Cerebral Blood Flow Stroke

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 ---> 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 ~

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

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 ---> bridge damaged areas Rats: function restored Human: June 23, 1998 no ill effects no recovery yet ~