Magnetic resonance elastography in normal pressure hydrocephalus—a scoping review

Aunan-Diop, Jan Saip; Pedersen, Christian Bonde; Halle, Bo; Jensen, Ulla; Munthe, Sune; Harbo, Fredrik; Johannsson, Bjarni; Poulsen, Frantz Rom

doi:10.1007/s10143-021-01669-0

Cited by 11 publications

(4 citation statements)

References 44 publications

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“…This occurs largely due to the effect of the second law of thermodynamics, ensuring that a concentration gradient will be dissipated due to diffusion, pulsatile The prediction of increased venous pressure in the veins over the cortex but reduced venous pressure around the ventricles, would tend to make the outer brain parenchyma stiffer and the inner brain floppier [68] because the veins act as a hydraulic skeleton. This very finding has been noted in magnetic resonance elastography studies of NPH and is specific to this disease [69]. The modelling of NPH shows an 8% increase in the parenchymal vein size pre-shunt and a reduction in these veins of 29% post-shunt.…”

Section: Hydrocephalus (Fig 2e) Appears To Be An Amalgamation Of the ...supporting

confidence: 71%

A Lumped Parameter Modelling Study of Cerebral Autoregulation in Normal Pressure Hydrocephalus: Does the Brain choose to be Ischemic?

Bateman,

Bateman

2024

Preprint

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Background It is well known that normal pressure hydrocephalus (NPH) is associated with a reduction in cerebral blood flow and, therefore, a relatively ischemic metabolic state. It would be expected that ischemia should exhaust the available autoregulation in an attempt to correct the metabolic imbalance. However, there is some evidence to suggest that although blunted, there is retained autoregulation reserve in NPH. The aim of this study is to model the cerebral autoregulation in NPH to discover a solution to this apparent paradox. Methods A lumped parameter model was developed utilizing the known limits of autoregulation in man obtained from the literature. The model was tested by predicting the cerebral blood volume changes which would be brought about by the changes in the resistance for each segment modeled. NPH and the post shunt state were then modeled using the known constraints provided from the literature. Results The model successfully predicted the cerebral blood volume changes brought about by both increasing and decreasing the cerebral perfusion pressure to the limit of autoregulation. The model suggests that NPH is associated with a balanced increase in resistance within the arterial and venous outflow segments. The arterial segment resistance decreases following shunt insertion, indicating a retained autoregulation reserve existed pre-shunt insertion. Conclusions The model suggests that the cerebral blood flow is actively limited in NPH by arteriolar constriction. This may occur to minimize the rise in ICP by reducing the apparent CSF formation rate.

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Section: Hydrocephalus (Fig 2e) Appears To Be An Amalgamation Of the ...supporting

confidence: 71%

A Lumped Parameter Modelling Study of Cerebral Autoregulation in Normal Pressure Hydrocephalus: Does the Brain choose to be Ischemic?

Bateman,

Bateman

2024

Preprint

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“…Moreover, this pathological conditions might be responsible of neurological disturbances and cerebral damages. Recent research focused on the correlation between hydrocephalus and changes in the elastic behavior (see [12] or the recent review [13]). In [14] a novel method based on ultrasound time-harmonic elastography has been described, in which the quantification of shear wave speed is used as indirect biomarker for elevated ICP.…”

Section: Introductionmentioning

confidence: 99%

Assimilation of magnetic resonance elastography data in an in silico brain model

Galarce¹,

Tabelown²,

Polzehl³

et al. 2022

Preprint

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This paper investigates a data assimilation approach for non-invasive quantification of intracranial pressure from partial displacement data, acquired through magnetic resonance elastography. Data assimilation is based on a parametrized-background data weak methodology, in which the state of the physical system -tissue displacements and pressure fields -is reconstructed from partially available data assuming an underlying poroelastic biomechanics model. For this purpose, a physics-informed manifold is built by sampling the space of parameters describing the tissue model close to their physiological ranges, to simulate the corresponding poroelastic problem, and compute a reduced basis. Displacements and pressure reconstruction is sought in a reduced space after solving a minimization problem that encompasses both the structure of the reduced-order model and the available measurements. The proposed pipeline is validated using synthetic data obtained after simulating the poroelastic mechanics on a physiological brain. The numerical experiments demonstrate that the framework can exhibit accurate joint reconstructions of both displacement and pressure fields. The methodology can be formulated for an arbitrary resolution of available displacement data from pertinent images. It can also inherently handle uncertainty on the physical parameters of the mechanical model by enlarging the physics-informed manifold accordingly. Moreover, the framework can be used to characterize, in silico, biomarkers for pathological conditions, by appropriately training the reduced-order model. A first application for the estimation of ventricular pressure as an indicator of abnormal intracranial pressure is shown in this contribution.

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“…Magnetic resonance elastography (MRE) is an MRI method that allows the biomechanical properties of tissues to be measured by recording and analyzing the propagation of shear waves in the tissue of interest 19 and does not require the use of an exogenous contrast agent. MRE was first used for measuring and staging liver fibrosis and has subsequently been applied to study many other soft tissues such as brain, 20–22 for example, in patients with hydrocephalus 23 . Studies have shown that interactions between the biomechanical properties of cells and the external forces acting on the cells play a key role in regulating cellular functions and influencing growth and aging 24 .…”

mentioning

confidence: 99%

“…MRE was first used for measuring and staging liver fibrosis and has subsequently been applied to study many other soft tissues such as brain, [20][21][22] for example, in patients with hydrocephalus. 23 Studies have shown that interactions between the biomechanical properties of cells and the external forces acting on the cells play a key role in regulating cellular functions and influencing growth and aging. 24 MRE studies of normal brain aging have revealed a linear decline in whole brain viscoelastic properties of about 0.8% per year.…”

mentioning

confidence: 99%

Magnetic Resonance Elastography in the Study of Neurodegenerative Diseases

Feng

Murphy

Hojo

et al. 2023

Magnetic Resonance Imaging

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Neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD) present a major health burden to society. Changes in brain structure and cognition are generally only observed at the late stage of the disease. Although advanced magnetic resonance imaging (MRI) techniques such as diffusion imaging may allow identification of biomarkers at earlier stages of neurodegeneration, early diagnosis is still challenging. Magnetic resonance elastography (MRE) is a noninvasive MRI technique for studying the mechanical properties of tissues by measuring the wave propagation induced in the tissues using a purpose‐built actuator. Here, we present a systematic review of preclinical and clinical studies in which MRE has been applied to study neurodegenerative diseases. Actuator systems for data acquisition, inversion algorithms for data analysis, and sample demographics are described and tissue stiffness measures obtained for the whole brain and internal structures are summarized. A total of six animal studies and eight human studies have been published. The animal studies refer to 123 experimental animals (68 AD and 55 PD) and 121 wild‐type animals, while the human studies refer to 142 patients with neurodegenerative disease (including 56 AD and 17 PD) and 166 controls. The animal studies are consistent in the reporting of decreased stiffness of the hippocampal region in AD mice. However, in terms of disease progression, although consistent decreases in either storage modulus or shear modulus magnitude are reported for whole brain, there is variation in the results reported for the hippocampal region. The clinical studies are consistent in reports of a significant decrease in either whole brain storage modulus or shear modulus magnitude, in both AD and PD and with different brain structures affected in different neurodegenerative diseases. MRE studies of neurodegenerative diseases are still in their infancy, and in future it will be interesting to investigate potential relationships between brain mechanical properties and clinical measures, which may help elucidate the mechanisms underlying onset and progression of neurodegenerative diseases.Evidence Level1.Technical EfficacyStage 2.

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Magnetic resonance elastography in normal pressure hydrocephalus—a scoping review

Cited by 11 publications

References 44 publications

A Lumped Parameter Modelling Study of Cerebral Autoregulation in Normal Pressure Hydrocephalus: Does the Brain choose to be Ischemic?

A Lumped Parameter Modelling Study of Cerebral Autoregulation in Normal Pressure Hydrocephalus: Does the Brain choose to be Ischemic?

Assimilation of magnetic resonance elastography data in an in silico brain model

Magnetic Resonance Elastography in the Study of Neurodegenerative Diseases

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