The methods of treating hydrocephalus have evolved greatly through history, with the most recent progress being made since 1955 when John Holter an American engineer invented a ball-and-spring valve system to be implanted into his son who had hydrocephalus.  His son's neurosurgeon explained that there was no satisfactory treatment for hydrocephalus. He questioned the surgeon and gained an idea of the sort of treatment required.  He experimented at home and soon developed such a device, made from silicone rubber which had never been implanted into people before but was used as insulation for electrical systems in airplanes.  The surgeon decided to try this, with great success. The Holter valve soon became the treatment of choice for hydrocephalus.  It also revolutionized the treatment of spina bifida, removing the principal cause of death and encouraging orthopedic and  urological surgeons to develop procedures to improve mobility and continence. Other similar devices were developed soon afterwards, all made from the same material and having similar valve mechanisms.

This is a picture of  Johnson & Johnson's CODMAN® Programmable Valve.  

The Shunt System

A shunt is mechanical device that is used to divert the buildup of cerebrospinal fluid to another area of the body where it can be reabsorbed.  A shunt system consists of three parts:  two catheters made of silicone, with a one way valve placed between the two catheters to help CSF flow out of the brain.

The three parts of the shunt are:

Proximal Catheter:  This section of the shunt can either be placed in the ventricles of the brain or the lumbar region of the spine.

Shunt Valve:  The shunt valve is what regulates the flow of CSF between the proximal and distal catheter.  Most shunt valves are known as differential pressure valves and are self-regulating.  The valve should be able to gauge the amount of ICP and adjust to differential pressures between the ventricles and the distal cavity the shunt drains into. 

Distal Catheter:  This section of the shunt is located furthest away from the affected area.  The distal catheter can be placed in peritoneal cavity of the abdomen, this kind of shunt is called a VP shunt (ventriculoperitoneal shunt) and is the most common place to put a distal catheter.  Another common place is the right atriumm of the heart via the internal or external jugular vain.  This kind of shunt is called a VA shunt (ventriculoatrial shunt).  The distal catheter can also be placed into the pleural space that surrounds the lungs and is called a VP1 shunt (ventriculopleural shunt).

Here is a diagram of the placement of a VP shunt and VA shunt.  I got this picture out of another useful source called About Hydrocephalus-A Book For Families.

How Shunts Work

When a shunt system is implanted in a person with hydrocephalus, the goal is for the shunt system is to mimic what would occur in the body naturally.  CSF will be drained by the shunt, and the flow will be regulated so that a constant intracranial pressure ( ICP) is maintained within the brain.  CSF enters the shunt system through small holes or slits near the tip of the proximal catheter.  As CSF is produced by the choroid plexus, the shunt valve regulates the amount of ICP by draining fluid from the ventricles.  From the proximal catheter, CSF flows through the valve system and into the distal catheter, which drains CSF into another area of the body where it can be reabsorbed by the bloodstream.

Here is a basic look at the ventricles in the brain.  Here in this photo you can see tubing.  This is part of the shunt, in this picture there are two different shunts, you can see two proximal catheters and two valves.  Depending on the cause of a person's hydrocephalus most only have one shunt system.  Though it is not uncommon to hear of someone having two shunt systems.  Noah received a second shunt system in January 2005.  However, this one was placed in his lumbar space of his spine.  He now has a VP shunt and a LP shunt.