Practice guideline: Idiopathic normal pressure hydrocephalus: Response to shunting and predictors of response: Report of the Guideline Development, Dissemination, and Implementation Subcommittee of the American Academy of Neurology

Abstract

Objective: We evaluated evidence for utility of shunting in idiopathic normal pressure hydrocephalus (iNPH) and for predictors of shunting effectiveness.

Methods: We identified and classified relevant published studies according to 2004 and 2011 American Academy of Neurology methodology.

Results: Of 21 articles, we identified 3 Class I articles.

Conclusions: Shunting is possibly effective in iNPH (96% chance subjective improvement, 83% chance improvement on timed walk test at 6 months) (3 Class III). Serious adverse event risk was 11% (1 Class III). Predictors of success included elevated Ro (1 Class I, multiple Class II), impaired cerebral blood flow reactivity to acetazolamide (by SPECT) (1 Class I), and positive response to either external lumbar drainage (1 Class III) or repeated lumbar punctures. Age may not be a prognostic factor (1 Class II). Data are insufficient to judge efficacy of radionuclide cisternography or aqueductal flow measurement by MRI.

Recommendations: Clinicians may choose to offer shunting for subjective iNPH symptoms and gait (Level C). Because of significant adverse event risk, risks and benefits should be carefully weighed (Level B). Clinicians should inform patients with iNPH with elevated Ro and their families that they have an increased chance of responding to shunting compared with those without such elevation (Level B). Clinicians may counsel patients with iNPH and their families that (1) positive response to external lumbar drainage or to repeated lumbar punctures increases the chance of response to shunting, and (2) increasing age does not decrease the chance of shunting being successful (both Level C).

Figure 1. Percentage of patients improving with shunting in each of the 10 described studies

Summary of findings of included studies assessing different diagnostic testing modalities: external lumbar drainage (ELD; column 1), tap test (TT; column 2), CSF pulsatility (column 3), CSF infusion tests measuring CSF flow resistance (R_o; columns 4, 5, and 6), aqueductal flow on MRI as measured by flow velocity (Hyper velo; column 7), aqueductal stroke volume (Aq SV; column 8), aqueductal hypervelocity (Aq vel; column 9, defined as ≥25.5), improvement after TT (column 10), and R_o <12 on infusion test (column 11). Each bar reflects the overall percentage of patients in that study judged to have improved after shunting. The horizontal dashed line represents the overall response rate among all studies. In all studies, all patients met clinical and brain imaging criteria for the diagnosis of idiopathic normal pressure hydrocephalus. In columns 1, 2, 3, 4, 5, 7, 10, and 11, patients were selected solely on the basis of these criteria. In columns 6, 8, and 9, patients were additionally required to have a positive TT or CSF infusion test in order to undergo shunting. In the latter studies, substantial numbers of patients in whom the add-on investigational test was negative also responded to shunting. Hence, this figure shows the percentage responding among both test+ and test− individuals.

Figure 2. Receiver operating characteristic curve showing the incremental benefit of each of the discussed modalities

Measure of relative sensitivity and specificity of the different techniques described; studies are as listed in figure 1. Increased CSF pressure elevations in response to arterial pulsations are labeled CSF puls hyper. Results from studies in columns 4, 5, 6, and 11 of figure 1 were combined to provide a pooled assessment of R_o. Results from studies in columns 7, 8, and 9 were combined to provide a pooled assessment of elevated CSF flow by MRI. Results from studies in columns 2 and 10 were combined to provide a pooled assessment of the CSF tap test. ELD = external lumbar drainage.