Strokes Essay, Research Paper
Strokes
Though the ultimate result of a stroke or intracranial accident is neurological damsage, the primary cause of this condition stemms from a catastrophy of vascular origin affecting intracranial blood flow. From a technical perspective, a stroke is defined by the World Health Orgaisation as rapidly developing clinical sighn of cerebral function, lasting more then 24 hours or leading to death, with no apparent cause other then of vascular origin. Without a supply of oxygen rich blood to the brain, perminant damage to the tissue occurs within 3-4 minuites (Bickerstaff 1987). Connsequently, the effects of a stroke may range from recovery to perminant damage to an area of the brain (infartion ) or may even result in death. Intracranial accidents are multifaceted diseases which concern many areas of the medical sciences; however, it is the clinical manifestations of the condition which include acute symptoms, diagnosis, treatment and prognosis which will be the main topic of the following discussion as they are problems which are frequently of interest in everyday practice.
Aetiology
At a general level, strokes are classified into two catagories namely ishemic and hemorrhagic strokes. In ishemic strokes, the blood supply to an area of the brain has been obstructed due to a clot in an intracranial blood vessle. The obstruction may be thrombolytic origin whereby an intractanial clot originated within a diseased vessle and increases in size until the vessle is totally occluded. Alternativly, a small ebolus originating from a source outside the brain, ie. coronary artery, may become lodged in the narrow intracranial vessles causing an obstruction. In both scenerios however, the result of an ishemic attack if sustained for a period longer then 3-4 minuites will be perminant damage to an area of the brain producing a loss of function. Of a less serious nature, when the brain is temorarily deprived of oxygen due to generalised narrowing of the intracranial vessles in conditions such as athlerosclerosis a transient ishemic attack will result. In this case no actual clot is present and function may be restored when the primary cause has been resolved. Furthermore many ishemic attacks (both obstructive and transient) will be asymptomatic because the blood supply at the base to the brain, namely the cerebral and vertebral arteries are cooncted at the brain stem by the Circle of Willis which is designed to provide the brain with collateral circulation. If for example an obstruction occurs in a vessle, circulation may be redirected through the circle of Willis to maintain circulation to all areas of the brain. If however stress upon the intracraial circulation cannot be maintained by collateral circulation in cases of vasospasm or extensive narrowing of blood vessles, then transient ischemic attacks will result in permanent damage to the brain tissue.
Hemmoragic strokes occur when a blood vessel within the brain ruptures and bllod is released into the cranial cavity. Besides an obvious lack of oxygen to area of the brain, the pooling of blood in the cavity causes the intracranial pressure to rise which ultimatly causes tissue death. In some circumstances such as aneurysms or angiomas on the brain surface, blood may drain into the subarachnoid cavity and is thus termed a subarachnoid hemmorrhage.
Clinical Manifestations
Superficially, an acute intracranial episode is easily recognised by the characteristic sudden onset of symptoms which quickly increase intensity; however, diagnosis of an ischemic attack as opposed to a haemorragic stroke is difficult without the use of clinical methods such as angeography and Cat scans. Clinical manifestaions of an ischemic stroke correlate with the effective blood vessels and the area of the brain in which they are located. In mostinstances the onset of symptoms occurs during periods of inactivity such as following a large meal, after a bath, or during the night. Dizziness , light-headedness, slurred speech, vision deficiencies, and a loss of sensation which abruptly develop. Paralysis at a point of the body related to the area of abstruction is often observered. A clot in the middle cerebral area will often produce paralysis on the opposite side of the body with many symptoms confined to the face and the arms. Loss of speech (aphasia) may also be observed. Ischemic strokes in the anterior cerebral region, though rare, will cause paralysis in the opposite leg. Obstructions in the posterior cerebral region are mainly associated with vision deficits. The most serious ischemic stroke, that which occurs in the basilar artery will often result in coma and death as the blood from this artery supplies the brain stem which is responsible for many of the life sustaining involuntary function such as heart rate and breathing. Paralysis of the swallowing muscles may also occur.
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