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Türkçe Cerebrovascular Diseases
Cerebrovascular diseases rank third among the most common causes of death in the United States, and are the leading causes of disabilities. Death and disabilities are the result of focal or ischemia causing common infarction or hemorrhages causing compressive mass lesion.
Ischemic Vascular Disease (Paralysis-Stroke)
Ischemia and consequent brain infarction can be seen in the distribution area of any cerebral blood vessel thus, any part of the cerebrum, brain stem or cerebellum can be affected. Ischemia and infarction are more common in the distribution of the carotid circulation since it provides the largest amount of blood supply to the brain. Ischemia can be caused by occlusion of the main arteries, reduced blood flow as a result of stenosis or temporary or permanent occlusion of smaller arterioles as a result of intravascular embolism.
The most common cause of stenosis or occlusion in the large blood vessels is atherosclerosis. This disease usually occurs at the extracranial neck segment of the internal carotid artery, however, it may also occur at the carotid siphon segment (the part within the cavernous sinus), in the distal internal carotid artery and even in the proximal middle cerebral artery.
Arterial embolism usually originates either from the ulcerous atherosclerotic plaque in the carotid bifurcation or from a chamber of the heart. Mural thrombus or atrial fibrillation developed after myocardial infarction is the embolism origin in the heart. Other risk factors for cerebral ischaemia are hypertension, diabetes, hypercholesterolemia, obesity, smoking and familial anamnesis.
Since there is no effective medication or surgical intervention for stroke, the goal of neurosurgery is to identify possible stroke patients and reduce the risk of cerebral ischemia. These high-risk patients are known with the anamnesis of transient ischemic attack (TIA) that is commonly seen in form of transient cerebral ischemia or amaurosis fugax. Transient cerebral ischemia in the carotid circulation usually consists of transient hemianesthesia, hemiparesis or aphasia. Amaurosis fugax is the transient visual loss of one eye. Ischemia in the vertebrobasilar system may cause transient diplopia, dizziness, dysarthria, dysphagia, loss of strength, numbness, visual loss and even memory loss (amnesia).
The duration of majority of ischaemic cases are measured in seconds and minutes and rarely takes longer than 30 minutes. If the neurological disorder regresses within 24 hours, the case is defined as a GIA. A reversible ischemic neurological disorder (RIND) is one that takes 24 hours-3 weeks. Ischemic disorders with longer duration are considered as completed paralysis. It has been determined in careful questionings of individual with completed paralysis that 60% of them had a previous TIA, the paralysis developed progressively step by step in 20% of them and only in 20% of them it suddenly came up.
Treatment
Stroke cases with current GIA or with slow progression are potential candidates for protective surgical intervention. Stroke-preventive surgical interventions aim to remove the embolism focus or increase the blood flow to the brain. Operations to be performed for these cases involve carotid endarterectomy and microvascular bypass. Potential candidates are usually examined by CT and MRI scans to evaluate the level of infarction in the brain and eliminate other possibilities such as tumour, subdural hematoma or subarachnoid hemorrhage. After then, they are examined by angiography that involves the examinations of the aortic arch, carotid, vertebral and cerebral blood vessels. The examination of the carotid circulation with non-invasive techniques can be used for screening due to their low risk although they provide less accurate information.
If there are symptoms such as ipsilateral cerebral ischemia or amaurosis fugax (visual loss) and advanced stenosis (usually more than 75%) or ulceration is visualized in angiography, it is the indication for carotid endarterectomy. The procedure includes the opening the involved part of the carotid artery and removal of atherosclerotic plaque. In experienced hands, the mortality rate due to carotid endarterectomy is 1%, and the neurological morbidity rate is 5%.
Totally occluded internal carotid artery or stenosis at the segments of the internal carotid or middle cerebral artery which can not be reached surgically, ipsilateral cerebral ischemia can be seen in a group of patients. Microvascular bypass techniques are recommended for patients with such poor collateral circulation. The most commonly used technique of these is the the anastomosis of superficial temporal artery and middle cerebral artery (STA-MCA).
