Transcranial doppler: Technique and common findings (Part 1)

Neurovascular coupling during dynamic upper body resistance exercise in healthy individuals

During unilateral static and rhythmic handgrip exercise, middle cerebral artery blood velocity (MCAv) increases in the contralateral side to the exercising limb. However, whether this neurovascular coupling-mediated increase in contralateral MCAv is apparent against a background of fluctuating perfusion pressure produced by dynamic resistance exercise (RE) is unclear. We examined the cerebral haemodynamic response to unilateral dynamic RE in 30 healthy individuals (female = 16, mean ± SD: age, 26 ± 6 years; height, 175 ± 10 cm; weight, 74 ± 15 kg; body mass index, 24 ± 5 kg m-2). Participants completed four sets of 10 paced repetitions (15 repetitions min-1) of unilateral bicep curl exercise at 60% of the predicted one-repetition maximum (7 ± 3 kg). Beat-to-beat blood pressure, bilateral MCAv and end-tidal carbon dioxide were measured throughout. One-way ANOVA was used to analyse cardiovascular variables and two-way ANOVA to analyse dependent cerebrovascular variables (side × sets, 2 × 5). A linear mixed model analysis was also performed to investigate the effects of end-tidal carbon dioxide and mean arterial blood pressure on MCAv. In comparison to baseline, within-exercise mean arterial blood pressure increased (P < 0.001) across the sets, whereas bilateral MCAv decreased (P < 0.001). However, no significant interaction effect was observed for any dependent variables (all P > 0.787). The linear mixed model revealed that end-tidal carbon dioxide had the greatest effect on MCAv (estimate = 1.019, t = 8.490, P < 0.001). No differences were seen in contralateral and ipsilateral MCAv during dynamic RE, suggesting that neurovascular coupling contributions during dynamic RE might be masked by other regulators, such as blood pressure.

The effects of habitual resistance exercise training on cerebrovascular responses to lower body dynamic resistance exercise: A cross-sectional study

Dynamic resistance exercise (RE) produces sinusoidal fluctuations in blood pressure with simultaneous fluctuations in middle cerebral artery blood velocity (MCAv). Some evidence indicates that RE may alter cerebrovascular function. This study aimed to examine the effects of habitual RE training on the within-RE cerebrovascular responses. RE-trained (n = 15, Female = 4) and healthy untrained individuals (n = 15, Female = 12) completed four sets of 10 paced repetitions (15 repetitions per minute) of unilateral leg extension exercise at 60% of predicted 1 repetition maximum. Beat-to-beat blood pressure, MCAv and end-tidal carbon dioxide were measured throughout. Zenith, nadir and zenith-to-nadir difference in mean arterial blood pressure (MAP) and mean MCAv (MCAvmean) for each repetition were averaged across each set. Two-way ANOVA was used to analyse dependent variables (training × sets), Bonferroni corrected t-tests were used for post hoc pairwise comparisons. Group age (26 ± 7 trained vs. 25 ± 6 years untrained, P = 0.683) and weight (78 ± 15 vs. 71 ± 15 kg, P = 0.683) were not different. During exercise average MAP was greater for the RE-trained group in sets 2, 3 and 4 (e.g., set 4: 101 ± 11 vs. 92 ± 7 mmHg for RE trained and untrained, respectively, post hoc tests all P = < 0.012). Zenith MAP and zenith-to-nadir MAP difference demonstrated a training effect (P < 0.039). Average MCAvmean and MCAvmean zenith-to-nadir difference was not different between groups (interaction effect P = 0.166 and P = 0.459, respectively). Despite RE-trained individuals demonstrating greater fluctuations in MAP during RE compared to untrained, there were no differences in MCAvmean. Regular RE may lead to vascular adaptations that stabilise MCAv during RE.

A narrative review of neuromonitoring modalities in critically ill children

Acute neurologic injury is common in critically ill children. Some conditions - such as traumatic brain injury, meningitis, and hypoxic-ischemic injury following cardiac arrest - require careful consideration of cerebral physiology. Specialized neuromonitoring techniques provide insight regarding patient-specific and disease-specific insight that can improve diagnostic accuracy, aid in targeting therapeutic interventions, and provide prognostic information. In this review, we will discuss recent innovations in invasive (e.g., intracranial pressure monitoring and related computed indices) and noninvasive (e.g., transcranial doppler, near-infrared spectroscopy) neuromonitoring techniques used in traumatic brain injury, central nervous system infections, and after cardiac arrest. We will discuss the pertinent physiological mechanisms interrogated by each technique and discuss available evidence for potential clinical application. We will also discuss the use of innovative neuromonitoring techniques to detect and manage neurologic complications in critically ill children with systemic illness, focusing on sepsis and cardiorespiratory failure requiring extracorporeal membrane oxygenation.

Prediction of cerebral infarction after bypass surgery in adult moyamoya disease: using pulsatility index on TCD

BACKGROUND

At present, the most effective treatment for symptomatic moyamoya disease (MMD) is surgery. However, the high incidence of postoperative complications is a serious problem plaguing the surgical treatment of MMD, especially the acute cerebral infarction. Decreased cerebrovascular reserve is an independent risk factor for ischemic infarction, and the pulsatility index (PI) of transcranial Doppler (TCD) is a common intuitive index for evaluating intracranial vascular compliance. However, the relationship between PI and the occurrence of ischemic stroke after operation is unclear.

OBJECTIVE

To explore whether the PI in the middle cerebral artery (MCA) could serve as a potential predictor for the occurrence of ischemic infarction after bypass surgery in MMD.

METHODS

We performed a retrospective analysis of data from 71 patients who underwent combined revascularization surgery, including superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis and encephalo-duro-myo-synangiosis (EDMS). The patients were divided into two groups according to the median of ipsilateral MCA-PI before operation, low PI group (MCA-PI < 0.614) and high PI group (MCA-PI ≥ 0.614). Univariate and multivariate regression analysis were used to explore risk factors affecting the occurrence of postoperative cerebral infarction.

RESULTS

Among the 71 patients with moyamoya disease, 11 patients had cerebral infarction within one week after revascularization. Among them, 10 patients' ipsilateral MCA-PI were less than 0.614, and another one's MCA- PI is higher than 0.614. Univariate analysis showed that the lower ipsilateral MCA-PI (0.448 ± 0.109 vs. 0.637 ± 0.124; P = 0.001) and higher Suzuki stage (P = 0.025) were linked to postoperative cerebral infarction. Multivariate analysis revealed that lower ipsilateral MCA-PI was an independent risk factor for predicting postoperative cerebral infarction (adjusted OR = 14.063; 95% CI = 6.265 ~ 37.308; P = 0.009).

CONCLUSIONS

A lower PI in the ipsilateral MCA may predict the cerebral infarction after combined revascularization surgery with high specificity. And combined revascularization appears to be safer for the moyamoya patients in early stages.

Comparing Intraocular Pressure, Ocular Blood Flow, and Retinal Nerve Fiber Layer Thickness in Early and Chronic Hypertensives With Normotensives

PURPOSE

To compare blood pressure (BP), intraocular pressure (IOP), ophthalmic artery flow (OAF) velocity, retinal nerve fiber layer (RNFL) thickness, and visual fields in newly diagnosed hypertension (HT) patients (before treatment), chronic HT (on antihypertensive medications >5 years) and normotensives.

METHODS

A prospective, cross-sectional study at a tertiary care centre in India. Three groups of 45 patients each: group 1 - early HT, group 2 - chronic HT, and Group 3 - normotensives, underwent evaluation of BP, IOP by Goldmann applanation tonometry (GAT), OAF velocity by transcranial doppler (TCD), RNFL analysis by spectral-domain optical coherence tomography (SD-OCT), and visual fields.

RESULTS

The BP was highest in early HT > chronic HT > normotensives (p < 0.001). The IOP of early HT, chronic HT, and normotensives were 15.87 ± 2.19 mmHg, 13.47 ± 1.92 mmHg, and 15.67 ± SD 1.75 mmHg (p < 0.001). The OAF velocity [peak systolic velocity (PSV), end-diastolic velocity (EDV) in cm/sec] was lowest in chronic HT (30.80 ± 7.05, 8.58 ± 1.58) < early HT (35.47 ± 5.34, 10.02 ± 1.74) < normotensives (36.29 ± 4.43, 10.44 ± 2.29), (p < 0.001). The average RNFL thickness was significantly lower in chronic HT (p = 0.022). The PSV, EDV, and MFV showed significant correlation with IOP (r = 0.247, p = 0.004; r = 0.206, p = 0.016; r = 0.266, p = 0.002) and average RNFL thickness (r = 0.309, p= <0.001; r = 0.277, p = 0.001; r = 0.341, p < 0.001).

CONCLUSIONS

Patients with chronic HT demonstrated the lowest retrobulbar flows, IOP and lower RNFL measurements. Lower ocular perfusion may be associated with lower IOP and may be a risk factor for end-organ damage (RNFL) independent of IOP.

Clinical applications of ultrasound in neurosurgery and neurocritical care: A narrative review

Ultrasonography (USG) has become an invaluable tool in the assessment of neurocritical patients in the operating theaters and critical care units. Due to its easy availability, reliability, safety, and repeatability, neuro-intensivists and neuro-anesthesiologists utilize USG to make a diagnosis, assess prognosis, and decide upon treatment. In neurocritical care units, USG has myriad indications for use, both systemic and neurologic. The neurological indications include the assessment of stroke, vasospasm, traumatic brain injury, brain death, acute brain damage, optic nerve sheath diameter, and pupillary reflexes to name a few. The systemic indications range from assessment of cardio-pulmonary function and intravascular volume status to detection of deep venous thromboses, vocal cord assessment in intubated patients, placement of central venous catheters, and percutaneous tracheostomy. In this narrative review, we iterate the clinical applications of USG in neuroanesthesia and neurocritical care, which we penned after searching relevant databases in PubMed, Medline, Ovid, and Google Scholar by using terms such as ‘applications of transcranial Doppler’, ‘optic nerve sheath diameter’, ‘USG applications in the critical care unit’, and so on. Our search database includes several research papers, neurocritical care books, review articles, and scientific databases. This article reviews various applications of USG in neuroanesthesia, neurosurgery, and neurocritical care.

Middle Cerebral Artery Blood Flow Velocity During Normal Pregnancy

BACKGROUND

The present study aimed to evaluate resting middle cerebral artery (MCA) blood flow velocities using transcranial Doppler ultrasound (TCD) in healthy women at different stages of pregnancy, and to compare these velocities with those of normal controls.

METHODS

A total of 105 healthy normotensive pregnant women and 25 non-pregnant healthy controls were included in the study. We formed 3 groups according to gestational age: first trimester (7 to 13 wk pregnant), second trimester (14 to 28 wk pregnant), and third trimester (29 to 42 wk pregnant). Age, body mass index, heart rate, arterial blood pressure, and hematological data were recorded and TCD was performed on the subjects. Regarding TCD, we evaluated the mean cerebral blood flow velocity, the peak systolic velocity, the end-diastolic flow velocity, S/D ratio, the pulsatility Index (PI) and the resistance Index (RI).

RESULTS

The MCA mean blood flow velocities differed significantly among the groups ( P <0.001) and were higher in the controls than those of the first trimester, second trimester, and third trimester groups ( P <0.01, P <0.001, P <0.001 respectively). The MCA mean and peak blood flow velocities, and the PI and RI decreased significantly with advancing gestation.

CONCLUSIONS

TCD is a noninvasive and non-toxic method of monitoring the adaptation of the maternal cerebral blood flow in pregnancy. The progressive decreases in the MCA mean and peak blood flow velocities, PI, and RI during gestation may be the result of chemical and neuronal factors. This study supports the need for additional studies using TCD to establish normative cerebral blood flow volumes throughout pregnancy.

Neuroimaging, wearable sensors, and blood-based biomarkers reveal hyperacute changes in the brain after sub-concussive impacts

Impacts in mixed martial arts (MMA) have been studied mainly in regard to the long-term effects of concussions. However, repetitive sub-concussive head impacts at the hyperacute phase (minutes after impact), are not understood. The head experiences rapid acceleration similar to a concussion, but without clinical symptoms. We utilize portable neuroimaging technology - transcranial Doppler (TCD) ultrasound and functional near infrared spectroscopy (fNIRS) - to estimate the extent of pre- and post-differences following contact and non-contact sparring sessions in nine MMA athletes. In addition, the extent of changes in neurofilament light (NfL) protein biomarker concentrations, and neurocognitive/balance parameters were determined following impacts. Athletes were instrumented with sensor-based mouth guards to record head kinematics. TCD and fNIRS results demonstrated significantly increased blood flow velocity (p = 0.01) as well as prefrontal (p = 0.01) and motor cortex (p = 0.04) oxygenation, only following the contact sparring sessions. This increase after contact was correlated with the cumulative angular acceleration experienced during impacts (p = 0.01). In addition, the NfL biomarker demonstrated positive correlations with angular acceleration (p = 0.03), and maximum principal and fiber strain (p = 0.01). On average athletes experienced 23.9 ± 2.9 g peak linear acceleration, 10.29 ± 1.1 rad/s peak angular velocity, and 1,502.3 ± 532.3 rad/s2 angular acceleration. Balance parameters were significantly increased following contact sparring for medial-lateral (ML) center of mass (COM) sway, and ML ankle angle (p = 0.01), illustrating worsened balance. These combined results reveal significant changes in brain hemodynamics and neurophysiological parameters that occur immediately after sub-concussive impacts and suggest that the physical impact to the head plays an important role in these changes.

Intracranial Atherosclerosis Increases the Risk of Postoperative Stroke After Cardiac Surgery: A Review and Meta-Analysis

BACKGROUND

Postoperative stroke is a devastating complication of cardiac surgery with high morbidity, mortality, and health care cost. Extracranial carotid atherosclerosis (ECAS) is a known risk factor for stroke; however, the impact of intracranial atherosclerosis (ICAS) remains unclear. To our knowledge, this is the first literature review of ICAS in cardiac surgery. We aimed to assess the prevalence, association with postoperative stroke, and perioperative management of ICAS in cardiac surgery.

METHOD

A search was performed to identify studies reporting rates of ICAS and stroke after cardiac surgery. Data extraction and primary outcomes for meta-analysis included the prevalence of preoperative ICAS and the association between ICAS and stroke. Risk ratios (RRs) and 95% confidence intervals (CIs) were pooled by random-effects modelling.

RESULTS

Seventeen studies were reviewed and seven were included in the meta-analysis, comprising 4,936 patients. Prevalence of intracranial atherosclerosis (ICAS) among cardiac surgery patients was 21% (95% CI 13%-32%). Patients with ICAS were more likely to develop postoperative stroke (RR 3.61; 95% CI 2.30-5.67; p<0.001). ICAS was more closely associated with stroke than ECAS. Preoperative brain perfusion single-photon emission computed tomography with acetazolamide challenge, staged intracerebral revascularisation, or conversion to off-pump coronary artery bypass grafting are described management options for ICAS.

CONCLUSION

Patients with ICAS are 3.61 times more likely to develop stroke after cardiac surgery. Known predictors for ICAS can be used to develop risk stratification screening tools. Further research with diverse cohorts is required to develop evidence-based guidelines for screening and management of ICAS in cardiac surgery.

The Relationship between Transcranial Doppler Ultrasonography and Visual Field Test Results in Glaucoma and Glaucoma Suspect Patients

PURPOSE

To evaluate the relationships between parameters of transcranial ultrasonography and results of visual field tests in patients with open angle glaucoma or suspected of having glaucoma.

METHODS

This retrospective study was based on data from medical records of patients who visited the Department of Ophthalmology in Kangbuk Samsung Hospital from January 1, 2016, to October 17, 2019, and underwent transcranial Doppler ultrasonography as part of a routine health examination. Ophthalmic data were visual acuity, intraocular pressure, optical coherence tomography, and Humphrey visual field test results. Retinal nerve fiber layer defect was confirmed by a glaucoma specialist. Patients' ophthalmic data, such as average ganglion cell layer thickness, visual field index, pattern standard deviation, and mean deviation, were divided into quartiles. Each ophthalmic artery parameter from transcranial Doppler ultrasonography was compared between quartiles.

RESULTS

A total of 162 patients were reviewed. There was no difference in Doppler ophthalmic artery (OA) parameters between patients with or without retinal nerve fiber layer defect. None of the quartile groups of average ganglion cell layer thickness showed significant difference in any OA parameters. Patients in the low-visual field index quartile showed significant low peak systolic velocities of OAs when adjusted for age, sex, and presence of diabetes mellitus or hypertension (p = 0.016). A higher pattern standard deviation showed lower peak systolic velocity (p = 0.046). There was no significant tendency between any other OA parameter and mean deviation value.

CONCLUSIONS

Our study suggests that hemodynamic parameters of ophthalmic arteries might be associated with visual field status of patients. Further large-population studies are needed in order to better understand the relationship between visual function and ocular blood flow.

Pathophysiology, Management, and Therapeutics in Subarachnoid Hemorrhage and Delayed Cerebral Ischemia: An Overview

Subarachnoid hemorrhage (SAH) is a type of hemorrhagic stroke resulting from the rupture of an arterial vessel within the brain. Unlike other stroke types, SAH affects both young adults (mid-40s) and the geriatric population. Patients with SAH often experience significant neurological deficits, leading to a substantial societal burden in terms of lost potential years of life. This review provides a comprehensive overview of SAH, examining its development across different stages (early, intermediate, and late) and highlighting the pathophysiological and pathohistological processes specific to each phase. The clinical management of SAH is also explored, focusing on tailored treatments and interventions to address the unique pathological changes that occur during each stage. Additionally, the paper reviews current treatment modalities and pharmacological interventions based on the evolving guidelines provided by the American Heart Association (AHA). Recent advances in our understanding of SAH will facilitate clinicians' improved management of SAH to reduce the incidence of delayed cerebral ischemia in patients.

Hyper-acute effects of sub-concussive soccer headers on brain function and hemodynamics

Introduction

Sub-concussive head impacts in soccer are drawing increasing research attention regarding their acute and long-term effects as players may experience thousands of headers in a single season. During these impacts, the head experiences rapid acceleration similar to what occurs during a concussion, but without the clinical implications. The physical mechanism and response to repetitive impacts are not completely understood. The objective of this work was to examine the immediate functional outcomes of sub-concussive level impacts from soccer heading in a natural, non-laboratory environment.

Methods

Twenty university level soccer athletes were instrumented with sensor-mounted bite bars to record impacts from 10 consecutive soccer headers. Pre- and post-header measurements were collected to determine hyper-acute changes, i.e., within minutes after exposure. This included measuring blood flow velocity using transcranial Doppler (TCD) ultrasound, oxyhemoglobin concentration using functional near infrared spectroscopy imaging (fNIRS), and upper extremity dual-task (UEF) neurocognitive testing.

Results

On average, the athletes experienced 30.7 ± 8.9 g peak linear acceleration and 7.2 ± 3.1 rad/s peak angular velocity, respectively. Results from fNIRS measurements showed an increase in the brain oxygenation for the left prefrontal cortex (PC) (p = 0.002), and the left motor cortex (MC) (p = 0.007) following the soccer headers. Additional analysis of the fNIRS time series demonstrates increased sample entropy of the signal after the headers in the right PC (p = 0.02), right MC (p = 0.004), and left MC (p = 0.04).

Discussion

These combined results reveal some variations in brain oxygenation immediately detected after repetitive headers. Significant changes in balance and neurocognitive function were not observed in this study, indicating a mild level of head impacts. This is the first study to observe hemodynamic changes immediately after sub-concussive impacts using non-invasive portable imaging technology. In combination with head kinematic measurements, this information can give new insights and a framework for immediate monitoring of sub-concussive impacts on the head.

Clinical study of transcranial sonography image characteristics in patients with obstructive sleep apnea

OBJECTIVE

This study aimed to explore the relationship between patients with obstructive sleep apnea (OSA) from subgroups of varying severity and substantia nigra (SN) hyperechogenicity as well as cerebral blood flow detected by transcranial sonography (TCS). The study also explored if there were differences in damage of the SN and in the cerebral blood flow between the bilateral sides.

METHODS

Right-handed men diagnosed with OSA by polysomnography were recruited from August 2018 to August 2020. The included patients were divided into 3 subgroups (mild, moderate, and severe OSA), and all patients underwent TCS.

RESULTS

Among the 157 study patients (30 with mild OSA, 25 moderate, and 102 severe), the overall prevalence of SN hyperechogenicity was 15% (23/157). The hyperechogenicity detection rates were 3% (4/157) in the right SN subgroup and 13% (20/157) in the left SN subgroup, which were significantly different. The left side always had reduced blood flow on TCS (P < 0.05). No correlation was observed between the severity of OSA and the detection rates of SN hyperechogenicity (P > 0.05).

CONCLUSION

Patients with OSA showed a higher detection rate of SN hyperechogenicity on the left compared with the right side. The left middle cerebral arteries had reduced blood flow, which was consistent with the more severe damage of the left SN. No relationship was observed between the severity of OSA and the detection rate of SN hyperechogenicity or hemodynamic parameters.

Transcranial Doppler Remote Positioning System with Virtual Reality Integration for Vestibular Studies

Transcranial doppler (TCD) ultrasound probes are an invaluable tool in cerebral blood flow (CBF) studies. Their operation demands maintaining consistent pose on the subject throughout the experimental protocol. However, the displacement of the TCD probe during vestibular studies is common and substantially prolongs the experiment or even terminates it. This is a significant challenge for integrating motion-based vestibular studies with CBF investigations. In response, a mechatronics system is designed to allow remote repositioning of the TCD probe during data collection experiments while the subject is wearing a head mounted virtual reality (VR) display and seated in a vestibular disorientation device. This paper presents the design, prototype, and operation of this mechatronics apparatus.Clinical Relevance- The mechatronics apparatus of this paper can enable motion-based vestibular studies that entail the use of CBF velocity measurement and head-mounted virtual reality display.

Cerebrovascular reactivity after functional activation of the Brain using Photic Stimulation in Migraine and Tension Type Headache: a transcranial doppler Ultrasonography Study

BACKGROUND

Previous studies in headache patients measured the cerebrovascular reactivity (CVR) in response to photic stimulation but they have yielded contradictory results. The purpose of study was to measure CVR of both migraine and chronic tension headache (TTH) patients in response to photic stimulation.

METHODS

The study included 37 migraineurs and 24 chronic TTH patients compared with 50 age- and sex-matched healthy volunteers. Peak systolic, end diastolic, mean flow velocities and CVR (PSV, EDV, MFV, and CVR) were measured using TCD ultrasonography of the middle, anterior, posterior cerebral and vertebral arteries (MCA, ACA, PCA, and VA) before and after 100 s of 14 Hz photic stimulation.

RESULTS

A three-way repeated measures ANOVA interaction with main factors of Vessels (MCA, ACA, PCA, VA), Time (pre-post photic) and Groups (migraine, TTH, and control group) revealed significant 3-way interactions for measures of PSV (P = 0.012) and MFV (P = 0.043). In the migraine patients there was significantly higher PSV, EDV, and MFV in the MCA, ACA, and PCA after photic stimulation compared with baseline. The CVR of the MCA was also significantly higher in migraineurs than controls. In the TTH group, there was significantly higher PSV, EDV, and MFV (P = 0.003, 0.012, 0.002 respectively) in the VA after photic stimulation than at baseline. The CVR was significantly higher in the VA of TTH patients than controls.

CONCLUSION

Compared with controls after photic stimulation, the higher CVR of the MCA in migraineurs and of the VA in TTH patients could be used as diagnostic tool to differentiate between the two types of headaches.

Transcranial Doppler Ultrasonography-Related Research in the Caribbean Region

Transcranial Doppler (TCD) ultrasonography is a non-invasive ultrasound technique that uses high-frequency sound waves to measure blood flow velocities in the cerebral vasculature. This review analyzes TCD research in the Caribbean region using a bibliometric analysis of 29 articles from PubMed. The articles were analyzed using Microsoft Excel 2016 and the VOSviewer software (Van Eck and Waltman, Leiden University, Centre for Science and Technology Studies (CWTS), www.vosviewer.com) and characterized various aspects of TCD research, including countries, research themes, authorship, journals, affiliations, and keywords. The majority of the 29 publications came from Cuba (38%), followed by the French West Indies (22%) and Jamaica (20%). Most TCD research focused on sickle cell disease (SCD), accounting for 45% of the studies, followed by 21% of articles on vasospasm and subarachnoid hemorrhage. The use of TCD in brain death and neuro-intensive care was also explored, constituting 17% of the studies. Alternative TCD-monitored treatment options for SCD, such as stem cell transplantation and hydroxyurea, were also frequently investigated. The most productive institutions were Hospital Clínico-Quirúrgico Hermanos Ameijeiras in Havana, Cuba, the Sickle Cell Unit at the University of West Indies (UWI) Mona in Jamaica, the Medical-Surgical Research Center (CIMEQ) in Havana, Cuba, and the SCD Reference Center in Guadeloupe and Martinique in the French West Indies. TCD has been identified as a cost-effective tool for real-time monitoring of cerebral blood flow in many clinical settings, including stroke and SCD, which are prevalent in the Caribbean. Although there is an increase in the trend of using TCD for neuromonitoring in the Caribbean, gaps still exist. Capacity-building initiatives, such as training programs for healthcare providers and the development of local TCD research networks, can improve access to TCD in resource-constrained settings to treat and neuromonitor patients cost-effectively.

Microembolic signal monitoring in patients with HeartMate 3 and HeartWare left ventricular assist devices: Association with antithrombotic treatment and cerebrovascular events

BACKGROUND

In patients with left ventricular assist devices (LVADs), ischemic and hemorrhagic stroke are dreaded complications. Predictive markers for these events are lacking. This study aimed to investigate the prevalence and predictive value of microembolic signals (MES) for stroke, detected by Transcranial Doppler sonography (TCD) in patients with HeartMate 3 (HM 3) or HeartWare (HW).

METHODS

A thirty-minute bilateral TCD monitoring of the middle cerebral artery (MCA) was performed in 62 outpatients with LVAD (HM 3 N = 31, HW N = 31) and 31 healthy controls. Prevalence and quantity of MES were investigated regarding clinical and laboratory parameters. Cerebrovascular events (CVE) were recorded on follow-up at 90 and 180 days.

RESULTS

MES were detected in six patients with HM 3, three patients with HW, and three controls. Within the LVAD groups, patients on monotherapy with vitamin-K-antagonist (VKA) without antiplatelet therapy were at risk for a higher count of MES (negative binomial regression: VKA: 1; VKA + ASA: Exp(B) = 0.005, 95%CI 0.001-0.044; VKA + clopidogrel: Exp(B) = 0.012, 95%CI 0.002-0.056). There was no association between the presence of MES and CVE or death on follow-up (p > 0.05).

CONCLUSION

For the first time, the prevalence of MES was prospectively investigated in a notable outpatient cohort of patients with HM 3 and HW. Despite optimized properties of the latest LVAD, MES remain detectable depending on antithrombotic therapy. No association between MES and CVE could be detected.

The impact of cerebral vasomotor reactivity on cerebrovascular diseases and cognitive impairment

The regulation of cerebral blood flow (CBF) is a complex and tightly controlled function ensuring delivery of oxygen and nutrients and removal of metabolic wastes from brain tissue. Cerebral vasoreactivity (CVR) refers to the ability of the nervous system to regulate CBF according to metabolic demands or changes in the microenvironment. This can be assessed through a variety of nuclear medicine and imaging techniques and protocols. Several studies have investigated the association of CVR with physiological and pathological conditions, with particular reference to the relationship with cognitive impairment and cerebrovascular disorders (CVD). A better understanding of the interaction between CVR and cognitive dysfunction in chronic and particularly acute CVD could help improving treatment and rehabilitation strategies in these patients. In this paper, we reviewed current knowledge on CVR alterations in the context of acute and chronic CVD and cognitive dysfunction. Alterations in CVR and hemodynamics have been described in patients with both neurodegenerative and vascular cognitive impairment, and the severity of these alterations seems to correlate with CVR derailment. Furthermore, an increased risk of cognitive impairment progression has been associated with alterations in CVR parameters and hemodynamics. Few studies have investigated these associations in acute cerebrovascular disorders and the results are inconsistent; thus, further research on this topic is encouraged.

Comparison of different metrics of cerebral autoregulation in association with major morbidity and mortality after cardiac surgery

BACKGROUND

Cardiac surgery studies have established the clinical relevance of personalised arterial blood pressure management based on cerebral autoregulation. However, variabilities exist in autoregulation evaluation. We compared the association of several cerebral autoregulation metrics, calculated using different methods, with outcomes after cardiac surgery.

METHODS

Autoregulation was measured during cardiac surgery in 240 patients. Mean flow index and cerebral oximetry index were calculated as Pearson's correlations between mean arterial pressure (MAP) and transcranial Doppler blood flow velocity or near-infrared spectroscopy signals. The lower limit of autoregulation and optimal mean arterial pressure were identified using mean flow index and cerebral oximetry index. Regression models were used to examine associations of area under curve and duration of mean arterial pressure below thresholds with stroke, acute kidney injury (AKI), and major morbidity and mortality.

RESULTS

Both mean flow index and cerebral oximetry index identified the cerebral lower limit of autoregulation below which MAP was associated with a higher incidence of AKI and major morbidity and mortality. Based on magnitude and significance of the estimates in adjusted models, the area under curve of MAP < lower limit of autoregulation had the strongest association with AKI and major morbidity and mortality. The odds ratio for area under the curve of MAP < lower limit of autoregulation was 1.05 (95% confidence interval, 1.01-1.09), meaning every 1 mm Hg h increase of area under the curve was associated with an average increase in the odds of AKI by 5%.

CONCLUSIONS

For cardiac surgery patients, area under curve of MAP < lower limit of autoregulation using mean flow index or cerebral oximetry index had the strongest association with AKI and major morbidity and mortality. Trials are necessary to evaluate this target for MAP management.

Transcranial Doppler Ultrasonography as a Diagnostic Tool for Cerebrovascular Disorders

Imaging techniques including transcranial Doppler (TCD), magnetic resonance imaging (MRI), computed tomography (CT), and cerebral angiography are available for cerebrovascular disease diagnosis. TCD is a less expensive, non-invasive, and practically simpler approach to diagnosing cerebrovascular disorders than the others. TCD is a commonly available and inexpensive diagnostic tool. However, owing to its large operator dependency, it has a narrow application area. Cerebrovascular disease indicates a group of disorders that alter the flow of blood in the brain. The brain’s functions can be temporarily or permanently impaired as a result of this change in blood flow. Timely diagnosis and treatment can restore the brain-impaired functions, resulting in a much-improved prognosis for the patients. This review summarizes the basic principles underlying the TCD imaging technique and its utility as a diagnostic tool for cerebrovascular disease.

Transcranial Doppler studies in Type 2 diabetes mellitus: A systematic review

BACKGROUND

Type II Diabetes mellitus (T2DM) patients are at the risk of developing cerebrovascular diseases, often contributed by altered cerebral haemodynamics. We present a systematic review of studies on cerebral haemodynamics assessment using transcranial Doppler (TCD) in T2DM.

REVIEW METHOD

A systematic review of the published articles in the English language between 1991 to 2021.

DATA SOURCES

Articles were retrieved via Pubmed and Cochrane library. We included Cross-sectional, prospective, retrospective, randomized controlled, and cross-over studies for this review.

RESULTS

A total of 25 articles met the inclusion criteria, which provided data for 3212 patients.

CONCLUSION

Cerebral autoregulation is often impaired among patients with T2DM. The risk increased with the duration of T2DM, related complications and presence of comorbidities.

Transcranial Doppler findings in reversible cerebral vasoconstriction syndrome

BACKGROUND AND PURPOSE

Reversible cerebral vasoconstriction syndrome (RCVS) is a syndrome characterized by reversible segmental vasoconstriction of cerebral arteries. Digital subtraction and noninvasive angiograms are typically used to detect vasospasm; however, due to the dynamic nature of RCVS these tests are often negative initially and may need to be repeated multiple times. Transcranial Doppler (TCD) offers many advantages as it is a noninvasive and nonradiating modality. Studies investigating its diagnostic utility for capturing vasospasm and studying temporal evolution of RCVS are limited.

METHODS

We conducted a retrospective analysis on all patients admitted with suspected RCVS from 2009 to 2014 to a single center at Jackson Memorial Hospital.

RESULTS

We identified 9 patients (88.9% women, age 46.6 ± 13.5 years) who met diagnostic criteria for RCVS. All patients presented with headache, 5 developed nonaneurysmal subarachnoid hemorrhage, 5 developed ischemic stroke, and 1 developed posterior reversible encephalopathy syndrome. At initial TCD, 8 patients had increased flow velocities in at least one large intracranial artery and ultimately all patients had abnormal middle cerebral artery flow velocity over the course of RCVS. We found that the number of vessels with abnormal velocities increases gradually and peaks between 13 and 14 days after first symptom onset. Finally, mean flow velocity of affected vessels also increases around the same time frame and normalizes at 60 days.

CONCLUSIONS

In this case series, we found TCD to be useful in detecting vasospasm and monitoring the temporal evolution of RCVS. TCD could be a helpful clinical tool to diagnose and monitor RCVS.

Comparison of transcranial doppler ultrasound indices in large and small vessel disease cerebral infarction

Background: Atherosclerotic involvement of large and small cerebral arteries leading to infarction is among the most prevalent subtypes of stroke worldwide. The hemodynamic changes due to these arterial pathologies can be studied non-invasively and in real-time by using transcranial Doppler (TCD) techniques. TCD indices of the studied arteries may guide the clinician in differentiating these two underlying arterial pathologies. Methods: A cross-sectional study of patients with small and large vessel types of cerebral infraction based on the Trial of ORG 10172 in Acute Stroke Treatment (TOAST) stroke classification was undertaken in the inpatient population of neurology service of Razi Hospital, Tabriz, Iran, from October 2018 to October 2019. After clinical diagnosis, all cases underwent TCD studies, brain magnetic resonance imaging (MRI), and brain and cervical four-vessel magnetic resonance angiography (MRA). The results of TCD indices related to major arteries of the circle of Willis were tabulated and compared between large and small vessel subtypes of cerebral infarction. Results: A statistically significant difference between right middle cerebral artery (MCA) pulsatility index (PI), left MCA PI, right internal carotid artery (ICA) PI, end-diastolic velocity (EDV), left ICA PI, left ICA EDV, left anterior cerebral artery (ACA) PI, and right vertebral artery (VA) PI measures of the two groups was seen (P < 0.05). In comparison to the large vessel group, left ACA, right VA, and bilateral MCAs and ICAs in the small-vessel stroke group demonstrated an elevated PI. Conclusion: A significant increase of PI occurs in the majority of intracranial arteries of patients with small vessel stroke. This makes PI a valuable marker for differentiating strokes with different underlying pathophysiologies.

Errors and Consequences of Inaccurate Estimation of Mean Blood Flow Velocity in Cerebral Arteries

Many transcranial Doppler ultrasonography devices estimate the mean flow velocity (FVm) by using the traditional formula (FVsystolic + 2 × FVdiastolic)/3 instead of a more accurate formula calculating it as the time integral of the current flow velocities divided by the integration period. We retrospectively analyzed flow velocity and intracranial pressure signals containing plateau waves (transient intracranial hypertension), which were collected from 14 patients with a traumatic brain injury. The differences in FVm and its derivative pulsatility index (PI) calculated with the two different methods were determined. We found that during plateau waves, when the intracranial pressure (ICP) rose, the error in FVm and PI increased significantly from the baseline to the plateau (from 4.6 ± 2.4 to 9.8 ± 4.9 cm/s, P < 0.05). Similarly, the error in PI also increased during plateau waves (from 0.11 ± 0.07 to 0.44 ± 0.24, P < 0.005). These effects were most likely due to changes in the pulse waveform during increased ICP, which alter the relationship between systolic, diastolic, and mean flow velocities. If a change in the mean ICP is expected, then calculation of FVm with the traditional formula is not recommended.

Effectiveness of nebulized dexmedetomidine for treatment of post-dural puncture headache in parturients undergoing elective cesarean section under spinal anesthesia: a randomized controlled study

PURPOSE

The need for effective treatment for post-dural puncture headache (PDPH) is a growing research entity. This study aimed to test the effectiveness of additional dexmedetomidine (DEX) to PDPH conservative management and evaluate its cerebral hemodynamic effects trans-cranial Doppler.

METHODS

This prospective randomized double-blind controlled trial was conducted on 43 post-partum females suffering from PDPH with visual analog score (VAS) ≥ 4 and Lybecker score ≥ 2. The study subjects were allocated into control group [n = 22] received nebulization of 4 mL 0.9% saline and DEX group [n = 21] received nebulization of 1 µg/kg DEX diluted in 4 mL 0.9% saline twice daily that was continued until achieving VAS score ≤ 3 and Lybecker score < 2 and/or for a maximum of 72 h. Both groups received routine conservative management. The primary outcome was the VAS and Lybecker scores and the secondary results were the DEX effects on cerebral vessels and the occurrence of any adverse effects.

RESULTS

VAS and Lybecker scores were significantly lower in DEX group. The middle cerebral artery mean flow velocity was significantly lower, and the pulsatility index was considerably higher after DEX nebulization compared to placebo. Two patients in the control group were indicated for epidural blood patch.

CONCLUSION

The addition of DEX nebulization (1 µg/kg twice daily) to the PDPH conservative care effectively relieved the symptoms and lowered pain scores which could be due to its analgesic and cerebral vasoconstrictive effects.

TRIAL REGISTRATION

This study was approved by the research ethical committee of Faculty of Medicine, Zagazig University with the reference number (ZU-IRB#: 6075/26-4-2020) and it was registered under clinicaltrials.gov (NCT04327726).

Outcome predictors of intravenous thrombolytic therapy in acute ischemic stroke patients: an Egyptian center experiences

Background

Intravenous thrombolytic therapy remains the guideline-recommended treatment to improve outcomes after acute ischemic stroke. However, the functional outcome among patients with acute ischemic stroke after receiving intravenous thrombolytic therapy is influenced by huge variety of factors, and this was the aim of our study to evaluate the outcome predictors of intravenous thrombolytic therapy in a sample of Egyptian patients with acute ischemic stroke.

Methods

We enrolled 183 acute ischemic stroke patients who were treated with intravenous recombinant tissue plasminogen activator (IV rtPA) according to the last updated guidelines of American Heart Association and American Stroke Association (AHA/ASA) from February 2018 to February 2020; however, only 150 patients of them completed our study plan till the end. Data of study variables were collected, analyzed statistically and correlated with the functional outcome 3 months after receiving IV rtPA using the modified Rankin Scale (mRS).

Results

Good functional outcome was seen in 98 (65.3%) patients and poor functional outcome was seen in 52 (34.7%) patients. Multivariate analysis of the study variables was done to detect the significant independent predictors of the functional outcome. Atrial fibrillation (AF) (P value < 0.001*OR 6.28* (95% C.I)), hypertension (P value 0.001*OR 3.65*(95% C.I)), diabetes mellitus (DM) (P value 0.009*OR 2.805*(95% C.I)), increased National Institute of Health Stroke Scale (NIHSS) score 24 h after receiving IV rtPA (P value 0.003* OR 8.039* (95% C.I)), increased pulsatility index (PI) value in cerebral vessels at the same side of stroke lesion (P value 0.038* OR 42.48*(95% C.I)) were the significant independent predictors of poor functional outcome. On the other hand decreased NIHSS score 24 h after receiving IV rtPA (P value 0.003* OR 0.124*(95% C.I)), Normal value of PI in cerebral vessels at the same side of stroke lesion (P value 0.038* OR 42.48*(95% C.I)) were the significant independent predictors of good functional outcome.

Conclusion

Intravenous thrombolytic therapy improves the functional outcome of acute ischemic stroke patients. Also, AF, hypertension, DM, NIHSS 24 h after receiving IV rtPA and PI could be used as independent predictors of the functional outcome.

Cerebral vasoreactivity, a surrogate marker of cerebrovascular disease, is not impaired in subjects with lifetime, untreated, congenital isolated GH deficiency

OBJECTIVES

Cerebrovascular disease (CeVD) is a major cause of death and disability. The role of the GH/IGF-I axis on CeVD risk is controversial. Patients with GH deficiency (GHD) in the setting of hypopituitarism often exhibit CeVD predisposing factors, like low nitric oxide generation, endothelial dysfunction, increased visceral fat mass, increased levels of LDL cholesterol, and increased intima-media thickness, a surrogate marker of atherosclerosis. However, several confounders such as the primary hypothalamic-pituitary lesion, hormonal replacement therapies, consequences of surgery and radiotherapy, may influence this relationship. Therefore, we decided to assess cerebral vasoreactivity, a surrogate marker of CeVD, in adult subjects with untreated isolated GHD (IGHD) due to the same homozygous null mutation in the GHRH receptor gene.

METHODS

A cross-sectional study was carried out in 25 adult IGHD subjects and 25 age- and gender-matched controls. Interview, physical examination, laboratory data, intima-media thickness measurement, and transcranial Doppler were performed. The intracranial hemodynamics (mean flow velocity, pulsatility and resistance indexes) were measured, and the response to the vasodilatory stimulus by breath-holding maneuver (breath-holding index) was calculated.

RESULTS

IGHD and control groups were similar in Framingham risk score and intima-media thickness. Similarly, there was no difference in mean flow velocity, pulsatility, resistance, and breath-holding index.

CONCLUSIONS

Lifetime, untreated IGHD does not cause impaired cerebral vasoreactivity.

Role of transcranial Doppler ultrasonography in assessing stenosis after flow diversion

INTRODUCTION

Patients after implantation of flow diverters (FD) due to intracranial aneurysms require radiological and clinical follow-up in view of in-stent stenosis. The aim of the study was to evaluate transcranial Doppler ultrasonography (TCD) as an alternative to more invasive digital subtraction angiography in monitoring patients with FD.

PATIENTS AND METHODS

Twenty-five patients after FD deployment due to internal carotid artery (ICA) aneurysms were reviewed. The degree stenosis found on TCD was compared with the results of catheter angiography. The TCD examinations were recorded from two sides at the extracranial ICA and the most proximal and distal segment of intracranial ICA. Analyzed TCD factors included: peak systolic blood flow velocity, end diastolic velocity, mean velocity, pulsatility index, and resistivity index. The side-to-side differences and ratios between particular TCD indices were calculated.

RESULTS

The cumulative frequency of angiographic in-stent stenosis was 5 of 25 (20 %). The analysis showed that pulsatility index measured on the most proximal intracranial segment of ICA is a predictor for angiographic instent stenosis (AUC = 0.854; p = 0.04; 95 % CI 0.59-1.00). The threshold of pulsatility index separating stenosis and non-stenosis groups was 1.05 with a sensitivity of 50 % and a specificity of 100 %. As the cut-off threshold of PI was set 0.75 the sensitivity and specificity was 100 % and 16.7 %, respectively.

CONCLUSIONS

The increased TCD-derived pulsatility index measured on the most proximal intracranial segment of ICA is associated with in-stent stenosis demonstrated on angiograms.

Risk Factors for Delayed Neurocognitive Recovery According to Brain Biomarkers and Cerebral Blood Flow Velocity

Background and Objectives: The aim of this study is to identify risk factors for the development of delayed neurocognitive recovery (dNCR). Methods: 140 patients underwent neurocognitive evaluations (Adenbrooke, MoCa, trial making, and CAM test) and middle cerebral artery (MCA) blood flow velocity (BFV) measurements, one day before cardiac surgery. BFV was re-evaluated after anesthesia induction, before the beginning, middle, end, and after cardiopulmonary bypass (CPB) and postsurgery. To measure glial fibrillary acidic protein (GFAP) and neurofilament heavy chain (Nf-H), blood samples were collected after anesthesia induction, 24 and 48 h after the surgery. Neurocognitive evaluation was repeated 7-10 days after surgery. According to the results, patients were divided into two groups: with dNCR (dNCR group) and without dNCR (non-dNCR group). Results: 101 patients completed participation in this research. GFAP increased in both the non-dNCR group (p < 0.01) and in the dNCR group (p < 0.01), but there was no difference between the groups (after 24 h, p 0.342; after 48 h, p 0.273). Nf-H increased in both groups (p < 0.01), but there was no difference between them (after 24 h, p = 0.240; after 48 h, p = 0.597). MCA BFV was significantly lower in the dNCR group during the bypass (37.13 cm/s SD 7.70 versus 43.40 cm/s SD 9.56; p = 0.001) and after surgery (40.54 cm/s SD 11.21 versus 47.6 cm/s SD 12.01; p = 0.003). Results of neurocognitive tests correlated with CO₂ concentration (Pearson's r 0.40, p < 0.01), hematocrit (r 0.42, p < 0.01), MCA BFV during bypass (r 0.41, p < 0.01), and age (r -0.533, p < 0.01). The probability of developing dNCR increases 1.21 times with every one year of increased age (p < 0.01). The probability of developing dNCR increases 1.07 times with a decrease of BFV within 1 cm/s during bypass (p = 0.02). Conclusion: Risk factors contributing to dNCR among the tested patients were older age and middle cerebral artery blood flow velocity decrease during bypass.

Toward automated classification of pathological transcranial Doppler waveform morphology via spectral clustering

Cerebral Blood Flow Velocity waveforms acquired via Transcranial Doppler (TCD) can provide evidence for cerebrovascular occlusion and stenosis. Thrombolysis in Brain Ischemia (TIBI) flow grades are widely used for this purpose, but require subjective assessment by expert evaluators to be reliable. In this work we seek to determine whether TCD morphology can be objectively assessed using an unsupervised machine learning approach to waveform categorization. TCD beat waveforms were recorded at multiple depths from the Middle Cerebral Arteries of 106 subjects; 33 with Large Vessel Occlusion (LVO). From each waveform, three morphological features were extracted, quantifying onset of maximal velocity, systolic canopy length, and the number/prominence of peaks/troughs. Spectral clustering identified groups implicit in the resultant three-dimensional feature space, with gap statistic criteria establishing the optimal cluster number. We found that gap statistic disparity was maximized at four clusters, referred to as flow types I, II, III, and IV. Types I and II were primarily composed of control subject waveforms, whereas types III and IV derived mainly from LVO patients. Cluster morphologies for types I and IV aligned clearly with Normal and Blunted TIBI flows, respectively. Types II and III represented commonly observed flow-types not delineated by TIBI, which nonetheless deviate from normal and blunted flows. We conclude that important morphological variability exists beyond that currently quantified by TIBI in populations experiencing or at-risk for acute ischemic stroke, and posit that the observed flow-types provide the foundation for objective methods of real-time automated flow type classification.

Dynamic Estimation of Cerebral Blood Flow Using Blood Pressure Signal in sleep Apnea Patients

Monitoring apnea-induced cerebral blood flow (CBF) oscillations is of importance for assessing apnea patient brain health. Blood pressure (BP) oscillations during apnea can induce oscillations in CBF. Preliminary results of testing an Auto Regressive Moving Average model relating nocturnal CBP oscillations to nocturnal BP variations in 8 obstructive sleep apnea subjects (3 F, 55±8 yrs., BMI 34.2±7.85 kg/m²) showed that largest mean and standard deviation of the CBF estimation errors was 4.49±7.57 cm/s and maximum root mean squared of the errors was 8.80 cm/s. Hence, reasonable accuracy in estimating CBF from BP during sleep apnea events was observed.

A New Transcranial Doppler Scoring System for Evaluating Middle Cerebral Artery Stenosis

BACKGROUND AND PURPOSE

Transcranial Doppler (TCD) criteria for cerebrovascular stenosis are only based on velocity with unsatisfactory positive predictive value (PPV) in previous studies. We refined a published scoring system that integrates several characteristics of TCD data in diagnosing middle cerebral artery (MCA) stenosis.

METHODS

Using the TCD-digital subtraction angiography (DSA) database from Stroke Outcomes and Neuroimaging of Intracranial Atherosclerosis (SONIA) trial, velocity, spectrum pattern, diffuse ratio, and asymmetry ratio were assessed. The cutpoints were defined for each parameter and a point value was assigned to each category within that parameter. A summed score was calculated for each MCA. The accuracy was assessed for different cutpoints in predicting ≥50% MCA stenosis measured by DSA. Logistic regression and C-statistics were used for analysis.

RESULTS

A total of 114 MCAs were included in vessel-based and 87 patients were included in patient-based analysis. Compared to the velocity-only cutpoints in SONIA, the score results in much improved PPV while negative predictive value (NPV) remains unchanged. The score based on mean velocity (score 0: <140 cm/s, score 3: ≥140 cm/s), spectrum pattern (score 0: no turbulence; score 1: mild turbulence; 2: significant turbulence), and asymmetry ratio (score 0: ratio <1.5, score 1: ratio 1.5-2; score 2: ratio ≥2.1) has the highest NPV while PPV remains favorable (PPV: 72% [95% CI 54-90%]; NPV: 84% [95% CI: 75-93%], area under curve [AUC]: .76 [95% CI: .66-.86]).

CONCLUSIONS

The multiparameter scoring system incorporating several characteristics of TCD measures yielded higher PPV while maintaining high NPV compared with the single-parameter velocity criteria in diagnosing MCA ≥50% stenosis.

The Role of Transcranial Doppler Ultrasonography in the Diagnosis of Brain Death

Ancillary tests can be used for the diagnosis of brain death in cases wherein uncertainty exists regarding the neurological examination and apnoea test cannot be performed. Transcranial Doppler ultrasonography (TCD) is a useful, valid, non-invasive, portable, and repeatable ancillary test for the confirmation of brain death. Despite its varying sensitivity and specificity rates with regard to the diagnosis of the brain death, its clinical use has steadily increased in the intensive care unit because of its numerous superior properties. The use of TCD as an ancillary test for the diagnosis of brain death and cerebral circulatory arrest is discussed in the current review.

Effects of Alternating Standing and Sitting Compared to Prolonged Sitting on Cerebrovascular Hemodynamics

PURPOSE

Previous research suggests that prolonged sitting may acutely reduce cerebral blood flow velocity (CBFv). The purpose of this study was to evaluate the effects of alternating standing and sitting vs prolonged sitting on CBFv.

METHODS

This randomized crossover study enrolled working adults (N=25) with pre-to-stage 1 hypertension not using antihypertensive medications, and a body mass index from 25 to < 40 kg/m2. Subjects participated in two simulated workday conditions: 1) sitting continuously (SIT), and 2) alternating standing and sitting every 30 min (SS). Beat-to-beat systolic, mean and diastolic CBFv were recorded bilaterally for 1 min via insonation of the middle cerebral artery using transcranial Doppler ultrasonography before (morning), between (midday) and following (afternoon) two 3-hr 40 min work periods.

RESULTS

Mean±SD age was 42±12 years, blood pressure (BP) was 132±9/83±8 mmHg, and BMI was 32±5 kg/m2. Cerebrovascular hemodynamics did not differ across condition (P>0.05). There were, however, significant nonlinear effects of time (decrease from morning to midday; increase from midday to afternoon) on systolic CBFv (P=0.014), mean CBFv (P=0.001), diastolic CBFv (P=0.002), and pulsatility index (P=0.038). When overall time effects were evaluated during each time interval, mean and diastolic CBFv significantly decreased morning to midday and all CBFv increased from midday to afternoon. When separated by condition, significant time effects were observed for all CBFv during SIT (P<0.02) but not SS (P>0.05).

CONCLUSIONS

In individuals with elevated BP and BMI, CBFv significantly decreased by midday and increased by afternoon, especially during a workday of prolonged sitting. Future studies should evaluate the combination of frequent walks and a sit-stand desk to break up prolonged sitting.

Transcranial Doppler role in prediction of post-dural puncture headache in parturients undergoing elective cesarean section: prospective observational study

PURPOSE

Post-dural puncture headache (PDPH) may be resulted from significant changes in cerebral blood flow, which could be visualized by Transcranial Doppler (TCD). This study was performed to investigate if TCD can be used to predict the occurrence of PDPH in high-risk patients.

METHODS

This prospective observational study was conducted on ninety ASA I and II pregnant females undergoing elective cesarean section (CS) under spinal anesthesia. TCD was performed to all patients within 24 h before the operation, at 24 h and 48 h in the post-operative period to measure mean velocity (MV) and Gosling pulsatility index (PI) in the right middle cerebral artery. For 5 days postoperatively, all patients were assessed and the PDPH patients were identified, their pre- and post-puncture TCD measurements were compared with the corresponding measurements of PDPH-free patients and ROC analysis was done to evaluate the predictive value of TCD parameters.

RESULTS

17 patients (18.8%) developed PDPH. PDPH group was significantly higher regarding MV and significantly lower with regard to PI at all times except for the pre-spinal PI. The MV values in all patients showed statistical significant increase within the first 48 h after CS as compared with those before delivery. In PDPH group there was high statistical significant decrease in PI values at 24 h and 48 h compared to the pre-puncture values. The pre-puncture MV was the parameter of the best accuracy for predicting PDPH with a cutoff of MV > 68.4 cm/s and the post-puncture PI at 24 h was the best predictive of PDPH with a cutoff value of < 0.75.

CONCLUSION

TCD might prove a useful tool in predicting PDPH suggesting that higher pre-puncture MV with a cutoff value > 68.4 cm/s and post-puncture lower PI at 24 h with a cutoff < 0.75 are the best predictive parameters.

TRIAL REGISTRATION

This clinical trial was registered with ClinicalTrials.gov (NCT03464253).

Incorporation of Transcranial Doppler into the ED for the neurocritical care patient

INTRODUCTION

In the catastrophic neurologic emergency, a complete neurological exam is not always possible or feasible given the time-sensitive nature of the underlying disease process, or if emergent airway management is indicated. As the neurologic exam may be limited in some patients, the emergency physician is reliant on the assessment of brainstem structures to determine neurological function. Physicians thus routinely depend on advanced imaging modalities to further investigate for potential catastrophic diagnoses. Acquiring these tests introduces the risks of transport as well as delays in managing time-sensitive neurologic processes. A more immediate, non-invasive bedside approach complementing these modalities has evolved: Transcranial Doppler (TCD).

OBJECTIVE

This narrative review will provide a description of scenarios in which TCD may be applicable. It will summarize the sonographic findings and associated underlying pathophysiology in such neurocritical care patients. An illustrated tutorial, along with pearls and pitfalls, is provided.

DISCUSSION

Although there are numerous formalized TCD protocols utilizing four views (transtemporal, submandibular, suboccipital, and transorbital), point-of-care TCD is best accomplished through the transtemporal window. The core applications include the evaluation of midline shift, vasospasm after subarachnoid hemorrhage, acute ischemic stroke, and elevated intracranial pressure. An illustrative tutorial is provided.

CONCLUSIONS

With the wide dissemination of bedside ultrasound within the emergency department, there is a unique opportunity for the emergency physician to utilize TCD for a variety of conditions. While barriers to training exist, emergency physician performance of limited point-of-care TCD is feasible and may provide rapid and reliable clinical information with high temporal resolution.

Correlating transcranial arterial Doppler velocities with haematologic parameters and haemolytic indices of Nigerian children with sickle cell anaemia

Introduction

Cerebral vasculopathy, elevated transcranial Doppler velocities and stroke are linked to excessive intravascular haemolysis in sickle cell anaemia. This study determined the prevalence and pattern of abnormal blood flow velocities in children with sickle cell anaemia from Northern Nigeria using transcranial Doppler and to correlate transcranial Doppler velocities with haematological and biochemical markers of haemolysis.

Methods

Full blood count, reticulocyte count, fetal haemoglobin and some selected biochemical markers of haemolysis of 100 children with sickle cell anaemia were determined at steady state. The time-averaged mean of maximal velocities in four major intracranial blood vessels was measured using non-imaging transcranial Doppler, which were then classified according to the stroke prevention in sickle cell disease trial protocol. A simple linear correlation between time-averaged mean of maximal velocities in the four major intracranial vessels as the dependent variable and haematological and biochemical markers of haemolysis as independent variables was also determined at the significance level of 0.05.

Results

Abnormal transcranial Doppler velocities, classified as high risk, were found in 3% of the studied patients; 11% had intermediate risk while 84% had standard risk. Most high velocities were detected in the middle cerebral artery. The time-averaged mean of maximal velocities of middle cerebral artery positively correlated with total white blood cell count, absolute neutrophil count, platelet count, reticulocyte count, serum lactate dehydrogenase and total bilirubin, while it was negatively correlated with haematocrit and fetal haemoglobin levels.

Conclusion

Our study showed low prevalence of abnormal transcranial Doppler velocities and low prevalence is unrelated to low markers of haemolysis in our study population.

Evaluation of Cerebral Blood Flow Alterations and Acute Neuronal Damage due to Water-Pipe Smoking

Background:

Although water-pipe smoking is a great public health problem, data regarding the acute and chronic effects and the degree of toxin exposure are limited. While water pipe-related malignancy, pulmonary, infectious, cardiac effects, infertility, and biological effects have been described in a meta-analysis, there are no studies in the literature about its neurologic effects.

Aims:

To evaluate water pipe-related acute neurological effects and cerebral blood flow through transcranial Doppler ultrasonography and serum S100 calcium binding protein calcium binding protein level measurements.

Study Design:

Prospective observational study.

Methods:

Vital signs and baseline carboxyhemoglobin and S100 calcium binding protein levels, cerebral flood changes with transcranial Doppler ultrasound were evaluated and recorded before and after water-pipe smoking.

Results:

The mean age of the 31 volunteers was 30.61 (±5.67) years, and 24 of them (77.42%) were male. A statistically significant difference was determined in heart rate, oxygen saturation, systolic and diastolic arterial pressure values before and after water-pipe smoking (p<0.001, p=0.035, p=0.009, p=0.021, respectively). Mean carboxyhemoglobin level was 2.68% (±1.68) before, 14.97% (±4.83) after water-pipe smoking (p<0.001). The S100 calcium binding protein level was 25.05 μ/mL (±8.34) at the beginning, 40.71 μ/mL (±14.06) after water-pipe smoking (p<0.001). An increase was determined in peak, and median middle, anterior and posterior cerebral artery blood flow rates, and a decrease was determined in both the pulsatility index and resistivity index values after water-pipe smoking using transcranial Doppler ultrasound.

Conclusion:

Cerebral vasodilation develops due to the increase in cerebral blood flow rate and the decrease in pulsatility index, resistivity index values, and the elevation in carboxyhemoglobin, S100 calcium binding protein level indicates that water-pipe smoking leads to neuronal damage in the acute period.

Alterations in transcranial Doppler indices of pregnant women with complicated preeclampsia

OBJECTIVES

We aimed to investigate alterations in transcranial Doppler indices (TCD) of the cerebral arteries between normotensive and preeclampsia (PE) pregnancies according to the presence of cerebral symptoms.

STUDY DESIGN

This cross-sectional study included 48 PE and 20 normotensive pregnancies, respectively. Doppler indices of the anterior, middle, and posterior cerebral arteries (ACA, MCA, and PCA, respectively) were compared between the PE and normotensive group.

MAIN OUTCOME MEASURES

Mean cerebral velocity (MCV), pulsatility index (PI), and resistance index (RI) were calculated using cerebral velocities. The cerebral perfusion pressure (CPP), resistance area product (RAP), and cerebral flow index (CFI) were computed using velocity and blood pressure. The PE group was subdivided according to the presence of cerebral symptoms and the TCD indices were compared between these groups.

RESULTS

MCV and CFI of the PCA as well as CPP and RAP of all arteries were significantly higher, while PI and RI were significantly lower in PE group (P < 0.05). PI of the MCA had the highest sensitivity (91.7%), while PI of the PCA and RAP of the MCA had the highest specificity (95.0% each) for predicting PE-related cerebral complications. The positive likelihood ratio was highest in PI of the PCA (14.58). Among these parameters, CPP and RAP of the PCA were higher in PE patients showing cerebral symptoms than in those without symptoms.

CONCLUSIONS

These results suggest that pregnant women with PE had altered TCD indices and that prominent changes, thereof, especially in the PCA, contribute to the development of cerebral symptoms.

Monitoring cerebral vasospasm: How much can we rely on transcranial Doppler

Cerebral vasospasm leading to delayed cerebral ischaemia is one of the major concerns following subarachnoid haemorrhage (SAH). Various modalities are present for evaluation and detection of cerebral vasospasm that occurs following SAH. They include transcranial Doppler (TCD), computed tomographic angiography (CTA), computed tomographic (CT) perfusion and digital subtraction angiography (DSA). The recent guidelines have advocated the use of TCD and have described it as a reasonable technique for monitoring the development of vasospasm. This review describes the functioning of TCD, the cerebral haemodynamic changes during vasospasm and TCD-based detection of vasospasm. The review shall highlight as to how the TCD derived values are relevant in the settings of neurocritical care. The data in the review have been consolidated based on our search of literature from year 1981 till 2016 using various data base.

Are the Variants of the Circle of Willis Determined by Genetic or Environmental Factors? Results of a Twin Study and Review of the Literature

BACKGROUND

Anatomic variants of the circle of Willis (CW) are commonly observed in healthy subjects. Genetic and environmental factors influencing these variants remain unclear. Our aim was to assess the genetic and environmental background affecting variant CW phenotypes.

METHODS

A total of 122 adult healthy twins from the Hungarian Twin Registry (39 monozygotic (MZ) and 22 dizygotic (DZ) pairs, average age 49.7 ± 13.4 years) underwent Time-of-Flight magnetic resonance angiography and transcranial Doppler sonography. We investigated the anterior and posterior CW according to morphological categories. Prevalence and concordance rates of CW variants were calculated. MZ twins discordant for CW variants were analyzed for cardiovascular risk factors and altered blood flow.

RESULTS

Complete CW (45.0%) and bilaterally absent posterior communicating artery (PCoA) (22.5%) were the most prevalent variants in the anterior and posterior CW, respectively. There was no significant difference regarding the prevalence of variants across zygosity except for bilaterally hypoplastic PCoA (p = .02). DZ concordance was higher compared to MZ twins regarding morphological categories of the CW. Cardiovascular risk factors were not significantly associated with variant CW in MZ twins discordant to CW morphology. Flow parameters did not differ significantly among MZ twins discordant to CW variants.

CONCLUSION

CW variants may not be determined by substantial genetic effects and are not influenced by altered blood flow in healthy individuals. Further investigations are needed to identify potential environmental factors affecting these variants.

Regression-based noninvasive estimation of intracranial pressure

Monitoring of intracranial pressure (ICP) is indicated in patients with a variety of conditions affecting the brain and cerebrospinal fluid space. The measurement of ICP, however, is highly invasive as it requires placement of a catheter in the brain tissue or cerebral ventricular spaces. Several noninvasive techniques have been proposed to overcome this issue, and one class of approaches is based on analyzing cerebral blood flow velocity (CBFV) and arterial blood pressure (ABP) waveforms to infer ICP. Here, we analyze a physiologic model linking ICP to CBFV and ABP and present a regression-based approach to estimating ICP. We tested the model on 20 datasets recorded from three patients in intensive care. Our estimates achieve a mean error (bias) of -1.12 mmHg and a standard deviation of the error of 5.56 mmHg, for a root-mean-square error of 5.68 mmHg, when compared against the invasive ICP measurement. Since transcranial Doppler ultrasound based CBFV measurements depend on the Doppler angle φ between the direction of the ultrasound beam and the (main) direction of blood flow velocity, we investigated the robustness of our ICP estimates against variations in φ. Our results show a change in the estimated ICP that is <;1 mmHg if we assume φ ~ N(μ; σ²), with μ = 0 and σ = 10°.

Impaired Cerebral Haemodynamics in Vascular Depression: Insights From Transcranial Doppler Ultrasonography

Introduction: Late-life depression is a well-known risk factor for future dementia. Increasing evidences also show a link between cerebral hypoperfusion and neurodegeneration, although data on Transcranial Doppler ultrasonography (TCD)-derived measures in patients with "Vascular Depression" (VD) are lacking. The aim of this study was to assess and correlate TCD parameters with cognitive function and severity of subcortical ischemic vascular disease in a sample of VD patients. Methods: Seventy six patients (mean age 72.5 ± 5.3 years; 53.9% females) met the DSM-5 diagnostic criteria for unipolar major depression. Mean blood flow velocity (MBFv) and pulsatility index (PI) were recorded from the middle cerebral artery. Quantification of depressive symptoms (17-item Hamilton Depression Rating Scale -HDRS), neuropsychological test evaluating frontal lobe abilities (Stroop Color-Word test interference-Stroop T), and white matter lesions (WMLs) load according to the Fazekas visual score were also assessed. Results: WMLs severity was mild in 20 patients (group I), moderate in 32 (group II), and severe in 24 (group III). The groups were comparable in terms of clinical features, vascular risk factors profile, and HDRS score, whereas Stroop T score was worse in group III. An increased PI and a reduced MBFv were found in VD patients with severe WMLs. According to the regression analysis, a reduced MBFv was independently and significantly associated with depressive symptoms and executive dysfunction, even after adjusting for demographic features and vascular risk factors. Similarly, an independent and significant association was observed between the increase of PI and both Stroop T and WMLs severity. Conclusions: A TCD profile of low perfusion and high vascular resistance in VD patients suggests a diffuse cerebrovascular pathology likely arising from the small vessels and then extending to larger arteries. Hemodynamic dysfunction might play a pathogenic role in the development of cognitive impairment in patients with late-life depression and subcortical ischemic vascular disease. TCD represents a valuable tool in the early detection, assessment, and management of VD patients at risk for dementia.

Location of the internal carotid artery and ophthalmic artery segments for non-invasive intracranial pressure measurement by multi-depth TCD

The aim of the present study was to locate the ophthalmic artery by using the edge of the internal carotid artery (ICA) as the reference depth to perform a reliable non-invasive intracranial pressure measurement via a multi-depth transcranial Doppler device and to then determine the positions and angles of an ultrasonic transducer (UT) on the closed eyelid in the case of located segments. High tension glaucoma (HTG) patients and healthy volunteers (HVs) undergoing non-invasive intracranial pressure measurement were selected for this prospective study. The depth of the edge of the ICA was identified, followed by a selection of the depths of the IOA and EOA segments. The positions and angles of the UT on the closed eyelid were measured. The mean depth of the identified ICA edge for HTG patients was 64.3 mm and was 63.0 mm for HVs (p = 0.21). The mean depth of the selected IOA segment for HTG patients was 59.2 mm and 59.3 mm for HVs (p = 0.91). The mean depth of the selected EOA segment for HTG patients was 48.5 mm and 49.8 mm for HVs (p = 0.14). The difference in the located depths of the segments between groups was not statistically significant. The results showed a significant difference in the measured UT angles in the case of the identified edge of the ICA and selected ophthalmic artery segments (p = 0.0002). We demonstrated that locating the IOA and EOA segments can be achieved using the edge of the ICA as a reference point.

Abbreviations: OA: ophthalmic artery; IOA: intracranial segments of the ophthalmic artery; EOA: extracranial segments of the ophthalmic artery; ICA: internal carotid artery; UT: ultrasonic transducer; HTG: high tension glaucoma; SD: standard deviation; ICP: intracranial pressure; TCD: transcranial Doppler

Investigation of circle of Willis variants and hemodynamic parameters in twins using transcranial color-coded Doppler sonography

Morphological and hemodynamic variations of the circle of Willis (CW) may have an important impact on cerebrovascular events. However, the environmental and genetic influence remains unclear. For this reason we studied the variations and hemodynamic parameters of the CW in twins using transcranial color-coded sonography (TCCS). Sixty-four twins, 19 monozygotic (MZ) and 13 dizygotic (DZ) pairs from the Italian Twin Registry (average age 45.0 ± 13.7 years) underwent TCCS and risk factor assessment. We examined CW morphology and recorded peak systolic velocity (PSV), end-diastolic velocity (EDV) and pulsatility index (PI). Raw heritability was determined for hemodynamic parameters, whereas concordance and discordance rates were calculated for CW morphological variants. A normal CW anatomy was observed in the majority of MZ and DZ twins (76.5% and 92.3%, respectively). The most frequent variant was a missing anterior cerebral artery (ACA). There was no significant difference in the prevalence of most CW variants depending on the zigosity. Concordance rates were low regarding the presence of variant CW anatomy both in MZ and DZ groups (0.14 and 0.00, respectively). Women had a significantly higher PI in vertebral arteries (VA) and in the right ACA (p = 0.01, p = 0.02 and p < 0.01, respectively). An inverse correlation was observed between hemodynamic parameters and age. Morphological variants of the CW do not seem to be heritable; they are most likely determined by environmental factors. In contrast, hemodynamic parameters of the CW are moderately heritable and this might have implications in the management and prevention of cerebrovascular diseases.

Transcranial Doppler of the middle cerebral artery indicates regional gray matter cerebral perfusion

OBJECTIVE

We determined if transcranial color-coded Doppler derived hemodynamics are associated with MRI-based cerebral blood flow (CBF) in regions clinically important to dementia in healthy middle-aged adults.

APPROACH

In 30 subjects (18m/12f; age  =  52  ±  1 years), blood flow velocity (BFV) and cerebrovascular conductance (CVC) were measured with transcranial color-coded Doppler (TCCD) at the middle cerebral artery (MCA) and cerebral blood flow (CBF) was assessed with arterial spin labeled perfusion MRI.

MAIN RESULTS

BFV and CVC were associated with hippocampus (r  =  0.58 and r  =  0.61, both p  <  0.01) and occipitoparietal (r  =  0.50 and r  =  0.58, both p  <  0.01) CBF. CVC was further associated with posterior cingulate CBF (r  =  0.58 p  <  0.01). Independent of age and sex, BFV and CVC were associated with hippocampus (r  =  0.59 and r  =  0.55, both p  <  0.003) and occipitoparietal (r  =  0.50 and r  =  0.57, both p  <  0.01) CBF. CVC was independently associated with posterior cingulate CBF (r  =  0.38, p  =  0.049).

SIGNIFICANCE

TCCD-measured BFV and CVC of the MCA are indicators of cerebral perfusion to clinically valuable brain regions in healthy middle-aged adults. TCCD may not be a good indicator of blood flow to cerebral white matter.

Assessment of maternal cerebral blood flow velocity by transcranial Doppler ultrasound before delivery and in the early postpartum period

OBJECTIVE

This prospective observational study aimed to identify the effects of labor on cerebral hemodynamics by measuring the middle cerebral artery (MCA) blood flow velocity by transcranial Doppler ultrasound (TCD), and the related factors just before delivery and within the 24 h after delivery.

METHODS

The study included 35 healthy pregnant women with a gestational age of >37 weeks who were in labor and a control group including healthy, age-matched, nonpregnant women (n = 24). Demographic characteristics and significant clinical information of pregnant women were recorded. The MCA blood flow velocity was assessed by TCD just before and within 24 h after delivery. The parameters assessed by TCD were mean cerebral blood flow velocity (MCBFV), peak systolic velocity (PSV), pulsatility index (PI), resistance index (RI), and systolic/diastolic ratio.

RESULTS

There was no significant difference between the pregnant and nonpregnant women regarding age (27 ± 5 years versus 28 ± 7 years; p = .751). The MCBFV, PSV, PI, and RI showed a significant increase within the 24 h after delivery as compared with those before delivery. Comparison of the pregnant women with the control group in terms of the values of all parameters related to the MCA blood flow velocity revealed that the values that were significantly low before delivery reached to the level of the control group after delivery Conclusion: The findings of this study demonstrated that the blood flow velocity of the MCA decreased during the late pregnancy period and increased in the early postpartum period to the level similar to that of the nonpregnant group.

Transcranial Doppler Ultrasound Use in Pediatric Traumatic Brain Injury

Transcranial Doppler ultrasound (TCD) is an inexpensive portable diagnostic tool commonly available within most healthcare systems. A team of trained individuals perform and interpret the test to inform patient care management. The benefit of TCD is well established in adult patients with traumatic brain injury. However, in children with TBI, it is still considered exploratory and its use is not a part of the standard of care. This article describes what TCD is, its use in children, and how TCD measurements apply to children and adolescents in an effort to establish criteria for the use of TCD for children with TBI. The benefit of TCD in pediatric TBI is illustrated by 2 cases of children who participated in a TBI research study. Early indications are that the use of TCD in pediatric cases of TBI may produce unexpected real-time data about the cerebral vasculature and circulation characteristics in children with TBI. Transcranial Doppler ultrasound has the potential for playing an informative diagnostic role in future pediatric TBI management. Ultimately the goal to promote best outcomes after a TBI requires insights into the multi-dynamic nature of the injury and TCD has the ability to support these efforts.