Treatment of Normal Pressure Hydrocephalus

Treatment of Normal Pressure Hydrocephalus

The treatment of choice for NPH patients who show a positive response to diagnostic testing is the placement of a CSF shunt A shunt is an implantable device designed to drain CSF fluid away from the brain thereby allowing the enlarged ventricles to return to a normal state. As CSF fluid builds and the pressure in the ventricle increases, a one-way shunt in the shunt opens, and the excess CSF fluid drains into the abdomen where it is easily absorbed. This technique is very effective in improving the troubling symptoms of NPH.

With a traditional fixed pressure shunt, choice of the correct pressure setting is very important as under-drainage will not improve symptoms, whereas over-drainage can cause symptoms in itself, or predispose to problems such as subdural hematoma. Incorrect choice of a fixed pressure shunt requires removal of the original shunt, and repositioning of a different one.

Surgical revisions such as this can be avoided if your neurosurgeon is certified in the use of programmable shunt technology. With a programmable shunt, the pressure setting can be adjusted with a special magnetic programmer in your doctor's office, eliminating the need for additional surgery if the initial setting proves not to help.

What is a Shunt?

Shunt systems come in a variety of models but always have two similar components: a catheter, the tubing that transports and diverts the CSF from the ventricles to either the abdominal cavity or right atrium, and a shunt that regulates the pressure or flow of CSF from the ventricles. Valves are manufactured to operate at a specific pressure range. A surgeon chooses a pressure range for the shunt based on experience and the needs of the patient.

Many shunt systems also have a flexible flushing chamber called a reservoir. The reservoir may be housed within the shunt system or added as a component along with the shunt system. The reservoir serves several important functions. It permits the doctor to remove samples of CSF for testing, using a needle and syringe. The doctor also may inject fluid into the shunt system to test for flow; to be sure the system is functioning.

The parts of a shunt system are named according to where they are implanted (placed) in the body. The portion of the tube which is inserted into the ventricles is called the ventricular catheter. The peritoneal catheter is the portion of the tube that drains CSF into the abdominal or peritoneal cavity.

If a drainage tube is placed into the right atrium of the heart it is called the atrial catheter. To get a better understanding of what a shunt system looks like, ask your doctor or nurse to show you samples of the shunts they use. All of the components of a shunt system are made from materials which are well known to be tolerated by the body. For this reason, the entire shunt system is implanted under the skin. There are no external parts.

Codman Programmable Shunt

Use of a programmable shunt can significantly increase the probability of shunt implantation being a one-time procedure. If the pressure setting of a fixed pressure shunt proves to be a mismatch after surgery, causing underdrainage or overdrainage complications, the patient must undergo a complete or partial shunt revision, sometimes more than once. This is a limitation of all fixed pressure shunts.

The CODMAN Programmable Shunt gives your doctor a choice of 18 different programmable pressure settings. It is the same size as traditional fixed pressure shunts and is implanted in exactly the same way. Using an exclusive external programming device, the surgeon selects the initial pressure setting prior to the procedure, and can then easily adjust the setting at any time and as many times as necessary without further surgery. The large range of pressure settings allows the surgeon to make very fine adjustments in the pressure in order to get the best resolution of symptoms after the shunt is implanted. The totally non-invasive adjustments take only seconds and can be done right in the office with little or no patient discomfort.

Programming Device

The device used to adjust the pressure setting of the shunt is simply called a Programmer. The programmer includes an electrical box connected to a round transmitter head. Using the transmitter head, the shunt is programmed to a certain pressure chosen by the surgeon prior to being implanted in the patient. Upon pushing a button, the shunt is changed to the selected pressure in 5 to 10 seconds. No additional surgeries or hospital visits are needed in order to reprogram the shunt.