CSF then drains from the base of the skull and travels down the spinal column. Just like your brain, your spinal cord "floats" in CSF. From the spinal column, CFS leeches into your body and is absorbed.
In cases of SB, often the brain is seated farther back in the cranium. In addition, there may be an Arnold Chiari II malformation (see "Banana Sign") which blocks the proper draining of CSF. When the CSF cannot properly drain, the pressure begins to build inside the cranium. This condition is called hydrocephalus.
Fortunately, since the bony plates of an infant's cranium have not yet fused together, infants can tolerate a small amount of pressure building up. However the issue needs to be addressed. The most common way of treating hydrocephalus is though the insertion of a shunt.
A shunt consists of three basic parts:
1) Ventricular Catheter: The neurosurgeon will make a small hole in the skull (often behind an ear but not always). Then a small tube is placed through the hole and into the ventricles. This allows the excess CSF to drain out of the cranium
2) Valve and Reservoir: To regulate how much CSF is allowed to drain, a one-way valve is connected to the ventricular catheter. The valve is then attached to the outside of the skull underneath the skin. Non programmable valves come in various sizes and must be physically replaced if it is found that they are releasing too much or too little CSF. Programmable valves do not need to be replaced to make an adjustment in outflow. Instead, programmable valves are adjusted by magnets placed against the skin over the valve.
Along with the valve, will be a small bubble called a reservoir. This allows a small mount of CSF to remain in that bubble before it drains into the distal catheter. The reason being, if a doctor suspects an infection, there is no need for surgery. The doctor can just insert a needle into the reservoir and extract a sample of CSF for testing.
3) Distal Catheter: From the reservoir, a long tube is attached. This tube runs underneath the skin and down to the abdomen where the CSF is absorbed by the body. In the case of children, additional tubing will be coiled in the abdomen to allow for growth.
Here some xrays of Annie's shunt and tubing at 6 months:
Parents Note: Our Annie had her shunt placed two days after she was born. At around 6 months she had a revision as the ventricular catheter had become blocked. It has been 3 years since that last revision and we almost never think about her shunt anymore. Naturally, at the time of her operations were were stressed out however it has now faded into the background of our "new normal".