Department of Behavioral Neurology and Cognitive Neuroscience, Tohoku University Graduate School of Medicine, 2-1, Seiryo-machi, Aoba-ku, Miyagi, 980-8575, Sendai, Japan.
Department of Neurology, South Miyagi Medical Center, Shibata, Japan.
BMC Neurol. 2021 Sep 13;21(1):353. doi: 10.1186/s12883-021-02389-0.
The aim of this study was to investigate whether default mode network (DMN) connectivity and brain white matter integrity at baseline were associated with severe cognitive impairments at baseline and poor cognitive outcomes after shunt placement in patients with idiopathic normal pressure hydrocephalus (iNPH).
Twenty consecutive patients with iNPH whose symptoms were followed for 6 months after shunt placement and 10 healthy controls (HCs) were enrolled. DMN connectivity and brain white matter integrity at baseline in the patients with iNPH and HCs were detected by using resting-state functional magnetic resonance imaging (MRI) with independent component analysis and diffusion tensor imaging, respectively, and these MRI indexes were compared between the patients with iNPH and HCs. Performance on neuropsychological tests for memory and executive function and on the gait test was assessed in the patients with iNPH at baseline and 6 months after shunt placement. We divided the patients with iNPH into the relatively preserved and reduced DMN connectivity groups using the MRI indexes for DMN connectivity and brain white matter integrity, and the clinical measures were compared between the relatively preserved and reduced DMN connectivity groups.
Mean DMN connectivity in the iNPH group was significantly lower than that in the HC group and was significantly positively correlated with Rey auditory verbal learning test (RAVLT) immediate recall scores and frontal assessment battery (FAB) scores. Mean fractional anisotropy of the whole-brain white matter skeleton in the iNPH group was significantly lower than that in the HC group. The reduced DMN connectivity group showed significantly worse performance on the RAVLT at baseline and significantly worse improvement in the RAVLT immediate recall and recognition scores and the FAB scores than the preserved DMN connectivity group. Moreover, the RAVLT recognition score highly discriminated patients with relatively preserved DMN connectivity from those with relatively reduced DMN connectivity.
Our findings indicated that iNPH patients with reduced DMN connectivity relative to the severity of brain white matter disruption have severe memory deficits at baseline and poorer cognitive outcomes after shunt placement. However, further larger-scale studies are needed to confirm these findings.
本研究旨在探讨特发性正常压力脑积水（iNPH）患者基线时默认模式网络（DMN）连接和脑白质完整性是否与基线时严重认知障碍以及分流术后认知结局不良相关。
连续纳入 20 例 iNPH 患者，对其分流术后 6 个月的症状进行随访，并纳入 10 例健康对照者（HCs）。采用静息态功能磁共振成像（rs-fMRI）的独立成分分析（ICA）检测 iNPH 患者和 HCs 的 DMN 连接，采用弥散张量成像（DTI）检测其脑白质完整性，比较 iNPH 患者和 HCs 的这些 MRI 指标。在基线和分流术后 6 个月对 iNPH 患者进行记忆和执行功能神经心理学测试以及步态测试。采用 DMN 连接和脑白质完整性的 MRI 指标将 iNPH 患者分为 DMN 连接相对保留和降低的两组，并比较两组间的临床指标。
iNPH 组的平均 DMN 连接显著低于 HCs 组，且与 Rey 听觉言语学习测试（RAVLT）即时回忆评分和额叶评估量表（FAB）评分显著正相关。iNPH 组的全脑白质骨架分数各向异性值显著低于 HCs 组。基线时，DMN 连接降低组的 RAVLT 表现明显更差，且 RAVLT 即时回忆和识别评分以及 FAB 评分的改善明显更差。此外，RAVLT 识别评分可高度区分 DMN 连接相对保留和降低的患者。
本研究结果表明，与脑白质破坏程度相比，iNPH 患者的 DMN 连接降低提示其基线时记忆障碍严重，分流术后认知结局不良。但仍需进一步的大规模研究来证实这些发现。
