Assessing the effect of unilateral cerebral revascularisation on the vascular reactivity of the non-intervened hemisphere: a retrospective observational study

Advances in moyamoya disease: pathogenesis, diagnosis, and therapeutic interventions

Moyamoya disease (MMD) is a type of cerebrovascular disease characterized by occlusion of the distal end of the internal carotid artery and the formation of collateral blood vessels. Over the past 20 years, the landscape of research on MMD has significantly transformed. In this review, we provide insights into the pathogenesis, diagnosis, and therapeutic interventions in MMD. The development of high-throughput sequencing technology has expanded our understanding of genetic susceptibility, identifying MMD-related genes beyond RNF213, such as ACTA2, DIAPH1, HLA, and others. The genetic susceptibility of MMD to its pathological mechanism was summarized and discussed. Based on the second-hit theory, the influences of inflammation, immunity, and environmental factors on MMD were also appropriately summarized. Despite these advancements, revascularization surgery remains the primary treatment for MMD largely because of the lack of effective in vivo and in vitro models. In this study, 16 imaging diagnostic methods for MMD were summarized. Regarding therapeutic intervention, the influences of drugs, endovascular procedures, and revascularization surgeries on patients with MMD were discussed. Future research on the central MMD vascular abnormalities and peripheral circulating factors will provide a more comprehensive understanding of the pathogenic mechanisms of MMD.

Ramp protocol for non-linear cerebrovascular reactivity with transcranial doppler ultrasound

BACKGROUND

Cerebrovascular reactivity (CVR) reflects the ability of cerebral blood vessels to adjust their diameter in response to vasoactive stimuli, which is crucial for maintaining brain health. Traditional CVR assessments commonly use a two-point measurement, assuming a linear relationship between cerebral blood flow (CBF) and arterial CO2. However, this approach fails to capture non-linear characteristics, particularly the plateaus at extreme CO2 levels.

NEW METHOD

This study introduces a cost-effective, ramp-based end-tidal CO2 (PETCO2) protocol to assess non-linear aspects of CVR. Using transcranial Doppler ultrasound, we monitored blood velocity responses to progressive increases in arterial CO2 levels in eleven healthy adults, covering a spectrum from hypocapnia to hypercapnia.

RESULTS

All eleven participants successfully completed the protocol, with an average PETCO2 range of 26 ± 4 mmHg and blood velocity changes from -29 % to + 50 % relative to baseline. Non-linear CVR characteristics were observed in all subjects. Sigmoid models provided significantly better fits to the CVR data than linear models, while Bayesian approaches followed expected physiological ranges more accurately than least squares regression methods.

COMPARISON WITH EXISTING METHODS

Unlike traditional CVR methods, this ramp protocol captures the full, non-linear CVR profile. The sigmoid modeling approach offers a more accurate representation of cerebrovascular dynamics, particularly at CO2 extremes.

CONCLUSIONS

The PETCO2 ramp protocol with non-linear CVR modeling shows promise as an accessible and reliable tool for assessing CBF dynamics. With high completion rates, straightforward implementation, and low equipment cost, this approach holds significant potential for clinical applications in cerebrovascular health evaluation.

Cognitive dysfunction in Moyamoya disease: latest developments and future directions

Cognitive dysfunction is common in Moyamoya disease (MMD). However, current knowledge of cognitive impairment in MMD is inadequate. In this review, we explored the characteristics of altered cognitive function associated with MMD and offered recommendations aimed at guiding potential research endeavors into the cognitive dysfunction in MMD. Cognitive functions, including executive function, intelligence, memory and so on, show characteristic declines in MMD. The effects of cerebral revascularization surgery on cognitive impairment are controversial. Currently, there is still a lack of relevant research on cognitive impairment. Research on the pathogenesis and etiology associated with Moyamoya disease as well as long-term cohort studies, are important future directions.

BOLD Cerebrovascular Reactivity and NOVA Quantitative MR Angiography in Adult Patients with Moyamoya Vasculopathy Undergoing Cerebral Bypass Surgery

Revascularization surgery for the symptomatic hemisphere with hemodynamic impairment is effective for Moyamoya vasculopathy patients. However, careful patient selection is crucial and ideally supported by advanced quantitative hemodynamic imaging. Recently, blood oxygenation level-dependent cerebrovascular reactivity (BOLD-CVR) and quantitative magnetic resonance angiography with non-invasive optimal vessel analysis (qMRA-NOVA) have gained prominence in assessing these patients. This study aims to present the results of BOLD-CVR and qMRA-NOVA imaging along with the changes in cerebral hemodynamics and flow status following flow augmentation with superficial temporal artery-middle cerebral artery (STA-MCA) bypass in our Moyamoya vasculopathy patient cohort. Symptomatic patients with Moyamoya vasculopathy treated at the Clinical Neuroscience Center of the University Hospital Zurich who underwent hemodynamic and flow imaging (BOLD-CVR and qMRA-NOVA) before and after bypass were included in the analysis. Reduced hemispheric volume flow rates, as well as impaired BOLD-CVR, were measured in all 12 patients with Moyamoya vasculopathy before STA-MCA bypass surgery. Following the surgical procedure, post-operative BOLD-CVR demonstrated a non-significant increase in BOLD-CVR values within the revascularized, symptomatic middle cerebral artery territory and cerebral hemisphere. The results of the statistical tests should be viewed as indicative due to the small sample size. Additionally, post-operative qMRA-NOVA revealed a significant improvement in the hemispheric volume flow rate of the affected hemisphere due to the additional bypass flow rate. Our findings affirm the presence of hemodynamic and flow impairments in the symptomatic hemisphere of the Moyamoya vasculopathy patients. Bypass surgery proves effective in improving both BOLD-CVR impairment and the hemispheric volume flow rate in our patient cohort.

Natural course of hemodynamically stable hemispheres contralateral to operated hemispheres in adult patients with ischemic moyamoya diseases

The necessity of bilateral bypass in adult moyamoya disease (MMD) remains unclear despite its recommendation for pediatric and hemorrhagic cases. We aimed to investigate the natural course of hemodynamically stable unoperated hemispheres after bypass surgery for symptomatic and hemodynamically unstable hemispheres in adult patients with ischemic MMD. Among 288 patients, the mean age at the first operation of the unstable hemispheres was 40.8 ± 12.2 years. The mean follow-up period was 62.9 ± 46.5 months. 45 patients (15.6%) experienced stroke events in the unoperated hemisphere, consisting of hemorrhagic stroke in 8 (2.8%) and ischemic stroke in 37 (12.8%), including progressive transient ischemic attack in 25 (8.7%) and infarction in 12 (4.2%). Among them, 39 patients (13.5%) underwent bypass surgery. The annual risk of total stroke is 3.0%/patient-year, with 2.5% for ischemic stroke and 0.5% for hemorrhagic stroke. The 5- and 10-year cumulative risks of ischemic stroke were 13.4% and 18.3%, respectively, and those of hemorrhagic stroke were each 3.2%. The natural course of hemodynamically stable hemispheres contralateral to the operated ones appeared fairly good. Additional bypass surgery on the unoperated hemispheres should be considered for symptomatic and hemodynamically unstable hemispheres in adult patients with ischemic MMD during the follow-up.

A Systematic Review of the Association Between Dementia Risk Factors and Cerebrovascular Reactivity

Cumulative evidence suggests that impaired cerebrovascular reactivity (CVR), a regulatory response critical for maintaining neuronal health, is amongst the earliest pathological changes in dementia. However, we know little about how CVR is affected by dementia risk, prior to disease onset. Understanding this relationship would improve our knowledge of disease pathways and help inform preventative interventions. This systematic review investigates 59 studies examining how CVR (measured by magnetic resonance imaging) is affected by modifiable, non-modifiable, and clinical risk factors for dementia. We report that non-modifiable risk (older age and apolipoprotein ε4), some modifiable factors (diabetes, traumatic brain injury, hypertension) and some clinical factors (stroke, carotid artery occlusion, stenosis) were consistently associated with reduced CVR. We also note a lack of conclusive evidence on how other behavioural factors such as physical inactivity, obesity, or depression, affect CVR. This review explores the biological mechanisms underpinning these brain- behaviour associations, highlights evident gaps in the literature, and identifies the risk factors that could be managed to preserve CVR in an effort to prevent dementia.

Indirect revascularization vs. non-surgical treatment for Moyamoya disease and Moyamoya syndrome: A comparative effectiveness study

Background

The efficacy of indirect revascularization vs. non-surgical treatment in adults with Moyamoya disease (MMD) and Moyamoya syndrome (MMS) remains controversial.

Objective

To compare the clinical outcomes of indirect revascularization and non-surgical treatments in adult patients with MMD and MMS.

Methods

We collected medical records and follow-up results of adult patients with MMD and MMS who received treatment in the China-Japan Union Hospital of Jilin University between January 2019 and December 2021. A Shapiro-Wilk test, independent sample t-test or Mann-Whitney U-test, and Pearson chi-square test were used to compare baseline variables. The propensity-score analysis was used to compare clinical outcomes of patients with MMD and MMS who underwent indirect revascularization and non-surgical treatments. The color-coded digital subtraction angiography (CC-DSA) was used to quantitatively analyzed the preoperative and postoperative (at 6-month follow-up) images of patients in the surgical group.

Results

A total of 144 patients were included in this study, of whom 37 received indirect revascularization treatment and 107 received non-surgical treatment. The average age of the patients was 58.3 ± 13.4 years. Perioperative complications were observed in eight of the operations. During the follow-up period, a total of 35 stroke events occurred, including two cases (5.4%) in the surgery group and 33 cases (30.8%) in the non-surgery group (p < 0.05). The preoperative mean transit time (MTT) of bypass vessel (superficial temporal artery, STA) was 0.26 ± 0.07, and the postoperative MTT of bypass vessel was 3.0 ± 0.25, and there was no statistical difference between the subgroups.

Conclusion

Indirect revascularization surgery can significantly reduce the recurrent stroke incidence of MMD and MMS patients.

Vascular smooth muscle cell dysfunction in neurodegeneration

Vascular smooth muscle cells (VSMCs) are the key moderators of cerebrovascular dynamics in response to the brain's oxygen and nutrient demands. Crucially, VSMCs may provide a sensitive biomarker for neurodegenerative pathologies where vasculature is compromised. An increasing body of research suggests that VSMCs have remarkable plasticity and their pathophysiology may play a key role in the complex process of neurodegeneration. Furthermore, extrinsic risk factors, including environmental conditions and traumatic events can impact vascular function through changes in VSMC morphology. VSMC dysfunction can be characterised at the molecular level both preclinically, and clinically ex vivo. However the identification of VSMC dysfunction in living individuals is important to understand changes in vascular function at the onset and progression of neurological disorders such as dementia, Alzheimer's disease, and Parkinson's disease. A promising technique to identify changes in the state of cerebral smooth muscle is cerebrovascular reactivity (CVR) which reflects the intrinsic dynamic response of blood vessels in the brain to vasoactive stimuli in order to modulate regional cerebral blood flow (CBF). In this work, we review the role of VSMCs in the most common neurodegenerative disorders and identify physiological systems that may contribute to VSMC dysfunction. The evidence collected here identifies VSMC dysfunction as a strong candidate for novel therapeutics to combat the development and progression of neurodegeneration, and highlights the need for more research on the role of VSMCs and cerebrovascular dynamics in healthy and diseased states.

Quantifying cerebral blood arrival times using hypoxia-mediated arterial BOLD contrast

Cerebral blood arrival and tissue transit times are sensitive measures of the efficiency of tissue perfusion and can provide clinically meaningful information on collateral blood flow status. We exploit the arterial blood oxygen level dependent (BOLD) signal contrast established by precisely decreasing, and then increasing, arterial hemoglobin saturation using respiratory re-oxygenation challenges to quantify arterial blood arrival times throughout the brain. We term this approach the Step Hemoglobin re-Oxygenation Contrast Stimulus (SHOCS). Carpet plot analysis yielded measures of signal onset (blood arrival), global transit time (gTT) and calculations of relative total blood volume. Onset times averaged across 12 healthy subjects were 1.1 ± 0.4 and 1.9 ± 0.6 for cortical gray and deep white matter, respectively. The average whole brain gTT was 4.5 ± 0.9 seconds. The SHOCS response was 1.7 fold higher in grey versus white matter; in line with known differences in tissue-specific blood volume fraction. SHOCS was also applied in a patient with unilateral carotid artery occlusion revealing ipsilateral prolonged signal onset with normal perfusion in the unaffected hemisphere. We anticipate that SHOCS will further inform on the extent of collateral blood flow in patients with upstream steno-occlusive vascular disease, including those already known to manifest reductions in vasodilatory reserve capacity or vascular steal.

Identification of moyamoya disease based on cerebral oxygen saturation signals using machine learning methods

Moyamoya is a cerebrovascular disease with a high mortality rate. Early detection and mechanistic studies are necessary. Near-infrared spectroscopy (NIRS) was used to study the signals of the cerebral tissue oxygen saturation index (TOI) and the changes in oxygenated and deoxygenated hemoglobin concentrations (HbO and Hb) in 64 patients with moyamoya disease and 64 healthy volunteers. The wavelet transforms (WT) of TOI, HbO and Hb signals, as well as the wavelet phase coherence (WPCO) of these signals from the left and right frontal lobes of the same subject, were calculated. Features were extracted from the spontaneous oscillations of TOI, HbO and Hb in five physiological activity-related frequency segments. Machine learning models based on support vector machine (SVM), random forest (RF) and extreme gradient boosting (XGBoost) have been built to classify the two groups. For 20-min signals, the 10-fold cross-validation accuracies of SVM, RF and XGBoost were 87%, 85% and 85%, respectively. For 5-min signals, the accuracies of the three methods were 88%, 88% and 84%, respectively. The method proposed in this article has potential for detecting and screening moyamoya with high proficiency. Evaluating the cerebral oxygenation with NIRS shows great potential in screening moyamoya diseases.

Therapeutic Management of Ocular Ischemia in Takayasu's Arteritis: A Case-Based Systematic Review

Background

Takayasu’s arteritis (TA) is a rare, chronic granulomatous large-vessel vasculitis that can lead to ocular ischemia. Ocular outcomes after therapeutic management in TA remain largely unknown. We herein conduct a case-based systematic review to address the current treatment options in this particular cohort.

Methods

PubMed, Medline, and EMBASE databases were searched pertaining to ocular outcomes after systemic treatment in TA. Studies reporting ocular examinations before and after treatment in TA patients with ocular ischemia were included. Clinical characteristics, therapies, ocular outcomes, and complications were recorded.

Results

A 29-year-old woman with newly diagnosed TA showed dramatic regression of Takayasu’s retinopathy (TR) following balloon angioplasty. Optical coherence tomography angiography (OCTA) was used as a novel strategy for subsequent follow-up. A total of 117 eyes of 66 patients with a median age of 27 years were included for systematic review. TR was the most common ocular manifestation. Oral steroids were prescribed in nearly all patients (n = 65), followed by the use of methotrexate and antiplatelet therapy. Of the patients, 65.8% and 34.2% underwent open surgery and endovascular procedure, respectively. The median follow-up period was 12 weeks (interquartile range 8–33.5). Surgical therapy showed better ocular improvement (including visual and imaging responses) in both acute and chronic vision loss, along with fewer complications than medical therapy alone. In the surgical group, the visual prognosis was significantly better in patients with initial visual acuity better than 20/200 (p = 0.03) and those who underwent surgery before stage III TR (p = 0.01). Ocular outcomes were equivalent in the two surgical approaches.

Conclusion

Clinicians should be familiar with ophthalmic manifestations of this potentially treatable complication in TA. Compared with medical therapy alone, surgical intervention might be a better choice for both acute and chronic vision loss. Surgery is best recommended before the onset of irreversible ischemia to the globe. A combined regimen (oral steroids, immunosuppressants, and antiplatelet drugs) might be effective for those with surgical contradictions or reluctance to an invasive procedure. Physicians should be aware of the importance of ocular examinations, including OCTA, during the diagnosis and follow-up in TA.

Acetazolamide-Challenged Arterial Spin Labeling Detects Augmented Cerebrovascular Reserve After Surgery for Moyamoya

BACKGROUND AND PURPOSE

Cerebrovascular reserve (CVR) inversely correlates with stroke risk in children with Moyamoya disease and may be improved by revascularization surgery. We hypothesized that acetazolamide-challenged arterial spin labeling MR perfusion quantifies augmentation of CVR achieved by revascularization and correlates with currently accepted angiographic scoring criteria.

METHODS

We retrospectively identified pediatric patients with Moyamoya disease or syndrome who received cerebral revascularization at ≤18 years of age between 2012 and 2019 at our institution. Using acetazolamide-challenged arterial spin labeling, we compared postoperative CVR to corresponding preoperative values and to postoperative perfusion outcomes classified by Matsushima grading.

RESULTS

In this cohort, 32 patients (17 males) with Moyamoya underwent 29 direct and 16 indirect extracranial-intracranial bypasses at a median 9.7 years of age (interquartile range, 7.6-15.7). Following revascularization, median CVR increased within the ipsilateral middle cerebral artery territory (6.9 mL/100 g per minute preoperatively versus 16.5 mL/100 g per minute postoperatively, P<0.01). No differences were observed in the ipsilateral anterior cerebral artery (P=0.13) and posterior cerebral artery (P=0.48) territories. Postoperative CVR was higher in the ipsilateral middle cerebral artery territories of patients who achieved Matsushima grade A perfusion, in comparison to those with grades B or C (25.8 versus 17.5 mL, P=0.02). The method of bypass (direct or indirect) did not alter relative increases in CVR (8 versus 3.8 mL/100 g per minute, P=0.7).

CONCLUSIONS

Acetazolamide-challenged arterial spin labeling noninvasively quantifies augmentation of CVR following surgery for Moyamoya disease and syndrome.

Imaging methods for surgical revascularization in patients with moyamoya disease: an updated review

Neuroimaging is crucial in moyamoya disease (MMD) for neurosurgeons, during pre-surgical planning and intraoperative navigation not only to maximize the success rate of surgery, but also to minimize postsurgical neurological deficits in patients. This is a review of recent literatures which updates the clinical use of imaging methods in the morphological and hemodynamic assessment of surgical revascularization in patients with MMD. We aimed to assist surgeons in assessing the status of moyamoya vessels, selecting bypass arteries, and monitoring postoperative cerebral perfusion through the latest imaging technology.

Intraoperative BOLD-fMRI Cerebrovascular Reactivity Assessment

Blood oxygenation-level dependent cerebrovascular reactivity (BOLD-CVR) has gained attention in recent years as an effective way to investigate CVR, a measure of the hemodynamic state of the brain, with high spatial and temporal resolution. An association between impaired CVR and diverse pathologies has been observed, especially in ischemic cerebrovascular diseases and brain gliomas. The ability to obtain this information intraoperatively is novel and has not been widely tested. We report our first experience with this intraoperative technique in vascular and oncologic neurosurgical patients, discuss the results of its feasibility, and the possible developments of the intraoperative employment of BOLD-CVR.

Differential regional cerebral blood flow reactivity to alterations in end-tidal gases in healthy volunteers

PURPOSE

Anesthesia is associated with alterations in end-tidal (ET) respiratory gases from the awake state. These alterations result in marked vasoactive changes in regional cerebral blood flow (rCBF). Altered regional cerebrovascular reactivity (rCVR) is linked to neurologic dysfunction. We examined these differences in reactivity from prior work by focusing on the ratio of vasoconstriction with hyperoxia/hypocapnia (HO/hc):vasodilation with hypercapnia (HC) using magnetic resonance imaging pseudo-continuous arterial spin labelling (pCASL) to measure rCBF and compare rCVR The distribution and magnitude of these ratios could provide insights into rCBF during clinical anesthesia and inform future research into the origins of postoperative delirium (POD).

METHODS

Ten healthy subjects underwent cerebral blood flow (CBF) studies using pCASL with computer-controlled delivery of ET gases to assess flow effects of hyperoxia, hypercapnia, and hyperoxia/hypocapnia as part of a larger study into cerebrovascular reactivity. The vasoconstrictor stimulus was compared with the vasodilator stimulus by the ratio HO/hc:HC.

RESULTS

Hyperoxia minimally decreased whole brain CBF by - 0.6%/100 mm Hg increase in ETO₂. Hypercapnia increased CBF by +4.6%/mm Hg carbon dioxide (CO₂) and with HO/hc CBF decreased by - 5.1%/mm Hg CO₂. The brain exhibited markedly different rCVR-regional HO/hc:HC ratios varied from 7.2:1 (greater response to vasoconstriction) to 0.49:1 (greater response to vasodilation). Many of the ratios greater than 1, where vasoconstriction predominated, were seen in regions associated with memory, cognition, and executive function, including the entorhinal cortex, hippocampus, parahippocampus, and dorsolateral prefrontal cortex.

CONCLUSIONS

In awake humans, marked rCBF changes occurred with alterations in ET respiratory gases common under anesthesia. Such heterogeneous reactivity may be relevant to future studies to identify those at risk of POD.

Development and validation of a risk scoring model for postoperative adult moyamoya disease

OBJECTIVE

The current grading system for moyamoya disease (MMD) is focused on angiographic studies with limited clinical application. The authors aimed to determine relevant factors that may impact postoperative outcome and establish a scoring system to predict the functional outcome.

METHODS

Adult patients with MMD who underwent treatment between 1998 and 2016 were included. Factors such as age, sex, comorbidity, smoking, MMD family history, initial presentation, multimodal imaging modalities, and types of surgical revascularization were thoroughly reviewed. These factors were analyzed to determine possible risk factors related to unfavorable 6-month postoperative outcomes using the modified Rankin Scale (mRS) (unfavorable: mRS score ≥ 3). A scoring system was developed using these independent risk factors to predict the outcome and validated using prospectively collected data from multiple centers between 2017 and 2018.

RESULTS

Of 302 patients for whom applications were submitted, 260 patients (321 hemispheres) met the diagnostic criteria. In multivariate analysis, hyperlipidemia, smoking, cerebral infarction on preoperative CT or MRI, and moderately to severely reduced regional cerebrovascular reserve results from Diamox SPECT were significantly related to unfavorable outcome. The authors developed a scoring system and stratified patients into risk groups according to their scores: low-risk (score 0-3), intermediate-risk (score 4-6), and high-risk (score 7-9) groups. This model demonstrated both good discrimination and calibration using C-statistics and the Hosmer-Lemeshow goodness-of-fit test showing 0.812 (95% CI 0.743-0.881) (p = 0.568) for the development and 0.954 (95% CI 0.896-1) (p = 0.097) for the temporal and external validation cohort.

CONCLUSIONS

The authors' scoring system is readily adoptable to predict the postoperative outcome for MMD. Their data revealed the importance of smoking and hyperlipidemia, which were the only modifiable factors included in the scoring system. The authors validated their scoring system both internally and externally and maintained good performance, highlighting the system's generalizability and reliability.

Contralateral improvement of cerebrovascular reactivity and TIA frequency after unilateral revascularization surgery in moyamoya vasculopathy

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Contralateral cerebrovascular reactivity may improve after unilateral surgery in moyamoya.

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TIA frequency from the contralateral hemisphere can decrease after unilateral moyamoya surgery.

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These findings support staged rather than direct bilateral surgery in moyamoya.

Objective

Moyamoya vasculopathy is a rare, often bilateral disease characterized by progressive stenosis and occlusion of the distal internal carotid artery, leading to a progressive deterioration of cerebrovascular reactivity (CVR) and increased risk of transient ischemic attacks (TIAs), infarction and hemorrhage. Surgical revascularization is a widely accepted symptomatic treatment, often performed bilaterally in one or two stages. To possibly further optimize treatment strategy, we investigated the effect of unilateral revascularization surgery on the CVR of, and TIA frequency originating from, the contralateral hemisphere.

Methods

From our database of 143 moyamoya vasculopathy patients we selected those with bilateral disease, who underwent hemodynamic imaging ([15O]H2O positron emission tomography (PET)-CT with acetazolamide challenge) before and 14 months (median) after unilateral revascularization. We evaluated CVR in three regions per hemisphere, and averaged these per hemisphere for statistical comparison. Conservatively treated patients were showed as a comparison group. To examine TIA frequency, we selected patients who presented with TIAs that (also) originated from the contralateral – not to be operated – hemisphere. We scored changes in CVR and TIA frequency of the ipsilateral and contralateral hemisphere over time.

Results

Seven surgical and seven conservative patients were included for CVR comparison. Of the 20 scored contralateral regions in the surgical group, 15 showed improved CVR after unilateral revascularization, while 5 remained stable. The averaged scores improved significantly for both hemispheres. In conservatively treated patients, however, only 3 of the 20 scored regions improved in the least-affected (contralateral) hemispheres, and 9 deteriorated. From the 6 patients with contralateral TIAs at presentation, 4 had a decreased TIA frequency originating from the contralateral hemisphere after unilateral surgery, while 2 patients remained stable.

Conclusion

Both CVR and TIA frequency in the contralateral hemisphere can improve after unilateral revascularization surgery in bilateral MMV.

Distinct Cerebrovascular Reactivity Patterns for Brain Radiation Necrosis

Background: Current imaging-based discrimination between radiation necrosis versus recurrent glioblastoma contrast-enhancing lesions remains imprecise but is paramount for prognostic and therapeutic evaluation. We examined whether patients with radiation necrosis exhibit distinct patterns of blood oxygenation-level dependent fMRI cerebrovascular reactivity (BOLD-CVR) as the first step to better distinguishing patients with radiation necrosis from recurrent glioblastoma compared with patients with newly diagnosed glioblastoma before surgery and radiotherapy. Methods: Eight consecutive patients with primary and secondary brain tumors and a multidisciplinary clinical and radiological diagnosis of radiation necrosis, and fourteen patients with a first diagnosis of glioblastoma underwent BOLD-CVR mapping. For all these patients, the contrast-enhancing lesion was derived from high-resolution T1-weighted MRI and rendered the volume-of-interest (VOI). From this primary VOI, additional 3 mm concentric expanding VOIs up to 30 mm were created for a detailed perilesional BOLD-CVR tissue analysis between the two groups. Receiver operating characteristic curves assessed the discriminative properties of BOLD-CVR for both groups. Results: Mean intralesional BOLD-CVR values were markedly lower in radiation necrosis than in glioblastoma contrast-enhancing lesions (0.001 ± 0.06 vs. 0.057 ± 0.05; p = 0.04). Perilesionally, a characteristic BOLD-CVR pattern was observed for radiation necrosis and glioblastoma patients, with an improvement of BOLD-CVR values in the radiation necrosis group and persisting lower perilesional BOLD-CVR values in glioblastoma patients. The ROC analysis discriminated against both groups when these two parameters were analyzed together (area under the curve: 0.85, 95% CI: 0.65-1.00). Conclusions: In this preliminary analysis, distinctive intralesional and perilesional BOLD-cerebrovascular reactivity patterns are found for radiation necrosis.

Age corrected changes in intracranial hemodynamics after carotid endarterectomy

BACKGROUND

Transcranial Doppler ultrasound (TCD) is a frequently used method to monitor brain perfusion during and following carotid endarterectomy (CEA). Our aim was to define the normally occurring changes of intracranial hemodynamics in patients undergoing CEA measuring recently developed TCD parameters.

METHODS

A retrospective, single-center cohort study was performed. Patients undergoing CEA were evaluated pre- and postoperatively from day 0 to day 3 measuring middle cerebral artery flow velocity (MCAFV). The following parameters were analyzed: the first systolic peak (Sys1), the second systolic peak (Sys2) and diastolic flow velocity at a fixed time after heartbeat onset (Dias@560). These parameters linearly decrease with age and were, therefore, transformed to Z-scores.

RESULTS

Three hundred eighteen patients were included with a mean age of 70.8 years. Most patients were male (71%). Compared to preoperatively, the Z-scores of Sys1 and Sys2 were larger on postoperative day 3: +1.12 standard deviation (SD) or 16.0 cm/s (CI: 0.93 to 1.32; P<0.001) and +0.55 SD or 7.8 cm/s (CI: 0.35 to 0.74; P<0.001), respectively. The Z-score for Dias@560 was smaller than preoperatively: -0.23 SD or -1.9 cm/s (CI: -0.41 to -0.05, P=0.015).

CONCLUSIONS

Under normal circumstances Sys1 profits more from CEA than Sys2, whilst diastolic flow velocity decreases. This indicates a return to normal arteriolar vascular resistance. Carefully describing normal changes in MCAFV, may in future enable discrimination of abnormalities, such as hyperperfusion syndrome.

Cerebrovascular Reactivity Measurement Using Magnetic Resonance Imaging: A Systematic Review

Cerebrovascular reactivity (CVR) magnetic resonance imaging (MRI) probes cerebral haemodynamic changes in response to a vasodilatory stimulus. CVR closely relates to the health of the vasculature and is therefore a key parameter for studying cerebrovascular diseases such as stroke, small vessel disease and dementias. MRI allows in vivo measurement of CVR but several different methods have been presented in the literature, differing in pulse sequence, hardware requirements, stimulus and image processing technique. We systematically reviewed publications measuring CVR using MRI up to June 2020, identifying 235 relevant papers. We summarised the acquisition methods, experimental parameters, hardware and CVR quantification approaches used, clinical populations investigated, and corresponding summary CVR measures. CVR was investigated in many pathologies such as steno-occlusive diseases, dementia and small vessel disease and is generally lower in patients than in healthy controls. Blood oxygen level dependent (BOLD) acquisitions with fixed inspired CO₂ gas or end-tidal CO₂ forcing stimulus are the most commonly used methods. General linear modelling of the MRI signal with end-tidal CO₂ as the regressor is the most frequently used method to compute CVR. Our survey of CVR measurement approaches and applications will help researchers to identify good practice and provide objective information to inform the development of future consensus recommendations.

The value of a shorter-delay arterial spin labeling protocol for detecting cerebrovascular impairment

Background

The aim of this study was to determine the relationship between blood oxygen level dependent (BOLD) cerebrovascular reactivity (CVR) and cerebral blood flow (CBF) obtained from arterial spin labeling (ASL) using different post labeling delays (PLD).

Methods

Forty-two patients with steno-occlusive diseases and impaired CVR were divided into two groups, one scanned with a 1.5-second (1.5-s) and the other with a 2.5-second (2.5-s) PLD ASL protocol. For all patients, a region of interest (ROI) was drawn around the CVR impairment. This affected ROI was then left-right flipped across the brain midline to obtain the control ROI. For both groups, the difference in grey matter CVR between affected and control ROI was first tested to confirm significance. The average grey matter CBF of affected and control ROIs were then compared. The same analysis method was used to compare affected and control hemispheres.

Results

In both groups of 1.5-s and 2.5-s PLD, CVR values in the affected ROI (-0.049±0.055 and -0.042±0.074%/mmHg, respectively) were significantly lower compared to that in the control ROI (0.152±0.054 and 0.152±0.053%/mmHg, respectively, P<0.0001). In the group with the 1.5-s PLD, CBF in the affected ROI (37.62±11.37 mL/100 g/min) was significantly lower compared to CBF in the control ROI (44.13±11.58 mL/100 g/min, P<0.05). However, in the group with the 2.5-s PLD, no significant differences could be seen between CBF in the affected ROI (40.50±14.82 mL/100 g/min) and CBF in the control ROI (39.68±12.49 mL/100 g/min, P=0.73). In the hemisphere-based analysis, CBF was significantly lower in the affected side than in the control side for the group with the 1.5-s PLD (P<0.05) when CVR was impaired (P<0.0001), but not for the group with the 2.5-s PLD (P=0.49).

Conclusions

In conclusion, our study reveals and highlights the value of a shorter-PLD ASL protocol, which is able to reflect CVR impairment. At the same time, we offer a better understanding of the relationship between BOLD CVR and CBF obtained from ASL.

The Effect of Extracranial-to-Intracranial Bypass on Cerebral Vasoreactivity: A 4D Flow MRI Pilot Study

BACKGROUND AND PURPOSE

Extracranial-to-intracranial (EC-IC) surgical bypass improves cerebral blood flow (CBF) and cerebrovascular vasoreactivity (CVR) for patients with carotid occlusion. Bypass graft patency and contribution of the graft to the postoperative increase in CVR are challenging to assess. To assess the effectiveness of 4D flow magnetic resonance imaging (MRI) to evaluate bypass graft patency and flow augmentation through the superficial temporal artery (STA) before and after EC-IC bypass.

METHODS

Three consecutive patients undergoing EC-IC bypass for carotid occlusion were evaluated pre- and postoperatively using CVR testing with pre- and poststimulus 4D flow-MRI for assessment of the bypass graft and intracranial vasculature.

RESULTS

Preoperatively, 2 patients (patients 1 and 3) did not augment flow through either native STA. The third, who had evidence of extensive native EC-IC collateralization on digital subtraction angiography (DSA), did augment flow through the STA preoperatively (CVR = 1). Postoperatively, all patients demonstrated CVR > 1 on the side of bypass. The patient who had CVR > 1 preoperatively demonstrated the greatest increase in resting postoperative graft flow (from 40 to 130 mL/minute), but the smallest CVR, with a poststimulus graft flow of 160 mL/minute (CVR = 1.2). The 2 patients who did not demonstrate augmentation of graft flow preoperatively augmented postoperatively from 10 to 20 mL/minute (CVR = 2.0) and 10-80 mL/minute (CVR = 8.0), respectively. Intracranial flow was simultaneously interrogated. Two patients demonstrated mild reductions in resting flow velocities in all interrogated vessels immediately following bypass. The patient who underwent CVR testing on postoperative day 48 demonstrated a stable or increased flow rate in most intracranial vessels.

CONCLUSION

Four-dimensional flow MRI allows for noninvasive, simultaneous interrogation of the intra- and extracranial arterial vasculature during CVR testing, and reveals unique paradigms in cerebrovascular physiology. Observing these flow patterns may aid in improved patient selection and more detailed postoperative evaluation for patients undergoing EC-IC bypass.

Feasibility and safety of intraoperative BOLD functional MRI cerebrovascular reactivity to evaluate extracranial-to-intracranial bypass efficacy

Blood oxygenation level-dependent functional MRI cerebrovascular reactivity (BOLD-CVR) is a contemporary technique to assess brain tissue hemodynamic changes after extracranial- intracranial (EC-IC) bypass flow augmentation surgery. The authors conducted a preliminary study to investigate the feasibility and safety of intraoperative 3-T MRI BOLD-CVR after EC-IC bypass flow augmentation surgery. Five consecutive patients selected for EC-IC bypass revascularization underwent an intraoperative BOLD-CVR examination to assess early hemodynamic changes after revascularization and to confirm the safety of this technique. All patients had a normal postoperative course, and none of the patients exhibited complications or radiological alterations related to prolonged anesthesia time. In addition to intraoperative flow measurements of the bypass graft, BOLD-CVR maps added information on the hemodynamic status and changes at the brain tissue level. Intraoperative BOLD-CVR is feasible and safe in patients undergoing EC-IC bypass revascularization. This technique can offer immediate hemodynamic feedback on brain tissue revascularization after bypass flow augmentation surgery.

Brain BOLD MRI O2 and CO2 stress testing: implications for perioperative neurocognitive disorder following surgery

Background

Mechanical ventilation to alter and improve respiratory gases is a fundamental feature of critical care and intraoperative anesthesia management. The range of inspired O₂ and expired CO₂ during patient management can significantly deviate from values in the healthy awake state. It has long been appreciated that hyperoxia can have deleterious effects on organs, especially the lung and retina. Recent work shows intraoperative end-tidal (ET) CO₂ management influences the incidence of perioperative neurocognitive disorder (POND). The interaction of O₂ and CO₂ on cerebral blood flow (CBF) and oxygenation with alterations common in the critical care and operating room environments has not been well studied.

Methods

We examine the effects of controlled alterations in both ET O₂ and CO₂ on cerebral blood flow (CBF) in awake adults using blood oxygenation level-dependent (BOLD) and pseudo-continuous arterial spin labeling (pCASL) MRI. Twelve healthy adults had BOLD and CBF responses measured to alterations in ET CO₂ and O₂ in various combinations commonly observed during anesthesia.

Results

Dynamic alterations in regional BOLD and CBF were seen in all subjects with expected and inverse brain voxel responses to both stimuli. These effects were incremental and rapid (within seconds). The most dramatic effects were seen with combined hyperoxia and hypocapnia. Inverse responses increased with age suggesting greater risk.

Conclusions

Human CBF responds dramatically to alterations in ET gas tensions commonly seen during anesthesia and in critical care. Such alterations may contribute to delirium following surgery and under certain circumstances in the critical care environment.

Trial registration

ClincialTrials.gov NCT02126215 for some components of the study. First registered April 29, 2014.

Factors related to improvement of cerebrovascular reserve after superficial temporal artery to middle cerebral artery anastomosis for patients with atherosclerotic steno-occlusive disease

BACKGROUND

This study aimed to investigate factors related to improvement of hemodynamics and evaluated the usefulness of intraoperative Doppler for predicting postoperative hemodynamics in patients with cerebrovascular atherosclerotic steno-occlusive disease (CASD) of the internal carotid artery (ICA) or middle cerebral artery (MCA) who were treated with extracranial-intracranial (EC-IC) bypass surgery.

METHOD

Forty-eight patients with CASD of the ICA or MCA who were treated by superficial temporal artery to middle cerebral artery bypass with a follow-up longer than 12 months were enrolled. Repeated transient ischemic attack or completed ischemic stroke was observed under optimal medical therapy in all patients. Intraoperative blood flow velocity of the MCA was evaluated by a Doppler flowmeter. Cerebral blood flow and cerebrovascular reserve (CVR) were evaluated using N-isopropyl-[¹²³I] p-iodoamphetamine (IMP) single photon emission computed tomography (SPECT) preoperatively and 3 months after surgery. Imaging and clinical data were retrospectively reviewed.

RESULTS

CVR was significantly increased postoperatively (p = 0.03). One year after the operation, two (4.2%) patients developed cerebral infarction. The change in MCA flow velocity just after anastomosis compared with pre-anastomosis proximal and distal of the anastomosis site was a median of 3.0 and 2.6 times, respectively. However, there was no significant association between changes in intraoperative MCA flow velocity and postoperative CVR. Multivariate analysis showed that the presence of a lower estimated glomerular filtration rate (eGFR) was an independent risk factor for a decrease in CVR (p = 0.036).

CONCLUSIONS

A higher eGFR might have prognostic value for improvement in CVR after EC-IC bypass surgery in patients with CASD and misery perfusion.

Neuroimaging of vascular reserve in patients with cerebrovascular diseases

Cerebrovascular reactivity, defined broadly as the ability of brain parenchyma to adjust cerebral blood flow in response to altered metabolic demand or a vasoactive stimulus, is being measured with increasing frequency and may have a use for portending new or recurrent stroke risk in patients with cerebrovascular disease. The purpose of this review is to outline (i) the physiological basis of variations in cerebrovascular reactivity, (ii) available approaches for measuring cerebrovascular reactivity in research and clinical settings, and (iii) clinically-relevant cerebrovascular reactivity findings in the context of patients with cerebrovascular disease, including atherosclerotic arterial steno-occlusion, non-atherosclerotic arterial steno-occlusion, anemia, and aging. Literature references summarizing safety considerations for these procedures and future directions for standardizing protocols and post-processing procedures across centers are presented in the specific context of major unmet needs in the setting of cerebrovascular disease.

Hypercapnic BOLD MRI compared to H215O PET/CT for the hemodynamic evaluation of patients with Moyamoya Disease

Background and purpose

Patients with Moyamoya Disease (MMD) need hemodynamic evaluation of vascular territories at risk of stroke. Today's investigative standards include H₂¹⁵O PET/CT with pharmacological challenges with acetazolamide (ACZ). Recent developments suggest that CO₂-triggered blood‑oxygen-level-dependent (BOLD) functional MRI might provide comparable results to current standard methods for evaluation of territorial hemodynamics, while being a more widely available and easily implementable method. This study examines results of a newly developed quantifiable analysis algorithm for CO₂-triggered BOLD MRI in Moyamoya patients and correlates the results with H₂¹⁵O PET/CT with ACZ challenge to assess comparability between both modalities.

Methods

CO₂-triggered BOLD MRI was performed and compared to H₂¹⁵O PET/CT with ACZ challenge in patients with angiographically proven MMD. Images of both modalities were analyzed retrospectively in a blinded, standardized fashion by visual inspection, as well as with a semi-quantitative analysis using stimuli-induced approximated regional perfusion-weighted data and BOLD-signal changes with reference to cerebellum.

Results

20 consecutive patients fulfilled the inclusion criteria, a total of 160 vascular territories were analyzed retrospectively. Visual analysis (4-step visual rating system) of standardized, color-coded cerebrovascular reserve/reactivity maps showed a very strong correlation (Spearman's rho = 0.9, P < 0.001) between both modalities. Likewise, comparison of approximated regional perfusion changes across vascular territories (normalized to cerebellar change) reveal a highly significant correlation between both methods (Pearson's r = 0.71, P < 0.001).

Conclusions

The present analysis indicates that CO₂-triggered BOLD MRI is a very promising tool for the hemodynamic evaluation of MMD patients with results comparable to those seen in H₂¹⁵O PET/CT with ACZ challenge. It therefore holds future potential in becoming a routine examination in the pre- and postoperative evaluation of MMD patients after further prospective evaluation.

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Non-invasive cerebrovascular reactivity measurement with BOLD MRI.

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CO₂-triggered BOLD MRI correlates strongly with H₂¹⁵O PET/CT with ACZ challenge

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Widely-available tool for the hemodynamic evaluation of Moyamoya patients.

Improved White Matter Cerebrovascular Reactivity after Revascularization in Patients with Steno-Occlusive Disease

BACKGROUND AND PURPOSE

One feature that patients with steno-occlusive cerebrovascular disease have in common is the presence of white matter (WM) lesions on MRI. The purpose of this study was to evaluate the effect of direct surgical revascularization on impaired WM cerebrovascular reactivity in patients with steno-occlusive disease.

MATERIALS AND METHODS

We recruited 35 patients with steno-occlusive disease, Moyamoya disease (n = 24), Moyamoya syndrome (n = 3), atherosclerosis (n = 6), vasculitis (n = 1), and idiopathic stenosis (n = 1), who underwent unilateral brain revascularization using a direct superficial temporal artery-to-MCA bypass (19 women; mean age, 45.8 ± 16.5 years). WM cerebrovascular reactivity was measured preoperatively and postoperatively using blood oxygen level-dependent (BOLD) MR imaging during iso-oxic hypercapnic changes in end-tidal carbon dioxide and was expressed as %Δ BOLD MR signal intensity per millimeter end-tidal partial pressure of CO₂.

RESULTS

WM cerebrovascular reactivity significantly improved after direct unilateral superficial temporal artery-to-middle cerebral artery (STA-MCA) bypass in the revascularized hemisphere in the MCA territory (mean ± SD, -0.0005 ± 0.053 to 0.053 ± 0.046 %BOLD/mm Hg; P < .0001) and in the anterior cerebral artery territory (mean, 0.0015 ± 0.059 to 0.021 ± 0.052 %BOLD/mm Hg; P = .005). There was no difference in WM cerebrovascular reactivity in the ipsilateral posterior cerebral artery territory nor in the vascular territories of the nonrevascularized hemisphere (P < .05).

CONCLUSIONS

Cerebral revascularization surgery is an effective treatment for reversing preoperative cerebrovascular reactivity deficits in WM. In addition, direct-STA-MCA bypass may prevent recurrence of preoperative symptoms.

Long-term changes in cerebrovascular reactivity following EC-IC bypass for intracranial steno-occlusive disease

The purpose of this retrospective observational study is to investigate the long-term changes in cerebrovascular reactivity (CVR) as a measure of cerebral hemodynamics in patients with intracranial steno-occlusive disease (IC-SOD) after they have undergone an Extracranial-intracranial (EC-IC) bypass. Twenty-six patients suffering from IC-SOD were selected from our CVR database. Nineteen patients underwent unilateral and 7 underwent bilateral revascularization. CVR measurements were done using BOLD-MRI and precisely controlled CO2 and expressed as ΔBOLD (%)/Δ P_ETCO₂ (mmHg). Trends in CVR over time were compared in both vascularized and non-vascularized hemispheres. Repeated measures analysis of variance with Greenhouse-Geisser correction was used to determine CVR changes within the grey matter MCA for longitudinal assessments. Overall, re-vascularized hemisphere showed a significant increase in CVR at the first follow-up, followed by a slight decrease at the second follow-up that significantly increased compared to the pre-bypass. However, the changes in the postoperative CVR were quite variable across the patients. Similar variability was seen in subsequent follow-ups, with a slight overall decline in the long term CVR as compared with first post-operative CVR. Our study demonstrates that EC-IC bypass has a beneficial long-term effect on cerebral hemodynamics and this effect varies between patients probably due to the variability in the underlying vascular pattern receiving the bypass. Hence, in the postoperative follow-up of patients routine functional imaging to monitor cerebral hemodynamics may be useful as the risk of stroke and cognitive decline remain present with impaired CVR.

Diffuse gliomas exhibit whole brain impaired cerebrovascular reactivity

PURPOSE

Cerebral diffuse gliomas exhibit perilesional impaired cerebrovascular reactivity (CVR), yet the degree of impairment as well as its full spatial extent in the brain remains unknown. With quantitative fMRI, we studied twelve subjects with untreated brain diffuse glioma and twelve healthy controls to assess CVR impairment and determine its distribution throughout the brain.

METHODS

In a prospective case-control study, quantitative CVR measurements were derived from BOLD fMRI volumes during standardized iso-oxic changes in carbon dioxide. Whole brain CVR was assessed with additional detailed analyses using specific tumor and tissue masks and compared to datasets of healthy controls.

RESULTS

Whole brain CVR was significantly impaired compared to healthy controls (0.11±0.10 versus 0.28±0.8, p<0.01). All diffuse glioma patients exhibited even more severely impaired intralesional CVR (mean 0.01±0.06). Increasing tumor volume significantly correlated with severity of intralesional CVR impairment (p<0.05, R²=0.38), and whole brain CVR impairment (p<0.05, R²=0.55).

CONCLUSION

Patients with brain diffuse glioma exhibit intralesional and whole brain impaired CVR with severity correlating to tumor volume. Quantitative fMRI may be entertained to study antitumor therapy efficacy by tracking CVR changes and may have a complementary role to better interpret BOLD associated neurovascular uncoupling.

Baseline Hemodynamic Impairment and Future Stroke Risk in Adult Idiopathic Moyamoya Phenomenon: Results of a Prospective Natural History Study

BACKGROUND AND PURPOSE

The purpose was to test the hypothesis that increased oxygen extraction fraction (OEF), a marker of severe hemodynamic impairment measured by positron emission tomography, is an independent risk factor for subsequent ischemic stroke in this population.

METHODS

Adults with idiopathic moyamoya phenomena were recruited between 2005 and 2012 for a prospective, multicenter, blindly adjudicated, longitudinal cohort study. Measurements of OEF were obtained on enrollment. Subjects were followed up for the occurrence of ipsilateral ischemic stroke at 6-month intervals. Patients were censored at the time of surgical revascularization or at last follow-up. The primary analysis was time to ischemic stroke in the territory of the occlusive vasculopathy.

RESULTS

Forty-nine subjects were followed up during a median of 3.7 years. One of 16 patients with increased OEF on enrollment had an ischemic stroke and another had an intraparenchymal hemorrhage. Three of 33 patients with normal OEF had an ischemic stroke. On a per-hemisphere basis, 21 of 79 hemispheres with moyamoya vasculopathy had increased OEF at baseline. No ischemic strokes and one hemorrhage occurred in a hemisphere with increased OEF (n=21). Sixteen patients (20 hemispheres), including 5 with increased OEF at enrollment, were censored at a mean of 5.3 months after enrollment for revascularization surgery.

CONCLUSIONS

The risk of new or recurrent stroke was lower than expected. The low event rate, low prevalence of increased OEF, and potential selection bias introduced by revascularization surgery limit strong conclusions about the association of increased OEF and future stroke risk.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00629915.

Evaluation of Encephaloduroarteriosynangiosis Efficacy Using Probabilistic Independent Component Analysis Applied to Dynamic Susceptibility Contrast Perfusion MRI

BACKGROUND AND PURPOSE

Indirect cerebral revascularization has been successfully used for treatment in Moyamoya disease and symptomatic intracranial atherosclerosis. While angiographic neovascularization has been demonstrated after surgery, measurements of local tissue perfusion are scarce and may not reflect the reported successful clinical outcomes. We investigated probabilistic independent component analysis and conventional perfusion parameters from DSC-MR imaging to measure postsurgical changes in tissue perfusion.

MATERIALS AND METHODS

In this prospective study, 13 patients underwent unilateral indirect cerebral revascularization and DSC-MR imaging before and after surgery. Conventional perfusion parameters (relative cerebral blood volume, relative cerebral blood flow, and TTP) and probabilistic independent components that reflect the relative contributions of DSC signals consistent with arterial, capillary, and venous hemodynamics were calculated and examined for significant changes after surgery. Results were compared with postsurgical DSA studies to determine whether changes in tissue perfusion were due to postsurgical neovascularization.

RESULTS

Before surgery, tissue within the affected hemisphere demonstrated a high probability for hemodynamics consistent with venous flow and a low probability for hemodynamics consistent with arterial flow, whereas the contralateral control hemisphere demonstrated the reverse. Consistent with symptomatic improvement, the probability for venous hemodynamics within the affected hemisphere decreased with time after surgery (P = .002). No other perfusion parameters demonstrated this association. Postsurgical DSA revealed an association between an increased preoperative venous probability in the symptomatic hemisphere and neovascularization after surgery.

CONCLUSIONS

Probabilistic independent component analysis yielded sensitive measurements of changes in local tissue perfusion that may be associated with newly formed vasculature after indirect cerebral revascularization surgery.

Impaired dynamic cerebrovascular response to hypercapnia predicts development of white matter hyperintensities

Purpose

To evaluate the relationship between both dynamic and steady-state measures of cerebrovascular reactivity (CVR) and the progression of age-related white matter disease.

Methods

Blood oxygen level-dependent (BOLD) MRI CVR scans were acquired from forty-five subjects (age range: 50–90 years, 25 males) with moderate to severe white matter disease, at baseline and one-year follow-up. To calculate the dynamic (τ) and steady-state (ssCVR) components of the BOLD signal response, the P_ETCO₂ signal waveform was convolved with an exponential decay function. The τ corresponding to the best fit between the convolved P_ETCO₂ and BOLD signal defined the speed of response, and the slope of the regression between the convolved P_ETCO₂ and BOLD signal defined ssCVR. ssCVR and τ were compared between normal-appearing white matter (NAWM) that remains stable over time and NAWM that progresses to white matter hyperintensities (WMHs).

Results

In comparison to contralateral NAWM, NAWM that progressed to WMH had significantly lower ssCVR values by mean (SD) 46.5 (7.6)%, and higher τ values by 31.9 (9.6)% (both P < 0.01).

Conclusions

Vascular impairment in regions of NAWM that progresses to WMH consists not only of decreased magnitude of ssCVR, but also a pathological decrease in the speed of vascular response. These findings support the association between cerebrovascular dysregulation and the development of WMH.

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Vascular responses are slower in normal white matter that progresses to disease.

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Steady-state cerebrovascular reactivity is reduced in normal white matter that progresses to disease.

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Cerebrovascular dysregulation occurs before development of leukoaraiosis.

One sided bypass for bilateral Moyamoya disease, a case report and review of the literatures

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Moyamoya disease (MMD) is a rare condition which can present both in children and adults.

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Diagnosis is usually established after imagine.

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Treatment is aiming at stroke prevention by improving blood flow.

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When surgical intervention is considered, unilateral revascularisation might be sufficient even for patients with bilateral lesion.

Background

Moyamoya disease (MMD) is a rare condition, where the most appropriate treatment for it is yet to be determined. Surgery remains an important method of choice although it is considered a form of palliative care. The outcome following surgery is very difficult to judge, and there is no standardised measurement to assess it. It is therefore important to know which approach for such patient is adequate.

Clinical presentation

A 21-year-old male patient presented with signs and symptoms of intracranial haemorrhage. Upon investigation, a diagnosis of bilateral MMD was made, and one sided direct bypass surgery was subsequently performed. At 3-year follow-up, there is no evidence of recurrent cerebral vascular event.

Conclusion

This case provided further evidence that direct bypass surgery is beneficial for patient in terms of blood flow improvement and symptom relieve. Although there is no consensus on whether bilateral surgical intervention is mandatory for patient with bilateral MMD, unilateral bypass might be sufficient enough. Further study is required to evaluate the best approach for such group of patient.

Reduced cerebrovascular reserve is regionally associated with cortical thickness reductions in children with sickle cell disease

Sickle cell disease (SCD) is a genetic disorder which adversely affects cerebrovascular health. Previous studies have demonstrated regional cortical thinning in SCD. However, the reason behind regional reductions in cortical thickness remains unclear. Therefore, we aimed to explore the possible link between the state of cerebrovascular health and cortical thickness. In this study, we obtained magnetic resonance (MR) based measures of cerebrovascular reactivity (CVR), a measure of vascular health, and cortical thickness in SCD patients (N=60) and controls of similar age and similar gender ratio (N=27). The group comparison analysis revealed significant regionally specific reductions in CVR and cortical thickness in the SCD group compared to the controls. In addition, a regional association analysis was performed between CVR and cortical thickness in the SCD group which revealed a significant regional association in several brain regions with the highest strength of association observed in the left cuneus, right post central gyrus and the right temporal pole. The regional association analysis revealed that significant associations were found in brain regions with high metabolic activity (anterior cingulate, posterior cingulate, occipital gyrus, precuneus) thus demonstrating that these regions could be most vulnerable to structural damage under hypoxic conditions.