Abstract
Periventricular white matter changes are common in patients with idiopathic normal pressure hydrocephalus (iNPH) and considered to represent focally elevated interstitial fluid. We compared diffusion measures in periventricular hyperintensities in patients with imaging features of iNPH to patients without. The hypothesis is that periventricular hyperintensities in patients with presumed iNPH show higher water content than in patients without imaging features of iNPH. 21 patients with iNPH Radscale 7–12 (“high probability of iNPH”) and 10 patients with iNPH Radscale 2–4 (“low probability of iNPH”) were examined with a neurodegeneration imaging protocol including a diffusion microstructure imaging sequence. Periventricular hyperintensities and deep white matter hyperintensities were segmented and diffusion measures were compared. In patients with imaging features of iNPH, the free water content in periventricular hyperintensities was significantly higher compared to the control group (p = 0.005). This effect was also detectable in deep white matter hyperintensities (p = 0.024). Total brain volumes and total gray or white matter volumes did not differ between the groups. Periventricular cap free water fraction was highly discriminative regarding patients with presumed iNPH and controls with an ROC AUC of 0.933. Quantitative diffusion microstructure imaging shows elevated water content in periventricular hyperintensities in patients with imaging features of iNPH, which could be the imaging correlate for pathologic fluid accumulation and may be used as an imaging biomarker in the future.
Highlights
Periventricular white matter changes are common in patients with idiopathic normal pressure hydrocephalus and considered to represent focally elevated interstitial fluid
There was no significant difference regarding Periventricular hyperintensities (PVHs) (p = 0.142) and deep white matter hyperintensities (DWMH) volumes (p = 0.990) between groups with imaging features of idiopathic normal pressure hydrocephalus (iNPH) and controls, even though periventricular white matter changes are included in the selection criteria of the iNPH Radscale
No significant correlation between PVH or DWMH volume and PVH/DWMH V-cerebrospinal fluid (CSF) was observed in both groups
Summary
Periventricular white matter changes are common in patients with idiopathic normal pressure hydrocephalus (iNPH) and considered to represent focally elevated interstitial fluid. In patients with imaging features of iNPH, the free water content in periventricular hyperintensities was significantly higher compared to the control group (p = 0.005) This effect was detectable in deep white matter hyperintensities (p = 0.024). Abbreviations CSF Cerebrospinal fluid DMI Diffusion microstructure imaging DWMH Deep white matter hyperintensities FA Fractional anisotropy iNPH Idiopathic normal pressure hydrocephalus PVH Periventricular hyperintensities SVM Support Vector Machine V-CSF Free water/CSF fraction V-extra Extraaxonal volume fraction V-intra Intraaxonal volume fraction. Periventricular hyperintensities (PVHs) are T2-hyperintense white matter areas located around the lateral (mostly frontal and occipital) ventricles, commonly found in standard MRI studies in the older population with and without idiopathic normal pressure hydrocephalus (iNPH)[1] They represent areas of finely textured myelin associated with denudation of the ventricular ependymal lining rather than ischemic or gliotic changes[2]. Though to date, focused evaluation of iNPH-associated T2w hyperintense white matter changes based on current diffusion sequences is missing
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