CNS

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CNS Blood Supply
Nabeel Kouka, MD, DO, MBA www.brain101.info
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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
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5. Adamkiwicz artery
anterior spinal artery segmental arteries
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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 its blood from two pairs of
arteries, the carotid and vertebral. About 80 of
the brains blood supply comes from the carotid,
and the remaining 20 from the vertebral.
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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.
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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
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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
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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.
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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.
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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 its
branches. These branches head for the pons,
medulla and cerebellum
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Spinal Cord Blood Supply
Ventral
Dorsal
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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.
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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
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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
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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.
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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
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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.
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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
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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
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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
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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
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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
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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
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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
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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
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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.
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Blood Supply to the Medulla
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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
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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
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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
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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
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Blood Supply to the Medulla
Occlusion of the posterior inferior cerebellar
artery (or contributing vertebral) will produce a
lateral medullary syndrome or Wallenbergs
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. Hornors syndrome,
(miosis contraction of the pupil, ptosis
sinking of the eyelid, decreased sweating), due
to damage to the descending hypothalamolspinal
tract
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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
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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
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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
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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
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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
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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, periaquaducta
l gray areas
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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)
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Blood Supply to the Pons
The short circumferential branches
supply, pontine nuclei, pontocerebellar fibers,
medial leminiscus the anterolateral system
(spinothalamic fibers)
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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.
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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)
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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
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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
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Blood Supply to the Midbrain
Occlusion of midbrain paramedian branches
produces a medial midbrain or superior
alternating hemiplegia (or Webers
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
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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
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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.
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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
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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