Below is an instruction from Human. Write a response.
    ### Instruction:
    What causes Bilateral perisylvian polymicrogyria ?
    ### Response:
    What causes bilateral perisylvian polymicrogyria? The exact underlying cause of bilateral perisylvian polymicrogyria (BPP) is unknown. The signs and symptoms associated with the condition are thought to be due to improper development of the outer surface of the brain (cerebral cortex) during embryonic growth.
    