artery
  • anterior cerebral artery ACA
  • ophthalmic artery

Vessel Systems of the Brain

• Internal carotid system includes 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
• Vertebro-basilar system, includes
  • vertebral artery
  • basilar artery
  • spinal artery
  • posterior inferior cerebellar artery
  • anterior inferior cerebellar artery
  • superior cerebellar artery
  • posterior cerebral artery (P1, P2)

Atherosclerosis

• Atherosclerosis at bifurcations of major vessels within the Circle of Willis can pose risks
• The Circle of Willis provides anastomosis for collateral blood supply
• Basilar artery offers no collateral perfusion

Aneurysms

• Aneurysms involve ballooning, such as a berry aneurysm at the base of the brain within the Circle of Willis or micro-aneurysms within the cerebrum.
• Dissections involve bleeding within a vessel, specifically the internal carotid artery
• Arteriovenous malformation occurs within the cerebrum

CVA (Cerebrovascular Accident)

• Risks and complications can arise from Atherosclerosis, Aneurysm, and Arteriovenous Malformation (AVM)
• Atherosclerosis:
  • May lead to occlusive stroke, infarction, or hemorrhage
• Aneurysm and dissection:
  • May lead to hemorrhage and infarction that presents as death of tissue

Case Study

• Patient presented with a history of smoking, atherosclerosis, coronary artery disease, and previous coronary bypass operations, coupled with a sudden onset of explosive headache
• The patient presented with bi-frontal headache, mild nuchal rigidity and was diagnosed with a common aneurysm
• Symptoms included diffuse subarachnoid hemorrhage and hydrocephalus
• Angiogram showed a saccular berry aneurysm in the anterior communicating artery
• Sclerotic plaques weaken vessel wall, leading to aneurysm

Internal Vascular Supply

• Supplied by Internal Carotid and Basilar Arteries
• Internal carotid’s anterior choroidal artery supplies basal ganglia, hippocampus, the posterior limb of the internal capsule
• The M1 proximal branch of MCA supplies lenticulostriate arteries that feed basal ganglia, the posterior limb of the internal capsule
• Proximal ACA - penetrating branches from the recurrent artery of Heubner supplies basal ganglia, limbic structures, and anterior limb of internal capsule
• Basilar Artery supplies: PCA supplies thalamoperforator, thalamogeniculate, and posterior choroidal regions to the thalamus and posterior limb of the internal capsule

Brain Ischemia

• Ischemia: Lack of blood flow to a brain region
• Hypoxia: Lack of oxygenated blood in a 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, cardiac arrest, shock and hypo-perfusion
• Focal cerebral ischemia: Occlusion from embolism, thrombus and vasculitis

Intra-Cerebral Hemorrhage

• Intra-cerebral hemorrhage consists of lacunar infarction with Charcot-Bouchard micro-aneurysm.
• Penetrating arteries to the thalamus, basal ganglia, and internal capsule are end arteries, indicating no anastomosis and no collateral perfusion.
• Pallidal (L) and thalamic (R) hemorrhage result in small lacunes
• posterior limb of internal capsule can leads to pure hemi-paresis with descending motor deficits
• ventral posterior nucleus of thalamus, pure hemi-sensory loss with ascending sensory deficits
• etat lacunaire manifests as progressive dementia, cranial nerve palsies, dysarthria, dysphagia, a positive gag reflex, and emotional imbalance

Case Study: Occlusion of Lenticulo-Striate Branches

• Occlusion of lenticulo-striate branches off left M1 segment in the internal capsule
• The patient presented with a history of diabetes and hypertension, slurred speech leading to dysarthria, right sided weakness, facial weakness sparing forehead, right hemiparesis leading to hemiplegia, and an extension plantar response (Babinski’s sign)

Cortical Supply

• Midline cortical supply: ACA
  • calloso-marginal artery
  • peri-callosal artery
• PCA
  • medial temporal, occipital
• External cortical supply: ACA
  • antero-medial frontal lobe
• MCA
  • M3 (superior), M4 (inferior) lateral frontal, parietal, temporal lobe
• PCA
  • parietal, inferior temporal, occipital

Case Studies: Infarction of Cerebral Arteries

• Case 1 - 40 year smoker showed signs of Lleft leg weakness, mild left arm weakness, Babinski’s sign, poor motor control of the left arm, and mild dysarthria
  • Infarct of right anterior cerebral artery (ACA)
• Case 2 - diabetic, hypercholesterolemia, and coronary artery disease showed sign of blurry vision with right field of view
  • Infarct of left posterior cerebral artery (PCA)
  • No somatosensory or motor defects; infarct of non-cortical MCA or ACA

Watershed Infarction

• Watershed infarction results from hypo-perfusion of border zones. There are 2 types: MCA/ACA and MCA/PCA
• Occlusion of The end vessel leads to focal ischemia
• Aphaasia, proximal limb weakness can result from hypo-perfusion zone infarct

Cerebral Veins

• There are several superior and inferior Cerebral veins along with Sinuses in the brain
• Superior sagittal sinus
• Inferior sagittal sinus
• Straight sinus
• Transverse sinus
• Cavernous sinus
• Superior petrosal sinus
• Inferior petrosal sinus
• Superficial middle Cerebral vein
• Superior anastomotic vein of Trolard
• Cerebral of Galen
• Basal vein of Rosenthal

Venous System

• Superficial veins: superior sagittal sinus and cavernous sinus
• Deep veins: Great vein of Galen
• The great vein of Galen drains into cavernous sinus, superior petrosal sinus and inferior petrosal sinus
• Internal cerebral veins, basal veins of Rosenthal and great cerebral vein of Galen all eventually drain into the Internal Jugular vein
• Other veins that participate in venous drainage consist of inferior sagittal sinus, superior anastomotic vein of Trolard, inferior anastomotic vein of Lobe - ts and torcula (confluence of sinuses)
  • Superior sagittal thrombosis can be identified by an empty delta sign

Blood Brain Barrier

• Blood brain barrier:
  • astrocytes induce endothelial tight junctions (BBB)
  • pericytes maintain the BBB
  • metabolic barrier - MAO
• Exchange from blood/CSF/brain: lipid soluble diffusion, receptor mediated transport and ion channel diffusion
• Functions of CSF: shock absorber, removal of metabolites and pH buffer for blood
• Blood-CSF barrier: -capillary filtration -active epithelial transport
• The CSF has low protein and low ionic content
  • increased CSF protein can indicate meningitis
  • appearance of RBCs indicates infarction or infection

Parkinson's Treatment

• To get dopamine into the brain in Parkinson's treatment
• Step 1: Oral L-DOPA crosses blood brain barrier and is permeable in the brain
• Step 2: Combine L-DOPA with carbidopa to decrease systemic L-DOPA metabolism
• Step 3: L-DOPA is converted to dopamine in the brain via AADC (Aromatic L-Amino acid Decarboxylase)