Essential Dental Therapeutics by David Wray

Essential Dental Therapeutics by David Wray

Author:David Wray
Language: eng
Format: epub
ISBN: 9781119057420
Publisher: John Wiley & Sons, Inc.
Published: 2017-06-24T00:00:00+00:00


Stroke

A stroke, or cerebrovascular accident, is associated with an interruption of the blood supply to a region of the brain that results in an infarction, or neuronal death, in the affected area. Normal cerebral perfusion can be interrupted in a number of different ways. The most common mechanism is a thrombotic event within a cerebral artery. Thrombotic strokes are frequently associated with the development of an atherosclerotic plaque in a cerebral artery. The plaque causes narrowing, and eventual occlusion of a vessel due to thrombus formation, particularly if the plaque ruptures. Strokes may also occur as a result of an embolism. Embolic strokes commonly involve blood clot, or thrombus, fragments that have formed outside of the brain, and travel to the brain through the circulation. Once in the cerebral circulation, they may occlude a cerebral vessel, commonly at a site of vessel bifurcation or narrowing. By their nature, the onset of embolic strokes is always very sudden and can involve very large regions of brain. Predisposing factors for embolic strokes include atrial fibrillation, bacterial endocarditis, and heart valve disease. Together, thrombotic and embolic strokes are referred to as ischaemic strokes, and account for more than 80% of all cerebrovascular accidents.

Other cerebrovascular accidents are associated with haemorrhage. Haemorrhagic strokes, also known as intracerebral haemorrhages, are most commonly caused by uncontrolled hypertension leading to weakening, and subsequent rupture of a blood vessel. Haemorrhagic strokes most commonly occur in deeper brain structures, particularly in the region of the basal ganglia.

A very severe headache is a consistent finding, while other symptoms depend upon the region affected. The release of blood from the ruptured vessel can cause further ischaemia in the brain, as a result of cerebral vasospasm.

A subarachnoid haemorrhage, where there is bleeding in the subarachnoid space of the meningeal membranes, can also cause a stroke. The rupture of a vessel is most commonly associated with the presence of an aneurysm, which weakens the vessel wall, although subarachnoid haemorrhages may also occur with head injuries. The risk of an aneurysm rupturing is exacerbated by uncontrolled hypertension.

The mechanisms associated with ischaemic strokes can also give rise to transient ischaemic attacks (TIAs). In some cases, the obstructing clot can be efficiently removed by the body's fibrinolytic system before any permanent tissue damage occurs. As a result, the early symptoms of the ‘stroke’ can resolve without evidence of neurologic dysfunction. However, these signs should not be ignored, since TIAs are an important warning sign of cerebrovascular disease, and sufferers carry a high risk of a subsequent stroke.

The signs and symptoms of a stroke will vary depending upon the vessel, and with that, the area of the brain affected. The initial signs of a stroke normally comprise a mixture of motor and sensory impairment. Motor impairment may result in weakness or clumsiness on one side of the body, along with difficulties in swallowing, slurred speech, and double vision. There may also be problems with language comprehension, balance and vision, as well as somatosensory loss.

It is important to be aware of the signs of a stroke, since early clinical intervention is critical.



Download



Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.