Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Ischemic Stroke ?
    ### Response:
    A stroke is a medical emergency. There are two types - ischemic and hemorrhagic. Ischemic stroke is the most common type. It is usually caused by a blood clot that blocks or plugs a blood vessel in the brain. This keeps blood from flowing to the brain. Within minutes, brain cells begin to die.
    