Diffusion Tensor Imaging helps identify shunt-responsive Normal Pressure Hydrocephalus patients amongst probable iNPH cohort

Abstract

Objectives The aim of this study was to investigate whether white matter changes as measured by Diffusion Tensor Imaging (DTI) can help differentiate shunt-responsive idiopathic normal pressure hydrocephalus (iNPH) patients from patients with other causes of gait disturbances and/or cognitive decline with ventriculomegaly whose clinical symptoms do not improve significantly after cerebrospinal fluid derivation (non-iNPH). Methods Between 2017 and 2022, 85 patients with probable iNPH underwent prospective preoperative magnetic resonance imaging (MRI) and comprehensive clinical workup. Patients with clinical symptoms of iNPH, positive result on lumbar infusion test and gait improvement after 120-hour lumbar drainage were diagnosed with iNPH and underwent shunt-placement surgery. Fractional anisotropy (FA) and mean diffusivity (MD) values for individual regions of interest were extracted from preoperative MRI, using the TBSS pipeline of FSL toolkit. These FA and MD values were then compared to results of clinical workup and established diagnosis of iNPH. An identical MRI protocol was performed on 13 age- and sex-matched healthy volunteers. Results Statistically significant differences in FA values of several white matter structures were found not only between iNPH patients and healthy controls, but also between iNPH and non-iNPH patients. ROI that showed best diagnostic ability when differentiating iNPH amongst probable iNPH cohort was uncinate fasciculus, with AUC of 0.74 (p < 0.001). Conclusion DTI methods of white matter analysis using standardised methods of ROI extraction can help in differentiation of iNPH patients not only from healthy patients, but also from patients with other causes of gait disturbances with cognitive decline and ventriculomegaly.