The 2 major mechanisms that cause it to occur are an obstructive blood clot or burst blood vessel
Monday, October 20, 2008
By DAVID DONALDSON
Staten Island Advance
STATEN ISLAND, N.Y. -- In last weeks Advance, I discussed the risk factors and presenting symptoms of a stroke. This article will focus on the mechanisms, diagnosis and treatment of a stroke.
A stroke is caused by a sudden interruption of blood supply to the brain. This interruption of blood starves the brain of oxygen and nutrients. The brain is highly sensitive to such changes and immediately begins to die and undergo irreversible brain damage with a stroke.
There are two major mechanisms of a stroke; either due to an obstructive blood clot (ischemic stroke) or burst blood vessel (hemorrhagic stroke). In an ischemic stroke, a blood clot forms on a ruptured atherosclerotic plaque or a blood clot formed from a distant site travels downstream to become lodged in the arteries of the brain.
In a hemorrhagic stroke, an artery bursts and releases blood into the brain, compressing the surrounding tissue and preventing downstream blood flow to the remaining portions of the brain.
The majority of strokes are ischemic in nature and are the result of progressive atherosclerosis, or fatty plaguing of blood vessels. Another common cause of an ischemic stroke is an irregular heart beat, called atrial fibrillation. In this condition, blood pools in the top chamber of the heart, allowing small blood clots to form that are subsequently released to the brain.
Less frequently, strokes are hemorrhagic, in which the blood vessels break and cause damage. The most common cause of hemorrhagic stroke is abnormal blood vessel formation, in which the vessels are weak and eventually rupture. Abnormal blood vessels are commonly due to ballooning of artery walls, forming aneurysms. A second cause is clustering of abnormally formed arteries and veins, forming AV malformations. Both aneurysms and AV malformations increase the risk of hemorrhagic strokes.
DIAGNOSIS OF STROKE
The diagnosis of a stroke or a TIA is usually made with close examination and history taking by a medical professional. In an emergency stroke hospital, a physician will perform a rapid history and focused neurological examination and then order some basic tests. These tests start with blood work, an EKG, and a head CT to determine whether the stroke appears to be hemorrhagic or embolic.
If indicated, a brain MRI is extremely useful to more accurately assess the brain tissue, and the blood vessels of the neck and brain. Also, ultrasound imaging of the blood vessels of the neck and base of the brain is quite useful. Lastly, the most accurate imaging of blood vessels is an invasive procedure called a cerebral angiogram, in which catheters are placed in the arteries of the brain to look for possible blockages.
The management of a stroke depends on whether the cause is hemorrhagic or embolic in nature. Regardless of the mechanism, time is critical in making the diagnosis of a stroke and initiating appropriate care.
For embolic strokes, the culprit is commonly a blood clot obstructing down stream blood flow. Therefore, the goal of therapy is to break up and dissolve the clot. This is done with blood thinners, and in cases when the time of onset of symptoms is close enough to the time of medical attention, patients can be treated with an injection of a potent clot buster called a thrombolytic.
Rarely, physicians are able to remove the blood clot during the cerebral angiogram, yet this is not usually attempted. Unfortunately, only a small fraction of all patients with embolic strokes reach medical attention in the allowed time window for administration of thromobolytics. The long-term care of embolic strokes is focused on minimizing the risk of future embolic strokes with the anti-platelet agents aspirin and Clopidogrel, or commonly with the anti-coagulant Coumadin.
The management of hemorrhagic strokes is completely the opposite. As bleeding is the problem, the goal of therapy is to stop the bleeding as quickly as possible and decompress the surrounding brain tissue. As AV malformations and aneurysms are the most common causes of hemorrhagic strokes, neurosurgeons can place a surgical clip at the base of the AVM and aneurysm and then drain the accumulating blood. A non-surgical technique employs catheters that are introduced into the blood vessels, allowing placement of a coil into the AV malformation or aneurysm, thus preventing expansion and reducing the risk of rupture.
A stroke is a lethal and commonly debilitating condition that is all too prevalent in the United States. As only medical professionals can initiate treatment for a stroke, it remains critical that Americans be mindful of the clues of a stroke and always remember to act "FAST."
Dr. Donaldson is a cardiologist at Massachusetts General Hospital. He is a former Staten Islander who recently moved to Boston. Dr. Donaldson's column appears on the first Monday of every month in the HEALTH section.
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And That's about it...I haven't sold any tubs , since my first.... but oh well... I will get a shot tomorrow.
I noticed that there were no new AVMs to report.... this is very good news.
I have been in bed all day.... I seems that I get headaches... today was a doozey! It is a side effect of my AVM.
So it looks like I have a new avm story... only I can't write... so know that I have bad ones to...
okay enuff of me... Goodnight.
R
