6 ARTERIAL DISTRIBUTION TO THE BRAIN: FRONTAL VIEW WITH HEMISPHERES RETRACTED

82



Overview of the Nervous System



Coronal Section through the Head of the Caudate Nucleus



Frontal horn of lateral ventricle

Corpus striatum (head of the

caudate and putamen)

Medial and lateral

lenticulostriate arteries



Falx cerebri



Callosomarginal

arteries

and

Pericallosal arteries

(branches of anterior

cerebral arteries)



Limen of insula



Insula

Precentral (prerolandic),

central (rolandic)

and parietal branches

Lateral cerebral

(sylvian) fissure



Temporal branches



Temporal lobe



Middle cerebral artery



Interior carotid artery



Body of corpus

callosum

Internal capsule

(anterior limb)



Septum pellucidum



Rostrum of

corpus callosum

Anterior

cerebral arteries

Recurrent artery

(of Heubner)

Anterior

communicating

artery

Optic chiasm



7.7╇ARTERIAL DISTRIBUTION TO THE BRAIN:

CORONAL FOREBRAIN SECTION

The MCA is the major continuation of the ICA. The MCA

travels through the lateral fissure, supplying branches both to

deep structures and to the convexity of the cerebral cortex.

The lenticulostriate arteries, sometimes called the arteries of



stroke, are thin branches of the MCA that penetrate into the

basal ganglia and internal capsule regions of the forebrain.

A stroke in this territory produces a classic contralateral

hemiplegia )>>spastic) with aphasia, often worse in the upper

�extremity.



Vasculature



Ischemic



Diagnosis of Stroke

Stroke



83



Hemorrhagic



Thrombosis

Infarct



Clot in carotid artery

extends directly to

middle cerebral artery

Embolism



Subarachnoid hemorrhage

(ruptured aneurysm)



Infarct



Clot fragment carried

from heart or more

proximal artery

Hypoxia

Infarcts



Intracerebral hemorrhage

(hypertensive)

Hypotension and poor

cerebral perfusion:

border zone infarcts,

no vascular occlusion



7.8  TYPES OF STROKES

There are two types of strokes, ischemic and hemorrhagic.

The ischemic strokes include thrombotic strokes, embolic

strokes, and hypoxic strokes. The hemorrhagic strokes include



subarachnoid hemorrhages )>>ruptured aneurysm) and intracerebral hemorrhages )>>hypertensive or bleeds associated with

anticoagulant medication).



84



Overview of the Nervous System



Anterior cerebral artery



1

Anterior communicating artery



Middle cerebral artery



Ophthalmic artery



Posterior communicating artery

Caroticotympanic branch of

internal carotid artery



3



Posterior cerebral artery



3



2



3



Supraorbital artery

1



Lacrimal artery



Superior cerebellar artery



Dorsal nasal artery



3



Anterior tympanic artery



Middle meningeal artery



Middle meningeal artery

Maxillary artery



1

1



4



Posterior inferior cerebellar artery



4



5



5



5



5



5

5



Common carotid artery

5



Lingual artery



Anterior spinal artery

Spinal segmental medullary branches

Vertebral artery



Ascending cervical artery

Inferior thyroid artery



Facial artery



Ascending pharyngeal artery



Superior thyroid artery



Vertebral artery



Posterior auricular artery



Occipital artery



External carotid artery

Internal carotid artery



Angular artery

Superficial temporal artery



Basilar artery

Anterior inferior cerebellar artery



Supratrochlear artery



5



Thyrocervical trunk



Common carotid artery

Deep cervical artery

Transverse cervical artery

Suprascapular artery

Supreme intercostal artery

Costocervical trunk



Subclavian artery

Brachiocephalic trunk



Arch

Aorta



Descending

Ascending



7.9  SCHEMATIC OF ARTERIES TO THE BRAIN

This schematic diagram shows the entire layout of the arterial

blood supply to the brain, including anastomoses. The circle of

Willis is present in the upper central portion of this �schematic.



Subclavian artery

Internal thoracic artery



Anastomoses

1 Right–Left

2 Carotid–Vertebral

3 Internal carotid–External carotid

4 Subclavian–Carotid

5 Subclavian–Vertebral



The relative separation of the anterior )>>MCA, ACA) and posterior )>>vertebrobasilar system, PCA) circulation is evident in

this diagram.



Vasculature



85



Vessels Dissected Out: Inferior View

Anterior cerebral artery (A2 segment)

Anterior communicating artery

Anterior cerebral artery (A1 segment)



Medial striate artery (recurrent artery of Heubner)

Anteromedial central (perforating) arteries

Hypothalamic artery



Ophthalmic artery



Anterolateral central (lenticulostriate) arteries



Internal carotid artery

Middle cerebral artery

Posterior communicating artery



Superior hypophyseal artery

Inferior hypophyseal artery



Posterior cerebral artery

(P2 segment)

(P1 segment)



Anterior choroidal artery

Thalamotuberal (premammillary) artery



Superior cerebellar artery

Basilar artery

Pontine arteries

Anterior inferior cerebellar artery



Posteromedial central (perforating) artery

Thalamoperforating artery

Posteromedial central (paramedian) arteries

Labyrinthine (internal acoustic) artery



Vertebral artery



Vessels in Situ: Inferior View

Anterior cerebral artery

Hypothalamic artery

Internal carotid artery



Anterior communicating artery

Optic chiasm

Cavernous sinus



Superior hypophyseal artery



Infundibulum (pituitary stalk) and

long hypophyseal portal veins



Middle cerebral artery



Adenohypophysis

(anterior lobe of pituitary gland)

Inferior hypophyseal artery



Neurohypophysis (posterior lobe of pituitary gland)



Posterior communicating artery

Efferent hypophyseal veins

Posterior cerebral artery



Posteromedial central (perforating) arteries

Superior cerebellar artery

Basilar artery



7.10  CIRCLE OF WILLIS: SCHEMATIC

�ILLUSTRATION AND VESSELS IN SITU

The circle of Willis surrounds the optic tracts, pituitary stalk,

and basal hypothalamus. It includes the three sets of paired

cerebral arteries plus the anterior communicating artery, interconnecting the ACAs, and the posterior communicating

arteries, interconnecting the MCAs and PCAs. The free flow

of arterial blood through the communicating arteries usually

is insufficient to perfuse the brain adequately in the face of an

occlusion to a major cerebral artery; the circle of Willis is fully

patent and functional for free flow through the communicating arteries in only approximately 20% of individuals. The circle of Willis is the most common site of cerebral aneurysms.



CLINICAL POINT

Saccular, or berry, aneurysms account for more than 80% of all intracranial aneurysms; they are outpouchings of cerebral arteries that probably

form over a relatively short period of time )>>days to weeks). The most

likely site of these berry aneurysms is at the junctions of arteries in the

circle of Willis. Rupture of the aneurysm results in arterial bleeding into

the cerebrospinal fluid )>>subarachnoid hemorrhage), which produces

an acute, excruciating headache, nausea, vomiting, signs of meningeal

irritation, and sometimes loss of consciousness. A sudden subarachnoid

hemorrhage may be immediately fatal. Autopsy studies show that most

cerebral aneurysms never rupture. Untreated ruptured aneurysms have

approximately a one third likelihood of rebleeding within 2 months,

sometimes with fatal results; other sequelae are cerebral infarction

and vasospasm of the affected vessel. Treatment sometimes involves

�clipping the aneurysm or occluding it with coils or balloons.



86



Overview of the Nervous System



Anterior parietal branch



Posterior parietal branch



Central (rolandic) branch



Angular branch



Precentral (prerolandic) branch



Terminal cortical branches

of Ieft posterior cerebral artery



Ascending frontal (candelabra) branch

Terminal cortical branches

of anterior cerebral arteries

Lateral orbitofrontal artery



Posterior temporal branches



Left middle cerebral artery

Anterior temporal branches



Left anterior cerebral artery

Anterior communicating artery

Right anterior cerebral artery

Left internal carotid artery



A. Lateral view

Pericallosal artery

Internal frontal branches



Paracentral artery



Posterior

Middle

Anterior



Callosomarginal artery

Frontopolar artery



Precuneal artery

Right posterior cerebral artery

Posterior pericallosal artery

Parietooccipital branch

Posterior temporal branch



Right anterior cerebral artery



Anterior temporal branch

Calcarine branch



Medial orbitofrontal artery

Anterior communicating artery

Recurrent artery (of Heubner)

Right internal carotid artery



B. Medial view



7.11  ARTERIAL DISTRIBUTION TO THE BRAIN:

LATERAL AND MEDIAL VIEWS

A, The MCA sends named branches along the surface of the

hemispheric convexity into the frontal and parietal lobes and

into the anterior and middle regions of the temporal lobes.

Occlusion disrupts sensory and motor functions in the contralateral body, especially the upper extremity, or in the entire

contralateral body if the internal capsule is affected. B, The

ACA distributes to the midline region of the frontal and parietal lobes. Occlusion disrupts sensory and motor functions in

the contralateral lower extremity. The PCA distributes to the

occipital lobe and the inferior surface of the temporal lobe.

Occlusion disrupts mainly visual functions in the contralateral visual field.



Posterior communicating artery



CLINICAL POINT

The MCA is a continuation of the ICA, extending through the lateral

fissure to supply branches to the convexity of the hemisphere, as well

as penetrating branches. Cerebrovascular “strokes” appear in several

forms. Approximately one third are atherosclerotic/sclerotic strokes

)>>usually preceded by a transient ischemic attack); about one third are

embolic strokes; close to 20% are lacunar )>>small distal) infarcts; 10%

are cerebral hemorrhages; and a small percent are ruptured aneurysms

or arteriovenous malformations. Lacunar infarcts are small infarcts

)>>between 3 to 4 μm and 2 cm in diameter) in small penetrating vessels supplying the putamen, caudate, internal capsule, thalamus, pons,

and cerebral white matter. They occur most commonly as atherosclerosis-related infarcts, particularly in the presence of hypertension or

diabetes. Symptoms are determined by which region of the brain is

involved; they can include weakness, hemiplegia, contralateral loss of

sensation, ataxia, and other symptoms.