Natural History of Hemodynamics in Vertebrobasilar Disease: Temporal Changes in the VERiTAS Study Cohort.

BACKGROUND AND PURPOSE: The role of regional hypoperfusion as a contributor to stroke risk in atherosclerotic vertebrobasilar disease has recently been confirmed by the observational VERiTAS (Vertebrobasilar Flow Evaluation and Risk of Transient Ischemic Attack and Stroke) Study. We examined the stability of hemodynamic status over time and its relationship to stroke risk in patients from this prospective cohort. METHODS: VERiTAS enrolled patients with recently symptomatic ≥50% atherosclerotic stenosis/occlusion of vertebral and/or basilar arteries. Large vessel flow in the vertebrobasilar territory was assessed using quantitative magnetic resonance angiography, and patients were designated as low or normal flow based on distal territory regional flow, incorporating collateral capacity. Patients underwent standard medical management and follow-up for primary outcome event of vertebrobasilar territory stroke. Quantitative magnetic resonance angiography imaging was repeated at 6, 12, and 24 months. Flow status over time was examined relative to baseline and relative to subsequent stroke risk using a cause-specific proportional hazard model, with flow status treated as a time-varying covariate. Mean blood pressure was examined to assess for association with changes in flow status. RESULTS: Over 19±8 months of follow-up, 132 follow-up quantitative magnetic resonance angiography studies were performed in 58 of the 72 enrolled patients. Of the 13 patients with serial imaging who had low flow at baseline, 7 (54%) had improvement to normal flow at the last follow-up. Of the 45 patients who had normal flow at baseline, 3 (7%) converted to low flow at the last follow-up. The mean blood pressure did not differ in patients with or without changes in flow status. The time-varying flow status remained a strong predictor of subsequent stroke (hazard ratio, 10.3 [95% CI, 2.2-48.7]). CONCLUSIONS: There is potential both for improvement and worsening of hemodynamics in patients with atherosclerotic vertebrobasilar disease. Flow status, both at baseline and over time, is a risk factor for subsequent stroke, thus serving as an important prognostic marker. Registration: URL: https://clinicaltrials.gov. Unique identifier: NCT00590980.

Hypoperfusion Symptoms Poorly Predict Hemodynamic Compromise and Stroke Risk in Vertebrobasilar Disease.

Background and Purpose- Cerebral hypoperfusion symptoms (defined as symptoms related to change in position, effort or exertion, or recent change in antihypertensive medication) have been used in stroke studies as a surrogate for detecting hemodynamic compromise. However, the validity of these symptoms in identifying flow compromise in patients has not been well established. We examined whether hypoperfusion symptoms correlated with quantitative measurements of flow compromise in the prospective, observational VERiTAS study (Vertebrobasilar Flow Evaluation and Risk of Transient Ischemic Attack and Stroke). Methods- VERiTAS enrolled patients with recent vertebrobasilar transient ischemic attack or stroke and ≥50% atherosclerotic stenosis or occlusion in vertebral or basilar arteries. Hemodynamic status using vertebrobasilar large vessel flow was measured using quantitative magnetic resonance angiography, and patients were designated as low, borderline, or normal flow based on distal territory regional flow, incorporating collateral capacity. The presence of qualifying event hypoperfusion symptoms was assessed relative to the quantitatively determined flow status (normal versus borderline/low) and also examined as a predictor of subsequent stroke risk. Results- Of the 72 enrolled subjects, 66 had data on hypoperfusion symptoms available. On initial quantitative magnetic resonance angiography designation, 43 subjects were designated as normal flow versus 23 subjects designated as low flow (n=16) or borderline flow (n=7). Of these, 5 (11.6%) normal flow and 3 (13.0%) low/borderline flow subjects reported at least one qualifying event hypoperfusion symptom ( P=0.99, Fisher exact test). Hypoperfusion symptoms had a positive predictive value of 37.5% and negative predictive value of 65.5% for low/borderline flow status. Compared with flow status, which strongly predicted subsequent stroke risk, hypoperfusion symptoms were not associated with stroke outcome ( P=0.87, log-rank test). Conclusions- These results suggest that hypoperfusion symptoms alone correlate poorly with actual hemodynamic compromise as assessed by quantitative magnetic resonance angiography and subsequent stroke risk in vertebrobasilar disease, and are not a reliable surrogate for flow measurement. Clinical Trial Registration- URL: https://www.clinicaltrials.gov . Unique identifier: NCT00590980.

Cost-Effectiveness of Quantitative Magnetic Resonance Angiography Screening and Submaximal Angioplasty for Symptomatic Vertebrobasilar Disease.

Background and Purpose- The VERiTAS (Vertebrobasilar Flow Evaluation and Risk of Transient Ischemic Attack and Stroke) study demonstrated posterior circulation distal flow status, determined by quantitative magnetic resonance angiography, is a robust predictor of vertebrobasilar stroke risk in patients with symptomatic atherosclerotic vertebrobasilar disease. Flow-compromised high-risk patients may benefit from flow-restoring endovascular procedures, such as submaximal angioplasty. In this study, we examine the cost-effectiveness of quantitative magnetic resonance angiography screening to identify patients who may benefit from submaximal angioplasty to restore vertebrobasilar flow. Methods- A Markov model was created comparing a no screening strategy with standard medical management alone and a screening strategy involving quantitative magnetic resonance angiography imaging and submaximal angioplasty for treatable patients with low vertebrobasilar flow for a 30-year time horizon. Outcomes included quality-adjusted life years (QALY) and lifetime costs. Rates of stroke and death were obtained from VERiTAS data, and disability rates and costs were derived from VERiTAS and the literature. A sensitivity analysis was performed with periprocedural stroke rate from angioplasty the primary variable of interest. Results- At a 6% periprocedural stroke risk, the screening strategy saved an average of 0.364 QALYs per patient and a lifetime cost savings of $7312 versus the no screening strategy. Among patients with low flow suitable for intervention, the benefit was substantially higher, averaging 1.485 QALYs saved and lifetime cost savings of $21 294. Across the entire cohort, QALY savings were observed at the end of the first year and economic savings at year 6. The benefit of screening declined at higher periprocedural risk. Conclusions- Quantitative magnetic resonance angiography screening and submaximal angioplasty with 6% periprocedural risk in suitable patients are cost effective both in terms of QALY and lifetime costs for patients with symptomatic vertebrobasilar occlusive disease. With potential health and economic savings, a clinical trial examining the periprocedural risk of submaximal angioplasty is warranted. Clinical Trial Registration- URL: http://www.clinicaltrials.gov . Unique identifier: NCT00590980.

Higher Stroke Risk with Lower Blood Pressure in Hemodynamic Vertebrobasilar Disease: Analysis from the VERiTAS Study.

BACKGROUND: Despite concerns regarding hypoperfusion in patients with large-artery occlusive disease, strict blood pressure (BP) control has become adopted as a safe strategy for risk reduction of stroke. We examined the relationship between BP control, blood flow, and risk of subsequent stroke in the prospective Vertebrobasilar Flow Evaluation and Risk of Transient Ischemic Attack and Stroke (VERiTAS) study. METHODS: The VERiTAS study enrolled patients with recent vertebrobasilar (VB) transient ischemic attack or stroke and ≥50% atherosclerotic stenosis or occlusion of vertebral or basilar arteries. Hemodynamic status was designated as low or normal based on quantitative magnetic resonance angiography. Patients underwent standard medical management and follow-up for primary outcome event of VB territory stroke. Mean BP during follow-up (<140/90 versus ≥140/90 mm Hg) and flow status were examined relative to subsequent stroke risk using Cox proportional hazards analysis. RESULTS: The 72 subjects had an average of 3.8 ± 1.2 BP recordings over 20 ± 8 months of follow-up; 39 (54%) had mean BP of<140/90 mm Hg. The BP groups were largely comparable for baseline demographics, risk factors, and stenosis severity. Comparing subgroups stratified by BP and hemodynamic status, we found that patients with both low flow and BP <140/90 mm Hg (n = 10) had the highest risk of subsequent stroke, with hazard ratio of 4.5 (confidence interval 1.3-16.0, P = .02), compared with the other subgroups combined. CONCLUSIONS: Among a subgroup of patients with VB disease and low flow, strict BP control (BP <140/90) may increase the risk of subsequent stroke.

Hemodynamic Features of Symptomatic Vertebrobasilar Disease.

BACKGROUND AND PURPOSE: Atherosclerotic vertebrobasilar disease is an important cause of posterior circulation stroke. To examine the role of hemodynamic compromise, a prospective multicenter study, Vertebrobasilar Flow Evaluation and Risk of Transient Ischemic Attack and Stroke (VERiTAS), was conducted. Here, we report clinical features and vessel flow measurements from the study cohort. METHODS: Patients with recent vertebrobasilar transient ischemic attack or stroke and ≥50% atherosclerotic stenosis or occlusion in vertebral or basilar arteries (BA) were enrolled. Large-vessel flow in the vertebrobasilar territory was assessed using quantitative MRA. RESULTS: The cohort (n=72; 44% women) had a mean age of 65.6 years; 72% presented with ischemic stroke. Hypertension (93%) and hyperlipidemia (81%) were the most prevalent vascular risk factors. BA flows correlated negatively with percentage stenosis in the affected vessel and positively to the minimal diameter at the stenosis site (P<0.01). A relative threshold effect was evident, with flows dropping most significantly with ≥80% stenosis/occlusion (P<0.05). Tandem disease involving the BA and either/both vertebral arteries had the greatest negative impact on immediate downstream flow in the BA (43 mL/min versus 71 mL/min; P=0.01). Distal flow status assessment, based on an algorithm incorporating collateral flow by examining distal vessels (BA and posterior cerebral arteries), correlated neither with multifocality of disease nor with severity of the maximal stenosis. CONCLUSIONS: Flow in stenotic posterior circulation vessels correlates with residual diameter and drops significantly with tandem disease. However, distal flow status, incorporating collateral capacity, is not well predicted by the severity or location of the disease.

Effects of extracranial carotid stenosis on intracranial blood flow.

BACKGROUND AND PURPOSE: The hemodynamic effects of extracranial carotid stenosis on intracranial blood flow are not well characterized. We sought to determine the impact of degree of stenosis, stenosis length, and residual lumen on intracranial blood flow in patients with extracranial carotid stenosis. METHODS: Carotid stenosis patients who had undergone both vessel flow rate measurements using quantitative magnetic resonance angiography and digital subtraction angiography were examined. The impact of the anatomic measurements of the stenosis relative to ipsilateral internal carotid artery (ICA) flow and ipsilateral-to-contralateral middle cerebral artery (MCA) flow ratio were assessed. RESULTS: Forty-four patients (mean age, 67 years; 64% symptomatic) were included. Higher percentage stenosis and smaller residual lumen were associated with a significant decrease in ICA flow (P<0.01 and 0.04, respectively). On multivariate analysis, percentage stenosis remained as the primary predictor of ICA flow (P<0.001). MCA flow ratio was not significantly associated with percentage stenosis, stenosis length, or residual lumen. However, mean MCA flow ratio was significantly lower in symptomatic compared with asymptomatic patients (0.92 versus 1.22; P=0.001). In contrast, mean ICA flow ratio was similar among these 2 groups (0.55 versus 0.55; P=0.99). CONCLUSIONS: Percentage stenosis and residual lumen are significantly associated with ICA but not MCA flow, suggesting that local hemodynamic effects of carotid stenosis do not translate directly to distal vasculature, because intracranial flows can be maintained through collaterals. The lower MCA flow ratio in symptomatic patients highlights the potential importance of distal hemodynamics in symptomatic presentation.

A patient-specific circle of Willis blood flow model in predicting outcomes of balloon test occlusion.

BACKGROUND AND PURPOSE: Balloon test occlusion (BTO) evaluates cerebral ischemic tolerance before internal carotid artery (ICA) sacrifice but carries risks like dissection and thrombosis. This study introduces a new approach using a patient-specific circle of Willis (COW) blood flow model, based on non-invasive quantitative MR angiography (qMRA) measurements, to predict the outcomes of BTO. METHODS: We developed individualized COW blood flow models for 43 patients undergoing BTO. These models simulated blood flow and pressure under normal conditions and with the ICA occlusion. We then compared the model's predictions of blood flow changes due to the simulated ICA occlusion to actual qMRA measurements before the BTO. RESULTS: For all 31 BTO failures, the ipsilateral hemisphere showed an average flow decrease of 15 ± 10% (mean ± standard deviation), compared to 3 ± 2% in the contralateral hemisphere. In all 12 BTO passes, these figures were 6 ± 3% and 1 ± 0.8%, respectively. Notably, all BTO passes had less than a 10% reduction in the ipsilateral hemisphere. In contrast, 65% of BTO failures and 67% single-photon emission computed tomography (SPECT) failures exhibited a decrease of 10% or more in the same region. CONCLUSION: Blood flow reduction exceeding 10% in the ipsilateral hemisphere during BTO is a strong predictor of failure in both BTO and SPECT. Our patient-specific COW blood flow models, incorporating detailed flow and arterial geometry data, offered valuable insights for predicting BTO outcomes. These models are especially beneficial for situations where conducting BTO or SPECT is clinically impractical.

Evaluating outcome associations with race after mechanical thrombectomy: an analysis of the NVQI-QOD acute ischemic stroke registry.

BACKGROUND: Mechanical thrombectomy has become the standard of care for acute ischemic stroke due to large vessel occlusions. Racial differences in outcomes after mechanical thrombectomy for acute ischemic stroke have not been extensively studied. We evaluate the real-world evidence for differences between races in the outcomes of thrombectomy for large vessel occlusions using the NeuroVascular Quality Initiative-Quality Outcomes Database (NVQI-QOD). METHODS: Data from the NVQI-QOD acute ischemic stroke registry were analyzed and compared for racial differences in outcomes after mechanical thrombectomy in 4507 patients from 28 US centers (17 states) between January 2014 and April 2021. Race was dichotomized into non-Hispanic White (NHW, n=3649) and non-Hispanic Black (NHB, n=858). We performed 1:1 propensity score matching resulting in a subsample of matched groups (n=761 each for NHB and NHW) to compare study endpoints using Welch's two-sided t-tests and Χ2 test for continuous and categorical outcomes, respectively. RESULTS: Prior to matching, NHW and NHB patients significantly differed in age, comorbidities, medication use, smoking status, and presenting stroke severity. No significant difference in functional outcomes or mortality, at discharge or follow-up, were revealed. NHB patients had higher average postprocedure length of stay than NHW patients, which persisted following matching (11.2 vs 9.1 days, P=0.004). CONCLUSION: Evidence from the NVQI-QOD acute ischemic stroke registry showed that outcome metrics, such as modified Rankin Scale score and mortality, did not differ significantly between racial groups; however, disparity between NHW and NHB patients in postprocedure length of stay following mechanical thrombectomy was revealed.

Perfusion-MRI is a Poor Indicator of Hemodynamic Compromise in Vertebrobasilar Disease in the VERiTAS Study.

BACKGROUND AND PURPOSE: Dynamic susceptibility perfusion MR imaging (DSC MRP) has been used to assess changes in cerebral perfusion attributable to vascular stenosis or occlusion that may predict stroke risk. However, DSC MRP is not validated for identifying hemodynamic compromise in the posterior circulation. We investigated the clinical utility of DSC MRP in vertebrobasilar (VB) atherosclerotic disease in the observational VERiTAS study. METHODS: VERiTAS enrolled patients with symptomatic ≥50% VB stenosis/occlusion. Posterior circulation hemodynamic status was designated as low or normal based on large vessel flow measured using quantitative magnetic resonance angiography (QMRA) and was predictive of future stroke risk. In this study, DSC MRP conducted concurrently with QMRA was used to evaluate posterior circulation perfusion. The primary outcome was the mean transit time (MTT) and relative cerebral blood volume (rCBV) in the posterior circulation normalized to the anterior circulation, compared between patients with low and normal blood flow as determined on QMRA. RESULTS: Twenty-six subjects had 47 DSC MRP studies for review. There was no statistically or clinically significant difference in the rCBV ratio (1.02 vs. .96 P = .89), or MTT ratio (1.04 vs. 1.04 P = .96) relative to normal or low VB territory flow. CONCLUSIONS: In this study, we did not find that DSC MRP adequately distinguished between patients with low or normal flow status based on large-vessel flow measurements.

Socioeconomic Inequities in the Surgical Management of Moyamoya Disease.

BACKGROUND: Given the vasculopathic nature of moyamoya disease (MMD) and high susceptibility to ischemic events, patients with MMD often require surgical revascularization via an indirect or direct bypass, and analysis of disparities in receipt of appropriate management is critical. METHODS: The 2012-2016 Nationwide Inpatient Sample was queried for patients admitted with a diagnosis of MMD using International Classification of Diseases codes. Patient baseline demographics, hospital characteristics, and associated symptoms were collected. Patients were grouped by receipt of bypass procedure, and propensity score matching was performed to identify socioeconomic disparities between operative and nonoperative groups. RESULTS: Inclusion criteria were met by 4474 patients (827 pediatric patients and 3647 adult patients). Mean (SD) age for pediatric patients was 10.4 (4.6) years and for adult patients was 40.5 (14.4) years. Among pediatric patients, Black and Hispanic/Latino patients were less likely to undergo revascularization surgery (odds ratio [OR] 0.49, 95% confidence interval [CI] 0.21-0.78, P ≤ 0.01; OR 0.47, 95% CI 0.26-0.84, P = < 0.01, respectively); among adult patients, Black and Hispanic/Latino patients were similarly less likely to undergo bypass procedures (OR 0.60, 95% CI 0.49-0.72, P ≤ 0.01; OR 0.73, 95% CI 0.55-0.96, P = 0.01, respectively). Pediatric and adult patients in the lowest and next to lowest income quartiles were also less likely to receive operative treatment (pediatric patients: OR 0.61, 95% CI 0.40-0.94, P = 0.02; OR 0.64, 95% CI 0.42-0.98, P = 0.04, respectively; adult patients: OR 0.82, 95% CI 0.88-0.98, P = 0.03). CONCLUSIONS: Further investigation into socioeconomic disparities in adult and pediatric patients with MMD is warranted given the potential for inequities in access to appropriate intervention.

Optimal timing and sequence of ventriculoperitoneal shunt and gastrostomy placement.

Background: The optimal timing of ventriculoperitoneal shunt (VPS) and gastrostomy placement, relative to the safety of simultaneous versus staged surgery, has not been clearly delineated in the literature.Objective: To study the optimal inter-procedural timing relative to distal VPS infection and pertinent reoperation.Methods: A fifteen-year, retrospective, single-center study was conducted on adults undergoing VPS and gastrostomy within 30-days. Patients were grouped according to inter-procedural interval: 0-24 hr (immediate), 24 hr-7 days (early), and 7-30 days (delayed). The primary endpoint of the study was VPS infection and distal shunt complications requiring reoperation. Potential predictors of the primary end point (baseline cohort characteristics, procedural factors) were examined with standard statistical methods.Results: A total of 188 patients met inclusion criteria. The average interval between procedures was 7 ± 6 days, with 43.1% undergoing VPS prior to gastrostomy. Primary endpoint was encountered in 5 patients (2.7%): 1 (5.9%) of 17 patients undergoing immediate placement, 3 (2.8%) of 107 with early placement, and 1 (1.6%) of 64 with delayed placement. Although not statistically significant, 3.7% of patients undergoing VPS first had the primary endpoint, compared to 1.9% of those with gastrostomy. There were no statistically significant associations between the primary outcome and peri-operative CSF counts, gastrostomy modality, hydrocephalus etiology, chronic steroid use, or extended antibiotic administration.Conclusion: Although the low overall event rate in this cohort precludes definitive determination regarding differential safety, the data generally support a practice of performing the procedures >24-hours apart, with placement of gastrostomy prior to VPS.

Quantification of blood flow patterns in the cerebral arterial circulation of individual (human) subjects.

There is a growing research interest in quantifying blood flow distribution for the entire cerebral circulation to sharpen diagnosis and improve treatment options for cerebrovascular disease of individual patients. We present a methodology to reconstruct subject-specific cerebral blood flow patterns in accordance with physiological and fluid mechanical principles and optimally informed by in vivo neuroimage data of cerebrovascular anatomy and arterial blood flow rates. We propose an inverse problem to infer blood flow distribution across the visible portion of the arterial network that best matches subject-specific anatomy and a given set of volumetric flow measurements. The optimization technique also mitigates the effect of uncertainties by reconciling incomplete flow data and by dissipating unavoidable acquisition errors associated with medical imaging data.

Optimized Hemodynamic Assessment to Predict Stroke Risk in Vertebrobasilar Disease: Analysis From the VERiTAS Study.

Background Atherosclerotic vertebrobasilar disease is a significant etiology of posterior circulation stroke. The prospective observational VERiTAS (Vertebrobasilar Flow Evaluation and Risk of Transient Ischemic Attack and Stroke) study demonstrated that distal hemodynamic status is a robust predictor of subsequent vertebrobasilar stroke risk. We sought to compare predictive models using thresholds for posterior circulation vessel flows standardized to age and vascular anatomy to optimize risk prediction. Methods and Results VERiTAS enrolled patients with recent vertebrobasilar transient ischemic attack or stroke and ≥50% atherosclerotic stenosis/occlusion in vertebral and/or basilar arteries. Quantitative magnetic resonance angiography measured large-vessel vertebrobasilar territory flow, and patients were designated as low or normal flow based on a prespecified empiric algorithm considering distal territory regional flow and collateral capacity. For the present study, post hoc analysis was performed to generate additional predictive models using age-specific normalized flow measurements. Sensitivity, specificity, and time-to-event analyses were compared between the algorithms. The original prespecified algorithm had 50% sensitivity and 79% specificity for future stroke risk prediction; using a predictive model based on age-normalized flows in the basilar and posterior cerebral arteries, standardized to vascular anatomy, optimized flow status thresholds were identified. The optimized algorithm maintained sensitivity and increased specificity to 84%, while demonstrating a larger and more significant hazard ratio for stroke on time-to-event analysis. Conclusions These results indicate that flow remains a strong predictor of stroke across different predictive models, and suggest that prediction of future stroke risk can be optimized by use of vascular anatomy and age-specific normalized flows.

A patient-specific cerebral blood flow model.

In clinical practice, many complex choices in treatment of complex cerebrovascular diseases have to be made. A patient-specific mathematical blood flow could aid these decisions. For certain cases, less accuracy is required and more simplistic models might be feasible. The current study is aiming to validate a patient-specific simplistic blood flow model in 20 healthy subjects. All subjects underwent MRI and Noninvasive Optimal Vessel Analysis (NOVA) to obtain patient-specific vascular morphology and flow measurements of all major cerebral arteries for validation. The mathematical model used was based on the Hagen-Poiseuille equations. Proximal boundary conditions were patient-specific blood pressure cuff measurements. For distal boundary conditions, a structured tree and a simple autoregulatory model were applied. Autoregulatory parameters were optimized based on the data of 10 additional healthy subjects. A median percentual flow difference of -3% (interquartile range -36% to 17%) was found. Regression analysis to an identity line resulted in R2 values of 0.71 for absolute flow values. Bland-Altman plots showed a bias (levels of agreement) of 5% (-70 to 80%) for absolute flow. Based on these results the model proved to be accurate within a range that might be feasible for use in clinic. Major limitations to the model arise from the simplifications made compared to the actual physiological situation and limitations in the validation method. As the model is validated in healthy subjects only, further validation in actual patients is needed.

A New Scoring System for Prediction of Underlying Vascular Pathology in Patients with Intracerebral Hemorrhage: The Modified Secondary Intracerebral Hemorrhage Score.

BACKGROUND: Secondary intracerebral hemorrhage (SICH) score is used to predict risk of intracranial hemorrhage (ICH) associated vascular lesions. However, it has low clinical utility in identifying patients without need for neurovascular imaging. This study aims to develop a modified scoring system to capture patients with low risk of underlying vascular pathology, thereby decreasing need for vascular imaging and its associated morbidity. METHODS: A retrospective analysis of 994 patients with atraumatic ICH over 8 years was conducted, excluding known underlying pathology, subarachnoid hemorrhage, or lack of vascular imaging. Using a multivariate logistic regression model, independent predictors of vascular pathology were identified and utilized toward developing a modified Secondary Intracerebral Hemorrhage (mSICH) score. RESULTS: Of 575 patients identified, 60 (10.4%) had underlying vascular etiology. Statistically significant predictors of vascular pathology included age; female sex; admission systolic blood pressure <160 mm Hg; locations other than basal ganglia, thalamus, pons, or midbrain; presence of high-risk imaging features; and proximity to large vessel-containing cisterns. The mSICH score correlated with an increasing incidence of vascular pathology [0-1 (0%), 9 (4.3%), 12 (9.7%), 21 (40.4%), 6 (33.3%), 8 (88.9%), and 4 (100%)] and had a significantly higher number of patients receiving scores with 0% incidence of vascular lesions compared with the SICH score [159 (27.6%) versus 12 (2.1%); P < 0.001)]. CONCLUSIONS: The mSICH score can more accurately predict risk of underlying vascular pathology of ICH and identify patients with lowest risk of vascular pathology. This may minimize the cost and associated risks of invasive cerebrovascular imaging.

Primary hepatic mucosa-associated lymphoid tissue lymphoma: A case report and literature review.

RATIONALE: Primary hepatic mucosa-associated lymphoid tissue (MALT) lymphoma is a rare disease, and there is no consensus yet on the treatment modalities. Here, we report a new case of MALT lymphoma and review the current literature on this disease. PATIENT CONCERNS: A 73-year-old man was admitted to our department following the incidental finding of a solitary 1.8-cm diameter mass in the liver. DIAGNOSIS: Microscopic findings identified the mass as a tumor with infiltration of diffuse atypical B lymphocytes. Immunohistochemical analysis showed positivity for CD20 and CD79a, and negativity for CD3 and CD5. These collective data led to the diagnosis of primary hepatic MALT lymphoma. INTERVENTIONS: The tumor was removed by surgical resection. The patient refused additional treatment after the surgery. OUTCOMES: At the time of writing this report, the patient has been disease free for 6 months postsurgery. LESSONS: Review of the previously published case reports on this rare tumor type indicates that in addition to chronic liver inflammation due to infection or other reasons, genetic aberrations can also contribute to the development of hepatic MALT lymphoma. Additionally, IgH rearrangement is a good genetic hallmark of this tumor. Owing to no specific clinical or radiologic features to define the disease profile for diagnosis, surgery may be a good choice for both diagnosis and therapy if the patient's condition permits.

An efficient full space-time discretization method for subject-specific hemodynamic simulations of cerebral arterial blood flow with distensible wall mechanics.

A computationally inexpensive mathematical solution approach using orthogonal collocations for space discretization with temporal Fourier series is proposed to compute subject-specific blood flow in distensible vessels of large cerebral arterial networks. Several models of wall biomechanics were considered to assess their impact on hemodynamic predictions. Simulations were validated against in vivo blood flow measurements in six human subjects. The average root-mean-square relative differences were found to be less than 4.3% for all subjects with a linear elastic wall model. This discrepancy decreased further in a viscoelastic Kelvin-Voigt biomechanical wall. The results provide support for the use of collocation-Fourier series approach to predict clinically relevant blood flow distribution and collateral blood supply in large portions of the cerebral circulation at reasonable computational costs. It thus opens the possibility of performing computationally inexpensive subject-specific simulations that are robust and fast enough to predict clinical results in real time on the same day.

Quantification of near-wall hemodynamic risk factors in large-scale cerebral arterial trees.

Detailed hemodynamic analysis of blood flow in pathological segments close to aneurysm and stenosis has provided physicians with invaluable information about the local flow patterns leading to vascular disease. However, these diseases have both local and global effects on the circulation of the blood within the cerebral tree. The aim of this paper is to demonstrate the importance of extending subject-specific hemodynamic simulations to the entire cerebral arterial tree with hundreds of bifurcations and vessels, as well as evaluate hemodynamic risk factors and waveform shape characteristics throughout the cerebral arterial trees. Angioarchitecture and in vivo blood flow measurement were acquired from healthy subjects and in cases with symptomatic intracranial aneurysm and stenosis. A global map of cerebral arterial blood flow distribution revealed regions of low to high hemodynamic risk that may significantly contribute to the development of intracranial aneurysms or atherosclerosis. Comparison of pre-intervention and post-intervention of pathological cases further shows large angular phase shift (~33.8°), and an augmentation of the peak-diastolic velocity. Hemodynamic indexes of waveform analysis revealed on average a 16.35% reduction in the pulsatility index after treatment from lesion site to downstream distal vessels. The lesion regions not only affect blood flow streamlines of the proximal sites but also generate pulse wave shift and disturbed flow in downstream vessels. This network effect necessitates the use of large-scale simulation to visualize both local and global effects of pathological lesions.

Evaluation of extracranial-intracranial bypass using quantitative magnetic resonance angiography.

OBJECT: To date, angiography has been the primary modality for assessing graft patency following extracranial-intracranial bypass. The utility of a noninvasive and quantitative method of assessing bypass function postoperatively was evaluated using quantitative magnetic resonance (MR) angiography. METHODS: One hundred one cases of bypass surgery performed over a 5.5-year period at a single institution were reviewed. In 62 cases, both angiographic and quantitative MR angiographic data were available. Intraoperative flow measurements were available in 13 cases in which quantitative MR angiography was performed during the early postoperative period (within 48 hours after surgery). There was excellent correlation between quantitative MR angiographic flow and angiographic findings over the mean 10 months of imaging follow up. Occluded bypasses were consistently absent on quantitative MR angiograms (four cases). The flow rates were significantly lower in those bypasses that became stenotic or reduced in diameter as demonstrated by follow-up angiography (nine cases) than in those bypasses that remained fully patent (mean +/- standard error of the mean, 37 +/- 13 ml/minute compared with 105 +/- 7 ml/minute, p = 0.001). Flows were appreciably lower in poorly functioning bypasses for both vein and in situ arterial grafts. All angiographically poor bypasses (nine cases) were identifiable by absolute flows of less than 20 ml/minute or a reduction in flow greater than 30% within 3 months. Good correlation was seen between intraoperative flow measurements and early postoperative quantitative MR angiographic flow measurements (13 cases, Pearson correlation coefficient = 0.70, p = 0.02). CONCLUSIONS: Bypass grafts can be assessed in a noninvasive fashion by using quantitative MR angiography. This imaging modality provides not only information regarding patency as shown by conventional angiography, but also a quantitative assessment of bypass function. In this study, a low or rapidly decreasing flow was indicative of a shrunken or stenotic graft. Quantitative MR angiography may provide an alternative to standard angiography for serial follow up of bypass grafts.

Large-scale subject-specific cerebral arterial tree modeling using automated parametric mesh generation for blood flow simulation.

In this paper, we present a novel technique for automatic parametric mesh generation of subject-specific cerebral arterial trees. This technique generates high-quality and anatomically accurate computational meshes for fast blood flow simulations extending the scope of 3D vascular modeling to a large portion of cerebral arterial trees. For this purpose, a parametric meshing procedure was developed to automatically decompose the vascular skeleton, extract geometric features and generate hexahedral meshes using a body-fitted coordinate system that optimally follows the vascular network topology. To validate the anatomical accuracy of the reconstructed vasculature, we performed statistical analysis to quantify the alignment between parametric meshes and raw vascular images using receiver operating characteristic curve. Geometric accuracy evaluation showed an agreement with area under the curves value of 0.87 between the constructed mesh and raw MRA data sets. Parametric meshing yielded on-average, 36.6% and 21.7% orthogonal and equiangular skew quality improvement over the unstructured tetrahedral meshes. The parametric meshing and processing pipeline constitutes an automated technique to reconstruct and simulate blood flow throughout a large portion of the cerebral arterial tree down to the level of pial vessels. This study is the first step towards fast large-scale subject-specific hemodynamic analysis for clinical applications.