Trial Readiness of Cavernous Malformations With Symptomatic Hemorrhage, Part I: Event Rates and Clinical Outcome.

BACKGROUND: Cerebral cavernous malformation with symptomatic hemorrhage (SH) are targets for novel therapies. A multisite trial-readiness project (https://www.clinicaltrials.gov; Unique identifier: NCT03652181) aimed to identify clinical, imaging, and functional changes in these patients. METHODS: We enrolled adult cerebral cavernous malformation patients from 5 high-volume centers with SH within the prior year and no planned surgery. In addition to clinical and imaging review, we assessed baseline, 1- and 2-year National Institutes of Health Stroke Scale, modified Rankin Scale, European Quality of Life 5D-3 L, and patient-reported outcome-measurement information system, Version 2.0. SH and asymptomatic change rates were adjudicated. Changes in functional scores were assessed as a marker for hemorrhage. RESULTS: One hundred twenty-three, 102, and 69 patients completed baseline, 1- and 2-year clinical assessments, respectively. There were 21 SH during 178.3 patient years of follow-up (11.8% per patient year). At baseline, 62.6% and 95.1% of patients had a modified Rankin Scale score of 1 and National Institutes of Health Stroke Scale score of 0 to 4, respectively, which improved to 75.4% (P=0.03) and 100% (P=0.06) at 2 years. At baseline, 74.8% had at least one abnormal patient-reported outcome-measurement information system, Version 2.0 domain compared with 61.2% at 2 years (P=0.004). The most common abnormal European Quality of Life 5D-3 L domains were pain (48.7%), anxiety (41.5%), and participation in usual activities (41.4%). Patients with prospective SH were more likely than those without SH to display functional decline in sleep, fatigue, and social function patient-reported outcome-measurement information system, Version 2.0 domains at 2 years. Other score changes did not differ significantly between groups at 2 years. The sensitivity of scores as an SH marker remained poor at the time interval assessed. CONCLUSIONS: We report SH rate, functional, and patient-reported outcomes in trial-eligible cerebral cavernous malformation with SH patients. Functional outcomes and patient-reported outcomes generally improved over 2 years. No score change was highly sensitive or specific for SH and could not be used as a primary end point in a trial.

Trial Readiness of Cavernous Malformations With Symptomatic Hemorrhage, Part II: Biomarkers and Trial Modeling.

BACKGROUND: Quantitative susceptibility mapping (QSM) and dynamic contrast-enhanced quantitative perfusion (DCEQP) magnetic resonance imaging sequences assessing iron deposition and vascular permeability were previously correlated with new hemorrhage in cerebral cavernous malformations. We assessed their prospective changes in a multisite trial-readiness project. METHODS: Patients with cavernous malformation and symptomatic hemorrhage (SH) in the prior year, without prior or planned lesion resection or irradiation were enrolled. Mean QSM and DCEQP of the SH lesion were acquired at baseline and at 1- and 2-year follow-ups. Sensitivity and specificity of biomarker changes were analyzed in relation to predefined criteria for recurrent SH or asymptomatic change. Sample size calculations for hypothesized therapeutic effects were conducted. RESULTS: We logged 143 QSM and 130 DCEQP paired annual assessments. Annual QSM change was greater in cases with SH than in cases without SH (P=0.019). Annual QSM increase by ≥6% occurred in 7 of 7 cases (100%) with recurrent SH and in 7 of 10 cases (70%) with asymptomatic change during the same epoch and 3.82× more frequently than clinical events. DCEQP change had lower sensitivity for SH and asymptomatic change than QSM change and greater variance. A trial with the smallest sample size would detect a 30% difference in QSM annual change during 2 years of follow-up in 34 or 42 subjects (1 and 2 tailed, respectively); power, 0.8, α=0.05. CONCLUSIONS: Assessment of QSM change is feasible and sensitive to recurrent bleeding in cavernous malformations. Evaluation of an intervention on QSM percent change may be used as a time-averaged difference between 2 arms using a repeated measures analysis. DCEQP change is associated with lesser sensitivity and higher variability than QSM. These results are the basis of an application for certification by the US Food and Drug Administration of QSM as a biomarker of drug effect on bleeding in cavernous malformations. REGISTRATION: URL: https://www.clinicaltrials.gov; Unique identifier: NCT03652181.

Baseline Characteristics of Patients With Cavernous Angiomas With Symptomatic Hemorrhage in Multisite Trial Readiness Project.

BACKGROUND AND PURPOSE: Brain cavernous angiomas with symptomatic hemorrhage (CASH) have a high risk of neurological disability from recurrent bleeding. Systematic assessment of baseline features and multisite validation of novel magnetic resonance imaging biomarkers are needed to optimize clinical trial design aimed at novel pharmacotherapies in CASH. METHODS: This prospective, multicenter, observational cohort study included adults with unresected, adjudicated brain CASH within the prior year. Six US sites screened and enrolled patients starting August 2018. Baseline demographics, clinical and imaging features, functional status (modified Rankin Scale and National Institutes of Health Stroke Scale), and patient quality of life outcomes (Patient-Reported Outcomes Measurement Information System-29 and EuroQol-5D) were summarized using descriptive statistics. Patient-Reported Outcomes Measurement Information System-29 scores were standardized against a reference population (mean 50, SD 10), and one-sample t test was performed for each domain. A subgroup underwent harmonized magnetic resonance imaging assessment of lesional iron content with quantitative susceptibility mapping and vascular permeability with dynamic contrast-enhanced quantitative perfusion. RESULTS: As of May 2020, 849 patients were screened and 110 CASH cases enrolled (13% prevalence of trial eligible cases). The average age at consent was 46±16 years, 53% were female, 41% were familial, and 43% were brainstem lesions. At enrollment, ≥90% of the cohort had independent functional outcome (modified Rankin Scale score ≤2 and National Institutes of Health Stroke Scale score <5). However, perceived health problems affecting quality of life were reported in >30% of patients (EuroQol-5D). Patients had significantly worse Patient-Reported Outcomes Measurement Information System-29 scores for anxiety (P=0.007), but better depression (P=0.002) and social satisfaction scores (P=0.012) compared with the general reference population. Mean baseline quantitative susceptibility mapping and permeability of CASH lesion were 0.45±0.17 ppm and 0.39±0.31 mL/100 g per minute, respectively, which were similar to historical CASH cases and consistent across sites. CONCLUSIONS: These baseline features will aid investigators in patient stratification and determining the most appropriate outcome measures for clinical trials of emerging pharmacotherapies in CASH.

Facial Feminization Surgery: Key CT Findings for Preoperative Planning and Postoperative Evaluation.

Facial feminization surgery is an increasingly performed component of gender affirmation surgery for transgender women. Preoperative facial CT is performed to plan the adjustment of the patient's masculine characteristics to feminine and to plan operative navigation around specific readily identifiable anatomic structures. In the upper face, surgery is performed to reduce the prominence of the brow and increase the nasofrontal angle; the radiology report should indicate the frontal sinus and supraorbital foramen anatomy. In the midface, rhinoplasty is performed to increase the nasofrontal and nasolabial angles; the radiology report should indicate the presence of a dorsal hump and septal deviation or spurring. In the lower face, the prominence of the chin and squareness of the jaw are adjusted via genioplasty and mandible contouring, respectively; the radiology report should describe the location and potential anatomic variations of the inferior alveolar nerve and mental foramina as well as the presence of dental abnormalities that directly inform the surgical approach. CT may also be performed if there is clinical suspicion for postoperative complications such as hardware fracture or osteotomy through the supraorbital or mental foramen. Familiarity with these findings will facilitate improved communication between radiologists and surgeons, thereby contributing to the care of transgender women.

Development and web deployment of an automated neuroradiology MRI protocoling tool with natural language processing.

BACKGROUND: A systematic approach to MRI protocol assignment is essential for the efficient delivery of safe patient care. Advances in natural language processing (NLP) allow for the development of accurate automated protocol assignment. We aim to develop, evaluate, and deploy an NLP model that automates protocol assignment, given the clinician indication text. METHODS: We collected 7139 spine MRI protocols (routine or contrast) and 990 head MRI protocols (routine brain, contrast brain, or other) from a single institution. Protocols were split into training (n = 4997 for spine MRI; n = 839 for head MRI), validation (n = 1071 for spine MRI, fivefold cross-validation used for head MRI), and test (n = 1071 for spine MRI; n = 151 for head MRI) sets. fastText and XGBoost were used to develop 2 NLP models to classify spine and head MRI protocols, respectively. A Flask-based web app was developed to be deployed via Heroku. RESULTS: The spine MRI model had an accuracy of 83.38% and a receiver operator characteristic area under the curve (ROC-AUC) of 0.8873. The head MRI model had an accuracy of 85.43% with a routine brain protocol ROC-AUC of 0.9463 and contrast brain protocol ROC-AUC of 0.9284. Cancer, infectious, and inflammatory related keywords were associated with contrast administration. Structural anatomic abnormalities and stroke/altered mental status were indicative of routine spine and brain MRI, respectively. Error analysis revealed increasing the sample size may improve performance for head MRI protocols. A web version of the model is provided for demonstration and deployment. CONCLUSION: We developed and web-deployed two NLP models that accurately predict spine and head MRI protocol assignment, which could improve radiology workflow efficiency.

Using neuronal extracellular vesicles and machine learning to predict cognitive deficits in HIV.

Our objective was to predict HIV-associated neurocognitive disorder (HAND) in HIV-infected people using plasma neuronal extracellular vesicle (nEV) proteins, clinical data, and machine learning. We obtained 60 plasma samples from 38 women and 22 men, all with HIV infection and 40 with HAND. All underwent neuropsychological testing. nEVs were isolated by immunoadsorption with neuron-specific L1CAM antibody. High-mobility group box 1 (HMGB1), neurofilament light (NFL), and phosphorylated tau-181 (p-T181-tau) proteins were quantified by ELISA. Three different computational algorithms were performed to predict cognitive impairment using clinical data and nEV proteins. Of the 3 different algorithms, support vector machines performed the best. Applying 4 different models of clinical data with 3 nEV proteins, we showed that selected clinical data and HMGB1 plus NFL best predicted cognitive impairment with an area under the curve value of 0.82. The most important features included CD4 count, HMGB1, and NFL. Previous published data showed nEV p-T181-tau was elevated in Alzheimer's disease (AD), and in this study, p-T181-tau had no importance in assessing HAND but may actually differentiate it from AD. Machine learning can access data without programming bias. Identifying a few nEV proteins plus key clinical variables can better predict neuronal damage. This approach may differentiate other neurodegenerative diseases and determine recovery after therapies are identified.

The regional pattern of abnormal cerebrovascular reactivity in HIV-infected, virally suppressed women.

The purpose of this study was to assess whole brain and regional patterns of cerebrovascular reactivity (CVR) abnormalities in HIV-infected women using quantitative whole brain arterial spin labeling (ASL). We hypothesized that HIV-infected women would demonstrate decreased regional brain CVR despite viral suppression. This cross-sectional study recruited subjects from the Bay Area Women's Interagency Health Study (WIHS)-a cohort study designed to investigate the progression of HIV disease in women. In addition to conventional noncontrast cerebral MRI sequences, perfusion imaging was performed before and after the administration of intravenous acetazolamide. CVR was measured by comparing quantitative ASL brain perfusion before and after administration of intravenous acetazolamide. In order to validate and corroborate ASL-based whole brain and regional perfusion, phase-contrast (PC) imaging was also performed through the major neck vessels. FLAIR and susceptibility weighted sequences were performed to assess for white matter injury and microbleeds, respectively. Ten HIV-infected women and seven uninfected, age-matched controls were evaluated. Significant group differences were present in whole brain and regional CVR between HIV-infected and uninfected women. These regional differences were significant in the frontal lobe and basal ganglia. CVR measurements were not significantly impacted by the degree of white matter signal abnormality or presence of microbleeds. Despite complete viral suppression, dysfunction of the neurovascular unit persists in the HIV population. Given the lack of association between CVR and traditional imaging markers of small vessel disease, CVR quantification may provide an early biomarker of pre-morbid vascular disease.

Facial Feminization Surgery: Key CT Findings for Preoperative Planning and Postoperative Evaluation.

Facial feminization surgery (FFS) is an increasingly performed component of gender affirmation surgery for transgender women. Preoperative facial CT is performed to plan the adjustment of the patient's masculine characteristics to feminine, and to plan operative navigation around specific readily identifiable anatomic structures. In the upper face, surgery is performed to reduce the prominence of the brow and increase the nasofrontal angle; the radiology report should indicate the frontal sinus and supraorbital foramen anatomy. In the midface, rhinoplasty is performed to increase the nasofrontal and nasolabial angles; the radiology report should indicate presence of a dorsal hump and septal deviation or spurring. In the lower face, prominence of the chin and squareness of the jaw are adjusted via genioplasty and mandible contouring, respectively; the radiology report should describe the location and potential anatomic variations of the inferior alveolar nerve and mental foramina, as well as presence of dental abnormalities that directly inform the surgical approach. CT may also be performed if there is clinical suspicion for postoperative complications such as hardware fraction or osteotomy through the supraorbital or mental foramen. Familiarity with these findings will facilitate improved communication between radiologists and surgeons, thereby contributing to the care of transgender women.

Between Always and Never: Evaluating Uncertainty in Radiology Reports Using Natural Language Processing.

The ideal radiology report reduces diagnostic uncertainty, while avoiding ambiguity whenever possible. The purpose of this study was to characterize the use of uncertainty terms in radiology reports at a single institution and compare the use of these terms across imaging modalities, anatomic sections, patient characteristics, and radiologist characteristics. We hypothesized that there would be variability among radiologists and between subspecialities within radiology regarding the use of uncertainty terms and that the length of the impression of a report would be a predictor of use of uncertainty terms. Finally, we hypothesized that use of uncertainty terms would often be interpreted by human readers as "hedging." To test these hypotheses, we applied a natural language processing (NLP) algorithm to assess and count the number of uncertainty terms within radiology reports. An algorithm was created to detect usage of a published set of uncertainty terms. All 642,569 radiology report impressions from 171 reporting radiologists were collected from 2011 through 2015. For validation, two radiologists without knowledge of the software algorithm reviewed report impressions and were asked to determine whether the report was "uncertain" or "hedging." The relationship between the presence of 1 or more uncertainty terms and the human readers' assessment was compared. There were significant differences in the proportion of reports containing uncertainty terms across patient admission status and across anatomic imaging subsections. Reports with uncertainty were significantly longer than those without, although report length was not significantly different between subspecialities or modalities. There were no significant differences in rates of uncertainty when comparing the experience of the attending radiologist. When compared with reader 1 as a gold standard, accuracy was 0.91, sensitivity was 0.92, specificity was 0.9, and precision was 0.88, with an F1-score of 0.9. When compared with reader 2, accuracy was 0.84, sensitivity was 0.88, specificity was 0.82, and precision was 0.68, with an F1-score of 0.77. Substantial variability exists among radiologists and subspecialities regarding the use of uncertainty terms, and this variability cannot be explained by years of radiologist experience or differences in proportions of specific modalities. Furthermore, detection of uncertainty terms demonstrates good test characteristics for predicting human readers' assessment of uncertainty.

Comparison of Deep Brain Stimulation Lead Targeting Accuracy and Procedure Duration between 1.5- and 3-Tesla Interventional Magnetic Resonance Imaging Systems: An Initial 12-Month Experience.

BACKGROUND: Interventional magnetic resonance imaging (iMRI) allows deep brain stimulator lead placement under general anesthesia. While the accuracy of lead targeting has been described for iMRI systems utilizing 1.5-tesla magnets, a similar assessment of 3-tesla iMRI procedures has not been performed. OBJECTIVE: To compare targeting accuracy, the number of lead targeting attempts, and surgical duration between procedures performed on 1.5- and 3-tesla iMRI systems. METHODS: Radial targeting error, the number of targeting attempts, and procedure duration were compared between surgeries performed on 1.5- and 3-tesla iMRI systems (SmartFrame and ClearPoint systems). RESULTS: During the first year of operation of each system, 26 consecutive leads were implanted using the 1.5-tesla system, and 23 consecutive leads were implanted using the 3-tesla system. There was no significant difference in radial error (Mann-Whitney test, p = 0.26), number of lead placements that required multiple targeting attempts (Fisher's exact test, p = 0.59), or bilateral procedure durations between surgeries performed with the two systems (p = 0.15). CONCLUSIONS: Accurate DBS lead targeting can be achieved with iMRI systems utilizing either 1.5- or 3-tesla magnets. The use of a 3-tesla magnet, however, offers improved visualization of the target structures and allows comparable accuracy and efficiency of placement at the selected targets.

Classification of traumatic injury to the dural venous sinus using CT venography.

BACKGROUND AND PURPOSE: Cerebral venous sinus thrombosis (CVST) is an underrecognized cause of morbidity in acute traumatic brain injury (TBI). Radiologic diagnosis is challenging in the setting of concurrent extra-axial injury and a lack of standardized diagnostic criteria. The prevalence of traumatic thrombosis versus compression is unknown. Treatment with anticoagulation is often determined by the appropriate classification of the type of traumatic venous injury. METHODS: We developed a two-part radiologic grading method for standardized assessment of traumatic CVST based on (1) the degree of flow limitation through the affected sinus and (2) the location of venous pathology (ie, external compression vs. intrinsic thrombosis) based on computed tomography venography. We applied this grading method to a retrospective cohort of TBI patients presenting to a Level 1 Trauma center. Chart review was performed to identify potential clinical correlates. A senior neuroradiologist graded the entire cohort and a random subsample was selected for blinded rating by two independent neuroradiologists. RESULTS: Seventy-six of 221 patients were identified for inclusion after excluding nontraumatic mechanisms. Seven unique grades were employed to characterize the full extent of venous injuries. The plurality of patients from the cohort (43/76 = 43.4%) suffered compressive injuries. Inter-rater reliability was moderate for the combined grade, kappa = 0.48, p<.05, and substantial for the flow limitation component, kappa = 0.69, p<.05. CONCLUSIONS: We introduce a standardized two-part classification system for traumatic venous sinus injury with moderate-substantial inter-rater reliability. Compressive injuries were more common than thrombotic injuries. Further prospective work is needed to validate the clinical significance of this classification system.

A feasibility study for quantitative assessment of cerebrovascular malformations using flutriciclamide ([18F]GE-180) PET/MRI.

Aim: Neuroinflammation plays a key role in both the pathogenesis and the progression of cerebral cavernous malformations (CCM). Flutriciclamide ([18F]GE-180) is a translocator protein (TSPO) targeting positron emission tomography (PET) tracer, developed for imaging neuroinflammation. The objectives of this study were to describe characteristics of flutriciclamide uptake in different brain tissue regions in CCM patients compared to controls, and to evaluate flutriciclamide uptake and iron deposition within CCM lesions. Materials and methods: Five patients with CCM and six controls underwent a 60 or 90 min continuous PET/MRI scan following 315 ± 68.9 MBq flutriciclamide administration. Standardized uptake value (SUV) and standardized uptake value ratio (SUVr) were obtained using the striatum as a pseudo-reference. Quantitative susceptibility maps (QSM) were used to define the location of the vascular malformation and calculate the amount of iron deposition in each lesion. Results: Increased flutriciclamide uptake was observed in all CCM lesions. The temporal pole demonstrated the highest radiotracer uptake; the paracentral lobule, cuneus and hippocampus exhibited moderate uptake; while the striatum had the lowest uptake, with average SUVs of 0.66, 0.55, 0.63, 0.55, and 0.33 for patient with CCM and 0.57, 0.50, 0.48, 0.42, and 0.32 for controls, respectively. Regional SUVr showed similar trends. The average SUV and QSM values in CCM lesions were 0.58 ± 0.23 g/ml and 0.30 ± 0.10 ppm. SUVs and QSM were positively correlated in CCM lesions (r = 0.53, p = 0.03). Conclusion: The distribution of flutriciclamide ([18F]GE-180) in the human brain and CCM lesions demonstrated the potential of this TSPO PET tracer as a marker of neuroinflammation that may be relevant for characterizing CCM disease progression along with QSM.

Cavernous Angioma Symptomatic Hemorrhage (CASH) Trial Readiness II: Imaging Biomarkers and Trial Modeling.

Background: Quantitative susceptibility mapping (QSM) and dynamic contrast enhanced quantitative perfusion (DCEQP) MRI sequences assessing iron deposition and vascular permeability were previously correlated with new hemorrhage in cavernous angiomas. We assessed their prospective changes in cavernous angiomas with symptomatic hemorrhage (CASH) in a multisite trial readiness project ( clinicaltrials.gov NCT03652181 ). Methods: Patients with CASH in the prior year, without prior or planned lesion resection or irradiation were enrolled. Mean QSM and DCEQP of CASH lesion were acquired at baseline, and at 1- and 2-year follow-ups. Sensitivity and specificity of biomarker changes were analyzed in relation to predefined lesional symptomatic hemorrhage (SH) or asymptomatic change (AC). Sample size calculations for hypothesized therapeutic effects were conducted. Results: We logged 143 QSM and 130 DCEQP paired annual assessments. Annual QSM change was greater in cases with SH than in cases without SH (p= 0.019). Annual QSM increase by ≥ 6% occurred in 7 of 7 cases (100%) with recurrent SH and in 7 of 10 cases (70%) with AC during the same epoch, and 3.82 times more frequently than clinical events. DCEQP change had lower sensitivity for SH and AC than QSM change, and greater variance. A trial with smallest sample size would detect a 30% difference in QSM annual change in 34 or 42 subjects (one and two-tailed, respectively), power 0.8, alpha 0.05. Conclusions: Assessment of QSM change is feasible and sensitive to recurrent bleeding in CASH. Evaluation of an intervention on QSM percent change may be used as a time-averaged difference between 2 arms using a repeated measures analysis. DCEQP change is associated with lesser sensitivity and higher variability than QSM. These results are the basis of an application for certification by the U.S. F.D.A. of QSM as a biomarker of drug effect in CASH.

Intracranial vascular imaging detects arterial wall abnormalities in persons with treated HIV infection.

OBJECTIVE: Although a substantial proportion of ischemic strokes in persons with HIV infection (PWH) is related to large artery disease, studies evaluating elevated cerebrovascular risk in PWH have focused primarily on microvascular disease. We compared the burden of intracranial large artery disease on vessel wall MRI (VW-MRI) in PWH and HIV-uninfected individuals. DESIGN: Cross-sectional study. METHODS: We recruited antiretroviral therapy-treated PWH with undetectable plasma viral load and HIV-uninfected individuals. All participants were at least 40 years of age and at moderate-to-high cardiovascular risk. We used Poisson and mixed effects logistic regression models to compare the number and associated characteristics of enhancing intracranial arteries on VW-MRI by HIV status. RESULTS: Of 46 participants (mean age 59 years), 33 were PWH. PWH had nearly four-fold as many enhancing intracranial arteries on VW-MRI than HIV-uninfected individuals (rate ratio 3.94, 95% CI 1.57-9.88, P = 0.003). The majority of wall enhancement was eccentric (76%) and short-segment (93%), suggestive of intracranial atherosclerotic disease (ICAD). Sixty-nine percent of enhancing arteries were not associated with luminal narrowing on magnetic resonance angiography (MRA). None of these characteristics differed significantly by HIV status. CONCLUSION: In persons at moderate-to-high cardiovascular risk, HIV infection, even when well controlled, may be associated with a greater burden of intracranial large artery disease and, specifically, of ICAD. Studies of the mechanisms underlying higher rates of ischemic stroke in PWH should include evaluation for intracranial large artery disease. VW-MRI provides added value as an adjunct to traditional luminal imaging when evaluating cerebrovascular risk in PWH.

Neurovascular disease, diagnosis, and therapy: Cervical and intracranial atherosclerosis, vasculitis, and vasculopathy.

Stroke is a leading cause of death, disability, and financial burden in the United States. Perhaps more than any other disease process, the rapidity with which the diagnosis and treatment of stroke are successfully achieved is paramount to the reduction of its associated morbidity and mortality. Steno-occlusive intracranial vascular disease, the most notorious culprit of cerebral ischemia and/or hemorrhage, traces its etiology to native and embolic atherosclerosis as well as various forms of vascular inflammation, insult, and dysfunction. Distinguishing between these causes is a critical first step in the diagnosis and treatment of a patient presenting with cerebrovascular compromise. In this chapter, we delineate the clinical and imaging features of cervical and intracranial atherosclerosis, vasculitis, and vasculopathy, along with the evidence behind the treatments which comprise their current-day standard of care. The modern imaging armamentarium is diverse and complex, with contrast-enhanced and non-contrast MR angiography, CT angiography, digital subtraction angiography, and ultrasound; each playing an important role in providing rapid insight into the patient's disease process. Understanding these imaging techniques and their application in the acute setting is critical for the provider caring for stroke patients.

The Effect of Extracranial-to-Intracranial Bypass on Cerebral Vasoreactivity: A 4D Flow MRI Pilot Study.

BACKGROUND AND PURPOSE: Extracranial-to-intracranial (EC-IC) surgical bypass improves cerebral blood flow (CBF) and cerebrovascular vasoreactivity (CVR) for patients with carotid occlusion. Bypass graft patency and contribution of the graft to the postoperative increase in CVR are challenging to assess. To assess the effectiveness of 4D flow magnetic resonance imaging (MRI) to evaluate bypass graft patency and flow augmentation through the superficial temporal artery (STA) before and after EC-IC bypass. METHODS: Three consecutive patients undergoing EC-IC bypass for carotid occlusion were evaluated pre- and postoperatively using CVR testing with pre- and poststimulus 4D flow-MRI for assessment of the bypass graft and intracranial vasculature. RESULTS: Preoperatively, 2 patients (patients 1 and 3) did not augment flow through either native STA. The third, who had evidence of extensive native EC-IC collateralization on digital subtraction angiography (DSA), did augment flow through the STA preoperatively (CVR = 1). Postoperatively, all patients demonstrated CVR > 1 on the side of bypass. The patient who had CVR > 1 preoperatively demonstrated the greatest increase in resting postoperative graft flow (from 40 to 130 mL/minute), but the smallest CVR, with a poststimulus graft flow of 160 mL/minute (CVR = 1.2). The 2 patients who did not demonstrate augmentation of graft flow preoperatively augmented postoperatively from 10 to 20 mL/minute (CVR = 2.0) and 10-80 mL/minute (CVR = 8.0), respectively. Intracranial flow was simultaneously interrogated. Two patients demonstrated mild reductions in resting flow velocities in all interrogated vessels immediately following bypass. The patient who underwent CVR testing on postoperative day 48 demonstrated a stable or increased flow rate in most intracranial vessels. CONCLUSION: Four-dimensional flow MRI allows for noninvasive, simultaneous interrogation of the intra- and extracranial arterial vasculature during CVR testing, and reveals unique paradigms in cerebrovascular physiology. Observing these flow patterns may aid in improved patient selection and more detailed postoperative evaluation for patients undergoing EC-IC bypass.

"Looks familiar, but I do not know who she is": The role of the anterior right temporal lobe in famous face recognition.

Processing a famous face involves a cascade of steps including detecting the presence of a face, recognizing it as familiar, accessing semantic/biographical information about the person, and finally, if required, production of the proper name. Decades of neuropsychological and neuroimaging studies have identified a network of occipital and temporal brain regions ostensibly comprising the 'core' system for face processing. Recent research has also begun to elucidate upon an 'extended' network, including anterior temporal and frontal regions. However, there is disagreement about which brain areas are involved in each step, as many aspects of face processing occur automatically in healthy individuals and rarely dissociate in patients. Moreover, some common phenomena are not easily induced in an experimental setting, such as having a sense of familiarity without being able to recall who the person is. Patients with the semantic variant of Primary Progressive Aphasia (svPPA) often recognize a famous face as familiar, even when they cannot specifically recall the proper name or biographical details. In this study, we analyzed data from a large sample of 105 patients with neurodegenerative disorders, including 43 svPPA, to identify the neuroanatomical substrates of three different steps of famous face processing. Using voxel-based morphometry, we correlated whole-brain grey matter volumes with scores on three experimental tasks that targeted familiarity judgment, semantic/biographical information retrieval, and naming. Performance in naming and semantic association significantly correlates with grey matter volume in the left anterior temporal lobe, whereas familiarity judgment with integrity of the right anterior middle temporal gyrus. These findings shed light on the neuroanatomical substrates of key components of overt face processing, addressing issues of functional lateralization, and deepening our understanding of neural substrates of semantic knowledge.

The Role of Circle of Willis Anatomy Variations in Cardio-embolic Stroke: A Patient-Specific Simulation Based Study.

We describe a patient-specific simulation based investigation on the role of Circle of Willis anatomy in cardioembolic stroke. Our simulation framework consists of medical image-driven modeling of patient anatomy including the Circle, 3D blood flow simulation through patient vasculature, embolus transport modeling using a discrete particle dynamics technique, and a sampling based approach to incorporate parametric variations. A total of 24 (four patients and six Circle anatomies including the complete Circle) models were considered, with cardiogenic emboli of varying sizes and compositions released virtually and tracked to compute distribution to the brain. The results establish that Circle anatomical variations significantly influence embolus distribution to the six major cerebral arteries. Embolus distribution to MCA territory is found to be least sensitive to the influence of anatomical variations. For varying Circle topologies, differences in flow through cervical vasculature are observed. This incoming flow is recruited differently across the communicating arteries of the Circle for varying anastomoses. Emboli interact with the routed flow, and can undergo significant traversal across the Circle arterial segments, depending upon their inertia and density ratio with respect to blood. This interaction drives the underlying biomechanics of embolus transport across the Circle, explaining how Circle anatomy influences embolism risk.

Brain MRI Features of CSF Human Immunodeficiency Virus Escape.

BACKGROUND AND PURPOSE: HIV infection of the central nervous system (CNS) is a nearly universal feature of untreated systemic HIV infection. While combination antiretroviral therapy (ART) that suppresses systemic infection usually suppresses CNS (CNS) HIV infection, exceptions have been reported with discordance between CSF and blood HIV RNA concentrations such that CSF demonstrates higher HIV concentrations than blood, referred to as CSF HIV escape. Rarely, CSF HIV escape presents with neurological symptoms, called neurosymptomatic escape. METHODS: In this report, we describe the MRI findings in 6 patients with neurosymptomatic escape who were identified at our institution. RESULTS: MR imaging suggests an encephalitis possibly evolving from a distinct HIV subpopulation within the CNS. A major difference between primary HIV infection and the current case series is that untreated HIV encephalitis usually occurs in the setting of late disease and a low CD4 whereas CSF Escape develops in setting of a higher CD4, as well as more robust immune and inflammatory responses. Our findings show a burden and distribution of white matter signal abnormalities atypical for patients adherent to ART and that differs from that seen in untreated HIV encephalitis and leukoencephalopathy. Moreover, these patients may also demonstrate perivascular enhancement, a finding not previously reported in the CSF HIV escape literature. CONCLUSION: Recognition of these imaging characteristics-patchy subcortical white matter intensities and a perivascular pattern of enhancement-may be helpful in recognition and, along with other clinical information and CSF findings, in diagnosis of neurosymptomatic escape.

Diagnostic Performance of Brain MRI in Immune Reconstitution Inflammatory Syndrome.

BACKGROUND AND PURPOSE: Central nervous system immune reconstitution inflammatory syndrome (CNS-IRIS) significantly negatively impacts the human immunodeficiency virus (HIV)-infected population on combination antiretroviral therapy (cART). We sought to determine the diagnostic performance of several magnetic resonance imaging (MRI) features for CNS-IRIS in a cohort of HIV+ patients recently started on cART. METHODS: Our radiologic database was searched from January 2003 to September 2014 retrospectively for patients diagnosed with HIV and worsening symptoms on cART. A total of 20 patients with HIV were identified; patients were classified as having CNS-IRIS on the basis of established clinical criteria (8 patients; 12 age- and sex-matched controls). Brain MR images were obtained at a single post-cART timepoint during hospitalization for acute neurologic deterioration and blindly interpreted by two experienced neuroradiologists for the presence of four variables: intrinsic T1 hyperintensity, marginal reduced diffusion, and marginal enhancement or perivascular enhancement. RESULTS: Although each individual finding showed moderate predictive accuracy, the combination of MR findings demonstrated good test characteristics: sensitivity 88% (confidence interval [CI] 62-98), specificity 79% (58-93), positive predictive value 71% (44-90%), and negative predictive value 83% (CI 52-98%). In addition, this final diagnosis demonstrated good predictive accuracy, area under curve .78 (CI .63-.91), and moderate inter-reader agreement, κ = .55. CONCLUSIONS: Our findings suggest that although each individual MR finding shows only moderate diagnostic performance, the combined assessment of experienced neuroradiologists has good predictive accuracy. The absence of any described MRI findings makes the diagnosis of CNS-IRIS highly unlikely.