Final answer:
Hydrocephalus is the abnormal accumulation of CSF in the brain, which can cause severe symptoms and requires treatment, typically with a shunt insertion.
Step-by-step explanation:
An abnormal accumulation of cerebrospinal fluid (CSF) in the brain is called hydrocephalus. The brain and spinal cord are cushioned by CSF, which is produced in the ventricles. Blockage of the ventricular system can lead to an overaccumulation of CSF, causing the brain to swell and push against the skull. If untreated, hydrocephalus can lead to seizures, cognitive problems, and can be fatal. Treatment often involves the insertion of a shunt to drain the excess fluid and relieve pressure.