Cerebral circulation by DR.ARSHAD

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Cerebral circulation by DR.ARSHAD

  1. 1. CEREBRAL CIRCULATION
  2. 2. FACTS ABOUT BLOOD SUPPLYOF BRAIN Brain – 2% of body weight Receives 17% of cardiac output Consumes 20% of entire Oxygen used by the body 10 seconds of interruption in blood flow leads to unconsciousness Most neurologic disorders are due to vascular lesions
  3. 3. ANTERIOR AND POSTERIORCIRCULATIONSAnterior – Internal carotid arteriesPosterior – Vertebral arteries
  4. 4. INTERNAL CAROTID ARTERYCourse Entry – carotid canal Middle cranial fossa- beside dorsum sellae Enters cavernous sinus Approaches medial side of anterior clinoid process
  5. 5.  Pierces dura and arachnoid maters Moves lateral to optic chiasma Divides into Anterior and Middle cerebral arteries
  6. 6. BRANCHES OF INTERNAL CAROTIDARTERY[PRIOR TO BIFURCATION]
  7. 7.  Occasionally, Anterior choroidal artery supplies2. Rostral midbrain3. Ventral thalamus4. Subthalamus
  8. 8. ARTERIAL‘CIRCLE’/’CIRCLE’ OFWILLIS
  9. 9. “CIRCLE” OF WILLIS Looks more like a polygon Connects anterior and posterior circulations
  10. 10. COMPONENTS From anterior2. Anterior communicating artery3. Anterior cerebral artery4. Posterior communicating artery5. Posterior cerebral artery
  11. 11.  Alternate route – inadequate, especially in the elderly [atherosclerosis] Variations3. In approximately 33% persons Posterior cerebral artery arises from Internal carotid artery4. One Anterior cerebral artery may be small- anterior communicating artery is wider
  12. 12. TERRITORIES OFCEREBRAL ARTERIES
  13. 13. ANTERIOR CEREBRAL ARTERY Midline proximity [longitudinal horizontal fissure] Joined together by anterior communicating arteryBranches4. Medial striate/recurrent artery of Heubner→ventral part of head of caudate nucleus, putamen, anterior limb and genu of internal capsule
  14. 14. AREA SUPPLIED Medial part of orbital surface of frontal lobe [includes olfactory bulb and tract] Medial surfaces of frontal and parietal lobes Corpus callosum A strip on lateral surface
  15. 15. FUNCTIONAL AREAS SUPPLIED Supplementary and cingulate motor areas Dorsal parts of primary motor and sensorimotor areas
  16. 16. OTHER ASSOCIATED DEFICITS INACA BLOCK Mental confusion and dysphasia[functional loss in prefrontal cortex, cingulate gyrus, supplementary motor area]
  17. 17. EFFECTS OF OCCLUSION Paralysis and sensory deficits in contralateral leg, perineum Urinary incontinence [inadequate perineal sensation, defective cortical control of pelvic floor muscles]If obstruction is proximal to anterior communicating artery [blocked medial striate artery] UMN weakness of face, tongue and upper limb [lesion in or near genu] Ipsilateral anosmia [maybe]
  18. 18. POSTERIOR CEREBRALARTERY
  19. 19. BRANCHES Central branches supply2. Midbrain3. Pineal gland4. Lateral geniculate body5. Lentiform nucleus [partly]6. Thalamus [partly]
  20. 20.  Temporal branches→ inferolateral and medial surfaces of temporal lobe, much of parahippocampal gyrus Calcarine and parieto-occipital branches→ peripheral strip on lateral surface Calcarine branch supplies all of primary visual cortex and some of Visual association cortex
  21. 21.  Posterior choroidal artery suppliesd Choroid plexus of inferior horn of lateral ventriclef Choroid plexus of 3rd ventriclef Thalamusf Fornixf Tectum of midbrain anastomoses with Anterior choroidal artery
  22. 22. EFFECTS OF OCCLUSION Blindness in contralateral visual fields of both eyes – homonymous hemianopia Disturbance of memory – transient In case of dominant hemisphere being affected, the infarct extends into corpus callosum→ disconnection of contralateral visual area from language area of dominant hemisphere→ alexia in addition to homonymous hemianopia
  23. 23. SPECIAL CIRCUMSTANCES Expanding space-occupying lesion in supratentorial compartment→ herniation of uncus and midbrain→ compression of one or both PCA→ necrosis of areas supplied [even after surgical correction of cause]→ cortical blindness+inability to form new memories Traumatic Intracranial hemorrhage can lead to the same consequences
  24. 24. MIDDLE CEREBRALARTERY
  25. 25.  Larger, more direct continuation of ICA Occupies lateral sulcus Central branches →Head of caudate nucleus,Putamen, Lateral pallidum, Internal capsule [anterior limb, genu, posterior limb], External capsule, Claustrum, Lateral hypothalamus
  26. 26. FUNCTIONAL AREAS SUPPLIED Most of primary motor and premotor areas Frontal eye field Primary somatosensory area Geniculocalcarine tract EXCEPT motor and sensory cortex for lower limb and perineum In most persons, left MCA supplies all cortical areas concerned with language [Wernicke’s,Broca’s]
  27. 27. EFFECTS OF OCCLUSION Contralateral paralysis of lower face, upper limb General somatosensory deficits in the same areas Astereognosis Hemianopia in contralateral visual fields of both eyes Global aphasia if dominant hemisphere involved Aprosodia if non-dominant hemisphere involved
  28. 28.  Cortical neglect, if right hemisphere involved Conjugate eye movements affected[ at rest, eyes turn towards the side of lesion] Hearing unaffected [bilateral representation] Obstruction to central branches- contralateral hemiplegia without aphasia

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