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Monteiro A, Castro P, Pereira G, Ferreira C, Polonia J, Lobo M, Azevedo E. Cerebral blood flow regulation and cognitive performance in hypertension. J Cereb Blood Flow Metab 2024:271678X241254680. [PMID: 38738526 DOI: 10.1177/0271678x241254680] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 05/14/2024]
Abstract
We examined the relation between transcranial Doppler (TCD) markers of cerebral blood flow regulation and cognitive performance in hypertension (HT) patients to evaluate the predictive value of these markers for cognitive decline. We assessed dynamic cerebral autoregulation (dCA), vasoreactivity to carbon dioxide, and neurovascular coupling (NVC) in the middle (MCA) and posterior (PCA) cerebral arteries of 52 patients. Neuropsychological evaluation included the Montreal Cognitive Assessment and tests covering attention, executive function, processing speed, and memory. Notably, reduced rate time in the PCA significantly predicted better processing speed (p = 0.003). Furthermore, reduced overshoot systolic cerebral blood velocity in the PCA and reduced phase in the VLF range in the MCA (p = 0.021 and p = 0.017, respectively) significantly predicted better memory. Intriguingly, enhanced dCA in the MCA predicted poorer memory performance, while reduced NVC in the PCA predicted both superior processing speed and memory performance. These findings suggest that HT-induced changes in cerebral hemodynamics impact cognitive performance. Further research should verify these observations and elucidate whether these changes represent adaptive responses or neurovascular inefficiency. TCD markers might provide insights into HT-related cognitive decline.
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Affiliation(s)
- Ana Monteiro
- UnIC@RISE, Department of Clinical Neurosciences and Mental Health, Faculty of Medicine of University of Porto, Porto, Portugal
- Department of Neurology, Unidade Local de Saúde Alto Ave - Hospital de Guimarães, E.P.E., Guimarães, Portugal
| | - Pedro Castro
- UnIC@RISE, Department of Clinical Neurosciences and Mental Health, Faculty of Medicine of University of Porto, Porto, Portugal
- Department of Neurology, Centro Hospitalar Universitário de São João, E.P.E., Porto, Portugal
| | - Gilberto Pereira
- Department of Neurology, Centro Hospitalar Universitário de São João, E.P.E., Porto, Portugal
| | - Carmen Ferreira
- Department of Neurology, Centro Hospitalar Universitário de São João, E.P.E., Porto, Portugal
| | - Jorge Polonia
- CINTESIS@RISE, Department of Medicine, Faculty of Medicine of University of Porto, Porto, Portugal
- Hypertension and Cardiovascular Risk Unit, Unidade Local de Saúde de Matosinhos, Matosinhos, Portugal
| | - Mariana Lobo
- CINTESIS@RISE, MEDCIDS Department, Faculty of Medicine of University of Porto, Porto, Portugal
| | - Elsa Azevedo
- UnIC@RISE, Department of Clinical Neurosciences and Mental Health, Faculty of Medicine of University of Porto, Porto, Portugal
- Department of Neurology, Centro Hospitalar Universitário de São João, E.P.E., Porto, Portugal
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Ferreira J, Ferreira P, Azevedo E, Castro P. Assessment of Neurovascular Coupling by Spectral Analysis of Cerebral Blood Flow Velocity With Transcranial Doppler. ULTRASOUND IN MEDICINE & BIOLOGY 2024; 50:751-759. [PMID: 38418342 DOI: 10.1016/j.ultrasmedbio.2024.02.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2023] [Revised: 01/17/2024] [Accepted: 02/04/2024] [Indexed: 03/01/2024]
Abstract
OBJECTIVE Neurovascular coupling (NVC) represents the increase in regional blood flow associated with neural activity. The aim here was to describe a new approach to non-invasive measurement of NVC by spectral analysis of the cerebral blood flow velocity (CBFV) with transcranial Doppler. METHODS In a sample of 20 healthy participants, we monitored systolic CBFV in the left posterior cerebral artery (PCA) during off (eyes closed) and on (flickering checkerboard) periods. The contralateral middle cerebral artery was simultaneously monitored as a control. Each participant was submitted to three experiments, each having five cycles, with increasing duration of the cycles, from 10 s (0.1 Hz) to 20 s (0.05 Hz) and lastly 40 s (0.025 Hz), half the time for on and for off periods, constituting a total of 6 min. The successive cycles were expected to cause oscillation in CBFV in a sinusoidal pattern that could be characterized by spectral analysis. We also measured the classic CBFV overshoot as the relative increase in percentage of systolic CBFV from baseline. The relationship and agreement between the two methods were analyzed by linear regression and Bland-Altman plots. In every participant, a clear peak of amplitude in the PCA CBFV spectrum was discernible at 0.1, 0.05 and 0.025 Hz of visual stimulation. RESULTS On average, this amplitude was 7.1 ± 2.3%, 10.9 ± 3.5% and 17.3 ± 6.5%, respectively. This response contrasted significantly with an absent peak in middle cerebral artery monitoring (p < 0.0001). The spectral amplitude and classic overshoot were highly correlated and linearly related (p < 0.0001). CONCLUSION NVC can be quantified by the spectral amplitude of PCA CBFV at slower and higher frequencies of visual stimulation. This method represents an alternative to classic overshoot without the need for stimulus marking or synchronization.
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Affiliation(s)
- Juliana Ferreira
- UnIC@RISE, Department of Clinical Neurosciences and Mental Health, Faculty of Medicine, University of Porto, Porto, Portugal
| | | | - Elsa Azevedo
- UnIC@RISE, Department of Clinical Neurosciences and Mental Health, Faculty of Medicine, University of Porto, Porto, Portugal; Department of Neurology, Centro Hospitalar Universitário de São João, Porto, Portugal
| | - Pedro Castro
- UnIC@RISE, Department of Clinical Neurosciences and Mental Health, Faculty of Medicine, University of Porto, Porto, Portugal; Department of Neurology, Centro Hospitalar Universitário de São João, Porto, Portugal.
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3
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Could salt intake directly affect the cerebral microvasculature in hypertension? J Stroke Cerebrovasc Dis 2022; 31:106632. [PMID: 35870266 DOI: 10.1016/j.jstrokecerebrovasdis.2022.106632] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Revised: 06/26/2022] [Accepted: 06/30/2022] [Indexed: 11/23/2022] Open
Abstract
OBJECTIVES Excess dietary salt and chronic kidney disease (CKD) are acknowledged stroke risk factors. The development of small vessel disease, similarly affecting the cerebral and renal microvasculatures, may be an important mechanistic link underlying this interaction. Therefore, we aimed to evaluate if the dietary salt intake and markers of CKD (estimated glomerular filtration rate, albuminuria) relate to transcranial Doppler (TCD) markers of cerebral small vessel disease (CSVD) in hypertensive patients. MATERIALS AND METHODS Fifty-six hypertensive patients (57% with diabetes) underwent TCD monitoring in the middle (MCA) and posterior (PCA) cerebral arteries for evaluating neurovascular coupling (NVC), dynamic cerebral autoregulation (dCA), and vasoreactivity to carbon dioxide (VRCO2). We investigated the relation between renal parameters and TCD studies using Pearson's correlation coefficient and linear regression analyses. RESULTS There were no associations between dCA, VRCO2, NVC, and renal function tests. However, there was a negative association between the daily salt intake and the natural frequency during visual stimulation (r2=0.101, ß=-0.340, p=0.035), indicative of increased rigidity of the cerebral resistance vessels that react to cognitive activation. CONCLUSIONS In this cross-sectional study, we found an association between excess dietary salt consumption and CSVD in hypertensive patients. Future research is needed to evaluate whether the natural frequency could be an early, non-invasive, surrogate marker for microvascular dysfunction in hypertension.
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Monteiro A, Castro P, Pereira G, Ferreira C, Sorond F, Milstead A, Higgins JP, Polónia J, Azevedo E. Neurovascular Coupling Is Impaired in Hypertensive and Diabetic Subjects Without Symptomatic Cerebrovascular Disease. Front Aging Neurosci 2021; 13:728007. [PMID: 34690741 PMCID: PMC8526560 DOI: 10.3389/fnagi.2021.728007] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2021] [Accepted: 08/31/2021] [Indexed: 01/04/2023] Open
Abstract
The mechanistic link between hypertension, diabetes and cerebral small vessel disease (CSVD) is still poorly understood. We hypothesized that hypertension and diabetes could impair cerebrovascular regulation prior to irreversibly established cerebrovascular disease. In this study, 52 hypertensive patients [54% males; age 64 ± 11 years; 58% with comorbid diabetes mellitus (DM)] without symptomatic cerebrovascular disease underwent transcranial Doppler (TCD) monitoring in the middle (MCA) and posterior (PCA) cerebral arteries, to assess vasoreactivity to carbon dioxide (VRCO2) and neurovascular coupling (NVC). 1.5T magnetic resonance imaging was also performed and white matter hyperintensity volume was automatically segmented from FLAIR sequences. TCD data from 17 healthy controls were obtained for comparison (47% males; age 60 ± 16 years). Hypertensive patients showed significant impairment of NVC in the PCA, with reduced increment in cerebral blood flow velocity during visual stimulation (22.4 ± 9.2 vs. 31.6 ± 5.7, p < 0.001), as well as disturbed NVC time-varying properties, with slower response (lower rate time: 0.00 ± 0.02 vs. 0.03 ± 6.81, p = 0.001), and reduced system oscillation (reduced natural frequency: 0.18 ± 0.08 vs. 0.22 ± 0.06, p < 0.001), when compared to controls. VRCO2 remained relatively preserved in MCA and PCA. These results were worse in hypertensive diabetic patients, with lower natural frequency (p = 0.043) than non-diabetic patients. White matter disease burden did not predict worse NVC. These findings suggest that hypertensive diabetic patients may have a precocious impairment of NVC, already occurring without symptomatic CSVD. Future research is warranted to evaluate whether NVC assessment could be useful as an early, non-invasive, surrogate marker for CSVD.
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Affiliation(s)
- Ana Monteiro
- Department of Clinical Neurosciences and Mental Health, Faculty of Medicine of University of Porto, Porto, Portugal.,Department of Neurology, Unidade Local de Saúde de Matosinhos, Matosinhos, Portugal
| | - Pedro Castro
- Department of Clinical Neurosciences and Mental Health, Faculty of Medicine of University of Porto, Porto, Portugal.,Department of Neurology, Centro Hospitalar Universitário de São João, Porto, Portugal
| | - Gilberto Pereira
- Department of Clinical Neurosciences and Mental Health, Faculty of Medicine of University of Porto, Porto, Portugal.,Department of Neurology, Centro Hospitalar Universitário de São João, Porto, Portugal
| | - Carmen Ferreira
- Department of Clinical Neurosciences and Mental Health, Faculty of Medicine of University of Porto, Porto, Portugal.,Department of Neurology, Centro Hospitalar Universitário de São João, Porto, Portugal
| | - Farzaneh Sorond
- Department of Neurology, Division of Stroke and Neurocritical, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
| | - Andrew Milstead
- Department of Neurology, Division of Stroke and Neurocritical, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
| | - James P Higgins
- Department of Radiology, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
| | - Jorge Polónia
- Hypertension Unit, Unidade Local de Saúde de Matosinhos, Matosinhos, Portugal.,Department of Medicine, Faculty of Medicine of University of Porto, Porto, Portugal
| | - Elsa Azevedo
- Department of Clinical Neurosciences and Mental Health, Faculty of Medicine of University of Porto, Porto, Portugal.,Department of Neurology, Centro Hospitalar Universitário de São João, Porto, Portugal
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Janzarik WG, Sander M, Rößler J, Sommerlade L, Allignol A, Reinhard M. Cerebral Autoregulation and Neurovascular Coupling after Craniospinal Irradiation in Long-Term Survivors of Malignant Pediatric Brain Tumors of the Posterior Fossa. Neuropediatrics 2021; 52:12-18. [PMID: 33065751 DOI: 10.1055/s-0040-1709452] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
INTRODUCTION Long-term survivors of craniospinal irradiation have an increased risk for stroke which increases with radiation dose and follow-up time. Radiotherapy induces structural changes of the cerebral vasculature, affecting both, large, and small vessels. It is unknown how these structural changes affect functional mechanisms of cerebral blood flow regulation such as cerebral autoregulation and neurovascular coupling. METHODS Using the transcranial Doppler, we compared dynamic cerebral autoregulation and neurovascular coupling of 12 patients after long-term survival of craniospinal irradiation due to a malignant pediatric brain tumor of the posterior fossa and 12 age- and sex-matched healthy patients. Mean arterial blood pressure and cerebral blood flow velocities in the middle and posterior cerebral artery were recorded at rest during normal breathing to assess cerebral autoregulation (transfer function parameters phase and gain, as well as the correlation coefficient indices Mx, Sx, and Dx), and during 10 cycles of a visual task to assess neurovascular coupling (parameters time delay, natural frequency, gain, attenuation, and rate time). RESULTS Parameters of cerebral autoregulation showed a consistent trend toward reduced cerebral autoregulation in patients that did not reach statistical significance. Neurovascular coupling was not altered after craniospinal irradiation. CONCLUSION In this pilot study, we demonstrated a trend toward reduced cerebral autoregulation, and no alteration of neurovascular coupling after irradiation in long-term survivors of malignant pediatric brain tumors of the posterior fossa.
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Affiliation(s)
- Wibke G Janzarik
- Department of Neuropediatrics and Muscle Disorders, Center for Pediatrics, University Medical Center Freiburg, University of Freiburg, Germany
| | - Milena Sander
- Department of Neuropediatrics and Muscle Disorders, Center for Pediatrics, University Medical Center Freiburg, University of Freiburg, Germany
| | - Jochen Rößler
- Department of Pediatric Hematology and Oncology, Center for Pediatrics, University Medical Center Freiburg, University of Freiburg, Germany.,Division of Pediatric Hematology/Oncology, Department of Pediatrics, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Linda Sommerlade
- Institute for Complex Systems and Mathematical Biology, King's College, University of Aberdeen, Aberdeen, United Kingdom
| | | | - Matthias Reinhard
- Department of Neurology and Clinical Neurophysiology, Medical Center Esslingen, Academic Teaching Hospital of the University of Tübingen, Germany.,Department of Neurology and Neurophysiology, University Medical Center Freiburg, University of Freiburg, Germany
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Neurovascular Coupling Impairment in Heart Failure with Reduction Ejection Fraction. Brain Sci 2020; 10:brainsci10100714. [PMID: 33036338 PMCID: PMC7601077 DOI: 10.3390/brainsci10100714] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Revised: 09/27/2020] [Accepted: 10/01/2020] [Indexed: 12/19/2022] Open
Abstract
The hemodynamic consequences of a persistent reduced ejection fraction and unknown cardiac output on the brain have not been thoroughly studied. We sought to explore the status of the mechanisms of cerebrovascular regulation in patients with heart failure with reduced (HFrEF) and recovered (HFrecEF) ejection fraction. We monitored cerebral blood flow velocity (CBFV) with transcranial Doppler and blood pressure. Cerebral autoregulation, assessed by transfer function from the spontaneous oscillations of blood pressure to CBFV and neurovascular coupling (NVC) with visual stimulation were compared between groups of HFrEF, HFrecEF and healthy controls. NVC was significantly impaired in HFrEF patients with reduced augmentation of CBFV during stimulation (overshoot systolic CBFV 19.11 ± 6.92 vs. 22.61 ± 7.78 vs. 27.92 ± 6.84, p = 0.04), slower upright of CBFV (rate time to overshoot: 1.19 ± 3.0 vs. 3.06 (4.30) vs. 2.90 ± 3.84, p = 0.02); p = 0.023) and reduced arterial oscillatory properties (natural frequency 0.17 ± 0.06 vs. 0.20 ± 0.09 vs. 0.24 ± 0.07, p = 0.03; attenuation 0.34 ± 0.24 vs. 0.48 ± 0.35 vs. 0.50 ± 0.23, p = 0.05). Cerebral autoregulation was preserved. The neurovascular unit of subjects with chronically reduced heart pumping capability is severely dysfunctional. Dynamic testing with transcranial Doppler could be useful in these patients, but whether it helps in predicting cognitive impairment must be addressed in future prospective studies.
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Castro P, Gutierres M, Pereira G, Ferreira S, Oliveira JP, Azevedo E. Evaluation of Cerebral Microvascular Regulatory Mechanisms with Transcranial Doppler in Fabry Disease. Brain Sci 2020; 10:brainsci10080528. [PMID: 32784589 PMCID: PMC7464258 DOI: 10.3390/brainsci10080528] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Revised: 08/03/2020] [Accepted: 08/05/2020] [Indexed: 12/14/2022] Open
Abstract
Background: Fabry disease (FD) causes cerebrovascular disease (CVD) even if asymptomatic, and this is why it is important to identify non-invasive methods to monitor the disease. We evaluated the usefulness of the cerebral autoregulation, vasoreactivity, and neurovascular coupling assessed by transcranial Doppler (TCD) in FD. Methods: Ten adult patients with classic phenotype FD, without clinical expression of CVD, and ten healthy controls, were included. We monitored cerebral blood flow velocity with TCD in the middle and posterior cerebral arteries, blood pressure, heart rate, and non-invasive expired carbon dioxide (CO2). Cerebral autoregulation was calculated from the spontaneous oscillations of blood pressure, cerebral vasoreactivity through CO2 inhalation and hyperventilation and neurovascular coupling by the flow velocity change to visual stimulation. Results: FD male patients showed blunted vasoreactivity in posterior circulation (0.70 ± 0.36%/mmHg vs. 1.09 ± 0.18%/mmHg CO2, p = 0.01) and impaired neurovascular coupling (overshoot 15 ± 2.9% vs. 28 ± 6.1%, p < 0.01). Cerebral autoregulation was similar to controls. Conclusion: Male patients with FD classic phenotype and hitherto clinical expression of CVD already show impairment of cerebral vasoreactivity and neurovascular coupling. It supports the notion of an early dysfunction of cerebral microvascular in a presymptomatic stage of CVD in FD and that TCD could be useful in its assessment.
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Affiliation(s)
- Pedro Castro
- Department of Clinical Neurosciences and Mental Health, Faculty of Medicine of University of Porto, 4200-319 Porto, Portugal; (P.C.); (M.G.)
- Cardiovascular Research and Development Unit, Faculty of Medicine of University of Porto, 4200-319 Porto, Portugal
- Department of Neurology, Centro Hospitalar Universitário de São João, 4200-319 Porto, Portugal;
| | - Mariana Gutierres
- Department of Clinical Neurosciences and Mental Health, Faculty of Medicine of University of Porto, 4200-319 Porto, Portugal; (P.C.); (M.G.)
| | - Gilberto Pereira
- Department of Neurology, Centro Hospitalar Universitário de São João, 4200-319 Porto, Portugal;
| | - Susana Ferreira
- Department of Medical Genetics, Faculty of Medicine of University of Porto and Centro Hospitalar Universitário de São João, 4200-319 Porto, Portugal; (S.F.); (J.P.O.)
- i3S–Instituto de Investigação e Inovação em Saúde, 4200-135 Porto, Portugal
| | - João Paulo Oliveira
- Department of Medical Genetics, Faculty of Medicine of University of Porto and Centro Hospitalar Universitário de São João, 4200-319 Porto, Portugal; (S.F.); (J.P.O.)
- i3S–Instituto de Investigação e Inovação em Saúde, 4200-135 Porto, Portugal
| | - Elsa Azevedo
- Department of Clinical Neurosciences and Mental Health, Faculty of Medicine of University of Porto, 4200-319 Porto, Portugal; (P.C.); (M.G.)
- Cardiovascular Research and Development Unit, Faculty of Medicine of University of Porto, 4200-319 Porto, Portugal
- Department of Neurology, Centro Hospitalar Universitário de São João, 4200-319 Porto, Portugal;
- Correspondence: ; Tel.: +351-966-019-939
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Castello-Branco RC, Cerqueira-Silva T, Andrade AL, Gonçalves BMM, Pereira CB, Felix IF, Santos LSB, Porto LM, Marques MEL, Catto MB, Oliveira MA, de Sousa PRSP, Muiños PJR, Maia RM, Schnitman S, Oliveira-Filho J. Association Between Risk of Obstructive Sleep Apnea and Cerebrovascular Reactivity in Stroke Patients. J Am Heart Assoc 2020; 9:e015313. [PMID: 32164495 PMCID: PMC7335520 DOI: 10.1161/jaha.119.015313] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Background Obstructive sleep apnea (OSA) is present in 60% to 70% of stroke patients. Cerebral vasoreactivity in patients with stroke and OSA has not been well studied and could identify a new pathophysiologic mechanism with potential therapeutic intervention. We aimed to determine whether risk categories for OSA are associated with cerebral vasoreactivity in stroke patients. Methods and Results In this cross-sectional study of a cohort of patients with stroke, we used clinical questionnaires (Sleep Obstructive Apnea Score Optimized for Stroke [SOS] and snoring, tiredness, observed, pressure, bmi, age, neck, gender [STOP-BANG] scores) to assess the risk of OSA and transcranial Doppler to assess cerebral vasoreactivity (breath-holding index and visual evoked flow velocity response). Of the 99 patients included, 77 (78%) had medium or high risk of OSA and 80 performed transcranial Doppler. Mean breath-holding index was 0.52±0.37, and median visual evoked flow velocity response was 10.8% (interquartile range: 8.8-14.5); 54 of 78 (69%) showed impaired anterior circulation vasoreactivity (breath-holding index <0.69) and 53 of 71 (75%) showed impaired posterior circulation vasoreactivity (visual evoked flow velocity response ≤14.0%). There was a significant negative correlation between the risk of OSA calculated by STOP-BANG and the breath-holding index (rS=-0.284, P=0.012). The following variables were associated with low anterior circulation vasoreactivity: dyslipidemia (odds ratio: 4.7; 95% CI, 1.5-14.2) and STOP-BANG score (odds ratio: 1.7 per 1-point increase; 95% CI, 1.1-1.5). Conclusions A high risk of OSA and impaired vasoreactivity exists in the population that has had stroke. Dyslipidemia and STOP-BANG sleep apnea risk categories were independently associated with impaired anterior circulation vasoreactivity.
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Affiliation(s)
| | - Thiago Cerqueira-Silva
- Stroke Clinic, Hospital Professor Edgard Santos Federal University of Bahia Salvador Brazil
| | - Alisson L Andrade
- Stroke Clinic, Hospital Professor Edgard Santos Federal University of Bahia Salvador Brazil
| | - Beatriz M M Gonçalves
- Stroke Clinic, Hospital Professor Edgard Santos Federal University of Bahia Salvador Brazil
| | - Camila B Pereira
- Stroke Clinic, Hospital Professor Edgard Santos Federal University of Bahia Salvador Brazil
| | - Iuri F Felix
- Stroke Clinic, Hospital Professor Edgard Santos Federal University of Bahia Salvador Brazil
| | - Leila S B Santos
- Stroke Clinic, Hospital Professor Edgard Santos Federal University of Bahia Salvador Brazil
| | - Louise M Porto
- Stroke Clinic, Hospital Professor Edgard Santos Federal University of Bahia Salvador Brazil
| | - Maria E L Marques
- Stroke Clinic, Hospital Professor Edgard Santos Federal University of Bahia Salvador Brazil
| | - Marilia B Catto
- Stroke Clinic, Hospital Professor Edgard Santos Federal University of Bahia Salvador Brazil
| | - Murilo A Oliveira
- Stroke Clinic, Hospital Professor Edgard Santos Federal University of Bahia Salvador Brazil
| | - Paulo R S P de Sousa
- Stroke Clinic, Hospital Professor Edgard Santos Federal University of Bahia Salvador Brazil
| | - Pedro J R Muiños
- Stroke Clinic, Hospital Professor Edgard Santos Federal University of Bahia Salvador Brazil
| | - Renata M Maia
- Stroke Clinic, Hospital Professor Edgard Santos Federal University of Bahia Salvador Brazil
| | - Saul Schnitman
- Stroke Clinic, Hospital Professor Edgard Santos Federal University of Bahia Salvador Brazil
| | - Jamary Oliveira-Filho
- Stroke Clinic, Hospital Professor Edgard Santos Federal University of Bahia Salvador Brazil
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Squair JW, Lee AH, Sarafis ZK, Chan F, Barak OF, Dujic Z, Day T, Phillips AA. Network analysis identifies consensus physiological measures of neurovascular coupling in humans. J Cereb Blood Flow Metab 2020; 40:656-666. [PMID: 30841780 PMCID: PMC7026847 DOI: 10.1177/0271678x19831825] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Intimate communication between neural and vascular structures is required to match neuronal metabolism to blood flow, a process termed neurovascular coupling. The number of laboratories assessing neurovascular coupling in humans is increasing due to clinical interest in disease states, and basic science interest in a non-anesthetized, non-craniotomized, unrestrained, in vivo model. However, there is a lack of knowledge regarding how best to characterize the neurovascular response. To address this knowledge gap, we have amassed a highly powered human neurovascular coupling dataset, and deployed a network-based approach to reveal the most powerful and consistent metrics for quantifying neurovascular coupling. Using dimensionality reduction, community-based clustering, and majority-voting of traditional metrics (e.g. peak response, time to peak) and non-traditional metrics (e.g. varying time windows, pulsatility), we have identified which of the existing metrics predominantly characterize the neurovascular coupling response, are stable within and across participants, and explain the vast majority of the variance within our dataset of over 300 trials. We then harnessed our empirical approach to generate powerful novel metrics of neurovascular coupling, termed iAmplitude, iRate, and iPulsatility, which increase sensitivity when capturing population differences. These metrics may be useful to optimally understand neurovascular coupling in health and disease.
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Affiliation(s)
- Jordan W Squair
- Departments of Physiology and Pharmacology, Clinical Neurosciences, Cardiac Sciences, University of Calgary, Calgary, Canada.,Hotchkiss Brain Institute, Libin Cardiovascular Institute of Alberta, Cumming School of Medicine, University of Calgary, Calgary, Canada.,International Collaboration on Repair Discoveries, Faculty of Medicine, University of British Columbia, Vancouver, Canada.,MD/PhD Training Program, Faculty of Medicine, University of British Columbia, Vancouver, Canada.,Department of Experimental Medicine, Faculty of Medicine, University of British Columbia, Vancouver, Canada
| | - Amanda Hx Lee
- International Collaboration on Repair Discoveries, Faculty of Medicine, University of British Columbia, Vancouver, Canada.,Department of Experimental Medicine, Faculty of Medicine, University of British Columbia, Vancouver, Canada
| | - Zoe K Sarafis
- International Collaboration on Repair Discoveries, Faculty of Medicine, University of British Columbia, Vancouver, Canada
| | - Franco Chan
- Departments of Physiology and Pharmacology, Clinical Neurosciences, Cardiac Sciences, University of Calgary, Calgary, Canada.,Hotchkiss Brain Institute, Libin Cardiovascular Institute of Alberta, Cumming School of Medicine, University of Calgary, Calgary, Canada
| | - Otto F Barak
- Faculty of Medicine, University of Novi Sad, Novi Sad, Serbia
| | - Zeljko Dujic
- ▪, University of Split School of Medicine, Split, Croatia
| | - Trevor Day
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Canada
| | - Aaron A Phillips
- Departments of Physiology and Pharmacology, Clinical Neurosciences, Cardiac Sciences, University of Calgary, Calgary, Canada.,Hotchkiss Brain Institute, Libin Cardiovascular Institute of Alberta, Cumming School of Medicine, University of Calgary, Calgary, Canada
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10
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Primary involvement of neurovascular coupling in cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy. J Neurol 2019; 266:1782-1788. [PMID: 31028544 DOI: 10.1007/s00415-019-09331-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Revised: 04/14/2019] [Accepted: 04/21/2019] [Indexed: 01/24/2023]
Abstract
BACKGROUND Cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is the most frequent monogenic cause of cerebral ischemia, but reliable biomarkers to monitor the disease are lacking. AIMS AND OBJECTIVES To evaluate cerebral autoregulation (CA), vasoreactivity (VR), and neurovascular coupling (NVC) in CADASIL patients through a battery of dynamic transcranial Doppler tests. METHODS We screened our database for all pre-dementia CADASIL cases. We monitored cerebral blood flow velocity (CBFV) with transcranial Doppler, blood pressure, and expiratory carbon dioxide (CO2) non-invasively. CA was assessed by transfer function from the spontaneous oscillations of blood pressure to CBFV, VR with inhalation of CO2 at 5%, and hyperventilation and NVC by the CBFV response to visual stimulation. RESULTS We included 27 CADASIL patients and 20 healthy controls with similar age and sexes. CA and VR were similar between groups. However, NVC was significantly affected in CADASIL patients, with lower magnitudes of CBFV upsurge (overshoot 19 ± 5 vs 26 ± 6%, p = 0.013; gain 12 ± 7 vs 17 ± 5%, p = 0.003) and altered time behavior during visual stimulation (natural frequency 0.18 ± 0.06 vs 0.24 ± 0.06 Hz, p = 0.005; rate time 0.7 ± 1.7 vs 2.7 ± 3.5 s, p = 0.025). CONCLUSION Our results express a primary and selective involvement of the neurovascular unit in CADASIL rather than a generalized cerebral vasomotor disturbance. Functional cerebrovascular testing could be useful in patient evaluation and monitoring.
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Karacay Ozkalayci S, Nazliel B, Batur Caglayan HZ, Irkec C. Cerebral blood flow velocity in migraine and chronic tension-type headache patients. J Pain Res 2018; 11:661-666. [PMID: 29670392 PMCID: PMC5894724 DOI: 10.2147/jpr.s144183] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Introduction The present study seeks to use transcranial Doppler ultrasound to evaluate cerebral blood flow velocities in anterior and posterior circulation arteries, during an attack-free episode in migraine patients, with and without aura, as well as in chronic tension-type headache patients who were not receiving prophylactic medication. Methods A total of 50 patients (35 female, 15 male) were evaluated during a headache-free episode: 30 migraine patients without aura (mean age: 32±8 years), 10 migraine patients with aura (mean age: 34±4 years), and 10 patients with chronic tension-type headache (mean age: 34±5 years). Results No significant difference was present between anterior, middle, and posterior cerebral and vertebral arteries' blood flow velocities between migraine patients, with and without aura, or in patients with a tension-type headache, and normal controls (p>0.05). However, a significant increase in basilar artery cerebral blood flow velocities relative to controls was present in patients with a tension-type headache (p>0.001). Conclusion It is difficult to predict the main reason for the significant increase in basilar artery blood flow velocities in patients with chronic tension-type headache. It may be due to constriction of conductance or the dilatation of the resistance vessels.
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Affiliation(s)
- S Karacay Ozkalayci
- Department of Neurology, Faculty of Medicine, Gazi University, Ankara, Turkey
| | - B Nazliel
- Department of Neurology, Faculty of Medicine, Gazi University, Ankara, Turkey
| | - H Z Batur Caglayan
- Department of Neurology, Faculty of Medicine, Gazi University, Ankara, Turkey
| | - C Irkec
- Department of Neurology, Faculty of Medicine, Gazi University, Ankara, Turkey
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Malojcic B, Giannakopoulos P, Sorond FA, Azevedo E, Diomedi M, Oblak JP, Carraro N, Boban M, Olah L, Schreiber SJ, Pavlovic A, Garami Z, Bornstein NM, Rosengarten B. Ultrasound and dynamic functional imaging in vascular cognitive impairment and Alzheimer's disease. BMC Med 2017; 15:27. [PMID: 28178960 PMCID: PMC5299782 DOI: 10.1186/s12916-017-0799-3] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Accepted: 01/21/2017] [Indexed: 01/03/2023] Open
Abstract
BACKGROUND The vascular contributions to neurodegeneration and neuroinflammation may be assessed by magnetic resonance imaging (MRI) and ultrasonography (US). This review summarises the methodology for these widely available, safe and relatively low cost tools and analyses recent work highlighting their potential utility as biomarkers for differentiating subtypes of cognitive impairment and dementia, tracking disease progression and evaluating response to treatment in various neurocognitive disorders. METHODS At the 9th International Congress on Vascular Dementia (Ljubljana, Slovenia, October 2015) a writing group of experts was formed to review the evidence on the utility of US and arterial spin labelling (ASL) as neurophysiological markers of normal ageing, vascular cognitive impairment (VCI) and Alzheimer's disease (AD). Original articles, systematic literature reviews, guidelines and expert opinions published until September 2016 were critically analysed to summarise existing evidence, indicate gaps in current knowledge and, when appropriate, suggest standards of use for the most widely used US and ASL applications. RESULTS Cerebral hypoperfusion has been linked to cognitive decline either as a risk or an aggravating factor. Hypoperfusion as a consequence of microangiopathy, macroangiopathy or cardiac dysfunction can promote or accelerate neurodegeneration, blood-brain barrier disruption and neuroinflammation. US can evaluate the cerebrovascular tree for pathological structure and functional changes contributing to cerebral hypoperfusion. Microvascular pathology and hypoperfusion at the level of capillaries and small arterioles can also be assessed by ASL, an MRI signal. Despite increasing evidence supporting the utility of these methods in detection of microvascular pathology, cerebral hypoperfusion, neurovascular unit dysfunction and, most importantly, disease progression, incomplete standardisation and missing validated cut-off values limit their use in daily routine. CONCLUSIONS US and ASL are promising tools with excellent temporal resolution, which will have a significant impact on our understanding of the vascular contributions to VCI and AD and may also be relevant for assessing future prevention and therapeutic strategies for these conditions. Our work provides recommendations regarding the use of non-invasive imaging techniques to investigate the functional consequences of vascular burden in dementia.
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Affiliation(s)
- Branko Malojcic
- Department of Neurology, University Hospital Center Zagreb, Zagreb School of Medicine, Kispaticeva 12, 10000, Zagreb, Croatia.
| | | | - Farzaneh A Sorond
- Department of Neurology, Northwestern University Feinberg School of Medicine Chicago, Chicago, IL, USA
| | - Elsa Azevedo
- Department of Neurology, São João Hospital Center and Faculty of Medicine of University of Porto, Porto, Portugal
| | - Marina Diomedi
- Cerebrovascular Disease Center, Stroke Unit, University of Rome Tor Vergata, Rome, Italy
| | - Janja Pretnar Oblak
- Department of Vascular Neurology and Intensive Therapy, University Medical Center Ljubljana, Ljubljana, Slovenia
| | - Nicola Carraro
- Department of Medical Sciences, Clinical Neurology-Stroke Unit, University Hospital, University of Trieste, Trieste, Italy
| | - Marina Boban
- Department of Neurology, University Hospital Center Zagreb, Zagreb School of Medicine, Kispaticeva 12, 10000, Zagreb, Croatia
| | - Laszlo Olah
- Department of Neurology, University of Debrecen, Debrecen, Hungary
| | - Stephan J Schreiber
- Department of Neurology, Charite - Universitätsmedizin Berlin, Berlin, Germany
| | - Aleksandra Pavlovic
- Neurology Clinic, Clinical Center of Serbia, Faculty of Medicine, University of Belgrade, Belgrade, Serbia
| | - Zsolt Garami
- Methodist DeBakey Heart and Vascular Center, Houston, TX, USA
| | - Nantan M Bornstein
- Neurology Department, Tel Aviv Sourasky Medical Centre, Tel Aviv, Israel
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Viski S, Orgovan D, Szabo K, Rosengarten B, Csiba L, Olah L. Effect of reading on blood flow changes in the posterior cerebral artery in early blind and sighted people--A transcranial Doppler study. J Neurol Sci 2016; 363:132-9. [PMID: 27000238 DOI: 10.1016/j.jns.2016.02.050] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Revised: 02/17/2016] [Accepted: 02/19/2016] [Indexed: 10/22/2022]
Abstract
BACKGROUND Neuroimaging studies proved that Braille reading resulted in visual cortex activation in blind people, however, very few data are available about the measure of flow increase in these subjects. Therefore, we investigated the flow response in the posterior cerebral artery (PCA) of eleven early blind and ten sighted subjects induced by reading Braille and print, respectively. METHODS Two experimental protocols were used in both groups: PCA flow velocity during reading was compared to the resting phase and "NLC" phase (volunteers "read" non-lexical characters; e.g. .,-.:,-.:...,). The use of these experimental protocols allowed to investigate separately the effect of "light stimulus+print reading" versus "print reading alone" in sighted, and "hand/finger movement+Braille reading" versus "Braille reading alone" in blind subjects. RESULTS The flow response in the PCA evoked by "Braille reading alone" in blind (10.5±4.5%) and "print reading alone" in sighted subjects (8.1±3.5%) was similar. The flow increase induced by "hand/finger movement+Braille reading" and by "Braille reading alone" did not differ in blind people, however, "light stimulus+print reading" in sighted subjects caused higher PCA flow increase (25.9±6.9%) than "print reading alone" (8.1±3.5%). CONCLUSION The similar PCA flow response induced by Braille and print reading alone suggested a similar degree of occipital cortex activation in blind and sighted subjects. In sighted people, the 3-times higher flow velocity increase induced by "light stimulus+print reading" compared with "print reading alone" indicated that 2/3 of PCA flow increase during reading was due to the light stimulus and only 1/3 of flow response was caused by reading alone.
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Affiliation(s)
- Sandor Viski
- Department of Neurology, University of Debrecen, Moricz Zs. str. 22, H-4032 Debrecen, Hungary
| | - David Orgovan
- Department of Neurology, University of Debrecen, Moricz Zs. str. 22, H-4032 Debrecen, Hungary
| | - Katalin Szabo
- Department of Neurology, University of Debrecen, Moricz Zs. str. 22, H-4032 Debrecen, Hungary
| | - Bernhard Rosengarten
- Department of Neurology, University of Giessen, Giessen, Amsteg 14, Giessen D-35385, Germany
| | - Laszlo Csiba
- Department of Neurology, University of Debrecen, Moricz Zs. str. 22, H-4032 Debrecen, Hungary
| | - Laszlo Olah
- Department of Neurology, University of Debrecen, Moricz Zs. str. 22, H-4032 Debrecen, Hungary.
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Visually evoked blood flow responses and interaction with dynamic cerebral autoregulation: correction for blood pressure variation. Med Eng Phys 2014; 36:613-9. [PMID: 24507691 DOI: 10.1016/j.medengphy.2014.01.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2012] [Revised: 01/06/2014] [Accepted: 01/15/2014] [Indexed: 11/20/2022]
Abstract
Visually evoked flow responses recorded using transcranial Doppler ultrasonography are often quantified using a dynamic model of neurovascular coupling. The evoked flow response is seen as the model's response to a visual step input stimulus. However, the continuously active process of dynamic cerebral autoregulation (dCA) compensating cerebral blood flow for blood pressure fluctuations may induce changes of cerebral blood flow velocity (CBFV) as well. The effect of blood pressure variability on the flow response is evaluated by separately modeling the dCA-induced effects of beat-to-beat measured blood pressure related CBFV changes. Parameters of 71 subjects are estimated using an existing, well-known second order dynamic neurovascular coupling model proposed by Rosengarten et al., and a new model extending the existing model with a CBFV contributing component as the output of a dCA model driven by blood pressure as input. Both models were evaluated for mean and systolic CBFV responses. The model-to-data fit errors of mean and systolic blood pressure for the new model were significantly lower compared to the existing model: mean: 0.8%±0.6 vs. 2.4%±2.8, p<0.001; systolic: 1.5%±1.2 vs. 2.2%±2.6, p<0.001. The confidence bounds of all estimated neurovascular coupling model parameters were significantly (p<0.005) narrowed for the new model. In conclusion, blood pressure correction of visual evoked flow responses by including cerebral autoregulation in model fitting of averaged responses results in significantly lower fit errors and by that in more reliable model parameter estimation. Blood pressure correction is more effective when mean instead of systolic CBFV responses are used. Measurement and quantification of neurovascular coupling should include beat-to-beat blood pressure measurement.
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15
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Castro P, Santos R, Freitas J, Rosengarten B, Panerai R, Azevedo E. Adaptation of cerebral pressure-velocity hemodynamic changes of neurovascular coupling to orthostatic challenge. ACTA ACUST UNITED AC 2012. [DOI: 10.1016/j.permed.2012.02.052] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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16
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Panerai RB, Salinet ASM, Robinson TG. Contribution of arterial blood pressure and PaCO2 to the cerebrovascular responses to motor stimulation. Am J Physiol Heart Circ Physiol 2012; 302:H459-66. [DOI: 10.1152/ajpheart.00890.2011] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Motor stimulation induces a neurovascular response that can be detected by continuous measurement of cerebral blood flow (CBF). Simultaneous changes in arterial blood pressure (ABP) and PaCO2 have been reported, but their influence on the CBF response has not been quantified. Continuous bilateral recordings of CBF velocity (CBFV), ABP, and end-tidal CO2 (ETCO2) were obtained in 10 healthy middle-aged subjects at rest and during 60 s of repetitive, metronome-controlled (1 Hz) elbow flexion. A multivariate autoregressive-moving average model was adopted to quantify the relationship between beat-to-beat changes in ABP, breath-by-breath ETCO2, and the motor stimulus, represented by the metronome on-off signal (inputs), and the CBFV response to stimulation (output). All three inputs contributed to explain CBFV variance following stimulation. For the ipsi- and contralateral hemispheres, ABP explained 20.3 ± 17.3% ( P = 0.0007) and 19.5 ± 17.2% ( P = 0.01) of CBFV variance, respectively. Corresponding values for ETCO2 and metronome signals were 22.0 ± 24.2% ( P = 0.008), 24.0 ± 24.1% ( P = 0.037), 32.7 ± 22.5% ( P = 0.0015), and 43.2 ± 25.1% ( P = 0.013), respectively. Synchronized population averages suggest that the initial sudden change in CBFV was largely due to ABP, while the influence of ETCO2 was more erratic. The component due to elbow flexion showed a well-defined pattern, with rise time slower than the main CBFV change but reaching a stable plateau after 15 s of stimulation. Identifying and removing the influences of ABP and PaCO2 to motor-induced changes in CBF should lead to more robust estimates of neurovascular coupling and better understanding of its physiological covariates.
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Affiliation(s)
- Ronney B. Panerai
- Department of Cardiovascular Sciences, University of Leicester; and National Institute for Health Research Biomedical Research Unit in Cardiovascular Science, Glenfield Hospital, Leicester, United Kingdom
| | - Angela S. M. Salinet
- Department of Cardiovascular Sciences, University of Leicester; and National Institute for Health Research Biomedical Research Unit in Cardiovascular Science, Glenfield Hospital, Leicester, United Kingdom
| | - Thompson G. Robinson
- Department of Cardiovascular Sciences, University of Leicester; and National Institute for Health Research Biomedical Research Unit in Cardiovascular Science, Glenfield Hospital, Leicester, United Kingdom
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17
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Azevedo E, Mendes A, Seixas D, Santos R, Castro P, Ayres-Basto M, Rosengarten B, Oliveira JP. Functional Transcranial Doppler: Presymptomatic Changes in Fabry Disease. Eur Neurol 2012; 67:331-7. [DOI: 10.1159/000337906] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2011] [Accepted: 02/27/2012] [Indexed: 11/19/2022]
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18
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Autonomic dysfunction affects cerebral neurovascular coupling. Clin Auton Res 2011; 21:395-403. [PMID: 21796357 DOI: 10.1007/s10286-011-0129-3] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2011] [Accepted: 05/17/2011] [Indexed: 10/17/2022]
Abstract
OBJECTIVE Autonomic failure (AF) affects the peripheral vascular system, but little is known about its influence on cerebrovascular regulation. Patients with familial amyloidotic polyneuropathy (FAP) were studied as a model for AF. METHODS Ten mild (FAPm), 10 severe (FAPs) autonomic dysfunction FAP patients, and 15 healthy controls were monitored in supine and sitting positions for arterial blood pressure (ABP) and heart rate (HR) with arterial volume clamping, and for blood flow velocity (BFV) in posterior (PCA) and contralateral middle cerebral arteries (MCA) with transcranial Doppler. Analysis included resting BFV, cerebrovascular resistance parameters (cerebrovascular resistance index, CVRi; resistance area product, RAP; and critical closing pressure, CrCP), and neurovascular coupling through visually evoked BFV responses in PCA (gain, rate time, attenuation, and natural frequency). RESULTS In non-stimulation conditions, in each position, there were no significant differences between the groups, regarding HR, BP, resting BFV, and vascular resistance parameters. Sitting ABP was higher than in supine in the three groups, although only significantly in controls. Mean BFV was lower in sitting in all the groups, lacking statistical significance only in FAPs PCA. CVRi and CrCP increased with sitting in all the groups, while RAP increased in controls but decreased in FAPm and FAPs. In visual stimulation conditions, FAPs comparing to controls had a significant decrease of natural frequency, in supine and sitting, and of rate time and gain in sitting position. INTERPRETATION These results demonstrate that cerebrovascular regulation is affected in FAP subjects with AF, and that it worsens with orthostasis.
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Bedeković MR, Lovrenčić-Huzjan A, Puretić MB, Demarin V. Prolonged mean reaction time in posterior cerebral artery during visual stimulation in patients with severe carotid stenosis. Clin Physiol Funct Imaging 2011; 31:282-7. [PMID: 21672135 DOI: 10.1111/j.1475-097x.2011.01013.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
While the mean increase in flow velocities in posterior cerebral artery (PCA) as a response to visual stimuli is well documented, the data on the reaction time as a measurement of the vasomotor response of the posterior part of the circle of Willis are still sparse. The aim was to assess the visual evoked response in PCA during white light stimulation by means of functional transcranial doppler in patients with severe internal carotid artery (ICA) stenosis, to introduce a real-time haemodynamic changes as a measurement of the effect of severe carotid disease on the posterior circulation. The measurements were taken in 49 right-handed patients with severe ICA stenosis or occlusion and 30 healthy volunteers, simultaneously in left and right PCA using 2-MHz probes, successively in the dark and during the white light stimulation, during three consecutive repetitive periods of 1 min each. Mean values of mean blood flow velocities (MBFV) and mean reaction time (MRT) with and without visual stimuli were analysed. Linear regression analysis showed no statistically significant correlation between the age, MBFV and a degree of left and right carotid stenosis, and MRT in left and right PCA either in the group of healthy subjects or in the group of patients with severe carotid stenosis, in both test conditions. MRT could be an indicator of compromised cerebral circulation in the presence of haemodynamic significant carotid stenosis as well as an additional and independent haemodynamic parameter of the cerebral visual evoked response.
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Affiliation(s)
- Marina Roje Bedeković
- University Department of Neurology, Sestre milosrdnice University Hospital, Zagreb, Croatia.
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20
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Fritzsch C, Rosengarten B, Guschlbauer B, Weiller C, Hetzel A, Reinhard M. Neurovascular coupling and cerebral autoregulation in patients with stenosis of the posterior cerebral artery. J Neuroimaging 2011; 20:368-72. [PMID: 19732298 DOI: 10.1111/j.1552-6569.2009.00424.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Neurovascular coupling and cerebral autoregulation are two brain intrinsic vasoregulative mechanisms that rapidly adjust local cerebral blood flow. This study examined if stenotic disease affects both mechanisms in the posterior cerebral artery. Ten patients with altogether 13 stenosed (≥50%) posterior cerebral artery (PCA) sides were studied. In addition, 6 control persons without a PCA stenosis were examined. Cerebral blood flow velocity was assessed from both PCAs with transcranial Doppler sonography; blood pressure was measured noninvasively via fingerplethysmography. Neurovascular coupling was assessed by a control system approach using a standard visual stimulation paradigm. Cerebral autoregulation dynamics were measured from spontaneous oscillations of blood pressure and cerebral blood flow velocity by transfer function analysis (phase and gain). The parameters of neurovascular coupling and cerebral autoregulation did not show relevant differences between controls, nonstenosed sides, and stenosed sides. The 3 severely stenosed PCA sides showed a trend to a minor functional flow velocity change and attenuation of the neurovascular coupling mechanism in relation to sides with moderate stenosis. Phase and gain were not altered on sides with PCA stenosis. We conclude that in a group of patients with mainly moderate stenosis of the PCA neurovascular coupling and dynamic autoregulation dynamics seem to be unaltered.
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Affiliation(s)
- Carsten Fritzsch
- Department of Neurology, Neurocenter, University of Freiburg, Freiburg, Germany
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21
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Azevedo E, Santos R, Freitas J, Rosas MJ, Gago M, Garrett C, Rosengarten B. Deep brain stimulation does not change neurovascular coupling in non-motor visual cortex: an autonomic and visual evoked blood flow velocity response study. Parkinsonism Relat Disord 2010; 16:600-3. [PMID: 20846894 DOI: 10.1016/j.parkreldis.2010.08.016] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/22/2010] [Revised: 07/24/2010] [Accepted: 08/23/2010] [Indexed: 11/25/2022]
Abstract
BACKGROUND AND PURPOSE In Parkinson's disease (PD) subthalamic nucleus deep brain stimulation (STN-DBS) improves motor function. Also an effect on the neurovascular coupling in motor cortex was reported due to a parallel activation of a subthalamic vasodilator area (SVA). To address this issue further we analysed neurovascular coupling in a non-motor area. METHODS Twenty PD patients selected for bilateral STN-DBS were investigated with functional transcranial Doppler (f-TCD) before and after surgery. Hemodynamic responses to visual stimulation were registered in left posterior cerebral artery (PCA) and analysed with a control-system approach (parameters gain, rate time, attenuation and natural frequency). To exclude autonomic effects of STN-DBS, we also addressed spectrum analysis of heart rate and of systolic arterial blood pressure variability, and baroreceptor gain. Findings in the PD group were compared with healthy age-matched controls. RESULTS PD patients showed no neurovascular coupling changes in PCA territory, compared to controls, and STN-DBS changed neither blood flow regulatory parameters nor autonomic function. CONCLUSIONS Improvement of vasoregulation in some motor cortical areas after STN-DBS might be related to an improved neuronal functional rather than indicating an effect on the neurovascular coupling or autonomic function.
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Affiliation(s)
- Elsa Azevedo
- Department of Neurology, Hospital São João and Faculty of Medicine of University of Porto, Alameda Professor Hernani Monteiro, 4202-451 Porto, Portugal.
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Rey B, Naranjo V, Parkhutik V, Tembl J, Alcañiz M. A new visually evoked cerebral blood flow response analysis using a low-frequency estimation. ULTRASOUND IN MEDICINE & BIOLOGY 2010; 36:383-391. [PMID: 20133037 DOI: 10.1016/j.ultrasmedbio.2009.11.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2009] [Revised: 10/25/2009] [Accepted: 11/03/2009] [Indexed: 05/28/2023]
Abstract
Transcranial Doppler (TCD) has been widely used to monitor cerebral blood flow velocity (BFV) during the performance of cognitive tasks compared with repose periods. Although one of its main advantages is its high temporal resolution, only some of the previous functional TCD studies have focused on the analysis of the temporal evolution of the BFV signal and none of them has performed a spectral analysis of the signal. In this study, maximum BFV data in both posterior cerebral arteries was monitored during a visual perception task (10 cycles of alternating darkness and illumination) for 23 subjects. A peak was located in the low-frequency band of the spectrum of the maximum BFV of each subject both during visual stimulation and repose periods. The frequency of this peak was in the range between 0.037 and 0.098Hz, depending on the subject, the vessel and the experimental condition. The component of the signal at this frequency, which is associated with the slow variations caused by the visual stimuli, was estimated. That way, the variations in BFV caused by the experimental stimuli were isolated from the variations caused by other factors. This low-frequency estimation signal was used to obtain parameters about the temporal evolution and the magnitude variations of the BFV in a reliable way, thus, characterizing the neurovascular coupling of the participants.
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Affiliation(s)
- Beatriz Rey
- Instituto en Bioingeniería y Tecnología Orientada al Ser Humano, Universidad Politécnica de Valencia, Valencia, Spain.
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Hao Q, Wong LK, Lin WH, Leung TW, Kaps M, Rosengarten B. Ethnic Influences on Neurovascular Coupling. Stroke 2010; 41:383-4. [DOI: 10.1161/strokeaha.109.566752] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background and Purpose—
An ethnic extraintracranial difference in atherosclerosis has been well reported, whereas the potential mechanism remains unclear. We aimed to investigate neurovascular coupling in healthy whites and Asians.
Methods —
Twenty volunteers of each ethnicity were recruited to perform a functional transcranial Doppler examination with standardized checkerboard patterns as visual stimulation (3×4, 6×8, and 12×16 checks subtending a visual field section of 18°×24°, flicker rate 1 Hz). Hemodynamic responses in both posterior cerebral arteries were evaluated with a control system approach.
Results—
The rate time, that is, the initial speed of flow velocity adaptation, was significantly lower in Asians leading to an approximately 2-second delayed hemodynamic adaptation. The other hemodynamic parameters and the dependency of hemodynamic responses in regard to the complexity degree of the stimulus were similar between groups.
Conclusion—
The constellation suggests a greater initial mismatch between functionally increased metabolic demand of neurons and adjusted cerebral blood flow in Asians.
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Affiliation(s)
- Qing Hao
- From the Department of Medicine and Therapeutics (Q.H., K.S.W., W.H. Lin, W.H. Leung), The Chinese University of Hong Kong, Hong Kong, China; and the Department of Neurology and Internal Medicine (M.K., B.R.), Justus-Liebig University-Giessen, Giessen, Germany
| | - Lawrence K.S. Wong
- From the Department of Medicine and Therapeutics (Q.H., K.S.W., W.H. Lin, W.H. Leung), The Chinese University of Hong Kong, Hong Kong, China; and the Department of Neurology and Internal Medicine (M.K., B.R.), Justus-Liebig University-Giessen, Giessen, Germany
| | - Wen Hua Lin
- From the Department of Medicine and Therapeutics (Q.H., K.S.W., W.H. Lin, W.H. Leung), The Chinese University of Hong Kong, Hong Kong, China; and the Department of Neurology and Internal Medicine (M.K., B.R.), Justus-Liebig University-Giessen, Giessen, Germany
| | - Thomas W.H. Leung
- From the Department of Medicine and Therapeutics (Q.H., K.S.W., W.H. Lin, W.H. Leung), The Chinese University of Hong Kong, Hong Kong, China; and the Department of Neurology and Internal Medicine (M.K., B.R.), Justus-Liebig University-Giessen, Giessen, Germany
| | - Manfred Kaps
- From the Department of Medicine and Therapeutics (Q.H., K.S.W., W.H. Lin, W.H. Leung), The Chinese University of Hong Kong, Hong Kong, China; and the Department of Neurology and Internal Medicine (M.K., B.R.), Justus-Liebig University-Giessen, Giessen, Germany
| | - Bernhard Rosengarten
- From the Department of Medicine and Therapeutics (Q.H., K.S.W., W.H. Lin, W.H. Leung), The Chinese University of Hong Kong, Hong Kong, China; and the Department of Neurology and Internal Medicine (M.K., B.R.), Justus-Liebig University-Giessen, Giessen, Germany
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Yücel MA, Devor A, Akin A, Boas DA. The Possible Role of CO(2) in Producing A Post-Stimulus CBF and BOLD Undershoot. FRONTIERS IN NEUROENERGETICS 2009; 1:7. [PMID: 20027233 PMCID: PMC2795469 DOI: 10.3389/neuro.14.007.2009] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/08/2009] [Accepted: 10/08/2009] [Indexed: 12/04/2022]
Abstract
Comprehending the underlying mechanisms of neurovascular coupling is important for understanding the pathogenesis of neurodegenerative diseases related to uncoupling. Moreover, it elucidates the casual relation between the neural signaling and the hemodynamic responses measured with various imaging modalities such as functional magnetic resonance imaging (fMRI). There are mainly two hypotheses concerning this mechanism: a metabolic hypothesis and a neurogenic hypothesis. We have modified recent models of neurovascular coupling adding the effects of both NO (nitric oxide) kinetics, which is a well-known neurogenic vasodilator, and CO2 kinetics as a metabolic vasodilator. We have also added the Hodgkin–Huxley equations relating the membrane potentials to sodium influx through the membrane. Our results show that the dominant factor in the hemodynamic response is NO, however CO2 is important in producing a brief post-stimulus undershoot in the blood flow response that in turn modifies the fMRI blood oxygenation level-dependent post-stimulus undershoot. Our results suggest that increased cerebral blood flow during stimulation causes CO2 washout which then results in a post-stimulus hypocapnia induced vasoconstrictive effect.
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Affiliation(s)
- Meryem A Yücel
- Institute of Biomedical Engineering, Boğaziçi University Istanbul, Turkey
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Martens EGHJ, Peeters LLH, Gommer ED, Mess WH, van de Vosse FN, Passos VL, Reulen JPH. The visually-evoked cerebral blood flow response in women with a recent history of preeclampsia and/or eclampsia. ULTRASOUND IN MEDICINE & BIOLOGY 2009; 35:1-7. [PMID: 18845379 DOI: 10.1016/j.ultrasmedbio.2008.08.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2008] [Revised: 07/11/2008] [Accepted: 08/05/2008] [Indexed: 05/26/2023]
Abstract
Several studies provide evidence for altered cerebral hemodynamics during (pre)eclampsia. Whether (pre)eclampsia has a persistent negative impact on cerebral hemodynamics, possibly contributing to an elevated risk of premature stroke, is unknown. The aims of this study were (i) to refine and apply a control system-based method previously introduced by Rosengarten to quantify the visually-evoked blood flow response of the posterior cerebral artery (PCA); and (ii) to test the hypothesis with this method that cerebral hemodynamics in women with a recent history of (pre)eclampsia is abnormal relative to that in parous controls. Hereto, we recorded cerebral blood flow velocity (CBFV) in the PCA by transcranial Doppler (TCD) sonography during cyclic visual stimulation in 15 former preeclamptics, 13 former eclamptics and 13 controls. The typical CBFV response was fitted with the step response of a second-order-linear model enabling quantification by parameters K (gain), zeta (damping), omega (natural frequency), T(v) (rate time) and T(d) (time delay). The method refinement introduced here consisted of response filtering before quantification and of considering the individual instead of group-averaged response patterns. Application of this refinement reduced the fitting errors (1.4 +/- 1.2 vs. 3.2 +/- 1.8, p < 0.01). Intergroup differences in model parameters were not found. Although statistically not significant, a trend was observed that critical damping (zeta>1) occurred more frequently in the combined group of former patients than in the controls (7 of 28 vs.1 of 13, p = 0.16). Critical damping (zeta>1) reflects an abnormal response, which is either compensated for by a rise in rate time ("intermediate"; zeta>1; T(v) > 20) or remains uncompensated ("sluggish"; zeta>1; T(v) < 20). Critical damping increased significantly (p = 0.039) with (pre-)eclampsia-to-test-interval in the PE+E patients with abnormal responses (zeta>1), suggesting that (pre)eclampsia might induce diminishing cerebral hemodynamic function over time. Based on a system-analytical classification approach, the data of this study provide evidence for individual CBFV responses to be abnormal in former (pre)eclamptics compared with controls. Further study is needed to reveal how the abnormal CBFV response classification reflects cerebrovascular dysfunction.
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Affiliation(s)
- E G H J Martens
- Department of Clinical Neurophysiology, University Hospital Maastricht, Maastricht, The Netherlands.
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Rosengarten B, Lutz H, Kaps M. The neurovascular coupling bears properties of a feedforward and feedback regulative mechanism. ULTRASOUND IN MEDICINE & BIOLOGY 2008; 34:1-6. [PMID: 17720302 DOI: 10.1016/j.ultrasmedbio.2007.06.024] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2007] [Revised: 03/01/2007] [Accepted: 06/22/2007] [Indexed: 05/16/2023]
Abstract
Temporal profiles of mediators involved in the neurovascular coupling bear feedforward and feedback characteristics, which are supported by mathematical modeling of evoked hemodynamic responses. However, cerebral autoregulation was expressed as a feedback control system. Therefore, question of overdetermination of the neurovascular coupling model arises. Addressing this issue, we analyzed both models for their appropriateness in describing the neurovascular coupling. Visually evoked flow velocities were recorded from healthy volunteers (aged 24.7 +/- 1.6 SD; 9 females, 11 males) with transcranial Doppler in the posterior cerebral artery. Control system parameters of the two models were specified according to the least-square-fitting technique. Mean square errors between measured and modeled curves and Akaike's information criterion (AIC) supported the feedforward-feedback model. Mean square differences decreased from 27.2 +/- 37.9 to 2.3 +/- 2 and the AIC from 2.7 +/- 0.6 %(2) to 2 +/- 0.3 %(2). The feedforward element increased the accuracy of the control system model in describing the fast initial response. Biologically, the parameter decreases the initial mismatch between the fast neuronal but slow vascular response because of visual activation.
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Affiliation(s)
- Bernhard Rosengarten
- University of Applied Sciences Giessen-Friedberg, Department of Information Science, Giessen, Germany.
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Rosengarten B, Auch D, Kaps M. Effects of initiation and acute withdrawal of statins on the neurovascular coupling mechanism in healthy, normocholesterolemic humans. Stroke 2007; 38:3193-7. [PMID: 17962596 DOI: 10.1161/strokeaha.107.491423] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND AND PURPOSE Recent clinical trials imply increased risk of vascular events after statin withdrawal. There is evidence that this observation relates to an impaired nitric oxide system. The present analysis investigates the effect of initiation and withdrawal of statin therapy on resting and functionally activated cerebral hemodynamics in healthy young volunteers. METHODS Sixteen healthy students (aged 23.7+/-3.3 years, 10 male) were subjected to a placebo-controlled, double-blind crossover study with a washout phase between blocks of 4 weeks. In the verum group, 20 mg pravastatin was taken for 2 weeks followed by 40 mg for 4 weeks. Withdrawal effects were investigated the day after discontinuation. Total cholesterol levels, blood pressure, resting and evoked hemodynamic responses due to a visual stimulation task in the posterior cerebral artery were obtained at baseline and then weekly and the day after discontinuation. RESULTS In the verum group, cholesterol levels significantly decreased after 2 weeks (from 183+/-30 to 150+/-28 mg/dL; P<0.001) and then remained nearly stable (147+/-21 mg/dL after 6 weeks). Blood pressure, resting and evoked hemodynamic responses remained constant throughout the study. The day after statin withdrawal, evoked flow velocity responses were significantly lower (11+/-4% versus 13+/-5% at baseline; P<0.01) indicating inappropriate blood supply of active neurons. CONCLUSIONS Reduction in evoked flow velocity responses reflects reduced nitric oxide bioavailability and therefore supports molecular findings of acute statin withdrawal. Questions arise if the present data might give a link to reports of increased vascular events in patients at vascular risk after acute statin withdrawal.
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Affiliation(s)
- Bernhard Rosengarten
- Department of Neurology, University Clinics of Giessen and Marburg, Am Steg 14, 35392 Giessen, Germany.
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Azevedo E, Rosengarten B, Santos R, Freitas J, Kaps M. Interplay of cerebral autoregulation and neurovascular coupling evaluated by functional TCD in different orthostatic conditions. J Neurol 2007; 254:236-41. [PMID: 17334660 DOI: 10.1007/s00415-006-0338-1] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2006] [Accepted: 06/22/2006] [Indexed: 02/04/2023]
Abstract
BACKGROUND Adequate cerebral blood flow (CBF) is mainly governed by neurovascular coupling (NC) which adapts local CBF to underlying cortical activity,and cerebral autoregulation (CA)that tends to maintain constant CBF despite changes in arterial blood pressure (BP). Since it was suggested that resistance vessels play an important role in both mechanisms, we investigated the irregulative interplay by performing a functional transcranial Doppler(f-TCD) test under different orthostatic conditions. METHODS Fifteen healthy volunteers performed a visual reading test stimulation task after stabilized in sitting, supine and upright position on a tilt table. Simultaneously, BP and heart rate (HR) were recorded by a photoplethysmographic method and CBF velocity was measured with TCD in left posterior cerebral artery, and, as a reference, also in right middle cerebral artery. Evoked flow velocity (FV) responses were evaluated by a control system approach for systolic and diastolic data. Parameters studied were baseline FV with eyes closed, stable FV under stimulation (gain), oscillatory feature (natural frequency) and damping (attenuation) of the control system model, rate time, and also systolic and diastolic BP and HR. ANOVA test was used for comparing the values of variables in different postural settings, inferring statistical significance at a p < 0,05 level. RESULTS Although there was a significant variation on the different orthostatic conditions in systolic (p = 0,027) and diastolic (p = 0,001) BP and HR (p = 0,0001), there was no significant change in the basal or evoked CBF velocities. CONCLUSIONS An intact CA compensates the different orthostatic conditions completely thus allowing an independent regulation of NC according to the metabolic needs of cortical stimulation.
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Affiliation(s)
- Elsa Azevedo
- Department of Neurology, Hospital S. João, University of Porto, Porto 4202-451, Portugal.
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Donaire A, Carreno M, Gómez B, Fossas P, Bargalló N, Agudo R, Falip M, Setoaín X, Boget T, Raspall T, Obach V, Rumiá J. Cortical laminar necrosis related to prolonged focal status epilepticus. J Neurol Neurosurg Psychiatry 2006; 77:104-6. [PMID: 16361606 PMCID: PMC2117425 DOI: 10.1136/jnnp.2004.058701] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Cortical laminar necrosis (CLN) is radiologically defined as high intensity cortical lesions on T1 weighted MRI images following a gyral distribution. Histopathologically, CLN is characterised by pannecrosis of the cortex involving neurones, glial cells, and blood vessels. It has been reported to be associated with hypoxia, metabolic disturbances, drugs, and infections. We present two patients who developed CLN and permanent neurological deficits after prolonged and repeated focal status epilepticus. The possible mechanisms leading to CLN in these patients are discussed, together with the implications of prompt and aggressive treatment in similar cases.
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Affiliation(s)
- A Donaire
- Hospital Clínic de Barcelona, Barcelona, Spain
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Yam AT, Lang EW, Lagopoulos J, Yip K, Griffith J, Mudaliar Y, Dorsch NWC. Cerebral autoregulation and ageing. J Clin Neurosci 2005; 12:643-6. [PMID: 16098757 DOI: 10.1016/j.jocn.2004.08.017] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2004] [Accepted: 08/10/2004] [Indexed: 11/27/2022]
Abstract
Little is known about the effects of ageing on cerebral autoregulation (CA). To examine the relationship between age and CA in adults, we conducted a prospective study using a non-invasive protocol without external stimuli. We studied 32 subjects, aged 23-68 years. They were assigned to a young group (28+/-5 years) and an old group (54+/-8 years). The groups were sex-matched. Transcranial Doppler ultrasonography (TCD) was used to record bilateral middle cerebral artery flow velocities (CBFV, cm/sec). Noninvasive beat-to-beat tonometric arterial blood pressure (ABP) measurement of the radial artery was used to record spontaneous blood pressure fluctuations. The Mx, an index of dynamic cerebral autoregulation (dCA), was calculated from a moving correlation between ABP and CBFV. We did not find a correlation between age and Mx. No statistically significant difference in the Mx between the groups (0.27+/-0.23, young, vs. 0.37+/-0.24, old) was demonstrated. Age does not affect dynamic cerebral autoregulation assessed by the Mx index in healthy adult subjects. This study supports findings from previous papers wherein CA was measured with protocols which require external stimuli. Further studies are needed to determine CA in subjects above 70 years of age.
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Affiliation(s)
- Alan T Yam
- Department of Neurosurgery, Westmead Hospital, Westmead, New South Wales, Australia
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Zaletel M, Strucl M, Pogacnik T, Zvan B. Effects of visual contrast on visual evoked potentials and Doppler signal. Eur J Neurosci 2004; 19:3353-8. [PMID: 15217390 DOI: 10.1111/j.0953-816x.2004.03448.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We studied visually evoked cerebral blood flow responses (VEFR) and visual evoked potentials (VEP) to different visual contrasts and analysed the relationship between them. The records were made from 35 healthy volunteers aged 38.6 +/- 10.1 years. The stimulus was a black-and-white checkerboard with visual contrasts (VC) of 1%, 10% and 100%. The VEFR were measured in the posterior cerebral artery using transcranial Doppler, and the VEP were recorded from the occipital leads. We found the relationship between visual contrast and VEFR (r = 0.79, P < 0.01) as well as between visual contrast and VEP (r = 0.71, P < 0.01). We also found moderate association between the VEP and the VEFR (r = 0.69, P < 0.01). The analysis of the regression slopes between two different age subgroups (P < 0.01) did not show a significant difference (P = 0.020). We concluded that a simultaneous recording of VEFR and VEP to visual contrasts could allow an assessment of neurovascular coupling in humans.
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Affiliation(s)
- Marjan Zaletel
- University Medical Centre Ljubljana, Department of Neurology, Zaloska c. 7, SI-1525, Ljubljana, Slovenia.
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Rosengarten B, Budden C, Osthaus S, Kaps M. Effect of heart rate on regulative features of the cortical activity-flow coupling. Cerebrovasc Dis 2003; 16:47-52. [PMID: 12766362 DOI: 10.1159/000070115] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2002] [Accepted: 08/28/2002] [Indexed: 11/19/2022] Open
Abstract
OBJECTIVE Heart rate plays an important role in compensatory conditions of arterial pressure changes. Very little information, however, exists on its role in the dynamic adjustment of stimulated organ perfusion. We studied the influence of heart rate on the activity-flow coupling mechanism which adapts local cerebral blood flow in accordance with cortical activity. Since it does not affect heart rate or arterial blood pressure by itself, the commonly observed heart rate variability in test conditions was used to compare the flow response between different heart rate groups. For evaluation under stable heart rate conditions we performed a short test paradigm with a transcranial Doppler technique with the necessary high time resolution. METHODS 168 healthy young volunteers (24 +/- 3 years of age) were grouped according to their heart rate in decade steps from 60 to 100 beats/min (mean: 82 +/- 9 beats/min). The visually evoked flow velocity responses in the posterior cerebral artery were evaluated according to a control system approach. Peak systolic and end diastolic data were evaluated separately. RESULTS A correlation analysis between heart rate and baseline flow velocity as well as each of the control system parameters, i.e. gain, attenuation, rate time and natural frequency, revealed no significance. The flow responses did not differ among the heart rate groups as concluded from an ANOVA test. DISCUSSION The increase in heart rate and the possible stress factors responsible for this seem to be of no relevance in regulative features of the activity-flow coupling. The almost identical time course of flow velocity responses among the groups showing a heart rate difference of up to 50% indicates an integrative principle in flow regulation supporting simplified concepts of flow adaptation.
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Affiliation(s)
- B Rosengarten
- Department of Neurology, Faculty of Medicine, Justus Liebig University of Giessen, Germany
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Rosengarten B, Steen-Müller MK, Müller A, Traupe H, Voss RK, Kaps M. Contrast media effect on cerebral blood flow regulation after performance of cerebral or coronary angiography. Cerebrovasc Dis 2003; 16:42-6. [PMID: 12766361 DOI: 10.1159/000070114] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2002] [Accepted: 08/21/2002] [Indexed: 11/19/2022] Open
Abstract
OBJECTIVE The immediate hemodynamic effects of contrast agents are well documented. Less is known about their longer-lasting effects. We investigated the later effect of iopromide on the neurovascular coupling mechanism after the performance of cerebral or coronary angiography. Neurovascular coupling is a fine-tuned and reliable mechanism adapting cerebral blood flow to cortical activity. When performing a visual stimulation and measuring the resultant flow velocity change in the posterior cerebral artery transcranial Doppler has been used to determine vascular integrity. METHODS The visually evoked blood flow velocity response in the posterior cerebral artery was measured with transcranial Doppler before, 1-2 h after and the day after angiography. The overshoot of the flow velocity response and the stable flow velocity level at the end of the stimulation phase were used to compare the different conditions. RESULTS A significantly diminished overshoot was found 1-2 h after angiography only in patients undergoing cerebral angiography. The stable blood flow velocity levels at the end of the stimulation phase remained unchanged in all cases. CONCLUSIONS Our finding demonstrates effects of contrast media on dynamic blood flow regulation of the cerebral vasculature 1-2 h after application of direct contrast agent suggesting a possible concentration effect of the contrast agent. However, since the relative blood flow velocity increase under stable blood flow conditions remained constant, this dynamic alteration does not cause a reduction in cerebral blood flow.
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Affiliation(s)
- B Rosengarten
- Department of Neurology, Justus Liebig University of Giessen, Germany
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Rosengarten B, Osthaus S, Kaps M. Doppler investigation of within-session reproducibility in a visual stimulation task to assess the volunteer-dependent variation. Cerebrovasc Dis 2003; 16:53-60. [PMID: 12766363 DOI: 10.1159/000070116] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2002] [Accepted: 08/21/2002] [Indexed: 11/19/2022] Open
Abstract
OBJECTIVE In functional magnetic resonance imaging (MRI) studies in humans the tightness of activity-flow coupling was questioned due to a notable within-session variability of the signals obtained. To differentiate between moments of volunteer-dependent or technique-inherent variation in hemodynamic MRI measurements a method with a low technique-inherent variation is needed. Therefore, and because temporal features might also be of some relevance, we used the transcranial Doppler method. METHODS In 22 healthy volunteers the flow-velocity response to a visual stimulation task was evaluated. Conditions of 20 s of eye closure were altered with 40 s of silent reading, repeated 10 times. Averaged individual flow-velocity responses were evaluated from conditions of 40 s of stimulation and a 5-second time interval prior to the beginning of stimulation. The averaged data were subtracted from each single recording to calculate the mean squared differences (MSD). Statistical evaluation was performed according to a two-way ANOVA for repeated measures. To obtain additional qualitative data of the flow response, the individual flow curves were evaluated according to a control system approach specifying a second-order linear model. RESULTS The coefficient of variation (COV) of the within-session MSD was 7% for the stimulation phase and 2.9% for the resting phase, whereas the respective COVs were 15 and 8.1% for the interindividual MSDs. The interindividual COVs of control system parameters ranged from 3.6 to 7.6%. The ANOVA resulted in a significant (p < 0.003) difference for the MSD values between stimulation conditions, whereas the test repetition (p = 0.55) and the test for an interaction of repetition and stimulation condition (p = 0.54) revealed no significance. DISCUSSION Confirming the notion of a tight coupling between cortical activity and cerebral blood flow and being indicative of a low technique-inherent variation, we found a high within-session reproducibility in a functional Doppler test.
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Affiliation(s)
- B Rosengarten
- Department of Neurology, Faculty of Medicine, Justus Liebig University of Giessen, Germany
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Rosengarten B, Sperner J, Görgen-Pauly U, Kaps M. Cerebrovascular reactivity in adolescents with migraine and tension-type headache during headache-free interval and attack. Headache 2003; 43:458-63. [PMID: 12752750 DOI: 10.1046/j.1526-4610.2003.03090.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Migraine is a common cause of headache in adolescents. Assuming that the cerebral vasculature is involved in the pathophysiology of migraine, we compared cerebral vasoreactivity in adolescents both during a migraine attack and a headache-free interval. METHODS A functional transcranial Doppler test utilizing a visual stimulation paradigm was undertaken to measure the evoked flow velocity in the posterior cerebral artery of adolescents suffering from a migraine without aura or a tension-type headache. To serve as a control, data previously obtained from age-matched adolescents with no primary headache disorder were used. The flow curves were evaluated by determining the maximal flow velocity increase and by modeling their time course according to a control system analysis. In that analysis, the main dynamic features of the flow response were described mathematically in terms of a control system model of low order. The parameters were time delay, gain, attenuation, rate time, and natural frequency. RESULTS The attenuation parameter (P<.005), indicative of an increased tone of the vessel, and the resting absolute flow velocity (P<.01) both showed a significant increase during an attack in the adolescents with migraine; the gain parameter showed a trend towards similar increase (P =.07). The maximal flow velocity did not increase significantly during an attack. CONCLUSIONS The control system approach utilized here appears to be more sensitive for detecting migraine-associated changes in cerebral vasoreactivity than examination of the maximal flow velocities alone.
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Rosengarten B, Spiller A, Aldinger C, Kaps M. Control system analysis of visually evoked blood flow regulation in humans under normocapnia and hypercapnia. EUROPEAN JOURNAL OF ULTRASOUND : OFFICIAL JOURNAL OF THE EUROPEAN FEDERATION OF SOCIETIES FOR ULTRASOUND IN MEDICINE AND BIOLOGY 2003; 16:169-75. [PMID: 12573785 DOI: 10.1016/s0929-8266(02)00070-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
OBJECTIVE Among other factors, the cerebral blood flow (CBF) is regulated in accordance to the arterial CO(2) tension and the cortical activity. The CO(2) test is commonly used to measure the vascular reserve capacity. Most functional imaging studies rely on the activity-flow coupling (AFC). We aimed to combine both challenges in order to increase the insight into mechanisms of CBF regulation. METHODS Fifteen healthy students underwent a functional transcranial Doppler test using a visual stimulation paradigm: firstly under normocapnia and secondly under conditions of hypercapnia. Hypercapnia was induced by breathing a carbogene gas mixture of 5% CO(2) and 95% O(2). The entire time course of flow velocity adaptation in the posterior cerebral artery (PCA) was analyzed mathematically using a control system approach. RESULTS Resting CBF velocities increased by nearly 26% under conditions of hypercapnia, whereas the slight increase in arterial blood pressure (ABP) and the decrease in the Pourcelot-Pulsatility index (PI) were statistically not significant. From the control system parameters which were time delay, rate time, gain, attenuation and natural frequency, only the parameter rate time, indicative for the initial steepness of flow velocity increase, showed a statistically significant decrease, consistently for the peak systolic and enddiastolic flow velocity data. As concluded from the unchanged gain parameter the absolute amount of blood flow evoked by the same visual stimulus increased also by 26%. CONCLUSION Evaluated by Doppler measurements hypercapnia seems to influence the AFC in two ways: It decreases the steepness of the initial increase in blood flow velocity and enhances the absolute amount of blood flow evoked by the same stimulus.
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Affiliation(s)
- Bernhard Rosengarten
- Department of Neurology, Faculty of Medicine, Justus-Liebig University of Giessen, Am Steg 14, D-35385 Giessen, Germany
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Rosengarten B, Osthaus S, Auch D, Kaps M. Effects of acute hyperhomocysteinemia on the neurovascular coupling mechanism in healthy young adults. Stroke 2003; 34:446-51. [PMID: 12574558 DOI: 10.1161/01.str.0000050661.67548.32] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND AND PURPOSE Hyperhomocysteinemia is a vascular risk factor that infers with the nitric oxide signaling pathway of endothelial vasoregulation. Most investigations in young healthy humans on the peripheral vasculature using a standardized methionine challenge demonstrated altered vascular reactivity. In contrast, the cerebral autoregulation mechanism was shown to be unaffected by the same methionine load. To obtain additional insight into the compensatory range of the cerebral vasculature during a methionine challenge, we tested the neurovascular coupling mechanism that adjusts cerebral blood flow in accordance with cortical activity. METHODS Fifteen healthy young adults (age, 24.7+/-2.3 years; 7 men) were tested with a functional transcranial Doppler test before and 3, 8, and 24 hours after administration of placebo, 20 mg folic acid, 20 mg folic acid and 0.1 g/kg body weight L-methionine, or L-methionine alone. Evoked blood flow response was evaluated according to a control system approach. Plasma concentrations of homocysteine, resting blood flow velocities, and control system parameters of flow velocity change were compared for each time point using a multiple analysis of variance test. RESULTS Homocysteine levels increased significantly compared with baseline (before, 7.6+/-1.9 micromol/L; 3 hours, 22.2+/-6.0 micromol/L [P<0.0001]; 8 hours, 27.9+/-8.6 micromol/L [P<0.0001]; 24 hours, 12.6+/-7.8 micro mol/L [P=NS]). Resting flow velocities and control system parameters remained statistically nonsignificant. CONCLUSIONS Compared with the peripheral vasculature, the regulatory mechanisms controlling adequate cerebral blood flow appear to have a wider compensatory range. This is concluded from statistically nonsignificant results comparing the vascular reactivity in young adults undergoing a standardized methionine challenge. Our data confirm indirectly the reports of high concentrations of homocysteine needed to affect the cerebral vasculature in animal experiments.
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Affiliation(s)
- B Rosengarten
- Department of Neurology, Faculty of Medicine, Justus-Liebig-University of Giessen, Giessen, Germany
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Rosengarten B, Aldinger C, Spiller A, Kaps M. Neurovascular Coupling Remains Unaffected During Normal Aging. J Neuroimaging 2003. [DOI: 10.1111/j.1552-6569.2003.tb00155.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Rosengarten B, Dost A, Kaufmann A, Gortner L, Kaps M. Impaired cerebrovascular reactivity in type 1 diabetic children. Diabetes Care 2002; 25:408-10. [PMID: 11815528 DOI: 10.2337/diacare.25.2.408-a] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- Bernhard Rosengarten
- Department of Neurology, Justus-Liebig-University of Giessen, 35385 Giessen, Germany
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Rosengarten B, Aldinger C, Kaufmann A, Kaps M. Comparison of visually evoked peak systolic and end diastolic blood flow velocity using a control system approach. ULTRASOUND IN MEDICINE & BIOLOGY 2001; 27:1499-1503. [PMID: 11750749 DOI: 10.1016/s0301-5629(01)00464-1] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Transcranial Doppler sonography measures blood flow velocity in basal cerebral vessels with high accuracy. For quantification, time averaged mean blood flow velocities are used most because the peak systolic and end diastolic blood flow velocities mark the velocity extremes of one heart cycle. It is known, from hemodynamic measurements of the neurovascular coupling mechanism, that the end diastolic velocity is more sensitive for change in hemodynamics than the peak systolic velocity. Thus, we used a recently introduced control system approach to compare both indices for their use in functional transcranial Doppler tests focusing on hemodynamics of blood flow velocity change. We enrolled 65 healthy young volunteers without a medical history of cardiovascular risk factors, and performed a visual stimulation test. Peak systolic and end diastolic maximal blood flow velocities were used after transformation to relative data for control-system analysis. Due to Doppler artefacts, 95% of peak systolic and 86% of end diastolic data sets were analyzed. Results showed statistically significant differences for resting blood flow velocity and the control system parameter gain, attenuation and rate time, whereas the parameters' natural frequency and time delay were equal. Increase in relative blood flow velocity in the posterior cerebral artery due to visual-cortical stimulation was higher in end diastolic values than peak systolic data. Using a complex visual stimulation paradigm, the higher sensitivity of the end diastolic index is of no practical use. Being less influenced by Doppler artefacts, the peak systolic velocity index is more feasible for control-system analysis of dynamic blood flow regulation.
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Affiliation(s)
- B Rosengarten
- Department of Neurology, Faculty of Medicine, Justus-Liebig University of Giessen, Giessen, Germany
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