Diffusion-weighted MRI as a screening tool of stroke in the ED

This report describes a novel imaging technology for the evaluation of stroke patients. Diffusion-weighted magnetic resonance imaging can visualize hyperacute ischemic stroke which cannot be seen on computed tomography; moreover, it only takes few minutes to scan. We believe that diffusion-weighted magnetic resonance imaging, rather than routine computed tomography, should be considered when the emergency physician evaluates a patient with acute ischemic stroke.     

CT and MR Imaging in the Acute Ischemic Stroke Patient: A Nursing Perspective

Historically, computed tomography (CT) head scan is the first diagnostic test for stroke-like symptoms. CT rules out hemorrhage immediately but a magnetic resonance (MR) imaging is more sensitive to early ischemia. New advances in CT and MR imaging techniques provide data to differentiate between reversible and irreversible brain damage with accurate identification of the site of arterial occlusion. The additional data may guide the stroke team in determining if the patient can safely be treated beyond the 0- to 3-hr window. Extending the window for treatment substantially increases the number of patients receiving stroke reversal. Nurses play an integral role in facilitating appropriate treatment and providing care to optimize patient’s clinical outcome. The purpose of this article was to discuss the clinical application of CT and MR imaging, define its purpose in acute ischemic stroke treatment, and guide stroke nurses in understanding the advanced concepts of imaging.     

Neuroimaging in acute stroke

This article reviews the various imaging modalities available for the evaluation of patients presenting with a potential stroke syndrome, specifically acute ischemic stroke, intracerebral hemorrhage, and subarachnoid hemorrhage. It reviews the various computed tomography (CT) modalities, including noncontrast brain CT (NCCT), CT angiography, and CT perfusion. It discusses multimodal magnetic resonance imaging in the evaluation of patients with acute stroke, including diffusion-weighted imaging, T2-weighted sequences/fluid-attenuated inversion recovery, magnetic resonance angiography, perfusion-weighted imaging, and gradient-recalled echo. At the end of this article, a brief review on how to read an NCCT geared toward the emergency physician is included.     

Fast patient workup in acute stroke using parallel imaging

Treatment of ischemic stroke is a very frustrating topic for neurologists. Presently, the most promising therapy seems to be thrombolysis of the clot. However, this intervention is associated with complication risks, most significantly the risk of post-treatment hemorrhage. This risk of bleeding increases not only with the size of the ischemic brain tissue but also with the time-to-treatment interval. Studies suggest a time window of 3 hours for most effective treatment. Hence, there is demand for a rapid imaging workup, which thus far has been accomplished with computed tomography. Because of the risks associated with thrombolytic therapy, more detailed information is desirable. The distinction between patients with viable ischemically challenged neural tissue and those with complete infarcts is of great importance, and computed tomography is insufficient for this task. This is also true for outlining the etiology of stroke, which may impact treatment. For these tasks, magnetic resonance imaging has been proposed. However, comprehensive imaging protocols take time, which is limited in stroke treatment. Therefore, new imaging techniques are required that provide both in-depth information and short scanning times. Parallel imaging is uniquely suited for this purpose.     

Magnetic resonance imaging of cerebral hemorrhagic stroke

Despite a traditional perception of reliance on computed tomography and lack of acceptance of magnetic resonance imaging (MRI) for detecting acute hemorrhage, MRI appears to be used increasingly in hemorrhagic stroke. This review addresses the MRI findings of acute hemorrhagic stroke obtained using relatively new imaging techniques. These new techniques have resulted in more acute stroke patients undergoing MRI examination. New information about the frequency and appearance of hemorrhage is emerging: for example, approximately 15-26% of cases of acute cerebral infarctions appear to be complicated by intracerebral hemorrhage. The MRI appearances of hemorrhagic transformation of ischemic infarction, as well as acute hypertensive intracerebral hemorrhage, are discussed based on clinical, biochemical, and technical aspects.     

Diffusion-weighted magnetic resonance imaging versus computed tomography in the diagnosis of acute ischemic stroke

Current treatment protocols using reperfusion therapy for acute ischemic stroke rely on non-contrast computed tomography (NCCT), with most indications including the absence of acute hemorrhage or large volume of infarction in the presence of clinical signs and symptoms. This predictably results in a significant incidence of the administration of reperfusion therapy to patients with "stroke mimics," such as migraine headache or Todd's paralysis after a seizure. Diffusion-weighted imaging (DWI) is a technique based on magnetic resonance imaging (MRI) that may be more sensitive and specific for acute cerebral ischemia than NCCT. In addition, data for techniques such as perfusion-weighted imaging can be acquired with minimal additional time required. This may allow better risk assessment of a clinical response to reperfusion therapy vs. the possibility of hemorrhagic complications. This article describes a methodical review of studies comparing the sensitivity, specificity, positive predictive value, and negative predictive value of DWI vs. NCCT in the evaluation of acute ischemic stroke. Data from studies meeting our screening criteria are combined to produce overall values for each.     

Imaging in acute brain infarction

Imaging in a patient suspected of having suffered an acute stroke is used primarily to clear the patient for thrombolytic therapy, by excluding intracranial hemorrhage and nonstroke causes of the patient's symptoms, within a critical 3-hour window. Noncontrast CT of the brain is the imaging test of choice for the initial evaluation of a patient with suspected acute ischemic stroke. It is rapid and readily available and has a high sensitivity for intracranial hemorrhage. Contrast-enhanced CT angiography and perfusion imaging may provide additional information with only a minimal increase in scanning time. Finally, diffusion-weighted magnetic resonance sequences have a high sensitivity for acute stroke and, with magnetic resonance perfusion imaging, may play an increasing role in the future treatment of stroke.     

Does primary stroke center certification change ED diagnosis,utilization, and disposition of patients with acute stroke?

Background and Purpose

We examined the impact of primary stroke center (PSC) certification on emergency department (ED) use and outcomes within an integrated delivery system in which EDs underwent staggered certification.

Methods

A retrospective cohort study of 30?461 patients seen in 17 integrated delivery system EDs with a primary diagnosis of transient ischemic attack (TIA), intracranial hemorrhage, or ischemic stroke between 2005 and 2008 was conducted. We compared ED stroke patient visits across hospitals for (1) temporal trends and (2) pre- and post-PSC certification—using logistic and linear regression models to adjust for comorbidities, patient characteristics, and calendar time, to examine major outcomes (ED throughput time, hospital admission, radiographic imaging utilization and throughput, and mortality) across certification stages.

Results

There were 15?687 precertification ED visits and 11?040 postcertification visits. Primary stroke center certification was associated with significant changes in care processes associated with PSC certification process, including (1) ED throughput for patients with intracranial hemorrhage (55 minutes faster), (2) increased utilization of cranial magnetic resonance imaging for patients with ischemic stroke (odds ratio, 1.88; 95% confidence interval, 1.36-2.60), and (3) decrease in time to radiographic imaging for most modalities, including cranial computed tomography done within 6 hours of ED arrival (TIA: 12 minutes faster, ischemic stroke: 11 minutes faster), magnetic resonance imaging for patients with ischemic stroke (197 minutes faster), and carotid Doppler sonography for TIA patients (138 minutes faster). There were no significant changes in survival.

Conclusions

Stroke center certification was associated with significant changes in ED admission and radiographic utilization patterns, without measurable improvements in survival.     

Neuroimaging of stroke: a review

Advances in neuroimaging technology during the past 30 years have resulted in a virtual explosion in the amount of pathologic information that can be obtained in the clinical stroke setting. This neuroimaging revolution has led to a much better understanding of cerebrovascular and tissue pathology, creating a wide array of opportunities for acute treatment and secondary prevention. Advances include early and accurate detection of ischemic and infarcted tissue and the ability to reveal hypoperfused tissue at risk. Clinicians are increasingly able to noninvasively detect embolic and atherothrombotic intravascular lesions. Vascular lesions associated with stroke can be characterized through endovascular neuroimaging techniques and repaired by various means. In this article, we provide an overview and update on the various techniques used in the neuroimaging of stroke and intracranial hemorrhage, including computed tomography, magnetic resonance imaging, ultrasound, and catheter angiography. We outline the specific role of each modality in clinical practice.     

Advanced neuroimaging in stroke patients: prediction of tissue fate and hemorrhagic transformation

Stroke is the second greatest cause of mortality worldwide after ischemic heart disease. It is also the leading cause of disability in industrialized countries. According to the WHO, 15 million people worldwide suffer a stroke annually. It is very difficult to distinguish between an ischemic and a hemorrhagic stroke on a clinical basis, therefore imaging (computed tomography or MRI) plays a central role in the evaluation of patients with acute stroke symptoms. Because of significant advances over the last decade, imaging now provides information beyond the mere presence or absence of intracerebral hemorrhage. Comprehensive neurovascular imaging protocols using computed tomography or MRI can be acquired within minutes, helping to distinguish stroke etiology and guiding treatment decisions for acute reperfusion therapies. The purpose of this article is to give an overview of diagnostic information provided by neuroimaging in the setting of acute stroke, especially ischemic stroke, including information about brain tissue viability status and blood-brain barrier permeability. We will discuss the indications of the current treatment options for stroke, and how imaging influences treatment decision. We will organize our discussion around the concept of the 'four Ps' (parenchyma, pipes, penumbra and permeability) proposed by Howard Rowley, which is an excellent guide for understanding the underlying causes and pathophysiology of ischemic stroke.     

Lesson of the month (1). Homonymous left hemianopia secondary to traumatic extracranial vertebral artery dissection

This lesson reports the case of a 32-year-old female presenting with left-sided homonymous hemianopia after a road traffic accident. A diagnosis of vertebral artery dissection (VAD) was missed at presentation after an initial computed tomography head scan was normal. Later, VAD was confirmed on neck magnetic resonance imaging. VAD is an uncommon cause of stroke in the young and, to date, there are no current emergency guidelines available for the management of patients with the condition.     

Emergency Diagnosis of Subarachnoid Hemorrhage: An Evidence-Based Debate

Background

The diagnosis of subarachnoid hemorrhage is of paramount concern in patients presenting to the Emergency Department (ED) with acute headache. Computed tomography followed by lumbar puncture is a time-honored practice, but recent technologic advances in magnetic resonance imaging with magnetic resonance angiography and computed tomography with computed tomography angiography can present alternatives for clinicians and patients.

Objective

The aim of this article was to compare diagnostic strategies for ED patients in whom subarachnoid hemorrhage is suspected.

Methods

We analyze and discuss current protocols, in addition to summarizing the advantages and disadvantages of each method.

Results

Through our residency's journal club, we organized an evidence-based debate that pitted proponents of the three subarachnoid hemorrhage diagnostic strategies against one another. Proponents of each strategy described its advantages and disadvantages. Briefly, computed tomography/lumbar puncture is time honored and effective, but is limited by complications and indeterminate lumbar puncture results. Magnetic resonance imaging with magnetic resonance angiography might be more effective in late presentations and can visualize aneurysms, yet has limited availability. Computed tomography with computed tomography angiography offers rapid diagnosis and is considered the most sensitive for diagnosing aneurysms, but has the highest radiation exposure.

Conclusions

Each of the three strategies used to diagnose subarachnoid hemorrhage has advantages and disadvantages with which clinicians should be familiar. Patient factors (e.g., age, body habitus, and risk factors), presentation factors (e.g., time from headache onset and severity of presentation), and institutional factors (availability of magnetic resonance imaging with magnetic resonance angiography) can influence the choice of protocol.     

Diffusion-weighted MRI of intracerebral hemorrhage clinically undifferentiated from ischemic stroke

This report describes diffusion-weighted MRI findings of some intracerebral hemorrhages clinically undifferentiated from ischemic stroke. We treated patients with characteristic features of intracerebral hemorrhages that could distinguish themselves from ischemic lesion on diffusion-weighted imaging. Therefore, we think diffusion-weighted imaging could be an emergency screening tool for ischemic stroke as an alternative to computed tomography, and the EP should be familiar with the diffusion-weighted imaging findings of intracerebral hemorrhage as well as cerebral infarction.     

Acute stroke: pathophysiology, diagnosis, and treatment

Stroke, a neurologic event due to altered cerebral circulation, is the third leading cause of death in the United States. Risk factors for stroke include hypertension, family history, and diabetes mellitus. The subtypes of stroke are ischemia, infarction, and hemorrhage. Ischemia and infarction are the result of atherosclerotic development of thrombi and emboli. Decreased and/or absent cerebral circulation causes neuronal cellular injury and death. Intracerebral hemorrhage occurs from rupture of cerebral vessels often as the result of hypertension. Patient assessment and diagnosis include the use of computed tomography scans, magnetic resonance imaging, and the National Institute of Health Stroke Scale, and treatment depends on the etiology of the stroke. Thrombolytic therapy is the mainstay of treatment for thrombotic and embolic events. Current recommendations for future stroke care include the development of designated stroke centers. Directions for research in stroke treatment includes examining neuroprotective therapies.     

Computed tomographic angiography and computed tomographic perfusion imaging of hyperacute stroke

The roles of noncontrast computed tomography (NCCT) and CT angiographic/CT perfusion (CTA/CTP) imaging in the rapid triage of clinically suspected hyperacute stroke patients to appropriate therapy is reviewed. Contraindications to thrombolysis include NCCT hemorrhage (absolute) and significant parenchymal hypodensity (relative). The sensitivity of NCCT for early (<6 h) stroke detection, higher than that of conventional magnetic resonance imaging, is improved further by using nonstandard window and level review settings. CTA/CTP is fast and convenient, adding approximately 10 min to the NCCT examination. CTA/CTP's accuracy in diagnosing ischemia and localizing thrombus to proximal or distal intracranial vessels far exceeds that of clinical examination (including National Institutes of Health stroke scale use), facilitating triage of appropriate candidates to intra-arterial thrombolysis. The size of the ischemic CTP hypodensity (proportional to reduced cerebral blood volume) predicts final infarct volume and clinical outcome; its location can guide the decision to perform intra-arterial thrombolysis, intravenous thrombolysis, or other treatment.     

Imaging methods in examining the anatomy and function of the lumbar spine

Conventional plain radiography, with or without flexion and extension images, is still the primary imaging modality of the lumbosacral spine despite the modern imaging methods. This is due to the simplicity of the technique and the good anatomical detail of the bone structure. Despite the limited information content of the plain radiographs, they are needed to serve as anatomical maps in connection with computed tomography or magnetic resonance imaging. In some institutions magnetic resonance imaging is now the primary modality for the evaluation of the lumbosacral spine, in others computed tomography and myelography still have a primary role, often depending on the availability of the devices. Magnetic resonance imaging clearly shows the anatomy of the discs, spinal nerves and dural sac. The diagnostic precision achieved with computed tomography in the evaluation of a herniated disc may also be achieved with magnetic resonance imaging. Differentiation of epidural scar from recurrent or residual disc herniation in patients with previous laminectomy, which with computed tomography myelography has been unreliable, can be evaluated by using magnetic resonance imaging enhanced with gadolinium-DTPA. The identification of facet joint disease is, however, less efficient with magnetic resonance imaging. Computed tomography and magnetic resonance imaging are probably nearly comparable in their accuracy in the evaluation of patients with sciatica. If cost and availability were not limiting factors, magnetic resonance imaging could provide an excellent screening technique for identifying individuals who would benefit from the identification of risks or preclinical disease or from institution of preventive measures.(ABSTRACT TRUNCATED AT 250 WORDS)     

Imaging-based treatment selection for intravenous and intra-arterial stroke therapies: a comprehensive review

Reperfusion therapy is the only approved treatment for acute ischemic stroke. The current approach to patient selection is primarily based on the time from stroke symptom onset. However, this algorithm sharply restricts the eligible patient population, and neglects large variations in collateral circulation that ultimately determine the therapeutic time window in individual patients. Time alone is unlikely to remain the dominant parameter. Alternative approaches to patient selection involve advanced neuroimaging methods including MRI diffusion-weighted imaging, magnetic resonance and computed tomography perfusion imaging and noninvasive angiography that provide potentially valuable information regarding the state of the brain parenchyma and the neurovasculature. These techniques have now been used extensively, and there is emerging evidence on how specific imaging data may result in improved clinical outcomes. This article will review the major studies that have investigated the role of imaging in patient selection for both intravenous and intra-arterial therapies.     

Imaging-based treatment selection for intravenous and intra-arterial stroke therapies: a comprehensive review

Reperfusion therapy is the only approved treatment for acute ischemic stroke. The current approach to patient selection is primarily based on the time from stroke symptom onset. However, this algorithm sharply restricts the eligible patient population, and neglects large variations in collateral circulation that ultimately determine the therapeutic time window in individual patients. Time alone is unlikely to remain the dominant parameter. Alternative approaches to patient selection involve advanced neuroimaging methods including MRI diffusion-weighted imaging, magnetic resonance and computed tomography perfusion imaging and noninvasive angiography that provide potentially valuable information regarding the state of the brain parenchyma and the neurovasculature. These techniques have now been used extensively, and there is emerging evidence on how specific imaging data may result in improved clinical outcomes. This article will review the major studies that have investigated the role of imaging in patient selection for both intravenous and intra-arterial therapies.     

Bilateral thalamic infarction in a patient with factor V Leiden mutation.

In a 50-year-old unresponsive man with ophthalmoplegia, bilateral thalamic infarction was detected on magnetic resonance imaging of the brain. A thorough evaluation, including urinalysis, laboratory studies, computed tomography of the brain, chest radiography, lumbar puncture, magnetic resonance angiography, cerebral angiography, carotid ultrasonography, and transesophageal echocardiography, revealed no obvious predisposing factors other than heterozygous factor V Leiden mutation. To our knowledge, this is the first reported case of bilateral thalamic infarction associated with factor V Leiden mutation. Physicians should consider the possibility of this mutation in patients with ischemic stroke if no other source is evident.     

Confirmation of traumatic interhemispheric subdural hematoma by magnetic resonance imaging

We report a case of interhemispheric subdural hematoma following closed head injury producing contralateral neurological findings and focal seizures. Noncontrast cranial computed tomography scan was initially reported to be normal, but magnetic resonance imaging of the brain demonstrated an interhemispheric subdural hematoma. Head injury, specifically occipital, is the leading cause of interhemispheric subdural hematoma in adults. Most patients develop a “falx syndrome”. If adequately interpreted, magnetic resonance imaging of the brain showing the appearance of blood on T1- and T2-weighted images can detect interhemispheric subdural hematoma. However, computed tomography scan should always be done first to detect intercranial bleeding, and it should be performed with and without contrast in patients with prior head trauma and delayed bleeds.