Acute ischemic stroke explained

Acute ischemic stroke happens when a blood clot blocks a brain artery, cutting off blood supply to part of the brain. Brain cells in the affected area begin to die within minutes; surrounding cells can survive for several hours if blood flow is restored. The classic warning signs are sudden weakness on one side of the body, trouble speaking or understanding speech, sudden vision changes, severe sudden headache, or sudden dizziness or loss of balance.

Why time matters. The phrase "time is brain" captures the reality that every minute of delay means more brain cells die. Modern stroke care is built around getting blood flow restored as quickly as possible.

The two main acute treatments.

Intravenous thrombolysis: a medicine given through a vein that dissolves the clot. The standard medicine has been alteplase; tenecteplase is replacing it in many centres because it can be given as a single push rather than infused over an hour. The treatment window is typically up to 4.5 hours from when symptoms started.

Mechanical thrombectomy: a procedure in which a thin tube is threaded through the blood vessels into the brain artery containing the clot, and the clot is removed mechanically. This is the option for patients with clots in large brain arteries. The treatment window is typically up to 6 hours from onset, extended to 24 hours in selected patients whose brain imaging shows tissue still salvageable.

The stroke system. Modern stroke care depends on rapid recognition (Act FAST), rapid transport to an appropriate hospital, rapid imaging, and rapid intervention. Comprehensive stroke centres can provide both treatments; primary stroke centres can give thrombolysis and arrange transfer for thrombectomy. Mobile stroke units (specialised ambulances with CT scanners) bring imaging and thrombolysis to the patient.

Secondary prevention. After an ischemic stroke, the goal shifts to preventing the next stroke. This typically involves medicines to prevent clotting (antiplatelets or anticoagulants depending on the cause), lipid-lowering therapy, blood-pressure control, and lifestyle measures. Underlying causes (atrial fibrillation, carotid artery disease, certain heart conditions) are sought and addressed.

What to expect. Outcomes after stroke have improved substantially with modern acute care. Recovery often continues for many months, with rehabilitation playing a central role.