Stroke: Causes
Stroke is caused when the blood flow to the brain is severely restricted or when a blood vessel ruptures.
There are two types of stroke and their causes and treatment are summarised in the table below.
TYPE OF STROKE: Ischemic stroke
Occurrence
Most common type of stroke
Affects about 85% of stroke patients
Cause
Caused by a blocked blood vessel to, or within, the brain
In many cases this is caused by a build-up of fatty deposits narrowing the arteries and increasing their risk of becoming blocked by blood clots
Treatment
At present there is only one medicine that is widely recommended to treat ischemic stroke.
This medicine, a clot-dissolving agent, can only be administered by a doctor and must be given soon after stroke has occurred.
Apart from this medicine, there is an option of mechanical removal of the blood cloth, called mechanical thrombectomy. Mechanical thrombectomy is a promising new modality of interventional stroke treatment. The various devices differ with regard to where they apply force on the thrombus, taking a proximal approach such as aspiration devices or a distal approach such as basket-like devices.
TYPE OF STROKE: Hemorrhagic stroke
Occurrence
Less common type of stroke
Affects about 15% of stroke patients
Cause
Caused by a bleed from a ruptured blood vessel within the brain
In many cases this type of stroke is associated with high blood pressure
Treatment
Doctors may use a variety of medical and surgical techniques to treat this type of stroke
Use of a clot-dissolving agent can make a hemorrhagic stroke event worse
At present there is only one medicine that is widely recommended to treat ischemic stroke. This medicine may or may not be available in your country. The decision on whether it can be administered can only be made by a doctor.
Key facts about this medicine are:
- This medicine can be very effective in treating acute ischemic stroke
There are strict criteria for which stroke patients should be treated with this medicine
The current medicine can only be administered by a doctor:
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- soon after the acute ischemic stroke has occurred, and
- if a brain scan shows that the patient does not have hemorrhagic stroke.
(The medicine cannot be used in hemorrhagic stroke patients because it may make this type of stroke worse.)
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- Not every stroke patient should be treated with this medicine
- Often the administration criteria for this medicine are not met and, as a result, doctors are only able to administer it to small proportion of patients with acute ischemic stroke
The strict rules concerning the use of the medicine in ischemic stroke can limit the number of patients that doctors are able to treat with this medicine. The reasons why some patients with ischemic stroke cannot be given the medicine include:
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- many patients arrive at the hospital too late to qualify for treatment with this medicine
- not all hospitals have facilities for brain scanning and, therefore, cannot check for hemorrhagic stroke and so are unable to offer the possibility of treatment with this medicine
Reasons like these may reduce the opportunity of patients with ischemic stroke being treated with this medicine.
There is much interest in researching new treatments that doctors could use in more patients with ischemic stroke.
Currently there is only one medicine which is widely recommended for treatment of acute ischemic stroke. It can only be administered by a doctor and must be given soon after ischemic stroke has occurred. This treatment can be very effective but is not suitable for every stroke patient. Ongoing research is hoping to find new treatments that doctors could use in more stroke patients.
Several organisations, including pharmaceutical companies, are working with doctors and nurses to investigate new medicines and procedures for ischemic stroke (e.g. hypothermia, surgery to remove blood clots and neuroprotection).
Several of these are in the latter stages of development and some may be only available in specialist centres.
- By protecting brain cells from dying, neuroprotective stroke medicines may have the potential to reduce the degree of brain injury caused by ischemic stroke. In ischemic stroke, a blockage of the blood flow, to or within, the brain will deprive some brain cells of their nutrient and oxygen supply. In the area of reduced blood flow there is a central core of cells that are exposed to severe marked reduction in blood supply. These cells die very quickly (the area of dead brain cells is called the infarct). Brain cells surrounding the infarct are serviced by a diminished blood supply. Although they do not die immediately, they are at risk of being killed or harmed by damaging chemicals that are released during stroke. This area of cells, under the threat of destruction by stroke, is called the penumbra. Research suggests that neuroprotective medicines may have the capability to protect the brain cells within the penumbra from dying.
- The more brain cells that survive ischemic stroke, the more likely it is that patients will achieve their best possible recovery and best possible quality of life after the stroke.
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