Utility of preoperative magnetic resonance imaging features for predicting postoperative outcomes in patients with idiopathic normal pressure hydrocephalus

Objective: We investigated associations between postoperative outcomes and clinical characteristics and magnetic resonance imaging (MRI) findings, including disproportionately enlarged subarachnoid space hydrocephalus (DESH) features, in patients with idiopathic normal pressure hydrocephalus (iNPH). We also evaluated the usefulness of these features for predicting outcomes compared with the cerebrospinal fluid (CSF) tap test.Methods: This retrospective cohort study included 36 patients with iNPH who underwent ventriculoperitoneal shunt surgery. Clinical outcomes were assessed from changes in modified Rankin Scale scores at least 1 year after surgery. Cognitive function was evaluated using the Mini-Mental State Examination, and gait function was assessed using the 8-m walk test. Preoperative MRI findings were quantified using the DESH score.Results: Overall, 28 patients (77.8%) were classified as responders and 8 (22.2%) as nonresponders. Baseline clinical characteristics, the Evans index, and mean DESH scores did not differ significantly between the groups. A positive CSF tap test response (≥10% gait improvement) was significantly more frequent among responders than among nonresponders (57.1% vs. 12.5%; p=0.044). In multivariable regression, the DESH score was not independently associated with outcomes (p=0.885), whereas a positive tap test response showed a strong trend toward an association (p=0.078).Conclusion: This study demonstrated the role of the DESH features as noninvasive diagnostic factors for iNPH. However, their value in predicting treatment response could not be established in comparison with the CSF tap test. Further studies are needed to develop noninvasive predictors of treatment efficacy in iNPH.