Stroke Magnetic Resonance Imaging Is Accurate in Hyperacute Intracerebral Hemorrhage

Imaging of Ischemic Stroke

PURPOSE OF REVIEW

This article provides an overview of cerebrovascular hemodynamics, acute stroke pathophysiology, and collateral circulation, which are pivotal in the modern imaging of ischemic stroke that guides the care of the patient with stroke.

RECENT FINDINGS

Neuroimaging provides extensive information on the brain and vascular health. Multimodal CT and MRI delineate the hemodynamics of ischemic stroke that may be used to guide treatment decisions and prognosticate regarding expected outcomes. Mismatch imaging with either CT or MRI may identify patients with salvageable regions who are at risk and likely to benefit from reperfusion therapy, even if they are outside the standard time window. Imaging of collateral circulation and determination of collateral grade may predict greater reperfusion, lower hemorrhage risk, and better functional outcome. Current neuroimaging technology also enables the identification of patients at high risk of hemorrhagic transformation or those who may be harmed by treatment or unlikely to benefit from it.

SUMMARY

This article reviews the use and impact of imaging for the patient with ischemic stroke, emphasizing how imaging builds upon clinical evaluation to establish diagnosis or etiology, reveal key pathophysiology, and guide therapeutic decisions.

Imaging and management of fetuses and neonates with alloimmune thrombocytopenia

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is the most common cause of severe neonatal thrombocytopenia and intracranial bleeding in term newborns. Intracranial hemorrhage (ICH) commonly results in death or severe, lasting neurologic disability. The timing of ICH is also important for management of the next affected pregnancy in cases of FNAIT. This manuscript reviews the advantages and disadvantages of the different radiologic methodologies to identify and characterize ICH. It discusses the limits of ultrasound and the advantages of magnetic resonance imaging allowing avoidance of the radiation associated with computed tomography (CT) scans.

Introduction of a Dedicated Emergency Department MR Imaging Scanner at the Barrow Neurological Institute

Use of advanced imaging in the emergency department has been increasing in the United States during the past 2 decades. This trend has been most notable in CT, which has increased concern over the effects of increasing levels of medical ionizing radiation. MR imaging offers a safe, nonionizing alternative to CT and is diagnostically superior in many neurologic conditions encountered in the emergency department. Herein, we describe the process of developing and installing a dedicated MR imaging scanner in the Neuroscience Emergency Department at the Barrow Neurological Institute and its effects on neuroradiology and the emergency department in general.

MR imaging in hyperacute ischemic stroke

Brain and vascular imaging are required components of the emergency assessment of patients with suspected stroke. Either CT or MRI may be used as the initial imaging test. MRI is more sensitive to the presence of acute and chronic ischemic lesions, and chronic microbleeds, but CT remains the most practical and used initial brain imaging test. Although, a non-enhanced CT or T2* MRI sequence showing no haemorrhage is sufficient for deciding intravenous treatment eligibility within the first 4.5h after stroke onset, a non-invasive intracranial vascular study is strongly recommended during the initial imaging evaluation of the acute stroke patient, particularly if mechanical thrombectomy is contemplated. Advanced imaging with multimodal MRI may facilitate accurate ischemic stroke diagnosis and characterization, and should be considered as an alternative to CT, especially for the selection of patients for acute reperfusion therapy in extended time windows, and in patients in which time of stroke onset is unknown. However, MRI should only be considered in the acute stroke workflow if centres are able to achieve speed and triaging efficiency similar to that which is currently available with CT-based imaging.

Diagnosis of DWI-negative acute ischemic stroke: A meta-analysis

OBJECTIVE

To determine the prevalence of diffusion-weighted imaging (DWI)-negative acute ischemic stroke (AIS) and to identify clinical characteristics of patients with DWI-negative AIS.

METHODS

We systematically searched PubMed and Ovid/MEDLINE for relevant studies between 1992, the year that the DWI sequence entered clinical practice, and 2016. Studies were included based upon enrollment of consecutive patients presenting with a clinical diagnosis of AIS prior to imaging. Meta-analysis was performed to synthesize study-level data, estimate DWI-negative stroke prevalence, and estimate the odds ratios (ORs) for clinical characteristics associated with DWI-negative stroke.

RESULTS

Twelve articles including 3,236 AIS patients were included. The meta-analytic synthesis yielded a pooled prevalence of DWI-negative AIS of 6.8%, 95% confidence interval (CI) 4.9-9.3. In the 5 studies that reported proportion data for DWI-negative and DWI-positive AIS based on the ischemic vascular territory (n = 1,023 AIS patients), DWI-negative stroke was strongly associated with posterior circulation ischemia, as determined by clinical diagnosis at hospital discharge or repeat imaging (OR 5.1, 95% CI 2.3-11.6, p < 0.001).

CONCLUSIONS

A small but significant percentage of patients with AIS have a negative DWI scan. Patients with neurologic deficits consistent with posterior circulation ischemia have 5 times the odds of having a negative DWI scan compared to patients with anterior circulation ischemia. AIS remains a clinical diagnosis and urgent reperfusion therapy should be considered even when an initial DWI scan is negative.

The impact of installing an MR scanner in the emergency department for patients presenting with acute stroke-like symptoms

PURPOSE

We examined the impact of an MR scanner in the emergency department (ED) on ED length of stay (LOS), hospital (H) LOS, hospital admission rate, hospitalization costs, and ED re-presentation rate of patients presenting with stroke-like symptoms (SLS). We hypothesized that the ED MR would increase efficiency of patient care.

METHODS

The number of MRIs performed in the ED vs. inpatient setting, EDLOS, HLOS, hospitalization charges, admission rate, discharge diagnoses, and 30-60-day ED re-presentation rates were determined for ED patients with SLS six months before (2011) and after (2012) ED MR installation.

RESULTS

362 and 448 patients with SLS presented to the ED, and 196 and 176 patients were admitted in 2011 and 2012 respectively. In 2011, 36 (18.4%) admitted patients, and, in 2012, 68 (38.6%) had MRIs in the ED, p<0.001. In 2011, 74 (37.8%) admitted patients were diagnosed with ischemic stroke, compared to 92 (52.3%) in 2012, p=0.007. HLOS was longer and charges higher for patients with stroke. No patients returned with a confirmed diagnosis of CVA or TIA within 0-60days after being discharged from the ED with negative MR.

CONCLUSIONS

With the ED MR, more admitted patients 1) got scanned in the ED and 2) were diagnosed with stroke. Because this led to more patients on the stroke service actually suffering from strokes (and not other diagnoses), the overall HLOS and charges of patients presenting with SLS were not reduced by ED MR screening. Discharge after a negative ED MR did not incur risk of TIAs or strokes over the ensuing 60days. Therefore, not only does a dedicated MR scanner in the ED aid in the acute diagnosis of a CVA or other neurologic disorder, but it does so without the risk of under-diagnosing TIAs or evolving strokes in the presence of a negative MRI.

Diffusion and Perfusion MR Imaging in Acute Stroke: Clinical Utility and Potential Limitations for Treatment Selection

Magnetic resonance (MR) diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI) offer unique insight into acute ischemic stroke pathophysiology. These techniques may offer the ability to apply pathophysiology to accurately individualize acute stroke reperfusion treatment, including extending the opportunity of reperfusion treatment to well beyond the current time-based treatment windows.This review examines the use of DWI and PWI in the major stroke trials, their current clinical utility, and potential limitations for reperfusion treatment selection. DWI and PWI continue to be investigated in ongoing randomized controlled trials, and continued research into these techniques will help achieve the goal of tissue-based decision making and individualized acute stroke treatment.

Spontaneous Intracerebral Hemorrhage: Management

Spontaneous non-traumatic intracerebral hemorrhage (ICH) remains a significant cause of mortality and morbidity throughout the world. To improve the devastating course of ICH, various clinical trials for medical and surgical interventions have been conducted in the last 10 years. Recent large-scale clinical trials have reported that early intensive blood pressure reduction can be a safe and feasible strategy for ICH, and have suggested a safe target range for systolic blood pressure. While new medical therapies associated with warfarin and non-vitamin K antagonist oral anticoagulants have been developed to treat ICH, recent trials have not been able to demonstrate the overall beneficial effects of surgical intervention on mortality and functional outcomes. However, some patients with ICH may benefit from surgical management in specific clinical contexts and/or at specific times. Furthermore, clinical trials for minimally invasive surgical evacuation methods are ongoing and may provide positive evidence. Upon understanding the current guidelines for the management of ICH, clinicians can administer appropriate treatment and attempt to improve the clinical outcome of ICH. The purpose of this review is to help in the decision-making of the medical and surgical management of ICH.

Management of intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is a potentially devastating neurologic injury representing 10-15% of stroke cases in the USA each year. Numerous risk factors, including age, hypertension, male gender, coagulopathy, genetic susceptibility, and ethnic descent, have been identified. Timely identification, workup, and management of this condition remain a challenge for clinicians as numerous factors can present obstacles to achieving good functional outcomes. Several large clinical trials have been conducted over the prior decade regarding medical and surgical interventions. However, no specific treatment has shown a major impact on clinical outcome. Current management guidelines do exist based on medical evidence and consensus and these provide a framework for care. While management of hypertension and coagulopathy are generally considered basic tenets of ICH management, a variety of measures for surgical hematoma evacuation, intracranial pressure control, and intraventricular hemorrhage can be further pursued in the emergent setting for selected patients. The complexity of management in parenchymal cerebral hemorrhage remains challenging and offers many areas for further investigation. A systematic approach to the background, pathology, and early management of spontaneous parenchymal hemorrhage is provided.

A Case of Traumatic Unilateral Internuclear Ophthalmoplegia: Clinical Significance of Susceptibility-Weighted Imaging

A 43-year-old man was admitted for head trauma after falling backward. The patient complained of diplopia. Unilateral internuclear ophthalmoplegia (INO) was diagnosed during the neurologic examination. Initially, no specific finding was shown on T2-weighted, T1-weighted, and fluid attenuated inversion recovery brain magnetic resonance image (MRI) or brain computed tomography (CT). However, susceptibility-weighted imaging (SWI) definitively demonstrated a tiny hemorrhage at the midline of the pontomesencephalic junction. The patient's symptom improved after 12 weeks. We discuss the clinical significance of SWI when traumatic INO due to a tiny hemorrhage is suspected.

Stroke mimic: Perfusion magnetic resonance imaging of a patient with ictal paralysis

We present an uncommon case of clinically diagnosed window period stroke subsequently recognised on diffusion - perfusion MRI as ictal paralysis due to focal inhibitory seizures or negative motor seizures. This case highlights the importance of MRI with perfusion imaging in establishing the diagnosis of stroke mimics and avoiding unnecessary thrombolysis.

Emergency Neurological Life Support: Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) is a subset of stroke due to bleeding within the parenchyma of the brain. It is potentially lethal, and survival depends on ensuring an adequate airway, reversal of coagulopathy, and proper diagnosis. ICH was chosen as an Emergency Neurological Life Support protocol because intervention within the first critical hour may improve outcome, and it is critical to have site-specific protocols to drive care quickly and efficiently.

Radiological imaging in acute ischaemic stroke

Patients who suffer acute ischaemic stroke can be treated with thrombolysis if therapy is initiated early. Radiological evaluation of the intracranial tissue before such therapy can be given is mandatory. In this review current radiological diagnostic strategies are discussed for this patient group. Beyond non-enhanced computed tomography (CT), the standard imaging method for many years, more sophisticated CT stroke protocols including CT angiography and CT perfusion have been developed, and additionally an increasing number of patients are examined with magnetic resonance imaging as the first imaging method used. Advantages and challenges of the different methods are discussed.

The H-ATOMIC Criteria for the Etiologic Classification of Patients with Intracerebral Hemorrhage

BACKGROUND AND PURPOSE

There are no generally accepted criteria for the etiologic classification of intracerebral hemorrhage (ICH). For this reason, we have developed a set of etiologic criteria and have applied them to a large number of patients to determine their utility.

METHODS

The H-ATOMIC classification includes 7 etiologic categories: Hypertension, cerebral Amyloid angiopathy, Tumour, Oral anticoagulants, vascular Malformation, Infrequent causes and Cryptogenic. For each category, the etiology is scored with three degrees of certainty: Possible(3), Probable(2) and Definite(1). Our aim was to perform a basic study consisting of neuroimaging, blood tests, and CT-angio when a numerical score (SICH) suggested an underlying structural abnormality. Combinations of >1 etiologic category for an individual patient were acceptable. The criteria were evaluated in a multicenter and prospective study of consecutive patients with spontaneous ICH.

RESULTS

Our study included 439 patients (age 70.8 ± 14.5 years; 61.3% were men). A definite etiology was achieved in 176 (40.1% of the patients: Hypertension 28.2%, cerebral Amyloid angiopathy 0.2%, Tumour 0.2%, Oral anticoagulants 2.2%, vascular Malformation 4.5%, Infrequent causes 4.5%). A total of 7 patients (1.6%) were cryptogenic. In the remaining 58.3% of the patients, ICH was attributable to a single (n = 56, 12.7%) or the combination of ≥2 (n = 200, 45.5%) possible/probable etiologies. The most frequent combinations of etiologies involved possible hypertension with possible CAA (H3A3, n = 38) or with probable CAA (H3A2, n = 29), and probable hypertension with probable OA (H2O2, n = 27). The most frequent category with any degree of certainty was hypertension (H1+2+3 = 80.6%) followed by cerebral amyloid angiopathy (A1+2+3 = 30.9%).

CONCLUSIONS

According to our etiologic criteria, only about 40% patients received a definite diagnosis, while in the remaining patients ICH was attributable to a single possible/probable etiology or to more than one possible/probable etiology. The use of these criteria would likely help in the management of patients with ICH.

[Competence Network Stroke. A successful model for stroke research]

In 1999 the German Ministry of Education and Research initiated a funding initiative for competence networks in health research in order to improve research and health care for major diseases with high morbidity and relevance to public health. All major players in a given field were invited to cooperate. The aims were to improve horizontal as well as vertical networking in order to improve research quality and the transfer of new results into general clinical practice. Another aim was to establish sustainable structures for lasting cooperation. After a highly competitive application round, the Competence Network Stroke was among the very first to be funded. The incidence of stroke in Germany is about 250,000 new patients per year, it is the leading cause of adult impairment and its societal impact is dramatic.This article describes how the Competence Network Stroke managed to meet the above-mentioned goals and how cooperation among stroke researchers and caregivers in Germany has improved. Furthermore it provides examples of researcher achievements in the network, which have advanced research and benefited patients.

Intracranial hemorrhage alters scalp potential distribution in bioimpedance cerebral monitoring: Preliminary results from FEM simulation on a realistic head model and human subjects

PURPOSE

Current diagnostic neuroimaging for detection of intracranial hemorrhage (ICH) is limited to fixed scanners requiring patient transport and extensive infrastructure support. ICH diagnosis would therefore benefit from a portable diagnostic technology, such as electrical bioimpedance (EBI). Through simulations and patient observation, the authors assessed the influence of unilateral ICH hematomas on quasisymmetric scalp potential distributions in order to establish the feasibility of EBI technology as a potential tool for early diagnosis.

METHODS

Finite element method (FEM) simulations and experimental left-right hemispheric scalp potential differences of healthy and damaged brains were compared with respect to the asymmetry caused by ICH lesions on quasisymmetric scalp potential distributions. In numerical simulations, this asymmetry was measured at 25 kHz and visualized on the scalp as the normalized potential difference between the healthy and ICH damaged models. Proof-of-concept simulations were extended in a pilot study of experimental scalp potential measurements recorded between 0 and 50 kHz with the authors' custom-made bioimpedance spectrometer. Mean left-right scalp potential differences recorded from the frontal, central, and parietal brain regions of ten healthy control and six patients suffering from acute/subacute ICH were compared. The observed differences were measured at the 5% level of significance using the two-sample Welch t-test.

RESULTS

The 3D-anatomically accurate FEM simulations showed that the normalized scalp potential difference between the damaged and healthy brain models is zero everywhere on the head surface, except in the vicinity of the lesion, where it can vary up to 5%. The authors' preliminary experimental results also confirmed that the left-right scalp potential difference in patients with ICH (e.g., 64 mV) is significantly larger than in healthy subjects (e.g., 20.8 mV; P < 0.05).

CONCLUSIONS

Realistic, proof-of-concept simulations confirmed that ICH affects quasisymmetric scalp potential distributions. Pilot clinical observations with the authors' custom-made bioimpedance spectrometer also showed higher left-right potential differences in the presence of ICH, similar to those of their simulations, that may help to distinguish healthy subjects from ICH patients. Although these pilot clinical observations are in agreement with the computer simulations, the small sample size of this study lacks statistical power to exclude the influence of other possible confounders such as age, sex, and electrode positioning. The agreement with previously published simulation-based and clinical results, however, suggests that EBI technology may be potentially useful for ICH detection.

Hemorrhagic Cerebellar Abscess

BACKGROUND

Brain abscess represents a significant medical problem, accounting for 1 in every 10,000 U.S. hospital admissions and imposing a mortality of 17%-32%. Treatment success depends on early diagnosis, allowing for prompt intervention before a potentially catastrophic rupture. However, diagnosis can be difficult because currently no magnetic resonance imaging signal characteristics are pathognomonic. The presence of hemorrhage may further complicate the radiographic detection of an abscess, potentially leading to delayed treatment.

CLINICAL PRESENTATION

A 71-year-old man was diagnosed with hemorrhagic cerebellar abscess as a complication of groin abscess after cardiac catheterization. After surgical resection of the cerebellar abscess and culture-based antibiotic treatment, the patient suffered repeat hemorrhages into the abscess cavity, of which he died. We describe his clinical course with emphasis on radiology-based differential diagnosis. We also describe the possible pathogenesis of this rare case, based on review of the literature.

CONCLUSIONS

To our knowledge, this is the first report on recurrent hemorrhages in a cerebellar abscess. Hemorrhagic brain abscess has a complex radiologic appearance, which may delay diagnosis and treatment. A high degree of clinical suspicion is necessary to ensure timely treatment of this potentially lethal lesion.

Diffusion tensor imaging and functional MRI

The advances in diffusion-weighted imaging (DWI), diffusion tensor imaging (DTI), and functional magnetic resonance imaging (fMRI) over the last 20 years have vastly contributed to improving the understanding of the brain structure and function in patients with many diseases of the central nervous system (CNS). DWI is commonly used, for instance, in the diagnostic workup of stroke, CNS neoplasia, and rapidly progressive dementia cases. The new DTI methods provide more specific information about the most destructive aspects of tumors, neurodegenerative dementia, and multiple sclerosis pathology and give a more complete picture of the complex pathologic mechanisms of these conditions. More recently, fMRI has provided insight to the mechanisms of brain adaptation and plasticity to damage related to many neurologic conditions and has further extended our ability to understand the functional significance of pathologic changes in these diseases. Although at present fMRI does not have a role in the diagnosis, routine assessment, and monitoring of neurologic diseases, significant efforts are under way in order to achieve harmonization of both acquisition and postprocessing procedures, which are likely to contribute to a significant change of the clinical scenario.

Spot Sign in Acute Intracerebral Hemorrhage in Dynamic T1-Weighted Magnetic Resonance Imaging

BACKGROUND AND PURPOSE

In computed tomographic imaging of acute intracerebral hemorrhage spot sign on computed tomographic angiography has been established as a marker for hematoma expansion and poor clinical outcome. Although, magnetic resonance imaging (MRI) can accurately visualize acute intracerebral hemorrhage, a corresponding MRI marker is lacking to date.

METHODS

We prospectively examined 50 consecutive patients with acute intracerebral hemorrhage within 24 hours of symptom onset. The MRI protocol consisted of a standard stroke protocol and dynamic contrast-enhanced T1-weighted imaging with a time resolution of 7.07 s/batch. Stroke scores were assessed at admission and at time of discharge. Volume measurements of hematoma size and spot sign were performed with MRIcron.

RESULTS

Contrast extravasation within sites of the hemorrhage (MRI spot sign) was seen in 46% of the patients. Patients with an MRI spot sign had a significantly shorter time to imaging than those without (P<0.001). The clinical outcome measured by the modified Rankin Scale was significantly worse in patients with spot sign compared with those without (P≤0.001). Hematoma expansion was observed in the spot sign group compared with the nonspot sign group, although the differences were not significant.

CONCLUSIONS

Spot sign can be detected using MRI on postcontrast T1-weighted and dynamic T1-weighted images. It is associated with worse clinical outcome. The time course of contrast extravasation in dynamic T1 images indicates that these spots represent ongoing bleeding.

Magnetic Resonance Imaging in Ischemic Stroke and Cerebral Venous Thrombosis

Imaging is indispensable in the evaluation of patients presenting with central nervous system emergencies. Although computed tomography (CT) is the mainstay of initial assessment and triage, magnetic resonance imaging (MRI) has become vital in expanding diagnostic capabilities, refining management strategies, and developing our understanding of disease processes. Ischemic stroke and cerebral venous thrombosis are 2 areas wherein MRI is actively revolutionizing patient care. Familiarity with the imaging manifestations of these 2 disease processes is crucial for any radiologist reading brain MR studies. In this review, the fundamentals of image interpretation will be addressed in-depth. Furthermore, advanced imaging techniques which are redefining the role of emergency MRI will be outlined, with a focus on the pathophysiological mechanisms that underlie image interpretation. In particular, emerging data surrounding the use of MR perfusion imaging in acute stroke management portend dramatic shifts in neurointerventional management. To this end, a review of the recent stroke literature will hopefully enhance the radiologist's role in both meaningful reporting and multidisciplinary teamwork.

Multimodal Diagnostic Imaging for Hyperacute Stroke

In April 2015, the American Roentgen Ray Society and the American Society of Neuroradiology cosponsored a unique program designed to evaluate the state of the art in the imaging work-up of acute stroke. This topic has grown in importance because of the recent randomized controlled trials demonstrating the clear efficacy of endovascular stroke treatment. The authors, who were participants in that symposium, will highlight the points of emphasis in this article.

Brain imaging in acute ischemic stroke—MRI or CT?

In acute stroke, imaging provides different technologies to demonstrate stroke subtype, tissue perfusion and vessel patency. In this review, we highlight recent clinical studies that are likely to guide therapeutic decisions. Clot length in computed tomography (CT) and clot burden in MR, imaging of leptomeningeal collaterals and indicators for active bleeding are illustrated. Imaging-based concepts for treatment of stroke at awakening and pre-hospital treatment in specialized ambulances offer new potentials to improve patient outcome.

Quantitative Susceptibility Mapping: Contrast Mechanisms and Clinical Applications

Quantitative susceptibility mapping (QSM) is a recently developed magnetic resonance imaging (MRI) technique for quantifying the spatial distribution of magnetic susceptibility within biological tissues. It first uses the frequency shift in the MRI signal to map the magnetic field profile within the tissue. The resulting field map is then used to determine the spatial distribution of the underlying magnetic susceptibility by solving an inverse problem. The solution is achieved by deconvolving the field map with a dipole field, under the assumption that the magnetic field results from a superposition of the dipole fields generated by all voxels and that each voxel has its own unique magnetic susceptibility. QSM provides an improved contrast-to-noise ratio for certain tissues and structures compared with its magnitude counterpart. More importantly, magnetic susceptibility directly reflects the molecular composition and cellular architecture of the tissue. Consequently, by quantifying magnetic susceptibility, QSM is becoming a quantitative imaging approach for characterizing normal and pathological tissue properties. This article reviews the mechanism that generates susceptibility contrast within tissues and some associated applications.

Diffusion-weighted signal patterns of intracranial haemorrhage

The signal pattern of intracranial haemorrhage on diffusion-weighted imaging (DWI) as it evolves over time is rarely discussed due to the sensitivity of T2*-weighted sequences and the specificity of classic signal patterns on T1 and T2-weighted sequences. The DWI signal is strongly affected by the magnetic susceptibility of paramagnetic blood products and, therefore, is markedly hypointense in the same phases that demonstrate hypointensity on T2*-weighted sequences; however, hyperacute haemorrhage (oxyhaemoglobin-predominant clot) and late subacute haemorrhage (extracellular methaemoglobin) do not demonstrate T2* hypointensity. Moreover, T2*-weighted sequences are less sensitive to the presence of extra-axial haemorrhage than to intraparenchymal haemorrhage. At these stages of evolution, haemorrhage demonstrates high DWI signal in association with low ADC values, which may be more pronounced than even its corresponding fluid-attenuated inversion recovery (FLAIR) signal. DWI is useful for identifying hyperacute subarachnoid haemorrhage and as a problem-solving tool in challenging cases.

How I treat and manage strokes in sickle cell disease

Neurologic complications are a major cause of morbidity and mortality in sickle cell disease (SCD). In children with sickle cell anemia, routine use of transcranial Doppler screening, coupled with regular blood transfusion therapy, has decreased the prevalence of overt stroke from ∼11% to 1%. Limited evidence is available to guide acute and chronic management of individuals with SCD and strokes. Current management strategies are based primarily on single arm clinical trials and observational studies, coupled with principles of neurology and hematology. Initial management of a focal neurologic deficit includes evaluation by a multidisciplinary team (a hematologist, neurologist, neuroradiologist, and transfusion medicine specialist); prompt neuro-imaging and an initial blood transfusion (simple followed immediately by an exchange transfusion or only exchange transfusion) is recommended if the hemoglobin is >4 gm/dL and <10 gm/dL. Standard therapy for secondary prevention of strokes and silent cerebral infarcts includes regular blood transfusion therapy and in selected cases, hematopoietic stem cell transplantation. A critical component of the medical care following an infarct is cognitive and physical rehabilitation. We will discuss our strategy of acute and long-term management of strokes in SCD.

Guidelines for the Management of Spontaneous Intracerebral Hemorrhage: A Guideline for Healthcare Professionals From the American Heart Association/American Stroke Association

PURPOSE

The aim of this guideline is to present current and comprehensive recommendations for the diagnosis and treatment of spontaneous intracerebral hemorrhage.

METHODS

A formal literature search of PubMed was performed through the end of August 2013. The writing committee met by teleconference to discuss narrative text and recommendations. Recommendations follow the American Heart Association/American Stroke Association methods of classifying the level of certainty of the treatment effect and the class of evidence. Prerelease review of the draft guideline was performed by 6 expert peer reviewers and by the members of the Stroke Council Scientific Oversight Committee and Stroke Council Leadership Committee.

RESULTS

Evidence-based guidelines are presented for the care of patients with acute intracerebral hemorrhage. Topics focused on diagnosis, management of coagulopathy and blood pressure, prevention and control of secondary brain injury and intracranial pressure, the role of surgery, outcome prediction, rehabilitation, secondary prevention, and future considerations. Results of new phase 3 trials were incorporated.

CONCLUSIONS

Intracerebral hemorrhage remains a serious condition for which early aggressive care is warranted. These guidelines provide a framework for goal-directed treatment of the patient with intracerebral hemorrhage.

Simultaneous detection and separation of hyperacute intracerebral hemorrhage and cerebral ischemia using amide proton transfer MRI

PURPOSE

To explore the capability of amide proton transfer (APT) imaging in the detection of hemorrhagic and ischemic strokes using preclinical rat models.

METHODS

The rat intracerebral hemorrhage (ICH) model (n = 10) was induced by injecting bacterial collagenase VII-S into the caudate nucleus, and the permanent ischemic stroke model (n = 10) was induced by using a 4-0 nylon suture to occlude the origin of the middle cerebral artery. APT-weighted (APTw) MRI was acquired on a 4.7T animal imager and quantified using the magnetization transfer-ratio asymmetry at 3.5 ppm from water.

RESULTS

There was a consistently high APTw MRI signal in hyperacute ICH during the initial 12 h after injection of collagenase compared with the contralateral brain tissue. When hemorrhagic and ischemic stroke were compared, hyperacute ICH and cerebral ischemia demonstrated opposite APTw MRI contrasts-namely, hyperintense versus hypointense compared with contralateral brain tissue, respectively. There was a stark contrast in APTw signal intensity between these two lesions.

CONCLUSION

APT-MRI could accurately detect hyperacute ICH and distinctly differentiate hyperacute ICH from cerebral ischemia, thus opening up the possibility of introducing to the clinic a single MRI scan for the simultaneous visualization and separation of hemorrhagic and ischemic strokes at the hyperacute stage. Magn Reson Med 74:42-50, 2015. © 2014 Wiley Periodicals, Inc.

Imaging Patterns and Management Algorithms in Acute Stroke: An Update for the Emergency Radiologist

Neuroimaging plays a key role in the initial work-up of patients with symptoms of acute stroke. Understanding the advantages and limitations of available CT and MR imaging techniques and how to use them optimally in the emergency setting is crucial for accurately making the diagnosis of acute stroke and for rapidly determining appropriate treatment.

Emergency and critical care management of acute ischaemic stroke

Ischaemic stroke is a devastating condition that is the leading cause of disability in the USA. Over the last 2 decades, the focus of management has shifted from secondary stroke prevention to acute treatment. Coordinated care starts in the field with the emergency medical service providers and continues in the ambulance and the emergency department through to the intensive care unit. After diagnosis and stabilization, a major goal is reperfusion therapy with intravenous fibrinolytics. Neuroimaging research is focused on improving patient selection, expanding treatment windows, and increasing the safety of therapeutic intervention. The role of adjunctive intra-arterial and mechanical thrombectomy remains undefined, and methods to improve reperfusion using sonolysis and new-generation fibrinolytics are currently investigational. Treatment in the intensive care unit targets prevention of secondary brain injury through optimization of blood pressure, cerebral perfusion, glucose, and temperature management, ventilation, and oxygenation. The most feared complications include malignant cerebral edema and symptomatic hemorrhagic transformation. Decompressive craniectomy is life saving, but questions regarding patient selection and timing remain. Hyperosmolar agents are currently used to mitigate cerebral edema, but newer agents to prevent the formation of cerebral edema at the molecular level are being studied. We outline a practical approach to current emergency and intensive care management based on consensus guidelines and the best available evidence.

Quantitative susceptibility mapping (QSM): Decoding MRI data for a tissue magnetic biomarker

In MRI, the main magnetic field polarizes the electron cloud of a molecule, generating a chemical shift for observer protons within the molecule and a magnetic susceptibility inhomogeneity field for observer protons outside the molecule. The number of water protons surrounding a molecule for detecting its magnetic susceptibility is vastly greater than the number of protons within the molecule for detecting its chemical shift. However, the study of tissue magnetic susceptibility has been hindered by poor molecular specificities of hitherto used methods based on MRI signal phase and T2* contrast, which depend convolutedly on surrounding susceptibility sources. Deconvolution of the MRI signal phase can determine tissue susceptibility but is challenged by the lack of MRI signal in the background and by the zeroes in the dipole kernel. Recently, physically meaningful regularizations, including the Bayesian approach, have been developed to enable accurate quantitative susceptibility mapping (QSM) for studying iron distribution, metabolic oxygen consumption, blood degradation, calcification, demyelination, and other pathophysiological susceptibility changes, as well as contrast agent biodistribution in MRI. This paper attempts to summarize the basic physical concepts and essential algorithmic steps in QSM, to describe clinical and technical issues under active development, and to provide references, codes, and testing data for readers interested in QSM.

An assessment of the cost-effectiveness of magnetic resonance, including diffusion-weighted imaging, in patients with transient ischaemic attack and minor stroke: a systematic review, meta-analysis and economic evaluation

BACKGROUND

Patients with transient ischaemic attack (TIA) or minor stroke need rapid treatment of risk factors to prevent recurrent stroke. ABCD2 score or magnetic resonance diffusion-weighted brain imaging (MR DWI) may help assessment and treatment.

OBJECTIVES

Is MR with DWI cost-effective in stroke prevention compared with computed tomography (CT) brain scanning in all patients, in specific subgroups or as 'one-stop' brain-carotid imaging? What is the current UK availability of services for stroke prevention?

DATA SOURCES

Published literature; stroke registries, audit and randomised clinical trials; national databases; survey of UK clinical and imaging services for stroke; expert opinion.

REVIEW METHODS

Systematic reviews and meta-analyses of published/unpublished data. Decision-analytic model of stroke prevention including on a 20-year time horizon including nine representative imaging scenarios.

RESULTS

The pooled recurrent stroke rate after TIA (53 studies, 30,558 patients) is 5.2% [95% confidence interval (CI) 3.9% to 5.9%] by 7 days, and 6.7% (5.2% to 8.7%) at 90 days. ABCD2 score does not identify patients with key stroke causes or identify mimics: 66% of specialist-diagnosed true TIAs and 35-41% of mimics had an ABCD2 score of ≥ 4; 20% of true TIAs with ABCD2 score of < 4 had key risk factors. MR DWI (45 studies, 9078 patients) showed an acute ischaemic lesion in 34.3% (95% CI 30.5% to 38.4%) of TIA, 69% of minor stroke patients, i.e. two-thirds of TIA patients are DWI negative. TIA mimics (16 studies, 14,542 patients) make up 40-45% of patients attending clinics. UK survey (45% response) showed most secondary prevention started prior to clinic, 85% of primary brain imaging was same-day CT; 51-54% of patients had MR, mostly additional to CT, on average 1 week later; 55% omitted blood-sensitive MR sequences. Compared with 'CT scan all patients' MR was more expensive and no more cost-effective, except for patients presenting at > 1 week after symptoms to diagnose haemorrhage; strategies that triaged patients with low ABCD2 scores for slow investigation or treated DWI-negative patients as non-TIA/minor stroke prevented fewer strokes and increased costs. 'One-stop' CT/MR angiographic-plus-brain imaging was not cost-effective.

LIMITATIONS

Data on sensitivity/specificity of MR in TIA/minor stroke, stroke costs, prognosis of TIA mimics and accuracy of ABCD2 score by non-specialists are sparse or absent; all analysis had substantial heterogeneity.

CONCLUSIONS

Magnetic resonance with DWI is not cost-effective for secondary stroke prevention. MR was most helpful in patients presenting at > 1 week after symptoms if blood-sensitive sequences were used. ABCD2 score is unlikely to facilitate patient triage by non-stroke specialists. Rapid specialist assessment, CT brain scanning and identification of serious underlying stroke causes is the most cost-effective stroke prevention strategy.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

A systemized stroke code significantly reduced time intervals for using intravenous tissue plasminogen activator under magnetic resonance imaging screening

BACKGROUND

A stroke code can shorten time intervals until intravenous tissue plasminogen activator (IV t-PA) treatment in acute ischemic stroke (AIS). Recently, several reports demonstrated that magnetic resonance imaging (MRI)-based thrombolysis had reduced complications and improved outcomes in AIS despite longer processing compared with computed tomography (CT)-based thrombolysis.

METHODS

In January 2009, we implemented CODE RED, a computerized stroke code, at our hospital with the aim of achieving rapid stroke assessment and treatment. We included patients with thrombolysis from January 2007 to December 2008 (prestroke code period) and from January 2009 to May 2013 (poststroke code period). The IV t-PA time intervals and 90-day modified Rankin Scale (mRS) scores were collected.

RESULTS

During the observation period, 252 patients used IV t-PA under the CODE RED (MRI based: 208; CT based: 44). The remaining 71 patients (MRI based: 53; CT based: 18) received it before the implementation of our stroke code. After implementation of CODE RED, door-to-image time, door-to-needle time, and the onset-to-needle time were significantly reduced by 11, 18, and 22 minutes in MRI-based thrombolysis. Particularly, the proportion of favorable outcome (mRS score 0-2) was significantly increased (from 41.5% to 60.1%, P = .02) in poststroke than in prestroke code period in MRI-based thrombolysis. However, in ordinal regression, the presence of stroke code showed just a trend for favorable outcome (odds ratio, .99-2.87; P = .059) at 90 days of using IV t-PA after correction of age, sex, and National Institutes of Health Stroke Scale.

CONCLUSIONS

In this study, we demonstrated that a systemized stroke code shortened time intervals for using IV t-PA under MRI screening. Also, our results showed a possibility that a systemized stroke code might enhance the efficacy of MRI-based thrombolysis. In the future, we need to carry out a more detailed prospective study about this notion.

The role of imaging in acute ischemic stroke

Neuroimaging has expanded beyond its traditional diagnostic role and become a critical tool in the evaluation and management of stroke. The objectives of imaging include prompt accurate diagnosis, treatment triage, prognosis prediction, and secondary preventative precautions. While capitalizing on the latest treatment options and expanding upon the "time is brain" doctrine, the ultimate goal of imaging is to maximize the number of treated patients and improve the outcome of one the most costly and morbid disease. A broad overview of comprehensive multimodal stroke imaging is presented here to affirm its utilization.

Diffusion-weighted imaging at b1000 for identifying intracerebral hemorrhage: preliminary sensitivity, specificity, and inter-rater variability

BACKGROUND

Noncontrast computed tomography (NCCT) is the gold standard to detect intracerebral hemorrhage (ICH) and ischemic stroke (IS) in patients presenting with acute focal syndromes. Diffusion-weighted magnetic resonance imaging (DW-MRI) obtained at b1000 is highly sensitive to identify acute IS but its sensitivity and specificity to detect ICH has not been systematically studied.

METHODS

Patients with a diagnosis of ICH on NCCT were prospectively enrolled and underwent DW-MRI at b1000. Patients with suspected ischemia and a negative NCCT served as controls. All diffusion-weighted imaging (DWI) scans were evaluated blindly by 4 experienced raters. Sensitivity, specificity, and inter-rater variability of the DWI b1000 scans for detection of ICH were determined.

RESULTS

In this preliminary pilot study, 15 patients with ICH and 17 patients with IS were included. All ICH lesions seen on NCCT showed a typical pattern on DW-MRI at b1000 with a hypointense core surrounded by a hyperintense rim. ICH volumes and size were similar on NCCT and MRI. All cases of IS were identified on the DWI scans but none were apparent on NCCT. The mean sensitivity and specificity of DW-MRI at b1000 for ICH were 94% and 93.5%, respectively, and the inter-rater variability for ICH detection on DWI was excellent (κ = .84).

CONCLUSIONS

DW-MRI at b1000 has a diagnostic yield similar to NCCT for detecting ICH and superior to NCCT for detecting IS. Therefore, DW-MRI may be considered as the initial screening tool for imaging patients presenting with focal neurologic symptoms suggestive of stroke.

GRE T2∗-weighted MRI: principles and clinical applications

The sequence of a multiecho gradient recalled echo (GRE) T2*-weighted imaging (T2*WI) is a relatively new magnetic resonance imaging (MRI) technique. In contrast to T2 relaxation, which acquires a spin echo signal, T2* relaxation acquires a gradient echo signal. The sequence of a GRE T2*WI requires high uniformity of the magnetic field. GRE T2*WI can detect the smallest changes in uniformity in the magnetic field and can improve the rate of small lesion detection. In addition, the T2* value can indirectly reflect changes in tissue biochemical components. Moreover, it can be used for the early diagnosis and quantitative diagnosis of some diseases. This paper reviews the principles and clinical applications as well as the advantages and disadvantages of GRE T2*WI.

The role of advanced neuroimaging in intracerebral hemorrhage

In this report, the authors sought to summarize existing literature to provide an overview of the currently available techniques and to critically assess the evidence for or against their application in intracerebral hemorrhage (ICH) for management, prognostication, and research. Functional imaging in ICH represents a potential major step forward in the ability of physicians to assess patients suffering from this devastating illness due to the advantages over standing imaging modalities focused on general tissue structure alone, but its use is highly controversial due to the relative paucity of literature and the lack of consolidation of the predominantly small data sets that are currently in existence. Current data support that diffusion tensor imaging and tractography, diffusion-perfusion weighted MRI techniques, and functional MRI all possess major potential in the areas of highlighting motor deficits, motor recovery, and network reorganization. Novel clinical studies designed to objectively assess the value of each of these modalities on a wider scale in conjunction with other methods of investigation and management will allow for their rapid incorporation into standard practice.

Advances in revascularization for acute ischemic stroke treatment

Intravenous thrombolysis with recombinant tissue plasminogen activator is the established treatment for acute ischemic stroke patients presenting within 3 h after stroke onset. In a significant number of patients, however, intravenous thrombolysis with recombinant tissue plasminogen activator remains ineffective. New thrombolytic agents, such as reteplase, tenecteplase or desmoteplase, offer pharmacokinetic and dynamic advantages over recombinant tissue plasminogen activator and have been or are currently being tested for safety and efficacy in clinical trials. Endovascular revascularization is an evolving treatment option enabling mechanical clot disruption or extraction in combination with thrombolysis. Several new endovascular devices have been successfully tested for safety in acute ischemic stroke patients and are now being tested for efficacy in larger clinical trials. Continued innovation and refinement of endovascular technology and techniques is expected to increase technical success with a minimal procedure-related morbidity in the treatment of acute ischemic stroke.

Diagnostic imaging for acute ischemic stroke management

Although our clinical understanding remains our most important diagnostic tool, acute stroke therapy without neuroimaging is impossible. In most patients, only non-contrast computed tomography is used for diagnosis of acute stroke. However, findings based exclusively on clinical assessment and nonhemorrhagic computed tomography scans may no longer be appropriate for acute stroke treatment. From a pathophysiologic point of view, advanced computed tomography techniques and stroke magnetic resonance imaging provide much more information about the acute stroke patient as the basis of decision making in acute stroke treatment. Advanced computed tomography may provide information comparable with stroke magnetic resonance imaging, although a more detailed evaluation concerning these methods in clinical practice is required. This review gives the reader an integrated view on the current status of acute stroke imaging based on advanced computed tomography and multiparametric stroke magnetic resonance imaging protocols. These new imaging techniques allow for a far more individualized method of decision making according to the findings in each patient. This results in improved identification of patients with acute stroke syndromes, improved patient selection of those patients who are regarded suitable for thrombolysis, an extension of the rather strictly defined therapeutic time window for treatment, as well as a more sophisticated method of introduction of alternative therapies into clinical practice.