The following excerpt is taken from Chapter Four of
Hydrocephalus: A Guide for Patients, Families, and Friends
by Chuck Toporek & Kellie Robinson, copyright 1999 by
O'Reilly & Associates, Inc. For book orders/information,
call 1-800-998-9938. Permission is granted to print and
distribute this excerpt for noncommercial use as long
as the above source is included. The information in this
article is meant to educate and should not be used as an
alternative for professional medical care.
Not all shunts are created equal. How are you, as the
patient, to know which shunt valve has tested better, is
more reliable, and is best for you? Choose a good
neurosurgeon and trust his recommendations. However, this
does not mean that you have to be in the dark about which
shunt is recommended for you or how it works. Being
informed, able to visualize how the shunt works, and able
to ask questions about it helps many people relax, trust,
and get on with treatment. Your neurosurgeon may have
samples of the shunts he recommends. You can ask to see
models in order to understand how the shunt will operate.
Check with your neurosurgeon to see what type of shunt
will be used (e.g., flow-control, anti-siphoning,
programmable, etc.) and who manufactures it. Although
your neurosurgeon will keep records of the type of shunt
valve you have, knowing this information can be useful
later in case of an emergency.
Shunts can vary by the materials they are made of and
standards they are manufactured under, as well as by
Materials and components
Nearly all shunts used for treating hydrocephalus today
are made out of, or contain, silicone and plastic. Some
shunts are made entirely of silicone and plastic to reduce
the risk of metal components interfering with CT and MRI
equipment, while other shunts contain some non-magnetic
metal components in addition to the silicone and plastic.
Most shunt valves and catheters contain dots or stripes
of barium sulfate, a radiopaque material.
Manufacturing and testing standards
Shunts are manufactured and tested in various ways. Some
shunt manufacturers build their shunts in clean rooms
similar to those used by most computer chip manufacturers.
These clean rooms meet strict international standards for a
sterile, dust-free environment. Unfortunately, not all
shunts are made this way.
Some shunt manufacturers test each and every valve they make
by putting them through a series of rigorous tests. These
tests not only include pressure testing to verify the valves'
pressure, but subjecting shunts to extreme heat and cold,
shock tests, and numerous CT and MRI scans to ensure they
work properly. In these cases, if a shunt valve passes all
of the tests, it is then sterilized and packed for
distribution. If it fails, the shunt valve gets tossed
(as it should). However, some shunt manufacturers only test
a few shunt valves from a specific batch, or may only
pressure test them prior to sterilization. Again, trust
your neurosurgeon to use shunts that are produced by a
manufacturer who adheres to strict production and testing
Shunt valves share many common features. For instance,
most shunt valves and catheters are equipped with a
radiopaque material, usually barium sulfate, which allows
them to be viewed in the body by X-rays and CT scans.
Most shunt valves include a bulb reservoir so that surgery
doesn't need to be performed to test the shunt system. The
reservoir gives your neurosurgeon access to CSF in the shunt,
enabling him to perform a shunt tap. A shunt tap is done by
inserting a small-gauged needle through the scalp,
penetrating the bulb of the reservoir. By performing a shunt
tap, your neurosurgeon can:
The bulb reservoir is designed to enable small-gauged needles
to be inserted, and this in no way compromises the function
of the shunt valve. However, shunt taps need to be performed
under sterile conditions to reduce the risk of introducing
bacteria directly into the shunt valve.
Remove CSF from the shunt system for analysis.
Inject a radioisotope into the shunt valve to follow and
quantitate the flow of CSF with an isotope camera (gamma
Warning: Do not depress the bulb reservoir of your
shunt. This should only be done by your neurosurgeon.
Improper or unnecessary depression of the bulb reservoir can
overdrain the ventricles or cause an obstruction in the shunt.