Susceptibility-Weighted Imaging in Pediatric Arterial Ischemic Stroke: A Valuable Alternative for the Noninvasive Evaluation of Altered Cerebral Hemodynamics

BACKGROUND AND PURPOSE:SWI provides information about blood oxygenation levels in intracranial vessels. Prior reports have shown that SWI focusing on venous drainage can provide noninvasive information about the degree of brain perfusion in pediatric arterial ischemic stroke. We aimed to evaluate the influence of the SWI venous signal pattern in predicting stroke evolution and the development of malignant edema in a large cohort of children with arterial ischemic stroke.MATERIALS AND METHODS:A semiquantitative analysis of venous signal intensity on SWI and diffusion characteristics on DTI was performed in 16 vascular territories. The mismatch between areas with SWI-hypointense venous signal and restricted diffusion was correlated with stroke progression on follow-up. SWI-hyperintense signal was correlated with the development of malignant edema.RESULTS:We included 24 children with a confirmed diagnosis of pediatric arterial ischemic stroke. Follow-up images were available for 14/24 children. MCA stroke progression on follow-up was observed in 5/6 children, with 2/8 children without mismatch between areas of initial SWI hypointense venous signal and areas of restricted diffusion on DTI. This mismatch showed a statistically significant association (P = .03) for infarct progression. Postischemic malignant edema developed in 2/10 children with and 0/14 children without SWI-hyperintense venous signal on initial SWI (P = .07).CONCLUSIONS:SWI-DTI mismatch predicts stroke progression in pediatric arterial ischemic stroke. SWI-hyperintense signal is not useful for predicting the development of malignant edema. SWI should be routinely added to the neuroimaging diagnostic protocol of pediatric arterial ischemic stroke.

Acute arterial ischemic stroke (AIS) affects 2–5/100,000 children every year and is associated with high mortality and morbidity.¹ The mortality rate is estimated at 5%–13%, and moderate-to-severe neurologic deficits or epilepsy occur in >50% of children after AIS.^2,3 The Chest and American Heart Association guidelines support the use of anticoagulation in acute pediatric arterial ischemic stroke (PAIS) despite of the absence of large-scale clinical trials.^4,5 Antithrombotic therapy aims to prevent early propagation of the thrombus, inhibit the formation of new thrombus, and promote early recanalization to save hypoperfused tissue at risk of irreversible ischemic infarction. However, the diagnosis of PAIS should be made first, and tissue at risk for infarction should be detected. The diagnosis of PAIS is frequently delayed or missed.⁶ DWI/DTI is a highly sensitive MR imaging sequence in detecting early ischemic regions and is the diagnostic criterion standard for imaging acute PAIS.⁷ Neuroimaging techniques that allow early, reliable, noninvasive identification of potentially salvageable hypoperfused brain tissue—the so called ischemic penumbra—are imperative to guide treatment.SWI is a high-spatial-resolution, gradient-echo MR imaging sequence that accentuates the magnetic properties of various substances such as blood, blood products, nonheme iron, and calcification.⁸ In addition, SWI accentuates magnetic susceptibility differences between deoxygenated hemoglobin in the vessels and adjacent oxygenated tissues. A few previous reports have shown that SWI-hypointense signals in veins draining hypoperfused brain areas provide indirect evaluation of critically perfused tissue by focusing on venous drainage.^9–12 In addition, SWI-hyperintense signal was reported to detect regions of hyperperfusion and to be associated with an increased risk of developing postischemic malignant edema.¹³ SWI may consequently serve as a valuable alternative sequence to evaluate the hemodynamics of brain tissue in PAIS.The aims of this retrospective study were to evaluate the potential of acute SWI to identify potentially salvageable brain tissue and to predict the development of postischemic malignant edema in the largest cohort of PAIS reported so far, to our knowledge. We hypothesized that hypointense venous signal on acute SWI may identify brain tissue at risk of infarction progression by focusing on venous drainage and that the presence of SWI-hyperintense venous signal may predict the development of postischemic malignant edema.     

Receptor Tyrosine Kinase Fusions and BRAF Kinase Fusions are Rare but Actionable Resistance Mechanisms to EGFR Tyrosine Kinase Inhibitors

Introduction

We analyzed a large set of EGFR-mutated (EGFR+) NSCLC to identify and characterize cases with co-occurring kinase fusions as potential resistance mechanisms to EGFR tyrosine kinase inhibitors (TKIs).

Multifocal infantile hepatic hemangiomas—imaging strategy and response to treatment after propranolol and steroids including review of the literature

Infantile hepatic hemangioma is the most common benign liver tumor during infancy. Prompt diagnosis and timely institution of therapy are of utmost importance. Magnetic resonance imaging (MRI) plays a key role in the correct diagnosis and monitoring of treatment. We report on a 15-week-old girl with multifocal infantile hemangiomas of the liver and high output congestive heart failure. Diagnosis was confirmed by MRI. Subsequent treatment with propranolol and steroids showed dramatic regression of the lesions within 24?weeks. We present the characteristic MRI findings and discuss treatment options together with a comprehensive review of the relevant literature. Conclusion Propranolol appears highly efficacious in the management of infantile hepatic hemangioma; dedicated MRI is essential in confirming the diagnosis and monitoring of treatment.     

Spinal Nerve Root Enhancement on MRI Scans in Children: A Review

Spinal nerve root enhancement in pediatric patients is generally nonspecific, and clinical and laboratory correlation is essential. Nerve root enhancement indicates lack of integrity of the blood‐nerve barrier. In this review, we will present a range of pediatric conditions that can present with spinal nerve root enhancement including inflammatory, infectious, hereditary, and neoplastic causes. Familiarity with the various pathologic entities associated with spinal nerve root enhancement is important for a concise differential diagnosis in the appropriate clinical setting. This will avoid unnecessary additional investigations.