Treatment (physicians)
The treatment of choice for patients with NPH who show a positive result with external lumbar drainage is placement of a CSF shunt. The typical shunts used are either ventriculoperitoneal or lumboperitoneal. Both flow dependent and pressure dependent varieties have been used with similar success (1). Pressure type valves are more commonly employed, and traditionally these were available with different ratings - high, medium and low pressure (where the pressure rating relates to the pressure range over which the valve opens). 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 valve requires removal of the original shunt, and repositioning of a different one. Revisional procedures such as this should be avoided if possible. Careful and knowledgeable interpretation of CSF dynamic studies can help predict the rating of valve which would best suit the patient; therefore the number of patients requiring a second operation can be reduced. Randomised trials have clearly identified that blind-choice of valves is not a beneficial procedure (2).
Some modern valves are now being made with a variable pressure control which can be adjusted externally using a magnet. In this way the valve opening pressure can be varied without the need for repeat surgery.
The surgical placement of the shunts is a short and relatively simple procedure. The surgical risks of shunt placement include infection, subdural hematoma, CSF leaks, chronic headaches, shunt-blockage with a need for reoperation, plus the standard risks of general anesthesia and operative procedures in an elderly person. These risks amount to no more than 10-13% in published studies (3,4) depending on the skill of the surgeon. In a recent review of our shunt procedures for NPH at MCV Hospitals of Virginia Commonwealth University, we observed a less than 8% complication rate.
References:
(1) Weiner HL. Constantini S. Cohen H. Wisoff JH. Current treatment of normal-pressure hydrocephalus: comparison of flow-regulated and differential-pressure shunt valves. Neurosurgery. 37(5):877-84, 1995 Nov.
(2) Boon AJ. Tans JT. Delwel EJ. Egeler-Peerdeman SM. Hanlo PW. Wurzer HA. Avezaat CJ. de Jong DA. Gooskens RH. Hermans J. Dutch Normal-Pressure Hydrocephalus Study: randomized comparison of low- and medium-pressure shunts. Journal of Neurosurgery. 88(3):490-5, 1998 Mar.
(3) Larsson A. Wikkelso C. Bilting M. Stephensen H. Clinical parameters in 74 consecutive patients shunt operated for normal pressure hydrocephalus. Acta Neurologica Scandinavica. 84(6):475-82, 1991 Dec.
(4) Lund-Johansen M. Svendsen F. Wester K. Shunt failures and complications in adults as related to shunt type, diagnosis, and the experience of the surgeon. Neurosurgery. 35(5):839-44; discussion 844, 1994 Nov.