What is Acute Ischemic Stroke?
Strokes are of two types: Ischemic Stroke and Hemorrhagic Stroke. In case of acute ischemic stroke, atherosclerosis or blood clot obstructs a blood vessel resulting in diminished blood supply to the part of the brain where that vessel was serving. If the blood clot travels to the brain from another artery, then it can result in artery-to-artery embolization. If the clot comes from the heart, then it may result in a cardioembolic stroke.
Causes and Risk Factors of Acute Ischemic Stroke
A blockage or obstruction anywhere in the arteries which supply the brain can cause an acute ischemic stroke. The causes for these blockages leading to acute ischemic stroke are:
- Accumulation of fatty material, known as atheroma, in the artery walls causing diminished blood flow.
- If the atheroma breaks off into a small piece, then it may travel with the blood and become lodged in a smaller artery resulting in a blockage.
- If a part of the blood clot breaks loose from the heart or the valves then it is called as embolus. This embolus travels via the arteries to the brain and gets embedded there resulting in an embolic stroke or cerebral embolism. This is one of the most common types of stroke occurring in individuals with recent heart surgery and with defective heart valves or abnormal heart rhythms, particularly atrial fibrillation.
- Inflammation/infection cause narrowing of the blood vessels which supply the brain and result in decreased blood flow and acute ischemic stroke.
- Certain drugs, such as cocaine and amphetamines, also cause narrowing of the blood vessels which can lead to acute ischemic stroke.
- A rapid drop in blood pressure commonly causes the individual to faint, but if the drop in the blood pressure is prolonged and is critical, then it may cause a stroke. This severe, prolonged and abrupt drop in the blood pressure can occur if there is severe blood loss due to an injury or during a surgery or if that person has a heart attack or suffers from an abnormal heart rate/rhythm.
- Strokes can cause swelling in the brain and this pressure from the swelling causes more damage to the brain tissue and results in additional worsening of the neurologic problems.
Signs and Symptoms of Acute Ischemic Stroke
Majority of the acute ischemic strokes occur rapidly and unexpectedly and they advance quickly damaging the brain within just minutes. Sometimes, an ischemic stroke can continue to get worse over the next several hours or may continue to get worse till the next day or two. This occurs due to a gradually increasing area of the brain dying. This is known as stroke in evolution and it happens very rarely. When this happens, the stroke may have periodic stable episodes in between when the area temporarily ceases to get bigger or due to some other improvement.
Some Common Symptoms of Acute Ischemic Stroke Include:
- Abnormal sensations or loss of sensation in one arm, leg or one side of the body.
- Weakness or paralysis of an arm or leg on one side of the body.
- Partial loss of hearing or partial loss of vision.
- Impaired or double vision.
- Lightheadedness or dizziness.
- Incoherent or slurred speech.
- Problems in word finding.
- Other cognitive problems such as not being able to think clearly.
- Not being able to recognize body parts.
- Loss of coordination, problems in balancing and falling.
Treatment for Acute Ischemic Stroke
Treatment of acute ischemic stroke depends on the underlying cause. Diagnostic testing also depends on the cause of the acute ischemic stroke and differs from patient to patient. For e.g. some patients may require an echocardiogram, duplex scan and other sophisticated blood tests to find out the cause for the formation of the blood clots, whereas some don't require that many diagnostic tests. The outcome of a stroke depends on the severity of the ischemic stroke and the part of the brain which was affected. Most of the people who have had a acute ischemic stroke are able to regain their complete or most of their functional capacity. Whereas some may not be able to speak, eat or move normally.
- In the course of the initial few days following acute ischemic stroke, doctors usually won't be able to foretell whether a patient will improve or worsen. About 50% of the acute ischemic stroke patients having one-sided paralysis and patients with less severe symptoms will be able to regain some of their function before leaving the hospital and they are eventually able to take care of their basic needs. Around 20% of the patients suffering from a ischemic stroke die in the hospital and this proportion increases in the elderly patients. Acute Ischemic Strokes which result in loss of consciousness or impaired breathing or heart function are very serious and require immediate medical attention.
- If the acute ischemic stroke patient experiences problems in functioning even after six months, then these problems are likely to be permanent; however, some patients may improve gradually over a period of time. Younger patients, with overall better health, have more chances of recovering completely and quickly following acute ischemic stroke.
- Patient having a stroke requires prompt medical attention. Getting immediate medical attention helps in reducing the damage from the stroke or in preventing further damage. Most of the times, patient may require oxygen or an intravenous line to provide fluids and nourishment.
- In case of stroke in evolution, anticoagulants such as heparin can be given.
- Anticoagulants are ineffective in case of complete stroke.
- If a blood clot is the cause of the acute ischemic stroke, then clot-dissolving drugs, such as streptokinase or tissue plasminogen activator if given within 3 hours, help in preventing or reversing stroke symptoms such as paralysis. The patient should be examined by a doctor immediately to rule out hemorrhage, as it cannot be treated with clot-dissolving drugs.
- If the acute ischemic stroke is complete, then there will be some dead brain tissue whose function can never be restored. However, if the blockages are removed after a small stroke or transient ischemic attack in a patient with more than 70% carotid artery blockage, then it can reduce the chances of future strokes.
- Mannitol and rarely corticosteroids can be given in acute strokes where there is swelling and increased pressure on the brain due to the swelling. If the patient has suffered from an acute ischemic stroke, then that patient may be put on a respirator to maintain adequate breathing or because of pneumonia.
- Even though the dead brain tissue cannot be restored, patient can undergo intensive rehabilitation to help them in overcoming their disability by training other parts of the brain to do those tasks which were originally done by the dead or damaged part of the brain. Acute ischemic stroke patient should enroll in a rehab program immediately in order to keep his/her muscles strong and to prevent pressure sores and muscular contractions. Joining a rehab program immediately helps the patient to walk and talk again. Patient may continue rehabilitation even after leaving the hospital.
Tests to Diagnose Acute Ischemic Stroke
- Detailed medical history and physical examination.
- CT scan.
- MRI scan.
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