Quantitative collateral assessment evaluated by cerebral blood volume measured by CT perfusion in patients with acute ischemic stroke.

OBJECTIVES: Collateral status (CS) is considered a predictor of clinical outcome after reperfusion therapy (RT) in patients with acute ischemic stroke (AIS). We proposed a quantitative assessment of CS using cerebral blood volume (CBV) measured by computed tomography perfusion (CTP) imaging. MATERIALS AND METHODS: This retrospective study was approved by the Institutional Review Board. Between February 2019 and September 2020, 60 patients with anterior circulation large-vessel occlusion who presented to our institution within 8 h after stroke onset were included. The ratio of the average CBV values in the affected middle cerebral artery (MCA) territories to the unaffected side was defined as the CBV ratio. CS was assessed by scores from previously reported qualitative scoring systems (Tan & regional leptomeningeal collateral (rLMC) scores). RESULTS: The CBV ratio was an independent factor contributing to a good functional outcome (P<0.01) and was significantly correlated with the Tan score (ρ=0.73, P<0.01) and the rLMC score (ρ=0.77, P<0.01). Among the patients with recanalization, the CBV ratio was a useful parameter that predicted both a good functional outcome (area under the receiver operating characteristic curve (AUC-ROC), 0.76; 95% CI, 0.55-0.89) and a good radiological outcome (AUC-ROC, 0.90; 95% CI, 0.72-0.97), and it was an independent predictor for good radiological outcome (OR: 4.38; 95% CI:1.29-14.82; P<0.01) in multivariate models. CONCLUSIONS: The CBV ratio is a suitable parameter for evaluating CS quantitatively for patients with AIS that can predict patient response to recanalization.

Comparison of methods between CT perfusion source images and CT angiography in collateral flow assessment.

BACKGROUND: The methods used for grading leptomeningeal collateral flow (LMF) on single-phase computed tomography angiography (CTA) are heterogeneous and limited by temporal resolution. PURPOSE: To compare the reliability of relative filling time delay (rFTD) on CT perfusion source images (CTP-SI) and the currently used single-phase CTA collateral assessment methods and evaluate their ability to predict clinical outcomes in acute ischemic stroke patients. MATERIAL AND METHODS: We analyzed consecutive middle cerebral artery or internal carotid artery occlusion patients who received multimodal CT before treatment and within 12 h of stroke symptom onset from October 2015 to December 2018. Patients were dichotomized using the 90-day mRS into good (0-1) versus adverse (2-6) outcomes. CTP-SI was used to identify the rFTD score. CTA images were reconstructed to assess collateral status using the collateral score (Cs) and region leptomeningeal collateral score (rLMCs). Two observers independently assessed images. RESULTS: The baseline characteristics (n = 54) were median age of 67 years and 68.5% of the participants were men. The baseline median NIHSS was 14. Good clinical outcomes were observed in 19 (35.2%) patients. The k value was higher for rFTDs (k = 0.779, P < 0.001) than Cs (k = 0.666, P < 0.001) and rLMCs (k = 0.763, P < 0.001). Higher rFTDs were correlated with lower rLMCs (Spearman's rho -0.68, P < 0.001) and Cs (rho -0.66, P < 0.001). In multivariate logistic regression, rFTD was associated with functional outcomes (P = 0.044). CONCLUSION: The rFTDs method is comparable to single-phase CTA-based assessments in assessing LMFs in acute ischemic stroke patients. Higher rFTDs is independently associated with adverse long-term functional outcomes.

Assessment of Atherosclerosis in Peripheral and Central Circulation in Adult ß Thalassemia Intermedia Patients by Color Doppler Ultrasound: Egyptian Experience.

BACKGROUND: Atherosclerosis has been extensively studied in thalassemia major (TM) and sickle cell disease but not yet in ß thalassemia intermedia (TI). Previous studies concerned with TM were performed in children. TI patients usually live longer and, thus, are more prone to complications of atherosclerosis. AIM: In our study, we applied color Doppler for the determination of arterial conduit and flow velocities in ß TI patients. METHODS: For central circulation, we measured right and left middle cerebral arteries (MCAs) and basilar artery (BA) mean flow velocity (MFV), pulsatility index (PI), and peak systolic velocity (PSV) as well as carotid intimal media thickness, and to assess peripheral circulation, we studied ankle/brachial index and posterior and anterior tibial arteries' (ATA, PTA) pressure and PSV. This was applied for 30 adult TI patients and 20 age-, sex-, and ethnic group-matched controls. RESULTS: Transcranial Doppler findings among cases and controls showed that the MFV, PSV of MCAs, and PSV, PI, and MFV of the BA were statistically higher in cases than controls. A comparison between splenectomized and nonsplenectomized patients showed that total leukocyte count, platelet count, lactate dehydrogenase, ferritin, PSV and MFV of the left MCA were all statistically higher in splenectomized cases. Differences between males and females with TI with respect to laboratory and Doppler findings were all statistically insignificant except for intima media thickness, PTA pressure, ATA pressure, and PSV. CONCLUSION: More than one parameter should be applied to assess atherosclerosis in TI. There is evidence of an increased risk of central ischemia rather than peripheral ischemia in these patients.

Assessment of Collateral Circulation Using Perfusion CT in Middle Cerebral Artery Thrombectomy-Treated Patients.

INTRODUCTION: The prognostic value of leptomeningeal collateral circulation in thrombectomy-treated patients remains unclear. We evaluated the construct validity of assessing leptomeningeal collateral circulation using a new regional perfusion CT source image-based approach, the Perfusion Acquisition for THrombectomy Scale (PATHS). We also compared the prognostic value of PATHS with a further 6 scales based on various techniques: CT-angiography, perfusion CT, and digital subtraction angiography. Additionally, we studied the relationship between the scores for the different scales. PATIENTS AND METHODS: We performed a retrospective study of consecutive patients with stroke and M1/terminal carotid occlusion treated with thrombectomy in our center. Leptomeningeal collateral circulation was prospectively evaluated using 7 scales: Tan and Miteff (CT Angiography); Calleja, Cao, American Society of Intervention and Therapeutic Neuroradiology/Society of Interventional Radiology, and PATHS (perfusion); and Christoforidis (Digital Subtraction Angiography). Correlations were studied using the Spearman method. RESULTS: The study population comprised 108 patients. All scales predicted the modified Rankin Scale at 3 months (P ≤ .02) and all but 1 (Christoforidis) correlated with 24-hour brain infarct volume (P ≤ .02). These correlations were higher with PATHS (rho = -0.47, P < .001 for 3-month modified Rankin Scale; rho = -0.35, P < .001 for follow-up infarct volume). The multivariate analysis showed PATHS to be an independent predictor of modified Rankin Scale at 3 months less than equal to 2. A crosscorrelation analysis revealed a better correlation between scales that used the same techniques. CONCLUSIONS: PATHS can be used to assess leptomeningeal collateral circulation. PATHS had better prognostic value than other scales; therefore, it might be considered for assessment of leptomeningeal collateral circulation in candidates for thrombectomy. The moderate correlation between scales suggests that scores are not interchangeable.

Assessment of dynamic cerebral autoregulation in humans: Is reproducibility dependent on blood pressure variability?

We tested the influence of blood pressure variability on the reproducibility of dynamic cerebral autoregulation (DCA) estimates. Data were analyzed from the 2nd CARNet bootstrap initiative, where mean arterial blood pressure (MABP), cerebral blood flow velocity (CBFV) and end tidal CO2 were measured twice in 75 healthy subjects. DCA was analyzed by 14 different centers with a variety of different analysis methods. Intraclass Correlation (ICC) values increased significantly when subjects with low power spectral density MABP (PSD-MABP) values were removed from the analysis for all gain, phase and autoregulation index (ARI) parameters. Gain in the low frequency band (LF) had the highest ICC, followed by phase LF and gain in the very low frequency band. No significant differences were found between analysis methods for gain parameters, but for phase and ARI parameters, significant differences between the analysis methods were found. Alternatively, the Spearman-Brown prediction formula indicated that prolongation of the measurement duration up to 35 minutes may be needed to achieve good reproducibility for some DCA parameters. We conclude that poor DCA reproducibility (ICC<0.4) can improve to good (ICC > 0.6) values when cases with low PSD-MABP are removed, and probably also when measurement duration is increased.

Neurovascular Dysfunction in Alzheimer Disease: Assessment of Cerebral Vasoreactivity by Ultrasound Techniques and Evaluation of Circulating Progenitor Cells and Inflammatory Markers.

AIMS: The aims of this study were to assess vascular dysfunction in patients with Alzheimer disease (AD) by investigating cerebral vasomotor reactivity using transcranial Doppler ultrasound (TCD) and to evaluate any correlations between cerebral vasoreactivity and endothelium dysfunction. Moreover, the frequency of circulating progenitor cells (CPCs) and the blood concentration of vascular/inflammatory markers were evaluated. MATERIALS AND METHODS: We recruited 35 AD subjects and 17 age-matched, sex-matched, and education-matched healthy control subjects. Cerebral vasomotor reactivity was assessed by means of the TCD-based breath-holding index test (BHI). The level of CPCs was evaluated by means of flow cytometry from venous blood samples, while blood vascular/inflammatory markers were measured by means of enzyme-linked immunosorbent assay. RESULTS: Both cerebral assay blood flow velocity in the middle cerebral artery (MCAFV) and BHI values were significantly lower in AD subjects than in healthy controls (P<0.05). A positive trend was found between MCAFV and BHI values and Mini-Mental State Evaluation (MMSE) scores. Moreover, the hematopoietic progenitor cells' count was found to be lower in patients with AD than in controls (P<0.05). Finally, a significantly higher expression of the plasma chemokine CCL-2 was observed in AD patients than in healthy controls. CONCLUSIONS: Our results confirm that cerebral hemodynamic deterioration may be a critical marker of cognitive decline. Further studies are needed to investigate the role of circulating CPCs and chemokines as potential contributors to neurovascular dysfunction.

Prognostic value of the aortic isthmus Doppler assessment on late onset fetal growth restriction.

Background As conflicting results have been reported about the association of reversed flow on the aortic isthmus (AoI) and adverse perinatal results in fetal growth restriction (FGR), we aim to compare perinatal outcomes (including tolerance to labor induction) of late-onset FGR between those with anterograde and reversed AoI flow. Methods This was an observational retrospective cohort study on 148 singleton gestations diagnosed with late-onset FGR (diagnosis ≥32+0 weeks), with an estimated fetal weight (EFW) <10th centile and mild fetal Doppler alteration: umbilical artery (UA) pulsatility index (PI) >95th centile, middle cerebral artery (MCA)-PI <5th centile or cerebral-placental ratio <5th centile. Anterograde AoI flow was present in n=79 and reversed AoI flow in n=69. Delivery was recommended from 37 weeks in both groups. Perinatal results were compared between the groups. Results The global percentage of vaginal delivery of fetuses with anterograde and reversed blood flow was 55.7% vs. 66.7% (P=0.18) and the percentage of cesarean section (C-section) for non-reassuring fetal status was 12.7% vs. 15.9% (P=0.29), respectively. When evaluating those that underwent labor induction, the vaginal delivery rate was 67.9% vs. 77.2% (P=0.17), respectively. There were no significant differences regarding any other perinatal variables and there were no cases of severe morbidity or mortality. Conclusion We observed that the presence of reversed AoI flow does not worsen perinatal outcomes on fetuses with late-onset growth restriction with mild Doppler alterations. Attempt of labor induction is feasible in these fetuses regardless of the direction of AoI flow.

Doppler ultrasonographic assessment of fetal middle cerebral artery peak systolic velocity in gestational diabetes mellitus.

OBJECTIVE: To compare Doppler ultrasonographic measurements of the fetal middle cerebral artery peak systolic velocity (MCA PSV) among women with or without gestational diabetes mellitus (GDM). METHODS: A cross-sectional study was conducted among pregnant women who presented for prenatal care at a single hospital in Brazil between September 11, 2015, and January 6, 2017. Patients were stratified into a group with GDM and a control group without GDM. One Doppler ultrasonographic assessment was performed per participant. This measurement was made after diagnosis but before the start of treatment among women in the GDM group. Fetal ultrasonographic and biometric variables assessed included MCA PSV, MCA pulsatility index, umbilical artery pulsatility index, the MCA-to-umbilical artery ratio, abdominal circumference, and weight. RESULTS: The study included 238 women: 115 in the GDM group and 123 in the control group. The median MCA PSV was 1.02 in the GDM group and 1.08 in the control group (P=0.036). No statistically significant between-group differences were found for the other fetal ultrasonographic variables or for the fetal biometric variables assessed. None of the maternal or fetal parameters assessed displayed a linear correlation with MCA PSV. CONCLUSION: Doppler ultrasonographic measurements of MCA PSV were lowered among the fetuses of women diagnosed with GDM.

Assessment of Single-Barrel Superficial Temporal Artery-Middle Cerebral Artery Bypass in Treatment for Adult Patients with Ischemic-Type Moyamoya Disease.

BACKGROUND Moyamoya disease (MMD) is an idiopathic disease caused by progressive steno-occlusion of the distal internal carotid artery. Ideal surgical treatment for adult patients with ischemic-type MMD has not been achieved. The aim of this study was to evaluate the efficacy of single-barrel superficial temporal artery-middle cerebral artery (STA-MCA) bypass in treatment for adult patients with ischemic-type MMD by analyzing clinical and radiological data retrospectively. MATERIAL AND METHODS The present study included 37 patients with non-hemorrhagic MMD, including 21 women and 16 men (21~55 years old, mean age 38.1 years). The bypass surgery was performed on 56 sides in the 37 patients. The clinical charts, angiographic revascularization, and hemodynamic changes were reviewed at 6-60 months after surgery. RESULTS Among the 37 patients, the clinical symptoms and signs of 32 patients were improved or stabilized. Five patients had complications, including 2 cases of acute cerebral infarction, 1 case of epidural hematoma, and 1 case of transient speech disturbance, and 1 patient died. Follow-up computed tomography perfusion (CTP) revealed that cerebral blood flow (CBF) was markedly improved after surgery (P<0.05). Time to peek (TTP) and mean transit time (MTT) were significantly decreased after surgery (P<0.05). No significant change in cerebral blood volume (CBV) was found after surgery (P>0.05). Postoperative patency was clearly verified in 52 bypasses (92.8%) of 56 bypasses on follow-up DSA imaging. CONCLUSIONS Single-barrel STA-MCA bypass can be considered as an effective surgical treatment, which exhibits satisfactory clinical efficacy in ischemic-type MMD patients.

Perinatal loss at term: role of uteroplacental and fetal Doppler assessment.

OBJECTIVE: To examine the associations of uterine artery (UtA) Doppler indices and cerebroplacental ratio (CPR) with perinatal outcome at term. METHODS: This was a retrospective cohort study conducted at a tertiary referral center that included all singleton pregnancies undergoing ultrasound assessment in the third trimester that subsequently delivered at term. Fetal biometry and Doppler assessment, including that of the umbilical artery (UA), fetal middle cerebral artery (MCA) and UtA, were recorded. Data were corrected for gestational age, and CPR was calculated as the ratio of MCA pulsatility index (PI) to UA-PI. Logistic regression analysis was conducted to examine for independent predictors of adverse perinatal outcome. RESULTS: The study included 7013 pregnancies, 12 of which were complicated by perinatal death. When compared with pregnancies resulting in perinatal survival, pregnancies complicated by perinatal death had a significantly higher proportion of small-for-gestational-age infants (25.0% vs 5%; P = 0.001) and a higher incidence of low (< 5th centile) CPR (16.7% vs 4.5%; P = 0.041). A subgroup analysis comparing 1527 low-risk pregnancies that resulted in fetal survival with pregnancies complicated by perinatal death demonstrated that UtA-PI multiples of the median (MoM), CPR < 5th centile and estimated fetal weight (EFW) centile were all associated significantly with the risk of perinatal death at term (all P < 0.05). After adjusting for confounding variables, only EFW centile (odds ratio (OR) 0.96 (95% CI, 0.93-0.99); P = 0.003) and UtA-PI MoM (OR 13.10 (95%CI, 1.95-87.89); P = 0.008) remained independent predictors of perinatal death in the low-risk cohort. CONCLUSION: High UtA-PI at term is associated independently with an increased risk of adverse perinatal outcome, regardless of fetal size. These results suggest that perinatal mortality at term is related not only to EFW and fetal redistribution (CPR), but also to indices of uterine perfusion. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Changes in Blood Flow Velocity of the Middle Cerebral Artery After Carotid Endarterectomy: Daily Assessment with Transcranial Color-Coded Sonography.

BACKGROUND: Hyperperfusion syndrome (HPS) is a well-known complication of carotid endarterectomy (CEA) warranting repeatable inexpensive monitoring. Transcranial color-coded sonography (TCCS) may provide a potential modality for such monitoring, but little is known about TCCS trends after CEA. METHODS: Between January 2016 and February 2017, we prospectively included patients with CEA at our institute in this study. TCCS was performed preoperatively and repeated daily from the operation day until postoperative day (POD) 7. Daily trends in mean flow velocity (MFV) at the M1 portion of the middle cerebral artery were compared between patients with and without HPS. RESULTS: Among 35 patients with CEA, daily TCCS monitoring was performed in 18 patients (mean age ± SD, 72 ± 7 years; male/female, 17:1). Among these 18 patients, 3 had probable HPS. On POD 0, MFV of the 18 patients showed a 32% increase from the initial preoperative value (from 52.5 to 69.4 cm/s, P = 0.0013). This increased MFV lasted for several days and recovered gradually by POD 7. Patients with probable HPS demonstrated a trend to higher MFV than those without; however, the difference was below the significance level. CONCLUSIONS: We used daily TCCS after CEA to depict cerebral blood flow changes after CEA in our cohort. This technique may be useful both for the detection and prevention of HPS.

Cerebrovascular response to maternal hyperoxygenation in fetuses with hypoplastic left heart syndrome depends on gestational age and baseline cerebrovascular resistance.

OBJECTIVES: Compared with normal fetuses, fetuses with hypoplastic left heart syndrome (HLHS) have smaller brain volumes and are at higher risk of brain injury, possibly due to diminished cerebral blood flow and oxygen content. By increasing cerebral oxygen delivery, maternal hyperoxygenation (MH) might improve brain development and reduce the risk of brain injury in these fetuses. This study investigated whether gestational age and baseline cerebrovascular resistance affect the response to MH in fetuses with HLHS. METHODS: The study population comprised 43 fetuses with HLHS or HLHS variant referred for fetal echocardiography between January 2004 and September 2008. Middle cerebral artery (MCA) pulsatility index (PI), a surrogate measure of cerebrovascular resistance, was assessed between 20 and 41 weeks' gestation at baseline in room air (RA) and after 10 min of MH. Z-scores of MCA-PI were generated. A mixed-effects model was used to determine whether change in MCA-PI depends upon gestational age and baseline MCA-PI. RESULTS: In RA and following MH, MCA-PI demonstrated a curvilinear relationship with gestational age in fetuses with HLHS, peaking at around 28 weeks and then falling more steeply near term. MCA-PI Z-score declined in a linear manner, such that it was 1.4 SD below that in normal fetuses at 38 weeks. Increase in MCA-PI Z-score after MH was first seen at ≥ 28 weeks. A baseline MCA-PI Z-score ≤ -0.96 was predictive of an increase in cerebrovascular resistance in response to MH. CONCLUSION: In fetuses with HLHS, MCA-PI first increases in response to MH at ≥ 28 weeks' gestation. A baseline MCA-PI Z-score ≤ -0.96 predicts an increase in cerebrovascular resistance in response to MH. These results may have implications for clinical trials utilizing MH as a neuroprotective agent. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Stenosis in Middle Cerebral Artery Duplication: Assessment With Transcranial Color-Coded Duplex Sonography.

Duplication of the middle cerebral artery is an unusual anatomic variant. Stenosis of one of its branches can be an exceptional cause of stroke and is very difficult to diagnose with transcranial duplex sonography. We report 2 patients with duplication of the middle cerebral artery in whom stenosis of one of its branches led to ischemic stroke and describe the sonographic findings in comparison to other neuroimaging modalities. These cases highlight the utility of adding a coronal insonation plane on top of the traditional axial plane to avoid identification pitfalls in patients with anatomic variants.

Severity assessment of intracranial large artery stenosis by pressure gradient measurements: A feasibility study.

BACKGROUND: Fractional flow reserve (FFR)-guided revascularization strategy is popular in coronary intervention. However, the feasibility of assessing stenotic severity in intracranial large arteries using pressure gradient measurements still remains unclear. METHODS: Between March 2013 and May 2014, 12 consecutive patients with intracranial large artery stenosis (including intracranial internal carotid artery, middle cerebral M1 segment, intracranial vertebral artery, and basilar artery) were enrolled in this study. The trans-stenotic pressure gradient was measured before and/or after percutaneous transluminal angioplasty and stenting (PTAS), and was then compared with percent diameter stenosis. A Pd /Pa cut-off of ≤0.70 was used to guide stenting of hemodynamically significant stenoses. The device-related and procedure-related serious adverse events and recurrent cerebral ischemic events were recorded. RESULTS: The target vessel could be reached in all cases. No technical complications occurred due to the specific study protocol. Excellent pressure signals were obtained in all patients. For seven patients who performed PTAS, the mean pre-procedural pressure gradient decreased from 59.0 ± 17.2 to 13.3 ± 13.6 mm Hg after the procedure (P < 0.01). Only one patient who refused stenting experienced a TIA event in the ipsilateral MCA territory. No recurrent ischemic event was observed in other patients. CONCLUSION: Mean trans-stenotic pressure gradients can be safely and easily measured with a 0.014-inch fluid-filled guide wire in intracranial large arteries. © 2016 Wiley Periodicals, Inc.

Reliability of Doppler Assessment of the Middle Cerebral Artery in the Near and Far Fields in Healthy and Anemic Fetuses.

OBJECTIVES: The purpose of this study was to assess the reliability of the middle cerebral artery pulsatility index (PI) and peak systolic velocity (PSV) at the proximal portions of the near- and far-field vessel sites in healthy and anemic fetuses. METHODS: The middle cerebral artery PSV and PI were prospectively assessed in 50 normal singleton pregnancies. The Doppler waveforms for the middle cerebral artery PI and the PSV were recorded independently by 2 operators at the most proximal portions of the near- and far-field sites. Data for the PSV and PI at the proximal portions of both the near- and the far-field sites were also retrospectively collected in 7 anemic fetuses. RESULTS: No significant difference between the operators was detected for the middle cerebral artery PSV (P = .60) and PI (P = .88) measured in the conventionally used near-field proximal site in the 50 healthy fetuses. No significant difference between the proximal portions of the near- and far-field sites was detected for the PSV (P = .53) and PI (P = .23) in healthy or anemic fetuses. CONCLUSIONS: The findings of this study suggest that the use of the far-field vessel is an acceptable alternative for measurement of the middle cerebral artery PI and PSV when investigation of the near-field vessel is technically difficult.

Monitoring cerebral autoregulation after brain injury: multimodal assessment of cerebral slow-wave oscillations using near-infrared spectroscopy.

BACKGROUND: Continuous monitoring of cerebral autoregulation might provide novel treatment targets and identify therapeutic windows after acute brain injury. Slow oscillations of cerebral hemodynamics (0.05-0.003 Hz) are visible in multimodal neuromonitoring and may be analyzed to provide novel, surrogate measures of autoregulation. Near-infrared spectroscopy (NIRS) is an optical neuromonitoring technique, which shows promise for widespread clinical applicability because it is noninvasive and easily delivered across a wide range of clinical scenarios. The aim of this study is to identify the relationship between NIRS signal oscillations and multimodal neuromonitoring, examining the utility of near infrared derived indices of cerebrovascular reactivity. METHODS: Twenty-seven sedated, ventilated, brain-injured patients were included in this observational study. Intracranial pressure, transcranial Doppler-derived flow velocity in the middle cerebral artery, and ipsilateral cerebral NIRS variables were continuously monitored. Signals were compared using wavelet measures of phase and coherence to examine the spectral features involved in reactivity index calculations. Established indices of autoregulatory reserve such as the pressure reactivity index (PRx) and mean velocity index (Mx) and the NIRS indices such as total hemoglobin reactivity index (THx) and tissue oxygen reactivity index (TOx) were compared using correlation and Bland-Altman analysis. RESULTS: NIRS indices correlated significantly between PRx and THx (rs = 0.63, P < 0.001), PRx and TOx (r = 0.40, P = 0.04), and Mx and TOx (r = 0.61, P = 0.004) but not between Mx and THx (rs = 0.26, P = 0.28) and demonstrated wide limits between these variables: PRx and THx (bias, -0.06; 95% limits, -0.44 to 0.32) and Mx and TOx (bias, +0.15; 95% limits, -0.34 to 0.64). Analysis of slow-wave activity throughout the intracranial pressure, transcranial Doppler, and NIRS recordings revealed statistically significant interrelationships, which varied dynamically and were nonsignificant at frequencies <0.008 Hz. CONCLUSIONS: Although slow-wave activity in intracranial pressure, transcranial Doppler, and NIRS is significantly similar, it varies dynamically in both time and frequency, and this manifests as incomplete agreement between reactivity indices. Analysis informed by a priori knowledge of physiology underpinning NIRS variables combined with sophisticated analysis techniques has the potential to deliver noninvasive surrogate measures of autoregulation, guiding therapy.

Assessment of middle cerebral artery diameter during hypocapnia and hypercapnia in humans using ultra-high-field MRI.

In the evaluation of cerebrovascular CO2 reactivity measurements, it is often assumed that the diameter of the large intracranial arteries insonated by transcranial Doppler remains unaffected by changes in arterial CO2 partial pressure. However, the strong cerebral vasodilatory capacity of CO2 challenges this assumption, suggesting that there should be some changes in diameter, even if very small. Data from previous studies on effects of CO2 on cerebral artery diameter [middle cerebral artery (MCA)] have been inconsistent. In this study, we examined 10 healthy subjects (5 women, 5 men, age 21-30 yr). High-resolution (0.2 mm in-plane) MRI scans at 7 Tesla were used for direct observation of the MCA diameter during hypocapnia, -1 kPa (-7.5 mmHg), normocapnia, 0 kPa (0 mmHg), and two levels of hypercapnia, +1 and +2 kPa (7.5 and 15 mmHg), with respect to baseline. The vessel lumen was manually delineated by two independent observers. The results showed that the MCA diameter increased by 6.8 ± 2.9% in response to 2 kPa end-tidal P(CO2) (PET(CO2)) above baseline. However, no significant changes in diameter were observed at the -1 kPa (-1.2 ± 2.4%), and +1 kPa (+1.4 ± 3.2%) levels relative to normocapnia. The nonlinear response of the MCA diameter to CO2 was fitted as a continuous calibration curve. Cerebral blood flow changes measured by transcranial Doppler could be corrected by this calibration curve using concomitant PET(CO2) measurements. In conclusion, the MCA diameter remains constant during small deviations of the PET(CO2) from normocapnia, but increases at higher PET(CO2) values.

Transcranial Doppler-based assessment of cerebral autoregulation in critically ill children during diabetic ketoacidosis treatment.

OBJECTIVES: Impaired cerebral autoregulation may be associated with poor outcome in diabetic ketoacidosis. We examined change in cerebral autoregulation during diabetic ketoacidosis treatment. DESIGN: Prospective observational cohort study. SETTING: Tertiary care children's hospital. PATIENTS/SUBJECTS: Children admitted to the ICU with diabetic ketoacidosis (venous pH < 7.3, glucose > 300 mg/dL, HCO3 < 15 mEq/L, and ketonuria) constituted cases, and children with type I diabetes without diabetic ketoacidosis constituted controls. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Between 2005 and 2009, 32 cases and 50 controls were enrolled. Transcranial Doppler ultrasonography was used to measure middle cerebral artery flow velocities, and cerebral autoregulation testing was achieved via tilt-table testing. Cases underwent two and controls underwent one cerebral autoregulation test. Cerebral autoregulation was quantified by the autoregulatory index (autoregulatory index < 0.4 = impaired and autoregulatory index 0.4-1.0 = intact autoregulation). The first autoregulation test was obtained early (time 1, 12-24 hr; median [interquartile range], 8 hr [5-18 hr]) during diabetic ketoacidosis treatment, and a second autoregulation test was obtained during recovery (time 2, 36-72 hr; median [ interquartile range], 46 hr [40-59 hr]) from time 0 (defined as time of insulin start). Cases had lower autoregulatory index at time 1 than time 2 (p < 0.001) as well lower autoregulatory index than control subjects (p < 0.001). Cerebral autoregulation was impaired in 40% (n = 13) of cases at time 1 and in 6% (n = 2) of cases at time 2. Five cases (17%) showed persistent impairment of cerebral autoregulation between times 1 and 2 of treatment. All control subjects had intact cerebral autoregulation. CONCLUSIONS: Impaired cerebral autoregulation was common early during diabetic ketoacidosis treatment. Although the majority improved during diabetic ketoacidosis treatment, 17% of subjects had impairment between 36 and 72 hours after start of insulin therapy. The observed impaired cerebral autoregulation appears specific to the diabetic ketoacidosis process in patients with type I diabetes.

Assessment of motoric and hemodynamic parameters in growth restricted fetuses - case study.

OBJECTIVE: In order to more accurately assess fetal neurological status in five fetuses with severe intrauterine growth restriction (IUGR), combined assessment of their hemodynamics and motor activity was undertaken in this study. METHOD: Hemodynamic changes in the placental and fetal cerebral vessels were evaluated using the umbilical artery resistance index (URI), and the middle cerebral artery resistance index (CRI). The blood flow redistribution towards the fetal brain in response to fetal hypoxia was detected by the C/U (cerebro - umbilical) ratio, expressed as CRI/URI. Motoric parameters were assessed by new antenatal neurologic scoring test named Kurjak Antenatal Neurodevelopmental Test (KANET), based on evaluation of spontaneous motor activity using four-dimensional (4D) ultrasound. RESULTS: KANET has potential in recognizing pathologic and borderline behavior in IUGR fetuses with or without blood flow redistribution towards the fetal brain. Very low values of C/U ratio and abnormal KANET score have indicated adverse pregnancy outcome. CONCLUSION: In some pregnancies complicated with IUGR, estimation of the risk of hypoxia versus prematurity can be extremely puzzling. Combined assessment of hemodynamic and motoric parameters in IUGR fetuses could allow construction of an algorithm, which would be helpful in the decision making process of pregnancy termination.

Whole-brain CT perfusion and CT angiography assessment of Moyamoya disease before and after surgical revascularization: preliminary study with 256-slice CT.

BACKGROUND/AIMS: The 256-slice CT enables the entire brain to be scanned in a single examination. We evaluated the application of 256-slice whole-brain CT perfusion (CTP) in determining graft patency as well as investigating cerebral hemodynamic changes in Moyamoya disease before and after surgical revascularization. METHODS: Thirty-nine cases of Moyamoya disease were evaluated before and after surgical revascularization with 256-slice CT. Whole-brain perfusion images and dynamic 3D CT angiographic images generated from perfusion source data were obtained in all patients. Cerebral blood flow (CBF), cerebral blood volume (CBV), time to peak (TTP) and mean transit time (MTT) of one hemisphere in the region of middle cerebral artery (MCA) distribution and contralateral mirroring areas were measured. Relative CTP values (rCBF, rCBV, rTTP, rMTT) were also obtained. Differences in pre- and post- operation perfusion CT values were assessed with paired t test or matched-pairs signed-ranks test. RESULTS: Preoperative CBF, MTT and TTP of potential surgical side were significantly different from those of contralateral side (P<0.01 for all). All graft patencies were displayed using the 3D-CTA images. Postoperative CBF, rCBF and rCBV values of surgical side in the region of MCA were significantly higher than those before operation (P<0.01 for all). Postoperative MTT, TTP, rMTT and rTTP values of the surgical side in the region of MCA were significantly lower than those before operation (P<0.05 for all). CONCLUSION: The 256-slice whole-brain CTP can be used to evaluate cerebral hemodynamic changes in Moyamoya disease before and after surgery and the 3D-CTA is useful for assessing the abnormalities of intracranial arteries and graft patencies.