Lower middle cerebral artery blood velocity during low-volume high-intensity interval exercise in chronic stroke

High-intensity interval training (HIIE) may present unique challenges to the cerebrovascular system in individuals post-stroke. We hypothesized lower middle cerebral artery blood velocity (MCAv) in individuals post-stroke: 1) during 10 minutes of HIIE, 2) immediately following HIIE, and 3) 30 minutes after HIIE, compared to age- and sex-matched controls (CON). We used a recumbent stepper submaximal exercise test to determine workloads for high-intensity and active recovery. Our low volume HIIE protocol consisted of 1-minute intervals for 10 minutes. During HIIE, we measured MCAv, mean arterial pressure (MAP), heart rate (HR), and end tidal carbon dioxide (PETCO2). We assessed carotid-femoral pulse wave velocity as a measure of arterial stiffness. Fifty participants completed the study (25 post-stroke, 76% ischemic, 32% moderate disability). Individuals post-stroke had lower MCAv during HIIE compared to CON (p = 0.03), which remained 30 minutes after HIIE. Individuals post-stroke had greater arterial stiffness (p = 0.01) which was moderately associated with a smaller MCAv responsiveness during HIIE (r = -0.44). No differences were found for MAP, HR, and PETCO2. This study suggests individuals post-stroke had a lower MCAv during HIIE compared to their peers, which remained during recovery up to 30 minutes. Arterial stiffness may contribute to the lower cerebrovascular responsiveness post-stroke.

Cerebrovascular and cardiovascular autonomic regulation in sickle cell patients with white matter lesions

BACKGROUND AND PURPOSE

White matter lesions (WMLs) are frequent in sickle cell disease (SCD), with a prevalence described to be as high as 53% by age 30. Cerebrovascular regulation and cardiovascular autonomic regulation, more specifically the sympatho-vagal balance, can be altered in SCD. In this study the association between WMLs, cerebrovascular regulation and sympatho-vagal balance was assessed in SCD patients.

METHODS AND RESULTS

Sickle cell disease patients with no history of stroke were prospectively evaluated for cerebrovascular reactivity using the breath-holding test (BHT), the sympatho-vagal balance (ratio low frequency/high frequency [HF]) using heart rate variability parameters and cerebral autoregulation in the time domain using correlation index Mx, and arterial cerebral compliance based on continuous assessment of cerebral blood flow velocities using transcranial Doppler ultrasound and arterial blood pressure with photo-plethysmography. WMLs were assessed with magnetic resonance imaging using Fazekas score grading and the presence of lacunes. Forty-one patients (F/M 25/16) were included. Median age was 37.5 years (19-65). Twenty-nine (70.7%) patients had SS genotype. Eleven patients had WMLs (26.8%). Patients with WMLs were significantly older (p < 0.001), had a lower HF (p < 0.005) and an impaired cerebral arterial compliance (p < 0.014). The receiver operating curve for the regression model including age and HF showed a higher area under the curve compared to age alone (0.946 vs. 0.876). BHT and Mx did not significantly differ between the two groups.

CONCLUSIONS

Lower parasympathetic activity and impaired cerebral arterial compliance were associated with WMLs in adults with SCD. This could potentially yield to a better understanding of pathophysiological parameters leading to premature cerebrovascular ageing in SCD.

Lower dynamic cerebral autoregulation following acute bout of low-volume high-intensity interval exercise in chronic stroke compared to healthy adults

Fluctuating arterial blood pressure during high-intensity interval exercise (HIIE) may challenge dynamic cerebral autoregulation (dCA), specifically after stroke after an injury to the cerebrovasculature. We hypothesized that dCA would be attenuated at rest and during a sit-to-stand transition immediately after and 30 min after HIIE in individuals poststroke compared with age- and sex-matched control subjects (CON). HIIE switched every minute between 70% and 10% estimated maximal watts for 10 min. Mean arterial pressure (MAP) and middle cerebral artery blood velocity (MCAv) were recorded. dCA was quantified during spontaneous fluctuations in MAP and MCAv via transfer function analysis. For sit-to-stand, time delay before an increase in cerebrovascular conductance index (CVCi = MCAv/MAP), rate of regulation, and % change in MCAv and MAP were measured. Twenty-two individuals poststroke (age 60 ± 12 yr, 31 ± 16 mo) and twenty-four CON (age 60 ± 13 yr) completed the study. Very low frequency (VLF) gain (P = 0.02, η2 = 0.18) and normalized gain (P = 0.01, η2 = 0.43) had a group × time interaction, with CON improving after HIIE whereas individuals poststroke did not. Individuals poststroke had lower VLF phase (P = 0.03, η2 = 0.22) after HIIE compared with CON. We found no differences in the sit-to-stand measurement of dCA. Our study showed lower dCA during spontaneous fluctuations in MCAv and MAP following HIIE in individuals poststroke compared with CON, whereas the sit-to-stand response was maintained.NEW & NOTEWORTHY This study provides novel insights into poststroke dynamic cerebral autoregulation (dCA) following an acute bout of high-intensity interval exercise (HIIE). In people after stroke, dCA appears attenuated during spontaneous fluctuations in mean arterial pressure (MAP) and middle cerebral artery blood velocity (MCAv) following HIIE. However, the dCA response during a single sit-to-stand transition after HIIE showed no significant difference from controls. These findings suggest that HIIE may temporarily challenge dCA after exercise in individuals with stroke.

Impact of stalling events on microcirculatory hemodynamics in the aged brain

OBJECTIVE

The role of cerebral microvasculature in cognitive dysfunction can be investigated by identifying the impact of blood flow on cortical tissue oxygenation. In this paper, the impact of capillary stalls on microcirculatory characteristics such as flow and hematocrit (Ht) in the cortical angioarchitecture is studied.

METHODS

Using a deterministic mathematical model to simulate blood flow in a realistic mouse cortex, hemodynamics parameters, including pressure, flow, vessel diameter-adjustable hematocrit, and transit time are calculated as a function of stalling events.

RESULTS

Using a non-linear plasma skimming model, it is observed that Ht increases in the penetrating arteries from the pial vessels as a function of cortical depth. The incidence of stalling on Ht distribution along the blood network vessels shows reduction of RBCs around the tissue near occlusion sites and decreased Ht concentration downstream from the blockage points. Moreover, upstream of the occlusion, there is a noticeable increase of the Ht, leading to larger flow resistance due to higher blood viscosity. We predicted marked changes in transit time behavior due to stalls which match trends observed in mice in vivo.

CONCLUSIONS

These changes to blood cell quantity and quality may be implicated in the development of Alzheimer's disease and contribute to the course of the illness.

Cerebral hemodynamics and stroke risks in symptomatic intracranial atherosclerotic stenosis with internal versus cortical borderzone infarcts: A computational fluid dynamics study

There may be different mechanisms underlying internal (IBZ) and cortical (CBZ) borderzone infarcts in intracranial atherosclerotic stenosis. In 84 patients with symptomatic, 50-99% atherosclerotic stenosis of M1 middle cerebral artery (MCA-M1) with acute borderzone infarcts in diffusion-weighted imaging, we classified the infarct patterns as isolated IBZ (n = 37), isolated CBZ (n = 31), and IBZ+CBZ (n = 16) infarcts. CT angiography-based computational fluid dynamics models were constructed to quantify translesional, post-stenotic to pre-stenotic pressure ratio (PR) in the MCA-M1 lesion. Those with IBZ infarcts were more likely to have a low PR (indicating impaired antegrade flow across the lesion) than those without (p = 0.012), and those with CBZ infarcts were more likely to have coexisting small cortical infarcts (indicating possible embolism) than those without (p = 0.004). In those with isolated IBZ or CBZ infarcts, low PR was independently associated with isolated IBZ infarcts (adjusted odds ratio = 4.223; p = 0.026). These two groups may also have different trajectories in the stroke risks under current medical treatment regimen, with a higher risk of same-territory ischemic stroke recurrence within 3 months in patients with isolated IBZ infarcts than isolated CBZ infarcts (17.9% versus 0.0%; log-rank p = 0.023), but similar risks later in 1 year.

Validation of the Openwater wearable optical system: cerebral hemodynamic monitoring during a breath-hold maneuver

Significance

Bedside cerebral blood flow (CBF) monitoring has the potential to inform and improve care for acute neurologic diseases, but technical challenges limit the use of existing techniques in clinical practice.

Aim

Here, we validate the Openwater optical system, a novel wearable headset that uses laser speckle contrast to monitor microvascular hemodynamics.

Approach

We monitored 25 healthy adults with the Openwater system and concurrent transcranial Doppler (TCD) while performing a breath-hold maneuver to increase CBF. Relative blood flow (rBF) was derived from changes in speckle contrast, and relative blood volume (rBV) was derived from changes in speckle average intensity.

Results

A strong correlation was observed between beat-to-beat optical rBF and TCD-measured cerebral blood flow velocity (CBFv), R = 0.79 ; the slope of the linear fit indicates good agreement, 0.87 (95% CI: 0.83 - 0.92 ). Beat-to-beat rBV and CBFv were also strongly correlated, R = 0.72 , but as expected the two variables were not proportional; changes in rBV were smaller than CBFv changes, with linear fit slope of 0.18 (95% CI: 0.17 to 0.19). Further, strong agreement was found between rBF and CBFv waveform morphology and related metrics.

Conclusions

This first in vivo validation of the Openwater optical system highlights its potential as a cerebral hemodynamic monitor, but additional validation is needed in disease states.

Transcranial Doppler ultrasonography in bacterial meningitis: A systematic review

PURPOSE

Bacterial meningitis remains a global threat due to its high mortality. It is estimated that >1.2 million cases of bacterial meningitis are reported annually. Intracranial vasculopathy is an important, under-documented complication, easily detected by transcranial Doppler (TCD) ultrasonography. Following the PRISMA Guidelines, we reviewed the utility of TCD in bacterial meningitis.

METHODS

This is a systematic review of observational studies on the use of TCD in patients with CSF-proven bacterial meningitis. Characteristic changes in TCD parameters along the course of the disease, correlation of TCD findings with neuroimaging, and functional outcomes were evaluated.

RESULTS

Nine studies were included with a total of 492 participants (mean age of 42). The most common TCD finding was intracranial arterial stenosis of the MCA (50%-82%) and ischemia (33%) was the predominant neuroimaging finding. The presence of an abnormal TCD finding increased the risk of poor outcomes as high as 70%.

CONCLUSIONS

Patients diagnosed with bacterial meningitis who underwent TCD show alterations in cerebral blood flow, correlating with imaging findings and poor outcomes. It aids in the diagnosis of its sequelae and can predict the prognosis of its outcome. TCD is a cost-effective, reliable modality for diagnosing vasculopathy associated with bacterial meningitis. It may prove useful in our armamentarium of management. Large prospective studies with long-term follow-up data may help establish the use of TCD in bacterial meningitis.

Pulsatile microvascular cerebral blood flow waveforms change with intracranial compliance and age

Significance

Diffuse correlation spectroscopy (DCS) is an optical method to measure relative changes in cerebral blood flow (rCBF) in the microvasculature. Each heartbeat generates a pulsatile signal with distinct morphological features that we hypothesized to be related to intracranial compliance (ICC).

Aim

We aim to study how three features of the pulsatile rCBF waveforms: the augmentation index (AIx), the pulsatility index, and the area under the curve, change with respect to ICC. We describe ICC as a combination of vascular compliance and extravascular compliance.

Approach

Since patients with Chiari malformations (CM) (n = 30 ) have been shown to have altered extravascular compliance, we compare the morphology of rCBF waveforms in CM patients with age-matched healthy control (n = 30 ).

Results

AIx measured in the supine position was significantly less in patients with CM compared to healthy controls (p < 0.05 ). Since physiologic aging also leads to changes in vessel stiffness and intravascular compliance, we evaluate how the rCBF waveform changes with respect to age and find that the AIx feature was strongly correlated with age (R healthy subjects = - 0.63 , R preoperative   CM   patient = - 0.70 , and R postoperative   CM   patients = - 0.62 , p < 0.01 ).

Conclusions

These results suggest that the AIx measured in the cerebral microvasculature using DCS may be correlated to changes in ICC.

Detection of Blood CO2 Influences on Cerebral Hemodynamics Using Transfer Entropy

Cerebral hemodynamics describes an important physiological system affected by components such as blood pressure, CO2 levels, and endothelial factors. Recently, novel techniques have emerged to analyse cerebral hemodynamics based on the calculation of entropies, which quantifies or describes changes in the complexity of this system when it is affected by a pathological or physiological influence. One recently described measure is transfer entropy, which allows for the determination of causality between the various components of a system in terms of their flow of information, and has shown positive results in the multivariate analysis of physiological signals. This study aims to determine whether conditional transfer entropy reflects the causality in terms of entropy generated by hypocapnia on cerebral hemodynamics. To achieve this, non-invasive signals from 28 healthy individuals who undertook a hyperventilation maneuver were analyzed using conditional transfer entropy to assess the variation in the relevance of CO2 levels on cerebral blood velocity. By employing a specific method to discretize the signals, it was possible to differentiate the influence of CO2 levels during the hyperventilation phase (22.0% and 20.3% increase for the left and right hemispheres, respectively) compared to normal breathing, which remained higher during the recovery phase (15.3% and 15.2% increase, respectively).

Interdisciplinary Multidimensional Assessment of Transthyretin Amyloidosis before and after Tafamidis

BACKGROUND

Clinically, there is considerable heterogeneity in the presentation of transthyretin amyloidosis (ATTR), which ranges from primarily cardiac and primarily neurologic to mixed disease, among other manifestations. Because of this complex presentation, the diagnosis and management of patients with ATTR are often challenging and should be performed in interdisciplinary centers specialized in amyloidosis. Here, we aimed to increase awareness of ATTR detection and pathophysiology through a multidimensional multiorgan approach.

CASE REPORT

We reported on a 60-year-old man with wild-type ATTR who underwent a number of both basic and advanced cardiological and neurological investigations at baseline and after a treatment period with the TTR tetramer stabilizer, tafamidis. Several findings are provided here, some of which might be considered instrumental correlates of the patient's clinical improvement after therapy.

CONCLUSIONS

Adequate awareness and prompt recognition of ATTR support early diagnosis and faster access to therapies, thereby slowing the progression and improving the prognosis. The need for a multidisciplinary alliance between specialists and the opportunity to perform, at least in selected cases, a set of specific examinations for a detailed assessment of ATTR patients can also provide valuable insights into the physiopathology and response to therapy of a disease as complex and intriguing as ATTR.

The effects of pulsatile versus nonpulsatile flow on cerebral pulsatility index, mean flow velocity at the middle cerebral artery, regional cerebral oxygen saturation, cerebral gaseous microemboli counts, and short-term clinical outcomes in patients undergoing congenital heart surgery

Objective

The objective of this retrospective review was to evaluate whether or not pulsatile flow improves cerebral hemodynamics and clinical outcomes in pediatric congenital cardiac surgery patients.

Methods

This retrospective study included 284 pediatric patients undergoing congenital cardiac surgery with cardiopulmonary bypass support utilizing nonpulsatile (n = 152) or pulsatile (n = 132) flow. Intraoperative cerebral gaseous microemboli counts, pulsatility index, and mean blood flow velocity at the right middle cerebral artery were assessed using transcranial Doppler ultrasound. Clinical outcomes were compared between groups.

Results

Patient demographics and cardiopulmonary bypass characteristics between groups were similar. Although the pulsatility index during aortic crossclamping was consistently higher in the pulsatile group (P < .05), a significant degree of pulsatility was also observed in the nonpulsatile group. No significant differences in mean cerebral blood flow velocity, regional cerebral oxygen saturation, or gaseous microemboli counts were observed between the perfusion modality groups. Clinical outcomes, including intubation duration, intensive care unit and hospital length of stay, and mortality within 180 days were similar between groups.

Conclusions

Although the pulsatility index was greater in the pulsatile group, other measures of intraoperative cerebral perfusion and short-term outcomes were similar to the nonpulsatile group. These findings suggest that while pulsatile perfusion represents a safe modality for cardiopulmonary bypass support, its use may not translate into detectably superior clinical outcomes.

Diffuse Optical Monitoring of Cerebral Hemodynamics and Oxygen Metabolism during and after Cardiopulmonary Bypass: Hematocrit Correction and Neurological Vulnerability

Cardiopulmonary bypass (CPB) provides cerebral oxygenation and blood flow (CBF) during neonatal congenital heart surgery, but the impacts of CPB on brain oxygen supply and metabolic demands are generally unknown. To elucidate this physiology, we used diffuse correlation spectroscopy and frequency-domain diffuse optical spectroscopy to continuously measure CBF, oxygen extraction fraction (OEF), and oxygen metabolism (CMRO2) in 27 neonatal swine before, during, and up to 24 h after CPB. Concurrently, we sampled cerebral microdialysis biomarkers of metabolic distress (lactate-pyruvate ratio) and injury (glycerol). We applied a novel theoretical approach to correct for hematocrit variation during optical quantification of CBF in vivo. Without correction, a mean (95% CI) +53% (42, 63) increase in hematocrit resulted in a physiologically improbable +58% (27, 90) increase in CMRO2 relative to baseline at CPB initiation; following correction, CMRO2 did not differ from baseline at this timepoint. After CPB initiation, OEF increased but CBF and CMRO2 decreased with CPB time; these temporal trends persisted for 0-8 h following CPB and coincided with a 48% (7, 90) elevation of glycerol. The temporal trends and glycerol elevation resolved by 8-24 h. The hematocrit correction improved quantification of cerebral physiologic trends that precede and coincide with neurological injury following CPB.

Point-Counterpoint: Cerebral perfusion pressure is a high-risk concept

Cerebral perfusion pressure (CPP) is calculated as the difference between mean arterial blood pressure and mean intracranial pressure, being commonly applied in neurocritical care. This commentary discusses recent physiological advances in knowledge as well as bedside practice issues that in combination indicate considering CPP under this perspective may lead to inaccurate assumptions and potentially misleading decision making.

Effects of Physical Exercise on Cerebral Blood Velocity in Older Adults: A Systematic Review and Meta-Analysis

As the older population grows, there is an increasing interest in understanding how physical exercise can counteract the changes seen with aging. The benefits of exercise to general health, and especially to the cardiovascular system, have been a topic of discussion for decades. However, there is still a need to elucidate the effects of training programs on the cerebrovascular blood velocity in older people. This systematic review and meta-analysis aimed to investigate the effect of physical exercise on the cerebral blood velocity in older people (PROSPERO CRD42019136305). A search was performed on PubMed, Web of Science, EBSCO, ScienceDirect, and Scopus from the inception of this study to October 2023, retrieving 493 results, of which 26 were included, analyzing more than 1000 participants. An overall moderate risk of bias was found for the studies using the Cochrane risk-of-bias tools for randomized and non-randomized clinical trials. The pooled results of randomized trials showed that older people who underwent physical exercise presented a statistically significant increase in cerebral blood velocity (3.58; 95%CI = 0.51, 6.65; p = 0.02). This result indicates that physical exercise is important to help maintain cerebral health in older adults.

Quantitative hemodynamic imaging: a method to correct the effects of optical properties on laser speckle imaging

Significance

Studying cerebral hemodynamics may provide diagnostic information on neurological conditions. Wide-field imaging techniques, such as laser speckle imaging (LSI) and optical intrinsic signal imaging, are commonly used to study cerebral hemodynamics. However, they often do not account appropriately for the optical properties of the brain that can vary among subjects and even during a single measurement. Here, we describe the combination of LSI and spatial-frequency domain imaging (SFDI) into a wide-field quantitative hemodynamic imaging (QHI) system that can correct the effects of optical properties on LSI measurements to achieve a quantitative measurement of cerebral blood flow (CBF).

Aim

We describe the design, fabrication, and testing of QHI.

Approach

The QHI hardware combines LSI and SFDI with spatial and temporal synchronization. We characterized system sensitivity, accuracy, and precision with tissue-mimicking phantoms. With SFDI optical property measurements, we describe a method derived from dynamic light scattering to obtain absolute CBF values from LSI and SFDI measurements. We illustrate the potential benefits of absolute CBF measurements in resting-state and dynamic experiments.

Results

QHI achieved a 50-Hz raw acquisition frame rate with a 10 × 10    mm field of view and flow sensitivity up to ∼ 4    mm / s . The extracted SFDI optical properties agreed well with a commercial system (R 2 ≥ 0.98 ). The system showed high stability with low coefficients of variations over multiple sessions within the same day (< 1 % ) and over multiple days (< 4 % ). When optical properties were considered, the in-vivo hypercapnia gas challenge showed a slight difference in CBF (- 1.5 % to 0.5% difference). The in-vivo resting-state experiment showed a change in CBF ranking for nine out of 13 animals when the correction method was applied to LSI CBF measurements.

Conclusions

We developed a wide-field QHI system to account for the confounding effects of optical properties on CBF LSI measurements using the information obtained from SFDI.

Older females but not males exhibit increases in cerebral blood velocity, despite similar pulsatility increases after high-intensity resistance exercise

Sex differences in resting cerebral hemodynamics decline with aging. Given that acute resistance exercise (RE) is a hypertensive challenge, it may reveal sex-dependent abnormalities in cerebral hemodynamics. Thus, we hypothesized that cerebral blood velocity and pulsatility responses to RE would be sex-dependent in older adults. Fourteen older females and 11 males (50-68 yr) completed a high-intensity unilateral isokinetic knee flexion/extension exercise. Measurements were collected at baseline, immediately, 5- and 30-min post-RE. Blood pressure was measured via finger photoplethysmography. Mean middle cerebral artery blood velocity (MCAv) and pulsatility were assessed via transcranial Doppler ultrasound. Carotid pulsatility was obtained via duplex ultrasound. MCAv increased immediately after RE in older females [mean difference (d) = 6.02, 95% CI: 1.66 to 10.39 cm/s, P < 0.001] but not in males (d = -0.72, 95% CI: -3.83 to 5.27 cm/s, P = 0.99), followed by similar reductions 5-min post-RE in older females (d = -4.40, 95% CI: -8.81 to -0.10 cm/s, P = 0.045) and males (d = -6.41, 95% CI: -11.19 to -1.62 cm/s, P = 0.003). MCAv pulsatility increased similarly in older females (d = 0.24, 95% CI: 0.11 to 0.40, P < 0.001) and males (d = 0.38, 95% CI: 0.20 to 0.53, P < 0.001), persisting 5-min post-RE. Older females showed smaller increases in carotid pulsatility immediately after RE (d = 0.18, 95% CI: 0.03 to 0.38, P = 0.01) than males (d = 0.48, 95% CI: 0.26 to 0.68, P < 0.001). An exercise-mediated hypertensive stimulus revealed differential sex responses in MCAv and carotid pulsatility but not in cerebral pulsatility. Cerebral pulsatility findings suggest a similar sex susceptibility to cerebrovascular abnormalities following exercise-mediated hypertensive stimulus in older adults.NEW & NOTEWORTHY Sex differences in resting cerebral hemodynamics decline with advancing age as females experience larger reductions in cerebral blood velocity and steeper pulsatility increases than males. However, an exercise-mediated hypertensive stimulus might reveal sex differences in cerebral hemodynamics not apparent at rest. Following high-intensity resistance exercise, older females but not males exhibit increases in cerebral blood velocity, despite similar increases in cerebral pulsatility. The susceptibility to cerebrovascular abnormalities following exercise-mediated hypertensive stimulus appears similar between sexes.

Impact of continuous-flow mechanical circulatory support on cerebrospinal fluid motility

BACKGROUND

Mechanical circulatory support (MCS), including ventricular assist devices (VADs), have emerged as promising therapeutic alternatives for end-stage congestive heart failure (CHF). The latest generation of these devices are continuous flow (CF) blood pumps. While there have been demonstrated benefits to patient outcomes due to CF-MCS, there continue to be significant clinical challenges. Research to-date has concentrated on mitigating thromboembolic risk (stroke), while the downstream impact of CF-MCS on the cerebrospinal fluid (CSF) flow has not been well investigated. Disturbances in the CSF pressure and flow patterns are known to be associated with neurologic impairment and diseased states. Thus, here we seek to develop an understanding of the pathophysiologic consequences of CF-MCS on CSF dynamics.

METHODS

We built and validated a computational framework using lumped parameter modeling of cardiovascular, cerebrovascular physics, CSF dynamics, and autoregulation. A sensitivity analysis was performed to confirm robustness of the modeling framework. Then, we characterized the impact of CF-MCS on the CSF and investigated cardiovascular conditions of healthy and end-stage heart failure.

RESULTS

Modeling results demonstrated appropriate hemodynamics and indicated that CSF pressure depends on blood flow pulsatility more than CSF flow. An acute equilibrium between CSF production and absorption was observed in the CF-MCS case, characterized by CSF pressure remaining elevated, and CSF flow rates remaining below healthy, but higher than CHF states.

CONCLUSION

This research has advanced our understanding of the impact of CF-MCS on CSF dynamics and cerebral hemodynamics.

Personalised simulation of hemodynamics in cerebrovascular disease: lessons learned from a study of diagnostic accuracy

Intracranial atherosclerotic disease (ICAD) poses a significant risk of subsequent stroke but current prevention strategies are limited. Mechanistic simulations of brain hemodynamics offer an alternative precision medicine approach by utilising individual patient characteristics. For clinical use, however, current simulation frameworks have insufficient validation. In this study, we performed the first quantitative validation of a simulation-based precision medicine framework to assess cerebral hemodynamics in patients with ICAD against clinical standard perfusion imaging. In a retrospective analysis, we used a 0-dimensional simulation model to detect brain areas that are hemodynamically vulnerable to subsequent stroke. The main outcome measures were sensitivity, specificity, and area under the receiver operating characteristics curve (ROC AUC) of the simulation to identify brain areas vulnerable to subsequent stroke as defined by quantitative measurements of relative mean transit time (relMTT) from dynamic susceptibility contrast MRI (DSC-MRI). In 68 subjects with unilateral stenosis >70% of the internal carotid artery (ICA) or middle cerebral artery (MCA), the sensitivity and specificity of the simulation were 0.65 and 0.67, respectively. The ROC AUC was 0.68. The low-to-moderate accuracy of the simulation may be attributed to assumptions of Newtonian blood flow, rigid vessel walls, and the use of time-of-flight MRI for geometric representation of subject vasculature. Future simulation approaches should focus on integrating additional patient data, increasing accessibility of precision medicine tools to clinicians, addressing disease burden disparities amongst different populations, and quantifying patient benefit. Our results underscore the need for further improvement of mechanistic simulations of brain hemodynamics to foster the translation of the technology to clinical practice.

How does obstructive sleep apnea alter cerebral hemodynamics?

STUDY OBJECTIVES

We aimed to characterize the cerebral hemodynamic response to obstructive sleep apnea/hypopnea events, and evaluate their association to polysomnographic parameters. The characterization of the cerebral hemodynamics in obstructive sleep apnea (OSA) may add complementary information to further the understanding of the severity of the syndrome beyond the conventional polysomnography.

METHODS

Severe OSA patients were studied during night sleep while monitored by polysomnography. Transcranial, bed-side diffuse correlation spectroscopy (DCS) and frequency-domain near-infrared diffuse correlation spectroscopy (NIRS-DOS) were used to follow microvascular cerebral hemodynamics in the frontal lobes of the cerebral cortex. Changes in cerebral blood flow (CBF), total hemoglobin concentration (THC), and cerebral blood oxygen saturation (StO2) were analyzed.

RESULTS

We considered 3283 obstructive apnea/hypopnea events from sixteen OSA patients (Age (median, interquartile range) 57 (52-64.5); females 25%; AHI (apnea-hypopnea index) 84.4 (76.1-93.7)). A biphasic response (maximum/minimum followed by a minimum/maximum) was observed for each cerebral hemodynamic variable (CBF, THC, StO2), heart rate and peripheral arterial oxygen saturation (SpO2). Changes of the StO2 followed the dynamics of the SpO2, and were out of phase from the THC and CBF. Longer events were associated with larger CBF changes, faster responses and slower recoveries. Moreover, the extrema of the response to obstructive hypopneas were lower compared to apneas (p < .001).

CONCLUSIONS

Obstructive apneas/hypopneas cause profound, periodic changes in cerebral hemodynamics, including periods of hyper- and hypo-perfusion and intermittent cerebral hypoxia. The duration of the events is a strong determinant of the cerebral hemodynamic response, which is more pronounced in apnea than hypopnea events.

Comparison of Near-Infrared Spectroscopy-Based Cerebral Autoregulatory Indices in Extremely Low Birth Weight Infants

BACKGROUND

Premature infants are born with immature cerebral autoregulation function and are vulnerable to pressure passive cerebral circulation and subsequent brain injury. Measurements derived from near-infrared spectroscopy (NIRS) have enabled continuous assessment of cerebral vasoreactivity. Although NIRS has enabled a growing field of research, the lack of clear standardization in the field remains problematic. A major limitation of current literature is the absence of a comparative analysis of the different methodologies.

OBJECTIVES

To determine the relationship between NIRS-derived continuous indices of cerebral autoregulation in a cohort of extremely low birth weight (ELBW) infants.

METHODS

Premature infants of birth weight 401-1000 g were studied during the first 72 h of life. The cerebral oximetry index (COx), hemoglobin volume index (HVx), and tissue oxygenation heart rate reactivity index (TOHRx) were simultaneously calculated. The relationship between each of the indices was assessed with Pearson correlation.

RESULTS

Fifty-eight infants with a median gestational age of 25.8 weeks and a median birth weight of 738 g were included. Intraventricular hemorrhage (IVH) was detected in 33% of individuals. COx and HVx demonstrated the highest degree of correlation, although the relationship was moderate at best (r = 0.543, p < 0.001). No correlation was found either between COx and TOHRx (r = 0.318, p < 0.015) or between HVx and TOHRx (r = 0.287, p < 0.029). No significant differences in these relationships were found with respect to IVH and no IVH in subgroup analysis.

CONCLUSIONS

COx, HVx, and TOHRx are not numerically equivalent. Caution must be applied when interpreting or comparing results based on different methodologies for measuring cerebral autoregulation. Uniformity regarding data acquisition and analytical methodology are needed to firmly establish a gold standard for neonatal cerebral autoregulation monitoring.

Impact of Stepwise Recruitment Maneuvers on Cerebral Hemodynamics: Experimental Study in Neonatal Model

BACKGROUND

Lung recruitment maneuvers (LRMs) have been demonstrated to be effective in avoiding atelectasis during general anesthesia in the pediatric population. Performing these maneuvers is safe at the systemic hemodynamic and respiratory levels.

AIMS

We aimed to evaluate the impact of a stepwise LRM and individualized positive end-expiratory pressure (PEEP) on cerebral hemodynamics in an experimental neonatal model.

METHODS

Eleven newborn pigs (less than 72 h old, 2.56 ± 0.18 kg in weight) were included in the study. The LRM was performed under pressure-controlled ventilation with a constant driving pressure (15 cmH2O) in a stepwise increasing PEEP model. The target peak inspiratory pressure (PIP) was 30 cmH2O and the PEEP was 15 cmH2O. The following hemodynamic variables were monitored using the PICCO® system: mean arterial pressure (MAP), central venous pressure (CVP), and cardiac output (CO). The cerebral hemodynamics variables monitored were intracranial pressure (ICP) (with an intraparenchymal Camino® catheter) and cerebral oxygen saturation (rSO2) (with the oximetry monitor INVOS 5100® system). The following respiratory parameters were monitored: oxygen saturation, fraction of inspired oxygen, partial pressure of oxygen, end-tidal carbon dioxide pressure, Pmean, PEEP, static compliance (Cstat), and dynamic compliance (Cdyn).

RESULTS

All LRMs were safely performed as scheduled without any interruptions. Systemic hemodynamic stability was maintained during the lung recruitment maneuver. No changes in ICP occurred. We observed an improvement in rSO2 after the maneuver (+5.8%).

CONCLUSIONS

Stepwise LRMs are a safe tool to avoid atelectasis. We did not observe an impairment in cerebral hemodynamics but an improvement in cerebral oxygenation.

Force sensor reduced measurement error compared with verbal command during sit-to-stand assessment of cerebral autoregulation

Current methods estimate the time delay (TD) before the onset of dynamic cerebral autoregulation (dCA) from verbal command to stand. A force sensor used during a sit-to-stand dCA measure provides an objective moment an individual stands (arise-and-off, AO). We hypothesized that the detection of AO would improve the accuracy of TD compared with estimation. We measured middle cerebral artery blood velocity (MCAv) and mean arterial pressure (MAP) for 60 s sitting followed by 2-min standing, three times separated by 20 min. TD was calculated as the time from: (1) verbal command and (2) AO, until an increase in cerebrovascular conductance index (CVCi = MCAv/MAP). Sixty-five participants were enrolled: young adults (n = 25), older adults (n = 20), and individuals post-stroke (n = 20). The TD calculated from AO (x ¯ $$ \overline{x} $$  = 2.98 ± 1.64 s) was shorter than TD estimated from verbal command (x ¯ $$ \overline{x} $$  = 3.35 ± 1.72 s, η2  = 0.49, p < 0.001), improving measurement error by ~17%. TD measurement error was not related to age or stroke. Therefore, the force sensor provided an objective method to improve the calculation of TD compared with current methods. Our data support using a force sensor during sit-to-stand dCA measures in adults across the lifespan and post-stroke.

Enhanced Cerebral Hemodynamics and Cognitive Function Via Knockout of Dual-Specificity Protein Phosphatase 5

Alzheimer's Disease (AD) and Alzheimer's Disease-Related Dementias (ADRD) are neurodegenerative disorders. Recent studies suggest that cerebral hypoperfusion is an early symptom of AD/ADRD. Dual-specificity protein phosphatase 5 (DUSP5) has been implicated in several pathological conditions, including pulmonary hypertension and cancer, but its role in AD/ADRD remains unclear. The present study builds on our previous findings, demonstrating that inhibition of ERK and PKC leads to a dose-dependent dilation of the middle cerebral artery and penetrating arteriole, with a more pronounced effect in Dusp5 KO rats. Both ERK and PKC inhibitors resulted in a significant reduction of myogenic tone in vessels from Dusp5 KO rats. Dusp5 KO rats exhibited stronger autoregulation of the surface but not deep cortical cerebral blood flow. Inhibition of ERK and PKC significantly enhanced the contractile capacity of vascular smooth muscle cells from both strains. Finally, a significant improvement in learning and memory was observed in Dusp5 KO rats 24 hours after initial training. Our results suggest that altered vascular reactivity in Dusp5 KO rats may involve distinct mechanisms for different vascular beds, and DUSP5 deletion could be a potential therapeutic target for AD/ADRD. Further investigations are necessary to determine the effects of DUSP5 inhibition on capillary stalling, blood-brain barrier permeability, and neurodegeneration in aging and disease models.

Altered Cerebral Vasoreactivity on Transcranial Color-Coded Sonography Related to Akinetic-Rigid Phenotype of Parkinson's Disease: Interim Analysis of a Cross-Sectional Study

BACKGROUND

A correlation between worse functional outcomes in Parkinson's disease (PD) patients with cerebrovascular disease (CVD) or the Akinetic-rigid phenotype has been argued in recent studies. We aimed to evaluate the association of cerebral hemodynamics impairments, assessed by Transcranial Color-coded Doppler sonography (TCCS), on PD patients with different phenotypes of the disease and with risk factors for CVD.

METHODOLOGY

Idiopathic PD patients (n = 51) were divided into motor subtypes: Akinetic-rigid (AR) (n = 27) and Tremor-dominant (TD) (n = 24) and into two groups regarding vascular risk factors: when ≥2 were present (PDvasc) (n = 18) and <2 (PDnvasc) (n = 33). In a parallel analysis, the Fazekas scale on brain magnetic resonance imaging (MRI) was applied to a sample to assess the degree of leukoaraiosis. TCCS examinations were prospectively performed obtaining middle cerebral artery Mean Flow Velocities (Vm), Resistance Index (RI), and Pulsatility Index (PI). The Breath-Holding Index (BHI) was calculated to assess cerebrovascular reactivity (cVR). Standardized functional scales were administered (UPDRS III and Hoehn&Yahr).

RESULTS

The phenotype groups were similar in age, disease duration and demographic parameters, but there were significantly higher H&Y scores than TD group. cVR was impaired in 66.7% of AR vs. 37.5% of TD. AR group exhibited lower BHI (0.53 ± 0.31 vs. 0.91 ± 0.62; p = 0.000), lower Vm after apnea (44.3 ± 9.0 cm/s vs. 53.4 ± 11.4 cm/s; p = 0.003), higher PI (0.91 ± 0.26 vs. 0.76 ± 0.12; p = 0.000) and RI (0.58 ± 0.11 vs. 0.52 ± 0.06; p = 0.021). PDvasc group showed higher PI (0.98 vs. 0.76; p = 0.001) and higher frequency of altered cVR (72.2% vs. 42.2%; p = 0.004). There was a significant predominance of higher values on Fazekas scale in the PDvasc group. We found no difference between the Fazekas scale when comparing motor subtypes groups but there was a trend toward higher scores in the AR phenotype.

CONCLUSIONS

TCCS, a cost-effective method, displayed impaired cVR in Parkinsonian patients with risk factors for CVD with higher degree of MRI leukoaraiosis. PD patients with the AR disease phenotype also presented impaired cVR on TCCS and greater functional impairment, although with just a trend to higher scores on MRI Fazekas.

Preictal neuronal and vascular activity precedes the onset of childhood absence seizure: direct current potential shifts and their correlation with hemodynamic activity

SIGNIFICANCE AIMS

The neurovascular mechanisms underlying the initiation of absence seizures and their dynamics are still not well understood. The objective of this study was to better noninvasively characterize the dynamics of the neuronal and vascular network at the transition from the interictal state to the ictal state of absence seizures and back to the interictal state using a combined electroencephalography (EEG), functional near-infrared spectroscopy (fNIRS), and diffuse correlation spectroscopy (DCS) approach. The second objective was to develop hypotheses about the neuronal and vascular mechanisms that propel the networks to the 3-Hz spikes and wave discharges (SWDs) observed during absence seizures.

APPROACHES

We evaluated the simultaneous changes in electrical (neuronal) and optical dynamics [hemodynamic, with changes in (Hb) and cerebral blood flow] of 8 pediatric patients experiencing 25 typical childhood absence seizures during the transition from the interictal state to the absence seizure by simultaneously performing EEG, fNIRS, and DCS.

RESULTS

Starting from ∼ 20    s before the onset of the SWD, we observed a transient direct current potential shift that correlated with alterations in functional fNIRS and DCS measurements of the cerebral hemodynamics detecting the preictal changes.

DISCUSSION

Our noninvasive multimodal approach highlights the dynamic interactions between the neuronal and vascular compartments that take place in the neuronal network near the time of the onset of absence seizures in a very specific cerebral hemodynamic environment. These noninvasive approaches contribute to a better understanding of the electrical hemodynamic environment prior to seizure onset. Whether this may ultimately be relevant for diagnostic and therapeutic approaches requires further evaluation.

Reduced-order modeling and analysis of dynamic cerebral autoregulation via diffusion maps

OBJECTIVE

A data-driven technique for parsimonious modeling and analysis of dynamic cerebral autoregulation (DCA) is developed based on the concept of diffusion maps. Specifically, first, a state-space description of DCA dynamics is considered based on arterial blood pressure (ABP), cerebral blood flow velocity (CBFV), and their time derivatives. Next, an eigenvalue analysis of the Markov matrix of a random walk on a graph over the dataset domain yields a low-dimensional representation of the intrinsic dynamics. Further dimension reduction is made possible by accounting only for the two most significant eigenvalues. The value of their ratio indicates whether the underlying system is governed by active or hypoactive dynamics, indicating healthy or impaired DCA function, respectively. We assessed the reliability of the technique by considering healthy individuals and patients with unilateral ICA stenosis or occlusion. We computed the sensitivity of the technique to detect the presumed side-to-side difference in the DCA function of the second group (assuming hypoactive dynamics on the occluded or stenotic side), using McNemar's chi square test. The results were compared with transfer function analysis (TFA). The performance of the two methods was also compared under the assumption of missing data.

MAIN RESULTS

Both diffusion maps and TFA suggested a physiological side-to-side difference in the DCA of ICA stenosis or occlusion patients with a sensitivity of 77% and 58%, respectively. Further, both two methods suggested the difference between the occluded or stenotic side and any two sides of the healthy group. However, the diffusion maps captured additional difference between the unoccluded side and the healthy group, that TFA did not. Furthermore, compared to TFA, diffusion maps exhibited superior performance when subject to missing data.

SIGNIFICANCE

The eigenvalues ratio derived using the diffusion maps technique can be used as a reliable and robust biomarker for assessing how active the intrinsic dynamics of the autoregulation is and for indicating healthy versus impaired DCA function.

Challenging the Pleiotropic Effects of Repetitive Transcranial Magnetic Stimulation in Geriatric Depression: A Multimodal Case Series Study

BACKGROUND

Although the antidepressant potential of repetitive transcranial magnetic stimulation (rTMS), the pleiotropic effects in geriatric depression (GD) are poorly investigated. We tested rTMS on depression, cognitive performance, growth/neurotrophic factors, cerebral blood flow (CBF) to transcranial Doppler sonography (TCD), and motor-evoked potentials (MEPs) to TMS in GD.

METHODS

In this case series study, six drug-resistant subjects (median age 68.0 years) underwent MEPs at baseline and after 3 weeks of 10 Hz rTMS on the left dorsolateral prefrontal cortex. The percentage change of serum nerve growth factor, vascular endothelial growth factor, brain-derived growth factor, insulin-like growth factor-1, and angiogenin was obtained. Assessments were performed at baseline, and at the end of rTMS; psychocognitive tests were also repeated after 1, 3, and 6 months.

RESULTS

Chronic cerebrovascular disease was evident in five patients. No adverse/undesirable effect was reported. An improvement in mood was observed after rTMS but not at follow-up. Electrophysiological data to TMS remained unchanged, except for an increase in the right median MEP amplitude. TCD and neurotrophic/growth factors did not change.

CONCLUSIONS

We were unable to detect a relevant impact of high-frequency rTMS on mood, cognition, cortical microcircuits, neurotrophic/growth factors, and CBF. Cerebrovascular disease and exposure to multiple pharmacological treatments might have contributed.

[Three-dimensional pseudo-continuous arterial spin labeling for evaluation of cerebral hemodynamic changes after revascularization in adult patients with moyamoya disease]

OBJECTIVE

To evaluate cerebral hemodynamic changes using three-dimensional pseudo-continuous arterial spin labeling (3D-pCASL) and its association with the changes of neurological symptoms in adult patients with moyamoya disease after revascularization.

METHODS

We prospectively collected the clinical and radiographic data of 40 adult patients with moyamoya disease diagnosed by digital subtraction angiography (DSA) or magnetic resonance angiography (MRA) undergoing unilateral superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis. All the patients underwent 3D-pCASL examination before and after the surgery, and were followed up for 3 to 11 months after the operation. The region of interest (ROI) was located in the middle cerebral artery cortical territory covering the surgical side and ipsilateral cerebellar hemisphere. Cerebral blood flow (CBF) and relative CBF (rCBF) values were compared before and after the surgery, and the changes in cerebral hemodynamics were evaluated. The correlations were analyzed between preoperative rCBF and Suzuki stage and between the changes in postoperative neurological symptoms and rCBF.

RESULTS

The mean CBF of the patients increased significantly from 53.96±10.04 mL·100 g^-1·min^-1 to 58.90±13.57 mL·100 g^-1·min^-1 after the operation (t=-3.068, P=0.004); the mean rCBF also increased significantly after the operation (0.96 ± 0.14 vs 1.15 ± 0.18; t=-7.155, P < 0.001). The changes in postoperative neurological symptoms were significantly correlated with the changes in rCBF (P=0.017) and the type of disease onset (P < 0.001).

CONCLUSION

3D-pCASL is an valuable means for noninvasive monitoring of hemodynamic changes after revascularization in adult patients with moyamoya disease without the use of contrast agent.

Dynamic alterations in cerebral hemodynamics measured by portable near-infrared spectroscopy in orthostatic hypotension and intolerance

BACKGROUND

We aimed to evaluate dynamic alterations in cerebral total hemoglobin concentration (HbT) in individuals with orthostatic hypotension (OH) and orthostatic intolerance (OI) symptoms using a portable NIRS system.

METHODS

Participants comprised 238 individuals (mean age, 47.9 years) without a history of cardiovascular, neurodegenerative, or cerebrovascular diseases, including those with unexplained OI symptoms and healthy volunteers. Participants were categorized by the presence of OH based on the supine-to-stand blood pressure (BP) drop and OI symptoms using on OH questionnaires: classic OH (OH-BP), OH symptoms alone (OH-Sx), and control groups. Random case-control matching sets were constructed, resulting in 16 OH-BP and 69 OH-Sx-control sets. The time-derivative of HbT change in the prefrontal cortex during the squat-to-stand maneuver was measured using a portable near-infrared spectroscopy system.

RESULTS

There were no differences in demographics, baseline BP, and heart rate among matched sets. The peak-time of maximum slope variation in HbT change, indicating the recovery rate and speed of cerebral blood volume (CBV) change, was significantly longer in OH-Sx and OH-BP groups than in the control group under transition to a standing position after squatting. In the OH-BP subgrouping, the peak-time of maximum slope variation in HbT change was significantly longer only in OH-BP with OI symptoms, but did not differ between OH-BP without OI symptoms and controls.

CONCLUSIONS

Our results suggest that OH and OI symptoms are associated with dynamic alterations in cerebral HbT. Regardless of the severity of the postural BP drop, OI symptoms are associated with prolonged CBV recovery.

Capillary transit time heterogeneity inhibits cerebral oxygen metabolism in patients with reduced cerebrovascular reserve capacity from steno-occlusive disease

The healthy cerebral perfusion demonstrates a homogenous distribution of capillary transit times. A disruption of this homogeneity may inhibit the extraction of oxygen. A high degree of capillary transit time heterogeneity (CTH) describes that some capillaries have very low blood flows, while others have excessively high blood flows and consequently short transit times. Very short transit times could hinder the oxygen extraction due to insufficient time for diffusion of oxygen into the tissue. CTH could be a consequence of cerebral vessel disease. We examined whether patients with cerebral steno-occlusive vessel disease demonstrate high CTH and if elevation of cerebral blood flow (CBF) by administration of acetazolamide (ACZ) increases the cerebral metabolic rate of oxygen (CMRO₂), or if some patients demonstrate reduced CMRO₂ related to detrimental CTH. Thirty-four patients and thirty-one healthy controls participated. Global CBF and CMRO₂ were acquired using phase-contrast MRI. Regional brain maps of CTH were acquired using dynamic contrast-enhanced MRI. Patients with impaired cerebrovascular reserve capacity demonstrated elevated CTH and a significant reduction of CMRO₂ after administration of ACZ, which could be related to high CTH. Impaired oxygen extraction from CTH could be a contributing part of the declining brain health observed in patients with cerebral vessel disease.

Early cerebral hemodynamic changes following unilateral carotid artery stenting in patients with different degrees of carotid stenosis

Background

Few studies have focused on cerebral hemodynamics in the early stage following carotid artery stenting (CAS). This retrospective cohort study aimed to investigate cerebral hemodynamic changes within 6 hours of unilateral CAS in patients with different degrees of carotid stenosis.

Methods

A total of 104 patients who underwent CAS accompanied by transcranial color-code Doppler or transcranial Doppler were enrolled in the study. The participants were divided into the following 3 groups based on the degree of carotid stenosis: severe stenosis group, extreme stenosis group, and near occlusion group. Bilateral middle cerebral artery (MCA) peak systolic velocity (PSV) and pulsatility index (PI) were measured using transcranial color-code Doppler before and 1 and 3 hours following CAS. Blood pressure, MCA-PSV, and PI were compared among the 3 groups.

Results

At 1 hour following CAS, ipsilateral MCA-PSV increased compared to the baseline in the severe stenosis group [84±21 vs. 93±27 cm/s; 8.1%; interquartile range (IQR), 1.4-20.1%; P<0.001]. A similar hemodynamic change, but of a larger magnitude, was observed in the extreme stenosis group (83±24 vs. 100±29 cm/s; 20.8%; IQR, 5.3-33.1%; P<0.001) and near occlusion group (73±24 vs. 109±29 cm/s, 45.8%; IQR, 24.3-73.1%; P<0.001). At 3 hours after CAS, the hemodynamic changes were the same as those at 1 hour. PI increased in all 3 groups following CAS. A subgroup analysis was performed according to symptoms, sex, smoking status, history of hypertension, and presence of hyperlipidemia or diabetes, and the increase in ipsilateral MCA-PSV was not significant. In terms of adverse events, only 4 patients in the near occlusion group experienced transient post-CAS hyperperfusion.

Conclusions

The ipsilateral MCA-PSV and PI in patients following unilateral CAS increased significantly in the initial hours. The increase in ipsilateral MCA-PSV was considerably higher in patients with a severe degree of stenosis. Near occlusion of the carotid artery was an independent risk factor for hyperperfusion after unilateral CAS.

A magnetic resonance imaging-based computational analysis of cerebral hemodynamics in patients with carotid artery stenosis

Management of asymptomatic carotid artery stenosis (CAS) relies on measuring the percentage of stenosis. The aim of this study was to investigate the impact of CAS on cerebral hemodynamics using magnetic resonance imaging (MRI)-informed computational fluid dynamics (CFD) and to provide novel hemodynamic metrics that may improve the understanding of stroke risk. CFD analysis was performed in two patients with similar degrees of asymptomatic high-grade CAS. Three-dimensional anatomical-based computational models of cervical and cerebral blood flow were constructed and calibrated patient-specifically using phase-contrast MRI flow and arterial spin labeling perfusion data. Differences in cerebral hemodynamics were assessed in preoperative and postoperative models. Preoperatively, patient 1 demonstrated large flow and pressure reductions in the stenosed internal carotid artery, while patient 2 demonstrated only minor reductions. Patient 1 exhibited a large amount of flow compensation between hemispheres (80.31%), whereas patient 2 exhibited only a small amount of collateral flow (20.05%). There were significant differences in the mean pressure gradient over the stenosis between patients preoperatively (26.3 vs. 1.8 mmHg). Carotid endarterectomy resulted in only minor hemodynamic changes in patient 2. MRI-informed CFD analysis of two patients with similar clinical classifications of stenosis revealed significant differences in hemodynamics which were not apparent from anatomical assessment alone. Moreover, revascularization of CAS might not always result in hemodynamic improvements. Further studies are needed to investigate the clinical impact of hemodynamic differences and how they pertain to stroke risk and clinical management.

Dynamic cerebral autoregulation measured by diffuse correlation spectroscopy

Dynamic cerebral autoregulation (dCA) can be derived from spontaneous oscillations in arterial blood pressure (ABP) and cerebral blood flow (CBF). Transcranial Doppler (TCD) measures CBF-velocity and is commonly used to assess dCA. Diffuse correlation spectroscopy (DCS) is a promising optical technique for non-invasive CBF monitoring, so here we aimed to validate DCS as a tool for quantifying dCA. In 33 healthy adults and 17 acute ischemic stroke patients, resting-state hemodynamic were monitored simultaneously with high-speed (20 Hz) DCS and TCD. dCA parameters were calcaulated by a transfer function analysis using a Fourier decomposition of ABP and CBF (or CBF-velocity). Strong correlation was found between DCS and TCD measured gain (magnitude of regulation) in healthy volunteers (r = 0.73, p < 0.001) and stroke patients (r = 0.76, p = 0.003). DCS-gain retained strong test-retest reliability in both groups (ICC 0.87 and 0.82, respectively). DCS and TCD-derived phase (latency of regulation) did not significantly correlate in healthy volunteers (r = 0.12, p = 0.50) but moderately correlated in stroke patients (r = 0.65, p = 0.006). DCS-derived phase was reproducible in both groups (ICC 0.88 and 0.90, respectively). High-frequency DCS is a promising non-invasive bedside technique that can be leveraged to quantify dCA from resting-state data, but the discrepancy between TCD and DCS-derived phase requires further investigation.

Cerebrovascular Impedance as a Function of Cerebral Perfusion Pressure

Goal: Cerebrovascular impedance is modulated by a vasoactive autoregulative mechanism in response to changes in cerebral perfusion pressure. Characterization of impedance and the limits of autoregulation are important biomarkers of cerebral health. We developed a method to quantify impedance based on the spectral content of cerebral blood flow and volume at the cardiac frequency, measured with diffuse optical methods. Methods: In three non-human primates, we modulated cerebral perfusion pressure beyond the limits of autoregulation. Cerebral blood flow and volume were measured with diffuse correlation spectroscopy and near-infrared spectroscopy, respectively. Results: We show that impedance can be used to identify the lower and upper limits of autoregulation. Conclusions: This impedance method may be an alternative method to measure autoregulation and a way of assessing cerebral health non-invasively at the clinical bedside.

Changes in hemodynamic response function components reveal specific changes in neurovascular coupling in type 2 diabetes

Type 2 Diabetes Mellitus (T2DM) is a metabolic disease that leads to multiple vascular complications with concomitant changes in human neurophysiology, which may lead to long-term cognitive impairment, and dementia. Early impairments of neurovascular coupling can be studied using event-related functional magnetic resonance imaging (fMRI) designs. Here, we aimed to characterize the changes in the hemodynamic response function (HRF) in T2DM to probe components from the initial dip to late undershoot. We investigated whether the HRF morphology is altered throughout the brain in T2DM, by extracting several parameters of the fMRI response profiles in 141 participants (64 patients with T2DM and 77 healthy controls) performing a visual motion discrimination task. Overall, the patients revealed significantly different HRFs, which extended to all brain regions, suggesting that this is a general phenomenon. The HRF in T2DM was found to be more sluggish, with a higher peak latency and lower peak amplitude, relative slope to peak, and area under the curve. It also showed a pronounced initial dip, suggesting that the initial avidity for oxygen is not compensated for, and an absent or less prominent but longer undershoot. Most HRF parameters showed a higher dispersion and variability in T2DM. In sum, we provide a definite demonstration of an impaired hemodynamic response function in the early stages of T2DM, following a previous suggestion of impaired neurovascular coupling. The quantitative demonstration of a significantly altered HRF morphology in separate response phases suggests an alteration of distinct physiological mechanisms related to neurovascular coupling, which should be considered in the future to potentially halt the deterioration of the brain function in T2DM.

Diabetes or calcium channel blocker contribute to cerebral hemodynamics after bypass surgery in adult patients with moyamoya disease

Background

Moyamoya disease (MMD) is a teratogenic and lethal disease. However, existing studies do not sufficiently indicate the impact factors. Therefore, we investigated the different impact factors on cerebral hemodynamics after revascularization in patients with MMD.

Methods

We retrospectively collected the clinical data of 233 adult patients with MMD who underwent revascularization surgery in the Department of Neurosurgery, Renmin Hospital of Wuhan University, from January 2015 to June 2021 for this retrospective cohort study. We analyzed the effects on hemodynamic improvement of age, sex, stroke type, early symptoms, Suzuki stage, history of hypertension, history of diabetes, and history of hyperlipidemia in patients with MMD. We also evaluated the efficacy of different revascularization strategies and we verified the effect of computed tomography perfusion (CTP) in evaluating cerebral hemodynamics.

Results

The CTP values demonstrated that δ cerebral blood volume (CBV) values were significantly higher in the combined group [1.01 (0.87-1.75)] relative to those in the indirect group [1.34 (1.01-1.63); P=0.027]. There was no statistical significance in the improvement of clinical symptoms and clinical prognosis between the indirect and combined groups. Patients with MMD with diabetes [δ mean transit time (MTT), 0.49 (0.35-0.70) vs. 0.72 (0.52-0.87); P<0.001] or calcium channel blocker (CCB) [δCBV, 1.46 (1.10-1.83) vs. 1.12 (0.93-1.54); P=0.001] had better cerebral hemodynamics than patients in non-diabetic group or non-CCB group after revascularization.

Conclusions

We didn't find differences in clinical outcome between indirect and combined revascularization in patients with MMD. we demonstrated that CTP values can be used as a way to detect postoperative cerebral hemodynamic changes in MMD patients. Interestingly, we found that MMD patients with diabetes or CCB showed better cerebral perfusion after revascularization.

Animal models for the study of intracranial hematomas (Review)

Intracranial hematomas (ICH) are a frequent condition in neurosurgical and neurological practices, with several mechanisms of primary and secondary injury. Experimental research has been fundamental for the understanding of the pathophysiology implicated with ICH and the development of therapeutic interventions. To date, a variety of different animal approaches have been described that consider, for example, the ICH evolutive phase, molecular implications and hemodynamic changes. Therefore, choosing a test protocol should consider the scope of each particular study. The present review summarized investigational protocols in experimental research on the subject of ICH. With this subject, injection of autologous blood or bacterial collagenase, inflation of intracranial balloon and avulsion of cerebral vessels were the models identified. Rodents (mice) and swine were the most frequent species used. These different models allowed improvements on the understanding of intracranial hypertension establishment, neuroinflammation, immunology, brain hemodynamics and served to the development of therapeutic strategies.

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

PURPOSE

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.

METHODOLOGY

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.

RESULTS

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).

CONCLUSION

fNIRS is a useful non-invasive modality for the assessment of DAVF, and could potentially assist in bedside monitoring of treatment response.

Temporal stability of the hemodynamic response function across the majority of human cerebral cortex

The hemodynamic response function (HRF) measured with functional magnetic resonance imaging is generated by vascular and metabolic responses evoked by brief (<4 s) stimuli. It is known that the human HRF varies across cortex, between subjects, with stimulus paradigms, and even between different measurements in the same cortical location. However, our results demonstrate that strong HRFs are remarkably repeatable across sessions separated by time intervals up to 3 months. In this study, a multisensory stimulus was used to activate and measure the HRF across the majority of cortex (>70%, with lesser reliability observed in some areas of prefrontal cortex). HRFs were measured with high spatial resolution (2‐mm voxels) in central gray matter to minimize variations caused by partial‐volume effects. HRF amplitudes and temporal dynamics were highly repeatable across four sessions in 20 subjects. Positive and negative HRFs were consistently observed across sessions and subjects. Negative HRFs were generally weaker and, thus, more variable than positive HRFs. Statistical measurements showed that across‐session variability is highly correlated to the variability across events within a session; these measurements also indicated a normal distribution of variability across cortex. The overall repeatability of the HRFs over long time scales generally supports the long‐term use of event‐related functional magnetic resonance imaging protocols.

Retinal Thickness Correlates with Cerebral Hemodynamic Changes in Patients with Carotid Artery Stenosis

Background: We aimed to assess the retinal structural and choroidal changes in carotid artery stenosis (CAS) patients and their association with cerebral hemodynamic changes. Asymptomatic and symptomatic patients with unilateral CAS were enrolled in our study. Material and methods: Swept-source optical coherence tomography (SS-OCT) was used to image the retinal nerve fiber layer (RNFL), ganglion cell-inner plexiform layer (GCIPL), while SS-OCT angiography (SS-OCTA) was used to image and measure the choroidal vascular volume (CVV) and choroidal vascular index (CVI). Computed Tomography Perfusion (CTP) was used to assess the cerebral perfusion parameters; relative perfusion (r) was calculated as the ratio of the value on the contralateral side to that on the ipsilateral side. Results: Compared with contralateral eyes, ipsilateral eyes showed significantly thinner RNFL (p < 0.001), GCIPL (p = 0.013) and CVV (p = 0.001). Relative cerebral blood volume (rCBV) showed a significant correlation with RNFL (p < 0.001), GCIPL (p < 0.001) and CVI (p = 0.027), while the relative permeability surface (rPS) correlated with RNFL (p < 0.001) and GCIPL (p < 0.001). Conclusions: Our report suggests that retinal and choroidal changes have the potential to detect hemodynamic changes in CAS patients and could predict the risk of stroke.

Cerebral Hemodynamics, Right-to-Left Shunt and White Matter Hyperintensities in Patients with Migraine with Aura, Young Stroke Patients and Controls

Background: Migraine with aura (MA) patients present an increased risk of cerebrovascular events. However, whether these patients present an increased white matter hyperintensities (WMHs) load compared to the general population is still under debate. Our study aimed to evaluate the relationship between cerebral hemodynamics, right-to-left shunt (RLS) and WMHs in MA patients, young patients with cryptogenic stroke or motor transient ischemic attack (TIA) and controls. Methods: We enrolled 30 MA patients, 20 young (<60 years) patients with cryptogenic stroke/motor TIA, and 10 controls. All the subjects underwent a transcranial Doppler bubble test to detect RLS and cerebral hemodynamics assessed by the breath holding index (BHI) for the middle (MCA) and posterior (PCA) cerebral arteries. Vascular risk factors were collected. The WMHs load on FLAIR MRI sequences was quantitatively assessed. Results: The stroke/TIA patients presented a higher prevalence of RLS (100%) compared with the other groups (p < 0.001). The MA patients presented a higher BHI compared with the other groups in the PCA (p = 0.010) and higher RLS prevalence (60%) than controls (30%) (p < 0.001). The WMHs load did not differ across groups. BHI and RLS were not correlated to the WMHs load in the groups. Conclusions: A preserved or more reactive cerebral hemodynamics and the presence of a RLS are likely not involved in the genesis of WMHs in MA patients. A higher BHI may counteract the risk related to their higher prevalence of RLS. These results need to be confirmed by further studies to be able to effectively identify the protective role of cerebral hemodynamics in the increased RLS frequency in MA patients.

Cerebral hemodynamics in children with sickle cell disease in India: An observational cohort study

India has the second highest number of cases of sickle cell disease (SCD) and affects the most socioeconomically disadvantaged communities living in a horizontal belt from Gujarat to Odisha state. Despite high prevalence, information about cerebral hemodynamics among children with SCD in India remains scarcely described. We performed transcranial Doppler (TCD) to assess cerebral hemodynamics among Indian children with SCD and evaluated their association with clinical and hematological parameters. Children aged 3-18years, diagnosed with SCD living in Raipur in Chhattisgarh and Ahmedabad in Gujarat state were recruited. TCD was performed to obtain flow velocities from middle cerebral (MCA), intracranial internal carotid (ICA) and basilar artery. Associations were evaluated between timed-average-mean-maximum velocities (TAMMV) and various clinical and hematological parameters. Our prospective study included 62 consecutive children with known SCD. Mean ± SD age of the study population was 9.8 ± 3.9 years and 31 (50%) were male. Mean ± SD hemoglobin was 8.64 ± 1.34 Gm/dL while the mean HbSS ± SD was 70.25 ± 15.27%. While 6 (9.6%) children had suffered from stroke during previous 2 years, 7 (11%) demonstrated abnormal TAMMV. Higher HbSS level along with history of iron chelation therapy, blood transfusion and/or stroke showed a trend towards having higher TAMMV. Stroke and cerebral hemodynamic alterations are common among Indian children with SCD. Larger studies with detailed neuroimaging and genetic evaluations are needed for better understanding, characterization, risk stratification as well as optimization of the timing of blood transfusion to reduce physical disabilities among Indian children with SCD.

Dynamics of the cerebral autoregulatory response to paced hyperventilation assessed using sub-component and time-varying analyses

Cerebral blood flow (CBF) can be altered by a change in partial pressure of arterial CO₂ (pCO₂), being reduced during hyperventilation (HPV). Critical closing pressure (CrCP) and resistance area product (RAP) are parameters which can be studied to understand this change, but their dynamic response has not been investigated during paced HPV (PHPV). Seventy five participants had recordings at rest and during PHPV. Blood pressure (BP) (Finometer), bilateral CBF velocity (CBFV) (transcranial Doppler), end-tidal CO₂ (capnography) and heart rate (HR) were recorded continuously. Subcomponent analysis (SCA) and time-varying CrCP, RAP and dynamic cerebral autoregulation (Autoregulation Index, ARI) were estimated comparing PHPV to poikilocapnia. PHPV caused a change in CBFV (p<0.01), EtCO₂, (p<0.01), HR (p<0.001) and RAP (p<0.01). SCA demonstrated RAP was the main parameter explaining the changes in CBFV due to PHPV. The time-varying step responses for CBFV and RAP during PHPV demonstrated considerable non-stationarity compared to poikilocapnia (p<0.00001). Although time-varying ARI was temporarily depressed, after 60 s of PHPV it was significantly higher (6.81 ± 1.88) (p<0.0001) than in poikilocapnia (5.08 ± 1.86). The mean plateau of the RAP step response was -98.3 ± 58.8 % 60 s after the onset of PHPV but -71.7 ± 45.0 % for poikilocapnia (p=0.0026), with no corresponding changes in CrCP (p=0.6). Further work is needed to assess the role of sex and aging in our findings, and the potential for using RAP and CrCP to improve the sensitivity and specificity of CO₂ reactivity studies in cerebrovascular conditions.

Individual Watershed Areas in Sickle Cell Anemia: An Arterial Spin Labeling Study

Previous studies have pointed to a role for regional cerebral hemodynamic stress in neurological complications in patients with sickle cell anemia (SCA), with watershed regions identified as particularly at risk of ischemic tissue injury. Using single- and multi-inflow time (TI) arterial spin labeling sequences (ASL) in 94 patients with SCA and 42 controls, the present study sought to investigate cerebral blood flow (CBF) and bolus arrival times (BAT) across gray matter, white matter with early arrival times, and in individual watershed areas (iWSAs). In iWSAs, associations between hemodynamic parameters, lesion burden, white matter integrity, and general cognitive performance were also explored. In patients, increases in CBF and reductions in BAT were observed in association with reduced arterial oxygen content across gray matter and white matter with early arrival times using both sequences (all p < 0.001, d = -1.55--2.21). Across iWSAs, there was a discrepancy between sequences, with estimates based on the single-TI sequence indicating higher CBF in association with reduced arterial oxygen content in SCA patients, and estimates based on the multi-TI sequence indicating no significant between-group differences or associations with arterial oxygen content. Lesion burden was similar between white matter with early arrival times and iWSAs in both patients and controls, and using both sequences, only trend-level associations between iWSA CBF and iWSA lesion burden were observed in patients. Further, using the multi-TI sequence in patients, increased iWSA CBF was associated with reduced iWSA microstructural tissue integrity and slower processing speed. Taken together, the results highlight the need for researchers to consider BAT when estimating CBF using single-TI sequences. Moreover, the findings demonstrate the feasibility of multi-TI ASL for objective delineation of iWSAs and for detection of regional hemodynamic stress that is associated with reduced microstructural tissue integrity and slower processing speed. This technique may hold promise for future studies and treatment trials.

The Impact of Aging on the Association Between Aortic Stiffness and Cerebral Pulsatility Index

The central arteries dampen the pulsatile forces from myocardial contraction, limiting the pulsatility that reaches the cerebral vasculature, although there are limited data on this relationship with aging in humans. The purpose of this study was to determine the association between aortic stiffness and cerebral artery pulsatility index in young and older adults. We hypothesized that cerebral pulsatility index would be associated with aortic stiffness in older adults, but not in young adults. We also hypothesized that both age and aortic stiffness would be significant predictors for cerebral pulsatility index. This study included 23 healthy older adults (aged 62 ± 6 years) and 33 healthy young adults (aged 25 ± 4 years). Aortic stiffness was measured using carotid-femoral pulse wave velocity (cfPWV), while cerebral artery pulsatility index in the internal carotid arteries (ICAs), middle cerebral arteries (MCAs), and basilar artery were assessed using 4D Flow MRI. Cerebral pulsatility index was calculated as (maximum flow - minimum flow) / mean flow. In the combined age group, there was a positive association between cfPWV and cerebral pulsatility index in the ICAs (r = 0.487; p < 0.001), MCAs (r = 0.393; p = 0.003), and basilar artery (r = 0.576; p < 0.001). In young adults, there were no associations between cfPWV and cerebral pulsatility index in any of the arteries of interest (ICAs: r = 0.253; p = 0.156, MCAs: r = -0.059; p = 0.743, basilar artery r = 0.171; p = 0.344). In contrast, in older adults there was a positive association between cfPWV and cerebral pulsatility index in the MCAs (r = 0.437; p = 0.037) and basilar artery (r = 0.500; p = 0.015). However, the relationship between cfPWV and cerebral pulsatility index in the ICAs of the older adults did not reach the threshold for significance (r = 0.375; p = 0.078). In conclusion, age and aortic stiffness are significant predictors of cerebral artery pulsatility index in healthy adults. This study highlights the importance of targeting aortic stiffness in our increasingly aging population to reduce the burden of age-related changes in cerebral hemodynamics.

Intraoperative Early Venous Filling Phenomenon as an Intrinsic Sign of the Local Hemodynamic Change after Revascularization Surgery in a Patient with Adult Moyamoya Disease: Implications of a Potential Arteriovenous Shunt

After revascularization surgery for patients with moyamoya disease (MMD), local and global hemodynamic changes occur intraoperatively and in the early postoperative period. Local cerebral hyperperfusion and watershed shift ischemia are well-known perioperative pathologies after revascularization for MMD, but early venous filling phenomenon is markedly rare. We report the case of a 19-year-old woman with hemorrhagic-onset MMD who presented with grand mal seizure and subarachnoid hemorrhage. She underwent superficial temporal artery (STA)–middle cerebral artery (MCA) anastomosis combined with indirect pial synangiosis on the affected hemisphere. Intraoperatively, notable early arterial blood filling in the fine cortical vein was observed around the site of anastomosis right after the STA–MCA anastomosis under the surgical microscope and fluorescence indocyanine green video angiography. Recovery of consciousness after general anesthesia was normal, although she exhibited a focal seizure 1 hour later. Postoperative magnetic resonance imaging was not remarkable, and cerebral hemodynamics significantly improved in the acute stage after surgical revascularization. Considering the intrinsic vulnerability of the microvascular anatomy of MMD, the present case is notable because early venous filling was observed intraoperatively. This phenomenon suggests the existence of a potential arteriovenous shunt as an underlying pathology of MMD, but its implications in the early postoperative course should be further verified in a larger number of MMD patients undergoing surgical revascularization.

Lipid accumulation product as useful predictors of stroke: A correlation analysis between lipid accumulation index/cerebral vascular hemodynamics indexes and risk factors of stroke in 3264 people undergoing physical examination in Xinjiang

OBJECTIVE

To investigate the relationship between lipid accumulation index and cerebral hemodynamic integral value in 3264 people undergoing physical examination, so as to analyze the correlation between different lipid accumulation product index (LAP) levels and stroke risk factors.

METHODS

This cross-sectional study was conducted from January to December 2019 on 3264 adults at the age of 19 to 85 living in Urumqi, Xinjiang. The stroke related risk factors were evaluated by the questionnaire survey. The enrolled subjects were divided into Q1 group (n = 817), Q2 group (n = 815), Q3 group (n = 816) and Q4 group (n = 816) according to the quartile site at a low-to-high-score manner.

RESULTS

The proportion of males was significantly higher than that of females in Q2, Q3, and Q4 groups. The proportion of middle-aged people and the elderly in Q2, Q3, and Q4 groups was significantly higher than that of youths (P < .05). The proportion of patients with history of hypertension, hyperlipidemia, physical inactivity, and smoking, and the levels of systolic blood pressure, diastolic blood pressure, fasting blood glucose, total cholesterol, high-density cholesterol, low-density cholesterol, triglyceride, body mass index, waist circumference increased with the increase of LAP level in different groups (P < .05). On both sides of the cerebral hemodynamic integral value (CVHI) index, Vmean, Vmax, Vmin showed a decreasing trend whereas peripheral resistance, pulse velocity, Zcv, dynamic resistance, critical pressure level, difference between diastolic and critical pressure showed an increase trend with the increase of LAP level. The normal rate of CVHI in 4 groups (>75 points) was 97.4%, 89.7%, 87.0, and 80.8%, respectively, showing a decreasing trend. Logistic regression results showed that the higher the LAP, the higher the abnormal risk of CVHI.

CONCLUSION

There is a positive correlation between LAP and CVHI, the higher the LAP, the higher the risk of CVHI abnormality, which should be concerned seriously.

Low frequency cerebral arterial and venous flow oscillations in healthy neonates measured by NeoDoppler

BACKGROUND

A cerebroprotective effect of low frequency oscillations (LFO) in cerebral blood flow (CBF) has been suggested in adults, but its significance in neonates is not known. This observational study evaluates normal arterial and venous cerebral blood flow in healthy neonates using NeoDoppler, a novel Doppler ultrasound system which can measure cerebral hemodynamics continuously.

METHOD

Ultrasound Doppler data was collected for 2 h on the first and second day of life in 36 healthy term born neonates. LFO (0.04-0.15 Hz) were extracted from the velocity curve by a bandpass filter. An angle independent LFO index was calculated as the coefficient of variation of the filtered curve. Separate analyses were done for arterial and venous signals, and results were related to postnatal age and behavioral state (asleep or awake).

RESULTS

The paper describes normal physiologic variations of arterial and venous cerebral hemodynamics. Mean (SD) arterial and venous LFO indices (%) were 6.52 (2.55) and 3.91 (2.54) on day one, and 5.60 (1.86) and 3.32 (2.03) on day two. After adjusting for possible confounding factors, the arterial LFO index was estimated to decrease by 0.92 percent points per postnatal day (p < 0.001). The venous LFO index did not change significantly with postnatal age (p = 0.539). Arterial and venous LFO were not notably influenced by behavioral state.

CONCLUSION

The results indicate that arterial LFO decrease during the first 2 days of life in healthy neonates. This decrease most likely represents normal physiological changes related to the transitional period. A similar decrease for venous LFO was not found.

[Features of the parameters of hemodynamics and vascular tone of the brain in patients with depressive disorders]

OBJECTIVE

To study the features of hemodynamics and vascular tone of the brain in patients with depressive disorders.

MATERIAL AND METHODS

Fifty-four patients with depressive disorders and 54 conditionally healthy individuals were examined. The study of hemodynamics and vascular tone of the brain was carried out using rheoelectroencephalography.

RESULTS

Patients with depression in conditions of physiological rest have a statistically significantly higher tone of resistive vessels and medium-caliber arteries, as well as a lower level of elastic properties of the main arteries compared to healthy individuals.

CONCLUSION

The shape of the rheoelectroencephalogram of patients with depressive disorders was characterized by smoothing of the dicrotic wave and its displacement to the top, as well as a slight severity of incisure and an increase in the speed of propagation of the rheographic wave.