Pictorial review: challenges in distinguishing bilateral metaphyseal marrow abnormalities on magnetic resonance imaging.

The paediatric metaphysis is afflicted by a wide range of pathological processes as it is the most metabolically active and well-vascularised part of the developing skeleton. This review focuses on metaphyseal marrow signal change detected with magnetic resonance imaging, which is most often occult on radiographs. When bilateral, these imaging appearances frequently present a diagnostic quandary. This review assists the radiologist to confidently dismiss physiological signal change and confidently work through the differential diagnosis. This is achieved by illustrating a practical method of classifying signal change into four categories: physiological red marrow, red marrow reconversion, marrow infiltration, and oedema-like marrow signal intensity. In doing so, various pathological entities are reviewed along with imaging pearls and next-step investigations.

Appendiceal involvement in pediatric inflammatory multisystem syndrome temporally associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2): a diagnostic challenge in the coronavirus disease (COVID) era.

BACKGROUND: Many studies on pediatric inflammatory multisystem syndrome temporally associated with severe acute respiratory syndrome coronavirus 2 (PIMS-TS) have described abdominal findings as part of multisystem involvement, with limited descriptions of abdominal imaging findings specific to PIMS-TS. OBJECTIVE: To perform a detailed evaluation of abdominal imaging findings in children with PIMS-TS. MATERIALS AND METHODS: We performed a single-center retrospective study of children admitted to our institution between April 2020 and January 2021 who fulfilled Royal College of Paediatrics and Child Health criteria for PIMS-TS and who had cross-sectional abdominal imaging. We studied clinical data, abdominal imaging, laboratory markers, echocardiography findings, treatment and outcomes for these children. We also reviewed the literature on similar studies. RESULTS: During the study period, 60 PIMS-TS cases were admitted, of whom 23 required abdominal imaging. Most (74%) were from a Black, Asian or minority ethnic background and they had an average age of 7 years (range 2-14 years). All children had fever and gastrointestinal symptoms on presentation with elevated C-reactive protein, D-dimer and fibrinogen. Most had lymphopenia, raised ferritin and hypoalbuminemia, with positive severe acute respiratory syndrome coronavirus 2 immunoglobulin G antibodies in 65%. Free fluid (78%), right iliac fossa mesenteric inflammation (52%), and significantly enlarged mesenteric lymph nodes (52%) were the most common imaging findings. Appendiceal inflammation (30%) and abnormal distal ileum and cecum/ascending colon wall thickening (35%) were also common. All children responded well to medical management alone, with no mortality. CONCLUSION: In addition to free fluid, prominent lymphadenopathy, and inflammatory changes in the right iliac fossa, we found abnormal long-segment ileal thickening and appendicitis to be frequent findings. Recognition of appendiceal involvement as a component of the PIMS-TS spectrum should help clinicians avoid unnecessary surgical intervention as part of a multidisciplinary team approach.

Customized approach for upfront or delayed resection using radiological criteria in unilateral, nonmetastatic pediatric renal tumors: A prospective study.

BACKGROUND: The availability of robust, equivalent data regarding outcomes for upfront or delayed surgery for renal tumors in children leads to a dilemma in selecting the initial treatment. Imaging criteria associated with the probability of rupture or incomplete resection may provide a more objective assessment for customization for the timing of surgery. PROCEDURE: Eighty-three children with unilateral, nonmetastatic renal tumors were enrolled between January 2012 and April 2018. Upfront nephrectomy was performed in the absence or delayed surgery (after a biopsy and chemotherapy) in the presence of one or more imaging-based high-risk features, including perinephric spread or adjacent organ infiltration, tumors crossing the midline, intravascular thrombus, and extensive adenopathy. Post hoc analysis for interobserver concordance for high-risk imaging features was also performed. RESULTS: The upfront surgery group (19) had predominantly stage I or II diseases (89%) and the histological types were Wilms (13), non-Wilms (5) renal tumor, and an inflammatory lesion. The delayed surgery group had 60% with stage I or II diseases and the histological types were Wilms (60) and non-Wilms (4) tumor. In addition, high-risk pathology was identified in nine patients. Overall, 27 patients with Wilms tumors required radiotherapy and anthracycline because of stage III disease, including one in the immediate surgery group. The event-free and overall survival (OS) at a median follow-up of 39 months for Wilms tumor are 88% (95% confidence interval [CI]: 78.5-94.9%) and 89% (95% CI: 81.4-96.6%), 85.1% (95% CI: 73.8-93.4%) and 86.5% (95% CI: 77.4-95.8%) for the delayed, and 100% event-free survival as well as OS (P = .1) in the upfront surgery group. CONCLUSION: A customized approach pivoted on image-based high-risk features facilitates identification of patients with early-stage renal tumor when the timing of surgery is tailored. Moreover, non-Wilms tumor and high-risk pathology are also identified.

Magnetic Resonance Imaging Features of Sporadic Optic Chiasmatic-Hypothalamic Gliomas and Correlation with Histopathology and BRAF Gene Alterations.

OBJECTIVE: Sporadic optic chiasmatic-hypothalamic gliomas (OCHGs), though histologically low-grade tumors, manifest as aggressive neoplasms radiologically, leading to difficulty in diagnosis. Molecular alterations of the BRAF gene are detectable in a majority of sporadic OCHGs. The purpose of our study was to elucidate the characteristic imaging features of sporadic OCHGs and to investigate whether imaging phenotypes could potentially correlate with specific BRAF gene alterations associated with these tumors. METHODS: We retrospectively reviewed baseline magnetic resonance (MR) images and medical records of 26 patients with histopathologically proven sporadic OCHGs. MR imaging (MRI) features were systematically evaluated. Statistical analysis was performed to determine whether there was a significant association between imaging findings and BRAF molecular alterations. RESULTS: Twenty-two cases (84.6%) presented with solid-cystic masses, while four (15.4%) presented with purely solid lesions. In all 26 cases, the solid component revealed central necrosis; there was minimal necrosis in 11 cases (42.3%), moderate in 8 (30.7%), and marked in 7 (26.9%). The presence of multiple cysts (>4) and minimal necrosis showed a significant association with BRAFV600E mutation (P < 0.005). Marked necrosis in the solid component significantly correlated with BRAF wild genotype (P < 0.001). The presence of a single peripheral cyst significantly correlated with BRAF fusion (P = 0.04). CONCLUSION: Sporadic OCHGs have a distinctive appearance on imaging. The solid-cystic composition coupled with varying degrees of central necrosis are clues to the radiological diagnosis of this entity and can facilitate early recognition in clinical practice. Imaging could potentially serve as a non-invasive predictor of the BRAF alteration status, thereby serving as a prognostic marker and guiding personalized management.

Can MRI biomarkers for hearing loss in enlarged vestibular aqueduct be measured reproducibly?

OBJECTIVE: Morphological features of an enlarged endolymphatic duct (ED) and sac (ES) are imaging biomarkers for genotype and hearing loss phenotype. We determine which biomarkers can be measured in a reproducible manner, facilitating further clinical prediction studies in enlarged vestibular aqueduct hearing loss. METHODS: A rater reproducibility study. Three consultant radiologists independently measured previously reported MRI ED & ES biomarkers (ED midpoint width, maximal ED diameter closest to the vestibule, ES length, ES width and presence of ES signal heterogeneity) and presence of incomplete partition Type 2 from 80 ears (T2 weighted axial MRI). Interclass correlation coefficients (ICC) and Gwet's Agreement Coefficients (AC) were generated to give a measure of reproducibility for both continuous and categorical feature measures respectively. RESULTS: ES length, width and sac signal heterogeneity showed adequate reproducibility (ICC 95% confidence intervals 0.77-0.95, Gwet's AC for sac heterogeneity 0.64). When determining ED midpoint width, measurements from multiple raters are required for "good" reliability (ICC 95% CI 0.75-0.89). Agreement on the presence of incomplete partition Type 2 ranged from "moderate" to "substantial". CONCLUSIONS: Regarding MR imaging, the opinion of multiple expert raters should be sought when determining the presence of an enlarged ED defined by midpoint width. ED midpoint, ES length, width and signal heterogeneity have adequate reproducibility to be further explored as clinical predictors for audiological phenotype. ADVANCES IN KNOWLEDGE: We report which ED & ES biomarkers are reproducibly measured. Researchers can confidently utilise these specific biomarkers when modelling progressive hearing loss associated with enlarged vestibular aqueduct.

Atypical imaging presentation of herpes simplex virus encephalitis in paediatric immunocompromised oncology patients.

INTRODUCTION: We aim to assess the imaging manifestations of brain involvement in paediatric immunocompromised patients with haematological malignancies on chemotherapy presenting with encephalitis and positive HSV CSF PCR. We also aim to determine whether our findings are similar or different to those described in literature for paediatric patients in general. METHODS: A retrospective study was performed in paediatric ALL/lymphoma patients on chemotherapy, and cases with positive CSF HSV-PCR with at least one head MRI scan were included. On imaging, location(typical/atypical), post-contrast enhancement and haemorrhage/diffusivity/gliosis were evaluated. RESULT: A total of 28 scans were included in study from 16 patients fulfilling inclusion criteria, 12 (75%) HSV-1 and 4 (25%) HSV-2. Of the 16 initial scans (CT n = 10, MRI n = 6), 11 were normal (CT = 7, MRI = 4). Fourteen patients had follow-up MRI, of which two had normal scans. On the abnormal initial scan (5/16), only 20% had typical medial temporal/inferomedial frontal/cingulate involvement. Most had frontal (80%), parietal (60%) and non-medial temporal (40%) lesions. Abnormal diffusivity/haemorrhage was absent in all, and postcontrast enhancement was seen in 20%. On follow-up, more patients (33%) had typical medial temporal/inferomedial frontal/cingulate involvement. Widespread atypical site involvement of frontoparietal (75%), thalamus (58%), non-medial temporal (50%), occipital/basal ganglia (33%) and cerebellum (8%) was noted. Most lesions were cortical (91%)/subcortical (75%) with few periventricular lesions (58%). Few showed abnormal diffusivity (16%), post-contrast parenchymal enhancement/haemorrhage (8%), post-contrast meningeal enhancement (25%) and gliosis (16%). CONCLUSION: Immunocompromised paediatric patients with haematological malignancies have widespread atypical brain involvement in herpes simplex encephalitis with lack of diffusion restriction and post-contrast enhancement, likely due to haematogenous spread of HSV across the blood-brain barrier, lack of cellular immunity and limited inflammatory cytokine response.