stroke
Meaning of stroke: Damage shows up as lost function rather than pain, and which abilities vanish depends on which patch of brain lost its blood.
Definition of stroke
A stroke is sudden injury to part of the brain caused by a loss of its blood supply. A clot may block an artery feeding the brain, or a vessel may burst and bleed into the tissue. Nerve cells in the affected area stop working within seconds and begin to die, so the abilities that region controlled fail abruptly.
What happens when the blood supply stops?
Brain tissue holds no reserve of fuel or oxygen and takes a large share of everything the heart pumps, so an interrupted supply is felt within seconds. The core of the affected territory is lost quickly. Around that core lies a rim of tissue that is starved but not yet dead, kept barely alive by blood seeping in from neighboring vessels. That rim is what treatment aims at, and it shrinks steadily while the artery stays blocked. This is why a stroke counts as a medical emergency in the strictest sense: the treatments that reopen a vessel work only within a limited period after symptoms begin, and the amount of brain saved falls as that period runs on.
What are the two main types?
| Type | What happens | Usual cause |
|---|---|---|
| Ischemic | An artery is blocked and the tissue beyond it starves | A clot forming on fatty plaque, or one carried up from the heart |
| Hemorrhagic | A vessel tears and blood escapes into or around the brain | Years of high blood pressure, or a weakened vessel wall |
The two cannot be told apart at the bedside. Symptoms overlap, an examination does not settle it, and only a brain scan does. That distinction governs everything afterward, because a drug that breaks up clots helps the blocked type and makes the bleeding type worse. Blocked arteries account for much the larger share of cases.
How does a stroke announce itself?
Abruptly, and often without pain. The familiar pattern is one side of the face drooping, weakness or numbness running down one arm or leg, and speech that comes out slurred or scrambled. Vision can be lost to one side, balance can collapse, and a bleed frequently brings a sudden severe headache unlike any the person has had before. Because the injury is confined to the territory one vessel fed, the deficit is usually one sided and specific rather than a vague sense of illness. Symptoms that clear on their own within minutes describe a warning event, not a false alarm.
What happens after the acute phase?
Surviving tissue takes over some of the lost work, a process that runs for months and is the basis of rehabilitation. Physical therapy, speech therapy and occupational therapy retrain movement, language and daily tasks. Because the injury sits in the nervous system rather than in the muscle itself, an affected limb is not weak from disuse; the instructions reaching it are damaged. Attention afterward turns to whatever produced the event, since a first stroke marks out a person at raised risk of a second.
Also known as
Used in a sentence
The stroke involved the left middle cerebral artery territory, leaving right sided weakness.
Good to know
Symptoms that clear completely within minutes still reflect the same disease process, and a blocked artery cannot be told from a bleed at the bedside even though the two call for opposite treatment, so imaging is what separates them.