Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Arteriovenous Malformation ?
    ### Response:
    Arteriovenous malformations (AVMs) are abnormal, snarled tangles of blood vessels that cause multiple irregular connections between the arteries and veins. These malformations most often occur in the spinal cord and in any part of the brain or on its surface, but can develop elsewhere in the body.
    