What is hydrocephalus?
Hydrocephalus comes from the Greek hydro meaning water and cephalie, meaning brain. A watery fluid, known as cerebro-spinal fluid or CSF, is produced constantly inside each of the four spaces or ventricles inside the brain: between 400 and 600mls is produced each day. The CSF normally flows through narrow pathways from one ventricle to the next, then out over the outside of the brain and down the spinal cord. The CSF is absorbed into the bloodstream, and the amount and pressure are normally kept within a fairly narrow range.
If the drainage of CSF is prevented at any point, the fluid accumulates in the ventricles inside the brain, causing them to swell and resulting in compression of the surrounding tissue. In babies and infants, the head will enlarge. In older children and adults, the head size cannot increase as the bones which form the skull are completely joined together.
What causes hydrocephalus?
The condition is caused by the inability of CSF to drain away into the bloodstream. There are many reasons why this can happen. Hydrocephalus can be congenital or acquired.
Key
Cerebrum: The main part of the brain, in two halves one on each side (left and right hemispheres).
Cerebellum: The smaller part of the brain at the back of the head, involved in muscular coordination.
Ventricles: Connected spaces inside the brain, where CSF is produced. There are two lateral ventricles (one each side), a third ventricle and a fourth ventricle. CSF flows from here over the outside of the brain before being absorbed back into the bloodstream.
Choroid plexus: The organ that makes CSF.
Superior sagittal sinus: The major vein that runs over the centre of the top of the brain and collects CSF, draining it back into the central bloodstream.
Pituitary gland: A gland situated in the brain cavity but just behind the face. It is very important in secreting a large number of hormones that regulate body function and development. An example is growth hormone, and others are involved in sexual development.
Brainstem: A very important area connecting the spinal cord to the brain. It controls breathing and other vital functions.
Spinal cord: A complex trunk of nerves transmitting impulses to all parts of the body, allowing muscle movement, sensation and reflexes.