Cerebrospinal fluid or CSF is the fluid that surround the spinal cord and brain.
Cerebrolspinal fluid (CSF) has three important functions:
1) Protect the brain from damage
2) Act as the vehicle to remove waste product from the brain
3) Provide nutrient that the brain needed in order to function properly
The relationship between the brain and Hydrocephalus:
Hydrocephalus is cause by disturbance of CSF circulation in the brain. Too much CSF in the brain may cause ventricles which is abnormal widening of space in brain. It can pressure the tissue in the brain, pushed the brain up against the skull and damage brain's tissue. CSF is made continuously, and because of that balance between the production and absorption of cerebrospinal fluid are important. Hydrocephalus is the medical condition in which it blocks the normal flow of the CSF in the brain.
Source: Google image