Transcript CNS Blood Supply

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
- 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
5. Adamkiwicz artery
anterior spinal artery
segmental arteries
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.
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.
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
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
Branches of the Vertebral Artery
2. Anterior Spinal Artery, formed from a Yshaped 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.
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.
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
Spinal Cord Blood Supply
Ventral
Dorsal
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.
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
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
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.
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
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.
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
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
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
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
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
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
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
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
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.
Blood Supply to the Medulla
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
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
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
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
Blood Supply to the Medulla
Occlusion of the posterior inferior cerebellar artery (or contributing
vertebral) will produce a lateral medullary syndrome or Wallenberg’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
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
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
Blood Supply to the Pons
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
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
Blood Supply to the Pons
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
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
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”)
Blood Supply to the Pons
The short circumferential branches supply,
pontine nuclei,
pontocerebellar fibers,
medial leminiscus
the anterolateral system (spinothalamic
fibers)
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.
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)
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
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
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
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
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.
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
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