Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Cavernous Malformation ?
    ### Response:
    Cerebral cavernous malformations (CCMs) are vascular lesions comprised of clusters of tightly packed, abnormally thin-walled small blood vessels (capillaries) that displace normal neurological tissue in the brain or spinal cord. The vessels are filled with slow-moving or stagnant blood that is usually clotted or in a state of decomposition.
    