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CNS Blood Supply. Nabeel Kouka, MD, DO, MBA www.brain101.info. Spinal Cord Vascular Supply. Arterial Supply - Spinal Arteries Anterior (1) & Posterior (2) Spinal Artery from Vertebral artery

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slide1

CNS

Blood Supply

Nabeel Kouka, MD, DO, MBA

www.brain101.info

slide2

Spinal Cord Vascular Supply

Arterial Supply

- Spinal Arteries

Anterior (1) & Posterior (2) Spinal Artery

from Vertebral artery

- Radicular Arteries ----- Segmental arteries

from Vertebral, Ascending Cervical, Intercostal and

Lumbar Artery

Venous Drainage

- Longitudinal & Radicular Veins

to Intervertebral veins ---- to Internal Vertebral Venous Plexus

to external vertebral venous plexus ---- to segmental veins

slide3

5. Adamkiwicz artery

anterior spinal artery segmental arteries

slide4

Blood Supply to the

Spinal Cord and Brain Stem

The brain is one of the most

metabolically active organs

in the body, receiving 17% of

the total cardiac output and

about 20% of the oxygen available

in the body.

The brain receives it’s blood from

two pairs of arteries, the carotid and

vertebral. About 80% of the brain’s

blood supply comes from the carotid,

and the remaining 20% from the vertebral.

slide5

The Vertebrobasilar System

The vertebral arteries originate from the subclavian artery,

and ascend through the transverse foramen of the upper six cervical vertebra. At the upper margin of the Axis (C2) it moves outward and upward to the transverse foramen of the Atlas (C1). It then moves backwards along the articular process of atlas into a deep groove, passes beneath the atlanto-occipital ligament and enters the

foramen magnum. The arteries then run forward and unite at the caudal border of the pons to form the basilar artery.

slide6

Blood Supply to the Spinal Cord

and Brainstem

The Spinal Cord receives its blood supply from two major sources;

1. Branches of the vertebral arteries, the major source of blood supply,

via the anterior spinal and posterior spinal arteries.

2. Multiple radicular arteries, derives sporadically from segmental

arteries

The Medulla, Pons and Midbrain areas receive their major sources of blood

supply from several important branches of the Basilar artery

slide7

Branches of the Vertebral Artery

1. Posterior Inferior Cerebellar Artery (PICA), the largest branch of the vertebral, arises at the caudal end of the medulla on each side.

Runs a course winding between the

medulla and cerebellum

Distribution:

a. posterior part of cerebellar hemisphere

b. inferior vermis

c. central nuclei of cerebellum

d. choroid plexus of 4th ventricle

e. medullary branches to dorsolateral medulla

slide8

Branches of the Vertebral Artery

2. Anterior Spinal Artery, formed from a Y-shaped union of a branch

from each vertebral artery.

Runs down the ventral median fissure the length of the cord.

Distribution:

a. supplies the ventral 2/3 of the spinal cord.

slide9

Branches of the Vertebral Artery

3. Posterior Spinal Arteries (2), originate from each vertebral artery

or Posterior Inferior Cerebellar on

each side of the Medulla.

Descends along the dorsolateral sulcus.

Distribution:

supplies the dorsal 1/3 of the cord

of each side.

slide10

Branches of the Vertebral Artery

4. Posterior meningeal, one or two branches that originate

from the vertebral opposite the foramen magnum. This branch

moves into the dura matter of the cranium

5. Bulbar branches, composed of several smaller arteries which

originate from the vertebral and it’s branches. These branches

head for the pons, medulla and cerebellum

slide12

Spinal Cord Blood Supply

Anterior Spinal Artery, provides sulcal branches which penetrate the ventral median fissure and supply the ventral 2/3 of the spinal cord.

Posterior Spinal Arteries, each descends along the dorsolateral surface of the spinal cord and supplies the dorsal 1/3.

slide13

Spinal Cord Blood Supply

Radicular arteries, originating from segmental arteries at

various levels, which divide into anterior and posterior radicular

arteries as they move along ventral and dorsal roots to reach the spinal cord. Here they reinforce spinal arteries and anastomose with their branches.

From these varied sources of blood supply, a series of circumferential anastomotic

channels are formed around the spinal cord, called the arterial vasocorona, from

which short branches penetrate and supply the lateral parts of the cord

slide14

Spinal Cord Blood Supply

The radicular arteries provide the main blood supply to the cord at the thorasic, lumbar and sacral segments. There are a greater number on the posterior (10-23) than anterior (6-10 only) side of the cord.

One radicular artery, noticeably larger than the others, is called the

artery of Adamkiewicz, or the artery of the lumbar enlargement. Usually

located with the lower thorasic or upper lumbar spinal segment on the left

side of the spinal cord

slide15

Spinal Cord Blood Supply

The spinal cord lacks adequate collateral supply in some areas, making

these regions prone to ischemia after vascular occlusions. The upper

Thorasic (T1-T4) and first lumbar segments are the most vulnerable regions

of the cord.

slide16

Spinal Cord Blood Supply

There are several arteries that reinforce the

spinal cord blood supply and are termed

segmental arteries

1. The Vertebral arteries, spinal branches

which are present in the upper cervical

(~C3-C5) levels

2. Ascending Cervical arteries, present in the

lower cervical areas

3. Posterior Intercostal, present in the

mid-thorasic region

4. First Lumbar arteries, present in the

mid-lumbar regions

slide17

Spinal Cord Blood Supply

The spinal veins arranged in an irregular pattern.

The anterior spinal veins run along the midline and the ventral roots. The posterior spinal veins run along the midline and the dorsal roots. These are drained by the anterior and posterior radicular veins. These in turn empty into an epidural venous plexus which connects into an external vertebral venous plexus, the vertebral, intercostal and lumbar veins.

slide18

Spinal Cord Blood Supply

Occlusion of the anterior spinal artery may lead to the anterior

cord syndrome, characterized by;

1. Loss of ipsilateral motor function, due to damage to ventral gray matter

and the ventral corticospinal tract.

2. Loss of contralateral pain and temperature sensation, due to damage to

the spinothalamic pathway

slide19

Spinal Cord Blood Supply

Occlusion of the posterior spinal arteries may lead to the rare

posterior cord syndrome, characterized by;

1. Ipsilateral motor deficits, due to damage to corticospinal tract

2. Ipsilateral loss of tactile discrimination, position sense, vibratory sense,

due to damage to the dorsal columns

slide20

Blood Supply to the Brain Stem

The brain stem (medulla, pons

midbrain) receives the bulk of its

blood supply from the

vertebrobasilar system. Except

for the labyrynthine branch,

all other branches supply the

brain stem and cerebellum

The posterior cerebral has only

a small contribution, its main

target being the posterior

cerebral hemispheres

slide21

Branches of the Basilar Artery

1. Anterior Inferior Cerebellar Arteries

(AICA), originates near the lower border

of the Pons just past the union of the

vertebral arteries.

Distribution:

a. supplies anterior inferior surface and

underlying white matter of cerebellum

b. contributes to supply of central

cerebellar nuclei

c. also contributes to upper medulla

and lower pontine areas

slide22

Branches of the Basilar Artery

2. Pontine arteries, numerous smaller

branches that can be subdivided into

Paramedian and Circumferential pontine

arteries. The Circumferential can be

further subdivided into Long and Short

pontine arteries.

Distribution:

a. paramedian pontine - basal pons

b. circumferential pontine - lateral pons

and middle cerebellar peduncle, floor

of fourth ventricle and pontine tegmentum

slide23

Branches of the Basilar Artery

3. Superior Cerebellar arteries, originates

near the end of the Basilar artery,

close to the Pons-Midbrain junction.

Runs along dorsal surface of cerebellum

Distribution:

a. cerebellar cortex, white matter and

central nuclei

b. Additional contribution to rostral

pontine tegmentum, superior cerebellar

peduncle and inferior colliculus

slide24

Branches of the Basilar Artery

4. Posterior cerebral arteries, the terminal

branches of the Basilar artery. They

appear as a bifurcation of the Basilar,

just past the Superior Cerebellar arteries

and the oculomotor nerve.

Curves around the midbrain and reaches

the medial surface of the cerebral

hemisphere beneath the splenium of the

corpus callosum

Distribution:

a. mainly neocortex and diencephalon

b. some contribution to interpeduncular

plexus

slide25

Branches of the Basilar Artery

5. Labyrynthine arteries, may branch

from the basilar, but variable in its

origin. Supplies the region of the inner

ear

slide26

Blood Supply to the Medulla

The Medulla is supplied by the;

1. Anterior spinal artery, sends blood to the paramedian region of the caudal medulla.

2. Posterior spinal artery, supplies rostral areas, including the gracile and cuneate fasiculi and nuclei, along with dorsal areas of the inferior cerebellar peduncle.

3. Vertebral artery, bulbar branches supply areas of both the caudal and rostral medulla.

4. Posterior inferior cerebellar artery, supplies lateral medullary areas.

slide28

Blood Supply to the Medulla

Occlusion of branches of the anterior spinal artery will produce

a inferior alternating hemiplegia (aka medial medullary syndrome),

characterized by;

1. A contralateral hemiplegia of the limbs, due to damage to the

pyramids or the corticospinal fibers

2. A contralateral loss of position sense, vibratory sense and

discriminative touch, due to damage to the medial leminiscus

3. An ipsilateral deviation and paralysis of the tongue, due to

damage to the hypoglossal nucleus or nerve

Occasionally, these symptoms will develop after occlusion of the

vertebral artery before gives off its branches to the anterior spinal

artery

slide30

Blood Supply to the Medulla

The posterior spinal arteries supply the

gracile and cuneate fasiculi and nuclei,

spinal trigeminal tract and nucleus,

portions of the

inferior cerebellar peduncle

slide31

Blood Supply to the Medulla

The vertebral arteries supply

the pyramids at the level of the Pons,

the inferior olive complex,

the medullary reticular formation,

solitary motor nucleus

dorsal motor nucleus of the Vagus

(cranial nerve X),

hypoglossal nucleus

(cranial nerve XII).

spinal trigeminal tract,

spinothalamic tract

spinocerebellar tract

slide32

Blood Supply to the Medulla

The posterior inferior cerebellar arteries (PICA) supply

spinothalamic tract,

spinal trigeminal nucleus and tract,

fibers from the nucleus ambiguous,

dorsal motor nucleus of the

Vagus (cranial nerve X)

inferior cerebellar peduncle

slide33

Blood Supply to the Medulla

Occlusion of the posterior inferior cerebellar artery (or contributing

vertebral) will produce a lateral medullary syndromeorWallenberg’s syndrome, characterized by;

1. A contralateral loss of pain and temperature sense, due to

damage to the anterolateral system (spinothalamic tract)

2. An ipsilateral loss of pain and temperature sense on the face, due

to damage to the spinal trigeminal nucleus and tract

3. Vertigo, nausea and vomiting, due to damage to the vestibular nuclei

4. Hornor’s syndrome, (miosis [contraction of the pupil],

ptosis [sinking of the eyelid], decreased sweating), due to

damage to the descending hypothalamolspinal tract

slide35

Blood Supply to the Pons

The Pons is supplied by the;

1. The Basilar artery, contributions of this main artery can be further

subdivided;

a. paramedian branches, to medial pontine region

b. short circumferential branches, supply anterolateral pons

c. long circumferential branches, run laterally over the anterior

surface of the Pons to anastomose with branches of the anterior inferior

cerebellar artery (AICA).

2. Some reinforcing contributions by the anterior inferior cerebellar and

superior cerebellar arteries

slide36

Blood Supply to the Pons

Additional branches of the

Basilar artery can be found

branching off within the

region of the Pons;

1. Anterior Inferior Cerebellar Arteries (AICA), originates near the lower border

of the Pons just past the union of the vertebral arteries.

Distribution:

a. supplies anterior inferior surface and underlying white matter of cerebellum

b. contributes to supply of central cerebellar nuclei

c. also contributes to upper medulla and lower pontine areas

slide37

Blood Supply to the Pons

2. Superior Cerebellar arteries, originates near the end of the Basilar artery, close to the

Pons-Midbrain junction.

Runs along dorsal surface of cerebellum

Distribution:

a. cerebellar cortex, white matter and central nuclei

b. Additional contribution to rostral pontine tegmentum, superior cerebellar peduncle and inferior colliculus

slide38

Blood Supply to the Pons

2. Labyrynthine arteries, may branch from the basilar, but variable in its origin. Supplies the region of the inner ear.

Divides into two branches;

a. anterior vestibular

b. common cochlear

The labyrinthine has a variable

origin, according to a study done

by Wende et. al., 1975, (sample

size of 238) the artery originated

from;

1. Basilar (16%)

2. AICA (45%)

3. Superior cerebellar (25%)

4. PICA (5%)

5. Remaining 9% were of duplicate origin

slide39

Blood Supply to the Pons

The paramedian branches of the Basilar artery supplies the paramedian

regions of the Pons, this includes corticospinal fibers (basis pedunculi),

the medial leminiscus, abducens nerve and nucleus (cranial nerve VI) ,

pontine reticular area, and periaquaductal gray areas

slide40

Blood Supply to the Pons

The paramedian branches of the Basilar artery supply

corticospinal fibers,

the medial leminiscus, abducens nerve and nucleus (cranial nerve VI) ,

pontine reticular area,

periaquaductal gray areas

slide41

Blood Supply to the Pons

Obstruction of the paramedian pontine arteries will produce a

middle alternating hemiplegia(also termed medial pontine syndrome)

which is characterized by;

1. Hemiplegia of the contralateral arm and leg, due to damage to the

corticospinal tracts

2. Contralateral loss of tactile discrimination, vibratory and position

sense, due to damage to the medial leminiscus

3. Ipsilateral lateral rectus muscle paralysis, due to damage to the

abducens nerve or tract (can cause diplopia “double vision”)

slide42

Blood Supply to the Pons

The short circumferential branches supply,

pontine nuclei,

pontocerebellar fibers,

medial leminiscus

the anterolateral system (spinothalamic fibers)

slide43

Blood Supply to the Pons

The long circumferential branches supply,

along with the anterior inferior cerebellar (caudally),

and superior cerebellar artery (rostrally).

middle and superior cerebellar peduncles,

vestibular and cochlear nerves and nuclei,

facial motor nucleus (cranial nerve VII)

trigeminal nucleus (cranial nerve V)

spinal trigeminal nucleus and tract (cranial nerve V),

hypothalamospinal fibers,

the anterolateral system (spinothalamic)

pontine reticular nuclei.

slide44

Blood Supply to the Pons

Occlusions of long branches circumferential branches of the basilar

artery produce a lateral pontine syndrome, characterized by;

1. Ataxia, due to damage to the cerebral peduncles (middle and superior)

2. Vertigo, nausea, nystagmus, deafness, tinitus, vomiting, due to

damage to vestibular and cochlear nuclei and nerves

3. Ipsilateral pain and temperature deficits from face, due to damage to

the spinal trigeminal nucleus and tract

4. Contralateral loss of pain and temperature sense from the body,

due to damage to the anterolateral system (spinothalamic)

5. Ipsilateral paralysis of facial muscles and masticatory muscles, due

to damage to the facial and trigeminal motor nuclei (cranial nerves

VII and V)

slide49

Blood Supply to the Midbrain

The major blood supply to the midbrain is derived from branches

of the basilar artery;

1. Posterior cerebral artery, forms a plexus with the posterior

communicating arteries in the interpeduncular fossa, branches from this

plexus supply a wide area if the midbrain

2. Superior cerebellar artery, supplies dorsal areas around the

central gray and inferior colliculus with support from branches of

the posterior cerebral artery.

3. Quadrigeminal, (some posterior choroidal) a branch of the posterior

cerebral, provides support for the tectum (superior and inferior colliculi)

4. Posterior communicating artery, derived from the internal carotid,

joins the posterior cerebral to form portions of the circle of Willis

(arterial circle). Contributes to the interpeduncular plexus

5. Branches of these arteries are best understood when grouped into

paramedian, short circumferential and long circumferential

slide50

Blood Supply to the Midbrain

The paramedian arteries, derived from the posterior communicating and

posterior cerebral, form a plexus in the interpeduncular fossa, enter the

through the posterior perforated substance, this system supplies

raphe region,

oculomotor complex,

medial longitudinal fasiculus,

red nucleus

substantia nigra

crus cerebri

slide51

Blood Supply to the Midbrain

Occlusion of midbrain paramedian branches produces a medial

midbrain or superior alternating hemiplegia (or Weber’s syndrome)

characterized by;

1. Contralateral hemiplegia of the limbs, and contralateral face

and tongue due to damage to the descending motor tracts

(crus cerebri).

2. Ipsilateral deficits in eye motor activity, caused by damage to the

oculomotor nerve

slide52

Blood Supply to the Midbrain

The short circumferential arteries originate from the interpeduncular

plexus and portions of the posterior cerebral and superior cerebellar

arteries, this system supplies

crus cerebri,

substantia nigra

midbrain tegmentum

slide53

Blood Supply to the Midbrain

The long circumferential branches originate mainly from the posterior

cerebral artery, one important branch, the quadrigeminal (collicular

artery) supplies the superior and inferior colliculi.

slide54

Blood Supply to the Midbrain

The posterior choroidal arteries

originate near the basilar

bifurcation into the posterior

cerebral arteries. In addition

to providing reinforement to

the midbrain short and long

circumferential arteries they

move forward to supply portions

of the diencephalon and the

choroid plexus of the third

and lateral ventricles

slide57

Other Clinical Points

Substantial infarcts within the Pons are generally rapidly fatal,

due to failure of central control of respiration

Infarcts within the ventral portion of the Pons can produce

paralysis of all movements except the eyes. Patient is conscious

but can communicate only with eyes. LOCKED-IN-SYNDROME