Hydrocephalus is also known as "water on the brain". It is an abnormal accumulation of cerebral spinal fluid (CSF) in the ventricles in the brain. This may cause increased inter cranial pressure inside the skull, and progressive enlargement of the head, convulsion, & mental disability. Hydrocephalus can cause death if left untreated.
Brookelyn developed hydrocephalus after contracting her bacterial meningitis. When someone has bacterial meningitis their CSF becomes packed with protein and as a result of this many bacterial meningitis cases also develop hydrocephalus like Brookelyn did.