Cerebrovascular accident

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Cerebrovascular accident

STROKE(CVA)

A stroke occurs when the supply of blood and nutrients is disturbed in some way (McMurdo, 2009). The upshot of this is that the areas of the brain that do not receive blood or nutrients starve and can die (Kobayashi et al 2009). The most common type of stroke is the ischemic stroke which accounts for over 85% of stroke events (The National Stroke Association. 2009). This kind of stroke is categorized by a blood clot blocking one of the vessels that leads to the brain. Ischemic stroke can be divided into three types (Tomandl et al 2003). Transient ischemic stroke (TIA) (McMurdo, 2009). This is known as a mini stroke because the stroke and its symptoms only last for less than 24 hours. However, TIAs need to be treated very seriously as they indicate a high risk of a subsequent major stroke event. The second type of ischemic strokes are known as cerebral thrombosis. When fatty deposits in the blood vessels start to block up the flow through the blood vessel, there is a risk that a thrombus, a blood clot, will form. When this occurs in a blood vessel leading to the brain, it is defined as a cerebral thrombosis (McMurdo, 2009). Finally of ischemic strokes, there are cerebral embolisms. The only difference between cerebral embolisms and cerebral thrombosis, is that with the former, the blood clot is forms “outside” of the blood vessels supplying blood to the brain.  The second major category of stroke are hemorrhagic strokes (McMurdo, 2009).  These strokes are different because they are the result of blood vessels bursting and not blood clots.

The optimal function of the brain relies on the correct delivery of oxygen and nutrients to the brain (Kobayashi et al 2009). This is only possible through the operation of a dense network of blood vessels (Tomandl et al 2003). When blood flow is hinder in any one of these vessels in the brain, the results are grave. For example, occlusion of the vertebrae arteries can readily result in paralysis or blindness (Washington University. 2009).

Other blood vessels of the brain include the region known as the Circle of Willis. This part of the brain is a region where the carotid and the vertobrobasilar arteries meet forms a circle. The relevance is that if occlusion occurs in this area the distal smaller arteries may start to receive blood from other arteries. This is known as collateral circulation (Washington University. 2009).

Other arteries which are significant in stroke cases are the anterior cerebral artery, the middle cerebral artery, the posterior cerebral artery, and Lenticulostriate Arteries.

Role of imaging modalities in the diagnosis

The use of complicated imaging modalities such as computed tomography (CT) and magnetic resonance imaging (MRI) is essential in the evaluation of stroke especially due to the high rate of misdiagnosis for stroke (Azmon, Alibadi, and Holman. 1995). Having said this, there are at least seven sophisticated techniques which emergency departments utilize to understand stroke (Kobayashi et al 2009). These techniques are in alphabetical order (1) Cerebral angiography – this involves the injection of a substance known as a contrast agent into the carotid artery, then as the contrast medium moves around the target region, radiographs are taken , (2) Echocardiography – in a similar way to ultrasound, ultrasonic waves are directed through the chest wall, the information which is received is useful for recording the motion and position of the heart walls, (3) Contrast enhanced CT, (4) MRI, (5) Positron Emission tomography (PET), (6) SPECT and Xenon Contrast CT, and  (7) Ultrasound (Brunser et al 2009). More and more, brain perfusion imaging is being used in the evaluation of stroke. The basic principles of this technique are that it measures the amount of blood that a specific area of the brain is receiving. It does this by working together with the cerebral blood flow (CBF) measurement as well as the cerebral blood volume (CBV) (Phillips, 2001).

To assess the extent of damage, CT is used on the head of the suspected stroke victim in order to rule out intracranial hemorrhage, internal structural lesions, or tumors. These three incidents can mimic stroke.

As in the event of a genuine stroke, the results of the CT change with time, it is important that the health care team requests CT scans at different time periods. For example, in 60% of stroke victims, CT scans in the first two hours present as “normal.” However, later at 6 hours and 48 hours, decreased attenuation on the images is seen indicating stroke existence (Azmon, Alibadi, and Holman. 1995). Also, CT angiography is being increasingly used to understand stroke.

MRI has a number of advantages over CT for the early detection of stroke as it can locate abnormalities in vascular flow.  Also, MRI can be more sensitive than CT for the detection and pin pointing of acute cerebral infarcts. However, a combination of techniques is advised as standard MRI scans do miss as high as one in five acute

infarcts (Azmon, Alibadi, and Holman. 1995).

One of the most exciting developments related to MRI for the detection of stroke is Diffusion Weighed Imaging (DWI). The benefit of this technique is that it is able to rapidly identify the region of abnormality in blood flow, namely, the area where movement has ceased. However, this technique is still not the good standard technique applied in hospitals (Hacke et al. 2009) .

Treatment and prognosis

Doctors view the treatment of stroke in three stages. The first stage is the prevention of the ailment (Kobayashi et al 2009). Doctors, usually GPs deal with stroke by assessing the individual underlying risk factors (Tomandl et al 2003). There are a number of risk factors including hypertension and diabetes. Furthermore, there are a number of behaviors which are best avoided such as being obese, smoking, a lack of exercise and a poor diet (National Institute of Neurological disorders and stroke. 2009).

Once stroke has occurred there are two basic approaches. For ischemic stroke, physicians attempt to dissolve the blood clots as quickly as possible. And for hemorrhagic stroke, physicians try to evaluate the location of the bleeding and stop it.

Finally, treatment can occur post-stroke, and this is known as rehabilitation therapy. It is common for stroke sufferers to be prescribed with drug therapy to aid movement in the individual. The most common drugs to be prescribed are antithrombotics (National Institute of Neurological disorders and stroke. 2009).

What is the prognosis for this ailment? Complete paralysis of one side of the body known as hemiplegia is very common (Tomandl et al 2003). Also, less severe but still common is hemiparesis, which is the weakening of one side of the body. Stroke can lead the individual to suffer from a range of problems with the brain’s usual functions. Stroke sufferers often report having difficulties understanding speech. Memory retention becomes troublesome. Also, sufferers experience numbness, strange sensations in the hands and feet, and even pain in cold temperatures. Stroke victims are need to be weary of reoccurrence, which happens within five years for every one in four sufferers (National Institute of Neurological disorders and stroke. 2009).
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