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Understanding the story behind stroke: What causes blood flow to the brain to be interrupted?
Stroke, also known as ischemic stroke, is a pathological process caused by ischemia of brain tissue, eventually leading to the development of necrotic areas in the brain. Stroke is the leading cause of disability and the second leading cause of death in middle- and high-income countries. This phenomenon is primarily caused by interruption of blood supply (ischemia) and restriction of oxygen supply (hypoxia). The most common occurrence is due to thrombotic obstruction, or embolic obstruction of major blood vessels, resulting in brain necrosis.
The ischemic response causes the brain to undergo a process of liquefaction necrosis, which may lead to severe functional impairment.
Category
There are several classification systems for brain necrosis, one of which is the Oxford Community Stroke Project (OCSP) classification, which relies heavily on initial symptoms. Depending on the extent of symptoms, stroke events are classified as total anterior circulation infarction (TACI), partial anterior circulation infarction (PACI), cerebellar infarction (LACI), or posterior circulation infarction (POCI). These four types of stroke can predict the extent of the stroke, the area of the brain affected, the underlying cause, and the prognosis.
Another TOAST classification classifies stroke based on clinical symptoms and follow-up examination results as: 1. Thrombus or embolism caused by atherosclerosis of large arteries; 2. Embolism from cardiac origin; 3. Small vessel occlusion; 4. Others Determine the cause; 5. Unknown cause (two possible causes, unable to determine the cause or incomplete inspection).
Identification of stroke
There are a variety of tests available for initial screening of patients with stroke symptoms. The results of these tests varied, but there was room for improvement. For example, the Cincinnati Front Hospital Stroke Assessment Scale (CPSS), used in emergency care, checks for facial droop, arm drift, and changes in speech patterns; another, the Face, Arm, Speech Test (FAST), checks for facial weakness, arm weakness and speech impairment. Emergency physicians can also use the ROSIER (Emergency Stroke Identification Test), which has a score ranging from -2 to +5 for each variable.
In recent years, a study has shown that artificial intelligence can assist in the diagnosis of cerebral infarction and improve patient outcomes in areas where there is a lack of stroke-trained doctors.
Symptoms
Ischemic stroke usually presents with problems with nerve, spinal cord, or brain function. Depending on the area of the brain where the stroke occurred, symptoms may appear within minutes or hours. Most strokes occur without warning. Some common symptoms include unilateral weakness, facial paralysis or numbness, vision problems, speech difficulties, walking and balance problems. Individuals with these symptoms may experience one or more symptoms at the time of stroke. If the patient loses consciousness, the patient may have had a stroke in multiple parts of the brain or in the brainstem.
Symptoms of brain necrosis can determine the affected brain area, which in turn affects treatment and prognosis.
Risk factors
The main risk factors for brain necrosis are roughly the same as atherosclerosis, including hypertension, diabetes, smoking, obesity and dyslipidemia. There are also many risk factors that cannot be controlled, such as age, family history of stroke, being African American and being male. After age 55, the risk of stroke doubles every decade. Additionally, the American Heart Association/American Stroke Association (AHA/ASA) recommends controlling these risk factors to prevent the occurrence of stroke.
Pathophysiology
Brain necrosis is due to the interruption of blood supply. This interruption needs to last for a long time to cause tissue death. Interruptions in blood supply can occur for many reasons, including: thrombosis (a locally formed blood clot that blocks a blood vessel), embolism (an obstruction caused by an embolus emanating from another part of the body), systemic ischemia (reduced blood supply, such as in shock), and cerebral venous sinuses thrombus.
In the case of complete blockage of a major cerebral blood supply vessel, there is usually still some blood flow through collateral vessels to supply downstream tissues, which gives the area a certain survival potential.
Diagnosis
Computed tomography (CT) and magnetic resonance imaging (MRI) can show damaged areas of the brain. CT scans can rule out hemorrhagic strokes, are available at a low cost and are available in almost all hospitals, while MRIs can help diagnose acute brain infarctions within six hours of the onset of symptoms. CT angiography of the head and neck can pinpoint the exact location of the embolism within six hours of symptom onset.
Treatment
In the past decade, thrombolytic drugs have been introduced in the treatment of stroke, similar to the treatment of myocardial infarction. The efficacy of intravenous rtPA encourages its administration to patients in stroke units and preferably within three hours of onset. If the brain infarction is caused by a blood clot in the artery that supplies blood to the brain, it will need to be treated with treatments that dissolve the blockage. If blood flow can be quickly restored to the brain, the death rate of brain cells can be reduced.
Rapid administration of rtPA reduces the likelihood of disability after three months.
The consequences of stroke are not just physical, but also psychological and social. Behind the rapid changes in people's lives, how many underlying health problems still need to be explored and solved?
