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Szabo S, Totka Z, Nagy-Bozsoky J, Pinter I, Bagany M, Bodo M. Rheoencephalography: A non-invasive method for neuromonitoring. JOURNAL OF ELECTRICAL BIOIMPEDANCE 2024; 15:10-25. [PMID: 38482467 PMCID: PMC10936697 DOI: 10.2478/joeb-2024-0003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Indexed: 04/07/2024]
Abstract
In neurocritical care, the gold standard method is intracranial pressure (ICP) monitoring for the patient's lifesaving. Since it is an invasive method, it is desirable to use an alternative, noninvasive technique. The computerized real-time invasive cerebral blood flow (CBF) autoregulation (AR) monitoring calculates the status of CBF AR, called the pressure reactivity index (PRx). Studies documented that the electrical impedance of the head (Rheoencephalography - REG) can detect the status of CBF AR (REGx) and ICP noninvasively. We aimed to test REG to reflect ICP and CBF AR. For nineteen healthy subjects we recorded bipolar bifrontal and bitemporal REG derivations and arm bioimpedance pulses with a 200 Hz sampling rate. The challenges were a 30-second breath-holding and head-down-tilt (HDT - Trendelenburg) position. Data were stored and processed offline. REG pulse wave morphology and REGx were calculated. The most relevant finding was the significant morphological change of the REG pulse waveform (2nd peak increase) during the HDT position. Breath-holding caused REG amplitude increase, but it was not significant. REGx in male and female group averages have similar trends during HDT by indicating the active status of CBF AR. The morphological change of REG pulse wave during HDT position was identical to ICP waveform change during increased ICP, reflecting decreased intracranial compliance. A correlation study between ICP and REG was initiated in neurocritical care patients. The noninvasive REG monitoring would also be useful in space research as well as in military medicine during the transport of wounded service members as well as for fighter pilots to indicate the loss of CBF and consciousness.
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Affiliation(s)
- Sandor Szabo
- University of Szeged, Faculty of General Medicine, Department of Aviation and Space Medicine. Kecskemet, Hungary; Hungarian Defence Forces Medical Center, Aeromedical, Military Medical Screening and Healthcare Instituter;Kecskemet, Hungary
| | - Zsolt Totka
- University of Szeged, Faculty of General Medicine, Department of Aviation and Space Medicine. Kecskemet, Hungary; Hungarian Defence Forces Medical Center, Aeromedical, Military Medical Screening and Healthcare Instituter;Kecskemet, Hungary
| | - Jozsef Nagy-Bozsoky
- University of Szeged, Faculty of General Medicine, Department of Aviation and Space Medicine. Kecskemet, Hungary; Hungarian Defence Forces Medical Center, Aeromedical, Military Medical Screening and Healthcare Instituter;Kecskemet, Hungary
| | | | | | - Michael Bodo
- Uniformed Services University of the Health Sciences, Bethesda, MD, USA
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Sayin ES, Davidian A, Levine H, Venkatraghavan L, Mikulis DJ, Fisher JA, Sobczyk O, Duffin J. Does breathing pattern affect cerebrovascular reactivity? Exp Physiol 2021; 107:183-191. [PMID: 34961983 DOI: 10.1113/ep090122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Accepted: 12/22/2021] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? Is cerebrovascular reactivity affected by isocapnic changes in breathing pattern? What is the main finding and its importance? The main finding is that cerebrovascular reactivity does not change with isocapnic variations in tidal volume and frequency. ABSTRACT Deviations of arterial carbon dioxide tension from resting values affect cerebral blood vessel tone and thereby cerebral blood flow. Arterial carbon dioxide tension also affects central respiratory chemoreceptors, adjusting respiratory drive. This coincidence raises the question whether respiratory drive also affects the cerebral blood flow response to carbon dioxide. A change in cerebral blood flow for a given change in the arterial carbon dioxide tension is defined as cerebrovascular reactivity. Two studies have reached conflicting conclusions on this question, using voluntary control of breathing as a disturbing factor during measurements of cerebrovascular reactivity. Here we address some of the methodological limitations of both studies by using sequential gas delivery and targeted control of carbon dioxide and oxygen to enable a separation of the effects of carbon dioxide on cerebrovascular reactivity from breathing vigor. We confirm there is no detectable superimposed effect of breathing efforts on cerebrovascular reactivity. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Ece Su Sayin
- Department of Anaesthesia and Pain Management, University Health Network, Toronto, Canada.,Department of Physiology, University of Toronto, Toronto, Canada
| | - Anahis Davidian
- Department of Physiology, University of Toronto, Toronto, Canada
| | - Harrison Levine
- Department of Anaesthesia and Pain Management, University Health Network, Toronto, Canada.,Department of Physiology, University of Toronto, Toronto, Canada
| | - Lashmi Venkatraghavan
- Department of Anaesthesia and Pain Management, University Health Network, Toronto, Canada.,Department of Physiology, University of Toronto, Toronto, Canada
| | - David J Mikulis
- Institute of Medical Sciences, University of Toronto, Toronto, Canada.,Joint Department of Medical Imaging and the Functional Neuroimaging Laboratory, University Health Network, Toronto, Canada
| | - Joseph A Fisher
- Department of Anaesthesia and Pain Management, University Health Network, Toronto, Canada.,Department of Physiology, University of Toronto, Toronto, Canada.,Institute of Medical Sciences, University of Toronto, Toronto, Canada
| | - Olivia Sobczyk
- Department of Anaesthesia and Pain Management, University Health Network, Toronto, Canada.,Joint Department of Medical Imaging and the Functional Neuroimaging Laboratory, University Health Network, Toronto, Canada
| | - James Duffin
- Department of Anaesthesia and Pain Management, University Health Network, Toronto, Canada.,Department of Physiology, University of Toronto, Toronto, Canada
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Diabetic mice have retinal and choroidal blood flow deficits and electroretinogram deficits with impaired responses to hypercapnia. PLoS One 2021; 16:e0259505. [PMID: 34882677 PMCID: PMC8659412 DOI: 10.1371/journal.pone.0259505] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Accepted: 10/20/2021] [Indexed: 11/19/2022] Open
Abstract
Purpose The purpose of this study was to investigate neuronal and vascular functional deficits in the retina and their association in a diabetic mouse model. We measured electroretinography (ERG) responses and choroidal and retinal blood flow (ChBF, RBF) with magnetic resonance imaging (MRI) in healthy and diabetic mice under basal conditions and under hypercapnic challenge. Methods Ins2Akita diabetic (Diab, n = 8) and age-matched, wild-type C57BL/6J mice (Ctrl, n = 8) were studied under room air and moderate hypercapnia (5% CO2). Dark-adapted ERG a-wave, b-wave, and oscillatory potentials (OPs) were measured for a series of flashes. Regional ChBF and RBF under air and hypercapnia were measured using MRI in the same mice. Results Under room air, Diab mice had compromised ERG b-wave and OPs (e.g., b-wave amplitude was 422.2±10.7 μV in Diab vs. 600.1±13.9 μV in Ctrl, p < 0.001). Under hypercapnia, OPs and b-wave amplitudes were significantly reduced in Diab (OPs by 30.3±3.0% in Diab vs. -3.0±3.6% in Ctrl, b-wave by 17.9±1.4% in Diab vs. 1.3±0.5% in Ctrl). Both ChBF and RBF had significant differences in regional blood flow, with Diab mice having substantially lower blood flow in the nasal region (ChBF was 5.4±1.0 ml/g/min in Diab vs. 8.6±1.0 ml/g/min in Ctrl, RBF was 0.91±0.10 ml/g/min in Diab vs. 1.52±0.24 ml/g/min in Ctrl). Under hypercapnia, ChBF increased in both Ctrl and Diab without significant group difference (31±7% in Diab vs. 17±7% in Ctrl, p > 0.05), but an increase in RBF was not detected for either group. Conclusions Inner retinal neuronal function and both retinal and choroidal blood flow were impaired in Diab mice. Hypercapnia further compromised inner retinal neuronal function in diabetes, while the blood flow response was not affected, suggesting that the diabetic retina has difficulty adapting to metabolic challenges due to factors other than impaired blood flow regulation.
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Yamashiro SM, Kato T. Modeling cerebral blood flow and ventilation instability due to CO 2. J Appl Physiol (1985) 2021; 130:1427-1435. [PMID: 33764171 DOI: 10.1152/japplphysiol.00949.2020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
A minimal model of cerebral blood flow and respiratory control was developed to describe hypocapnic and hypercapnic responses. Important nonlinear properties such as cerebral blood flow changes with arterial partial pressure of carbon dioxide ([Formula: see text]) and associated time-dependent circulatory time delays were included. It was also necessary to vary cerebral metabolic rate as a function of [Formula: see text]. The cerebral blood flow model was added to a previously developed respiratory control model to simulate central and peripheral controller dynamics for humans. Model validation was based on previously collected data. The variable time delay due to brain blood flow changes in hypercapnia was an important determinant of predicted instability due to nonlinear interaction in addition to linear loop gain considerations. Peripheral chemoreceptor gains above a critical level, but within normal limits, were necessary to produce instability. Instability was observed in recovery from hypercapnia and hypocapnia. The 20-s breath-hold test appears to be a simple test of brain blood flow-mediated instability in hypercapnia. Brain blood flow was predicted to play an important role with nonlinear properties. There is an important interaction predicted by the current model between central and peripheral control mechanisms related to instability in hypercapnia recovery. Posthyperventilation breathing pattern can also reveal instability tied to brain blood flow. Previous data collected in patients with chronic obstructive lung disease were closely fitted with the current model and instability predicted. Brain vascular volume was proposed as a potential cause of instability despite cerebral autoregulation promoting constant brain flow.NEW & NOTEWORTHY Prior models of brain blood flow and respiratory control have not focused on instability. Time varying time delay resulting from brain blood flow changes due to carbon dioxide (CO2) and peripheral chemoreceptor gain were predicted to be important determinants of instability due to nonlinear interaction in addition to linear control loop gain. Time delay was assumed to be set by the ratio of brain arterial vascular volume and blood flow. This vascular volume was predicted to also significantly change with CO2.
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Affiliation(s)
- Stanley M Yamashiro
- Biomedical Engineering Department, University of Southern California, Los Angeles, California
| | - Takahide Kato
- Department of General Education, National Institute of Technology, Toyota College, Toyota, Japan
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Pham T, Blaney G, Sassaroli A, Fernandez C, Fantini S. Sensitivity of frequency-domain optical measurements to brain hemodynamics: simulations and human study of cerebral blood flow during hypercapnia. BIOMEDICAL OPTICS EXPRESS 2021; 12:766-789. [PMID: 33680541 PMCID: PMC7901322 DOI: 10.1364/boe.412766] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Revised: 12/04/2020] [Accepted: 12/16/2020] [Indexed: 05/20/2023]
Abstract
This study characterizes the sensitivity of noninvasive measurements of cerebral blood flow (CBF) by using frequency-domain near-infrared spectroscopy (FD-NIRS) and coherent hemodynamics spectroscopy (CHS). We considered six FD-NIRS methods: single-distance intensity and phase (SDI and SDϕ), single-slope intensity and phase (SSI and SSϕ), and dual-slope intensity and phase (DSI and DSϕ). Cerebrovascular reactivity (CVR) was obtained from the relative change in measured CBF during a step hypercapnic challenge. Greater measured values of CVR are assigned to a greater sensitivity to cerebral hemodynamics. In a first experiment with eight subjects, CVRSDϕ was greater than CVRSDI (p < 0.01), whereas CVRDSI and CVRDSϕ showed no significant difference (p > 0.5). In a second experiment with four subjects, a 5 mm scattering layer was added between the optical probe and the scalp tissue to increase the extracerebral layer thickness (L ec ), which caused CVRDSϕ to become significantly greater than CVRDSI (p < 0.05). CVRSS measurements yielded similar results as CVRDS measurements but with a greater variability, possibly resulting from instrumental artifacts in SS measurements. Theoretical simulations with two-layered media confirmed that, if the top (extracerebral) layer is more scattering than the bottom (brain) layer, the relative values of CVRDSI and CVRDSϕ depend on L ec . Specifically, the sensitivity to the brain is greater for DSI than DSϕ for a thin extracerebral layer (L ec < 13 mm), whereas it is greater for DSϕ than DSI for a thicker extracerebral layer.
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Affiliation(s)
- Thao Pham
- Tufts University, Department of Biomedical Engineering, 4 Colby Street, Medford, MA 02155, USA
| | - Giles Blaney
- Tufts University, Department of Biomedical Engineering, 4 Colby Street, Medford, MA 02155, USA
| | - Angelo Sassaroli
- Tufts University, Department of Biomedical Engineering, 4 Colby Street, Medford, MA 02155, USA
| | - Cristianne Fernandez
- Tufts University, Department of Biomedical Engineering, 4 Colby Street, Medford, MA 02155, USA
| | - Sergio Fantini
- Tufts University, Department of Biomedical Engineering, 4 Colby Street, Medford, MA 02155, USA
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Shalom DE, Trevisan MA, Mallela A, Nuñez M, Goldschmidt E. Brain folding shapes the branching pattern of the middle cerebral artery. PLoS One 2021; 16:e0245167. [PMID: 33411825 PMCID: PMC7790398 DOI: 10.1371/journal.pone.0245167] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Accepted: 12/22/2020] [Indexed: 11/19/2022] Open
Abstract
The folds of the brain offer a particular challenge for the subarachnoid vascular grid. The primitive blood vessels that occupy this space, when the brain is flat, have to adapt to an everchanging geometry while constructing an efficient network. Surprisingly, the result is a non-redundant arterial system easily challenged by acute occlusions. Here, we generalize the optimal network building principles of a flat surface growing into a folded configuration and generate an ideal middle cerebral artery (MCA) configuration that can be directly compared with the normal brain anatomy. We then describe how the Sylvian fissure (the fold in which the MCA is buried) is formed during development and use our findings to account for the differences between the ideal and the actual shaping pattern of the MCA. Our results reveal that folding dynamics condition the development of arterial anastomosis yielding a network without loops and poor response to acute occlusions.
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Affiliation(s)
- Diego E. Shalom
- Physics Institute of Buenos Aires (IFIBA) CONICET, Buenos Aires, Argentina
- Department of Physics, University of Buenos Aires (UBA), Buenos Aires, Argentina
| | - Marcos A. Trevisan
- Physics Institute of Buenos Aires (IFIBA) CONICET, Buenos Aires, Argentina
- Department of Physics, University of Buenos Aires (UBA), Buenos Aires, Argentina
| | - Arka Mallela
- Department of Neurosurgery, University of Pittsburgh Medical Center, Pittsburgh, PA, United States of America
| | - Maximiliano Nuñez
- Department of Neurosurgery, El Cruce Hospital, Provincia de Buenos Aires, Argentina
| | - Ezequiel Goldschmidt
- Department of Neurosurgery, University of Pittsburgh Medical Center, Pittsburgh, PA, United States of America
- Division of Molecular Neurobiology, Department of Medical Biochemistry and Biophysics, Karolinska Institute, Stockholm, Sweden
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7
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Duffin J. Fail‐safe aspects of oxygen supply. J Physiol 2020; 598:4859-4867. [DOI: 10.1113/jp280301] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Accepted: 08/03/2020] [Indexed: 12/30/2022] Open
Affiliation(s)
- James Duffin
- Department of Anesthesiology and Pain Medicine University of Toronto Toronto Ontario Canada
- Department of Physiology University of Toronto Toronto Ontario Canada
- Thornhill Medical Toronto Ontario Canada
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8
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Burley CV, Lucas RAI, Whittaker AC, Mullinger K, Lucas SJE. The CO 2 stimulus duration and steady-state time point used for data extraction alters the cerebrovascular reactivity outcome measure. Exp Physiol 2020; 105:893-903. [PMID: 32083357 DOI: 10.1113/ep087883] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2019] [Accepted: 02/19/2020] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? Cerebrovascular reactivity (CVR) is a common functional test to assess brain health, and impaired CVR has been associated with all-cause cardiovascular mortality: does the duration of the CO2 stimulus and the time point used for data extraction alter the CVR outcome measure? What is the main finding and its importance? This study demonstrated CVR measures calculated from 1 and 2 min CO2 stimulus durations were significantly higher than CVR calculated from a 4 min CO2 stimulus. CVRs calculated from the first 2 min of the CO2 stimulus were significantly higher than CVR values calculated from the final minute if the duration was ≥4 min. This study highlights the need for consistent methodological approaches. ABSTRACT Cerebrovascular reactivity to carbon dioxide (CVR) is a common functional test to assess brain vascular health, though conflicting age and fitness effects have been reported. Studies have used different CO2 stimulus durations to induce CVR and extracted data from different time points for analysis. Therefore, this study examined whether these differences alter CVR and explain conflicting findings. Eighteen healthy volunteers (24 ± 5 years) inhaled CO2 for four stimulus durations (1, 2, 4 and 5 min) of 5% CO2 (in air) via the open-circuit Douglas bag method, in a randomized order. CVR data were derived from transcranial Doppler (TCD) measures of middle cerebral artery blood velocity (MCAv), with concurrent ventilatory sensitivity to the CO2 stimulus ( V ̇ E , C O 2 ). Repeated measures ANOVAs compared CVR and V ̇ E , C O 2 measures between stimulus durations and steady-state time points. An effect of stimulus duration was observed (P = 0.002, η² = 0.140), with 1 min (P = 0.010) and 2 min (P < 0.001) differing from 4 min, and 2 min differing from 5 min (P = 0.019) durations. V ̇ E , C O 2 sensitivity increased ∼3-fold from 1 min to 4 and 5 min durations (P < 0.001, η² = 0.485). CVRs calculated from different steady-state time points within each stimulus duration were different (P < 0.001, η² = 0.454), specifically for 4 min (P = 0.001) and 5 min (P < 0.001), but not 2 min stimulus durations (P = 0.273). These findings demonstrate that methodological differences alter the CVR measure.
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Affiliation(s)
- Claire V Burley
- School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, UK.,Centre for Human Brain Health, University of Birmingham, Birmingham, UK
| | - Rebekah A I Lucas
- School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, UK
| | - Anna C Whittaker
- School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, UK
| | - Karen Mullinger
- Centre for Human Brain Health, University of Birmingham, Birmingham, UK.,School of Psychology, University of Birmingham, Birmingham, UK.,School of Physics and Astronomy, University of Nottingham, Nottingham, UK
| | - Samuel J E Lucas
- School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, UK.,Centre for Human Brain Health, University of Birmingham, Birmingham, UK.,Department of Physiology, University of Otago, New Zealand
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van Niftrik CHB, Piccirelli M, Bozinov O, Pangalu A, Fisher JA, Valavanis A, Luft AR, Weller M, Regli L, Fierstra J. Iterative analysis of cerebrovascular reactivity dynamic response by temporal decomposition. Brain Behav 2017; 7:e00705. [PMID: 28948064 PMCID: PMC5607533 DOI: 10.1002/brb3.705] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Revised: 02/28/2017] [Accepted: 03/01/2017] [Indexed: 12/24/2022] Open
Abstract
OBJECTIVE To improve quantitative cerebrovascular reactivity (CVR) measurements and CO 2 arrival times, we present an iterative analysis capable of decomposing different temporal components of the dynamic carbon dioxide- Blood Oxygen-Level Dependent (CO 2-BOLD) relationship. EXPERIMENTAL DESIGN Decomposition of the dynamic parameters included a redefinition of the voxel-wise CO 2 arrival time, and a separation from the vascular response to a stepwise increase in CO 2 (Delay to signal Plateau - DTP) and a decrease in CO 2 (Delay to signal Baseline -DTB). Twenty-five (normal) datasets, obtained from BOLD MRI combined with a standardized pseudo-square wave CO 2 change, were co-registered to generate reference atlases for the aforementioned dynamic processes to score the voxel-by-voxel deviation probability from normal range. This analysis is further illustrated in two subjects with unilateral carotid artery occlusion using these reference atlases. PRINCIPAL OBSERVATIONS We have found that our redefined CO 2 arrival time resulted in the best data fit. Additionally, excluding both dynamic BOLD phases (DTP and DTB) resulted in a static CVR, that is maximal response, defined as CVR calculated only over a normocapnic and hypercapnic calibrated plateau. CONCLUSION Decomposition and novel iterative modeling of different temporal components of the dynamic CO 2-BOLD relationship improves quantitative CVR measurements.
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Affiliation(s)
- Christiaan Hendrik Bas van Niftrik
- Department of NeurosurgeryUniversity Hospital ZurichUniversity of ZurichZurichSwitzerland
- Clinical Neuroscience CenterUniversity Hospital ZurichZurichSwitzerland
| | - Marco Piccirelli
- Clinical Neuroscience CenterUniversity Hospital ZurichZurichSwitzerland
- Department of NeuroradiologyUniversity Hospital ZurichUniversity of ZurichZurichSwitzerland
| | - Oliver Bozinov
- Department of NeurosurgeryUniversity Hospital ZurichUniversity of ZurichZurichSwitzerland
- Clinical Neuroscience CenterUniversity Hospital ZurichZurichSwitzerland
| | - Athina Pangalu
- Clinical Neuroscience CenterUniversity Hospital ZurichZurichSwitzerland
- Department of NeuroradiologyUniversity Hospital ZurichUniversity of ZurichZurichSwitzerland
| | - Joseph A. Fisher
- Department of AnesthesiologyUniversity Health NetworkUniversity of TorontoTorontoONCanada
| | - Antonios Valavanis
- Clinical Neuroscience CenterUniversity Hospital ZurichZurichSwitzerland
- Department of NeuroradiologyUniversity Hospital ZurichUniversity of ZurichZurichSwitzerland
| | - Andreas R. Luft
- Clinical Neuroscience CenterUniversity Hospital ZurichZurichSwitzerland
- Department of NeurologyUniversity Hospital ZurichUniversity of ZurichZurichSwitzerland
- Cereneo Center for Neurology and RehabilitationVitznauSwitzerland
| | - Michael Weller
- Clinical Neuroscience CenterUniversity Hospital ZurichZurichSwitzerland
- Department of NeurologyUniversity Hospital ZurichUniversity of ZurichZurichSwitzerland
| | - Luca Regli
- Department of NeurosurgeryUniversity Hospital ZurichUniversity of ZurichZurichSwitzerland
- Clinical Neuroscience CenterUniversity Hospital ZurichZurichSwitzerland
| | - Jorn Fierstra
- Department of NeurosurgeryUniversity Hospital ZurichUniversity of ZurichZurichSwitzerland
- Clinical Neuroscience CenterUniversity Hospital ZurichZurichSwitzerland
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Mutch WAC, Ellis MJ, Ryner LN, Ruth Graham M, Dufault B, Gregson B, Hall T, Bunge M, Essig M. Brain magnetic resonance imaging CO2 stress testing in adolescent postconcussion syndrome. J Neurosurg 2016; 125:648-60. [DOI: 10.3171/2015.6.jns15972] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
OBJECT
A neuroimaging assessment tool to visualize global and regional impairments in cerebral blood flow (CBF) and cerebrovascular responsiveness in individual patients with concussion remains elusive. Here the authors summarize the safety, feasibility, and results of brain CO2 stress testing in adolescents with postconcussion syndrome (PCS) and healthy controls.
METHODS
This study was approved by the Biomedical Research Ethics Board at the University of Manitoba. Fifteen adolescents with PCS and 17 healthy control subjects underwent anatomical MRI, pseudo-continuous arterial spin labeling MRI, and brain stress testing using controlled CO2 challenge and blood oxygen level–dependent (BOLD) MRI. Post hoc processing was performed using statistical parametric mapping to determine voxel-by-voxel regional resting CBF and cerebrovascular responsiveness of the brain to the CO2 stimulus (increase in BOLD signal) or the inverse (decrease in BOLD signal). Receiver operating characteristic (ROC) curves were generated to compare voxel counts categorized by control (0) or PCS (1).
RESULTS
Studies were well tolerated without any serious adverse events. Anatomical MRI was normal in all study participants. No differences in CO2 stimuli were seen between the 2 participant groups. No group differences in global mean CBF were detected between PCS patients and healthy controls. Patient-specific differences in mean regional CBF and CO2 BOLD responsiveness were observed in all PCS patients. The ROC curve analysis for brain regions manifesting a voxel response greater than and less than the control atlas (that is, abnormal voxel counts) produced an area under the curve of 0.87 (p < 0.0001) and 0.80 (p = 0.0003), respectively, consistent with a clinically useful predictive model.
CONCLUSIONS
Adolescent PCS is associated with patient-specific abnormalities in regional mean CBF and BOLD cerebrovascular responsiveness that occur in the setting of normal global resting CBF. Future prospective studies are warranted to examine the utility of brain MRI CO2 stress testing in the longitudinal assessment of acute sports-related concussion and PCS.
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Ellis MJ, Ryner LN, Sobczyk O, Fierstra J, Mikulis DJ, Fisher JA, Duffin J, Mutch WAC. Neuroimaging Assessment of Cerebrovascular Reactivity in Concussion: Current Concepts, Methodological Considerations, and Review of the Literature. Front Neurol 2016; 7:61. [PMID: 27199885 PMCID: PMC4850165 DOI: 10.3389/fneur.2016.00061] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Accepted: 04/11/2016] [Indexed: 01/07/2023] Open
Abstract
Concussion is a form of traumatic brain injury (TBI) that presents with a wide spectrum of subjective symptoms and few objective clinical findings. Emerging research suggests that one of the processes that may contribute to concussion pathophysiology is dysregulation of cerebral blood flow (CBF) leading to a mismatch between CBF delivery and the metabolic needs of the injured brain. Cerebrovascular reactivity (CVR) is defined as the change in CBF in response to a measured vasoactive stimulus. Several magnetic resonance imaging (MRI) techniques can be used as a surrogate measure of CBF in clinical and laboratory studies. In order to provide an accurate assessment of CVR, these sequences must be combined with a reliable, reproducible vasoactive stimulus that can manipulate CBF. Although CVR imaging currently plays a crucial role in the diagnosis and management of many cerebrovascular diseases, only recently have studies begun to apply this assessment tool in patients with concussion. In order to evaluate the quality, reliability, and relevance of CVR studies in concussion, it is important that clinicians and researchers have a strong foundational understanding of the role of CBF regulation in health, concussion, and more severe forms of TBI, and an awareness of the advantages and limitations of currently available CVR measurement techniques. Accordingly, in this review, we (1) discuss the role of CVR in TBI and concussion, (2) examine methodological considerations for MRI-based measurement of CVR, and (3) provide an overview of published CVR studies in concussion patients.
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Affiliation(s)
- Michael J Ellis
- Department of Surgery, University of Manitoba, Winnipeg, MB, Canada; Department of Pediatrics and Child Health, University of Manitoba, Winnipeg, MB, Canada; Section of Neurosurgery, University of Manitoba, Winnipeg, MB, Canada; Pan Am Concussion Program, University of Manitoba, Winnipeg, MB, Canada; Childrens Hospital Research Institute of Manitoba, University of Manitoba, Winnipeg, MB, Canada; Canada North Concussion Network, University of Manitoba, Winnipeg, MB, Canada; University of Manitoba, Winnipeg, MB, Canada
| | - Lawrence N Ryner
- Canada North Concussion Network, University of Manitoba, Winnipeg, MB, Canada; Department of Radiology, University of Manitoba, Winnipeg, MB, Canada; Health Sciences Centre, University of Manitoba, Winnipeg, MB, Canada
| | - Olivia Sobczyk
- Institute of Medical Sciences, University of Toronto , Toronto, ON , Canada
| | - Jorn Fierstra
- Department of Neurosurgery, University Hospital Zurich , Zurich , Switzerland
| | - David J Mikulis
- Department of Medical Imaging, University of Toronto, Toronto, ON, Canada; University of Toronto, Toronto, ON, Canada; University Health Network Cerebrovascular Reactivity Research Group, Toronto, ON, Canada
| | - Joseph A Fisher
- University of Toronto, Toronto, ON, Canada; University Health Network Cerebrovascular Reactivity Research Group, Toronto, ON, Canada; Department of Anesthesia, University of Toronto, Toronto, ON, Canada
| | - James Duffin
- University of Toronto, Toronto, ON, Canada; University Health Network Cerebrovascular Reactivity Research Group, Toronto, ON, Canada; Department of Physiology, University of Toronto, Toronto, ON, Canada
| | - W Alan C Mutch
- Canada North Concussion Network, University of Manitoba, Winnipeg, MB, Canada; University of Manitoba, Winnipeg, MB, Canada; Health Sciences Centre, University of Manitoba, Winnipeg, MB, Canada; Department of Anesthesia and Perioperative Medicine, University of Manitoba, Winnipeg, MB, Canada
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Poublanc J, Crawley AP, Sobczyk O, Montandon G, Sam K, Mandell DM, Dufort P, Venkatraghavan L, Duffin J, Mikulis DJ, Fisher JA. Measuring cerebrovascular reactivity: the dynamic response to a step hypercapnic stimulus. J Cereb Blood Flow Metab 2015; 35:1746-56. [PMID: 26126862 PMCID: PMC4635229 DOI: 10.1038/jcbfm.2015.114] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Revised: 04/13/2015] [Accepted: 04/14/2015] [Indexed: 11/09/2022]
Abstract
We define cerebral vascular reactivity (CVR) as the ratio of the change in blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI) signal (S) to an increase in blood partial pressure of CO2 (PCO2): % Δ S/Δ PCO2 mm Hg. Our aim was to further characterize CVR into dynamic and static components and then study 46 healthy subjects collated into a reference atlas and 20 patients with unilateral carotid artery stenosis. We applied an abrupt boxcar change in PCO2 and monitored S. We convolved the PCO2 with a set of first-order exponential functions whose time constant τ was increased in 2-second intervals between 2 and 100 seconds. The τ corresponding to the best fit between S and the convolved PCO2 was used to score the speed of response. Additionally, the slope of the regression between S and the convolved PCO2 represents the steady-state CVR (ssCVR). We found that both prolongations of τ and reductions in ssCVR (compared with the reference atlas) were associated with the reductions in CVR on the side of the lesion. τ and ssCVR are respectively the dynamic and static components of measured CVR.
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Affiliation(s)
- Julien Poublanc
- Joint Department of Medical Imaging, University Health Network, Toronto, Ontario, Canada
| | - Adrian P Crawley
- Joint Department of Medical Imaging, University Health Network, Toronto, Ontario, Canada
| | - Olivia Sobczyk
- Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada
| | - Gaspard Montandon
- Joint Department of Medical Imaging, University Health Network, Toronto, Ontario, Canada
| | - Kevin Sam
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada
| | - Daniel M Mandell
- Joint Department of Medical Imaging, University Health Network, Toronto, Ontario, Canada
| | - Paul Dufort
- Joint Department of Medical Imaging, University Health Network, Toronto, Ontario, Canada
| | | | - James Duffin
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada.,Department of Anaesthesia and Pain Management, University Health Network, Toronto, Ontario, Canada
| | - David J Mikulis
- Joint Department of Medical Imaging, University Health Network, Toronto, Ontario, Canada.,Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada
| | - Joseph A Fisher
- Joint Department of Medical Imaging, University Health Network, Toronto, Ontario, Canada.,Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada.,Department of Physiology, University of Toronto, Toronto, Ontario, Canada.,Department of Anaesthesia and Pain Management, University Health Network, Toronto, Ontario, Canada
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Nakai H, Tsujimoto K, Fuchigami T, Ohmatsu S, Osumi M, Nakano H, Fukui M, Morioka S. Effect of anticipation triggered by a prior dyspnea experience on brain activity. J Phys Ther Sci 2015; 27:635-9. [PMID: 25931697 PMCID: PMC4395681 DOI: 10.1589/jpts.27.635] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Accepted: 10/07/2014] [Indexed: 11/29/2022] Open
Abstract
[Purpose] Oxygenated hemoglobin (oxy-Hb) concentrations in the prefrontal cortex are
closely associated with dyspnea. Dyspnea is influenced not only by physical activity, but
also by visual stimuli, and several studies suggest that oxy-Hb concentrations change in
response to certain external stimuli. However, the effects of internal psychological
states on dyspnea have not been reported. This study explored the influence of
anticipation triggered by previous episodes of dyspnea on brain activity. [Subjects] The
subjects were 15 healthy volunteers with a mean age of 25.0 ± 3.0 years. [Methods] The
subjects were shown a variety of photographs and instructed to expect breathing resistance
matched to the affective nature of the particular photograph. After viewing the images,
varying intensities of breathing resistance that were identical to, easier than, or harder
than those shown in the images were randomly administered to the subjects; in fact, the
image and resistance were identical 33% of the time and discordant 66% of the time.
[Results] The concentrations of oxy-Hb in the right medial prefrontal cortex (rMPFC)
increased significantly with an inspiratory pressure that was 30% of the maximum intensity
in the subjects shown a pleasant image compared to the concentrations in subjects shown an
unpleasant image. Moreover, rMPFC activity was significantly correlated with the magnitude
of the dyspnea experienced. [Conclusion] These results suggest that a correlation exists
between increased oxy-Hb in the rMPFC and the effects of expectations on dyspnea.
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Affiliation(s)
- Hideki Nakai
- Department of Rehabilitation, Higashi Osaka Hospital, Japan
| | | | | | - Satoko Ohmatsu
- Department of Neurorehabilitation, Graduate School of Health Science, Kio University, Japan
| | - Michihiro Osumi
- Department of Neurorehabilitation, Graduate School of Health Science, Kio University, Japan
| | - Hideki Nakano
- Department of Neurorehabilitation, Graduate School of Health Science, Kio University, Japan
| | - Manami Fukui
- Department of Rehabilitation Medicine, Higashi Osaka Hospital, Japan
| | - Shu Morioka
- Department of Neurorehabilitation, Graduate School of Health Science, Kio University, Japan
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The dynamics of cerebrovascular reactivity shown with transfer function analysis. Neuroimage 2015; 114:207-16. [PMID: 25891374 DOI: 10.1016/j.neuroimage.2015.04.029] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2014] [Revised: 04/06/2015] [Accepted: 04/11/2015] [Indexed: 01/24/2023] Open
Abstract
Cerebrovascular reactivity (CVR) is often defined as the increase in cerebral blood flow (CBF) produced by an increase in carbon dioxide (CO2) and may be used clinically to assess the health of the cerebrovasculature. When CBF is estimated using blood oxygen level dependent (BOLD) magnetic resonance imaging, CVR values for each voxel can be displayed using a color scale mapped onto the corresponding anatomical scan. While these CVR maps therefore show the distribution of cerebrovascular reactivity, they only provide an estimate of the magnitude of the cerebrovascular response, and do not indicate the time course of the response; whether rapid or slow. Here we describe transfer function analysis (TFA) of the BOLD response to CO2 that provides not only the magnitude of the response (gain) but also the phase and coherence. The phase can be interpreted as indicating the speed of response and so can distinguish areas where the response is slowed. The coherence measures the fidelity with which the response follows the stimulus. The examples of gain, phase and coherence maps obtained from TFA of previously recorded test data from patients and healthy individuals demonstrate that these maps may enhance assessment of cerebrovascular pathophysiology by providing insight into the dynamics of cerebral blood flow control and distribution.
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Regan RE, Fisher JA, Duffin J. Factors affecting the determination of cerebrovascular reactivity. Brain Behav 2014; 4:775-88. [PMID: 25328852 PMCID: PMC4188369 DOI: 10.1002/brb3.275] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Revised: 07/14/2014] [Accepted: 07/27/2014] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND AND PURPOSE Cerebrovascular reactivity (CVR), measures the ability of the cerebrovasculature to respond to vasoactive stimuli such as CO2. CVR is often expressed as the ratio of cerebral blood flow change to CO2 change. We examine several factors affecting this measurement: blood pressure, stimulus pattern, response analysis and subject position. METHODS Step and ramp increases in CO2 were implemented in nine subjects, seated and supine. Middle cerebral artery blood flow velocity (MCAv), and mean arterial pressure (MAP) were determined breath-by-breath. Cerebrovascular conductance (MCAc) was estimated as MCAv/MAP. CVR was calculated from both the relative and absolute measures of MCAc and MCAv responses. RESULTS MAP increased with CO2 in some subjects so that relative CVR calculated from conductance responses were less than those calculated from CVR calculated from velocity responses. CVR measured from step responses were affected by the response dynamics, and were less than those calculated from CVR measured from ramp responses. Subject position did not affect CVR. CONCLUSIONS (1) MAP increases with CO2 and acts as a confounding factor for CVR measurement; (2) CVR depends on the stimulus pattern used; (3) CVR did not differ from the sitting versus supine in these experiments; (4) CVR calculated from absolute changes of MCAv was less than that calculated from relative changes.
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Affiliation(s)
- Rosemary E Regan
- Department of Physiology, University of Toronto Toronto, ON, M5S 1A8, Canada
| | - Joseph A Fisher
- Department of Physiology, University of Toronto Toronto, ON, M5S 1A8, Canada ; Department of Anaesthesiology, University of Toronto Toronto, ON, Canada ; University Health Network Toronto, ON, Canada
| | - James Duffin
- Department of Physiology, University of Toronto Toronto, ON, M5S 1A8, Canada ; Department of Anaesthesiology, University of Toronto Toronto, ON, Canada ; University Health Network Toronto, ON, Canada
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Mutch WAC, Ellis MJ, Graham MR, Wourms V, Raban R, Fisher JA, Mikulis D, Leiter J, Ryner L. Brain MRI CO2 stress testing: a pilot study in patients with concussion. PLoS One 2014; 9:e102181. [PMID: 25032707 PMCID: PMC4102518 DOI: 10.1371/journal.pone.0102181] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Accepted: 06/15/2014] [Indexed: 11/21/2022] Open
Abstract
BACKGROUND There is a real need for quantifiable neuro-imaging biomarkers in concussion. Here we outline a brain BOLD-MRI CO2 stress test to assess the condition. METHODS This study was approved by the REB at the University of Manitoba. A group of volunteers without prior concussion were compared to post-concussion syndrome (PCS) patients--both symptomatic and recovered asymptomatic. Five 3-minute periods of BOLD imaging at 3.0 T were studied--baseline 1 (BL1--at basal CO2 tension), hypocapnia (CO2 decreased ∼5 mmHg), BL2, hypercapnia (CO2 increased ∼10 mmHg) and BL3. Data were processed using statistical parametric mapping (SPM) for 1st level analysis to compare each subject's response to the CO2 stress at the p = 0.001 level. A 2nd level analysis compared each PCS patient's response to the mean response of the control subjects at the p = 0.05 level. RESULTS We report on 5 control subjects, 8 symptomatic and 4 asymptomatic PCS patients. Both increased and decreased response to CO2 was seen in all PCS patients in the 2nd level analysis. The responses were quantified as reactive voxel counts: whole brain voxel counts (2.0±1.6%, p = 0.012 for symptomatic patients for CO2 response < controls and 3.0±5.1%, p = 0.139 for CO2 response > controls: 0.49±0.31%, p = 0.053 for asymptomatic patients for CO2 response < controls and 4.4±6.8%, p = 0.281 for CO2 response > controls). CONCLUSIONS Quantifiable alterations in regional cerebrovascular responsiveness are present in concussion patients during provocative CO2 challenge and BOLD MRI and not in healthy controls. Future longitudinal studies must aim to clarify the relationship between CO2 responsiveness and individual patient symptoms and outcomes.
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Affiliation(s)
- W. Alan C. Mutch
- Department of Anesthesia and Perioperative Medicine, Health Sciences Centre, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Michael J. Ellis
- Department of Surgery, Section of Neurosurgery, Health Sciences Centre, University of Manitoba, Winnipeg, Manitoba, Canada
| | - M. Ruth Graham
- Department of Anesthesia and Perioperative Medicine, Health Sciences Centre, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Vincent Wourms
- Department of Anesthesia and Perioperative Medicine, Health Sciences Centre, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Roshan Raban
- Department of Anesthesia and Perioperative Medicine, Health Sciences Centre, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Joseph A. Fisher
- Department of Anesthesia and Pain Management, Toronto General Hospital, University of Toronto, Toronto, Ontario, Canada
| | - David Mikulis
- Department of Radiology, Section of Neuroimaging, Toronto Western Hospital, University of Toronto, Toronto, Ontario, Canada
| | - Jeffrey Leiter
- Department of Surgery, Pan Am Clinic, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Lawrence Ryner
- Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba, Canada
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