Controversies in Imaging of Patients With Acute Ischemic Stroke: AJR Expert Panel Narrative Review.

The development of reperfusion therapies has profoundly impacted stroke care, initially with the advent of IV thrombolytic treatment and, more recently, with the development and refinement of endovascular treatment (EVT). Progress in neuroim-aging has supported the paradigm shift of stroke care, and advanced neuroimaging now has a fundamental role in triaging patients for both IV thrombolytic treatment and EVT. As the standard of care for acute ischemic stroke (AIS) evolves, controversies remain in certain clinical scenarios. This article explores the use of multimodality imaging for treatment selection of patients with AIS in the context of recent guidelines, highlighting controversial topics and providing guidance for clinical practice. The results of major randomized trials supporting EVT are reviewed. The advantages and disadvantages of CT, CTA, MRI, and MRA in stroke diagnosis are summarized with attention to level 1 evidence supporting the role of vascular imaging and perfusion imaging. Patient selection is compared between approaches based on time thresholds and physiologic approaches based on infarct core measurement using imaging. Moreover, various imaging approaches to core measurement are described. As ongoing studies push treatment boundaries, advanced imaging is expected to help identify a widening range of patients who may benefit from therapy.

Malignant transformation of vestibular schwannoma after radiation therapy.

Stereotactic radiosurgery (SRS) is an effective treatment for vestibular schwannomas, offering high rates of tumor control and low neurological risks. Long-term complications of SRS are not fully understood, with several cases of malignant transformation reported in the literature. We report the case of a 50-year-old female with no prior history of neurofibromatosis who presented in 2013 with MRI evidence of a benign vestibular schwannoma. Despite treatment with CyberKnife SRS, she presented 6 years later with new onset neurologic symptoms. Further investigation showed stable lesion size with increasing vasogenic edema and a new area of enhancement in the brainstem, suspicious for malignant transformation. Subsequent treatment with partial craniectomy and histopathologic analysis was consistent with a malignant peripheral nerve sheath tumor diagnosis. Our case adds to a series of 24 similar cases in the literature, details of which have been summarized in our study. Overall, findings support the need for lifelong surveillance following SRS treatment of benign vestibular schwannomas. Patients should be educated on the potential risk of this complication, and clinicians must maintain a high level of suspicion for potential radiation-induced malignancy during the patient's clinical course.

Influence of Stroke Onset Location on the Efficacy of Endovascular Thrombectomy: Comparison of Outcomes Between In-hospital vs. Community-Onset Strokes.

BACKGROUND AND PURPOSE: Previous studies have suggested that patients suffering an in-hospital stroke (IHS) may face delays in treatment and worse outcomes compared to patients with community-onset strokes (COS). However, most studies occurred when intravenous thrombolysis was the primary treatment. This study aimed to examine the outcomes of patients experiencing an IHS in the endovascular thrombectomy (EVT) era. MATERIALS AND METHODS: Single-center retrospective cohort study of patients older than 18 years with acute ischemic stroke (AIS) treated with EVT within 12 hours of stroke onset from January 1, 2015, to April 30, 2021. Patients were classified into two groups: in-hospital strokes (IHS) and community-onset strokes (COS). We compared time metrics of stroke care delivery, rate of successful reperfusion, and functional outcome as scored using the modified Rankin Scale (mRS) score at 90 days (favorable outcome was defined as mRS 0-2). Differences in proportions were assessed using Fisher's exact and Chi-Square tests as appropriate. For continuous variables, differences in medians between groups were evaluated using Mann-Whitney U tests. RESULTS: A total of 676 consecutive patients were included, with 69 (10%) comprising the IHS group. IHS patients were more likely to have diabetes (36% vs. 18%, p=0.02) and less likely to receive thrombolysis (25% vs 68%, p<0.001) than the COS group but were otherwise similar. IHS patients had significantly faster overall time metrics, most notably from stroke recognition to imaging (median [IQR], 70 [38-141] min vs 121 [74-228] min, p<0.001). Successful recanalization was achieved in > 75% in both groups (p=0.39), with a median NIHSS at discharge <4 (p=0.18). The 90-day mRS was similar in both groups, with a trend of higher in-hospital mortality in the IHS group (p=0.06). CONCLUSIONS: IHS patients had shorter workflow delays to initiation of EVT compared to their community counterparts but with a similar rate of successful recanalization and clinical outcomes. Importantly, 90 day mortality and mRS scores were equivalent between IHS and COS. ABBREVIATIONS: AIS = acute ischemic stroke; LVO = large vessel occlusion; IHS= in-hospital stroke; COS= community-onset stroke; EVT= endovascular thrombectomy; CSC= comprehensive stroke center; TOAST= Trial of Org 10172 in Acute Stroke Treatment.

A Pilot Clinical and Technical Validation of an Immersive Virtual Reality Platform for 3D Anatomical Modeling and Contouring in Support of Surgical and Radiation Oncology Treatment Planning.

The aim of this study was to validate a novel medical virtual reality (VR) platform used for medical image segmentation and contouring in radiation oncology and 3D anatomical modeling and simulation for planning medical interventions, including surgery. The first step of the validation was to verify quantitatively and qualitatively that the VR platform can produce substantially equivalent 3D anatomical models, image contours, and measurements to those generated with existing commercial platforms. To achieve this, a total of eight image sets and 18 structures were segmented using both VR and reference commercial platforms. The image sets were chosen to cover a broad range of scanner manufacturers, modalities, and voxel dimensions. The second step consisted of evaluating whether the VR platform could provide efficiency improvements for target delineation in radiation oncology planning. To assess this, the image sets for five pediatric patients with resected standard-risk medulloblastoma were used to contour target volumes in support of treatment planning of craniospinal irradiation, requiring complete inclusion of the entire cerebral-spinal volume. Structures generated in the VR and the commercial platforms were found to have a high degree of similarity, with dice similarity coefficient ranging from 0.963 to 0.985 for high-resolution images and 0.920 to 0.990 for lower resolution images. Volume, cross-sectional area, and length measurements were also found to be in agreement with reference values derived from a commercial system, with length measurements having a maximum difference of 0.22 mm, angle measurements having a maximum difference of 0.04°, and cross-sectional area measurements having a maximum difference of 0.16 mm2. The VR platform was also found to yield significant efficiency improvements, reducing the time required to delineate complex cranial and spinal target volumes by an average of 50% or 29 min.

MRI findings in an infant with vaccine-associated paralytic poliomyelitis.

Although acute flaccid paralysis is a manifestation observed in several neurologic and muscular disorders, vaccine-associated paralytic poliomyelitis (VAPP) is an exceedingly rare etiology. In the clinical setting of acute flaccid paralysis, MRI is useful in differentiating between VAPP and other conditions. Additionally, MRI can assess the extent of lesions. However, reports on MRI findings in VAPP are scarce in the pediatric radiology literature. We report a Brazilian infant who developed VAPP 40 days after receiving the first dose of oral polio vaccine (OPV). MR images of the cervical and thoracic spinal cord showed lesions involving the anterior horn cell, with increased signal intensity on T2-weighted sequences. We would like to emphasize the importance of considering VAPP as a differential diagnosis in patients with acute flaccid paralysis and an MRI showing involvement of medulla oblongata or spinal cord, particularly in countries where OPV is extensively administered.

Reversible sulcal FLAIR hyperintensity on MRI in a migraine patient with aura.

Reversible sulcal fluid-attenuated inversion recovery (FLAIR) hyperintensity is a rare imaging finding that could be seen on magnetic resonance imaging (MRI), in patients with migraine with aura. Herein, we present a patient who was admitted to the emergency department with severe headaches, numbness on the right side of the body, and visual changes. MRI showed sulcal FLAIR hyperintensity in the occipital lobes, with no other abnormality. The patient was diagnosed with migraine with aura by neurology and the follow up MRI showed resolution of the finding, supporting the diagnosis. Sulcal hyperintensity on FLAIR is a nonspecific imaging finding that can occur with or without cerebral spinal fluid (CSF) abnormality. Although, clinical correlation and CSF analysis may be required, radiologists may often be able to suggest the cause of abnormal CSF signal depending on the distribution of sulcal FLAIR hyperintensity, and the presence of additional imaging findings.