Magnetic resonance imaging of pediatric brain tumors: state of the art

MRI Protocol for Pituitary Assessment in Children with Growth or Puberty Disorders-Is Gadolinium Contrast Administration Actually Needed?

The aim of this study was to assess the diagnostic value of non-contrast pituitary MRI in children with growth or puberty disorders (GPDs) and to determine the criteria indicating the necessity to perform post-contrast examination. A retrospective study included re-analysis of 567 contrast-enhanced pituitary MRIs of children treated in a tertiary reference center. Two sets of sequences were created from each MRI examination: Set 1, including common sequences without contrast administration, and Set 2, which included common pre- and post-contrast sequences (conventional MRI examination). The differences in the visibility of pituitary lesions between pairs of sets were statistically analyzed. The overall frequency of Rathke’s cleft cysts was 11.6%, ectopic posterior pituitary 3.5%, and microadenomas 0.9%. Lesions visible without contrast administration accounted for 85% of cases. Lesions not visible before and diagnosed only after contrast injection accounted for only 0.18% of all patients. Statistical analysis showed the advantage of the antero-posterior (AP) pituitary dimension over the other criteria in determining the appropriateness of using contrast in pituitary MRIs. The AP dimension was the most significant factor in logistic regression analysis: OR = 2.23, 95% CI, 1.35–3.71, p-value = 0.002, and in ROC analysis: AUC: 72.9% with a cut-off value of 7.5 mm, with sensitivity/specificity rates of 69.2%/73.5%. In most cases, the use of gadolinium-based contrast agent (GBCA) in pituitary MRI in children with GPD is unnecessary. The advantages of GBCA omission include shortening the time of MRI examination and of general anesthesia; saving time for other examinations, thus increasing the availability of MRI for waiting children; and acceleration in their further clinical management.

Hypothalamic Pilomyxoid Astrocytoma in a Child with Lipodystrophy

Pilomyxoid astrocytoma is a rare form of pediatric CNS malignancy first classified in 2007 by the World Health Organization. The tumors are similar to pilocytic astrocytomas, sharing both some imaging and histologic traits. However, pilomyxoid astrocytomas portend a more ominous prognosis, with more aggressive local tendencies and a greater proclivity for leptomeningeal spread. Although tissue sampling is ultimately required to differentiate pilocytic astrocytomas and pilomyxoid astrocytomas, some imaging features can be used to suggest a pilomyxoid astrocytoma, including homogeneous enhancement, leptomeningeal seeding, and lack of intratumoral cysts. In this article, a case of a hypothalamic pilomyxoid astrocytoma is described, in which the presenting disorder was profound generalized lipodystrophy. The aforementioned imaging characteristics of pilomyxoid astrocytomas are reviewed, as are the pathologic features of such tumors, including their angiocentric cellular arrangement and myxoid background.

MRI Phenotype of RELA-fused Pediatric Supratentorial Ependymoma

PURPOSE

Epigenetic profiling has recently identified clinically and molecularly distinct subgroups of ependymoma. The 2016 World Health Organization (WHO) classification recognized supratentorial ependymomas (ST-EPN) with REL-associated protein/p65 (RELA) fusion as a clinicopathological entity. These tumors represent 70% of pediatric ST-EPN characterized by recurrent C11orf95-RELA fusion transcripts, which lead to pathological activation of the nuclear factor 'kappa-light-chain-enhancer' of activated B-cells (NF-κB) signaling pathway. Cyclin-dependent kinase inhibitor 2A (CDKN2A) inactivation has also been reported to correlate with poor prognosis. Here, we systematically describe magnetic resonance imaging (MRI) characteristics of RELA-fused ST-EPN, with respect to CDKN2A deletion status.

METHODS

Our cohort of patients with ST-EPN (n = 57) was obtained from the database of the German Brain Tumor Reference Center of the German Society for Neuropathology and Neuroanatomy (DGNN), and tumors were diagnosed according to the 2016 WHO classification. Molecular characterization identified 47 RELA-fused tumors. We analyzed the preoperative MRI according to standardized criteria, and comparison was performed between CDKN2A altered (n = 21) and CDKN2A wild type (n = 26) tumors.

RESULTS

The RELA-fused ST-EPN showed a spectrum of predominantly hemispheric tumors with cysts and necrosis. Statistical analysis on CDKN2A status revealed significant differences in terms of younger manifestation age (p =0.002) and more intratumoral hemorrhage in T2-weighted imaging (T2WI) (p =0.010) in wild type tumors; however, the location was not a parameter for differentiation.

CONCLUSION

This study first provides comprehensive MRI data for RELA-fused ST-EPN as a distinct entity, with further interest on CDKN2A genomic status. Patient stratification by morphological MRI alone seems difficult at present. The results may support ongoing research in ST-EPN within the framework of the radiogenomics concept.

Systematic comparison of MRI findings in pediatric ependymoblastoma with ependymoma and CNS primitive neuroectodermal tumor not otherwise specified

BACKGROUND

Ependymoblastoma (EBL), ependymoma (EP), and primitive neuroectodermal tumors of the central nervous system not otherwise specified (CNS-PNET NOS) are pediatric brain tumors that can be differentiated by histopathology in the clinical setting. Recently, we described specific MRI features of EBL. In this study, we compare standardized MRI characteristics of EBL with EP and CNS-PNET NOS in a series comprising 22 patients in each group.

METHODS

All 66 centrally reviewed cases were obtained from the database of the German multicenter HIT trials. We systematically analyzed the initial MRI scans at diagnosis according to standardized criteria, and paired comparison was performed for EBL and EP, as well as for EBL and CNS-PNET NOS.

RESULTS

We found differences between EBL and EP regarding age at diagnosis, MR signal intensity, tumor margin and surrounding edema, presence and size of cysts, and contrast enhancement pattern. Although MRI appearance of EBL shares many features with CNS-PNET NOS, we revealed significant differences in terms of age at diagnosis, tumor volume and localization, tumor margins, edema, and contrast enhancement.

CONCLUSION

This is the first study that systematically compares multiple parameters of MRI in pediatric EBL with findings in EP and CNS-PNET NOS. Although a definite differentiation by means of MRI alone might not be feasible in the individual case, we identify significant differences between these tumor entities.

MRI characteristics of ependymoblastoma: results from 22 centrally reviewed cases

BACKGROUND AND PURPOSE

Ependymoblastoma is a malignant embryonal tumor that develops in early childhood and has a dismal prognosis. Categorized by the World Health Organization as a subgroup of CNS-primitive neuroectodermal tumor, ependymoblastoma is histologically defined by "ependymoblastic rosettes." Because it is so rare, little is known about specific MR imaging characteristics of ependymoblastoma. We systematically analyzed and discussed MR imaging features of ependymoblastoma in a series of 22 consecutive patients.

MATERIALS AND METHODS

Ependymoblastoma cases were obtained from the database of the German multicenter HIT trials between 2002 and 2013. All cases within this study were centrally reviewed for histopathology, MR imaging findings, and multimodal therapy. For systematic analysis of initial MR imaging scans at diagnosis, we applied standardized criteria for reference image evaluation of pediatric brain tumors.

RESULTS

Ependymoblastomas are large tumors with well-defined tumor margins, iso- to hyperintense signal on T2WI, and diffusion restriction. Contrast enhancement is variable, with a tendency to mild or moderate enhancement. Subarachnoid spread is common in ependymoblastoma but can be absent initially. There was a male preponderance (1.75:1 ratio) for ependymoblastoma in our cohort. Mean age at diagnosis was 2.1 years.

CONCLUSIONS

With this study, we add the largest case collection to the limited published database of MR imaging findings in ependymoblastoma, together with epidemiologic data. However, future studies are needed to systematically compare MR imaging findings of ependymoblastoma with other CNS-primitive neuroectodermal tumors and ependymoma, to delineate imaging criteria that might help distinguish these pediatric brain tumor entities.

Trends in childhood brain tumor incidence, 1973-2009

In the mid-1980s, there was a rise in incidence rates of childhood brain tumors (CBT) in the United States that appeared to stabilize at a higher rate in the early 1990 s. An updated analysis of the pattern of CBT over the past 2 decades, with commentary on whether the elevated incidence rate has continued, is past due. We used Surveillance, Epidemiology and End Results (SEER) data to examine trends in incidence of CBT from 1973 through 2009. We examined age-adjusted incidence rates (AAIRs) and secular trends for all malignant brain tumors combined (SEER classification) by histologic tumor type and anatomic site. The incidence of CBT remained stable from 1987 to 2009 [annual percent change (APC) = 0.10; 95 % confidence intervals (CI) -0.39 to 0.61] with an AAIR for all CBT of 3.32 (95 % CI 3.22-3.42). The stability of rates in these two decades contrast the change that occurred in the mid-1980s (1983-1986), when the incidence of CBT increased by 53 % (APC = 14.06; 95 % CI 4.05-25.0). From 1983 to 1986, statistically significant rate increases were observed for pilocytic astrocytoma, PNET/medulloblastoma, and mixed glioma. Further, the rate of increase in pilocytic astrocytoma was similar to the rate of decrease for astrocytomas NOS from 1981 to 2009, suggesting a change from a more general to more specific classification. After the increase in rates in the mid-1980s, rates of CBT over the past two decades have stabilized. Changes in incidence rates of subtypes of tumors over this time period reflect changes both in classification of CBT and in diagnostic techniques.

Conventional and advanced MRI features of pediatric intracranial tumors: supratentorial tumors

OBJECTIVE. Our objective is to review the imaging characteristics and applications of conventional and advanced neuroimaging techniques of supratentorial intracranial masses in the pediatric population. Specifically, we review astrocytomas, oligodendrogliomas, primary neuroectodermal tumors, dysembryoplastic neuroepithelial tumors, gangliogliomas, arachnoid cysts, and choroid plexus and pineal region masses. CONCLUSION. Advanced imaging methods, such as MR spectroscopy, perfusion MRI, functional MRI, diffusion-tensor imaging, and tractography, help develop a more accurate differential diagnosis and aid in planning tumor treatment.

Conventional and advanced MRI features of pediatric intracranial tumors: posterior fossa and suprasellar tumors

OBJECTIVE

In this article, we review the most common posterior fossa and suprasellar intracranial neoplasms in the pediatric population. We briefly discuss basic MRI concepts used in the initial evaluation of a pediatric brain tumor and then discuss sophisticated MRI techniques that give insight into the physiology and chemical makeup of these tumors to help the radiologist make a more specific diagnosis.

CONCLUSION

Diagnosis and treatment of pediatric CNS tumors necessitate a multi-disciplinary approach and require expertise and diligence of all parties involved. Imaging is an essential component has evolved greatly over the past decade. We are becoming better at making a preoperative diagnosis of that tumor type, detecting recurrence, and guiding surgical management to avoid injury to vital brain structures.

Diffuse hemispheric dysembryoplastic neuroepithelial tumor: a new radiological variant associated with early-onset severe epilepsy

The authors describe the clinical and radiological features in 3 children with a diffuse hemispheric dysembryoplastic neuroepithelial tumor (DNET) presenting with severe epilepsy and a previously unreported and characteristic MR imaging appearance. The DNET is a well-recognized cause of focal epilepsy, usually with a very good response to resection. These tumors are usually intracortical, and most commonly arise in the temporal lobe or frontal lobes. Radiologically they are usually sharply demarcated, and show little contrast enhancement. Three children (2 boys and 1 girl) presented at 14, 17, and 22 months of age with epileptic seizures. The seizures were focal motor or complex focal. One patient had epileptic spasms. The response to antiepileptic drug therapy was poor. Motor and cognitive development was delayed in all patients. One patient developed a severe epileptic encephalopathy, with regression of motor and cognitive skills. Her electroencephalogram obtained at that time showed hypsarhythmia. Admission MR imaging showed a diffuse unilateral abnormality involving frontal, temporal, and parietal lobes with little or no mass effect. There was involvement of both gray and white matter, with a striking sparing of the internal capsule in spite of apparent tumor throughout the basal ganglia and thalamus. In 2 patients there was prominent expansion of cortical gyri by tumor. In 1 child the initial radiological diagnosis was a middle cerebral artery infarct. On subsequent review the radiological diagnosis was thought to be low-grade glioma in all patients. The first patient underwent 2 limited resections involving the temporal lobe. He has continued to have poorly controlled seizures and severe behavioral and cognitive problems. The other patients had subtotal resection to the level of the internal capsule. One patient is currently seizure free 24 months postsurgery, but remains cognitively impaired. The patient in Case 3 is having some seizures 3.5 years postsurgery and remains hemiplegic, but the regression has reversed and she is making steady developmental progress. The pathological specimens showed the typical features of a DNET in all cases. This striking radiological pattern has not previously been described as a feature of a DNET. Recognition of this radiological pattern in young children with epilepsy will allow early consideration for resection, which may lead to improved long-term cognitive outcome.

Intracranial germinoma: clinical and MRI findings in 56 patients

INTRODUCTION

Intracranial germinoma is a rare malignant tumor, only constituting 0.5-2.0% of all primary intracranial tumors. It usually occurs in children and young adults, it is highly sensitive to radiotherapy or/and chemotherapy, and is potentially curable without operation. To make correct pre-operative diagnosis and spare surgical intervention, we retrospectively reviewed 56 patients in our hospital, and presented clinical findings and MRI characteristics.

MATERIALS AND METHODS

We reviewed medical records and magnetic resonance imaging (MRI) of 56 patients. Information regarding sex, age at diagnosis, clinical presentation, duration of symptom, and associated neurologic deficits was noted. The tumor location, number of metastasis, size, margin, involved tissues, and characteristics of signal intensity on MRI were analyzed by two experienced radiologists, respectively.

RESULTS

In the series, 57% of intracranial germinoma was located in pineal region, 32% in suprasellar region, and 9% in basal ganglia region. One patient was found germinoma with synchronous lesions in pineal and suprasellar region. Sixty-three percent of patients were male in pineal region, 39% and 100%, respectively, in suprasellar region and basal ganglia region. Age at diagnosis ranged from 3 to 21 years (mean, 12.5 years) with a peak between 10 and 18 years.

CONCLUSIONS

Intracranial germinoma has some features in terms of age, sex, clinical presentation, and MRI. These features are in favor of pre-operative diagnosis and thus make for good prognosis.

Neuroimaging of pediatric brain tumors: from basic to advanced magnetic resonance imaging (MRI)

In this review, the basic magnetic resonance concepts used in the imaging approach of a pediatric brain tumor are described with respect to different factors including understanding the significance of the patient's age. Also discussed are other factors directly related to the magnetic resonance scan itself including evaluating the location of the tumor, determining if the lesion is extra-axial or intra-axial, and evaluating the contrast characteristics of the lesion. Of note, there are key imaging features of pediatric brain tumors, which can give information about the cellularity of the lesion, which can then be confirmed with advanced magnetic resonance imaging (MRI) techniques. The second part of this review will provide an overview of the major advanced MRI techniques used in pediatric imaging, particularly, magnetic resonance diffusion, magnetic resonance spectroscopy, and magnetic resonance perfusion. The last part of the review will provide more specific information about the use of advanced magnetic resonance techniques in the evaluation of pediatric brain tumors.

Approach to pediatric epilepsy surgery: State of the art, Part II: Approach to specific epilepsy syndromes and etiologies

The second of this 2-part review depicts the specific approach to the common causes of pediatric refractory epilepsy amenable to surgery. These include tumors, malformations due to abnormal cortical development, vascular abnormalities and certain epileptic syndromes. Seizure freedom rates are high (usually 60-80%) following tailored focal resection, lesionectomy, and hemispherectomy. However, in patients in whom the epileptogenic zone overlaps with unresectable eloquent cortex, and in certain epileptic syndromes, seizure freedom may not be achievable. In such cases, palliative procedures such as callosotomy, multiple subpial transections and vagus nerve stimulation can achieve reduction in seizure severity but rarely seizure freedom. Integration of the new imaging techniques and the concepts of neuronal plasticity, the epileptogenic lesion, the ictal onset, symptomatogenic, irritative, and epileptogenic zones is an expanding and dynamic process that will allow us, in the future, to better decide on the surgical approach of choice and its timing.

A novel method for analyzing DSCE-images with an application to tumor grading

OBJECTIVES

(a) The development of a novel analysis method, named Dynamic pixel intensity Histogram Analysis (DHA) allowing for pixel intensity-histogram-model-parameter fitting of arbitrary-shaped regions defined in dynamic-susceptibility-contrast-enhanced (DSCE) difference MR-image time-series, and (b) its prospective application and evaluation for glioma grading.

MATERIALS AND METHODS

For each difference-image, pixel intensity histograms of arbitrary-shaped ROIs were computed and fitted using the Levenberg-Marquardt algorithm. Time-dependent histogram center-position- and width-parameters are computed during bolus-passage. The method was applied to 25 patients with low and high grade gliomas.

RESULTS

During bolus outflow-time, histogram-center-position-parameter and histogram-width-parameter reach highest significance levels and discriminate gliomas of different grades. The histogram center-position-parameter discriminated grade-II from grade-III, grade-II from grade-IV but not grade-III from grade-IV. The observed histogram width-parameters discriminated grade-II from grade-III (P < 0.00022), grade-II from grade-IV (P <8.3 10), and grade-III from grade-IV (P < 0.00063).

CONCLUSIONS

DHA is a easy-to-use method for glioma grading; the histogram width parameter is best indicator for histologic grade.

Brain MRI: tumor evaluation

The designation "brain tumors" is commonly applied to a wide variety of intracranial mass lesions that are distinct in their location, biology, treatment, and prognosis. Since many of these lesions do not arise from brain parenchyma, the more appropriate term would be "intracranial tumors." The term "tumor" is used to include both neoplastic and non-neoplastic mass lesions, and should be considered in its broadest sense to simply indicate a space-occupying mass. This review describes an imaging-based approach for evaluating intracranial tumors. Conventional MRI is discussed in the setting of a regional classification system. This system provides a framework for analysis, and imaging clues can then be applied to narrow the differential possibilities. Emphasis is placed on advanced MRI techniques and their utility for deciphering common diagnostic problems.

Advanced neuroimaging of pediatric brain tumors: MR diffusion, MR perfusion, and MR spectroscopy

This article highlights the MR imaging techniques of MR perfusion, MR diffusion, and MR spectroscopy in the evaluation of the child with a pediatric brain tumor. These techniques are complementary to conventional MR imaging in providing tumor physiologic information useful for diagnosis and therapy.

Imaging findings in primary intracranial atypical teratoid/rhabdoid tumors

BACKGROUND

Intracranial atypical teratoid/rhabdoid tumors (AT/RT) are rare and extremely aggressive neoplasms seen primarily in childhood. Imaging features are often considered non-specific. However, correct diagnosis of AT/RT is important because these tumors have a markedly different clinical prognosis and require more aggressive therapy.

OBJECTIVE

To determine the imaging features of AT/RT.

MATERIALS AND METHODS

We retrospectively analyzed imaging findings in 11 patients with primary intracranial AT/RT presenting over a period of 5 years. CT (n=11), MR (n=7), clinical (n=11) and pathological (n=11) features were evaluated. FISH analysis showing monosomy of chromosome 22 (absence of bcr 22q11 locus) was available for three patients. Immunohistochemical staining for INI-1 (BAF47) was performed on all tumors.

RESULTS

There were 11 patients, 6 boys and 5 girls. The age of presentation varied from 1 month to 15 years (average age 3 years 8 months). Six tumors were located in the posterior fossa and five in the supratentorial compartment. The tumors showed a hyperdense solid component (64%) that showed moderate to marked enhancement with contrast medium. On MR imaging, the predominant signal pattern was isointensity on T1-weighted images (57%) and T2 shortening with heterogeneity on T2-weighted images (86%). All tumors were large in size (average 4.2 x 3.7 cm), and there was a tendency for calcification (36%), hemorrhage (46%), necrosis (46%) and perifocal edema (100%). There was also a high tendency for subarachnoid dissemination, with five patients (46%) demonstrating brain and/or spinal metastasis. At follow-up (n=7), six patients showed local recurrence. At the time of recurrence, all these patients showed extensive leptomeningeal spread of the disease in both intracranial and intraspinal compartments.

CONCLUSION

There are no specific imaging features for intracranial AT/RT. But a high tendency toward large size, a hyperdense solid component on CT scan with calcification, hemorrhage, necrosis and subarachnoid spread suggest that this tumor should be considered in the differential diagnosis of large pediatric intracranial tumors.

Dysphagia outcomes in patients with brain tumors undergoing inpatient rehabilitation

The purpose of this retrospective study was to compare functional dysphagia outcomes following inpatient rehabilitation for patients with brain tumors with that of patients following a stroke. Group 1 (n = 24) consisted of consecutive admissions to the brain injury program with the diagnosis of brain tumor and dysphagia. Group 2 (n = 24) consisted of matched, consecutive admissions, with the diagnosis of acute stroke and dysphagia. Group 2 was matched for age, site of lesion, and initial composite cognitive FIM score. The main outcome measures for this study included the American Speech-Language-Hearing Association (ASHA) National Outcome Measurement System (NOMS) swallowing scale, length of stay, hospital charges, and medical complications. Results showed that swallowing gains made by both groups as evaluated by the admission and discharge ASHA NOMS levels were considered to be statistically significant. The differences for length of stay, total hospital charges, and speech charges between the two groups were not considered to be statistically significant. Three patients in the brain tumor group (12.5%) demonstrated dysphagia complications of either dehydration or pneumonia during their treatment course as compared to 0% in the stroke group. This study confirms that functional dysphagia gains can be achieved for patients with brain tumors undergoing inpatient rehabilitation and that they should be afforded the same type and intensity of rehabilitation for their swallowing that is provided to patients following a stroke.