Stroke

• 1. Introduction

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  Stroke is the moment the brain runs out of blood. In 2023-15 million people worldwide had one. In 2021, strokes were the third biggest cause of death, responsible for roughly 10% of total deaths. A person may suddenly find one side of their face drooping, an arm they cannot lift, words that will not form. These signs often appear within moments of the event. About half of those who have a stroke live less than one year afterward. Two thirds of cases occur in people over 65 years old. Yet a stroke is not one thing but two opposite things, and the difference decides everything that follows. What happens inside the brain in those first minutes? Why does one mnemonic spelled out as FAST sit at the center of how the world is taught to respond? And what does it take to rebuild a life once the blood returns too late?

• 2. Two Opposite Disasters

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  About 87% of strokes are ischemic, the rest hemorrhagic. An ischemic stroke happens when blood supply to part of the brain is interrupted, starving the tissue. A hemorrhagic stroke is the reverse: a blood vessel ruptures, or an abnormal vascular structure gives way, and blood floods where it should not be. Ischemic strokes arise four ways. A clot can form locally and block a vessel, called thrombosis. A traveling particle, an embolus, can lodge from elsewhere, called embolism. Blood supply can drop across the whole system, as in shock, called systemic hypoperfusion. Or the brain's draining veins can clot, cerebral venous sinus thrombosis. Hemorrhagic strokes split into their own two families. Intracerebral hemorrhage is bleeding within the brain itself, when an artery bursts and floods surrounding tissue. Subarachnoid hemorrhage bleeds outside the brain tissue but still inside the skull, precisely between the arachnoid mater and the pia mater. That subarachnoid form classically announces itself with a thunderclap headache, a severe pain at maximum the instant it begins. Intracerebral hemorrhage carries a mortality rate of 44% after 30 days, higher than either an ischemic stroke or a subarachnoid hemorrhage. The boundary between the two categories can blur. Bleeding can develop inside an area of ischemia, a condition called hemorrhagic transformation, and it is unknown how many hemorrhagic strokes actually begin as ischemic ones.

• 3. The Ischemic Cascade

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  With oxygen and glucose cut off, brain cells switch to anaerobic metabolism, which yields far less energy and leaves behind lactic acid. That acid is an irritant. It disrupts the brain's normal acid-base balance and can destroy cells. The damaged zone has a name borrowed from astronomy: the ischemic penumbra, the dimmer ring around a darker core. As energy fails, the ion pumps that keep nerve cells stable shut down. Glutamate transporters then run in reverse, dumping the excitatory neurotransmitter glutamate into the spaces between cells. Glutamate floods receptors, especially NMDA receptors, and triggers a rush of calcium that switches on enzymes which digest the cell's own proteins, lipids, and nuclear material. The brain is uniquely fragile here. It has little respiratory reserve and depends entirely on aerobic metabolism, unlike most other organs. If ischemia lasts more than 5 minutes with blood flow below 5% of normal, some neurons die. Severe ischemia lasting more than 15 to 30 minutes kills all the affected tissue, leading to infarction. Temperature shifts the rate, with heat speeding the damage and cold slowing it. The brain does have a backup. The collateral system links the carotid and vertebral arteries through the circle of Willis, and prompt restoration of blood flow can still rescue the moderately starved penumbra around a dead core.

• 4. Reading The Warning Signs

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  Sudden face weakness, an arm that drifts downward when both are raised, and abnormal speech are the three findings most likely to identify a stroke. When at least one is present, the likelihood rises by a factor of 5.5. When all three are absent, the likelihood drops. These checks are valuable precisely because they can be done quickly and easily in an emergency. From these signs comes FAST: facial droop, arm weakness, speech difficulty, and time to call emergency services. It is advocated by the Department of Health in the United Kingdom and the Stroke Association, the American Stroke Association, and the National Stroke Association in the United States. FAST has a blind spot. It is less reliable for a posterior circulation stroke, the kind affecting the back of the brain. The revised mnemonic BE FAST answers that gap by adding balance and eyesight, catching sudden trouble standing or new blurry, double, or lost vision. Younger patients are especially likely to slip through. Adults under 44 are seven times more likely to have a missed stroke than adults over 75, particularly with posterior circulation infarcts. Some strokes leave no warning at all. A silent stroke produces no outward symptoms, yet still damages the brain and raises the risk of a future major stroke. It is estimated to occur at five times the rate of a symptomatic stroke, often revealed only later as a lesion on an MRI scan.

• 5. The Race For The Clock

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  "Time is Brain!" was how the premise of rapid intervention was summed up in the early 1990s. The idea that faster restoration of blood flow means fewer dying brain cells was later proved and quantified. A stroke is a medical emergency, and the treatment depends on the type, the time elapsed, and the underlying cause. For ischemic strokes, the first goal is to remove the blockage. Thrombolysis breaks the clot down with a drug. Given within three hours of symptom onset, recombinant tissue plasminogen activator delivers an overall 10% benefit toward living without disability, though it does not improve survival. Benefit is greater the earlier it is used, and after four and a half hours thrombolysis worsens outcomes. The clot can also be pulled out by hand. Mechanical thrombectomy removes the clot from a large artery such as the middle cerebral artery. A 2015 review showed it safe and effective within 12 hours of onset, and certain cases benefit up to 24 hours later. When a stroke swells large portions of the brain, a so-called malignant cerebral infarction, surgeons may perform a hemicraniectomy, temporarily removing part of the skull to relieve the pressure. Hemorrhagic strokes demand the opposite reflexes. Anticoagulants and antithrombotics make bleeding worse and are generally stopped and reversed, while blood pressure, glucose, and oxygen are held at optimum levels.

• 6. The Long Pressure

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  High blood pressure accounts for 35 to 50% of stroke risk, the single biggest factor. Reducing systolic pressure by 10 mmHg, or diastolic by 5 mmHg, cuts stroke risk by about 40%. Lowering blood pressure has been conclusively shown to prevent both ischemic and hemorrhagic strokes, and even people older than 80 benefit. Other modifiable risks crowd behind it. Atrial fibrillation, diabetes mellitus, high cholesterol, end-stage kidney disease, obesity, heavy alcohol use, and physical inactivity all raise the odds. Smoking just one cigarette per day increases the risk by more than 30%. Diabetes mellitus alone raises stroke risk by two to three times. Some risks hide in unexpected places. Migraine with aura doubles a person's risk of ischemic stroke. Untreated celiac disease can be an underlying cause in both children and adults. A 2021 WHO study found that working 55 or more hours a week raises stroke risk by 35% compared with a 35 to 40-hour week. Prevention has its own arithmetic. For people with atrial fibrillation, who carry a 5% yearly stroke risk, anticoagulation can reduce recurrent stroke by 60% while antiplatelets reduce it by 20%. Surgery offers a sharper trade. Carotid endarterectomy can cut the recurrence risk from up to 20% over five years down to around 5%, but it works best when performed within two weeks of the first stroke.

• 7. Rebuilding A Life

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  Disability affects 75% of stroke survivors enough to reduce their ability to work. Stroke can strike the body, the mind, the emotions, or all three, and the results vary widely with the size and location of the lesion. Up to 10% of people develop seizures afterward, most often in the week following the event. An estimated 15% live with urinary incontinence for more than a year, and 50% experience a decline in sexual function. Rehabilitation gathers a crowd around the survivor. The team may include neurologists, clinical pharmacists, physiotherapists, occupational therapists, speech-language pathologists, and orthotists, because at least one third of affected people develop post-stroke depression. Most return of function comes in the first few months, and U.S. rehabilitation units consider the window officially closed after six months. Yet some survivors report improving for years, regaining writing, walking, running, and talking. The emotional toll runs deep and specific. Between 30 and 50% of survivors develop post-stroke depression, marked by lethargy, irritability, and withdrawal, most common when the stroke hits the anterior brain or the basal ganglia, particularly on the left side. Emotional lability can make a person swing between laughing and crying with little provocation. Many find the social isolation of lost speech harder to bear than any physical loss, which is why broader care must reach the person behind the symptoms.