MR screening of candidates for thrombolysis: How to identify stroke mimics?

Synthetic FLAIR as a Substitute for FLAIR Sequence in Acute Ischemic Stroke

Background In acute ischemic stroke (AIS), fluid-attenuated inversion recovery (FLAIR) is used for treatment decisions when onset time is unknown. Synthetic FLAIR could be generated with deep learning from information embedded in diffusion-weighted imaging (DWI) and could replace acquired FLAIR sequence (real FLAIR) and shorten MRI duration. Purpose To compare performance of synthetic and real FLAIR for DWI-FLAIR mismatch estimation and identification of patients presenting within 4.5 hours from symptom onset. Materials and Methods In this retrospective study, all pretreatment and early follow-up (<48 hours after symptom onset) MRI data sets including DWI (b = 0-1000 sec/mm²) and FLAIR sequences obtained in consecutive patients with AIS referred for reperfusion therapies between January 2002 and May 2019 were included. On the training set (80%), a generative adversarial network was trained to produce synthetic FLAIR with DWI as input. On the test set (20%), synthetic FLAIR was computed without real FLAIR knowledge. The DWI-FLAIR mismatch was evaluated on both FLAIR data sets by four independent readers. Interobserver reproducibility and DWI-FLAIR mismatch concordance between synthetic and real FLAIR were evaluated with κ statistics. Sensitivity and specificity for identification of AIS within 4.5 hours were compared in patients with known onset time by using McNemar test. Results The study included 1416 MRI scans (861 patients; median age, 71 years [interquartile range, 57-81 years]; 375 men), yielding 1134 and 282 scans for training and test sets, respectively. Regarding DWI-FLAIR mismatch, interobserver reproducibility was substantial for real and synthetic FLAIR (κ = 0.80 [95% CI: 0.74, 0.87] and 0.80 [95% CI: 0.74, 0.87], respectively). After consensus, concordance between real and synthetic FLAIR was almost perfect (κ = 0.88; 95% CI: 0.82, 0.93). Diagnostic value for identifying AIS within 4.5 hours did not differ between real and synthetic FLAIR (sensitivity: 107 of 131 [82%] vs 111 of 131 [85%], P = .2; specificity: 96 of 104 [92%] vs 96 of 104 [92%], respectively, P > .99). Conclusion Synthetic fluid-attenuated inversion recovery (FLAIR) had diagnostic performances similar to real FLAIR in depicting diffusion-weighted imaging-FLAIR mismatch and in helping to identify early acute ischemic stroke, and it may accelerate MRI protocols. © RSNA, 2022 Online supplemental material is available for this article. See also the editorial by Carroll and Hurley in this issue.

Stroke mimics: incidence, aetiology, clinical features and treatment

Mimics account for almost half of hospital admissions for suspected stroke. Stroke mimics may present as a functional (conversion) disorder or may be part of the symptomatology of a neurological or medical disorder. While many underlying conditions can be recognized rapidly by careful assessment, a significant proportion of patients unfortunately still receive thrombolysis and admission to a high-intensity stroke unit with inherent risks and unnecessary costs. Accurate diagnosis is important as recurrent presentations may be common in many disorders. A non-contrast CT is not sufficient to make a diagnosis of acute stroke as the test may be normal very early following an acute stroke. Multi-modal CT or magnetic resonance imaging (MRI) may be helpful to confirm an acute ischaemic stroke and are necessary if stroke mimics are suspected. Treatment in neurological and medical mimics results in prompt resolution of the symptoms. Treatment of functional disorders can be challenging and is often incomplete and requires early psychiatric intervention.

Ischemic stroke with a preceding Trans ischemic attack (TIA) less than 24 hours and thrombolytic therapy

Background

Acute ischemic stroke attack with and without a recent TIA may differ in clinical risk factors, and this may affect treatment outcomes following thrombolytic therapy. We examined whether the odds of exclusion or inclusion for thrombolytic therapy are greater in ischemic stroke with TIA less than 24 h preceding ischemic stroke (recent-TIA) as compared to those without recent TIA or non-TIA > 24 h and less than 1 month (past-TIA).

Methods

A retrospective hospital-based analysis was conducted on 6315 ischemic stroke patients, of whom 846 had proven brain diffusion-weighted magnetic resonance imaging (DW-MRI) of an antecedent TIA within 24 h prior to ischemic stroke. The logistic regression model was developed to generate odds ratios (OR) to determine clinical factors that may increase the likelihood of exclusion or inclusion for thrombolytic therapy. The validity of the model was tested using a Hosmer-Lemeshow test, while the Receiver Operating Curve (ROC) was used to test the sensitivity of our model.

Results

In the recent-TIA ischemic stroke population, patients with a history of alcohol abuse (OR = 5.525, 95% CI, 1.003–30.434, p = 0.05), migraine (OR = 4.277, 95% CI, 1.095–16.703, p = 0.037), and increasing NIHSS score (OR = 1.156, 95% CI, 1.058–1.263, p = 0.001) were associated with the increasing odds of receiving rtPA, while older patients (OR = 0.965, 95% CI, 0.934–0.997, P = 0.033) were associated with the increasing odds of not receiving rtPA.

Conclusion

In recent-TIA ischemic stroke patients, older patients with higher INR values are associated with increasing odds of exclusion from thrombolytic therapy. Our findings demonstrate clinical risks factors that can be targeted to improve the use and eligibility for rtPA in in recent-TIA ischemic stroke patients.

Stroke-mimics in stroke-units. Evaluation after changes imposed by randomized trials

BACKGROUND

A larger therapeutic window for stroke treatment requires a significant change in the organization of emergency services, avoiding the increase in number of imaging exams and indirectly the time to treatment.

OBJECTIVE

To highlight the relation between faster clinical evaluation and stroke over-suspicion and consequently excessive imaging acquisition. To identify predictors of ischemic stroke and stroke mimics (SM), aiming for better patient selection for comprehensive neuroimaging and reperfusion therapies.

METHODS

Retrospective, cohort, observational, single-center study that reviewed all consecutive files of patients presenting with acute neurological symptoms who underwent CT scan or MRI from July 1, 2016 to July 1, 2017.

RESULTS

736 patient files were reviewed. 385 patients (52.3%) presented with confirmed acute ischemic infarct, 93 (12.6%) had another brain lesion mimicking acute ischemia, and 258 (35.1%) had normal imaging. Acute stroke was more frequent in elderly patients with atrial fibrillation, arterial hypertension, or dysarthria or right motor impairment. Stroke mimic was associated with female patients with low vascular risk factors, low NIHSS, and patients with decreased level of consciousness or symptoms suggestive of posterior circulation.

DISCUSSION

47.7% of all patients seen at the stroke unit did not have acute stroke lesions. Clinical assessment data have been used to provide indicators of acute stroke and stroke mimic patients, and symptoms corresponding to acute stroke and stroke mimic seem to be similar in the literature.

CONCLUSION

Considering that the number of patients admitted for stroke treatment will increase even further with a larger therapeutic window for mechanical thrombectomy and for thrombolysis, a diagnostic decision-making algorithm for stroke patients is required in order to reinforce the suspicion of stroke indicating an urgent MRI.

Emergency management of stroke in the era of mechanical thrombectomy

Emergency management of stroke has been directed at the delivery of recombinant tissue plasminogen activator (tPA) in a timely fashion. Because of the many limitations attached to the delivery of tPA and the perceived benefits accrued to tPA, its use has been limited. Mechanical thrombectomy, a far superior therapy for the largest and most disabling strokes, large vessel occlusions (LVOs), has changed the way acute strokes are managed. Aside from the rush to deliver tPA, there is now a need to identify LVO and refer those patients with LVO to physicians and facilities capable of delivering urgent thrombectomy. Other parts of emergency department management of stroke are directed at identifying and mitigating risk factors for future strokes and at preventing further damage from occurring. We review here the most recent literature supporting these advances in stroke care and present a framework for understanding the role that emergency physicians play in acute stroke care.

Postictal syndrome: The forgotten continent. An overview of the clinical, biochemical and imaging features

Postictal syndrome (PIS) encompasses the clinical, biological, electroencephalographic (EEG) and magnetic resonance imaging (MRI) signs that follow the termination of a seizure. These signs occur as soon as the epileptic discharge ends, but might remain for a substantially long period of time, making them amenable to clinical observation. As a direct consequence, neurologists and intensivists are more frequently attending patients with PIS than during their seizure. Moreover, careful PIS documentation may help physicians to diagnose epileptic seizure from other non-epileptic disorders. Careful analysis of PIS could also be helpful to better characterize the seizure (seizure subtypes, and to some extent, the localization and/or lateralization of the seizure). This article aims to review the main clinical, biological, EEG and MRI components of PIS, discuss differential diagnoses and propose a general clinical attitude, based on the acronym "WAITTT": W for "Watch", to monitor and investigate PIS in order to provide relevant information on seizure, AIT for "Avoid Inappropriate Treatment", to underscore the risk carrying out unnecessary drug injections and intensive care procedures in the setting of a self-limited symptomatology, and TT for "Take Time", to keep in mind that time remains the clinician's best ally for treating patients with PIS.

Diagnosing cerebral ischemia with door-to-thrombolysis times below 20 minutes

Objectives

To clarify diagnostic accuracy and consequences of misdiagnosis in the admission evaluation of stroke-code patients in a neurologic emergency department with less than 20-minute door-to-thrombolysis times.

Methods

Accuracy of admission diagnostics was studied in an observational cohort of 1,015 stroke-code patients arriving by ambulance as candidates for recanalization therapy between May 2013 and November 2015. Immediate admission evaluation was performed by a stroke neurologist or a neurology resident with dedicated stroke training, primarily utilizing CT-based imaging.

Results

The rate of correct admission diagnosis was 91.1% (604/663) for acute cerebral ischemia (ischemic stroke/TIA), 99.2% (117/118) for hemorrhagic stroke, and 61.5% (144/234) for stroke mimics. Of the 150 (14.8%) misdiagnosed patients, 135 (90.0%) had no acute findings on initial imaging and 100 (67.6%) presented with NIH Stroke Scale score 0 to 2. Misdiagnosis altered medical management in 70 cases, including administration of unnecessary treatments (thrombolysis n = 13, other n = 24), omission of thrombolysis (n = 5), delays to specific treatments of stroke mimics (n = 13, median 56 [31–93] hours), and delays to antiplatelet medication (n = 14, median 1 [1–2] day). Misdiagnosis extended emergency department stay (median 6.6 [4.7–10.4] vs 5.8 [3.7–9.2] hours; p = 0.001) and led to unnecessary stroke unit stay (n = 10). Detailed review revealed 8 cases (0.8%) in which misdiagnosis was possible or likely to have worsened outcomes, but no death occurred as a result of misdiagnosis.

Conclusions

Our findings support the safety of highly optimized door-to-needle times, built on thorough training in a large-volume, centralized stroke service with long-standing experience. Augmented imaging and front-loaded specialist engagement are warranted to further improve rapid stroke diagnostics.

Neurology Concepts: Young Women and Ischemic Stroke-Evaluation and Management in the Emergency Department

OBJECTIVE

Ischemic stroke is a leading cause of morbidity and mortality worldwide. While the incidence of ischemic stroke is highest in older populations, incidence of ischemic stroke in adults has been rising particularly rapidly among young (e.g., premenopausal) women. The evaluation and timely diagnosis of ischemic stroke in young women presents a challenging situation in the emergency department, due to a range of sex-specific risk factors and to broad differentials. The goals of this concepts paper are to summarize existing knowledge regarding the evaluation and management of young women with ischemic stroke in the acute setting.

METHODS

A panel of six board-certified emergency physicians, one with fellowship training in stroke and one with training in sex- and sex-based medicine, along with one vascular neurologist were coauthors involved in the paper. Each author used various search strategies (e.g., PubMed, PsycINFO, and Google Scholar) for primary research and reviewed articles related to their section. The references were reviewed and evaluated for relevancy and included based on review by the lead authors.

RESULTS

Estimates on the incidence of ischemic stroke in premenopausal women range from 3.65 to 8.9 per 100,000 in the United States. Several risk factors for ischemic stroke exist for young women including oral contraceptive (OCP) use and migraine with aura. Pregnancy and the postpartum period (up to 12 weeks) is also an important transient state during which risks for both ischemic stroke and cerebral hemorrhage are elevated, accounting for 18% of strokes in women under 35. Current evidence regarding the management of acute ischemic stroke in young women is also summarized including use of thrombolytic agents (e.g., tissue plasminogen activator) in both pregnant and nonpregnant individuals.

CONCLUSION

Unique challenges exist in the evaluation and diagnosis of ischemic stroke in young women. There are still many opportunities for future research aimed at improving detection and treatment of this population.

Description of stroke mimics after complete neurovascular assessment

INTRODUCTION

A considerable percentage of events initially diagnosed as ischaemic stroke have non-cerebrovascular causes; these are called stroke mimics (SM). Currently available evidence about these events is heterogeneous and comes from studies with small samples.

OBJECTIVE

The purpose of our study is to identify conditions that may present as SM, define their epidemiological and clinical characteristics, and determine the percentage of cases of SM treated with intravenous fibrinolysis.

METHODS

Prospective study including all patients admitted to a tertiary university hospital between June 2005 and April 2015 with a diagnosis of acute stroke. We analysed demographic data, cardiovascular risk factors, time from code stroke activation to admission, stroke severity (NIHSS), final destination after discharge, degree of disability (mRS), and treatment. We compared SM and ischaemic strokes. We ruled out patients with intracranial haemorrhage, subarachnoid haemorrhage, or other causes of SM that may be detected on the baseline CT scan.

RESULTS

Four hundred four of the 4,570 included patients (8.8%) were found to have SM. Patients with SM were younger (70.3 vs. 74, P<.0001), less likely to exhibit cardiovascular risk factors and atrial fibrillation (13 vs. 34%, P<.0001), scored lower on the NIHSS at baseline (2 vs. 4, P<.0001), and included fewer cases of aphasia (9.4 vs. 19.6%, P<.02) and dysphagia (1.2 vs. 17%, P<.0001) than patients with stroke. SM caused fewer code stroke activations (28 vs. 40%, P<.0001). Patients with SM required shorter hospital stays (4.9 vs. 7.8 days, P<.0001), were less frequently admitted to the stroke unit (47 vs. 60%, P<.0001) and more frequently discharged home (95 vs. 62%, P<.0001), and had better outcomes (mRS scores 0-2; 76 vs. 54%, P<.0001). Intravenous fibrinolysis was administered to 4.7% of these patients. Epileptic seizures were the most frequent cause of SM (26%).

CONCLUSIONS

In our sample, 8.8% of all diagnoses of ischaemic stroke were SM. These events have different demographic, clinical, and prognostic characteristics; epilepsy is the most common aetiology. Despite receiving specialised emergency care, 19 patients with SM (4.7%) were treated with intravenous fibrinolysis.

ASL and susceptibility-weighted imaging contribution to the management of acute ischaemic stroke

Abstract

Magnetic resonance imaging (MRI) plays a central role in the early diagnosis of cerebral vascular events. Today, MRI is used not only for the detection of acute ischaemic lesions, but also to fine tune the diagnosis and improve patient selection for early therapeutic decision-making. In this perspective, new tools such as arterial spin labelling (ASL) and susceptibility-weighted imaging (SWI) sequences have been developed. These MRI sequences enable noninvasive assessment of brain damage, providing important diagnostic and prognostic information: evaluation of cerebral parenchymal perfusion; detection and aetiological assessment of thrombi; ruling out differential diagnoses. After a brief recall of the fundamental basis of these sequences, this article proposes an update on their current contribution to the early management of stroke victims.

Teaching Points

• These noninvasive sequences provide essential information for early management of acute stroke.

• They can detect zones of parenchymal hypoperfusion.

• Susceptibility-weighted sequences provide information on thrombus localisation and composition.

• ASL can identify certain aetiologies of stroke mimics.

• Post-therapeutic ASL perfusion status predicts outcome.