Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Hydrocephalus ?
    ### Response:
    Hydrocephalus is a condition in which the primary characteristic is excessive accumulation of cerebrospinal fluid (CSF) -- the clear fluid that surrounds the brain and spinal cord. This excessive accumulation results in an abnormal dilation of the spaces in the brain called ventricles.
    