Shunt refresher -
The most common treatment of hydrocephalus is the placement of a shunt (a narrow piece of tubing) into one of the fluid-filled ventricles inside the brain to drain excess fluid. 40,000 shunt surgeries are performed annually.

A shunt has four main parts:
The upper catheter is a small, narrow tube that is inserted into the ventricle (a small opening or pouch) inside the brain that contains the cerebrospinal fluid (CSF).
The reservoir is where the excess CSF is collected, then drains into the bottom portion of the shunt. Doctors can remove samples of CSF by sticking a needle into the reservoir and can inject medication or fluid into the shunt to test for proper flow.
The valve controls how much CSF is allowed to drain from the brain. Most valves work automatically when fluid pressure in the head gets too high. Some valves have special devices to keep too much fluid from draining.
The lower catheter is the bottom-most part of the shunt. It is a small, narrow tube that carries the excess CSF into the part of the body where it will be absorbed.

There are different types of shunt, named after the placement of the lower catheter:
Ventriculo-Peritoneal (VP) – The shunt tubing goes from the ventricle in the brain to the abdominal cavity where the excess fluid is absorbed by the body. This is the most common shunt.
Ventriculo-Pleural – The fluid is moved to the pleural space located outside the lung.
Ventriculo-Atrial – The excess fluid goes to the right atrium cavity of the heart.
Ventriculo-Gall Bladder – Fluid is moved to the gall bladder.
Lumbar-Peritoneal (LP) - These shunts are placed in the lumbar space of the spine and have the CSF redirected to the peritoneal cavity.
Shunts are either programmable or fixed pressure.
Programmable shunts have special valves that can be adjusted to allow more or less fluid to drain.
Fixed pressure shunts have valves that drain at a set rate, either low, medium, or high.
Unfortunately, shunts have a very high failure rate. 50% fail within the first 2 years, requiring more brain surgery. More research is desperately needed to improve the mechanics and to ultimately find a cure that makes shunts obsolete.