Diagnostic and management roles of FDG PET/CT imaging in post-transplant lympho-proliferation in pediatric heart transplantation.

BACKGROUND: Post-transplant lymphoproliferative disorder (PTLD) is a serious complication of pediatric heart transplant (PHTx). 18F-FDG PET/CT has been used to differentiate early lympho-proliferation from more advanced PTLD. We report our experience with PET/CT in the management of PTLD following PHTx. METHODS: This was a retrospective study of 100 consecutive PHTx recipients at our institution between 2004 and 2018. Patients who underwent PET/CT or conventional CT scans to evaluate for PTLD or high Epstein-Barr viral load were included. RESULTS: Males, eight females. Median age at transplant was 3.5 months (IQR = 1.5-27.5). Median age at PTLD diagnosis was 13.3 years (IQR = 9.2-16.1). Median time between transplant and PTLD diagnosis was 9.5 (IQR = 4.5-15) years. Induction agents were used in 12 patients (50%): Thymoglobulin (N = 9), anti-IL2 (N = 2), and Rituximab (N = 1). Eighteen patients (75%) had PET/CT, of whom 14 had 18FDG-avid PTLD. Six had conventional CT. Nineteen patients (79.2%) had diagnostic biopsy confirmation of PTLD, and 5 (20.8%) had excisional biopsies. Two patients had Hodgkin's lymphoma; nine had monomorphic PTLD; eight had polymorphic PTLD; five were classified as other. Nine patients had monomorphic PTLD, including seven with diffuse large cell lymphoma (DLBC) and one with T cell lymphoma. The majority (16/24) had multi-site involvement at PTLD diagnosis, and PET/CT showed that 31.3% (5/16) had easily accessible subcutaneous nodes. Seventeen patients (overall survival 71%) underwent successful treatment without recurrence of PTLD. Of seven deaths (7/24, 29%), five had DLBC lymphoma, one had polymorphic PTLD and one had T-cell lymphoma. CONCLUSION: PET-CT allowed simultaneous anatomical and functional assessment of PTLD lesions, while guiding biopsy. In patients with multiple lesions, PET/CT revealed the most prominent and active lesions, improving diagnostic accuracy.

Advances in Imaging Modalities for Pediatric Brain and Spinal Cord Tumors.

BACKGROUND: Neuroimaging has evolved from anatomical imaging toward a multi-modality comprehensive anatomical and functional imaging in the past decades, important functional data like perfusion-weighted imaging, permeability imaging, diffusion-weighted imaging (DWI), and diffusion tensor imaging (DTI), tractography, metabolic imaging, connectomics, event-related functional imaging, resting state functional imaging, and much more is now being offered. SUMMARY: Precision diagnostics has proven to be essential for precision treatment. Many minimal invasive techniques have been developed, taking advantage of digital subtraction angiography and interventional neuroradiology. Furthermore, intraoperative CT and/or MRI and more recently MR-guided focused ultrasound have complemented the diagnostic and therapeutic armamentarium. KEY MESSAGES: In the current manuscript, we discuss standard imaging sequences including advanced techniques like DWI, DTI, susceptibility-weighted imaging, and 1H magnetic resonance spectroscopy, various perfusion weighted imaging approaches including arterial spin labeling, dynamic contrast enhanced imaging, and dynamic susceptibility contrast imaging. Pre-, intra, and postoperative surgical imaging including visualize imaging will be discussed. The value of connectomics will be presented for its value in neuro-oncology. Minimal invasive therapeutic possibilities of interventional neuroradiology and image-guided laser ablation and MR-guided high-intensity-focused ultrasound will be presented for treatment of pediatric brain and spinal cord tumors. Finally, a comprehensive review of spinal cord tumors and matching neuropathology has been included.

Eosinophilic Meningitis: Eleven-Year Experience at Texas Children's Hospital.

Eosinophilic meningitis can be caused by various etiologies and is reported mostly in tropical climates. The diagnosis is rare in the continental US, presenting challenges for management. Following a case of pediatric eosinophilic meningitis, we reviewed our 11-year experience with this diagnosis at a large US children's hospital.

Another Piece of the Puzzle of Anomalous Connectivity in Joubert's Syndrome.

We report on the conventional and diffusion tensor imaging (DTI) findings of a 2-year-old child with clinical presentation of Joubert's Syndrome (JS) and brainstem structural abnormalities as depicted by neuroimaging.Conventional magnetic resonance imaging (MRI) showed a "molar tooth" configuration of the brainstem. A band-like formation coursing in an apparent axial plane anterior to the interpeduncular fossa was noted and appeared to partially cover the interpeduncular fossa.DTI maps and three-dimensional (3D) tractography demonstrated a prominent red-encoded white matter bundle anterior to the midbrain. Probable aberrant course of the bilateral corticospinal tracts (CST) was also depicted. Absence of the decussation of the superior cerebellar peduncles and elongated thickened, horizontal superior cerebellar peduncle (SCP) reflecting the molar tooth sign were also shown.Our report and the review of the published cases suggest that DTI and tractography may be very helpful to differentiate between interpeduncular heterotopias and similarly located white matter bundles corroborating the underlying etiology of axonal guidance disorders in the complex group of ciliopathies including JS. Our case represents an important additional puzzle piece to explore the variability of these ciliopathies.

Radiologic and clinical outcome of isolated fourth ventricle following post-hemorrhagic hydrocephalus in children.

PURPOSE: Few studies report radiologic and clinical outcome of post-hemorrhagic isolated fourth ventricle (IFV) with focus on surgical versus conservative management in neonates and children. Our aim is to investigate differences in radiological and clinical findings of IFV between patients who had surgical intervention versus patients who were treated conservatively. METHODS: A retrospective analysis of patients diagnosed with IFV was performed. Data included demographics, clinical exam findings, surgical history, and imaging findings (dilated FV extent, supratentorial ventricle dilation, brainstem and cerebellar deformity, tectal plate elevation, basal cistern and cerebellar hemisphere effacement, posterior fossa upward/downward herniation). RESULTS: Sixty-four (30 females) patients were included. Prematurity was 94% with 90% being < 28 weeks of gestation. Mean age at first ventricular shunt was 3.6 (range 1-19); at diagnosis of IFV, post-lateral ventricular shunting was 26.2 (1-173) months. Conservatively treated patients were 87.5% versus 12.5% treated with FV shunt/endoscopic fenestration. Severe FV dilation (41%), severe deformity of brainstem (39%) and cerebellum (47%) were noted at initial diagnosis and stable findings (34%, 47%, and 52%, respectively) were seen at last follow-up imaging. FV dilation (p = 0.0001) and upward herniation (p = 0.01) showed significant differences between surgery versus conservative management. No other radiologic or clinical outcome parameters were different between two groups. CONCLUSION: Only radiologic outcome results showed stable or normal FV dilation and stable or decreased upward herniation in the surgically treated group.

Characterization of Visual Pathway Abnormalities in Infants With Congenital Zika Syndrome Using Computed Tomography and Magnetic Resonance Imaging.

BACKGROUND: Severe visual impairment is present in nearly all infants with congenital Zika syndrome (CZS); however, ocular abnormalities are present only in a subset of these infants. The purpose of this study was to characterize the visual pathway abnormalities seen on computed tomography (CT) and MRI scans in infants with CZS. METHODS: Preliminary neuroimaging information was obtained from a referred sample of 105 infants with clinical and epidemiologic data consistent with CZS in the Pernambuco state of Brazil. Subjects were excluded if Zika virus infection was not confirmed by serologic or cerebrospinal fluid studies or if images were nondiagnostic. Of the 105 subjects initially screened, head CT images adequate for interpretation were available for 54, and brain MRI images adequate for interpretation were available for 20. Four patients had both CT and MRI images. Magnetic resonance imaging and CT scans from infants with CZS were systematically reviewed for globe malformations, optic nerve and chiasmal atrophy, occipital cortical volume loss, white matter abnormalities, ventriculomegaly, and calcifications. Neuroimaging findings were correlated with measures of visual function and with ocular examinations in these infants. RESULTS: Thirty-three males and 37 females were included in the analysis. The mean age of the infants at the time of neuroimaging was 16.0 weeks (range 0 days-15.5 months), and the mean gestational age at the time of birth was 38 weeks. All patients were from the Pernambuco state of Brazil. Overall, 70 of 74 (95%) scans showed occipital volume loss, whereas 9 (12%) showed optic nerve atrophy, 3 (4%) showed chiasmal atrophy, and 1 (1%) showed an ocular calcification. Sixty-two of the infants underwent ophthalmologic examinations. A total of 34 (55%) infants had at least one documented structural ocular abnormality, and 26 (42%) had at least one structural ocular abnormality documented in both eyes. Of those with available visual acuity data, all had visual impairment. Among those with visual impairment and normal eye examinations, 100% had visual pathway abnormalities on neuroimaging, including 100% with occipital cortical volume loss, 8% with optic nerve atrophy, and 8% with chiasmal atrophy. CONCLUSION: Our results suggest that cortical visual impairment related to structural abnormalities of the occipital cortex is likely an important cause of visual impairment in children with CZS with normal eye examinations.

The structural connectome in children: basic concepts, how to build it, and synopsis of challenges for the developing pediatric brain.

PURPOSE: The structural connectome is a comprehensive structural description of the network of elements and connections forming the brain. In recent years, this framework has progressively been used to investigate the pediatric brain. METHODS: We discuss the different steps and emphasize key technical aspects required for the successful reconstruction, analysis, and visualization of the pediatric structural connectome using current state-of-the-art neuroimaging and post-processing techniques. RESULTS: The two key components of structural connectome are a node (a cortical region obtained with high-resolution anatomical imaging) and an edge (structural association between cortical regions, defined with tractography). After delineation of nodes and edges, an association matrix can be generated by compiling all pairwise associations between nodes and applying a threshold to produce a binary adjacency matrix. Several measures can be used to characterize the topological architecture of the brain's networks. Finally, we provide an overview of various visualization methods of the structural connectome in children. CONCLUSION: The human connectome is the culmination of more than a century of conceptual and methodological innovation. Biological substrates of brain development such as cortical gyration and myelination challenge the acquisition, reconstruction, and analysis of structural connectome in children and require specific considerations compared to adults.

The impact of surgical strategies on outcomes for pediatric chronic pancreatitis.

PURPOSE: To review our institutional experience in the surgical treatment of pediatric chronic pancreatitis (CP) and evaluate predictors of long-term pain relief. METHODS: Outcomes of patients ≤21 years surgically treated for CP in a single institution from 1995 to 2014 were evaluated. RESULTS: Twenty patients underwent surgery for CP at a median of 16.6 years (IQR 10.7-20.6 years). The most common etiology was pancreas divisum (n = 7; 35%). Therapeutic endoscopy was the first-line treatment in 17 cases (85%). Surgical procedures included: longitudinal pancreaticojejunostomy (n = 4, 20%), pancreatectomy (n = 9, 45%), total pancreatectomy with islet autotransplantation (n = 2; 10%), sphincteroplasty (n = 2, 10%) and pseudocyst drainage (n = 3, 15%). At a median follow-up of 5.3 years (IQR 4.2-5.3), twelve patients (63.2%) were pain free and five (26.3%) were insulin dependent. In univariate analysis, previous surgical procedure or >5 endoscopic treatments were associated with a lower likelihood of pain relief (OR 0.06; 95% CI 0.006-0.57; OR 0.07; 95%, CI 0.01-0.89). However, these associations were not present in multivariate analysis. CONCLUSION: In children with CP, the step-up practice including a limited trial of endoscopic interventions followed by surgery tailored to anatomical abnormalities and gene mutation status is effective in ensuring long-term pain relief and preserving pancreatic function.

Diffusion tensor imaging: A biomarker of outcome in Krabbe's disease.

Krabbe's disease is a rare autosomal recessive lysosomal disorder resulting from deficiency of ß-galactocerebrosidase that affects primarily cerebral white matter and peripheral nerves. Conventional magnetic resonance imaging (MRI) is sensitive to changes in white matter myelination, but its assessment is based purely on qualitative, visual inspection, and it is subject to interobserver variability and open to reader bias. Diffusion tensor imaging (DTI) is an advanced MRI technique that provides quantitative information about the microscopic structural organization of the white matter and changes in cell density and myelination, and it is a suitable MRI tool for studying Krabbe's disease. This Review discusses the available studies on the application of quantitative DTI analysis to assess white matter changes in patients with Krabbe's disease. Quantitative analysis of DTI scalars, especially radial diffusivity and fractional anisotropy, has been shown to be a sensitive in vivo biomarker of white matter microstructural damage in Krabbe's disease, to detect early white matter injury in asymptomatic neonates with Krabbe's disease, to predict motor and cognitive functions after hematopoietic stem cell transplantation (HSCT), and to serve as a measurement for monitoring effects of HSCT on white matter development in Krabbe's disease. © 2016 Wiley Periodicals, Inc.

Pancreatic surgery for tumors in children and adolescents.

PURPOSE: Pancreatic neoplasms are uncommon in children. This study sought to analyze the clinical and pathological features of surgically resected pancreatic tumors in children and discuss management strategies. METHODS: We conducted a retrospective review of patients ≤21 years with pancreatic neoplasms who underwent surgery at a single institution between 1995 and 2015. RESULTS: Nineteen patients were identified with a median age at operation of 16.6 years (IQR 13.5-18.9). The most common histology was solid pseudopapillary neoplasm (SPN) (n = 13), followed by pancreatic neuroendocrine tumor (n = 3), serous cystadenoma (n = 2) and pancreatoblastoma (n = 1). Operative procedures included formal pancreatectomy (n = 17), enucleation (n = 1) and central pancreatectomy (n = 1). SPNs were noninvasive in all but one case with perineural, vascular and lymph node involvement. Seventeen patients (89.5 %) are currently alive and disease free at a median follow-up of 5.7 (IQR 3.7-10.9) years. Two patients died: one with metastatic insulinoma and another with SPN who developed peritoneal carcinomatosis secondary to a concurrent rectal adenocarcinoma. CONCLUSIONS: Pediatric pancreatic tumors are a heterogeneous group of neoplastic lesions for which surgery can be curative. SPN is the most common histology, is characterized by low malignant potential and in selected cases can be safely and effectively treated with a tissue-sparing resection and minimally invasive approach.

Structural connectivity analysis reveals abnormal brain connections in agenesis of the corpus callosum in children.

OBJECTIVES: Structural connectivity analysis is an ideal tool to study connections in brain malformations. We aimed to characterize the topological network measures and study sub-networks in children with agenesis of the corpus callosum (AgCC). We hypothesized a more segregated structural network in children with AgCC. METHODS: Structural connectivity analysis including topology analysis and network-based-statistics was applied in children with AgCC and age-matched controls. Probabilistic-tractography and brain segmentation into 108 regions were performed. For controls, structural connectivity has been analyzed after excluding the callosal connections ('virtual callosotomy'). RESULTS: Ten patients (six males, mean age 6.5 years, SD 4.5 years) and ten controls (mean age 5.9 years, SD 4.7 years) were included. In patients, topology analysis revealed higher clustering coefficient and transitivity and lower small world index and assortativity compared to controls. The bilateral insula were identified as hubs in patients, whereas the cerebellum was detected as a hub only in controls. Three sub-networks of increased connectivity were identified in patients. CONCLUSIONS: We found reduced global and increased local connectivity in children with AgCC compared to controls. Neural plasticity in AgCC may attempt to increase the interhemispheric connectivity through alternative decussating pathways other than the corpus callosum. KEY POINTS: • The structural connectivity analysis quantifies white-matter networks within the brain • In callosal agenesis there is reduced global and increased local connectivity • In callosal agenesis, alternative decussating pathways are used for interhemispheric connectivity.

Diffusion tensor imaging of the brainstem in children with achondroplasia.

AIM: The aims of this study were to compare, using diffusion tensor imaging (DTI) of the brainstem, microstructural integrity of the white matter in children with achondroplasia and age-matched participants and to correlate the severity of craniocervical junction (CCJ) narrowing and neurological findings with DTI scalars in children with achondroplasia. This study also aimed to assess the potential role of fibroblast growth factor receptor type 3 on white matter microstructure. METHOD: Diffusion tensor imaging was performed using a 1.5T magnetic resonance scanner and balanced pairs of diffusion gradients along 20 non-collinear directions. Measurements were obtained from regions of interest, sampled in each pontine corticospinal tract (CST), medial lemniscus, and middle cerebellar peduncle, as well as in the lower brainstem and centrum semiovale, for fractional anisotropy and for mean, axial, and radial diffusivity. In addition, a severity score for achondroplasia was assessed by measuring CCJ narrowing. RESULT: Eight patients with achondroplasia (seven males, one female; mean age 5y 6mo, range 1y 1mo-15y 1mo) and eight age- and sex-matched comparison participants (mean age 5y 2mo, range 1y 1mo-14y 11mo) were included in this study. Fractional anisotropy was lower and mean diffusivity and radial diffusivity were higher in the lower brainstem of patients with achondroplasia than in age-matched comparison participants. The CST and middle cerebellar peduncle of the participants showed increases in mean, axial, and radial diffusivity. Fractional anisotropy in the lower brainstem was negatively correlated with the degree of CCJ narrowing. No differences in the DTI metrics of the centrum semiovale were observed between the two groups. INTERPRETATION: The reduction in fractional anisotropy and increase in diffusivities in the lower brainstem of participants with achondroplasia may reflect secondary encephalomalacic degeneration and cavitation of the affected white matter tracts as shown by histology. In children with achondroplasia, DTI may serve as a potential biomarker for brainstem white matter injury and aid in the care and management of these patients.

Diffusion tensor imaging in pediatric Chiari type I malformation.

AIM: Chiari type I malformation (C1M) may be symptomatic or asymptomatic as an incidental finding. In this retrospective study, we applied diffusion tensor imaging (DTI) to study the brainstem and cerebellar white matter tracts in C1M. METHOD: Diffusion tensor imaging (DTI) data were acquired on a 1.5T MR-scanner using balanced pairs of diffusion gradients along 20 non-collinear directions. Measurements from regions of interest in each pontine corticospinal tract, medial leminscus, and middle cerebellar peduncle (MCP) and in the lower brainstem were obtained for fractional anisotropy and mean, axial, and radial diffusivity. Values in symptomatic and asymptomatic children, and children with and without hydromyelia were compared using analysis of variance. RESULTS: Fifteen children with C1M (10 males, five females; six symptomatic [four with hydromyelia] and nine asymptomatic) were included. Median age was 6 years 5 months (range 2y 10mo-15y 4mo). No significant differences in DTI scalars were found in the lower brainstem. In both MCPs, axial diffusivity values were lower in symptomatic than in asymptomatic children (p=0.049 and p=0.035 respectively) and higher in children with hydromyelia versus without hydromyelia (p=0.018 and p=0.006 respectively). In the left MCP, mean diffusivity values were lower in symptomatic than in asymptomatic children (p=0.047). INTERPRETATION: Our results show that microstructural tissue alterations may be present in C1M. Additionally, our study suggests a specific role for the MCPs in C1M. Further large-scale studies are warranted.

Evaluation of the ischemic penumbra focusing on the venous drainage: the role of susceptibility weighted imaging (SWI) in pediatric ischemic cerebral stroke.

BACKGROUND AND PURPOSE: Susceptibility weighted imaging (SWI) allows the study of the intracranial venous vasculature based on the paramagnetic susceptibility effects of deoxygenated blood. Prominent hypointense draining veins have been revealed in ischemic brain tissue by SWI. The goal of our study was to evaluate whether a match or mismatch between territorial changes in the venous drainage of ischemic brain tissue, as identified by SWI and diffusion restriction, can show a 'venous ischemic penumbra'. MATERIALS AND METHODS: Eight children with a confirmed diagnosis of acute pediatric arterial ischemic stroke (PAIS) were included in this preliminary study. All had undergone an acute standard magnetic resonance imaging (MRI) study with diffusion-weighted imaging (DWI) and SWI sequences. SWI scans were semi-quantitatively evaluated for signal intensity and caliber of both the intramedullary and sulcal veins. In addition, SWI abnormalities were compared with DWI images for match/mismatch of signal alterations, and the acute MRI data were compared with follow-up scans. RESULTS: A total of 17 vascular territories showed infarction. SWI hypointensity in sulcal and intramedullary veins was found in 77% and 94% of the infarcted territories, respectively, while the caliber of the sulcal and intramedullary veins was increased in 64% and 88% of the infarcted areas, respectively. SWI/DWI match was observed in 88% of the vascular territories, whereas mismatch was noted in two; follow-up neuroimaging showed infarct progression into the mismatch areas. CONCLUSION: Our study showed that, in children, high-quality SWI studies focused on venous drainage can provide important non-invasive data on critically perfused brain tissue at risk of infarct progression. SWI is therefore a valuable MR tool that can be added to the battery of neuroimaging techniques for acute PAIS.

Adaptive, behavioral, and emotional outcomes following postoperative pediatric cerebellar mutism syndrome in survivors treated for medulloblastoma.

OBJECTIVE: Patients who experience postoperative pediatric cerebellar mutism syndrome (CMS) during treatment for medulloblastoma have long-term deficits in neurocognitive functioning; however, the consequences on functional or adaptive outcomes are unknown. The purpose of the present study was to compare adaptive, behavioral, and emotional functioning between survivors with and those without a history of CMS. METHODS: The authors examined outcomes in 45 survivors (15 with CMS and 30 without CMS). Comprehensive neuropsychological evaluations, which included parent-report measures of adaptive, behavioral, and emotional functioning, were completed at a median of 2.90 years following craniospinal irradiation. RESULTS: Adaptive functioning was significantly worse in the CMS group for practical and general adaptive skills compared with the group without CMS. Rates of impairment in practical, conceptual, and general adaptive skills in the CMS group exceeded expected rates in the general population. Despite having lower overall intellectual functioning, working memory, and processing speed, IQ and related cognitive processes were uncorrelated with adaptive outcomes in the CMS group. No significant group differences or increased rates of impairment were observed for behavioral and emotional outcomes. CONCLUSIONS: Survivors with CMS, compared with those without CMS, are rated as having significant deficits in overall or general adaptive functioning, with specific weakness in practical skills several years posttreatment. Findings from this study demonstrate the high risk for ongoing functional deficits despite acute recovery from symptoms of CMS, highlighting the need for intervention to mitigate such risk.

Neonatal neuroimaging findings in inborn errors of metabolism.

Individually, metabolic disorders are rare, but overall they account for a significant number of neonatal disorders affecting the central nervous system. The neonatal clinical manifestations of inborn errors of metabolism (IEMs) are characterized by nonspecific systemic symptoms that may mimic more common acute neonatal disorders like sepsis, severe heart insufficiency, or neonatal hypoxic-ischemic encephalopathy. Certain IEMs presenting in the neonatal period may also be complicated by sepsis and cardiomyopathy. Early diagnosis is mandatory to prevent death and permanent long-term neurological impairments. Although neuroimaging findings are rarely specific, they play a key role in suggesting the correct diagnosis, limiting the differential diagnosis, and may consequently allow early initiation of targeted metabolic and genetic laboratory investigations and treatment. Neuroimaging may be especially helpful to distinguish metabolic disorders from other more common causes of neonatal encephalopathy, as a newborn may present with an IEM prior to the availability of the newborn screening results. It is therefore important that neonatologists, pediatric neurologists, and pediatric neuroradiologists are familiar with the neuroimaging findings of metabolic disorders presenting in the neonatal time period.

Diffusion tensor imaging in a child with hypertrophic olivary degeneration.

Hypertrophic olivary degeneration (HOD) is caused by disruptive lesions affecting components of the Guillain-Mollaret triangle (GMT). We present conventional magnetic resonance and diffusion tensor imaging (DTI) findings in a 6-year-old girl with HOD after surgery for a midbrain pilocytic astrocytoma. To our knowledge, this is the first dedicated DTI analysis of GMT in a child with HOD in the literature. In our patient, we found higher fractional anisotropy (FA) and axial diffusivity values of the inferior olivary nucleus (ION) and lower FA, but higher radial diffusivity (RD) values of all other GMT components compared to age-matched controls. Increased FA values of the ION may be explained by increased packing of white matter fibers. However, associated hyperintense T2 signal is contradictory and the association between increased FA values and hyperintense T2 signal remains unclear. Low FA and high RD values of the other GMT components likely reflect demyelination with axonal degeneration and correlate well with histopathological findings.

Apparent diffusion coefficient of pediatric cerebellar tumors: a biomarker of tumor grade?

BACKGROUND: The role of diffusion weighted imaging (DWI) to reliably differentiate tumor types and grades in pediatric cerebellar tumors is controversial. We aimed to clarify the discrepancy reported in previous articles. PROCEDURES: We retrospectively evaluated the apparent diffusion coefficient (ADC) values of the enhancing, solid parts of cerebellar tumors and correlated the absolute tumor ADC values and cerebellar and thalamic ratios with histology in a cohort of children with cerebellar tumors. RESULTS: Twenty-four children (12 females) were included in the study. The median age at pre-surgical MRI was 10 years (range 29 days-18.5 years). Absolute ADC values (mean 1.49, SD 0.25 vs. 0.63 ± 0.18), cerebellar (2.04 ± 0.33 vs. 0.83 ± 0.25), and thalamic ratio (1.98 ± 0.35 vs. 0.79 ± 0.23) were significantly higher in low- than in high-grade tumors (P < 0.0001). Absolute ADC values and cerebellar and thalamic ratios were significantly higher in low-grade astrocytomas than in MBs. Overlap was seen for WHO grade II and III ependymomas. One hundred percent specific cutoff ADC values of >1.2 × 10(3) and <0.8 × 10(-3) mm(2) /s were established for low- and high-grade tumors. CONCLUSION: ADC analysis of the solid, contrast enhancing components of pediatric cerebellar tumors may facilitate differentiation between various tumor histologies.