Anat 6.2 Blood Supply of CNS_zulueta

Anatomy 6.2 January 24, 2012

Blood Supply of the CNS Dr. Zulueta

Group 5 | Dave, Bamba, Precious, Jaela Page 1 of 10

OUTLINE

I. The Brain II. Internal Carotid Artery

A.Middle Cerebral Artery B.Anterior Cerebral Artery

III. Vertebral Artery System A. Posterior Cerebral Artery IV. Circle of Willis A. Middle Meningeal Artery V. Venous Drainage of the Brain VI. The Spinal Cord

Objectives: • Describe the origin and course of the arterial blood supply of the brain: o Internal carotid artery system o Vertebral artery system o Circle of Willis

• Describe the general distribution of the different branches of arteries that supply the various regions of the brain

• Describe the venous drainage of the brain • Describe the arterial supply and venous drainage of the spinal cord

* Texts in Comic Sans MS are from the lecture. o Ma’am gave the lecture with mostly pictures so most texts lifted from

the audio are describing figures. *Texts in Times New Roman are lifted from the book

I. The Brain

• One of the most metabolically active organs of the body consuming large amounts of oxygen and glucose requires continuous blood flow

• It uses 20% of the body's oxygen consumption and up to 2/3 of the liver's glucose production. As the brain only stores minimal amounts of oxygen and glucose, it needs a continuous blood flow to supply the brain with them. (If you lose blood supply to any area of the brain, you’d lose consciousness for 15 seconds. If you lose blood supply for 3-‐5 minutes, you’d be in coma.)

• Any damage to the brain is irreparable • Diving reflex o Blood flow is concentrated on areas which needs continuous blood supply (brain & heart) when in shock

o Usually kidneys are the ones depleted by blood supply • Arterial supply consists of 2 major interconnected systems: o Internal Carotid System(Anterior) o Vertebral Artery System(Posterior)

Some books say basilar artery system, the basilar artery is formed by the union of two vertebral arteries, so it’s the same actually

The vertebral artery arising from subclavian artery pass through vertebral foramen and pass through the biggest foramen (foramen magnum)

Vertebral veins don’t pass through foramen magnum, only vertebral arteries

This figure shows the origin of both systems - the anteriorly placed INTERNAL CAROTID SYSTEM supplies most of the TELENCEPHALON and the DIENCEPHALON, while the posteriorly placed VERTEBRAL ARTERY SYSTEM or the vertebral-basilar system supplies the SPINAL CORD, the BRAINSTEM, the CEREBELLUM and the INFERIOR and POSTERIOR parts of the CEREBRUM. The internal carotid, along with the external carotid, which supplies the face, the scalp and other extracranial structures, arises from the COMMON CAROTID in the neck.

• Start in the neck from the bifurcation of common carotid artery into Internal Carotid Artery + External Carotid Artery

• Perforates the skull through Carotid canal of the temporal bone in the floor of the middle cranial fossa, passes forward through the cavernous sinus just lateral to the sellaturcica

• Turns/bends medial to the anterior clinoid process and perforates the dura mater

• Have many turns called carotid siphon (only in radiographs) • Divides into the anterior and middle cerebral arteries Major Intracranial Branches of ICA before it terminates: • Hypophyseal arteries o Supply the pituitary glandand constitute part of the hypophyseal portal system

• Ophthalmic artery o Will give rise to central retinal artery (the sole supply of the retina, the nervous part of the eye and essentially you will be blind if occluded). Terminal branches also supply the frontal scalp, ethmoid and frontal sinuses, and the dorsum of the nose.

• Posterior communicating artery o Which anastomoses with the posterior cerebral artery forming part of the circle of Willis

II. INTERNAL CAROTID ARTERY

Fig. 1 Blood Supply to the CNS

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• Anterior choroidal artery o Supplies the choroid plexus(secretes Cerebrospinal fluid) in the inferior horn of the lateral ventricle, the optic tract, and parts of the thalamus, basal ganglia, and the ventral part of the internal capsule.

o It varies a great deal in size and importance in different individuals and may instead branch from the middle cerebral artery.

• Anterior cerebral artery (ACA) o When ICA goes up near interhemispheric fissure. Its cortical branches supply the entire medial surface of the cerebral cortex as far back as the parietooccipital cortex. Also supplies the “leg area” of the precentralgyrus.

• Middle cerebral artery (MCA) o When the ICA branches to the lateral sylvian fissure. o Largest branch of the ICA and its cortical branches supply the

entire lateral surface of the hemisphere except for the portion supplied by the anterior cerebral artery (ACA), the occipital pole, and the inferolateral surface supplied by the posterior cerebral artery (PCA).

This figure shows the branches of both the ICAs seen inferiorly from the base of the brain -‐ the ophthalmic, the posterior communicatingthe anterior cerebral, and the middle cerebral arteries.

Side Note: Ma’am discussed about how to locate the cranial nerves:

• CN I o There are two boobs (mammillary bodies) - two pairs of boobs

in the brainstem which are Superior and Inferior colliculi. You’ll see olfactory tract and bulb (must know the difference) are beside Interhemispheric fissure. The free nerve endings are actually in the nose.

• CN II o Optic nerve and optic chiasm- ma’am differentiated the two

with the optic tract • CN III o Upper pons (rostral pons) – occupied by the CN III

(Oculomotor nerve) • CN IV o Very small nerve arising from posterior part of brain –

Trochlear nerve (CN IV) – usually like a strand of dirt (as thin as the strand of hair

• CN V o Occupying lateral pons - motor and sensory component

• CN VI Pons and medulla junction o pontomedullary junction in between is the Abducens nerve (CN

VI) • CN VII, VIII, IX, X o Lateral pontomedullary junction – VII and VIII are always

together Facial Nerve (CN VII) the biggest while IX and X are together

• CN XI o Dorsolateral sulcus – you will see rootlets of Spinal Accessory

Nerve which innervates trapezius and sternocleidomastoid • CN XII o Ventrolateral sulcus– you will see rootlets of Hypoglossal

nerve which innervates all intrinsic muscles except palatoglossus

Fig. 3B Arterial Supply

Fig. 2 Branches of Internal Carotid Artery

Fig. 3A Arterial Supply


A. Middle Cerebral Artery • “Direct communication” of the ICA • Supplies the dorsolateral surface of the cerebral hemispheres o The MCA is regarded as the direct communication of the INTERNAL CAROTID ARTERY, passing laterally to the Sylvian fissure and is distributed in a fanlike fashion supplying the dorsolateral surface of the cerebral hemisphere.

• Branches from stem or M1 segment (initial part of the MCA o As it passes laterally, the stem gives off a series of 6-12 long,

small diameter penetrating vessels that travel upward to supply the basal ganglia and much of the internal capsule called the LATERAL STRIATE ARTERIES (Together with the medial striate arteries, which are branches of the ACA also supplying the basal ganglia and internal capsule, they are collectively called LENTICULOSTRIATE ARTERIES)

o Once in the Sylvian fissure itself, the MCA stem divides into two main cortical branches that supply the entire lateral surface of the brain as well as the insula: Superior (upper or suprasylvian) MCA branch Inferior (lower or infrasylvian) MCA branch

• MCA supplies: 1. Inferior frontal gyrus o BA 44 & 45 (Motor speech area/Broca’s area) Function: Language expression located at the back of the temporal lobe and traverse the gyrus of Heschel (Wornikke’s area BA 22

2. Precentralgyrus o BA 4 (Primary motor area)

3. Postcentralgyrus o BA 3, 1, 2 (Primary somatosensory area)

4. Superior temporal gyrus o BA 22 (Wernicke’s area) Function: Language comprehension

5. Frontal Eye fields o BA 8 This can also be affected if MCA occluded

On this lateral view of the cerebral hemisphere, in blue is seen the superior or suprasylvian branches of the MCA supplying the inferior and lateral frontal lobe and the anterolateral parietal lobe and the inferior or infrasylvian branches of the MCA supplying the lateral temporal, the lateral occipital and the posterior parietal lobes.

KEY FUNCTIONAL AREAS OF MCA: • Superior branches

o Sensorimotor cortex (except legs) -‐ surrounding the Rolandic fissure

o Frontal eye fields-‐ important for bilateral eye coordination

o Broca’s area (language expression) • Inferior branches

o Wernicke’s area (language comprehension) o Auditory cortex o Optic radiations

Fig 5. Branches of ICA

Clincial Correlation

Occlusion in the MCA may produce: • Severe contralateral hemiparesis (marked in UE and face) • Contralateral sensory loss mainly the face and the arm • Severe aphasia (if dominant hemisphere is involved

Broca’s/Wernicke’s) problem in understanding and speaking If there is occlusion in UE than L – occlusion in MCA LE than UE – more ACA than MCA involvement Only weaness (paresis) not paralysis, why is that? If you affected the peripheral nerve itself, for example you have affected the radial nerve. Radial nerve supplies the upper extremities such that if you affected it, there is difficulty in extension of the arm and forearm and there is paralysis. But if you affected only the pathway, (will be discussed by Dr. Calilao on Motor Pathway) you will only have weakness.

B. Anterior Cerebral Artery

• is a smaller branch of the Internal Carotid Artery that passes rostromedially, dorsal to the optic nerve and approaches the corresponding artery of the opposite side along the interhemispheric fissure

• Anterior branch of Internal carotid artery supplying the medial aspect of the frontal and parietal lobes

• Branches: o Anterior communicating artery -‐ which allows collateral flow into the opposite hemispheres if the ICA is occluded on either side.

o Orbital branches and frontopolar artery o Callosomarginal artery o Pericallosal artery

Fig. 4 Right Lateral view of right hemisphere


o Medial striate artery or recurrent artery of Heubner (part of the lenticulostriate arteries) is an early branch near the base of the artery which sends

off deep penetrating branches to supply the anteromedial part of the HEAD OF THE CAUDATE NUCLEUS, adjacent parts of the INTERNAL CAPSULE and PUTAMEN, and parts of the SEPTAL NUCLEI.

On the medial view of the cerebral hemisphere, the Ant CEREBRAL Artery sweeps forward into the interhemispheric fissure and then runs up and over the genu of the corpus callosum, giving off orbital branches and the frontopolarartery supplying the orbital, the frontal pole and the medial aspect of the frontal lobe. As it turns backwards, it forms one branch that stays immediately adjacent to the corpus callosum (the pericallosal artery) while a second branch runs in the cingulate sulcus just superior to the cingulategyrus (the callosomarginal artery) KEY FUNCTIONAL AREAS OF ACA: • Septal area • Sensorimotor cortex for the lower extremities • Motor planning areas in the medial frontal lobe anterior to

the precentral gyrus

III. VERTEBRAL ARTERY SYSTEM

The VERTEBRAL ARTERIES usually arise from the subclavian arteries. They course through the CERVICAL TRANSVERSE FORAMINA, run medially and ascend into the FORAMEN MAGNUM where they pierce the dura and enter the cranial cavity. They would then join to form a SINGLE BASILAR ARTERY, which would later bifurcate to form the POSTERIOR CEREBRAL ARTERIES, whose branch the POSTERIOR COMMUNICATING ARTERY joins with the ipsilateral INTERNAL CAROTID ARTERYjoining both systems. The Vertebral Artery System is from the 1st part of Subclavian

artery. It: • Perforates the intervertebral foramen of the upper 6 cervical vertebrae

• Enters cranial cavity through the foramen magnum [medulla + vertebral artery]

• Terminates into a big artery at the level of the pons „³ Basilar artery

• The entire blood supply of medullary oblongata, pons, mesencephalon and cerebellum

Divided into 2 Branches 1. Vertebral artery • ascend on the ventrolateral surface of the brainstem Branches are: • Spinal arteries-‐ 2 posterior and 1 anterior • A pair of POSTERIOR SPINAL ARTERIES o branches and descends along the posterolateral surface

of the spinal cord AND two anterior branches join to form a single midline ANTERIOR SPINAL ARTERYthat supplies the medial regions of the lower medulla and the upper spinal cord. These arteries form an ANASTOMOTIC system with the RADICULOSPINAL ARTERIES, which supply the spinal cord

• Meningeal arteries supply the bone and dura mater in the posterior cranial fossa

• Posterior inferior cerebellar arteries (PICA) o Supplies inferior and posterior surface of the cerebellum, lateral 1/3 of medulla and the choroid of the 4th ventricle

• Medullary (bulbar) branches o Small branches that are distributed to the medulla oblangata

CLINICAL CORRELATON Occlusion in the ACA may produce:

• Contralateral hemiparesis and hemisensory loss greatest in the lower limb

• Inability to identify objects correctly, apathy and personality changes (frontal and parietal lobes)

• Inhibition of primitive reflexes in the frontal lobe such as rooting reflex

Fig. 6 Medial View of Cerebral Hemisphere

Fig.7 Vertebral Arteries


2. Basilar artery -‐ Formed by fusion of the two vertebral arteries at medullary pontine/pontomedullary junction and further divided into(arranged from caudal to rostral): • Anterior inferior cerebellar arteries (AICA) o At point of fusion o supply the lateral region of the caudal pons, upper medulla, and portions of the inferior surface of the cerebellum;

• Internal auditory (labyrinthine) arteries o Enter internal acoustic meatus with CN 7 and 8 o Sometimes arise from AICA o Supplies the inner ear

• Pontine arteries o paramedian, circumferential (short and long) o have paramedian branches supplying the medial pons, short circumferential branches supplying the ventrolateral surface of the pons and long circumferential branches which anastomose with the AICA and the superior cerebellar arteries to supply most of the pontinetegmentum;

• Superior cerebellar arteries o Before termination o At upper pons and end at dorsal surface of cerebellum, pons, and superior cerebellar peduncle

o Supplies rostral pons, superior surface of the cerebellum, pineal gland, and the superior medullary velum.

• Posterior cerebral arteries (PCA) o terminal branches of the basilar artery.

A. Posterior Cerebral Artery [PCA] • Terminal branch of the basilar artery • Cortical brances supply the inferolateral and medial surfaces of the

temporal lobe (visual cortex). Central branches supply parts of the thalamus and the midbrain. A choroidal branch supplies the choroid plexus and third ventricle

• From parieto-‐occipital sulcus and posterior to it (Preoccipital notch)

• Also supplies the Reticular Activating System (RAS) for maintenance of consciousness

• Branches: o Calcarine artery

An important branch of the Post Cerebral Artery which supplies the visual cortex at the occipital lobe.

o Posterior choroidal arteries Arise from the Posterior Cerebral Art to supply portions of the midbrain, the thalamus, and the choroid plexus of the 3rd ventricle.

*So the main blood supply of the choroid plexus at different levels are:

(lateral ventricles, anterior choroidal a. [ICA (or MCA)]; 3rd ventricle, posterior choroidal a. [PCA]; 4th ventricle, PICA o Deep perforating branches-‐ As each Post Cerebral Artery passes around the cerebral peduncles, it forms a series of branches to the midbrain and gives rise to Deep perforating branches

Supply much of the hypothalamus and the thalamus (of the diencephalon). The small branches to the midbrain supply especially the RETICULAR ACTIVATING SYSTEM (or RAS) whose function is maintenance of consciousness.

KEY FUNCTIONAL AREAS OF PCA: • Diencephalon: All with the word “thalamus” • Midbrain • Primary visual cortex • Hippocampal formation (memory)

IV. CIRCLE OF WILLIS

• Also called “circulus arteriosus” • Formed by the junction of the basilar artery and the 2 ICAs through the presence of 2 posterior and 1 anterior communicating arteries

• Gives of 2 types of arteries: 1. Central 2. Cortical

**Aside from the cortical branches from the different arteries, which form part of the circle, there are CENTRAL ARTERIES which penetrate the substance of the brain and supply deep structures. The 2 groups of central arteries within the circle itself are the ANTERIOR MEDIAL and the POSTERIOR MEDIAL GROUPS.

CLINICAL CORRELATON Occlusion in the PCA may produce:

• Contralateral homonymous hemianopsia = Bigger blindspot -‐Due to occlusion of Calcarine artery

-‐Remember! NOT BLINDNESS -‐It is the occlusion of OPTHALMIC ARTERY that causes blindness • Bilateral occlusion: defect of memory

Fig. 8 Vertebral Artery System

Fig. 9 Vertebral Artery System (Gross)


• Little exchange between brain halves (functionally separate): equalize flow but functionally inadequate

• Compensates if there is occlusion to other arteries • Encircles the optic chiasm, tuber cinereum and interpeduncular region

• Anteromedial group – Central arteries arise from anterior communicating artery and ACA

• Posteromedial group – Originates from PCA and posterior communicating arteries

Notes: The circle of Willis is highly over-rated as a source of effective collateral circulation. Normally, there is little exchange of blood between brain halves because of the equality of blood pressure. Blood normally does not flow around the arterial circle. Though interconnected, the two systems are functionally separate. The anastomotic channels do serve to equalize flow to various parts of the brain and prevent neurological damage. However, the communicating arteries are often functionally inadequate if occlusion occurs acutely. In fact, various combinations of hypoplastic and asymmetrical arterial circles commonly occur.

Table 1. Arteries to Specific Brain Areas Corpus striatum &

internal capsule Lenticulostriate(supplied mainly

fromlateral striate from MCA and medial striate from ACA) and anterior choroidal arteries (from ICA)

Thalamus PCA (from basilar-vertebral system),

posterior communicating (from ICA)

Midbrain PCA, superior cerebellar (both from basilar-vertebral system)

Pons Superior cerebellar arteries, Pontine

a. and AICA (from basilar-vertebral system) and PICA (from vertebral)

Medulla oblongata AICA

PICA Basilar

Vertebral Ant and Post Spinal

Cerebellum Superior cerebellar, AICA and PICA

Fig. 11 Arteries to Specific Brain Areas

• Periosteal branch of the external carotid artery • supplies no CNS tissue • enters the cranial cavity through the foramen spinosum • usually ruptured by fracture of the lateral skull vault • bleeding between the dura and overlying skull(extradural or epidural hematoma)

V. VENOUS DRAINAGE OF THE BRAIN • Do NOT run along course of cerebral arteries • Devoid of valves • External veins divided into superficial and deep groups, which drain the cortex and subcortical white matter areas respectively, and piercing the arachnoid and dura mater, they drain into the dural venous sinuses and ultimately into the internal jugular veins. o Deep Cerebral Veins

It just follows venae comitantes; will eventually drain into that set of veins

A. Middle Meningeal Artery

1. Anterior cerebral artery (callosomarginal and pericallosal arteries)

2. Middle cerebral artery 3. Posterior cerebral artery

4. Medial striate arteries to the internal capsule, globuspallidus and amygdala

5. Lateral striate arteries to the caudate nucleus, putamen and internal capsule

Figs. 12 A and B. Venous Supply of the Brain

Fig. 10 A and B The Circle Of Willis

A

B


o Branches of Superficial Cerebral Veins: External cerebral veins

Superior cerebral veins – empty into superior sagittal sinus Superficial middle cerebral vein – drains lateral surface of cerebral hemisphere and empties into the cavernous sinus

Deep middle cerebral vein – drains the insula Basal veins

from anterior cerebral, striate and deep middle cerebral veins and empty into the great cerebral vein; drains into straight sinus

Internal cerebral veins From thalamostriate, septal and choroidal vv.

Great cerebral vein of Galen formed by the 2 internal cerebral veins and empty into the straight sinus

The superior cerebral veins drain the cortex and pass upward to empty into the superior sagittal sinus. The superficial middle cerebral veinruns inferiorly in the lateral sulcus following the course of the middle cerebral artery and drains the lateral surface of the cerebral hemispheres emptying into the cavernous sinus. A superior anastomotic vein may connect the superficial middle cerebral vein with the superior sagittal sinus.

The internal cerebral vein drains the interior of each hemisphere while the basal veindrains the cerebrum anteriorly. These two empty into the great cerebral vein of Galen, which in turn drains into the straight sinus. Take note that the superficial and deep cerebral veins are interconnected by numerous anastomotic channels. Veins to specific brain areas o Midbrain – drained by veins that open into the basal or great

cerebral veins o Pons- drained by veins that open into the basal vein, cerebellar

veins, or neighboring sinuses o Medulla oblongata – drained by veins opening into the spinal

veins and neighboring sinuses o Cerebellum – drained by veins emptying into the great cerebral

vein or adjacent sinuses Dural Venous Sinuses o Superior sagittal sinus

Runs along the superior margin of the falx cerebri from the foramen caecum to the confluence.

o Inferior sagittal sinus Runs along the inferior border of the falx cerebri and caudally joins the RECTUS or STRAIGHT SINUS, which is located at the junction of the falx cerebri and the tentorium cerebelli and then empties into the confluence.

o Rectus (straight) sinus At the junction of falxcerebri and tentorium cerebelli Empties into the confluence

o Confluence of the sinuses located near the internal occipital protuberance where the superior sagittal, the straight, the occipital and the transverse sinuses meet (SST)

o Transverse sinuses arise laterally from the confluence and curve downward and backward as the SIGMOID SINUSES, which eventually open into the INTERNAL JUGULAR VEIN.

o Sigmoid sinuses Turned backwards Pass into jugular foramen (not the internal jugular vein) Eventually drain into Internal jugular vein

o Cavernous sinus an irregular network of communicating venous channels on

either side of the sphenoid sinus, the sellaturcica, and the pituitary gland. It encloses the INTERNAL CAROTID ARTERY and CRANIAL NERVES 3, 4, ophthalmic 5, and 6. The cavernous sinus of each side is connected with the other by the basilar venous plexus and venous channels running anterior and posterior to the hypophysis.

A

B


*note: The SUPERIOR PETROSAL SINUS connects the cavernous sinus with the transverse sinus, while the INFERIOR PETROSAL SINUS connects the cavernous sinus with the bulb of the internal jugular vein.

The cavernous sinus also receives anastomotic branches from the veins draining the face and maxilla. Also note that the brainstem and the cerebellum are drained by numerous veins that parallel the arteries and form the BASILAR VENOUS PLEXUS, which also empties into the great cerebral vein via the basal veinsor the internal cerebral veins. The basilar venous plexus and the occipital sinus also make connections with the internal vertebral or epidural venous plexus. The significance of this I will point out when we discuss the venous drainage of the spinal cord.

VI. THE SPINAL CORD • Blood supply: perforating vessels from network of pial arteries o 1 anterior and 2 posterior spinal arteries (insufficient to supply the cord beyond the cervical levels.) 1 anterior spinal artery = supply anterior horn, lateral horn, central gray and basal part of the posterior horn

2 posterior spinal arteries = supply Posterior horn and posterior funiculi

o Radicular arteries supply the NERVE ROOTS Branch off from the vertebral/cervical arteries in the neck, intercostals arteries in the thorax, lumbar arteries in lumbar region and the abdominal aorta

o Radiculospinal or segmental medullary arteries – supply the RADICULOSPINAL or SEGMENTAL MEDULLARY ARTERIES arise from branches of the aorta and anastomose with the anterior and posterior spinal arteries at different levels

each supply about 6 spinal cord segments with the exception of the GREAT ANTERIOR SEGMENTAL MEDULLARY ARTERY OF ADAMKIEWICZ, which usually enters the left second lumbar ventral root, ranging between T10-‐L4, and supplies most of the caudal 1/3 of the cord

*The anterior spinal artery forms a circumferential plexus with the posterior spinal arteries called the VASOCORONA. * The anterior spinal artery supplies the anterior 2/3 of the cord including the base of the posterior horn, while each posterior spinal artery supplies the ipsilateral posterior horn and dorsal columns. *Below the cervical level, the RADICULOSPINAL or the SEGMENTAL MEDULLARY ARTERIES supply both the roots and the cord as they join with the spinal artery, augmenting its path. *Each of these radiculospinal arteries supply about 6 spinal cord segments with the exception of the GREAT ANTERIOR SEGMENTAL MEDULLARY ARTERY OF ADAMKIEWICZ, which usually enters the left second lumbar ventralroot, ranging between T10-L4, and supplies most of the caudal 1/3 of the cord.

Fig. 15 Dural Venous Sinuses of the Brain

Fig. 16 Anterior Blood Supply of the Spinal Cord


*Along its course, the spinal cord is supplied anteriorly and posteriorly from arteries which enter the spinal canal through the intervertebral foramina in company with the spinal nerves.

CLINICAL CORRELATION

• Any infection from angular vein or facial vein can enter cavernous sinus = Cavernous sinus thrombosis

• Each side is connected by basilar venous plexus • Where ophthalmic vein and sphenoparietal sinus drain • Drain into the superior and inferior petrosal sinuses • Superior petrosal drains into sigmoid „³ IJV „LInferiorpetrosal drains directly to IJV

• Emissary Veins -‐No valves -‐For emergency drainage in case IJV is occluded -‐Can be a pathway for extracranial infection, leading to infected thrombosis

Question: The dorsal horn of the spinal cord is supplied by what artery? Radicular arteries accompany the spinal nerves and bifurcate to form a VENTRAL or ANTERIOR RADICULAR ARTERY and a DORSAL or POSTERIOR RADICULAR ARTERY to supply the ventral and dorsal never roots respectively.

Radiculospinal arteries connect with the anterior spinal artery to also supply the cord -‐SULCAL ARTERIES arise from the anterior spinal artery and courses in the ANTERIOR MEDIAN FISSURE to supply approximately 2/3 of the anterior cross-‐sectional area of the cord (Sulcal means central)

• Venous Supply o Parallels with arterial supply (venae comitantes) o Internal vertebral venous plexus (epidural venous plexus)

Between the dura mater and the vertebral periosteum Have connections thoracic, abdominal and intercostals veins and external venous plexus

Internal vertebral venous plexus = External vertebral venous plexus = Systemic venous system

o Because of these connections, infection or carcinoma from pelvic or abdominal organs may spread to the brain

Notes: There are usually 3 anterior and 3 posterior spinal veins.

They are arranged longitudinally, communicate with each other, and are drained by up to 12 anterior and posterior medullary and radicular veins. These veins join the INTERNAL VERTEBRAL (or EPIDURAL) VENOUS PLEXUS [point bottom], lying in the extradural or epidural space.

Fig. 17 Anterior and Posterior Blood Supply of the Spinal Cord

Fig. 18 Venous Drainage of the Spinal Cord Fig. 19 A and B Spinal Cord Cross Section (Thoracic – Note lateral horn of Grey Matter)

B


As mentioned earlier, this INTERNAL VERTEBRAL VENOUS PLEXUS passes superiorly through the foramen magnum to communicate with the dural sinuses and basilar venous plexus in the skull.

The INTERNAL VERTEBRAL VENOUS PLEXUS also communicates with the EXTERNAL VERTEBRAL VENOUS PLEXUS on the external surface of the vertebrae and thus connect directly to the systemic venous system. These connections may act as a route for spread of infection or carcinoma from the pelvic or abdominal organs to the brain.

The anterior spinal artery forms a circumferential plexus with the posterior spinal arteries called the VASOCORONA . The anterior spinal artery supplies the anterior 2/3 of the cord including the base of the posterior horn [point], while each posterior spinal artery supplies the ipsilateral posterior horn and dorsal columns

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Anat 6.2 Blood Supply of CNS_zulueta