Vascular System of the Brain

What are the two major arterial systems?

Internal Carotid Artery (ICA) System (Anterior Circulation) and Vertebrobasilar Artery (VBA) System (Posterior Circulation)

Where does the Internal Carotid Artery arise from?

Common carotid artery

Where does the Internal Carotid Artery enter through?

Carotid canal

What does the Internal Carotid Artery branch into?

Anterior Cerebral Artery (ACA) and Middle Cerebral Artery (MCA)

What does the Internal Carotid Artery supply?

Most of the telencephalon (frontal, parietal and temporal lobes) and diencephalon

Where do Vertebral arteries originate?

Subclavian arteries

Where do vertebral arteries enter the skull?

Through the Foramen Magnum

Where do Vertebral arteries join, and what do they form?

Pontomedullary junction, form the Basilar Artery

What do the Vertebrobasilar Arteries supply?

Brainstem, cerebellum, occipital lobes, and inferior temporal lobes

Anterior Cerebral Artery Territory

Medial surface of the cerebral cortex, extending back to the parieto-occipital sulcus (specifically supplying the motor and sensory “leg/foot area” of the precentral/postcentral gyri

Deep Branch of the Anterior Cerebral Artery

Recurrent Artery of Heubner, supplies the anterior limb of the internal capsule and head of the caudate

Clinical Deficits in the Deep Branch of ACA

Contralateral lower limb weakness and sensory loss, urinary incontinence, and abulia

Abulia

Lack of motivation/drive from anterior cingulate/prefrontal involvement

Territory of MCA

Runs in Sylvian/lateral fissure to supply the vast majority of the lateral surface of the frontal, parietal and temporal lobes (motor/sensory for face and arm, sparing the leg)

Deep Branches of the MCA

Lenticulostriate Arteries (LSA) from M1 segment supply the basal ganglia (putamen, caudate) and posterior limb of the internal capsule

Clinical Deficits of Superior Division of MCA

Contralateral face/arm weakness and sensory loss; Broca’s aphasia (if dominant hemisphere)

Clinical Deficits of Inferior Division of MCA

Wernicke’s Aphasia (dominant) or hemispatial neglect (non-dominant)

Clinical Deficits of Main Stem/LSA Occlusion in MCA

Contralateral hemiplegia and hemianesthesia (due to posterior limb IC involvement)

Posterior Cerebral Artery Territory

Terminal branches of the basilar artery supplying the inferomedial temporal lobe, occipital lobe (primary visual cortex) and deep thalamic structures

Clinical Deficits of Posterior Cerebral Artery

Contralateral homonymous hemianopsia (visual field defect), thalamic pain syndrome, and alexia without agraphia (due to involvement of the splenium of the corpus callosum)

Where is the Circle of Willis located?

Located in subarachnoid space (interpeduncular fossa) surrounding the optic chiasm and pituitary stalk

What does the Circle of Willis connect?

Anterior and posterior circulations via the Anterior Communicating Artery (ACoA) and Posterior Communicating Arteries (PCoA) to provide collateral circulation

Watershed (Border-Zone) Infarcts

Vulnerable regions at the distal boundaries between major arterial territories (e.g ACA-MCA or MCA-PCA border zones) that suffer ischemia during severe systemic hypertension

Key Brainstem Stroke Syndromes

Weber Syndrome

Lateral Medullary (Wallenburg) Syndrome

Locked-in Syndrome

Weber Syndrome

Involves paramedian branches of the PCA in the midbrain; causes ipsilateral CN III palsy (“blown pupil”, eye down and out)+contralateral hemiplegia (cerebral peduncle)

Lateral Medullary (Wallenburg) Syndrome

Caused by PICA occlusion; damages the nucleus ambiguus (CN IX, X: dysphagia, hoarsness), spinothalamic tract (contralateral body pain/temp loss), vestibular nuclei (vertigo/nystagmus) and sympathetic fibers (ipsilateral Horner syndrome)

Locked-in Syndrome

Caused by basilar artery occlusion damaging the ventral basis pontis; results in total quadriplegia and anarthria while preserving consciousness, vertical eye movements, and blinking

Course of Venous Drainage in the brain

Superficial and deep cerebral veins (which are valveless) drain into dural venous sinuses, which ultimately empty into the internal jugular veins exiting the skull via the jugular foramen

Deep Venous System

Internal cerebral veins merge to form the Great Cerebral Vein of Galen, which drains into the Straight Sinus

Vascular Supply of Spinal Cord

Anterior Spinal Artery

Posterior Spinal Arteries

Artery of Adamkiewicz (Great Radicular Artery)

Anterior Spinal Artery

Formed by branches of the vertebral arteries; supplies the anterior 2/3 of the spinal cord (motor tracts and spinothalamic tracts)

Posterior Spinal Arteries

Supply the posterior 1/3 of the spinal cord (dorsal columns)

Artery of Adamkiewicz (Great Radicular Artery)

The largest anterior segment medullary artery (typically arising from a left intercostal artery between T9 and L2); provides essential blood supply to the lumbar enlargement