Surgical management of idiopathic normal-pressure hydrocephalus

To develop evidence-based guidelines for surgical management of idiopathic normal-pressure hydrocephalus (INPH). Compared with the diagnostic phase, the surgical management of INPH has received less scientific attention. The quality of much of the literature concerning the surgical management has been limited by many factors. These include retrospective analysis, small patient numbers, analysis of a mixed NPH population, and sometimes a lack of detail as to what type of shunt system was used. Many earlier studies predated our current understanding of the hydrodynamics of cerebrospinal fluid shunts, and therefore, the conclusions drawn may no longer be valid.

A MEDLINE and PubMed search from 1966 to the present was conducted using the following key terms: normal-pressure hydrocephalus and idiopathic adult-onset hydrocephalus. Only English-language literature in peer-reviewed journals was reviewed. The search was further limited to articles that described the method of treatment and outcome selectively for INPH patients. Finally, only studies that included 20 or more INPH patients were considered with respect to formulating the recommendations in these Guidelines (27 articles).

For practical reasons, it is important to identify probable shunt responders diagnosed with INPH. If the patient is an acceptable candidate for anesthesia, then an INPH-specific risk-benefit analysis should be determined. In general, patients exhibiting negligible symptoms may not be suitable candidates for surgical management, given the known risks and complications associated with shunting INPH. The choice of valve type and setting should be based on empirical reasoning and a basic understanding of shunt hydrodynamics. The most conservative choice is a valve incorporating an antisiphon device, with the understanding that underdrainage (despite a low opening pressure) may occur in a small percentage of patients because of the antisiphon device. On the basis of retrospective studies, the use of an adjustable valve seems to be beneficial in the management of INPH.

The treatment of INPH should not be considered lightly, given the seriousness of the potential complications. Within these limitations and the available evidence, guidelines for surgical management were developed.