Lab 11: Blood Supply To The Forebrain

Question 1

Anterior Cerebral Artery

Answer 1

• enters longitudinal fissure
• anterior communicating artery
• cortical branches
• penetration branches=anteromedial group: supply structures in the area of the optic chiasm and the anterior parts of the hypothalamus
• one of these anteromedial penetrating arteries (often the largest) is called the recurrent artery of Heubner

Question 2

Middle Cerebral Artery

Answer 2

• direct continuation of internal carotid artery
• enters the lateral sulcus
• cortical branches
• penetrating branches=anterolateral group (NOTE: the proximal part of the anterior cerebral artery also contributes some branches to this group): lenticulostriate (lateral striate) arteries are named arteries included in this group that supply the interior of the hemisphere

Question 3

Anterior Choroidal Artery (Middle Cerebral Artery)

Answer 3

• a branch of either the internal carotid or middle cerebral artery
• arises distal to the posterior communicating artery
• follows the optic tract and cerebral peduncle as far as the lateral geniculate body
• enters the choroid plexus of the lateral ventricle

Question 4

Posterior Communicating Artery

Answer 4

-joints the posterior cerebral artery to the anterior circulation
-penetrating branches = posteromedial group supplies the crus cerebri, middle and caudal hypothalamus
NOTE: the proximal part of the posterior cerebral artery also contributes some branches to this group

Question 5

Posterior Cerebral Artery

Answer 5

• cortical branches that supply the medial/ventral cortex
• penetration branches=posterolateral group: small penetrating branches that enter the midbrain. Supply parts of the thalamus and the choroid plexus

Question 6

Branches to the Deep Forebrain

Answer 6

• medial striate arteries (anteromedial group): branch from the anterior cerebral and anterior communicating arteries; supply the optic chiasm, anterior hypothalamus; inferior parts of the anterior limb and genu of the internal capsule
• recurrent artery of Heubner: a medial striate Artery that is large, travels laterally and supplies the head of caudate nucleus
• lateral striate arteries (from the anterolateral group): arise mainly from the middle cerebral artery; supply body of the caudate nucleus, lentiform nucleus, and most of the superior part of the internal capsule (anterior limb, genu, posterior limb)
• anterior choroidal artery: which branches from internal carotid or middle cerebral artery. Along its path, this artery supplies: inferior part of lentiform nucleus; inferior part of the posterior limb and retrolenticular and sublenticular fibers of the internal capsule; optic tract; medial temporal cortex; choroid plexus of the lateral ventricle, hippocampal formation; amygdaloid complex
• Posteromedial group: originate from the proximal part of the posterior cerebral and posterior Communicating arteries; supplies the middle and caudate hypothalamus, subthalamic nucleus, substantia nigra and anterior thalamus
• posterolateral group: originates from the distal area of the posterior cerebral artery and includes: small penetrating branches that enter the midbrain as well as circumferential arteries which supply the posterior thalamus

Question 7

Branches to the Cerebral Cortex and Subcortical White Matter

Answer 7

Anterior cerebral artery: travels in the longitudinal cerebral fissure and arches superiorly and caudally over the rostrum of the corpus callosum and divides into:

• pericallosal branch: courses inferior to the cingulate gyrus; supplies medial part of frontal and parietal lobes (anterior cingulate gyrus, anterior corpus callosum)
• callosomarginal branch: courses superior to the cingulate gyrus; supplies paracentral lobule (primary motor and somatosensory cortex) for the lower limb below the knee

Middle cerebral artery: enters and initially branches in the lateral fissure; branches fan out and:

• supply most of the lateral cortex, including: primary motor and somatosensory cortex for upper part of body; primary auditory and auditory associations cortex; motor and receptive speech areas (usually on left side)
• includes Rolandic Branches that supply pre and postcentral gyri

Posterior Cerebral Artery: winds around the midbrain, above the tentorium cerebelli

• has cortical branches supply the medial and inferior occipital lobe and most of the inferior temporal lobe
• a calcarine branch that supplies primary visual cortex

Question 8

Review of Venous Drainage of the Forebrain

Answer 8

Intra-axial veins proper Collect capillary blood which drain into a series of veins: superficial veins drain cerebral cortex and subcortical white matter; and deep veins drain deep structures of the forebrain. These venous systems empty into the dural Venous Sinuses which ultimately empty into extracranial veins (e.g. Internal jugular veins)

Question 9

Superficial Cerebral Veins

Answer 9

• have no valves, lie along the surface of sulci
• located superficial to arteries
• terminate in dural venous sinuses
• include the superior cerebral veins which drain into superior sagittal sinus
• bridging veins between the superficial cerebral veins and the superior sagittal sinus in the subdural space

Question 10

Deep Cerebral Veins

Answer 10

-more consistent in configuration than superficial veins
-drain the deep subcortical structures
-valveless
include:

• internal cerebral veins: are paired, parallel vessels situated lateral to the midline on the roof of the third ventricle; formed at the interventricular foramen by the confluence of septal vein and thalamostriate (terminal) vein; drain parts of internal capsule and basal nuclei; joins with partner on the other side to form the Great Cerebral Vein of Galen
• Great Cerebral Vein of Galen: unpaired; formed by junction of left and right internal cerebral veins; passes inferior to splenium of corpus callosum; joins inferior sagittal sinus to form straight sinus; easily torn
• Basal Vein of Rosenthal: receives vessels that drain part of basal ganglia, internal capsule, medial temporal lobe; drains into great cerebral vein of Galen

Question 11

Bridging Veins

Answer 11

Clinically important. If a force is applied across the long axis of the cranium (e.g. The forehead striking the windshield), bridging veins can tear and extravasated blood accumulates in the potential space between the dura and arachnoid forming a Subdural hematoma