Today I am going to present a powerpoint on Strokes, cerebrovascular accidents and Transient ischemic attacks. I decided to choose stroke as it is a disease that is very prevalent in the world today and a type that most people in the world have been or known someone affected by it.
The world Health organization define stroke as ‘Rapidly developed clinical signs of focal (or global) disturbance of cerebral function, lasting more than 24 hours or leading to death, with no apparent cause other than of vascular origin’.
CVA’s can be catergorised into two types, ischemic, defined as ’Decreased blood flow to brain tissues that prevents adequate delivery of oxygen, glucose and other nutrients leading to metabolic changes and possible cell death.’
And Haemorrhagic defined as 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 haemorrhagic stroke called intracerebral and subarachnoid.’ TIA’s which I will talk about later are similar to a stroke however defined as ’Brief episodes of neurological dysfunction resulting from focal cerebral ischemia not associated with permanent cerebral infarction.’
Ischemic Stroke Makes up 85% of all strokes and is the most common cause of stroke. Ischemic stroke can be caused by various types of dysfunctions, the most common is the narrowing of the arteries in the head or neck. When the vessels become too narrow or blocked, it can cause blood clots to form, due to collection of blood cells. If blood flow is not restored, only the cell tissue beyond the blockage will die, therefore damage to the brain is limited. The severity of the stroke is measured by what artery is involved, in turn, part of the brain is affected.
In a normal adult, CBF is 50 – 55 ml/100g/min. Reduced CBF means the brain receives inadequate glucose and oxygen delivery, triggering the Stroke process. Generally, pathophysiology of ischemic stroke can be said to be in two stages. At a CBF of approximately 14±2 ml/100 g/min, the electroencephalogram becomes isoelectric or evoked responses become abnormal, it’s a region of functionally impaired but structurally intact tissue, called ischemic penumbra and brain damage here is reversible; when CBF is reduced to approximately 6 ml/100 g/min, the brain damage becomes irreversible and results in brain infarction, which is called ischemic core. In this regard, salvaging of ischemic penumbra is the clinical target for acute stroke therapy.
The pathophysiology of stroke is extremely complex and involves numerous processes, including: energy failure, excitotoxicity, oxidative stress, disruption of the blood-brain barrier (BBB), inflammation, necrosis or apoptosis etc. I am going to focus on the excitotoxicity process aspect in depth.
Excitotoxicity is the process by which neurons and cell structures such as cytoskeleton, cell membrane and DNA are damaged and killed by enzymes. Phospholipases, endoclunucleases and proteases such as calpin all damage cells. These enzymes are activated due to the influx of Calcium ions (Ca2+). NMDA and Kalinic acid bind with NMDA and AMPA receptors, high levels of the excitatory neurotransmitter, glutamate is produced allowing high levels of Ca2+ to activate cell killing enzymes.
Glutamate is released at high concentrations in the penumbral cortex, particularly if blood flow is reduced for a long period, and the amount of glutamate released correlates with early neurological deterioration in patients with acute ischemic stroke. Glutamate concentrations greater than 200 mmol/l in plasma and greater than 8.2 mmol/l in CSF are associated with neurological deterioration in the acute phase of cerebral infarction.
Haemorrhagic CVAs, in contrast, are similar neurological incidents to Ischemic strokes in that they cause death to cell tissue in the brain, again due to a lack of blood supply however symptoms tend to worsen over time. In Haemorrhagic CVA’s, bleeding in the cranium occurs causing raised Intercranial Pressure (ICP) leading to herniation of the brain stem. There are two types of haemorrhagic stroke: Intracerebral (within the brain tissue, sometimes referred to as intracerebral) Haemorrhage: A blood vessel bursts leaking blood into the brain tissue Subarachnoid Hemorrhage: Occurs when a blood vessel bursts near the surface of the brain and blood pours into the area outside of the brain, between the brain and the skull.
In the past, TIAs were operationally defined as any focal cerebral ischemic event with symptoms lasting 24 hours. Recently, however, studies from many groups worldwide have demonstrated that this arbitrary time threshold was too broad because 30% to 50% of classically defined TIAs show brain injury on diffusion-weighted magnetic resonance (MR) imaging (MRI). This may also be referred to as a mini stroke. The symptoms of a TIA present similar to those of a stroke. A TIA typically lasts less than an hour, more often minutes. TIA can be considered as a serious warning for an impending ischemic stroke; the risk is highest in the first 48 hours following a transient ischemic attack. It was found one third of TIA patients suffer a stroke soon after. The most common cause of a TIA is carotid artery disease.
Risk factors for a stroke can be classified into modifiable and non-modifiable. This is referring to factors in and out of our control. Modifiable risk factors include,High blood pressure. The risk of a stroke begins to increase at blood pressure readings higher than 140/90 millimeters of mercury (mm Hg). Eating less cholesterol and fat, especially saturated fat and trans fat, may reduce the plaques in your arteries. Cholesterol controlling medication may be prescribed by your doctor if lifestyle changes are ineffective. Cardiovascular disease and Carotid artery disease as the blood vessels in your neck that lead to your brain become clogged. Peripheral artery disease (PAD) as blood vessels that carry blood to your arms and legs become clogged. Diabetes increases the severity of atherosclerosis — narrowing of the arteries due to accumulation of fatty deposits — and the speed with which it develops. High levels of homocysteine, the amino acid in your blood can cause your arteries to thicken and scar, which makes them more susceptible to clots.
Cigarette smoking. Smoking increases your risk of blood clots, raises your blood pressure and contributes to the development of cholesterol-containing fatty deposits in your arteries (atherosclerosis).
The best way to prevent stroke is to advise and identify those who may be at risk, to seek advice from their GP for either advice on lifestyle changes or drug therapy in order to reduce blood pressure. Family history. Your risk may be greater if one of your family members has had a TIA or a stroke. Non modifiable risk factors include
Your risk increases as you get older, especially after age 55. Men have a slightly higher likelihood of a TIA and a stroke, but more than half of deaths from strokes occur in women. Previous transient ischemic attack. If you've had one or more TIAs, you're 10 times more likely to have a stroke. Sickle cell disease. Also called sickle cell anemia, a stroke is a frequent complication of this inherited disorder. Sickle-shaped blood cells carry less oxygen and also tend to get stuck in artery walls, hampering blood flow to the brain. However, with proper treatment for sickle cell disease, you can lower your risk of a stroke. Race. Black people are at greater risk of dying of a stroke, partly because of the higher prevalence of high blood pressure and diabetes among blacks.
Because of this criss-cross wiring, damage to one side of the brain affects the opposite side of the body, so when we wink with our left eye, our right side of the brain is working. The brain's right hemisphere controls the muscles on the left side of the body, while the left hemisphere controls the muscles on the right side of the human body. Now knowing this, we can diagnose easier what part of the brain is being affected by stroke. If a patient is suffering from a right hemispheric stroke, symptoms may include, slurred speech – dysarthria, weakness or numbness of left face, arm or leg, Left sided neglect, Right gaze preference. Likewise, with left hemispheric stroke, patients may suffer with symptoms including speech problems – what is being said or inability to get words out, problems with comprehension, weakness or numbness of right face, arm, or leg, left gaze preference. Brain stem stroke can be even more difficult to diagnose pre hospitably despite their being a number of recognisable symptoms, they are complex. A patient may be presenting with vertigo, dizziness and imbalance altogether, however dizziness alone is not a sign of a stroke. Also, with Brain stem stroke, there isn’t the hallmark symptom of a stroke, weakness on one side, but other symptoms may include, slurred speech, double vision, decreased level of consciousness, abnormal eye movements and problems swallowing. All motor function for the brain runs through the brainstem, therefore any or all motor functions can be affected by it. It can also cause locked-in syndrome, a condition which survivors can only move their eyes. Brain stem also controls all basic activity in the central nervous system, level of consciousness, blood pressure, and breathing. Brain stem Stroke can be life threatening.
The ambulance service currently use the FAST test in order to diagnose a stroke however there are numerous other detailed test for example as shown in figure 14, ROSIER assessment tool using a scoring system to determine whether a patient is having a stroke and the severity of it, however, the type of stroke someone is having will be determined by a CT scan in hospital, therefore early transport is important.
Sanders’ refers to the 7 D’s of stroke management. Detection- early recognition and call for ambulance. Dispatch- Ambulance is dispatched and the call is regarded as time critical, therefore of high priority. Delivery – it is important that this is treated as time critical so the early treatment can be done , increasing the patients ability to recover. Door- it is vitally important the patient Is triaged properly. It is vitally important this patient is brought to the appropriate care provider. Data- Always try and transport a stroke patient to a facility that has a Computed Tomography (CT) Scan. Decision- following the CT scan reading, the patients need for Thrombolysis or surgery is considered. Drug- Patient is treated appropriately.
History taking in stroke patients is vital. We must find out the time of the onset of symptoms, this is in order to triage, if we discover a stroke within a timeframe of 4.5 hours from onset, it allows for early intervention through the use of thrombolysis. We must identify when the patient has last seemed normal. Thrombolysis is a treatment by which IV administered drugs dissolve dangerous clots and in turn improve blood flow and preventing further tissue or organ damage. The treatment can also include a mechanical device at the end of a catheter to break up or remove the clot. 25% of thrombolysis treatment is unsuccessful however, and a 12% of patients subsequently redevelop the clot or blockage in the blood vessel. In addition, thrombolysis alone -- even when successful -- cannot treat already damaged tissue from poor perfusion, So, further treatment such as surgery, may be needed to identify the causes of the blood clot and repair damaged tissues and organs.
If tPA is unavailable or the patient is outside the timeframe for administration, other treatments are available. Intra- arterial Thrombolysis may be used, however a strict criteria mut be met. A catheter is used to administer tPA directly into the clot. This can be done up to 6 hours after onset of symptoms. Alternatively, mechanical Thrombectomy is a procedure used to retrieve the clot, this is used if IV-tPA is ineffective or the patient is ineligible for the treatment
Stroke is the leading global cause of death and disability. Two-thirds of all strokes affect individuals in low- and middle-income countries. It is predicted that by 2025, 4 out of every 5 strokes will occur in people of these regions. Stroke incidence is predicted to go up also. . On average, someone has a stroke every five minutes in the UK, that’s more than 100,000 per year and there are over 1.2 million stroke survivors in the UK. Strokes cost the NHS and social care £1.7 billion a year in England, so its burden is clear.