Avner Meoded

Neuroimaging of pediatric posterior fossa tumors including review of the literature.

Conventional, anatomical MRI is an essential tool for diagnosis and evaluation of location, quality, and extent of posterior fossa tumors, but offers limited information regarding tumor grade and type. Advanced MRI techniques such as diffusion weighted imaging (DWI) and diffusion tensor imaging (DTI) may improve the specific diagnosis of brain tumors in the posterior fossa in children. In this review the conventional neuroimaging findings, as well as the DWI, and DTI characteristics of common pediatric posterior fossa tumors are discussed and summarized. J. Magn. Reson. Imaging 2012;35:32‐47.

The unique features of traumatic brain injury in children. review of the characteristics of the pediatric skull and brain, mechanisms of trauma, patterns of injury, complications, and their imaging findings--part 2.

Traumatic brain injury (TBI) is a major cause of morbidity and mortality in children. The unique biomechanical, hemodynamical, and functional characteristics of the developing brain and the age‐dependent variance in trauma mechanisms result in a wide range of age specific traumas and patterns of brain injuries. Detailed knowledge of the main primary and secondary pediatric injuries, which enhance sensitivity and specificity of diagnosis, will guide therapy and may give important information about the prognosis. In recent years, anatomical but also functional imaging methods have revolutionized neuroimaging of pediatric TBI. The purpose of this article is (1) to comprehensively review frequent primary and secondary brain injuries and (2) to give a short overview of two special types of pediatric TBI: birth related and nonaccidental injuries. J Neuroimaging 2012;22:e18–e41.

Diffusion tensor imaging and fiber tractography in brain malformations

Diffusion tensor imaging (DTI) is an advanced MR technique that provides qualitative and quantitative information about the micro-architecture of white matter. DTI and its post-processing tool fiber tractography (FT) have been increasingly used in the last decade to investigate the microstructural neuroarchitecture of brain malformations. This article aims to review the use of DTI and FT in the evaluation of a variety of common, well-described brain malformations, in particular by pointing out the additional information that DTI and FT renders compared with conventional MR sequences. In addition, the relevant existing literature is summarized.

Susceptibility weighted imaging of the neonatal brain

Susceptibility weighted imaging (SWI) is a well-established magnetic resonance technique, which is highly sensitive for blood, iron, and calcium depositions in the brain and has been implemented in the routine clinical use in both children and neonates. SWI in neonates might provide valuable additional diagnostic and prognostic information for a wide spectrum of neonatal neurological disorders. To date, there are few articles available on the application of SWI in neonatal neurological disorders. The purpose of this article is to illustrate and describe the characteristic SWI findings in various typical neonatal neurological disorders.

Susceptibility-weighted imaging (SWI): A potential non-invasive imaging tool for characterizing ischemic brain injury?

Susceptibility-weighted imaging (SWI) is a new high-resolution magnetic resonance imaging (MRI) tool that uses the paramagnetic susceptibility effects of deoxygenated blood to study the intracranial venous vasculature. We present SWI imaging findings in two children who suffered from acute arterial ischemia. Various patterns of normal/altered venous drainage could be identified. Our case study suggests that SWI assisted mapping of the regional changes of the cerebral venous drainage and correlation with diffusion weighted MRI may identify critically perfused brain at risk for infarct progression. Prospective studies are mandatory to further validate the value of SWI.

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. J. Magn. Reson. Imaging 2013;37:294–312.

Accuracy of head ultrasound for the detection of intracranial hemorrhage in preterm neonates: comparison with brain MRI and susceptibility-weighted imaging.

OBJECTIVES To evaluate the sensitivity and specificity of head ultrasound (HUS) in the detection of intracranial hemorrhage in premature neonates compared with brain MRI using susceptibility-weighted imaging (SWI). MATERIAL AND METHODS Ultrasound (US) and MRI scans of the brain using SWI in premature neonates were retrospectively evaluated for grade I-III germinal matrix hemorrhage (GMH), periventricular hemorrhagic infarction (PVHI), intra-axial hemorrhage other than PVHI, extra-axial hemorrhage in each cerebral hemisphere and cerebellar hemorrhage in each cerebellar hemisphere. The impact of these hemorrhagic findings on short-term clinical management was also reviewed. RESULTS Twelve neonates (mean age: 9.8 days; range: 3-23 days) with a mean gestational age of 32.8 weeks (range: 29.6-35.4 weeks) were included in the study. HUS had high sensitivity (100%) and specificity (93.3%) in detecting grade III GMH using SWI as a reference, but poor sensitivity (0%) in the detection of intraventricular hemorrhage with normal-sized ventricles (grade II GMH). US was not sensitive in detecting either small cerebellar or extra-axial hemorrhage. CONCLUSION HUS was highly sensitive and specific in the evaluation of grade III GMH, whereas SWI was superior to HUS in detecting small intra-axial or extra-axial hemorrhage, and had no impact on short-term management. Given the low cost, lack of radiation and advantages of bedside evaluation, HUS should continue to be the first line of imaging for brain injury in the evaluation of premature neonates with suspected intracranial hemorrhage. However, the usefulness of SWI for predicting long-term neurological outcomes has yet to be determined.

Diffusion tensor imaging in pediatric Chiari type I malformation

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.

Macrocerebellum: Significance and Pathogenic Considerations

Macrocerebellum is a rare finding characterized by an abnormally large cerebellum. Only few patients with a syndromal or isolated macrocerebellum have been reported so far. This article aims to categorize the magnetic resonance imaging (MRI) findings, quantitate the macrocerebellum by volumetric analysis, characterize the neurological and dysmorphic features and cognitive outcome, and report the results of genetic analyses in children with macrocerebellum. All MR images were qualitatively evaluated for infratentorial and supratentorial abnormalities. Volumetric analysis was performed. Data about neurological and dysmorphic features, outcome, and genetic analysis were collected from clinical histories and follow-up examinations. Five patients were included. Volumetric analysis in three patients confirmed large cerebellar size compared to age-matched controls. MR evaluation showed that thickening of the cortical gray matter of the cerebellar hemispheres is responsible for the macrocerebellum. Additional infratentorial and supratentorial abnormalities were present in all patients. Muscular hypotonia, as well as impaired motor and cognitive development, was found in all patients, with ocular movement disorders in three of five patients. The five patients differed significantly in terms of dysmorphic features and involvement of extracerebral organs. Submicroscopic chromosomal aberrations were found in two patients. Macrocerebellum is caused by thickening of the cortical gray matter of the cerebellar hemispheres, suggesting that cerebellar granule cells may be involved in its development. Patients with macrocerebellum show highly heterogeneous neuroimaging, clinical, and genetic findings, suggesting that macrocerebellum is not a nosological entity, but instead represents the structural manifestation of a deeper, more basic biological disturbance common to heterogeneous disorders.

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

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.