Placement of cerebral spinal fluid (CSF) shunt systems to treat hydrocephalus is a common medical procedure and a life-saving treatment for many patients. These shunt systems drain excess fluid from the brain to another part of the body where the fluid is absorbed as part of the circulatory process. CSF shunts contain three main components: an in-flow tube (catheter), a valve that regulates the flow of fluid, and an outflow catheter that carries the fluid to the abdomen or the heart where the fluid can be absorbed.
Figure 1 below shows a side view of an implanted CSF shunt system.
Figure 1: Side-view of implanted CSF shunt system.
Types of CSF Shunt Valves
There are two types of CSF shunt valves: fixed and adjustable. Fixed shunt valves allow CSF fluid to drain when CSF pressure exceeds a certain “fixed” threshold. Adjustable shunt valves allow for changes to the amount of fluid that flows through the valve. There are two types of adjustable CSF shunt valves: magnetic externally adjustable and non-magnetic externally adjustable.
Magnetic Externally Adjustable Shunt Valves
Magnetic externally adjustable shunts have mechanical parts that can be moved non-invasively from outside the body. To adjust these valves, a clinician places a magnetic tool on the skin near the valve and manually rotates it. The magnetic field of the programming tool passes through the skin to adjust the position of the valve. This process, setting a valve to drain more or less fluid from the brain, is sometimes called “programming,” although the process involves no electronics. Once implanted, no additional surgical procedures are required to change the setting of a magnetic externally adjustable shunt valve.
Non-Magnetic Externally Adjustable Valves
These types of shunts DO NOT use an external magnetic field for valve adjustments. Some valves have self-adjusting flow-regulating mechanisms, while others can only be adjusted using minimally invasive surgical procedures.