If, as described under Evaluation, external lumbar drainage appears to improve your symptoms, then it is likely that provision of a valve will provide you with longer-term improvement in symptoms.

The valve referred to is more technically called a 'CSF Shunt'. There are two types commonly used, the ventriculoperitoneal and the lumboperitoneal. The principle behind both types of shunt is the same - they are designed to 'shunt' CSF fluid away from the brain, and allow it to drain somewhere else in the body, in these cases the abdomen. If CSF fluid builds up, a one-way valve in the shunt opens, and the excess fluid drains away. Fluid is easily soaked up by the abdomen, and causes no problems at all. In the case of the ventriculoperitoneal shunt, fluid is diverted from the ventricles, or fluid spaces in the brain. In the case of the lumboperitoneal, fluid is shunted away from the spinal cord. Both techniques are very successful in reducing the excess fluid in the brain, and improving the troubling symptoms of NPH.

Shunts vary in terms of their size and also pressure at which their one-way valve opens. Older style shunts were designated with pressure ratings, however newer style shunts have an externally programmable valve which can be adjusted using magnets, without the need for extra surgery if the initial setting proves not to help.

As described previously, evaluation of both the External Lumbar Drainage procedures, and the CSF dynamics tests by experts, yields a much greater success rate of reducing symptoms after shunting. It firstly identifies those patients who can benefit from the procedure, and secondly what type of shunt, and at what setting it should be. As with all plumbing, a small number of shunts sometimes block, and CSF dynamics tests, again in the hands of an experienced assessor, can be invaluable in demonstrating such a blockage.

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Maintained by: Andrew Beaumont MD

Department of Neurosurgery
Updated August 2003, Rev 4.0