Most Common Causes Of Shunt Malfunction:

The most common causes of a person's shunt not working optimally are mechanical complications (shunt hardware malfunction), over drainage or under drainage of the cerebral spinal fluid (CSF), bleeding and infection.

What Is A Mechanical Complication?

illustration of the 3 parts of a shunt

All shunts have three basic parts: a Ventricular Catheter, a Shunt Valve and a Distal Catheter. Any of these parts may develop sub-optimal or incomplete function. (For a more detailed explanation of a shunt, see What is a Shunt?) If you look at the ventricular catheter closely, there are tiny holes in it which can become obstructed with tissue growing into the holes. This results in obstruction of CSF flow. Some tissue debris may flow into the valve and obstruct flow as well. The valve is a mechanical device and it is subject to malfunction just like any other mechanical device. Finally, the distal catheter end may become obstructed by tissue. It may also migrate out of its cavity due to movement of the surrounding tissue environment (lungs, heart, bowel...). For more details see Complications under the surgery section.

In general, when a patient 's shunt is not working properly, they will develop the same or similar complaints that they had prior to having the shunt. If the person had poor memory, headaches, nausea, then these symptoms return. Family members will usually notice these problems before health care providers can since, initially, they can be intermittent and very subtle. When they start to occur, keep a written log and bring it with you when you see your physician or health care provider.

Symptoms of Over-Drainage or Under-Drainage of a Shunt:

CT showing early subdural collection from overdrainage of a shunt

There are many types of shunts with many different settings. It can be quite complicated to determine the optimal setting for a particular shunt in a particular patient. Shunts may drain too much fluid or too little fluid. If they drain too little, the patient suffers with the hydrocephalus symptoms that person had initially to various degrees. If the shunt drains too much CSF, the patient may develop "spinal headaches". These are headaches which occur when the patient is sitting up, or moving about and resolve fairly quickly when the patient lies flat. Over drainage of shunts can lead to subdural collections of blood or cerebral spinal fluid along the surface of the brain as discussed in Complications.

Symptoms and Signs of A Shunt Infection:

brain covering call meninges, normally clear, here it is cloudy due to infection

Shunts can become infected at the time of surgery or via the body fluids such as the circulating blood stream. Infections can be very serious and can lead to strokes, paralysis, or even death. Many times the shunt will stop flowing due to debris from the infection. One may see redness or swelling along the skin following the path of the shunt. If the abdominal end becomes infected one may develop peritonitis with severe abdominal pain and fever. If the brain end becomes infected, an infection of the brain can lead to meningitis as depicted on the left. The patient may present with fever, confusion, headache, a stiff neck, some or all of these.