Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Hydrocephalus due to congenital stenosis of aqueduct of sylvius ?
    ### Response:
    Hydrocephalus due to congenital stenosis of aqueduct of sylvius (HSAS) is a form of L1 syndrome, which is an inherited disorder that primarily affects the nervous system. Males with HSAS are typically born with severe hydrocephalus and adducted thumbs (bent towards the palm).
    