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  2. 4. ANATOMICAL REVIEW <ul><li>Vertebral artery </li></ul><ul><li>Arises from the proximal subclavian artery. </li></ul><ul><li>Ascends through the transverse foramina of the first cervical vertebra. </li></ul><ul><li>Passes posteriorly around the articular process of the atlas to enter the skull through the foramen magnum. </li></ul><ul><li>The two vertebral arteries join each other at the level of the pontomedullary junction to form the basilar artery. </li></ul><ul><li>The vertebral artery gives rise to anterior and posterior spinal arteries, the posterior inferior cerebellar artery and branches to the medulla </li></ul>
  3. 5. ANATOMICAL REVIEW <ul><li>Basilar artery </li></ul><ul><li>Formed by the two vertebral arteries joining each other in the midline. </li></ul><ul><li>Ascends along the ventral aspect of the pons. </li></ul><ul><li>Ends at the ponto-midbrain junction where it divides into two posterior cerebral arteries. </li></ul><ul><li>It gives rise to anterior inferior cerebellar artery, superior cerebellar artery and numerous paramedian, short and long circumferential penetrators. </li></ul><ul><li>The internal auditory (labyrinthine) artery arises from the basilar artery in about 20 % of the population whereas in the remainder it arises from the anterior inferior cerebellar artery. </li></ul>
  4. 6. ANATOMICAL REVIEW <ul><li>Posterior cerebral artery (PCA) </li></ul><ul><li>The basilar artery ends by dividing into the two posterior cerebral arteries. </li></ul><ul><li>They encircle the midbrain close to the occulomotor nerve at the level of tentorium cerebelli and supply the inferior part of the temporal lobe and the occipital lobe. </li></ul><ul><li>They anastomose with the posterior communicating arteries to complete the circle of Willis. </li></ul><ul><li>Many small perforating arteries arise from PCA to supply the midbrain, the thalamus, hypothalamus and geniculate bodies. </li></ul><ul><li>In fifteen per cent of the population, the PCA is a direct continuation of the PoCA, its main blood supply then comes from the ICA rather than from the vertebrobasilar system </li></ul>
  5. 7. PHYSIOLOGY OF BLOOD FLOW <ul><li>Brain uses approximately twenty percent of the body's blood and needs twenty-five percent of the body's oxygen supply to function optimally. </li></ul><ul><li>Blood flow in a healthy person is 54 milliliters per 1000 grams of brain weight per minute. </li></ul><ul><li>There are 740 milliliters of blood circulating in the brain every minute. 3.3 milliliters of oxygen are used per minute by every 1000 grams of brain tissue. </li></ul><ul><li>This means that approximately 46 milliliters of oxygen are used by the entire brain in one minute. </li></ul><ul><li>During sleep, blood flow to the brain is increased, but the rate of oxygen consumption remains the same. </li></ul>
  6. 9. Circle of Willis or Circulus Arteriosus <ul><li>The Circle of Willis or the Circulus Arteriosus is the main arterial anastomatic trunk of the brain. </li></ul><ul><li>The Circle of Willis is a point where the blood carried by the two internal carotids and the basilar system comes together and then is redistributed by the anterior, middle, and posterior cerebral arteries. </li></ul>
  7. 10. COMPANSATORY MECHANISM <ul><li>Anterior cerebral arteries of the two hemispheres are joined together by the anterior communicating artery. </li></ul><ul><li>Middle cerebral arteries are linked to the posterior cerebral arteries by the posterior communicating arteries. </li></ul><ul><li>So brain areas continue to receive adequate blood supply even when there is a blockage somewhere in an arterial system. </li></ul><ul><li>If there are no problems in either system, the pressure of the streams will be equal and they will not mix. </li></ul><ul><li>However, if there is a blockage in one of them blood will flow from the intact artery to the damaged one. </li></ul>
  8. 11. ANATOMICAL VARIATIONS <ul><li>As long as the Circle of Willis can maintain blood pressure at fifty percent of normal, no infarction or death of tissue will occur in an area where a blockage exists. </li></ul><ul><li>Sometimes, an adjustment time is required before collateral circulation can reach a level that supports normal functioning; the communicating arteries will enlarge as blood flow through them increases. In such cases, a transient ischemic attack may occur. </li></ul><ul><li>Some people lack one of the communicating arteries that form the Circle of Willis. Now if a blockage develops, collateral blood supply will be compromised, causing brain damage to occur. </li></ul><ul><li>There are some watershed areas in the brain located at the ends of the vascular systems. Blockages in the water shed areas can cause transcortical aphasia . </li></ul>
  9. 12. PATHOGENESIS <ul><li>LUMINAL OBSTRUCTION: </li></ul><ul><li>e.g. Thromboembolic disease. </li></ul><ul><li>VESSEL WALL DISEASE: </li></ul><ul><li>e.g. Athersclerosis, Fibromuscular dysplasia. </li></ul><ul><li>EXTRINISIC COMPRESSION: </li></ul><ul><li>e.g. Osteophytes, Muculofibrous compression. </li></ul>
  11. 15. DOPPLER & DUPLEX SCANNING <ul><li>By us in g Doppler ultrasound alone, vertebral artery orig in can only be imaged in up to 60% of subjects. </li></ul><ul><li>This can be improved to over 80% by in corporat in g the use of colour Doppler flow imag in g. </li></ul><ul><li>Improved accuracy in estimation of flow velocities, may achieved by tak in g read in gs from both low (C5-6) and high (C1-2) cervical regions. </li></ul>
  12. 16. Transcranial Doppler ultrasound <ul><li>To detect in tracranial vertebral artery stenosis with a sensitivity of as high as 80%, and a specificity of 80–97% when compared with DSA. </li></ul><ul><li>Detection of emboli from a stenosis. </li></ul><ul><li>Monitor in g dur in g percutaneous translum in al angioplasty (PTA) of vertebral stenosis. </li></ul>
  13. 17. Helical or spiral computerized tomography angiography (CTA) <ul><li>To image the extra cranial vertebral artery without the risks associated with catheter angiography. </li></ul><ul><li>Diagnostic benefit in differentiat in g between ‘k in ked’ and truly atherosclerotic stenosed vessels. </li></ul><ul><li>Diagnostic value is less in acute posterior circulation ischemic stroke. </li></ul>
  14. 18. Magnetic resonance imag in g <ul><li>Alone can detect in tracranial vertebral artery disease. </li></ul><ul><li>Best used in comb in ation with magnetic resonance angiography (MRA) to assess both extra and in tracranial vertebral arteries. </li></ul><ul><li>MRA has a higher sensitivity for detect in g basilar stenosis than either extracranial or in tracranial vertebral artery disease. </li></ul><ul><li>An important pitfall with MRA is an over-report in g of occlusion in cases of high-grade stenosis. </li></ul>
  15. 19. Digital Subtraction Angiography <ul><li>It is gold standard for diagnos in g vertebral artery stenosis. </li></ul><ul><li>Stenosis at the vertebral artery orig in can still be missed with standard arch views, because of superimposition of the subclavian artery over the first segment of the vertebral artery and additional oblique views are required. </li></ul>
  16. 20. Medical treatment <ul><li>Antiplatelet therapies or Anticoagulation. </li></ul><ul><li>Anticoagulation with warfar in to an IN R of 1.6–1.8 with aspir in 325 mg. </li></ul>
  17. 21. Surgical treatment <ul><li>Endarterectomy or Reconstruction. </li></ul><ul><li>Endarterectomy: via a supraclavicular in cision with or wothout clavicular osteotomy. </li></ul><ul><li>Complications in clude lymphoceles, fistulas, vocal cord paralysis and pneumothorax. </li></ul><ul><li>Endarterectomy of in tracranial vertebral artery stenosis in volves a limited suboccipital craniotomy. </li></ul>
  18. 22. Reconstruction for extracranial vertebral artery <ul><li>Transposition of the vertebral artery: </li></ul><ul><li>Common or in ternal carotid artery. </li></ul><ul><li>Subclavian Artery. </li></ul><ul><li>Thyrocervical trunk. </li></ul><ul><li>COMPLICATIONS: Horners’ syndrome </li></ul><ul><li>Lympholcele, Stroke & Death. </li></ul>
  19. 23. VERTEBERAL ARTERY SEGMENTS <ul><li>T hree extracranial parts & an in tracranial portion. </li></ul><ul><li>Part one is from the orig in to the po in t at which it enters the transverse foram in a of either the fifth or sixth cervical vertebra. </li></ul><ul><li>Second part courses with in the in ter vertebral foram in a. </li></ul><ul><li>Third part beh in d the atlas and head in g towards the foramen magnum. </li></ul><ul><li>The f in al in tracranial part beg in s as it pierces the dura and arachnoid mater at the base of the skull, and ends as it meets its opposite vertebral artery. </li></ul>
  20. 24. Endovascular treatment <ul><li>Endovascular in tervention, with percutaneous translum in al angioplasty (PTA) and stent in g, is a safe and effective treatment for extracranial vertebral artery atherosclerotic stenosis, especially at the vertebral artery orig in . </li></ul>
  21. 25. Endovascular treatment <ul><li>PTA alone performed for VA orig in stenosis were associated with a marked in cidence of restenosis. </li></ul><ul><li>Advantage of primary stent in g is a reduced rate of in timal dissection at the time of the procedure. </li></ul><ul><li>. In tracranial stent in g as reported seems to be a more technically difficult procedure. </li></ul><ul><li>Best treatment for in tracranial vertebral artery stenosis rema in s controversial because of uncerta in ty about benefits of PTA and the lack of acceptable surgical alternatives, while optimal anti-thrombotic management for in tracranial stenosis is also unclear. </li></ul>
  22. 26. SUBCLAVIAN STEAL SYNDROME <ul><li>It refers to subclavian artery steno-occlusive disease proximal to the origin of the vertebral artery and is associated with flow reversal in the vertebral artery. </li></ul><ul><li>Percutaneous transluminal angioplasty has a high rate of technical success. </li></ul><ul><li>Carotid-subclavian bypass (CSB) with either synthetic graft or saphenous vein graft can be performed. </li></ul>
  23. 27. <ul><li>Vertebral artery stenosis is an important aetiology of posterior circulation stroke. Improvements in non- in vasive imag in g are provid in g better anatomical in formation about vertebral artery occlusive disease. This should allow an improved understand in g of the natural history of this disease process in terms of its liability to cause disabl in g stroke and death. Until the natural history is clearer, it is difficult to evaluate specific medical treatments and in terventions fully, although endovascular in tervention with primary stent in g for extracranial vertebral artery stenosis is a promis in g potential treatment. </li></ul>Conclusion
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