Cerebral Blood Flow

1
Cerebral Blood Flow Stroke

• Lecture 27

2
Cerebral Circulation

• Blood flow to CNS
• delivers O2, glucose, nutrients
• removes C O2, lactic acid, metabolites
• Cerebral vasculature
• unique anatomy physiology
• safety mechanisms
• Brain highly vulnerable to disrupted blood flow

3
Stroke

• CVA cerebrovascular accident
• Failure of safety mechanisms
• 3 cause of death for U.S. adults
• 1 cause of chronic functional incapacity
• about 2 million adults

4
CVAs

• neurological symptoms and signs
• usually focal
• localized
• acute
• sudden onset
• result from diseases involving blood vessels.

5
Causes of CVAs

• cardiac disease
• trauma
• infection
• neoplasm (tumor)
• exogenous toxins
• arterio-venous malformations (AVMs)

6
Types of CVAs

• Occlusive CVA
• due to the closure of a blood vessel -
• usually due to atherosclerosis thrombosis.
• Hemorrhagic CVA
• due to bleeding from a blood vessel
• usually due to either hypertension or an
  aneurysm.

7
Stroke Ischemia

• Insufficiency of blood supply
• Glucose O2 deprivation, build-up of wastes
• NOT synonymous Anoxia
• O2 deprivation only
• Few seconds little or no damage
• 6-8 minutes ---gt Infarction
• neurons other cells die

8
Blood Supply of Brain

• Arises from aortic arch
• 2 common carotid arteries
• (extracranial)
• give rise to external internal carotid
• 2 vertebral arteries

9
anterior cerebral
middle cerebral
Posterior cerebral
basilar
internal carotid
vertebral
external carotid
aortic arch
10
Blood Supply Arterial Territories

• Internal carotid arteries
• supply each cerebral hemisphere
• branches
• anterior cerebral artery
• middle cerebral artery
• anterior choroidal artery

11
Anterior Cerebral Arteries

• Surface branches supply cortex and white
  matter of
• inferior frontal lobe
• medial surface of the frontal and parietal lobes
• anterior corpus callosum

12
Anterior Cerebral Arteries

• Penetrating branches supply
• deeper cerebrum
• diencephalon
• limbic structures
• head of caudate
• anterior limb of internal capsule

13
Middle Cerebral Arteries

• Surface branches supply
• cortex white matter of hemispheric convexity
• (all four lobes and insula).
• Penetrating branches
• deep white matter
• some diencephalic structures

14
Anterior Choroidal Arteries

• Supply
• anterior hippocampus
• posterior limb of the internal capsule

15
Vertebral Arteries

• Rise from subclavian artery
• Branches
• anterior spinal arteries
• posterior inferior cerebellar arteries.
• 2 vertebral arteries join at the junction of the
  pons and medulla
• form basilar artery
• basilar divides into 2 posterior cerebral
  arteries.

16
Posterior Cerebral Arteries

• Surface branches supply
• cortex and white matter of medial occipital lobes
• inferior temporal lobes
• posterior corpus callosum
• Penetrating branches supply
• parts of the thalamus
• parts of the midbrain

17
Cerebral Artery Areas
1. anterior cerebral 2. Middle cerebral 3.
Penetrating branches of middle cerebral 4.
anterior choroidal 5. Posterior cerebral
18
Anastomoses

• Interconnections between blood vessels
• overlapping blood supply
• safety mechanism
• retrograde filling
• e.g., circle of Willis
• Others between...
• opthalmic artery external carotid
• surface branches of anterior, middle, posterior

19
Functions of Cortical Areas
20
Frontal lobe

• Prefrontal lobes
• anterior to motor cortex
• weigh consequences of future action and plan
  accordingly (an executive function)
• performance of delayed responses
• Inferior frontal lobes
• emotional responding

21
Frontal lobe

• Precentral gyri
• control contalateral movement
• Broca's area (L. Hemi.)
• language production
• R. Hemi. may be more involved in music
  production.

22
Parietal lobe

• Postcentral gyrus
• Anterior parietal lobe
• primary somatosensory cortex (S1)
• Posterior parietal cortex (PPC)
• higher-order sensory areas
• convergence from other sensory systems
• left parietal lobe reading and writing
• right parietal lobe spatial information.

23
Temporal lobe

• Language object recognition
• memory
• L. Hemi. verbal information
• R. Hemi. nonverbal information
• Inferior temporal lobes
• higher-order visual perception

24
Temporal lobe

• Superior temporal gyrus
• primary auditory cortex (A1)
• Superior temporal lobe
• L. Hemi. language comprehension
• R. Hemi. music comprehension
• except trained musicians

25
Occipital Lobe

• Analysis of visual information.
• Primary visual cortex (V1)
• Visual association cortex
• color
• movement
• shape

26
Infarction in the territories of the cerebral
arteries
27
Middle cerebral artery

• Most common stroke syndrome.
• contralateral weakness
• face, arm, and hand more than legs
• contralateral sensory loss
• face, arm, and hand more than legs
• visual field cut
• damage to optic radiations

28
Middle Cerebral Artery

• Aphasia language disturbances
• more likely with L. Hemi. damage
• especially men
• Broca's production
• Wernicke's comprehension

29
Middle Cerebral Artery

• Impaired spatial perception
• more likely after R. Hemi. damage
• spatial neglect
• dressing apraxia
• constructional apraxia
• topographagnosia

30
Anterior cerebral artery

• Motor distrubance contralateral distal leg
• urinary incontinence
• speech disturbance (may be more of a motor
  problem)
• apraxia of left arm (sympathetic apraxia) if
  anterior corpus callosum is affected
• If bilateral may cause apathy, motor inertia, and
  muteness

31
Posterior Cerebral Artery

• Visual disturbances
• contralateral homonymous hemianopsia
• (central vision is often spared)
• L. Hemi lesions alexia
• (with or without agraphia)
• Bilateral lesions cortical blindness
• patients unaware they cannot see
• (Anton's syndrome)
• Memory impairment if temporal lobe is affected

32
Posterior Cerebral Artery

• Proximal occlusion
• contralateral hemisensory loss,
• spontaneous pain and dysesthesia if thalamus
  affected
• (thalamic pain syndrome)
• contralateral severe proximal chorea
• (hemiballism)

33
Treatment

• Pharmacologic
• anticoagulants
• vasodilators
• antihypertensives
• steroids
• antagonism of excitatory amino acid neurotoxicity
  

34
Treatment

• Surgery
• remove aneurysms
• remove pressure following hemorrhage
• Radiation to treat AVMs
• Embolization therapy to
• plug vessels of an AVM
• or to treat an aneurysm
• (direct surgery usually preferable)

35
Stroke Rescue?

• Cell transplant - experimental
• Inject immature nerve cells
• grown from human cancer cells
• Cells mature ---gt bridge damaged areas
• Rats function restored
• Human June 23, 1998
• no ill effects
• no recovery yet