Lecture 7 - Current Treatments And Prevention Flashcards
What does a doctor need to consider before starting stroke treatment?
Could it be something else?
What type of stroke is it?
Need to check the severity of the stroke.
Can it be treated? If so, how? What is the best line of treatment?
Once they have managed to acute situation then they might look at why a stroke might have occurred.
What’s the underlying factor causing the stroke?
What are the steps for diagnosing a stroke?
Step 1 - medical professional will examine the patient.
- Ask about symptoms, how long they have been occurring, they will also take a medical history.
Step 2 - neurological exam.
- They will test for neurological functioning which helps the medical professional identify where in the brain the stroke has occurred.
- Will check speech, memory, comprehension, orientation etc., might also involve checking muscle weakness and numbness.
They may have to still do more tests to confirm it is a stroke.
How are CT scans used for stroke patients?
A CT scan takes lots of images of different sections of the brain from different angles and levels and puts them together to form an image.
A CT scan of a brain a few minutes after an ischaemic stroke would look pretty normal but after a day or 2 you will be able to see the difference.
There will be swelling in the brain due to the inflammation following the stroke - this will change the shape of the brain and reduce the ventricle size.
These scans aren’t helpful for diagnosing ischaemic strokes because it takes a whole to show but it is helpful in ruling out brain haemorrhages.
A CT scan of a haemorrage stroke will show blood leaking out of the cerebral circulation and shows up as a bright white region (easy to spot).
How are MRI scans used for stroke patients?
Not typically used for diagnosing stroke but might be used to assess the type and extent of brain injury.
They are less available and take longer so not ideal for diagnosis.
They look at anatomical and structural differences in the brain so you can look at arteries and veins.
You can detect changes in the brain within about half an hour of the stroke occurring.
You can see the areas of the brain where there is reduced blood flow or too much blood flow.
There is no exposure to radiation with an MRI which is good - there is exposure to radiation with CT scans.
What are the 2 different zones of injury in an ischaemic stroke?
The ischaemic core = zone closest to the artery that has been blocked off - the blood flow is less than 20% than normal. There is severe ischaemia in the core zone which causes the neurons and their supportive cells to die off.
The penumbra = the area that surrounds the core. This area is moderately ischaemic meaning the tissues won’t die right away as it can recite vie some collateral blood supply. Medication is most likely to be effective in this area and reintroducing blood flow to this area will rescue the neurons.
How does injury progress in an ischaemic stoke?
The core region gets larger over time if the blood supply is not reintroduced.
Time is crucial - they may not see any differences after minutes because the area is so small but it should get clearer as time goes on and it gets bigger.
There are challenges with the healthcare system meaning people aren’t getting treated as quickly as they should.
What is the cascade of injury in ischaemic strokes?
When blood flow is blocked off it instigates a chain of processes that contribute to brain injury.
First cells die off due to lack of oxygen (hypoxia).
This triggers the release of toxic substances that are secreted that go on to contribute to ischaemic injury.
Toxic substances in the body triggers inflammation which is part of your immune system response. Some elements are protective whilst others contribute to the damage.
Inflammation triggers swelling known as edema which develops with 24 hours of the stroke and lasts several days and can continue to cause damage.
This all then lead to apoptosis which is a type of cell death triggered by injury.
Research looking at therapeutic targets largely focuses on targeting these processes.
What is tissue plasminogen activator (TPA)?
A thrombolytic treatment.
It activates a compound that’s already naturally floating around in your blood (plasminogen). When it gets activated its converted to plasmin and this is the compound that breaks down the clot.
TPA is most effective when administered within 3-4 hours of the stroke occurring.
What are the limitations of TPA?
There is a limited time window - it is most effective within 4 hours of having the stroke so not everyone who presents with an ischaemic stroke will qualify for this treatment.
It can cause a bleed into the brain (risk of haemorrhage) because it reduces the bloods ability to clot.
Could interfere with other health issues or make things worse.
What surgical treatment is there for ischaemic strokes?
Surgery is not really considered the first line of treatment unless the patient isn’t responding to TPA. This type of surgery is known as thrombolectomy and only really suitable if the blood vessel is large - it is the removal of a clot.
There are a few variations: MERCI retriever and suction removal.
How does MERCI retriever work?
A surgeon will insert a little wire into the blocked artery and pushes the wire into the artery just past the clot. The wire is in a sheath and when the sheath gets retracted the wire starts to coil up and as the wire is retracted it catches onto the blood clot and the wire and the clot are removed.
How does suction removal work?
Works kind of like a vacuum.
The surgeon inserts a tube into the artery and a little wire is put through the tube and positioned so its right behind the clot. Then the tube starts to suck in and while its doing that the wire gets pushed back and forth to break the clot. The pieces of the clot will then get sucked into the tube.
What are the limitations of thrombolectomy?
It is a very technical procedure and only a number of doctors are trained to do this. This means the process is only accessible to some people depending on where they live.
How are ischaemic strokes treated?
May be given TPA when first get diagnosed if its within 4 hours of the stroke occurring.
May also be given surgical treatment such as MERCI retriever or suction removal.
How are haemorrhages treated?
There is nothing that can really be done straight after the stroke occurring as the goal is to stop the bleeding and manage the symptoms. They may be given antihypertensives to reduce the blood pressure as high blood pressure could lead to further problems like a seizure.
Surgery isn’t common after a haemorrhage as there are too many risks but in some classes surgery may be considered, particularly if a haemorrhage may have resulted from an aneurysm - could perform an aneurysm clipping or a coil embolisation.
