A stroke occurs when the blood supply to part of the brain is interrupted or severely reduced, depriving brain tissue of oxygen and nutrients. Brain cells begin to die within minutes. Common symptoms often appear suddenly and include sudden numbness or weakness in the face, arm, or leg (especially on one side of the body), sudden confusion, trouble speaking or understanding speech, sudden vision problems, sudden trouble walking, dizziness, and sudden severe headache with no known cause. MRI is a highly effective tool for detecting a stroke. It uses powerful radio waves and a magnetic field to create detailed images of the brain. An MRI can detect changes in the water content of brain tissue where blood flow has been reduced, indicating damage from an ischemic stroke, often within a few hours of its onset. It can also identify brain tissue damaged by a hemorrhagic stroke (bleeding in the brain).
