CVA occurs when there is an interruption to cerebral brain flow. Blood is supplied to the brain through two major arteries the carotid arteries and the veterbral arteries. The carotid arteries branch to supply most of the frontal, parietal and temporal lobes, the basal ganglia and part of the dienecphalon. The vertebral arteries join to form the basilar artery which branches to supply the middle and lower part of the temporal lobes, the occipital lobes, cerebellum, brain stem, and diencephalon.

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Risk factors for stroke include modifiable and non modifiable factors. Non modifiable inculdes age, gender, race, and heredibility.  Risk factors increase with age, doubling each decade after 55. Modifiable factors include smoking status, obesity, hypertension, hyperlipidaemia, physical inactivity, and oral oestrogen contraceptives.

 

Here are the different parts of the brain can have the potential to be impaired by  stroke

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Here’s a video explaining it

CVA can be divided into three main categories:Transient ischaemic attack,  Ischaemic and Haemorrhagic 

Transient ischaemic stroke

This is a temporary loss of neurological function caused by microemboli that temporarily block blood flow, resulting in ischaemia. TIAs resolve without the need for medical intervention, usually within 24 hours of onset. Most resolve within three hours. TIAs are warning signs of progressive cerebrovascular disease. Depending on the vessels blocked sign and symptoms of TIA will differ. If the carotid system is involved there may be loss of vision, transient hemiparesis, numbness, or inability to speak. Signs of TIA in the vertebrobasilar may include tinnitus, vertigo, blurred vision, dysarthia, dysphagia, ataxia and weakness.

Ischaemic stroke

This results from inadequate blood flow to the brain from a partial or complete blockage of an artery and accounts for 85% of all strokes. This category can be further divided into thrombotic, embolic, and lacunar stroke.

Thrombotic:

Thrombotic stroke occurs due to damage caused to a blood vessel, resulting in a formation of a blood clot which blocks the artery.  This type of stroke is usually seen in older persons, especially those with high cholesterol levels and atherosclerosis, diabetes, or hypertension. The narrowing of the lumen associated with atherosclerosis causes thrombosis to readily develop. This is the most common type of stroke. In up to 50% of individuals thrombotic strokes are preceded by a TIA.

The extent of the stroke depends on rapidity of onset, the size of the lesion, and the presence of collateral circulation. Collateral circulation is the alternate circulation around a blocked artery or vein via nearby minor vessels. Branches formed between adjacent blood vessels. It may arise from pathological conditions such as congestion or ischaemia.

Most patients with an ischaemic stroke do not have a decreased level of consciousness within the first 24hrs. Ischaemic stroke symptoms may progress in the first 72 hours as infarction and cerebral oedema increase. Symptoms include:

  • Headache
  • Dizziness or confusion
  • Weakness or paralysis on one side of the body
  • Sudden, severe numbness in any part of the body
  • Visual disturbance, including sudden loss of vision
  • Difficulty walking, including staggering or veering
  • Coordination problems in the arms and hands
  • Slurred speech or inability to speak

Lacunar stroke

This refers to a stroke from an occlusion of a small penetrating artery  with the development of a cavity in the place of infarcted brain tissue. This commonly occurs in the basal ganglia, thalamus, internal capsule or pons. Although a large percentage of lacunar strokes are asymptomatic, they can cause considerable deficits. These include:

  • motor hemiplegia
  • sensory stroke
  • contralateral leg and face weakness
  • ataxia

Multiple small vessel infarcts may also result in a decrease in cognitive function.

Embolic stroke

Embolic stroke occurs when an embolus lodges in and occludes cerebral blood flow, resulting in infarction and oedema. Embolic stroke is the second most common cause of stroke.

The majority of embolism originate for the endocardial layer of the heart. Plaque breaks off from the heart and travels to to cerebral circulation. Heart conditions associated with emboli includes AF, MI, endocarditis and atrial septic defects. Less common causes are a fat embolism originating from a fracture femur..

TIA as a warning sign is not common with embolic stroke. The onset is usually sudden and the patient may report a headache but will usually remain conscious.The rapid onset does not allow the body time to form collateral circulation. The effect of lodged emboli is severe neurological deficits.

Haemorrhagic stroke

There are two types of stroke, hemorrhagic and ischemic. Hemorrhagic strokes are less common, in fact only 15 percent of all strokes are hemorrhagic, but they are responsible for about 40 percent of all stroke deaths.

A hemorrhagic stroke is either a brain aneurysm burst or a weakened blood vessel leak. Blood spills into or around the brain and creates swelling and pressure, damaging cells and tissue in the brain. There are two types of hemorrhagic stroke called intracerebal and subarachnoid.

Intracerebral haemorrhage

The most common hemorrhagic stroke happens when a blood vessel inside the brain bursts and leaks blood into surrounding brain tissue (intracerebal hemorrhage). The bleeding causes brain cells to die and the affected part of the brain stops working correctly. High blood pressure and aging blood vessels are the most common causes of this type of stroke.

Sometimes intracerebral hemorrhagic stroke can be caused by an arteriovenous malformation (AVM). AVM is a genetic condition of abnormal connection between arteries and veins and most often occurs in the brain or spine. If AVM occurs in the brain, vessels can break and bleed into the brain.  The cause of AVM is unclear but once diagnosed it can be treated successfully.

There is most often a sudden onset of symptoms, with progression over hours. These include:

  • neurological deficits
  • headache
  • nausea/vomiting
  • decreased level of consciousness
  • hypertension (in an attempt to maintain cerebral perfusion pressure)

A blood clot in the brain can lead to pressure on brain tissues which displaces tissue, decreasing cerebral blood flow, leading to ishaemia and and infarction.

Subarachnoid haemorrhage

This type of stroke involves bleeding in the area between the brain and the tissue covering the brain, known as the subarachnoid space. This type of stroke is most often caused by a burst aneurysm. Other causes include:

  • AVM
  • Bleeding disorders
  • Head injury
  • Blood thinners

The symptoms may include ‘the worst headache’, loss of consciousness, focal neurological deficits, nausea, vomiting, and seizures.

Cerebral vasospasm is a complication associated with subarach haemorrhage. it is most likely due to an interaction between  the metabolites of blood and the vascular smooth muscle. During the lysis of blood clots, metabolites are released which cause endothelial damage and vasoconstriction.

 

 

Complications of stroke

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Here’s a booklet about understanding stroke

And a video (this guy is painful to listen to but some good info) but here’s another one

And a quiz

 

 

References

Elliot, M., Laskowski-Jones, L., & Baker, J. (2008). Nursing management: Acute intracranial problems. In D. Brown & H. Edwards (Eds.), Lewis’s medical-surgical nursing: Assessment and management of clinical problems (2nd ed., pp. 1570–1603). Sydney, Australia: Mosby Elsevier.

Johnston, A. (2015). Structure and function of the neurological system. In J. Craft & C. Gordon (Eds.), Understanding pathophysiology (2nd ed., pp. 89–136). Sydney, Australia: Mosby Elsevier.

 

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