The most common complications seen in clinical practice are mechanical complications (shunt hardware malfunction), over drainage of CSF fluid, bleeding and infection.
What Is A Mechanical Complication?
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 my become obstructed by tissue. It may also migrate out of its cavity due to movement of the surrounding tissue environment (lungs, heart, bowel...).
This patient developed a progressive swelling under the incision. He had developed an obstruction at the end of the shunt. CSF percolated in the tract around the catheter into the subcutaneous tissues.
What Is Over drainage 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. During this process, 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, or if the particular brain is not compliant enough to expand and remains compressed, an over drainage process occurs. Extra fluid begins to accumulate between the covering of the brain called the dura and the brain itself. A subdural collection begins to form.
These subdural collections may be cerebral spinal fluid. The collection may also result in blood accumulating in this same space resulting in a subdural hematoma.
The pictures below show a subdural hematoma. Notice the blood is in between the dura and the brain. Place your arrow on the picture in the lower left. Click the triangle button to play.