Concepts about the production, absorption, dynamics, and physiological roles of cerebrospinal fluid (CSF) have dramatically changed over the recent decades. This article will review these new concepts and detail how they must be used for a better assessment and a better understanding of the various aspects of hydrocephalus by using neuroradiological tools.

The identification of children with traumatic brain injury (TBI) who are at risk of death or poor global neurological functional outcome remains a challenge. Magnetic resonance imaging (MRI) can detect several brain pathologies that are a result of TBI; however, the types and locations of pathology that are the most predictive remain to be determined. Forty-two critically ill children with TBI were recruited prospectively from pediatric intensive care units at five Canadian children's hospitals. Pathologies detected on subacute phase MRIs included cerebral hematoma, herniation, cerebral laceration, cerebral edema, midline shift, and the presence and location of cerebral contusion or diffuse axonal injury (DAI) in 28 regions of interest were assessed. Global functional outcome or death more than 12 months post-injury was assessed using the Pediatric Cerebral Performance Category score. Linear modeling was employed to evaluate the utility of an MRI composite score for predicting long-term global neurological function or death after injury, and nonlinear Random Forest modeling was used to identify which MRI features have the most predictive utility. A linear predictive model of favorable versus unfavorable long-term outcomes was significantly improved when an MRI composite score was added to clinical variables. Nonlinear Random Forest modeling identified five MRI variables as stable predictors of poor outcomes: presence of herniation, DAI in the parietal lobe, DAI in the subcortical white matter, DAI in the posterior corpus callosum, and cerebral contusion in the anterior temporal lobe. Clinical MRI has prognostic value to identify children with TBI at risk of long-term unfavorable outcomes.

Background Failure to appreciate deep venous drainage pathways is a major cause of severe complications in the endovascular treatment of vein of Galen aneurysmal malformations (VOGMs). Objective To report deep venous drainage patterns in patients with VOGM, emphasizing the internal cerebral veins, and to describe the challenges in evaluating these. Methods Patients with VOGM presenting to our institute between 2000 and 2018 were retrospectively analyzed. Patients with complete and good quality imaging datasets were included in the study. Three neuroradiologists with expertise in the subject independently analyzed the deep venous drainage patterns on multi-sequence MRI and digital subtraction angiography. Follow-up imaging studies were analyzed for alterations in deep venous drainage patterns that occurred following endovascular treatment. Descriptive statistics were used to report findings. Results Twenty-three patients had optimal quality MRI imaging and 25 had optimal quality DSA imaging available. In 14/23 (61%) patients, internal cerebral vein (ICV) communication could be reliably identified on MRI and in 8/25 (32%) patients on DSA. Deep venous communication with the VOGM was demonstrated in 8/26 (30.8%) patients. One (3.8%) patient demonstrated ICV communication with the VOGM only on postoperative imaging, while in 2 (8%) patients the ICV drainage route changed from VOGM to alternative pathways after the procedure. Other variant pathways included lateral mesencephalic vein, superior or inferior sagittal sinus, anterior mesencephalic vein, tentorial sinus, deep Sylvian vein, and superior vermian vein. Conclusion ICV communication with the VOGM is not uncommon and requires dedicated preprocedural imaging to identify it. However, there are significant challenges in assessing this communication in the presence of high-flow fistulae, vessel tortuosity and size, and contrast limitations in this population.

Neuroimaging, specifically MRI (oriented by the clinical, functional, and electroencephalographic [EEG]/magnetoencephalographic [MEG] data), plays a central role in the assessment of epilepsy, as it is the most efficient way to demonstrate a lesion that is causally associated with the disease and to make possible a surgical treatment of it. Such a lesion may be obvious, but it may commonly be quite subtle, and for that reason, the best possible quality of imaging is mandatory: multiplanar, multisequence high-definition imaging, as much as possible with a "high field" magnet (3+ teslas) and a multiple phased-array coil. Diffusion tensor imaging (DTI) also is needed for the surgical planning. The best indications for epilepsy surgery are the lesions that are typically associated with severe, drug-resistant epilepsy. A common example in children are the low-grade epilepsy-associated tumors (LEATs; ganglioglioma and variants, dysembryoplastic neuroepithelial tumor [DNET], and pleomorphic xanthoastrocytoma [PAX] mostly, but also more rarely, angiocentric glioma, papillary glioneuronal tumor (PGNT), as well as any glial tumor involving the cortex). Focal cortical dysplasias (FCDs) are epileptogenic developmental lesions that may be very subtle. They are classified histologically in three types: most typical, FCD 2 (Taylor's) is defined by the presence of monstrous cells; FCD 1, more difficult to identify radiologically, is defined by an abnormal cortical layering; and FCD 3 are defined by their association with a principal lesion (hippocampal sclerosis, LEATs, vascular malformation, destructive lesions). Other surgical indications include the hemimegalencephalies (HMEs; hemispheric FCD) and sometimes tuberous sclerosis TSC (syndromic FCD), as well as the hypothalamic hamartomas, typically sessile and attached to the mammillary bodies. Cortex-associated cavernomas are obvious indications. Palliative surgery may be needed in Sturge-Weber's or Rasmussen's diseases, as well as in some cases of chronic encephalomalacic lesions. Obviously, like in adults but much less commonly, mesial temporal sclerosis is an important cause of refractory epilepsy in children, and therefore a surgical indication. In exceptional cases, major malformations of cortical development (MCD) such as a heterotopia, a polymicrogyria (PMG), or a schizencephaly may also benefit from surgery and can be diagnosed by MRI only.

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The corpus callosum is the largest of the 3 telencephalic commissures in eutherian (placental) mammals. Although the anterior commissure, and the hippocampal commissure before being pushed dorsally by the expanding frontal lobes, cross through the lamina reuniens (upper part of the lamina terminalis), the callosal fibers need a transient interhemispheric cellular bridge to cross. This review describes the molecular pathways that initiate the specification of the cells comprising this bridge, the specification of the callosal neurons, and the repulsive and attractive guidance molecules that convey the callosal axons toward, across, and away from the midline to connect with their targets.

The objective of this review is to discuss the role of neuroimaging in evaluating pediatric and fetal hydrocephalus based on possible pathophysiologic mechanisms and in the context of differing etiology. Although conventional brain imaging with ultrasound (US), computed tomography (CT), and magnetic resonance imaging (MRI) is commonly used to assess for ventricular enlargement, however, the underlying mechanisms and management of hydrocephalus is a challenge in pediatric population and fetal hydrocephalus. MRI helps define the possible nature of the obstruction, and provides useful functional and anatomic information. MR imaging, in both pediatric and fetal hydrocephalus, thus may help in better understanding of the possible pathophysiologic mechanisms of the varied causal factors. The article focuses on the usage of MRI sequences in both diagnosis and follow-up of pediatric and fetal hydrocephalus, to be able to investigate all possible etiopathogenesis through the CSF pathway and to assess the efficacy of treatment in a non-invasive standardized manner.

Purpose Brain metabolites show very rapid maturation over infancy, particularly following very preterm (VPT) birth, and can provide an index of brain injury. The utility of magnetic resonance imaging (MRS, magnetic resonance spectroscopy) in predicting outcome in VPT-born infants is largely limited to 2-year outcomes. We examined the value of MRS in VPT followed longitudinally to 4 years. Methods MRS datasets were acquired in 45 VPT infants (< 32 weeks gestational age) longitudinally: at birth, at term-equivalent and at 4 years of age. Using LCModel analyses in a basal ganglia voxel, we investigated metabolite ratios as a function of age, brain injury and outcome. We also studied a full-term (FT) cohort at 4 years and compared group differences with outcome. Results We found significant age-related changes in many brain metabolites in infancy, including phosphocreatine (CR)/phosphocholine (CHO), N -acetylaspartylglutamate (NAA)/CHO, myoinositol (INS)/CHO and INS/CR; there were no significant MRS differences between VPT and FT groups at 4 years of age, or differences at 4 years as a function of early brain injury or outcome. The rate of change in metabolite ratios from VPT birth to term-equivalent age did not predict outcome in the VPT children at 4 years. Conclusion Brain metabolite ratios measured in VPT-born infants have shown associations with short-term outcomes, but these correlations did not extend to early childhood nor predict cognitive sequelae. The most frequently reported poor outcome in VPT-born children is cognitive difficulties starting at early school age. MRS metrics early in the infant’s life do not appear to predict these longer-term outcomes.

Patients with the ACTA2 mutation have distinctive clinical and angiographic featuresspecifically, a combination of ectasia and stenosis, a straight arterial course, absence of basal collaterals, and more widespread cerebrovascular involvement in comparison with Moyamoya disease. Neuroimaging studies from 13 patients with heterozygous Arg179His mutations in ACTA2 and 1 patient with pathognomonic clinicoradiologic findings for ACTA2 mutation were retrospectively reviewed. Characteristic bending and hypoplasia of the anterior corpus callosum, apparent absence of the anterior gyrus cinguli, and radial frontal gyration were present in 100% of the patients; flattening of the pons on the midline and multiple indentations in the lateral surface of the pons were demonstrated in 93% of the patients. BACKGROUND AND PURPOSE:Arg179His mutations in ACTA2 are associated with a distinctive neurovascular phenotype characterized by a straight course of intracranial arteries, absent basal Moyamoya collaterals, dilation of the proximal internal carotid arteries, and occlusive disease of the terminal internal carotid arteries. We now add to the distinctive neuroimaging features in these patients by describing their unique constellation of brain malformative findings that could flag the diagnosis in cases in which targeted cerebrovascular imaging has not been performed. MATERIALS AND METHODS: Neuroimaging studies from 13 patients with heterozygous Arg179His mutations in ACTA2 and 1 patient with pathognomonic clinicoradiologic findings for ACTA2 mutation were retrospectively reviewed. The presence and localization of brain malformations and other abnormal brain MR imaging findings are reported. RESULTS: Characteristics bending and hypoplasia of the anterior corpus callosum, apparent absence of the anterior gyrus cinguli, and radial frontal gyration were present in 100% of the patients; flattening of the pons on the midline and multiple indentations in the lateral surface of the pons were demonstrated in 93% of the patients; and apparent squeezing of the cerebral peduncles in 85% of the patients. CONCLUSIONS: Because -actin is not expressed in the brain parenchyma, only in vascular tissue, we speculate that rather than a true malformative process, these findings represent a deformation of the brain during development related to the mechanical interaction with rigid arteries during the embryogenesis.

Importance Hydrocephalus is a treatable but potentially fatal complication that has not been previously described in congenital Zika syndrome (CZS). Objective To describe the clinical features and imaging findings in 24 patients with congenital Zika syndrome (CZS) who developed hydrocephalus. Design, Setting, and Participants This case series included patients with hydrocephalus who were born in October and November 2015 and followed up until mid-2017 in the 2 largest national referral centers for CZS in Brazil. The participants included consecutively enrolled children with a clinical and laboratorial diagnosis of CZS who developed clinical and/or image findings suggestive of hydrocephalus and who were confirmed to experience increased intracranial hypertension during ventriculoperitoneal shunt procedures. Main Outcomes and Measures To retrospectively describe clinical and image findings in these 24 patients. Results This multicenter cohort included 308 patients with CZS; 24 consecutive children were enrolled in this study. These children were aged between 3 to 18 months, and 13 of 24 (54%) were female. All patients presented with at least 1 positive test result for anti-Zika antibodies in cerebrospinal fluid or serum and had classic signs of CZS. At the time of hydrocephalus diagnosis, only 14 of 24 patients (58%) had symptoms and signs suggestive of hydrocephalus (mainly worsening seizures, vomiting, irritability, and/or sudden increase of head circumference percentile). Two of 24 patients (8%) had no symptoms suggestive of hydrocephalus but were found to have reduced brain volume on repeated imaging. Cerebellar or brainstem hypoplasia on baseline imaging were found in 18 of 23 patients (78%). At the second computed tomographic scan, all patients showed a marked increase of ventricular volume, compatible with communicating hydrocephalus, and reduction of brain tissue that was visibly worse than on baseline imaging for the 23 patients with repeated scans. Conclusions and Relevance We present evidence that hydrocephalus is a complication of CZS in at least a proportion of patients. The clinical spectrum of this condition continues to evolve, but given that presenting signs and symptoms of hydrocephalus can be challenging to recognize in CZS, we provisionally recommend that high suspicion and appropriate monitoring for hydrocephalus should be part of the standard care of patients with CZS.

BACKGROUND AND PURPOSE: Molecular grouping of medulloblastoma correlates with prognosis and supports the therapeutic strategy. We provide our experience with the imaging features of primary and metastatic disease in relation to the molecular groups. MATERIALS AND METHODS: One hundred nineteen consecutive patients (mean age, 7.3 ± 3.8 years at diagnosis; male, 79 [66.4%]) with a confirmed diagnosis of medulloblastoma and interpretable pretreatment MRIs were retrieved from our data base from January 2000 to December 2016. Each patient was assigned to wingless, sonic hedgehog, group 3, or group 4 molecular groups. Then, we determined the imaging features of both primary and metastatic/recurrent disease predictive of molecular groups. RESULTS: In addition to recently reported predictors based on primary tumor, including cerebellar peripheral location for sonic hedgehog (adjusted odds ratio = 9, P < .0001), minimal enhancement of primary group 4 tumor (adjusted odds ratio = 5.2, P < .0001), and cerebellopontine angle location for wingless (adjusted odds ratio = 1.4, P = .03), ependymal metastasis with diffusion restriction and minimal postcontrast enhancement (“mismatching pattern”) (adjusted odds ratio = 2.8, P = .001) for group 4 and spinal metastasis for group 3 (adjusted odds ratio = 1.9, P = .01) also emerged as independent predictors of medulloblastoma molecular groups. Specifically, the presence of a metastasis in the third ventricular infundibular recess showing a mismatching pattern was significantly associated with group 4 (P = .02). CONCLUSIONS: In addition to imaging features of primary tumors, some imaging patterns of metastatic dissemination in medulloblastoma seem characteristic, perhaps even specific to certain groups. This finding could further help in differentiating molecular groups, specifically groups 3 and 4, when the characteristics of the primary tumor overlap.

Brain tumors are the most common solid tumors in the pediatric population. Pediatric neuro-oncology has changed tremendously during the past decade owing to ongoing genomic advances. The diagnosis, prognosis, and treatment of pediatric brain tumors are now highly reliant on the genetic profile and histopathologic features of the tumor rather than the histopathologic features alone, which previously were the reference standard. The clinical information expected to be gleaned from radiologic interpretations also has evolved. Imaging is now expected to not only lead to a relevant short differential diagnosis but in certain instances also aid in predicting the specific tumor and subtype and possibly the prognosis. These processes fall under the umbrella of radiogenomics. Therefore, to continue to actively participate in patient care and/or radiogenomic research, it is important that radiologists have a basic understanding of the molecular mechanisms of common pediatric central nervous system tumors. The genetic features of pediatric low-grade gliomas, high-grade gliomas, medulloblastomas, and ependymomas are reviewed; differences between pediatric and adult gliomas are highlighted; and the critical oncogenic pathways of each tumor group are described. The role of the mitogen-activated protein kinase pathway in pediatric low-grade gliomas and of histone mutations as epigenetic regulators in pediatric high-grade gliomas is emphasized. In addition, the oncogenic drivers responsible for medulloblastoma, the classification of ependymomas, and the associated imaging correlations and clinical implications are discussed. ©RSNA, 2018.

BackgroundCongenital bilateral vocal cord paralysis is a rare occurrence. Approximately half the cases are associated with a major comorbidity, usually neurological, neuromuscular or malformative.Case presentationIn a male newborn, respiratory distress syndrome and stridor were observed immediately following birth. The cause was bilateral vocal cord paralysis in the adducted position. Neuroradiological investigation revealed a unilateral discontinuity between the upper pons and the right medulla oblongata. Hypoplasia of the right posterior hemiarches of C1-C2 and the right exo-occipital bone was observed, as was a small clivus. MR angiography showed the absence of the distal right vertebral artery, with hypoplasia and parietal irregularities of the proximal segments. Respiratory autonomy was not obtained despite endoscopic laser cordotomy, corticosteroid therapy and nasal continuous positive airway pressure. The infant died at the age of 4weeks after treatment was limited to comfort care.ConclusionsA medullary lesion is an exceptional cause of congenital bilateral vocal cord paralysis. The strictly unilateral neurological and vascular defect and the absence of associated intracranial or extracranial malformation make this clinical case unique and suggest a disruptive mechanism. This case also highlights the help provided by advanced neuroimaging techniques, i.e. fibre tracking using diffusion tensor imaging, in the decision-making process.