Cerebral infarction is the medical name for what most people call an “ischemic stroke.” It happens when a clot or other blockage shuts off blood flow to part of the brain. The signs can pop up without warning and usually reach their worst within minutes to a few hours.

The classic warning is sudden weakness or numbness on one side of the body. One side of the face may droop, the arm may drift downward, or the leg may feel heavy or “dead.” Speech often becomes slurred or garbled; some people can’t find the right words or understand simple sentences. Vision can blur or go black in one eye, and many folks feel dizzy or unsteady, as if they’re drunk. A mild headache may appear, but severe head pain is uncommon. Sudden confusion, trouble walking, or loss of balance—like stumbling or dragging a foot—are other key clues. In serious cases, the person may pass out or have a seizure.

Time lost is brain lost. If any of these signs show up, call 911 right away. Fast treatment can reopen the vessel and limit permanent damage.