Hans S. Keirstead

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Hans S. Keirstead

• Reeve-Irvine Research Center
• College of Medicine
• 2111 Gillespie Neuroscience Research Center
• Phone [phone]
• E-mail hansk_at_uci.edu

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Vasculature, BBB and CSF

• Two fluid systems
• Vasculature
• Cerebrospinal fluid
• And the system that contains them
• Blood Brain Barrier

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Ischemia

• Interruption of the blood supply
• Neuronal cell bodies
• Tracts/nerves of the nervous system
• Deficit reflects regional supply of vasculature

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Arterial Supply of the Brain

• Derives from the paired carotid arteries and the
  vertebral arteries
• Internal carotid system
• Vertebrobasilar system
• These supply the entire brain, in regional blocks
  that are called arterial territories
• They communicate at the Circle of Willis
• Basic layout of medial supply and lateral supply
  throughout the axis of the nervous system

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Vertebrobasilar SystemVentral/Anterior spinal
artery

• Vertebral arteries ascend from spinal column,
  travel along ventromedial aspect of medulla, and
  give rise to anterior spinal arteries. These
  descend caudally and medially, and fuse into the
  centrally located ventral spinal artery.

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Vertebrobasilar SystemPosterior inferior
cerebellar artery (PICA)

• Vertebral arteries ascend from spinal column,
  travel along ventromedial aspect of medulla, and
  give rise to PICA. These constitute the last
  major branch of the vertebral arteries before
  they fuse at the basilar artery. PICA supplies
  the lateral aspect of the inferior cerebellum.

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Vertebrobasilar SystemAnterior inferior
cerebellar artery (AICA)

• The first major branch of the basilar artery is
  the AICA. It supplies the inferior portion of the
  cerebellum. Branches of the AICA form the
  internal auditory artery, which supplies the
  inner ear.

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Vertebrobasilar SystemSuperior cerebellar artery

• The second major branch of the basilar artery is
  the superior cerebellar artery. This demarcates
  the rostral end of the pons. This supplies the
  superior surface of the cerebellum. The
  occulomotor nerves lie immediately rostral to
  these vessels.

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Vertebrobasilar SystemSupply of the medulla

• Medial aspect of medulla supplied by paramedian
  branches of anterior spinal arteries
• Lateral aspect of medulla supplied by branches of
  the vertebral arteries

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Vertebrobasilar SystemSupply of the pons

• Medial aspect of pons supplied by pontine
  branches of basilar artery
• Lateral aspect of pons supplied by AICA, and more
  rostrally by the superior cerebellar artery

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Vertebrobasilar SystemPosterior cerebral artery

• Posterior cerebral arteries arise from the
  rostral terminus of the basilar artery. Supply
  most of the occipital pole. Thalamoperforating
  branches supply the mesencephalon and
  diencephalon medially.

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Internal Carotid System

• Enters the cranial vault at the carotid foramen.
  Principle branches are the middle cerebral (MCA)
  and anterior cerebral arteries. Smaller branches
  are the posterior communicating arteries. The
  anterior cerebral arteries, the anterior
  communicating arteries, and the posterior
  communicating arteries form the Circle of Willis

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Internal Carotid SystemAnterior cerebral artery

• Extend rostrally and medially, then arch along
  dorsally along medial wall of hemisphere.
  Proximal segment of the anterior cerebellar
  artery supplies the striatum and the
  hypothalamus.

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Internal Carotid SystemAnterior cerebral artery

• Main branch follows the corpus callosum. Two
  major branches, landmarks in cerebral
  angiography, are he pericallosal artery and the
  callosomarginal artery which travels along the
  dorsal boundary of the cingulate cortex. Supplies
  most of medial aspect of cerebral cortex rostral
  to parieto-occipital fissure. Stroke symptoms?

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Internal Carotid SystemMiddle cerebral artery

• Largest of the branches of the internal carotid
  artery. Extends laterally along the base of the
  hemisphere, and then branches to supply the
  entire lateral portion of the hemisphere.

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Internal Carotid SystemMiddle cerebral artery

• Because the MCA is the largest of the branch of
  the internal carotid artery, cerebral emboli
  (detached blood clots) often lodge here causing
  occlusive stroke. This leads to contralateral
  hemiplegia (motor cortex) and hemianesthesia
  (somatosensory cortex). MCA occlusion on left
  side may lead to global aphasia.

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Internal Carotid SystemMiddle cerebral artery

• Deep penetrating branches of MCA are called the
  striate or lenticulostriate arteries which supply
  the striatum, globus pallidus and internal
  capsule (sensory and descending motor paths).
  These arteries are a common site of cerebral
  hemorrhage.

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Venous Drainage

• Sinuses drain the capillary beds of the brain
• Inferior sagittal sinus lies dorsally along the
  midline of the hemispheres, draining to the
  transverse sinus and then to the sigmoid sinus,
  which empties into the internal jugular vein.
• The great cerebral vein of Galen drains the deep
  structures of the brain, emptying to the straight
  sinus, which leads to the confluence of the
  sinuses.
• The pituitary gland is surrounded by the
  cavernous sinus, which is drained by the superior
  and inferior petrosal sinuses, to the sigmoid
  sinus.

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Spinal Cord Circulation

• Arterial supply to the spinal cord originates
  from the vertebral arteries and the radicular
  arteries.
• Anterior spinal artery supplies medial cord via
  medial branches, and lateral cord via
  circumferential branches.
• Posterior spinal artery derives from the
  posterior cerebellar arteries, and fuse at low
  cervical levels. Supplies the dorsal aspect of
  the cord.
• Radicular arteries are major supply to cord,
  following peripheral nerves and splitting at
  dorsal and ventral roots
• Effect of spinal cord injuries?

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Stroke/Cerebrovascular Accident

• Occlusive (block) or hemorrhagic (bleeding)
• Symptoms are due to loss of supply to the
  arterial territory, and space-occupying lesion
  formed by extravasated blood
• Ischemia refers to insufficiency of blood supply
  leading to lack of oxygen, nutrients (glucose)
  and removal of toxins (anoxia is loss of oxygen
  supply only)
• Strokes are often preceded by transient ischemic
  attacks due to a temporary hypoperfusion, which
  is usually due to a temporary occlusion.
• Cerebral embolisms (blood clots) most often enter
  the MCA, and cause symptoms according to where
  they lodge. Occlusion in the stem of the MCA
  causes sensory (hemianesthesia) and motor
  (hemiplegia) and visual deficits (homonymous
  hemianopsia, both eyes on one side) on the
  contralateral side of the body, and language
  disorders (global aphasia) if the lesion is on
  the left side

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Arteriovenous (AV) Malformations

• Usually the development of shunts between
  arteries and veins, consisting of a tangle of
  vessels
• These shunts are often abnormally weak walled,
  and subject to rupture
• Ballooning of vessel wall is called a berry
  aneurysm, most often occurring in anterior
  portion of the Circle of Willis

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Cerebrovascular Physiology

• Extracellular signals regulate blood flow
  (potassium, adenosine and pH)
• Neural activity increases metabolic demand and
  leads to an increase in blood flow
• PCO2 increases, and aterioles dilate
• PCO2 decreases, and aterioles constrict (note
  error in text page 61)

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Blood-Brain Barrier

• Limited diffusion between blood and interstitial
  fluid of brain. Unique in the body, regulating
  neuro-immune interaction
• Molecules that do enter the brain do so via
  specific (carrier-mediated) transport mechanisms
• Some trafficking of lymphocytes, and drainage to
  cervical lymph nodes

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Blood-Brain Barrier

• Formed by capillary endothelial cells, between
  which are tight junctions (this is unique to
  brain vasculature, as is their decreased
  endocytosis and transcellular transport of
  material)
• Nature of BBB dictates drug therapy. Example is
  L-dopa for Parkinsons disease
• BBB absent in neurosecretory and chemoreceptive
  regions, such as the pituitary and pineal gland.
  These areas are isolated by specialized
  astrocytes called tanycytes

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Cerebrospinal Fluid System

• CSF produced in the choroid plexus in the
  ventricles, flows through the ventricles,
  entering the subarachnoid space at the foramen of
  Magendie and foramina of Luschka
• Magendie-medial, Luschka-lateral
• CSF is resorbed at arachnoid granulations, which
  extend into the dural sinuses, especially
  prominent in the superior sagittal sinus
• Ionic composition similar to blood, but protein
  concentration relatively low. Disturbances
  indicative of pathology

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Cerebrospinal Fluid SystemHydrocephalus
Non-communicating (obstructive)
Communicating
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Cerebrospinal Fluid SystemHydrocephalus

• Often occurs as a result of developmental
  abnormalities, or a tumor in later life
• If a developmental defect, cranium enlarges
• If a tumor, cranium can not enlarge, so
  ventricles expand and compress brain tissue
• Normal pressure hydrocephalus enlargement of the
  ventricles with compression of the brain, without
  an increase in intracranial pressure
• Effects of a fixed casing pressure in one place
  can cause a shifting of tissue if pressure
  released elsewhere