Pratique du Shadowing: Ischemic Stroke - causes, symptoms, diagnosis, treatment, pathology - Apprendre l'anglais à l'oral avec la vidéo
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There are two main types of stroke.
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An ischemic stroke, which is when there is a blocked artery that reduces blood flow to the brain,
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and a hemorrhagic stroke, which is when there is an artery in the brain that breaks, creating a pool of blood that damages the brain.
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Of the two, ischemic strokes are much more common, and the amount of damage they cause is related to the parts of the brain
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that are affected and how long the brain suffers from reduced blood flow.
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Now, if symptoms self -resolve within 24 hours, it's called a transient ischemic attack, and there are usually minimal long -term problems.
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Okay, let's start with some basic brain anatomy.
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The brain has a few regions.
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The most obvious is the cerebrum, which is divided into two cerebral hemispheres, each of which has a cortex,
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an outer region divided into four lobes including the frontal lobe, the parietal lobe, the temporal lobe, and the occipital lobe.
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There are also a number of additional structures including the cerebellum
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which is down below as well as the brainstem which connects to the spinal cord.
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The right cerebrum controls muscles on the left side of your body and vice versa.
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The frontal lobe controls movement and executive function which is our ability to make decisions.
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The parietal lobe processes sensory information which lets us locate exactly where we are physically
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and guides movement in a three -dimensional space.
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The temporal lobe plays a role in hearing, smell, memory, as well as visual recognition of faces and language.
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Finally, there's the occipital lobe, which is primarily responsible for vision.
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The cerebellum helps with muscle coordination and balance.
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And finally, there's the brain stem, which plays a vital role in functions like heart rate, blood pressure, breathing, gastrointestinal function and consciousness.
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The brain receives blood from the left and right internal carotid arteries, as well as the left and right vertebral arteries,
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which come together to form the basilar artery.
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The internal carotid arteries turn into the left and right middle cerebral arteries, which serve the lateral portions of the frontal,
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parietal, and temporal lobes of the brain.
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Each of the internal carotid arteries also gives off branches called the anterior cerebral arteries
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which serve the medial portion of the frontal and parietal lobes
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and connect with one another with a short little connecting blood vessel called the anterior communicating artery.
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Meanwhile, the vertebral arteries and basilar arteries give off branches to supply the cerebellum and the brain stem.
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In addition, the basilar artery divides to become the right and left posterior cerebral artery,
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which mainly serves the occipital lobe and some of the temporal lobe as well as the thalamus.
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Finally, the internal carotid arteries each give off a branch called the posterior communicating artery, which attaches to the posterior arteries on each side.
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So together, the main arteries and the communicating arteries complete what is called the circle of willis,
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a ring where blood can circulate from one side to the other in case of a blockage.
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The Circle of Willis offers alternative ways for blood to get around an obstructed vessel.
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In general, the brain can get by on diminished blood flow, especially when it happens gradually, because that allows enough time for collateral circulation to develop,
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which is where a nearby blood vessel starts sending out branches of blood vessels to serve an area that's in need.
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But once the supply of blood flow is reduced to below the need of the tissue, it causes tissue damage, which we call an ischemic stroke.
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There are two main ways an ischemic stroke happens.
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One mechanism is endothelial cell dysfunction, which is when something irritates or inflames the slippery inner lining of the artery, the tunica intima.
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One classic irritant is the toxin found in tobacco, which floats around in the blood damaging the endothelium.
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That damage becomes a site for atherosclerosis, which is where a plaque forms.
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This is when a buildup of fat, cholesterol, proteins, calcium, and immune cells form and start to obstruct arterial blood flow.
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This plaque has two parts to it, the soft, cheesy, textured interior and the hard outer shell which is called the fibrous cap.
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Branch points in arteries and particularly the internal carotid and middle cerebral arteries are the most common spots for atherosclerosis.
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Usually though, it takes years for plaque to build up and this slow blockage only partially blocks the arteries.
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And so even though less blood makes it to the brain tissue, there's still some blood.
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So strokes happen when there is a sudden and complete or nearly complete blockage of the artery.
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So let's see how that can happen.
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Since plaques sit in the lumen of the blood vessel, they're constantly being stressed by mechanical forces from blood flow,
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and interestingly, it's often the smaller plaques that are more dangerous.
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Their fibrous caps are softer than the large ones, and are prone to getting ripped off.
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Once that happens, the inner cheesy filling is exposed to the blood and is thrombogenic, which means that they tend to form clots very quickly.
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Platelets adhere to the exposed cheesy material and they release chemicals that enhance the clotting process.
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Within a minute, that artery can be fully blocked.
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Another mechanism for ischemic stroke formation is an embolism.
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An embolic stroke typically happens when a blood clot breaks off from one location, travels through the blood, and gets lodged in an artery downstream,
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typically an artery, arterial, or capillary with a small diameter.
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These blood clots typically emerge from atherosclerosis but they can also form in the heart.
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For example stagnant blood flow can form a clot and blood can stagnate due to atrial fibrillation or after a heart attack.
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If a clot forms in the left atrium it moves into the left ventricle
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and from there it has direct route to the brain.
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On the other hand
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And if a clot forms in the low pressure veins or right atrium,
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then it goes to the right ventricle and gets lodged in the pulmonary capillaries, with no way of getting to the brain.
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An important exception is if a person has a heart defect, like an atrial septal defect, that allows blood
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and potentially a blood clot to wander from the right side of the heart over to the left side of the heart.
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In that situation, a venous or right atrial blood clot will have bypassed the pulmonary circulation and established a route to the brain.
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One specific type of ischemic stroke is called a lacunar stroke,
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and they typically involve the deep branches of the middle cerebral artery that feed the basal ganglia.
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Lacunar refers to lake, and is called that since after a lacunar stroke,
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the damaged brain tissue develops fluid -filled pockets called cysts that look like little lakes under a microscope.
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Lacuna strokes classically develop as a result of highline arteriolosclerosis, which is when the arteriole wall gets filled with protein.
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This can happen as a result of hypertension or diabetes, and can make the artery wall quite thick, reducing the size of the lumen.
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In addition to problems specific to an artery, something like shock can lead to reduction in blood flow throughout the entire body.
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In these cases, the tissues that are the furthest downstream are affected the most.
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This is because healthy tissue continues to extract what it needs from the blood flowing by,
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leaving little to no oxygen and nutrients for the tissue furthest away.
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The furthest downstream tissues in the brain are at the border of two different blood supplies.
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When the blood flow throughout the body is diminished for any reason, they get damaged, and this pattern of injury is called a watershed infarct.
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Regardless of the mechanism of an ischemic stroke, it's helpful to remember that there is an ischemic core,
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which is the brain tissue that will likely die from ischemia, and then there is the tissue around the core,
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called the ischemic penumbra, which is preserved for a period of time by collateral circulation
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and has a chance to survive if blood flow is restored quickly enough.
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Regardless of the type of ischemic stroke, without a steady supply of glucose and oxygen, cells run out of energy within minutes,
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and you get a high buildup of sodium and calcium levels in the cells.
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High sodium levels draw water into the cell, making it swell, and this is called cytotoxic edema.
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And high calcium leads up to the buildup of reactive oxygen radicals
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that react with lipids in the membranes of mitochondria and lysosomes.
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Damage to these organelles allow apoptosis inducing factors and degradative enzymes to seep out of the cell.
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Over a period of 4 -6 hours, immune cells begin to haul away damaged cells, and the resulting inflammation damages the blood -brain barrier,
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allowing fluids and proteins to get into the brain tissue, causing swelling or vasogenic edema.
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Because the skull creates a fixed volume,
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the swelling leads to a mass effect where the swollen brain tissue pushes into the unaffected side of the brain, called cingulate, or uncal herniation,
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or slips down and out of the base of the skull,
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called cerebellar tonsil herniation, which is particularly dangerous because it can push onto the brainstem and affect breathing and consciousness.
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Stroke symptoms depend on the exact part of the brain that is affected.
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For example, an interior or middle cerebral artery stroke can cause numbness and sudden muscle weakness.
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If a stroke affects the BRCA area, which is usually the left frontal lobe, or the Wernicke's area, which is usually the left temporal lobe,
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then it can cause slurred speech or difficulty understanding speech, respectively.
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If there's a posterior cerebral artery stroke, then it can affect vision.
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An acronym to remember some common stroke symptoms is FAST.
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Facial drooping, arm weakness, speech difficulties, and time.
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Time is obviously not a symptom,
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but just a reminder to help as quickly as possible to minimize cell injury and maximize the chance of a full recovery.
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To diagnose and confirm the location and size of an ischemic stroke, medical imaging with a CT or MRI can be used.
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Also, angiography, which uses a contrast injected into the blood, can help to visualize the exact location where blood flow is blocked within an artery.
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In addition, using flare -sequenced MRIs, it's possible to distinguish a new stroke injury from an old one.
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In an ischemic stroke, the ultimate treatment is to re -establish blood flow as quickly as possible to prevent further cell injury, particularly in the penumbra.
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Every minute counts.
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So thrombolytic enzymes like tissue plasminogen activator or TPA are used to activate the blood's natural clot -busting mechanism,
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but TPA does have a time limit of when it can be used.
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Aspirin is also used to prevent platelets from forming additional clots.
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If TPA is unsuccessful, surgical procedures can be used that push a wire through the artery and physically remove the clot.
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In mechanical embolus removal in cerebral ischemia, called MERCY for short, the wire grabs onto the clot and draws it out of the artery.
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In suction removal, the wire is used to physically break down the clot and the clot fragments are removed with suction.
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After a stroke has occurred, there is an elevated risk of having additional strokes, so it's important to minimize risk factors,
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the main one being quitting smoking, but others include having a healthy blood pressure, normal LDL cholesterol levels, and controlling other diseases like diabetes.
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Occasionally, a surgery may be necessary to help clean arteries obstructed by severe atherosclerosis.
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For example, in a carotid endarterectomy, the internal carotid artery is opened up and atherosclerotic plaque is removed.
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Alternatively, a stent might be placed to keep the artery opened up.
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Okay, as a quick recap, an ischemic stroke occurs when there is an acute decrease in the arterial blood supply.
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It can be due to atherosclerosis, a thrombus, or an embolus, or a global reduction in blood flow.
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The goal is to identify symptoms and re -establish blood flow to prevent long -term damage.
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To remember this, a common acronym is FAST, facial drooping, arm weakness, speech difficulties, and time.
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Vocabulaire et conseils d’expression pour cette leçon
Cette leçon d’expression orale s’appuie sur la vidéo « Ischemic Stroke - causes, symptoms, diagnosis, treatment, pathology ». Les mots qui reviennent le plus souvent : blood, stroke, artery, brain, arteries. Cette vidéo contient 83 phrases et 2020 mots à répéter en shadowing. La partie parlée dure 13:06. Le locuteur parle à un rythme naturel d’environ 154 mots par minute, proche d’une conversation courante. Seuls 70 % des mots font partie des 3 000 mots les plus courants en anglais, le vocabulaire est donc exigeant.
Vocabulaire clé de cette vidéo
15 mots de la vidéo à retenir, avec leur prononciation et leur sens :
| Mot | Prononciation | Sens |
|---|---|---|
| artery nom | /ˈɑɹ.təɹ.i/ | artère |
| tissue nom | /ˈtɪʃ.(j)u/ | tissu |
| cerebral adjectif | /səˈɹi.bɹəl/ | cérébral |
| plaque nom | /plæk/ | plaque |
| vessel nom | /ˈvɛsəl/ | vaisseau |
| temporal adjectif | /ˈtɛm.pə.ɹəl/ | temporel |
| mechanism nom | /ˈmɛk.ə.nɪ.zəm/ | mécanisme |
| symptom nom | /ˈsɪm(p)təm/ | symptôme |
| muscle nom | /ˈmʌs.əl/ | muscle |
| wire nom | /ˈwaɪɚ/ | fil |
| connect verbe | /kəˈnɛkt/ | accoupler, connecter |
| difficulty nom | /ˈdɪfɪkəlti/ | difficulté |
| physically adverbe | /ˈfɪz.ɪ.kli/ | physiquement |
| oxygen nom | /ˈɑksɪd͡ʒən/ | oxygène |
| communicate verbe | /kəˈmjuːnɪkeɪt/ | communiquer |
Les verbes à particule que vous entendrez
| Mot | Prononciation | Sens |
|---|---|---|
| give off verbe | /ɡɪv ɒf/ | émettre |
| open up verbe | ouvrir | |
| break down verbe | tomber en panne | |
| build up verbe | s'accumuler, s'entasser | |
| rip off verbe | arnaquer, escroquer |
La grammaire de cette vidéo
Les structures que le locuteur utilise le plus, avec les mots exacts de la vidéo :
| Structure | Dans la vidéo |
|---|---|
| Voix passive be + participe passé — l’accent est mis sur ce qui arrive, pas sur qui le fait | are affected · is divided · is called |
| Propositions relatives who / which + proposition — une précision sur une personne ou une chose | stroke, which is · cerebrum, which is · function which is |
Prononciation à surveiller
- Les sons « th »: breathe /bɹiːð/, thick /θɪk/, atherosclerosis /ˌæθɚoʊskləˈɹoʊsəs/, furthest /ˈfɜː(ɹ)ðɪst/
- Les sons « sh » et « zh »: tissue /ˈtɪʃ.(j)u/, circulation /ˌsɝkjʊˈleɪʃən/, reduction /ɹɪˈdʌk.ʃən/, consciousness /ˈkɑnʃəsnəs/, recognition /ˌɹɛkəɡˈnɪʃ(ə)n/
- Mots longs — placez bien l’accent: mechanism /ˈmɛk.ə.nɪ.zəm/, difficulty /ˈdɪfɪkəlti/, communicate /kəˈmjuːnɪkeɪt/, circulation /ˌsɝkjʊˈleɪʃən/, anterior /ænˈtɪɹ.i.ɚ/
Les sons difficiles pour les francophones :
- /h/ — il se souffle, il n’est pas muet: helpful /ˈhɛlp.fl̩/, enhance /ɪnˈhæns/, haul /hɔl/
- /tʃ/ et /dʒ/ — à ne pas adoucir en « ch » et « j »: oxygen /ˈɑksɪd͡ʒən/, cheesy /ˈt͡ʃiːzi/, lodge /lɑd͡ʒ/, procedure /pɹəˈsiː.d͡ʒə/, gradually /ˈɡɹæd͡ʒuəli/
- /r/ anglais — langue recourbée, sans frotter la gorge: artery /ˈɑɹ.təɹ.i/, cerebral /səˈɹi.bɹəl/, temporal /ˈtɛm.pə.ɹəl/, downstream /ˌdaʊnˈstɹiːm/, anterior /ænˈtɪɹ.i.ɚ/
Comment s’entraîner avec cette vidéo
- Écoutez la vidéo en entier une fois sans parler et notez les mots que vous ne connaissez pas.
- Commencez à la vitesse 0,75×, répétez phrase par phrase, puis revenez à la vitesse normale quand cela devient facile.
- Enregistrez-vous et comparez avec l’original, en faisant attention à des mots comme artery, tissue, cerebral.
Qu'est-ce que la technique du Shadowing ?
Le Shadowing est une technique d'apprentissage des langues fondée sur la science, développée à l'origine pour la formation des interprètes professionnels. Le principe est simple mais puissant : vous écoutez de l'anglais natif et le répétez immédiatement à voix haute — comme une ombre suivant le locuteur avec un décalage de 1 à 2 secondes. Les recherches montrent une amélioration significative de la précision de la prononciation, de l'intonation, du rythme, des liaisons, de la compréhension orale et de la fluidité.