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What Is a Stroke?

Computer generated brain showing an injury site
A stroke occurs when any part of the brain is deprived of blood flow (hence, oxygen) and the affected brain cells die. As the third leading cause of death in the United States, a stroke is a big deal. Even after a few minutes, brain cells will die, so the faster you reestablish blood flow to the affected area, the better the prognosis will be. You can have anything from a small, localized stroke which passes in minutes or hours (what is known as a TIA, or transient ischemic attack) or you can have a major stroke which can kill you, or leave you severely brain damaged. Stroke is the leading cause of permanent disability in the United States.

Because we’re talking about brain tissue, one fact is worth stating: brain tissue doesn’t grow back. It’s one of the few tissues in the body where once the brain matures, that’s all you get! So when blood flow is interrupted, you better get it back in a hurry! (New studies are indicating some portions of the brain can revert back to an embryonic state in some conditions, but that’s developing research.)

The two types of strokes are ischemic (that is, caused by a blood clot) and hemorrhagic (caused by a weakened blood vessel that’s burst.) Ischemic strokes are by far the most common (87% of strokes are ischemic). If a stroke is ischemic, and the patient can get immediate treatment, a clot-busting drug can be given within three hours after the onset of the symptoms.

In the image on the right, a clot-busting drug is administered to a patient suffering from an ischemic stroke, and the results are impressive. But keep in mind how quickly the time elapses when you’re having any kind of medical emergency for the first time. If you live near a hospital, and someone can drive you there, you might get there in 60-90 minutes from the onset of symptoms (if the stroke was instantly identified). If the hospital is ready for you, the MRI would take 30 minutes, and then it would need to be reviewed (another 30 minutes), and if a clot-buster is called for 30 more minutes to prep and administer it. You’d be hard-pressed to get it in in under three hours! (The image on the right was likely taken from a patient already in the hospital.)   

Brain MRI showing clot-busting drugs
Diagram indicating how brain tissue dies downstream from a blood clot
From Columbia Neurosurgery

Two things will impact how serious a stroke will be: where the interruption of blood flow occurs, and how long before it’s treated. Given the myriad of vascular pathways in the brain, it’s impossible to predict where a blood clot will lodge (in the case of ischemic stroke.) But there’s no part of the brain that’s good when damaged. It means that two people who’ve suffered strokes will have different outcomes, but neither one will be desirable.

As for the question of treatment time, seconds and minutes are more crucial than for most other medical emergencies. Get to a hospital immediately!

Ischemic Stroke vs. Hemorrhagic Stroke

Ischemic strokes are brought on by blood clots, and are by far the more typical (87% of strokes), but hemorrhagic strokes, which occur far less frequently, are typically more serious (a bleed from a ruptured blood vessel). These have a much higher mortality rate than ischemic strokes.

Ischemic strokes have a chance to turn into hemorrhagic strokes if left too long without attention. The blood vessels weaken when they’re starved of blood, and if blood flow is reestablished, they’ll burst. This typically happens 24-48 hours after an ischemic stroke’s onset. This is referred to as a hemorrhagic conversion or hemorrhagic transformation. If a stroke is bad, a hemorrhagic conversion is far worse!

“For patients with hemorrhagic primary [a hemorrhagic stroke] or conversion strokes [an ischemic stroke that went through a hemorrhagic conversion] or those with life-threatening elevation in their intracranial pressure, urgent neurosurgical consultation is required…”

“Acute Stroke: Slideshow” on

An ischemic stroke that's undergone a hemorrhagic conversion

The adjacent image shows an MRI with a large portion of the brain affected by a hemorrhagic conversion (the left side of the MRI). This image was presented in “Acute Stroke: Slideshow” on, a web site of medical news for doctors.


Strokes don’t just happen to your grandparents! They’re a very real threat to seemingly fine, healthy people. Nowhere is it more critical that you get to a hospital immediately, than if a stroke is suspected!

My stroke left me on the floor in my apartment for three-and-a-half days before I got help. But that is another story…

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