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To explore the mechanisms behind altered ICP wave amplitudes, we correlated central aortic blood pressure (BP) and ICP waveform amplitudes (intracranial aortic amplitude correlation) and examined how this correlation relates to ICP wave amplitude levels and systemic hemodynamic parameters.<\/jats:p>\n<\/jats:sec><jats:sec>\n<jats:title>Methods<\/jats:title>\n<jats:p>The study included 29 patients with probable iNPH who underwent continuous multi-hour measurement of ICP, radial artery BP, and systemic hemodynamic parameters. The radial artery BP waveforms were used to estimate central aortic BP waveforms, and the intracranial aortic amplitude correlation was determined over consecutive 4-min periods.<\/jats:p>\n<\/jats:sec><jats:sec>\n<jats:title>Results<\/jats:title>\n<jats:p>The average intracranial aortic amplitude correlation was 0.28\u2009\u00b1\u20090.16 at the group level. In the majority of iNPH patients, the intracranial aortic amplitude correlation was low, while in about 1\/5 patients, the correlation was rather high (average Pearson correlation coefficient <jats:underline>&gt;<\/jats:underline>\u00a00.4). The degree of correlation was hardly influenced by systemic hemodynamic parameters.<\/jats:p>\n<\/jats:sec><jats:sec>\n<jats:title>Conclusions<\/jats:title>\n<jats:p>In about 1\/5 iNPH patients of this study, the intracranial aortic amplitude correlation (IAAC<jats:sub>AORTIC<\/jats:sub>) was rather high (average Pearson correlation coefficient\u00a0<jats:underline>&gt;<\/jats:underline>\u00a00.4), suggesting that cerebrovascular factors to some extent may affect the ICP wave amplitudes in a subset of patients. However, in 14\/19 (74%) iNPH patients with elevated ICP wave amplitudes, the intracranial aortic amplitude correlation was low, indicating that the ICP pulse amplitude in most iNPH patients is independent of central vascular excitation, ergo it is modulated by local cerebrospinal physiology. In support of this assumption, the intracranial aortic amplitude correlation was not related to most systemic hemodynamic variables. An exception was found for a subgroup of the patients with high systemic vascular resistance, where there was a correlation.<\/jats:p>\n<\/jats:sec>","DOI":"10.1007\/s00701-020-04423-5","type":"journal-article","created":{"date-parts":[[2020,6,12]],"date-time":"2020-06-12T21:02:26Z","timestamp":1591995746000},"page":"1803-1813","update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":11,"title":["Mechanisms behind altered pulsatile intracranial pressure in idiopathic normal pressure hydrocephalus: role of vascular pulsatility and systemic hemodynamic variables"],"prefix":"10.1007","volume":"162","author":[{"given":"Karen Brastad","family":"Evensen","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6881-9280","authenticated-orcid":false,"given":"Per Kristian","family":"Eide","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"297","published-online":{"date-parts":[[2020,6,12]]},"reference":[{"key":"4423_CR1","doi-asserted-by":"publisher","first-page":"67","DOI":"10.1007\/s12028-012-9687-z","volume":"17","author":"MJ Aries","year":"2012","unstructured":"Aries MJ, Czosnyka M, Budohoski KP, Kolias AG, Radolovich DK, Lavinio A, Pickard JD, Smielewski P (2012) Continuous monitoring of cerebrovascular reactivity using pulse waveform of intracranial pressure. 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KBE and PKE certify that they have no affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers\u2019 bureaus; membership, employment, consultancies, stock ownership, or other equity interest; and expert testimony or patent-licensing arrangements), or non-financial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) in the subject matter or materials discussed in this manuscript.","order":3,"name":"Ethics","group":{"name":"EthicsHeading","label":"Conflict of interest"}},{"value":"The pressure recordings used in this study were retrieved from a study approved by the Regional Ethical Committee of Health Region South-East in Norway (S-07362b) and by Rikshospitalet (07\/5870). Informed consent was obtained from all individual participants included in the study. All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and\/or national research committee (name of institute\/committee) and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.","order":4,"name":"Ethics","group":{"name":"EthicsHeading","label":"Ethical approval"}}]}}