Alteration of brain viscoelasticity after shunt treatment in normal pressure hydrocephalus

Freimann, Florian Baptist; Streitberger, Kaspar Josche; Klatt, Dieter; Lin, Kui; McLaughlin, Joyce R.; Braun, Jürgen; Sprung, Christian; Sack, Ingolf

doi:10.1007/s00234-011-0871-1

Cited by 102 publications

(102 citation statements)

References 24 publications

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“…Hemodynamic evaluations have already shown a higher cerebral blood flow in patients with iNPH 7,8 . Another theoretical statement is the linkage between perfusion and function, but also depending in increasing complexity of the neural network after shunting [9][10][11] .…”

mentioning

confidence: 99%

Programmable valve represents an efficient and safe tool in the treatment of idiopathic normal-pressure hydrocephalus patients

Oliveira

Saad

Reis

et al. 2013

Arq. Neuro-Psiquiatr.

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Idiopathic normal pressure hydrocephalus (iNPH) is a condition characterized by gait disturbance, dementia and/or urinary incontinence without causative disorders, as well as dilation of ventricular system due to disturbance of cerebrospinal fluid (CSF) circulation with normal CSF pressure and no secondary cause [1][2][3] . It is a differential diagnosis for most of the dementia syndromes and occurs mainly in elderly populations 4 .The known incidence is approximately 6 per 100,000 and it has a prevalence of 22 per 100,000 for suspected iNPH.There are associations with hypertension, cerebrovascular and Alzheimer diseases [1][2][3] .The clinical evolution of iNPH is not clear 5 . Without surgery, most iNPH patients present early clinical deterioration. A small number of patients might improve without shunting; however, the extent of improvement is not clear 3 .Ventricular CSF shunting is the main treatment in the management of iNPH and its results in reducing the caregiver's burden when caring for iNPH patients are well-established 6 . ABSTRACTIdiopathic normal pressure hydrocephalus (iNPH) is characterized by gait disturbance, dementia and /or urinary incontinence, dilation of the ventricular system and normal opening cerebrospinal fluid pressure. Shunt surgery is the standard treatment of iNHP. Diversions with programmable valves are recommended, once drainage pressure can be changed. However, well-defined protocols still lack guiding the steps to attain proper pressure for each patient. Methods: In our study, we reported the experience of shunting 24 patients with iNPH using Strata ® (Medtronic) valve, following a protocol based on a positive Tap Test. Results: We observed clinical improvement in 20 patients and stability/ worsening in 4 patients. Complications occurred in five patients, including one death. The results display improvement, and complications occurred at a lower rate than reported in other studies. Conclusions: The Strata ® valve used in the proposed protocol represents an efficient and safe tool in the treatment of iNPH.Key words: hydrocephalus, normal pressure, cerebrospinal fluid shunts, treatment. RESUMOA hidrocefalia de pressão normal idiopática (iNPH) é caracterizada por alterações na marcha, demência e/ou incontinência urinária, além de dilatação dos ventrículos com pressão normal de abertura no líquido cefalorraquidiano. A cirurgia de derivação é o principal tratamento da iNHP. São recomendadas válvulas programáveis, pois a pressão de drenagem pode ser alterada. Embora as válvulas programáveis sejam utilizadas, não há protocolos para atingir a pressão adequada de cada paciente. Métodos: Neste estudo, relatamos nossa experiência com 24 pacientes com iNPH que usaram a válvula Strata ® (Medtronic), seguindo protocolo baseado em um Tap test positivo. Resultados: Observamos melhora em 20 pacientes e estabilidade ou piora em 4. Ocorreram complicações em cinco pacientes, tendo um deles falecido. Houve importante melhora clínica, e as complicações ocorreram em taxa mais baixa do que as relatad...

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mentioning

confidence: 99%

Programmable valve represents an efficient and safe tool in the treatment of idiopathic normal-pressure hydrocephalus patients

Oliveira

Saad

Reis

et al. 2013

Arq. Neuro-Psiquiatr.

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“…[117][118][119] In these soft tissues, the macroscopic mechanical behavior (stiffness) has highly correlated changes in the tissue composition and structure identified by histology on a microscopic scale. Therefore, it is reasonable to expect that changes in the structure and composition of engineered cartilage during growth will alter the MRE-derived stiffness.…”

Section: Magnetic Resonance Elastographymentioning

confidence: 99%

Monitoring Cartilage Tissue Engineering Using Magnetic Resonance Spectroscopy, Imaging, and Elastography

Kotecha

Klatt

Magin

2013

Tissue Engineering Part B: Reviews

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A key technical challenge in cartilage tissue engineering is the development of a noninvasive method for monitoring the composition, structure, and function of the tissue at different growth stages. Due to its noninvasive, three-dimensional imaging capabilities and the breadth of available contrast mechanisms, magnetic resonance imaging (MRI) techniques can be expected to play a leading role in assessing engineered cartilage. In this review, we describe the new MR-based tools (spectroscopy, imaging, and elastography) that can provide quantitative biomarkers for cartilage tissue development both in vitro and in vivo. Magnetic resonance spectroscopy can identify the changing molecular structure and alternations in the conformation of major macromolecules (collagen and proteoglycans) using parameters such as chemical shift, relaxation rates, and magnetic spin couplings. MRI provides high-resolution images whose contrast reflects developing tissue microstructure and porosity through changes in local relaxation times and the apparent diffusion coefficient. Magnetic resonance elastography uses low-frequency mechanical vibrations in conjunction with MRI to measure soft tissue mechanical properties (shear modulus and viscosity). When combined, these three techniques provide a noninvasive, multiscale window for characterizing cartilage tissue growth at all stages of tissue development, from the initial cell seeding of scaffolds to the development of the extracellular matrix during construct incubation, and finally, to the postimplantation assessment of tissue integration in animals and patients.

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“…3 and 5). Viscoelastic behavior of brain tissue has been reported in a number of studies, 8,9,13,20,24,26,29 but standard methods for calculating the R 0 do not take viscoelasticity into account. Taken together, these observations support our hypothesis that the clinically observed underestimation of R 0 is due to methods that do not account for the viscoelasticity of the brain.…”

Section: Possible Causes Of Underestimation Of the Rmentioning

confidence: 99%

“…13,18,26 Chang es of viscoelastic properties in hydrocephalic patients have been characterized by the latter method both before and after shunting. 9 On the basis of these data, we hypothesized that viscoelasticity plays a role in the ICP response and that neglecting the contributions of viscoelastic behavior is re sponsible for, or substantially contributes to, the underesti mation of the R 0 by the bolus infusion method.…”

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confidence: 99%

Assessment of intracranial dynamics in hydrocephalus: effects of viscoelasticity on the outcome of infusion tests

Bottan

Daners

Zélicourt

et al. 2013

JNS

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Object The treatment of hydrocephalus requires insight into the intracranial dynamics in the patient. Resistance to CSF outflow (R0) is a clinically obtainable parameter of intracranial fluid dynamics that quantifies the apparent resistance to CSF absorption. It is used as a criterion for the selection of shunt candidates and serves as an indicator of shunt performance. The R0 is obtained clinically by performing 1 of 3 infusion tests: constant flow, constant pressure, or bolus infusion. Among these, the bolus infusion method has the shortest examination times and provides the shortest time of exposure of patients to artificially increased intracranial pressure (ICP) levels. However, for unknown reasons, the bolus infusion method systematically underestimates the R0. Here, the authors have tested and verified the hypothesis that this underestimation is due to lack of accounting for viscoelasticity of the craniospinal space in the calculation of the R0. Methods The authors developed a phantom model of the human craniospinal space in order to reproduce in vivo pressure-volume (PV) relationships during infusion testing. The phantom model followed the Marmarou exponential PV equation and also included a viscoelastic response to volume changes. Parameters of intracranial fluid dynamics, such as the R0, could be controlled and set independently. In addition to the phantom model, the authors designed a computational framework for virtual infusion testing in which viscoelasticity can be turned on or off in a controlled manner. Constant flow, constant pressure, and bolus infusion tests were performed on the phantom model, as well as on the virtual computational platform, using standard clinical protocols. Values for the R0 were derived from each infusion test by using both a standard method based on the Marmarou PV equation and a novel method based on a system identification approach that takes into account viscoelastic behavior. Results Experiments with the phantom model confirmed clinical observations that both the constant flow and constant pressure infusion tests, but not the bolus infusion test, yield correct R0 values when they are determined with the standard method according to Marmarou. Equivalent results were obtained using the computational framework. When the novel system identification approach was used to determine the R0, all of the 3 infusion tests yielded correct values for the R0. Conclusions The authors' investigations demonstrate that intracranial dynamics have a substantial viscoelastic component. When this viscoelastic component is taken into account in calculations, the R0, is no longer underestimated in the bolus infusion test.

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Alteration of brain viscoelasticity after shunt treatment in normal pressure hydrocephalus

Cited by 102 publications

References 24 publications

Programmable valve represents an efficient and safe tool in the treatment of idiopathic normal-pressure hydrocephalus patients

Programmable valve represents an efficient and safe tool in the treatment of idiopathic normal-pressure hydrocephalus patients

Monitoring Cartilage Tissue Engineering Using Magnetic Resonance Spectroscopy, Imaging, and Elastography

Assessment of intracranial dynamics in hydrocephalus: effects of viscoelasticity on the outcome of infusion tests

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