Pathophysiology of Different Types of Stroke - Essay Example

Stroke Number Department Introduction Stroke is defined as the loss of functioning of the brain because of the occurrence of disturbance/ interference that remain for periods beyond 24 hours or is interrupted by death within 24 hours of onset. The retardation of blood flow associated with stroke often results in a general inability to move one or more limbs, impairment of vision of one side of the visual field or inability to formulate or understand speech. Stroke is a very serious medical condition that requires urgent treatment because delays can escalate the extent of damages suffered by the patient to permanent brain damage or fatal levels (Barrett, 2013, 34). Types of Stroke and their Pathophysiology Stroke has been classified into two main categories where we have ischemic and hemorrhagic stroke. Ischemic stroke takes place when the supply of blood to some area of the brain is impeded causing malfunction of that part of the brain. Ischemic stroke can result from venous thrombosis, systemic hyperfusion (which refers to a general reduction in the supply of blood such as shock), embolism (impediment/ obstruction caused by an embolus) or thrombosis (obstruction of the flow of blood when blood clots). Cryptogenic stroke is a stroke of unknown origins and lacks clear explanation. Cryptogenic strokes make up a third of all ischemic strokes. Dependent on symptom extents, stroke episodes can be grouped as posterior circulation infarct (POCI), lacunar infarct (LACI), partial anterior circulation infarct (PACI) or total anterior circulation infarct (TACI). These four episode categories can give insight on the area of the brain that has been impacted, extent of stroke, the underlying cause and prognosis. Approximately 85% of strokes are of ischemic nature (Lindley, 2008, 102). Unlike ischemic stroke, hemorrhagic stroke, on the other hand, occur due to rapture of a vessel of blood or a vascular structure that is abnormal. Intracranial hemorrhage denotes the accumulation of blood in any part of the skull vault. Extra-axial hemorrhage is accumulation of blood inside the skull but outside the brain whereas intra-axial hemorrhage is blood inside the brain (caused by intra-ventricular hemorrhage or intra-parenchymal hemorrhage). Subarachnoid hemorrhage (bleeding between the pia mater and the arachnoid mater), subdural hematoma (bleeding in the subdural space) and epidural hematoma (bleeding between the skull and the dura mater) are the commonest kind of extra-axial hemorrhage. Most forms of hemorrhagic stroke posses specific symptoms. Some hemorrhages take place within regions of ischemia in a condition called the hemorrhagic transformation. It is not yet known how many hemorrhagic strokes actually begin as ischemic strokes (Barrett, 2013, 45). Ischemic stroke take place due to loss of supply of blood to the brain leading to ischemic cascade whereby tissues of the brain stop functioning when oxygen deprived for over 60-90 seconds. After about three hours the brain suffers permanent damage causing tissue death/ infarction. As oxygen and glucose become depleted in the brain, production of high energy phosphate compounds such as ATP is halted causing failure of numerous energy dependent processes that usually ensure cell survival, leading to events that cause cell death and injury. The release of excitatory neurotransmitter glutamate at such times is a major cause of neuronal injury alongside production of oxygen free radicals and other damaging reactive oxygen species. In hemorrhagic stroke, blood accumulation causes tissue compression which distorts and damages tissues. The pressure can also cause loss of blood supply to affected tissue and the blood produced from hemorrhage can be toxic to the brain tissues and associated blood vessels. Inflammation that ensues also considerably damages tissues of the brain (Caplan, 2006, 345). Risk Factors Perhaps the most prominent risk factor for stroke is high blood pressure/ hypertension. Hypertension is responsible for 35-50% of stroke risk with the lowering of blood pressure indicated to considerably reduce incidences of both hemorrhagic and ischemic stroke. Anti-hypersensitive therapy benefits even patients older than 80 years with routine use of beta-blockers after stroke yielding quite impressive results. Another important risk factor for stroke is high cholesterol levels which have over time resulted in many cases of ischemic stroke. Lipid lowering drugs and statins (through mechanisms apart from lipid reduction) reduces the chances of experiencing stroke. High cholesterol causes blood vessel diseases which lead to stroke (Caplan, 2006, 365). Diabetes mellitus, another risk factor, twice or thrice increases the chances of getting stroke while proper regulation of blood sugar levels have been medically demonstrated to lower the risks of stroke. The fourth risk factor is heavy consumption of alcohol and drug abuse/ use. The use of alcohol could predispose stroke of ischemic nature alongside subarachnoid and inter-cerebral hemorrhage through several ways such hypertension, platelet aggregation, disturbances of clotting system, rebound thrombocytosis and atrial fibrillation. Drugs such as cocaine and amphetamines can cause stroke via acute hypertension or intracranial vasculopathy (Caplan, 2006, 400). Other risk factors of stroke include age. As one gets older, the risk of getting a stroke also increases. Gender also plays some role since stroke has been shown to be more prevalent in men than it is in women. Family history with stroke or even a previous encounter of stroke also serves to increase the chances of a person getting a stroke. Apart from atrial fibrillation and diabetes, other medical conditions that increase one’s chances of getting stroke include transient ischemic attack (TIA) and fibro-muscular dysplasia (FMD). Heart disorders and high concentrations of molecules (apolipoproteins) in the blood that are involved in the transportation of bad cholesterol is another factor of risk for stroke (Gillard, 2013, 377). Smoking (both active and passive) also increases one’s chances of getting a stroke or worsening one’s state by increasing blood pressure and lowering blood oxygen. Tobacco has a plethora of toxins which are deposited onto the lungs or absorbed in the blood which in the end cause complications of blood vessels and increase blood clotting in these vessels (such as those that take blood to the brain). Smoking equally causes blood to be sticky and therefore impedes its flow and makes clotting a common occurrence. In addition, obesity can increase the risk of stroke as too much body fat causes hypertension, heart diseases, and type II diabetes, and increases cholesterol levels. Poor nutrition and lack of exercise are other risk factors that promote obesity and thus hypertension, high blood cholesterol and so on. People who exercise frequently and eat healthy, fresh foods are less likely to suffer from stroke than those who eat recklessly and do not exercise. Unhealthy diets include excessive red meat consumption and intake of excess junk food and those with high fat and oil levels (Gillard, 2013, 411). In conclusion, risk factors of stroke are either controllable, that is, through medication or lifestyle changes, or are uncontrollable and cannot be changed. Most of the risk factors are controllable however and include hypertension, smoking, alcoholism, drug and substance abuse, atrial fibrillation, lack of exercise, poor diet, high blood cholesterol, obesity, diabetes mellitus, and so on, whereas, examples of uncontrollable predisposing factors include age, race, gender and family history (Gillard, 2013, 418). References Barrett, K., 2013, Stroke, Chichester, West Sussex: Wiley-Blackwell; 34, 45. Caplan, L., 2006, Stroke, New York: Demos; 345, 365, 400. Gillard, A., 2013, Stroke, Detroit: Greenhaven Press; 377, 411, 418. Lindley, R., 2008, Stroke, Oxford: Oxford University Press; 102. Read More