Idiopathic normal pressure hydrocephalus (iNPH) and late-onset idiopathic aqueductal stenosis (LIAS) are two forms of chronic adult hydrocephalus of different aetiology. We analysed overnight intracranial pressure (ICP) monitoring to elucidate ICP waveform changes characteristic for iNPH and LIAS to better understand pathophysiological processes of both diseases. 98 patients with iNPH and 14 patients with LIAS from two neurosurgical centres were included. All patients underwent diagnostic overnight computerised ICP monitoring with calculation of mean ICP, ICP heartbeat related pulse wave amplitude calculated in the frequency domain (AMP) and the time domain (MWA), index of cerebrospinal compensatory reserve (RAP) and power of slow vasogenic waves (SLOW). ICP was higher in LIAS than iNPH patients (9.3 ± 3.0 mmHg versus 5.4 ± 4.2 mmHg, p = 0.001). AMP and MWA were higher in iNPH versus LIAS (2.36 ± 0.91 mmHg versus 1.81 ± 0.59 mmHg for AMP, p = 0.012; 6.0 ± 2.0 mmHg versus 4.9 ± 1.2 mmHg for MWA, p = 0.049). RAP and SLOW indicated impaired reserve capacity and compliance in both diseases, but did not differ between groups. INPH patients were older than LIAS patients (77 ± 6 years versus 54 ± 14 years, p < 0.001). ICP is higher in LIAS than in iNPH patients, likely due to the chronically obstructed CSF flow through the aqueduct, but still in a range considered normal. Interestingly, AMP/MWA was higher in iNPH patients, suggesting a possible role of high ICP pulse pressure amplitudes in iNPH pathophysiology. Cerebrospinal reserve capacity and intracranial compliance is impaired in both groups and the pressure-volume relationship might be shifted towards lower ICP values in iNPH. The physiological influence of age on ICP and AMP/MWA requires further research.

中文翻译：

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特发性正常压力脑积水和迟发性特发性导水管狭窄的颅内压波形特征

特发性正常压力脑积水 (iNPH) 和迟发性特发性导水管狭窄 (LIAS) 是两种病因不同的慢性成人脑积水。我们分析了夜间颅内压 (ICP) 监测，以阐明 iNPH 和 LIAS 的 ICP 波形变化特征，以更好地了解这两种疾病的病理生理过程。包括来自两个神经外科中心的 98 名 iNPH 患者和 14 名 LIAS 患者。所有患者均接受诊断性夜间计算机化 ICP 监测，计算平均 ICP、在频域 (AMP) 和时域 (MWA) 中计算的 ICP 心跳相关脉搏波幅度、脑脊髓代偿储备指数 (RAP) 和慢血管生成波功率（慢的）。LIAS 患者的 ICP 高于 iNPH 患者（9.3 ± 3.0 mmHg vs 5.4 ± 4.2 mmHg，p = 0.001）。AMP 和 MWA 在 iNPH 与 LIAS 中更高（AMP 为 2.36 ± 0.91 mmHg，AMP 为 1.81 ± 0.59 mmHg，p = 0.012；6.0 ± 2.0 mmHg 与 MWA 的 4.9 ± 1.2 mmHg，p = 0.049）。RAP 和 SLOW 表明两种疾病的储备能力和依从性受损，但组间没有差异。INPH 患者比 LIAS 患者年龄大（77 ± 6 岁 vs 54 ± 14 岁，p <0.001）。LIAS 患者的 ICP 高于 iNPH 患者，这可能是由于脑脊液流经导水管的慢性阻塞所致，但仍处于正常范围内。有趣的是，iNPH 患者的 AMP/MWA 较高，表明高 ICP 脉压幅度可能在 iNPH 病理生理学中起作用。两组的脑脊髓储备能力和颅内顺应性均受损，iNPH 中的压力-容积关系可能会向较低的 ICP 值转移。