BACKGROUND Idiopathic normal pressure hydrocephalus (iNPH) shares clinical and radiological features with progressive supranuclear palsy (PSP) and Alzheimer's disease (AD). Corpus callosum (CC) involvement in these disorders is well established on structural MRI and diffusion tensor imaging (DTI), but alterations overlap and lack specificity to underlying tissue changes. OBJECTIVE We propose a semi-automated approach to assess CC integrity in iNPH based on the spatial distribution of DTI-derived principal diffusion direction orientation (V1). METHODS We processed DTI data from 121 subjects (Site1: iNPH = 23, PSP = 27, controls = 14; ADNI: AD = 35, controls = 22) to obtain V1, fractional anisotropy (FA) and mean diffusivity (MD) maps. To increase the estimation accuracy of DTI metrics, analyses were restricted to the midsagittal CC portion (± 6 slices from midsagittal plane). Group-wise comparison of normalized altered voxel count in midsagittal CC was performed using Kruskal-Wallis tests, followed by post hoc comparisons (Bonferroni-corrected p < 0.05). ROC analysis was used to evaluate the diagnostic power of DTI alterations compared to callosal volume. RESULTS We found specific changes of V1 distribution in CC splenium of iNPH compared to AD and PSP, while MD and FA showed patterns of alterations common to all disorders. ROC curves showed that, compared to splenial volume, V1 represented the most accurate marker of iNPH diagnosis versus AD and PSP. CONCLUSIONS Our results provide evidence that V1 is a powerful biomarker for distinguishing patients with iNPH from patients with AD or PSP. Indeed, our findings also provide more specific insight into the pathophysiological mechanisms that underlie tissue damage across iNPH and its mimics.

中文翻译：

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胼胝体主要扩散方向的半自动评估：特发性正常压力脑积水与神经退行性疾病的鉴别。

背景 特发性正常压力脑积水 (iNPH) 与进行性核上性麻痹 (PSP) 和阿尔茨海默病 (AD) 具有共同的临床和放射学特征。这些疾病的胼胝体 (CC) 参与在结构 MRI 和弥散张量成像 (DTI) 上得到了很好的证实，但改变重叠并且缺乏对潜在组织变化的特异性。目标 我们提出了一种基于 DTI 派生的主扩散方向方向 (V1) 的空间分布来评估 iNPH 中 CC 完整性的半自动方法。方法 我们处理了来自 121 名受试者的 DTI 数据（站点 1：iNPH = 23，PSP = 27，对照 = 14；ADNI：AD = 35，对照 = 22）以获得 V1、分数各向异性 (FA) 和平均扩散率 (MD) 图。为了提高 DTI 指标的估计精度，分析仅限于中矢状 CC 部分（距中矢状平面 ± 6 片）。使用 Kruskal-Wallis 检验对中矢状 CC 中标准化改变的体素计数进行分组比较，然后进行事后比较（Bonferroni 校正 p < 0.05）。ROC 分析用于评估与胼胝体体积相比 DTI 改变的诊断能力。结果 与 AD 和 PSP 相比，我们发现 iNPH 的 CC 压部 V1 分布的特定变化，而 MD 和 FA 显示出所有疾病共有的改变模式。ROC 曲线显示，与脾体积相比，V1 是 iNPH 诊断与 AD 和 PSP 最准确的标志物。结论 我们的结果提供了证据，证明 V1 是区分 iNPH 患者与 AD 或 PSP 患者的有力生物标志物。确实，