THE PATHOPHYSIOLOGY OF HAEMORRHAGIC STROKE-BY LAW JIA JUIN

Hemorrhagic stroke is defined as the bleeding which happens inside the brain as a result of the rupture of brain’s blood vessels or a leaky arteriovenous malformation (AVM), leading to the sudden onset of neurological symptoms. ^[1]It is dangerous because it leads to the increase of pressure inside the brain, ultimately leading to permanent brain damage.^[1] The hemorrhage can be classified into two which are intra-axial hemorrhage (blood inside the brain) and extra-axial hemorrhage (blood inside the skull but outside the brain). ^[2]

In this portfolio I will be mainly discussing on the pathophysiology of hemorrhagic stroke .The pathophysiology of hemorrhagic stroke can be discussed from few aspects. For examples, atrial fibrillation, underlying ischemic stroke, high blood pressure, aneurysm, accumulation of protein called amyloid, and abnormal connection between arteries and veins.^[3][4]

Atrial fibrillation is a type of arrhythmia in which the upper chambers of the heart beat too fast that they do not allow enough blood to be pump into the lower ventricles.^[3] These lead to the stagnant of the blood in the lower chambers, promoting the blood clot formation. If this clot dislodged escape from the heart and been circulated to the brain, it is known as embolus. ^[3]This embolus will block the capillaries in the brain, leading to decrease blood supply to the brain tissues. The brain tissues then become die off and soften. ^[3]The necrosis of the brain cells lead to the sudden release of large amount of toxins and radicals. ^[3]These free radicals and toxins will damage the epithelium cells of capillaries of the brain, leading to breakage and bleeding. ^[3]The epithelium cells of capillaries will also die when these cells do not receive enough oxygen and nutrients supply, leading to hemorrhagic stroke.^[3] On the other hand ,the ischemic stroke will lead to the increase of glutamate released, when the glutamate level rises too high, excite-toxicity will be resulted leading to cells death and hemorrhage can be resulted.^[3]

The blood vessels in the brain can also be broken when the peripheral blood pressure is too high .^[4]The high blood pressure in the capillaries will push on the capillaries wall and bring to leakage and bleeding.^[4] The accumulation of protein called amyloids within the artery will further enhance the risk of bleeding. Some patients who are having congenital vessels problems, may have brain’s arteries connected directly to the veins without passing through capillaries.  ^[4]The thin wall of the veins will not be able to withstand the high pressure created by the blood flowing directly into them. ^[4]This will lead to the damage and bleeding from the veins in the brain. ^[4]

The blood leaked out will accumulate within the skull vault or brain.^[4] The blood accumulated in the brain will create a pressure in the brain, causing swelling.^[4] Besides that, the blood accumulated will start to harden and form a solid structure known as hematoma. ^[4]Both these hematoma and swelling will displace the brain tissues. ^[4]The hematoma will also press on the nerves cells, leading to the lost of certain brain function. This is how hemorrhagic stroke lead to coma and paralysis. ^[4]

As a conclusion I would like to say that the pathophysiology of hemorrhagic stroke involved all the mechanisms which lead to the weakening,breakage and damage of the brain capillaries, arteries and veins. And by knowing this pathophysiology, drugs and treatments targeted on these mechanisms of hemorrhagic stroke can be developed

References

1.      Hemorrhagic Stroke Pathophysiology.The Pathophysiology of stroke[internet].2007[updated on 2012.Cited on 2012 April 12 ].Available from http://usgovernmentbenefits.org/hd/index.php?t=hemorrhagic+stroke+pathophysiology

2.      Wikepedia group. Stroke.[internet].2010[updated on 2012.Cited on 2012 April 12 ].Available from http://en.wikipedia.org/wiki/Stroke#Hemorrhagic_2

3.      About.com. Atrila Fibrillation and Stroke.[internet].2010[updated on 2012.Cited on 2012 April 12 ].Available from

4.      Health Central. Hemorrhagic stroke.[internet].2011[updated on 2012.Cited on 2012 April 12 ].Available fromhttp://www.healthcentral.com/ency/408/000761.html