An ischemic stroke is an interruption of the blood supply to any part of the brain. A stroke is sometimes called a ‘brain attack’. It occurs when a blood vessel that supplies blood to the brain is blocked by a blood clot. This may happen in two ways:
- Thrombotic stroke: A clot may form in an artery that is already very narrow. This is called a thrombus. If it completely blocks the artery, it causes a stroke.
- Embolic stroke: A clot may break off from another place in the blood vessels of the brain, or some other part of the body, and travel up to the brain to block a smaller artery. This is called an embolism.
Non-modifiable risk factors for stroke
- Family history: Risk of having a stroke is higher for people whose parents or siblings have had a stroke.
- Age: Stroke risk increases with age; doubling every 10 years after the age of 55.
- Gender: Before the age of 55 years, men are more likely than women to have strokes. Thereafter, the risk is the same for men and women.
- History of prior stroke, TIA or heart attack: Person who has had a stroke in the past is at much greater risk for suffering from another one. Risk of stroke after a TIA is greatest within the first 48 to 72 hours.
Modifiable risk factors for stroke
- High blood pressure: The most important modifiable risk factor for stroke. Controlling high blood pressure will greatly reduce risk of stroke.
- Cardiovascular disease: Congestive heart failure, a previous heart attack and atrial fibrillation can all raise the risk of stroke.
- Cigarette smoking: The risk of stroke is two to three times greater for smokers versus non-smokers.
- Carotid artery disease: Fatty deposits from atherosclerosis may cause significant narrowing in the carotid arteries. This can limit blood flow to the brain as well as acts as a potential source for cerebral emboli.
- Diabetes: Diabetes doubles stroke risk. Many people with diabetes also have high blood pressure, obesity and high cholesterol which increase their stroke risk even further.
- Undesirable blood cholesterol levels: High blood levels of low-density lipoprotein (LDL) cholesterol and low levels of high-density lipoprotein (HDL) cholesterol increase stroke risk.
- Obesity: Excess weight could double the risk of an ischemic stroke.
- Lack of exercise and physical activity: Doing some kind of activity for at least 30 minutes every day will help decrease stroke risk.
Common symptoms of ischemic stroke are
- Sudden weakness of a leg, arm or one side of the face
- Sudden trouble speaking or understanding speech
- Sudden vision problems, such as blurred or double vision
- Sudden loss of coordination or problems with balance
- Sudden numbness, weakness or dizziness
Treatment
Over 80 per cent of all strokes are ischemic and are commonly caused by blood clots that interrupt blood flow in an area of the brain. It is imperative for people with stroke symptoms to get to a hospital as quickly as possible. If the stroke is caused by a blood clot, a clot-busting drug (thrombolytic therapy) may be given to dissolve the clot. The drug breaks up blood clots and helps restore blood flow to the ischemic area. tPA acts by dissolving these stroke-causing blood clots. The efficacy of Intra-Venous Thrombolysis has been proven by several large clinical trials which show a greater chance of recovery in stroke patients who are treated with it. However, these trials also show that, if given later than three hours after stroke onset, tPA can cause dangerous bleeding in the brain. Hence, it is only safe to give tPA within three hours of the beginning of stroke symptoms, which is why we think of this time as the ‘golden three hour tPAwindow.’ Recently, the European Cooperative Acute Stroke Study (ECASS 3) study suggested that tPA was safe and effective up to 4.5 hours symptom onset for some patients.
| Remember F A S T rule |
 F – Face-ask the person to smile-Does one side of the face droop? |
 A – Arm- ask the person to raise both hands. Does one arm drift downwards? |
 S – Speech- ask the person to repeat a sentence. Is the speech slurred? |
 T – Time-If the person has any of these symptoms, send him to a stroke unit immediately. Call the hospital/consultant so they can activate the stroke protocol. |
Concept of ‘Golden Hour’
If flow through an artery supplying an area of the brain is stopped for some reason, other portions of the vasculature reperfuse the ischemic area. Contrary to popular belief, neurons do NOT die in few minutes, they, like other cells, can go an hour or more before death. However, they DO lose their function with a few minutes of ischemia. Ischemic neurons can regain function over time by either eliminating the cause of ischemic attack or collateral reperfusion will eventually make ischemic area smaller and smaller.
Time is equal to brain
- Every minute counts
- Permanent neurologic damage is more likely to occur the longer a stroke goes untreated.
- Rapid intervention is crucial in the treatment of stroke.
- For every minute a large vessel stroke goes untreated, as many as:
- 1.9 million neurons are lost
- 14 billion synapses are lost
- 7.5 miles of myelinated fibers are lost
The National Institutes of Health recommends time interval for tPA–eligible acute ischemic stroke patient presenting to the emergency department to receive treatment within 60 minutes.
0 min: Suspected acute ischemic stroke patient arrives at hospital
<10 min: Initial MD evaluation (including patient history, lab work initiation, and NIHSS assessment)
<15 min: Stroke team notified (including neurologic expertise)
<25 min: CT scan initiated
<45 min: CT and labs interpreted
<60 min: tPA given if patient is eligible
Before thrombolysis can begin, patients must undergo blood and radiological investigations, including a brain scan to ensure the stroke is ischemic and not haemorrhagic. These investigations also take time.
The golden window is often missed due to delays in treatment attributable to the patient and the medical system. Because of this only a small fraction of stroke patients receive tPA. The most common cause of delay is the lack of awareness about stroke signs and symptoms in the general public. Most people wait up to a day after their symptoms start before seeking medical attention because they simply don’t know their symptoms are those of a stroke.
Each of us can help get this message across by educating people before they are ever affected by a stroke. Teach the symptoms of stroke to your parents, your children, your patients and other people around you.
A stroke is a medical emergency. Immediate treatment can save lives and reduce disability.
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