Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Periventricular Leukomalacia ?
    ### Response:
    Periventricular leukomalacia (PVL) is characterized by the death of the white matter of the brain due to softening of the brain tissue. It can affect fetuses or newborns; premature babies are at the greatest risk of the disorder. PVL is caused by a lack of oxygen or blood flow to the periventricular area of the brain, which results in the death or loss of brain tissue.
    