Assessment Of Cerebral Hemodynamics Research Articles

Cerebral hemodynamic disorders in patients with schizophrenia with concomitant metabolic syndrome

To identify the differences or comparability of parameters of cerebral hemodynamics between patients with schizophrenia with or without concomitant metabolic syndrome (MS). The study included 94 patients with schizophrenia (48 men and 46 women). A control group consisted of 40 mentally and somatically healthy individuals (17 men and 23 women) comparable in sex and age to the main group of patients. The diagnosis of metabolic syndrome was carried out according to the criteria of the International Diabetes Federation (IDF). Assessment of cerebral hemodynamics was carried out by 4 - channel rheoencephalography (REG) at rest with closed eyes. Data analysis was carried out using the Kraskel-Wallis ANOVA criterion with the procedure of automatic a posteriori pairwise comparison, the χ2 criterion and Spearman correlation analysis. According to the IDF criteria, 37 (39.4%) patients were diagnosed with MS. REG results revealed significantly (p<0.05) lower indicators of blood filling in the carotid basin, elasticity of the wall of the main arteries, the tone of small-caliber arteries and arterioles, as well as higher values of the tone of medium-caliber arteries in the carotid and vertebrobasilar basins, in both groups of patients with schizophrenia compared with the control group. In patients with schizophrenia with MS, compared with patients without MS, there were lower indicators of blood filling (p=0.044 and p=0.016) and elasticity of the wall of the main arteries (p=0.044 and p=0.028) in the carotid basin on the left and right sides. The presence of MS in patients with schizophrenia was accompanied by more pronounced disorders of cerebral blood flow in the form of a decrease in blood filling and elasticity of the wall of the main arteries in the carotid basin. The results indicate that patients with schizophrenia with MS should be considered as a group at increased risk of cerebrovascular diseases.

Imaging Photoplethysmography in Green Light for Assessment of Cerebral Hemodynamics through an Intact Skull

Imaging Photoplethysmography in Green Light for Assessment of Cerebral Hemodynamics through an Intact Skull

Event-Related Cerebral Hemodynamic Assessment of Vigilance: Evidence in Favor of a More Temporally Precise Analysis

Transcranial Doppler sonography (TCD) is a neuroergonomic measure used in research on vigilance tasks. The current study focused on eventrelated analysis of TCD data, a relatively novel analytical approach that has previously been used to reveal that brain activity increases briefly when an individual detects a critical, target stimulus. Although research suggests that this detection-related response is sensitive to fatigue and demand effects associated with vigilance, future use and interpretation of event-related TCD analyses is complicated by interstudy variability in the time course and magnitude of the detection-related response. One possibility is that previous methods may have been too temporally coarse (4-second averages), so the current study reanalyzed data from one previous event-related study – this time using narrower 2-second averages. Results indicated that 2-second averages provided more precise depiction of the detection-related response than 4-second averages. We recommend use of 2-second averages for future eventrelated CBFV research.

Normative Cerebral Hemodynamics in Middle-aged and Older Adults Using 4D Flow MRI: Initial Analysis of Vascular Aging.

Background Characterizing cerebrovascular hemodynamics in older adults is important for identifying disease and understanding normal neurovascular aging. Four-dimensional (4D) flow MRI allows for a comprehensive assessment of cerebral hemodynamics in a single acquisition. Purpose To establish reference intracranial blood flow and pulsatility index values in a large cross-sectional sample of middle-aged (45-65 years) and older (>65 years) adults and characterize the effect of age and sex on blood flow and pulsatility. Materials and Methods In this retrospective study, patients aged 45-93 years (cognitively unimpaired) underwent cranial 4D flow MRI between March 2010 and March 2020. Blood flow rates and pulsatility indexes from 13 major arteries and four venous sinuses and total cerebral blood flow were collected. Intraobserver and interobserver reproducibility of flow and pulsatility measures was assessed in 30 patients. Descriptive statistics (mean ± SD) of blood flow and pulsatility were tabulated for the entire group and by age and sex. Multiple linear regression and linear mixed-effects models were used to assess the effect of age and sex on total cerebral blood flow and vessel-specific flow and pulsatility, respectively. Results There were 759 patients (mean age, 65 years ± 8 [SD]; 506 female patients) analyzed. For intra- and interobserver reproducibility, median intraclass correlation coefficients were greater than 0.90 for flow and pulsatility measures across all vessels. Regression coefficients β ± standard error from multiple linear regression showed a 4 mL/min decrease in total cerebral blood flow each year (age β = -3.94 mL/min per year ± 0.44; P < .001). Mixed effects showed a 1 mL/min average annual decrease in blood flow (age β = -0.95 mL/min per year ± 0.16; P < .001) and 0.01 arbitrary unit (au) average annual increase in pulsatility over all vessels (age β = 0.011 au per year ± 0.001; P < .001). No evidence of sex differences was observed for flow (β = -1.60 mL/min per male patient ± 1.77; P = .37), but pulsatility was higher in female patients (sex β = -0.018 au per male patient ± 0.008; P = .02). Conclusion Normal reference values for blood flow and pulsatility obtained using four-dimensional flow MRI showed correlations with age. © RSNA, 2023 Supplemental material is available for this article. See also the editorial by Steinman in this issue.

Non-invasive assessment of cerebral hemoglobin parameters in intracranial dural arteriovenous fistula using functional near-infrared spectroscopy-A feasibility study.

The purpose of this study was to assess the feasibility of non-invasive assessment of cerebral hemodynamics using functional near-infrared spectroscopy (fNIRS) in patients with intracranial dural arteriovenous fistula (DAVF) and to correlate the hemodynamic changes with definitive endovascular treatment. Twenty-seven DAVF patients and 23 healthy controls underwent 20-mins task-based functional near-infrared spectroscopy and neuropsychology evaluation. The mean change in the hemoglobin concentrations obtained from the prefrontal cortex was assessed for oxyhemoglobin, deoxyhemoglobin, and oxygen saturation (HbO, HbR, and SO2, respectively). The fNIRS data were analyzed and correlated with improvement in neuropsychology scores at 1-month follow-up. There was a significant reduction in HbO in the patient group, while it increased in controls (-2.57E-05 vs. 1.09E-04 mM, p < 0.001). The reduced HbO significantly improved after embolization (-2.1E-04 vs. 9.9E-04, p = 0.05, q = 0.05). In patients with aggressive DAVF (Cognard 2B and above), the change was highly significant (p < 0.001; q = 0.001). A moderate correlation was observed between MMSE scores and HbO changes (ρ = 0.4). fNIRS is a useful non-invasive modality for the assessment of DAVF, and could potentially assist in bedside monitoring of treatment response.

Evidence of Efficacy of Superficial Temporal Artery-Middle Cerebral Artery Bypass in Japan

The Japanese EC-IC Bypass Trial(JET)Study demonstrated that a superficial temporal artery-middle cerebral artery(STA-MCA)bypass is effective in preventing the recurrence of ischemic stroke in cases of atherosclerotic internal carotid artery or MCA steno-occlusive lesions with symptoms. The JET-2 Study revealed that the hemodynamic criteria for STA-MCA bypass in the JET Study(rest cerebral blood flow < 80% and cerebrovascular reactivity < 10%)were adequate. An STA-MCA bypass was ranked as recommendation B; the level of evidence was moderate under the conditions of quantitative evaluation of cerebral hemodynamics and low frequency of perioperative complications, as described in the Japanese Guidelines for the Management of Stroke 2021. An education system for the accurate assessment of cerebral hemodynamics, meticulous surgical procedures, and perioperative management for STA-MCA bypass is necessary to hand over evidence of STA-MCA bypass efficacy in Japan to future generations. Simultaneously, new evidence of STA-MCA bypass efficacy should be explored with the advancement of medicine and should be disseminated worldwide.

Prolonged Automated Robotic TCD Monitoring in Acute Severe TBI: Study Design and Rationale.

Transcranial Doppler ultrasonography (TCD) is a portable, bedside, noninvasive diagnostic tool used for the real-time assessment of cerebral hemodynamics. Despite the evident utility of TCD and the ability of this technique to function as a stethoscope to the brain, its use has been limited to specialized centers because of the dearth of technical and clinical expertise required to acquire and interpret the cerebrovascular parameters. Additionally, the conventional pragmatic episodic TCD monitoring protocols lack dynamic real-time feedback to guide time-critical clinical interventions. Fortunately, with the recent advent of automated robotic TCD technology in conjunction with the automated software for TCD data processing, we now have the technology to automatically acquire TCD data and obtain clinically relevant informationin real-time. By obviating the need for highly trained clinical personnel, this technology shows great promise toward a future of widespread noninvasive monitoring to guide clinical care in patients with acute brain injury. Here, we describe a proposal for a prospective observational multicenter clinical trial to evaluate the safety and feasibility of prolonged automated robotic TCD monitoring in patients with severe acute traumatic brain injury (TBI). We will enroll patients with severe non-penetratingTBI with concomitant invasive multimodal monitoring including, intracranial pressure, brain tissue oxygenation, and brain temperature monitoring as part of standard of care in centers with varying degrees of TCD availability and experience. Additionally, we propose to evaluate the correlation of pertinent TCD-based cerebral autoregulation indicessuch as the critical closing pressure, and the pressure reactivity index withthe brain tissue oxygenationvaluesobtained invasively. The overarching goal of this study is to establish safety and feasibility of prolonged automated TCD monitoring for patients with TBI in the intensive care unit and identify clinically meaningful and pragmatic noninvasive targets for future interventions.

Role of Bedside Transcranial Ultrasonography in the Assessment of Cerebral Hemodynamics in Decompressive Craniectomy Patients with Cranioplasty: A Single Centre Experience

Intracerebral hemorrhage is a leading cause of death and disability worldwide. After intracerebral hemorrhage, cerebral blood flow (CBF) becomes extremely low approaching ischemic thresholds. Concurrently, CBF velocities become strongly correlated to CBF itself post-injury. Identification of such hemodynamic disturbances can be used to predict outcome immediately post-injury when indices are measured using transcranial doppler ultrasonography (TCD). TCD permits non-invasive assessment of different CBF velocities as well as pulsatility index (PI). Abnormal measurement of such indices is believed to correlate to poor outcome. To investigate the effect of cerebral hemodynamics after cranioplasty in decompressive craniectomy patients using pre and postoperative TCD. This study is a prospective study of 3 years duration undertaken on 64 patients. All the patients were evaluated by TCDbefore and after decompressive craniectomy.All patients were evaluated by transcranial Doppler (TCD) 1 week before and 7-15 days after cranioplasty. TCD results were obtained though trans-temporal approach. Statistically significant differences between the values before and after craniectomy were detected in Peak Systolic Volume (PSV) for the Anterior Cerebral Artery (ACA) (P = 0.001), in PSV for the Middle Cerebral Artery (MCA) (P < 0.004), in Mean Bloodflow Velocity (MV) for the MCA (P < 0.003), and in PSV for the Posterior Cerebral artery (PCA) (P = 0.001) on the ipsilateral side. There were statistically significant differences between the values before and after cranioplasty in PSV for the PCA (P = 0.004), on contralateral side.After decompressive craniectomy, the PI values for the MCA decreased, on average, to 31+/- 33% of the pre-surgical value in the treated side and to 28+/- 31% on the opposite side. On the other hand, the mean PI values for the extracranial ICA reduced to 34+/- 21% of the initial values in the treated side, and to 21+/- 31% on the opposite side.Cranioplasty improved CBF velocities in all major intracrainal arteries, not only on the side of the lesion adjacent to the cranioplasty, but also in distant regions, such as in the contralateral hemisphere. Decompressive craniectomy significantly improves cerebral hemodynamics both on ipsilateral and contralateral cerebral hemispheres.Concomitantly, PI values on TCD decrease significantly postoperatively, mainly in the decompressed cerebral hemisphere, indicating reduction in cerebrovascular resistance. We conclude that cranioplasty improves neurological status and the mechanism of postoperative improvement of neurological status may be due to increased CBF velocity.

Clinical applications of point-of-care ultrasound in brain injury: a narrative review.

The use of point-of-care ultrasound has increased considerably over the last two decades. It has become a readily available, non-invasive bed-side modality for the rapid diagnosis and management of patients in varioussettings. Point-of-care ultrasound for assessing the heart, lung, abdomen, airway and vascular systems is now well established. Transcranial Doppler ultrasound for assessing cerebral blood flow has been in use for many years. In recent years, brain ultrasonography has been shown to be a powerful tool in the rapid bed-side assessment of cerebral haemodynamics and structural pathology. Brain ultrasound has been shown to be useful in both the emergency department and neurocritical care setting for the non-invasive assessment of raised intracranial pressure, cerebral autoregulation and diagnosis of intracranial haematoma and other space-occupying lesions. Point-of-care ultrasound is an important alternative technique to routine imaging and invasive monitoring techniques, and results are comparable. Competence is easily attainable without formal radiology training. With technological advancement, applications for the use of brain ultrasound continue to grow. This review discusses the clinical use of point-of-care ultrasound in the diagnosis and management of brain injury.

The Use of Different Components of Brain Oxygenation for the Assessment of Cerebral Haemodynamics: A Prospective Observational Study on COVID-19 Patients.

Introduction: The role of near-infrared spectroscopy (NIRS) for the evaluation of cerebral haemodynamics is gaining increasing popularity because of its noninvasive nature. The aim of this study was to evaluate the role of the integral components of regional cerebral oxygenation (rSO2) measured by NIRS [i.e., arterial-oxyhemoglobin (O2Hbi) and venous-deoxyhemoglobin (HHbi)-components], as indirect surrogates of cerebral blood flow (CBF) in a cohort of critically ill patients with coronavirus disease 2019 (COVID-19). We compared these findings to the gold standard technique for noninvasive CBF assessment, Transcranial Doppler (TCD).Methods: Mechanically ventilated patients with COVID-19 admitted to the Intensive Care Unit (ICU) of Policlinico San Martino Hospital, Genova, Italy, who underwent multimodal neuromonitoring (including NIRS and TCD), were included. rSO2 and its components [relative changes in O2Hbi, HHbi, and total haemoglobin (cHbi)] were compared with TCD (cerebral blood flow velocity, CBFV). Changes (Δ) in CBFV and rSO2, ΔO2Hbi, ΔHHbi, and ΔcHbi after systemic arterial blood pressure (MAP) modifications induced by different manoeuvres (e.g., rescue therapies and haemodynamic manipulation) were assessed using mixed-effect linear regression analysis and repeated measures correlation coefficients. All values were normalised as percentage changes from the baseline (Δ%).Results: One hundred and four measurements from 25 patients were included. Significant effects of Δ%MAP on Δ%CBF were observed after rescue manoeuvres for CBFV, ΔcHbi, and ΔO2Hbi. The highest correlation was found between ΔCBFV and ΔΔO2Hbi (R = 0.88, p < 0.0001), and the poorest between ΔCBFV and ΔΔHHbi (R = 0.34, p = 0.002).Conclusions: ΔO2Hbi had the highest accuracy to assess CBF changes, reflecting its role as the main component for vasomotor response after changes in MAP. The use of indexes derived from the different components of rSO2 can be useful for the bedside evaluation of cerebral haemodynamics in mechanically ventilated patients with COVID-19.

Индекс резистентности внутренних сонных артерий и нейросети мозга при хронической церебральной ишемии

Quantitative assessment of cerebral hemodynamics is important for patients with chronic cerebral ischemia (CCI), as it helps to reveal the pathogenesis of the disease and set the course for effective prevention and treatment. The study was aimed to assess the correlation of the left carotid artery (ICA) resistive index (RI) with cognitive functions and brain network organization based on fMRI data in patients with CCI (51 males and 105 females). The listed above indicators were studied in patients with the left ICA RI values below and above the average (0.54 ± 0.013). The lower, normal physiological ICA resistance levels corresponded to the more successful realization of verbal cognitive functions. In the first group, RI was within normal range (RI = 0.42 ± 0.007), and in the second group RI exceeded normal levels (RI = 0.61 ± 0.01). Variation of the right ICA RI did not correlate with the characteristics of verbal cognitive functions. FMRI data analysis was used to assess the differences in connectivity between various brain regions in the groups with low and high RI. The normal physiological and elevated RI values of the left ICA correlated with differences in the organization of brain networks: normal physiological RI values corresponded to a better organization of hemispheric connections in the basal ganglia and brainstem, and high RI values corresponded to a better organization of connections between the frontal regions and the cerebellum as well as occipital areas of the cerebral cortex. The left ICA RI can be considered as a biomarker of cognitive decline and brain networks reorganization in patients with CCI.

Brain Perfusion and Hemodynamic Changes in Moyamoya Disease

Moyamoya disease (MMD) – is a chronic progressive disorder of the unknown etiology with the development of the critical stenoses in internal carotid arteries and abnormal vascular net formation at the basal cerebrum to compensate the hemodynamic insufficiency and further development of the ischemic attacks, strokes, hematomas. The objective: to study the cerebral hemodynamic parameters and brain perfusion in patients with moyamoya disease. Materials and methods. We performed retrospective analysis of the cerebral angiography and cerebral perfusion investigations results of 6 patients with moyamoya desease, who were hospitalized in the State Institution «Romodanov Neurosurgery Institute of NAMS of Ukraine» in 2016–2020. All patients underwent a comprehensive examination, which included neuropsychological testing, the head and neck vessels duplex scanning, multispiral computed tomography (MSCT), selective cerebral angiography (SCA), and MSCT-angiography. The assessment of myamoya vessels was done by the Suzuki angiographic scale. Cerebral hemodynamics was studied by perfusion MSCT (PMSCT). Results. The diagnosis of moyamoya desease was confirmed in all patients by SCA and MSCT angiography. The clinical manifestation of the disease was represented by ischemic (n=5; 83.3%) and hemorrhagic (n=1; 16.7%) strokes. Stage 3, Stage 4 and Stage 6 has been diagnosed by Suzuki angiographic scale. Changes of the cerebral perfusion were more significant at Stage 4 / Stage 6: CBV was increased up to 20%, CBF was decreased &gt; 30% with MTT time &gt; 6 sec. The most significant changes were founed ipsilaterally in the territories of the MCA, moderate – in the territories of the ACA and PCA. Conclusion. In patients with moyamoya disease we have found the restructuring of the cerebral angioarchitectonics which has been matching the decrease of cerebral perfusion. Perfusion MSCT allows to get identification of the areas with an increased risk of ischemia and provides a decisive quantitative assessment of cerebral hemodynamics changes to establish indications for surgical treatment.

Intraoperative sonography in cranial neurosurgery: new possibilities and integration with neuronavigation. Review

In current review we represented new possibilities of intraoperative sonography introduced into clinical practice for the last 20 years. Contrast‑enhanced ultrasound and blood flow imaging (BFI) method are intended for assessment of cerebral hemodynamics. Elastosonography distinguishes tissues by differences of their density. Fusion of sonography with navigation is forwarded to brainshift reduction. Combination of ultrasound with endoscopy is effective in resection of intraventricular tumors and pituitary adenomas. Embedded three‑dimensional sonography is intended to facilitate interpretation of ultrasound results and tailoring craniotomy.

Assessment of cerebral hemodynamics in multiple sclerosis patients

BackgroundMultiple sclerosis (MS) is the most common demyelinating disease of the central nervous system. Autonomic dysfunction is present in a wide range of patients (15–80%) that might present with abnormalities in the regulation of the cardiovascular system, sleep disturbance, urinary symptoms, sexual problems, and temperature regulation problem. Although the predominant view is that of an autoimmune inflammatory condition, changes in brain vasculature can occur and contribute to pathophysiology.ObjectivesThe aim of this study was to evaluate cerebral hemodynamics and assess autonomic dysfunction in patients with MS and explore its relationship with disease status.MethodsEighty patients diagnosed with MS according to McDonald criteria 2017 were recruited to this comparative cross-sectional study. All participants underwent assessment of cerebral hemodynamics through transcranial Doppler ultrasonography. Cerebral vasomotor reactivity (CVR) to hypercapnia was measured by the breath-holding index (BHI). They were also assessed for autonomic dysfunction by autonomic questionnaire and blood pressure measurements in both erect and supine positions.ResultsBHI values showed decreased CVR and were significantly lower in SPMS than in RRMS patients. Autonomic functions were more affected in SPMS than RRMS with total score 2.58 ± 1.13 for the RRMS group and 4.05 ± 1.04 for the SPMS group.ConclusionsCerebrovascular hemodynamic insufficiency in MS may be secondary to the downstream effects of neuro-inflammatory cascades.

Left ventricular ejection fraction and right atrial diameter are associated with deep regional CBF in arteriosclerotic cerebral small vessel disease

BackgroundSystemic cardiac hypoperfusion is a well-acknowledged contributor to ischemic leukoencephalopathy. However, it has remained elusive how atherosclerosis-mediated cardiac remodelling modifies cerebral perfusion homeostasis as well as neuroimaging burden in cerebral small vessel disease (CSVD) development.MethodsThis retrospective study identified 103 arteriosclerotic CSVD (aCSVD) patients (CSVD burdenlow 0 ~ 1, n = 61 and CSVD burdenhigh 2 ~ 4, n = 42) from Sep. 2017 to Dec. 2019 who underwent transthoracic echocardiography(n = 81), structural magnetic resonance imaging and arterial spin labelling (ASL). Total CSVD burden was graded according to the ordinal “small vessel disease” rating score (0–4). We investigated the univariate and multivariate linear regression of mean deep regional cerebral blood flow (CBF) as well as logistic regression analysis of CSVD burdenhigh.ResultsRight atrial diameter (B coefficient, − 0.289; 95% CI, − 0.578 to − 0.001; P = 0.049) and left ventricular ejection fraction (B coefficient, 32.555; 95% CI, 7.399 to 57.711; P = 0.012) were independently associated with deep regional CBF in aCSVD patients. Binary logistic regression analysis demonstrated decreased deep regional CBF (OR 0.894; 95% CI 0.811–0.985; P = 0.024) was independently associated with higher CSVD burden after adjusted for clinical confounders. Multivariate receiver operating characteristics curve integrating clinical risk factors, mean deep CBF and echocardiographic parameters showed predictive significance for CSVD burdenhigh diagnosis (area under curve = 84.25, 95% CI 74.86–93.65%, P < 0.0001).ConclusionThe interrelationship of “cardiac -deep regional CBF-neuroimaging burden” reinforces the importance and prognostic significance of echocardiographic and cerebral hemodynamic assessment in CSVD early-warning.

Controversies and Advances in Adult Intracranial Bypass Surgery in 2020

Cerebral revascularization utilizing a variety of bypass techniques can provide either flow augmentation or flow replacement in the treatment of a range of intracranial pathologies, including moyamoya disease, intracranial atherosclerotic disease, and complex aneurysms that are not amenable to endovascular or simple surgical techniques. Though once routine, the publication of high-quality prospective evidence, along with the development of flow-diverting stents, has limited the indications for extracranial-to-intracranial (EC-IC) bypass. Nevertheless, advances in imaging, assessment of cerebral hemodynamics, and surgical technique have changed the risk-benefit calculus for EC-IC bypass. New variations of revascularization surgery involving multiple anastomoses, flow preserving solutions, IC-IC constructs, and posterior circulation bypasses have been pioneered for otherwise difficult to treat pathology including giant aneurysms, dolichoectasia, and medically refractory intracranial atherosclerosis. This review provides a practical update on recent advances in adult intracranial bypass surgery.

A Review of Cerebral Hemodynamics During Sleep Using Near-Infrared Spectroscopy

Investigating cerebral hemodynamic changes during regular sleep cycles and sleep disorders is fundamental to understanding the nature of physiological and pathological mechanisms in the regulation of cerebral oxygenation during sleep. Although sleep neuroimaging methods have been studied and have been well-reviewed, they have limitations in terms of technique and experimental design. Neurologists are convinced that Near-infrared spectroscopy (NIRS) provides essential information and can be used to assist the assessment of cerebral hemodynamics, and numerous studies regarding sleep have been carried out based on NIRS. Thus, a brief historical overview of the sleep studies using NIRS will be helpful for the biomedical students, academicians, and engineers to better understand NIRS from various perspectives. In this study, the existing literature on sleep studies is reviewed, and an overview of the NIRS applications is synthesized and provided. The paper first reviews the application scenarios, as well as the patterns of fluctuation of NIRS, which includes the investigation in regular sleep and sleep-disordered breathing. Various factors such as different sleep stages, populations, and degrees of severity were considered. Furthermore, the experimental design and signal processing, as well as the regulation mechanisms involved in regular and pathological sleep, are investigated and discussed. The strengths and weaknesses of the existing NIRS applications are addressed and presented, which can direct further NIRS analysis and utilization.

Assessment of Cerebral Blood Flow and Oxygen Extraction in Pediatric Sickle Cell Disease with Non-Invasive Diffuse Optical Spectroscopies

Introduction: Cerebral infarcts and associated cognitive impairments are a devastating consequence of sickle cell disease (SCD). While the underlying mechanisms are poorly understood, infarctions are thought to arise from anemia-induced microvascular perfusion abnormalities and subsequent reduced cerebrovascular reserve that is insufficient to meet tissue metabolic demands. Thus, quantification of abnormalities in microvascular cerebral blood flow (CBF) and oxygen extraction (OEF) may be useful in identifying infarct risk and monitoring therapeutic efficacy. Unfortunately, current modalities that quantify microvascular hemodynamics (e.g., PET, MRI) are prohibitively expensive, have limited availability, and require anesthesia in children &amp;lt;6y, making them inappropriate as routine monitoring tools. Transcranial Doppler ultrasound (TCD) is currently the standard screening tool for overt stroke risk in pediatric SCD, but it only measures blood flow velocity in the large arteries, which is a poor surrogate for microvascular perfusion in sickle cell disease. Diffuse optical spectroscopies (specifically near-infrared frequency-domain spectroscopy, FDNIRS, and diffuse correlation spectroscopy, DCS) offer a low-cost, non-invasive alternative for bedside monitoring of tissue-level OEF and CBF. We previously demonstrated that FDNIRS/DCS are sensitive to elevations in resting-state OEF and CBF in children with sickle cell disease compared to healthy controls (Lee, Neurophotonics 2019), consistent with previous studies using MRI and PET. In this feasibility study, we demonstrate these optical techniques are sensitive to altered cerebral hemodynamics in sickle patients who are 1) undergoing chronic transfusion, and 2) experiencing vaso-occlusive pain episodes (VOE). Methods: To date, we have recruited 6 pediatric patients with sickle cell disease undergoing chronic transfusion (5 females and 1 male, 6 - 14 y, mean ± std hemoglobin change pre- to post-transfusion = 1 ± 0.8 g/dL) and 4 patients admitted to the Emergency department for VOE (2 females and 2 males, 8 - 18 y, mean±std hemoglobin on admission = 8.9 ± 1.6 g/dL). For the transfusion cohort, FDNIRS/DCS measurements were made immediately prior to the start of transfusion and again immediately upon completion. For the VOE cohort, FDNIRS/DCS measurements were made upon hospital admission. For all FDNIRS/DCS assessments, a custom sensor was manually held over right and left forehead to assess oxygen extraction fraction (OEF, %) and an index of microvascular cerebral blood flow (CBFi, cm2/s) (Lee, Neurophotonics 2019). Hemispheric results were averaged to yield a mean of each measured parameter. Total measurement time was less than 15 minutes. Results: In the cohort undergoing chronic transfusion, one patient data was excluded due to poor DCS signal quality. Of the remaining 5 patients, OEF and CBFi decreased after transfusion by a median of -6.4% and -30.0%, respectively (Fig 1A, B). The FDNIRS-measured OEF decrease is comparable to previous results with MRI (Guilliams, Blood 2017) that quantified both cortical OEF and CBF response to transfusion in a similarly aged cohort. However, the DCS-measured CBFi decrease is more prominent than previously reported (30% vs. 9%). The enhanced sensitivity of DCS to CBF in sickle cell disease was reported in our recent study and is likely attributed to the confounding influences of hematocrit on the DCS-measured CBFi (Sathialingam, Biomed Opt Exp 2020). In the cohort measured during VOE, one patient data was excluded due to poor FDNIRS data quality. Of the remaining 3 subjects, OEF was elevated compared to healthy controls and was on the upper range of values measured in a cohort of otherwise subjects with sickle cell disease who were without clinical complications and were measured as part of a separate study (Fig. 1C). Conclusion: These data demonstrate how FDNIRS/DCS may be used as a simple, low-cost tool for bedside assessment of cerebral hemodynamics in non-sedated sickle children that could be used to track brain health over time, particularly during periods thought to be prone to hemodynamic instability like transfusion or VOEs. Although ~20% of data was discarded in this dataset due to improper sensor positioning leading to poor signal quality, we have recently implemented real-time quality control feedback to ensure our data passes quality criteria. Disclosures Lam: Sanguina, Inc: Current equity holder in private company.

Cerebral hemodynamics in patients with multiple sclerosis

Background and PurposeMultiple sclerosis (MS) is a demyelinating disease of the central nervous system. Although the currently predominant view is that of an autoimmune inflammatory condition, changes in brain vasculature can occur and contribute to pathophysiology. The aim of this study was to evaluate cerebral hemodynamics in patients with MS and explore its relationship with disease status. MethodsPatients with MS and age- and sex- matched healthy controls were recruited. All participants underwent assessment of cerebral hemodynamics through transcranial Doppler ultrasonography. Cerebral vasomotor reactivity (CVR) to hypercapnia was measured by the breath-holding index (BHI). ResultsA total of 80 patients with MS and 80 healthy controls were recruited. BHI values obtained in healthy controls, relapsing-remitting (RR)-MS and secondary progressive (SP)-MS patients were 1.15±0.11, 0.87±0.18 and 0.51±0.20, respectively (p<0.001). Group-wise, patients showed decreased CVR in comparison to controls and BHI values were significantly lower in SP-MS than in RR-MS patients. At linear regression analysis, the disease form was significantly associated with cerebral hemodynamics being the SP phenotype an independent predictor of lower BHI values [β=-0.36, 95% confidence interval (CI): -0.44 to -0.27, p<0.001; adjusted β=-0.37, 95% CI: -0.50 to -0.23, p<0.001). ConclusionsCerebrovascular hemodynamic insufficiency in MS may be secondary to the downstream effects of neuro-inflammatory cascades.

Cerebral spatially resolved near-infrared spectroscopy (SRS-NIRS): paving the way for non-invasive assessment of cerebral hemodynamics during atrial fibrillation

Cerebral spatially resolved near-infrared spectroscopy (SRS-NIRS): paving the way for non-invasive assessment of cerebral hemodynamics during atrial fibrillation