How does an ischemic stroke occur?

An ischemic stroke occurs when there is a blockage in an artery supplying blood to the brain, typically due to a blood clot. This clot can form in the arteries leading to the brain or can travel from another part of the body (often the heart) and lodge itself in a cerebral artery. Because blood flow is essential for delivering oxygen and nutrients to brain cells, any interruption can lead to cell damage and loss of brain function.

In contrast, a ruptured blood vessel in the brain describes a hemorrhagic stroke, which is a different condition and not what constitutes an ischemic stroke. Similarly, while brain tumors can exert pressure on arteries and potentially contribute to various neurological symptoms, they do not cause ischemic strokes by directly blocking blood flow in the same manner as a clot. A sudden increase in blood flow is also not a mechanism for an ischemic stroke; rather, this could lead to other complications, such as hemorrhagic strokes or other types of vascular injury. Thus, identifying that blockage of an artery by a clot is the primary cause of ischemic strokes is crucial for understanding this medical emergency.