How Shunts Work: An Exploration

As previously discussed, shunts are valves implanted into the brain through a craniotomy to relieve intracranial pressure by means of pumping out excess CSF. They are especially useful, for those reasons, when treating hydrocephalus. The valve is usually planted outside the skull, but underneath the skin, somewhere behind the patient's ear, and the tube that relieves the brain of the fluid is threaded underneath the patient's skin down to the stomach where the CSF can then be best absorbed.

Shunts look like the following (as seen in a previous article): 

 

Shunts have five pressure level settings: .5, 1, 1.5, 2, and 2.5. The various settings allow the surgeon to adjust the degree of CSF drainage after insertion without having to re-operate on the patient to place a new shunt with a new higher or lower pressure valve. The higher the setting, the less CSF is drained from the ventricles. Rather, shunts, or the rotary spring mechanism within them, can be adjusted by the use of a magnet since the valve itself is programmed magnetically. Whenever patients undergo an MRI scan, or anything of the sort, the shunt must be reprogrammed by the original surgeon since the magnetic field generated by the MRI would disrupt the shunt's original settings.

http://www.neurosurgery.pitt.edu/cerebrovascular/endovascular/treatments/nph.html

Possible complications to shunt insertion include infection (since the shunt is a foreign body), shunt blockage, chiari malformation, over drainage and hematomas (brain bleeds). Shunt removal is a very rare procedure. Most patients that require shunts need them for the entirety of their lives, even children. CSF over production does not repair itself, after all.