Changes to pediatric brain tumors in 2021 World Health Organization classification of tumors of the central nervous system.

New tumor types are continuously being described with advances in molecular testing and genomic analysis resulting in better prognostics, new targeted therapy options and improved patient outcomes. As a result of these advances, pathological classification of tumors is periodically updated with new editions of the World Health Organization (WHO) Classification of Tumors books. In 2021, WHO Classification of Tumors of the Central Nervous System, 5th edition (CNS5), was published with major changes in pediatric brain tumors officially recognized including pediatric gliomas being separated from adult gliomas, ependymomas being categorized based on anatomical compartment and many new tumor types, most of them seen in children. Additional general changes, such as tumor grading now being done within tumor types rather than across entities and changes in definition of glioblastoma, are also relevant to pediatric neuro-oncology practice. The purpose of this manuscript is to highlight the major changes in pediatric brain tumors in CNS5 most relevant to radiologists. Additionally, brief descriptions of newly recognized entities will be presented with a focus on imaging findings.

SUFU haploinsufficiency causes a recognisable neurodevelopmental phenotype at the mild end of the Joubert syndrome spectrum.

BACKGROUND: Joubert syndrome (JS) is a recessively inherited ciliopathy characterised by congenital ocular motor apraxia (COMA), developmental delay (DD), intellectual disability, ataxia, multiorgan involvement, and a unique cerebellar and brainstem malformation. Over 40 JS-associated genes are known with a diagnostic yield of 60%-75%.In 2018, we reported homozygous hypomorphic missense variants of the SUFU gene in two families with mild JS. Recently, heterozygous truncating SUFU variants were identified in families with dominantly inherited COMA, occasionally associated with mild DD and subtle cerebellar anomalies. METHODS: We reanalysed next generation sequencing (NGS) data in two cohorts comprising 1097 probands referred for genetic testing of JS genes. RESULTS: Heterozygous truncating and splice-site SUFU variants were detected in 22 patients from 17 families (1.5%) with strong male prevalence (86%), and in 8 asymptomatic parents. Patients presented with COMA, hypotonia, ataxia and mild DD, and only a third manifested intellectual disability of variable severity. Brain MRI showed consistent findings characterised by vermis hypoplasia, superior cerebellar dysplasia and subtle-to-mild abnormalities of the superior cerebellar peduncles. The same pattern was observed in two out of three tested asymptomatic parents. CONCLUSION: Heterozygous truncating or splice-site SUFU variants cause a novel neurodevelopmental syndrome encompassing COMA and mild JS, which likely represent overlapping entities. Variants can arise de novo or be inherited from a healthy parent, representing the first cause of JS with dominant inheritance and reduced penetrance. Awareness of this condition will increase the diagnostic yield of JS genetic testing, and allow appropriate counselling about prognosis, medical monitoring and recurrence risk.

Deep medullary vein engorgement and superficial medullary vein engorgement: two patterns of perinatal venous stroke.

Perinatal venous stroke has classically been attributed to cerebral sinovenous thrombosis with resultant congestion or thrombosis of the small veins draining the cerebrum. Advances in brain MRI, in particular susceptibility-weighted imaging, have enabled the visualization of the engorged small intracerebral veins, and the spectrum of perinatal venous stroke has expanded to include isolated congestion or thrombosis of the deep medullary veins and the superficial intracerebral veins. Congestion or thrombosis of the deep medullary veins or the superficial intracerebral veins can result in vasogenic edema, cytotoxic edema or hemorrhage in the territory of disrupted venous flow. Deep medullary vein engorgement and superficial medullary vein engorgement have characteristic findings on MRI and should be differentiated from neonatal hemorrhagic stroke.

Imaging of Horner syndrome in pediatrics: association with neuroblastoma.

Neuroblastoma is the most common neoplasm associated with pediatric Horner syndrome. The laboratory and imaging evaluation of isolated pediatric Horner syndrome is controversial. We review the literature published in the last several decades and present the rationale for the imaging work-up in this patient cohort.

Correction to: Subdural hemorrhage rebleeding in abused children: frequency, associations and clinical presentation.

The original article included a statement which is not fully accurate. This correction clarifies the original statement.

MN1 C-terminal truncation syndrome is a novel neurodevelopmental and craniofacial disorder with partial rhombencephalosynapsis.

MN1 encodes a transcriptional co-regulator without homology to other proteins, previously implicated in acute myeloid leukaemia and development of the palate. Large deletions encompassing MN1 have been reported in individuals with variable neurodevelopmental anomalies and non-specific facial features. We identified a cluster of de novo truncating mutations in MN1 in a cohort of 23 individuals with strikingly similar dysmorphic facial features, especially midface hypoplasia, and intellectual disability with severe expressive language delay. Imaging revealed an atypical form of rhombencephalosynapsis, a distinctive brain malformation characterized by partial or complete loss of the cerebellar vermis with fusion of the cerebellar hemispheres, in 8/10 individuals. Rhombencephalosynapsis has no previously known definitive genetic or environmental causes. Other frequent features included perisylvian polymicrogyria, abnormal posterior clinoid processes and persistent trigeminal artery. MN1 is encoded by only two exons. All mutations, including the recurrent variant p.Arg1295* observed in 8/21 probands, fall in the terminal exon or the extreme 3' region of exon 1, and are therefore predicted to result in escape from nonsense-mediated mRNA decay. This was confirmed in fibroblasts from three individuals. We propose that the condition described here, MN1 C-terminal truncation (MCTT) syndrome, is not due to MN1 haploinsufficiency but rather is the result of dominantly acting C-terminally truncated MN1 protein. Our data show that MN1 plays a critical role in human craniofacial and brain development, and opens the door to understanding the biological mechanisms underlying rhombencephalosynapsis.

Subdural hemorrhage rebleeding in abused children: frequency, associations and clinical presentation.

BACKGROUND: Limited documentation exists about how frequently radiologically visible rebleeding occurs with abusive subdural hemorrhages (SDH). Likewise, little is known about rebleeding predispositions and associated symptoms. OBJECTIVE: To describe the frequency of subdural rebleeding after abusive head trauma (AHT), its predispositions and clinical presentation. MATERIALS AND METHODS: We evaluated children with SDHs from AHT who were reimaged within a year of their initial hospitalization, retrospectively reviewing clinical details and imaging. We used the available CT and MR images. We then performed simple descriptive and comparative statistics. RESULTS: Fifty-four of 85 reimaged children (63.5%) with AHT-SDH rebled. No child had new trauma, radiologic evidence of new parenchymal injury or acute neurologic symptoms from rebleeding. From the initial presentation, macrocephaly was associated with subsequent rebleeding. Greater subdural depth, macrocephaly, ventriculomegaly and brain atrophy at follow-up were associated with rebleeding. No other radiologic findings at initial presentation or follow-up predicted rebleeding risk, although pre-existing brain atrophy at initial admission and initial chronic SDHs barely missed significance. Impact injuries, retinal hemorrhages and clinical indices of initial injury severity were not associated with rebleeding. All rebleeding occurred within chronic SDHs; no new bridging vein rupture was identified. The mean time until rebleeding was recognized was 12 weeks; no child had rebleeding after 49 weeks. CONCLUSION: Subdural rebleeding is common and occurs in children who have brain atrophy, ventriculomegaly, macrocephaly and deep SDHs at rebleed. It usually occurs in the early months post-injury. All children with rebleeds were neurologically asymptomatic and lacked histories or clinical or radiologic findings of new trauma. Bleeds did not occur outside of chronic SDHs. We estimate the maximum predicted frequency of non-traumatic SDH rebleeding accompanied by acute neurological symptoms in children with a prior abusive SDH is 3.5%.

Redefining the Etiologic Landscape of Cerebellar Malformations.

Cerebellar malformations are diverse congenital anomalies frequently associated with developmental disability. Although genetic and prenatal non-genetic causes have been described, no systematic analysis has been performed. Here, we present a large-exome sequencing study of Dandy-Walker malformation (DWM) and cerebellar hypoplasia (CBLH). We performed exome sequencing in 282 individuals from 100 families with DWM or CBLH, and we established a molecular diagnosis in 36 of 100 families, with a significantly higher yield for CBLH (51%) than for DWM (16%). The 41 variants impact 27 neurodevelopmental-disorder-associated genes, thus demonstrating that CBLH and DWM are often features of monogenic neurodevelopmental disorders. Though only seven monogenic causes (19%) were identified in more than one individual, neuroimaging review of 131 additional individuals confirmed cerebellar abnormalities in 23 of 27 genetic disorders (85%). Prenatal risk factors were frequently found among individuals without a genetic diagnosis (30 of 64 individuals [47%]). Single-cell RNA sequencing of prenatal human cerebellar tissue revealed gene enrichment in neuronal and vascular cell types; this suggests that defective vasculogenesis may disrupt cerebellar development. Further, de novo gain-of-function variants in PDGFRB, a tyrosine kinase receptor essential for vascular progenitor signaling, were associated with CBLH, and this discovery links genetic and non-genetic etiologies. Our results suggest that genetic defects impact specific cerebellar cell types and implicate abnormal vascular development as a mechanism for cerebellar malformations. We also confirmed a major contribution for non-genetic prenatal factors in individuals with cerebellar abnormalities, substantially influencing diagnostic evaluation and counseling regarding recurrence risk and prognosis.

Expanding phenotype with severe midline brain anomalies and missense variant supports a causal role for FOXA2 in 20p11.2 deletion syndrome.

Rare individuals with 20p11.2 proximal deletions have been previously reported, with a variable phenotype that includes heterotaxy, biliary atresia, midline brain defects associated with panhypopituitarism, intellectual disability, scoliosis, and seizures. Deletions have ranged in size from 277 kb to 11.96 Mb. We describe a newborn with a de novo 2.7 Mb deletion of 20p11.22p11.21 that partially overlaps previously reported deletions and encompasses FOXA2. Her clinical findings further expand the 20p11.2 deletion phenotype to include severe midline cranial and intracranial defects such as aqueductal stenosis with hydrocephalus, mesencephalosynapsis with diencephalic-mesencephalic junction dysplasia, and pyriform aperture stenosis. We also report one individual with a missense variant in FOXA2 who had abnormal glucose homeostasis, panhypopituitarism, and endodermal organ dysfunction. Together, these findings support the critical role of FOXA2 in panhypopituitarism and midline defects.

Glial injury in neurotoxicity after pediatric CD19-directed chimeric antigen receptor T cell therapy.

OBJECTIVE: To test whether systemic cytokine release is associated with central nervous system inflammatory responses and glial injury in immune effector cell-associated neurotoxicity syndrome (ICANS) after chimeric antigen receptor (CAR)-T cell therapy in children and young adults. METHODS: We performed a prospective cohort study of clinical manifestations as well as imaging, pathology, CSF, and blood biomarkers on 43 subjects ages 1 to 25 who received CD19-directed CAR/T cells for acute lymphoblastic leukemia (ALL). RESULTS: Neurotoxicity occurred in 19 of 43 (44%) subjects. Nine subjects (21%) had CTCAE grade 3 or 4 neurological symptoms, with no neurotoxicity-related deaths. Reversible delirium, headache, decreased level of consciousness, tremor, and seizures were most commonly observed. Cornell Assessment of Pediatric Delirium (CAPD) scores ≥9 had 94% sensitivity and 33% specificity for grade ≥3 neurotoxicity, and 91% sensitivity and 72% specificity for grade ≥2 neurotoxicity. Neurotoxicity correlated with severity of cytokine release syndrome, abnormal past brain magnetic resonance imaging (MRI), and higher peak CAR-T cell numbers in blood, but not cerebrospinal fluid (CSF). CSF levels of S100 calcium-binding protein B and glial fibrillary acidic protein increased during neurotoxicity, indicating astrocyte injury. There were concomitant increases in CSF white blood cells, protein, interferon-γ (IFNγ), interleukin (IL)-6, IL-10, and granzyme B (GzB), with concurrent elevation of serum IFNγ IL-10, GzB, granulocyte macrophage colony-stimulating factor, macrophage inflammatory protein 1 alpha, and tumor necrosis factor alpha, but not IL-6. We did not find direct evidence of endothelial activation. INTERPRETATION: Our data are most consistent with ICANS as a syndrome of systemic inflammation, which affects the brain through compromise of the neurovascular unit and astrocyte injury. ANN NEUROL 2019.

MACF1 Mutations Encoding Highly Conserved Zinc-Binding Residues of the GAR Domain Cause Defects in Neuronal Migration and Axon Guidance.

To date, mutations in 15 actin- or microtubule-associated genes have been associated with the cortical malformation lissencephaly and variable brainstem hypoplasia. During a multicenter review, we recognized a rare lissencephaly variant with a complex brainstem malformation in three unrelated children. We searched our large brain-malformation databases and found another five children with this malformation (as well as one with a less severe variant), analyzed available whole-exome or -genome sequencing data, and tested ciliogenesis in two affected individuals. The brain malformation comprised posterior predominant lissencephaly and midline crossing defects consisting of absent anterior commissure and a striking W-shaped brainstem malformation caused by small or absent pontine crossing fibers. We discovered heterozygous de novo missense variants or an in-frame deletion involving highly conserved zinc-binding residues within the GAR domain of MACF1 in the first eight subjects. We studied cilium formation and found a higher proportion of mutant cells with short cilia than of control cells with short cilia. A ninth child had similar lissencephaly but only subtle brainstem dysplasia associated with a heterozygous de novo missense variant in the spectrin repeat domain of MACF1. Thus, we report variants of the microtubule-binding GAR domain of MACF1 as the cause of a distinctive and most likely pathognomonic brain malformation. A gain-of-function or dominant-negative mechanism appears likely given that many heterozygous mutations leading to protein truncation are included in the ExAC Browser. However, three de novo variants in MACF1 have been observed in large schizophrenia cohorts.

Establishment of normative values for the fetal posterior fossa by magnetic resonance imaging.

OBJECTIVE: Suspected Dandy-Walker continuum anomalies constitute a significant percentage of prenatal cases evaluated by magnetic resonance imaging (MRI). To unify the description of posterior fossa malformations, we sought to establish objective measurements for the posterior fossa in normal fetuses between 18 and 37 weeks gestation. METHODS: T2-weighted images of normal fetal brains in sagittal projection were obtained from fetal magnetic resonance (MR) studies of normal brains performed from 2009 to 2017.121 fetal brains were included in the analysis. Three radiologists reviewed images and recorded the following for each case: superior posterior fossa angle (SPFA), posterior fossa perimeter, and tegmento-vermian angle (TVA). RESULTS: For each feature, the mean of the measurements, the percentage of absolute difference of the reader measurement compared with mean measurement, and the interclass correlation (ICC) were calculated. Values are reported as mean ± standard deviation. Perimeter increases linearly with age, whereas the SPFA and the TVA are independent of gestational age. For all included cases, the SPFA averaged 100.9° ± 8° and the TVA averaged 2.5° ± 2.3°. CONCLUSION: The superior posterior fossa angle, a novel measurement, and the posterior fossa perimeter can be used for establishing the expected size of the posterior fossa in second- and third-trimester fetuses by MRI.

The central nervous system manifestations of localized craniofacial scleroderma: a study of 10 cases and literature review.

BACKGROUND: Localized craniofacial scleroderma is a rare pediatric disease that involves a spectrum of discoloration, fibrosis and hemiatrophy of the face and scalp. Children with localized craniofacial scleroderma may have neurological symptoms, and in this context often undergo diagnostic imaging of the brain. OBJECTIVE: To catalogue neuroimaging abnormalities in patients with localized craniofacial scleroderma treated at our institution, review their clinical courses and compare this data with prior studies. MATERIALS AND METHODS: Following Institutional Review Board approval, an imaging database search identified 10 patients with localized craniofacial scleroderma and neuroimaging abnormalities treated at our institution. Neuroimaging exams and the electronic medical record were reviewed for each case. RESULTS: The most common indications for neuroimaging were headache or seizure (80% of cases). The most common neuroimaging abnormalities were T2-hyperintense, subcortical white matter lesions ipsilateral to the cutaneous lesion (90% of cases) on magnetic resonance imaging (MRI). Calcifications or blood products (50%), cysts (40%) and abnormal enhancement (20%) were also observed. A positron emission tomography (PET) scan obtained for a single case demonstrated diminished 18F-fluorodeoxyglucose (FDG) avidity corresponding to the dominant focus of signal abnormality on MRI. Progressive neuroimaging abnormalities were present in 30% of cases. There was no consistent relationship between changes in neurological symptoms following treatment and neuroimaging findings. CONCLUSION: Our results are similar to previously published data. In the absence of new or worsening neurological symptoms, the role of neuroimaging for follow-up of localized craniofacial scleroderma is unclear. Knowledge of intracranial neuroimaging abnormalities that are commonly associated with localized craniofacial scleroderma helps to distinguish these lesions from others that have similar appearance.

Pilocytic astrocytoma with leptomeningeal spread in a patient with incontinentia pigmenti presenting with unilateral nystagmus.

Incontinentia pigmenti (IP) is a genetic disorder caused by mutations in IKBKG, leading to functional loss of nuclear factor kappa B (NF-ĸB). We report the case of a 6-month-old female child with IP who presented with unilateral nystagmus and was found to have a pilocytic astrocytoma with leptomeningeal spread. Enhanced understanding of the relationship between NF-ĸB, along with its upstream regulators, and tumorigenesis may shed light on whether a subset of patients with IP may be at increased risk for neoplasia.

Mind the gap: an unusual case of a cervical lipomyelocele.

Cervical dysraphism is rare, and the 3 recognized subtypes manifest as cystic, skin-covered masses. To our knowledge, no case of cervical lipomyelocele has been reported in the literature so far. We present a case of surgically and pathologically confirmed cervical lipomyelocele in a patient with spondylocostal dysostosis and multiple other congenital anomalies and a brief review of the literature. In this case, magnetic resonance imaging demonstrates fat extension into a dysraphic cervical spinal canal, allowing for preoperative diagnosis. Computed tomography using 3-dimensional reconstruction serves to more clearly characterize the extensive spine malsegmentation characteristic of spondylocostal dysostosis. The use of this technique is suggested to benefit the orthopedic or neurologic surgeon confronted with such complex malformations.

Prenatal diagnosis of Chudley-McCullough syndrome.

Chudley-McCullough syndrome (CMS) is an autosomal-recessive disorder characterized by a complex brain malformation and profound congenital sensorineural hearing loss. Postnatal brain imaging findings include ventriculomegaly, partial agenesis of corpus callosum, inferior cerebellar dysplasia, arachnoid cysts, and malformations of cortical development including frontal subcortical heterotopia and polymicrogyria. Prenatal diagnosis of CMS is important due to the markedly less severe neurodevelopmental prognosis compared to disorders with similar brain imaging findings. We report prenatal imaging features that help distinguish CMS from other disorders, including slit-like frontal horns, agenesis of the corpus callosum, frontal subcortical heterotopia, arachnoid cysts, and cerebellar dysplasia. © 2016 Wiley Periodicals, Inc.

Cervicothoracic cystic dysraphism.

Cystic dysraphism of the cervical and upper thoracic spine is very rare. It differs from the much more common lumbosacral dysraphism in appearance and structure, and usually portends a better prognosis due to lack of functional neurological tissue in the dysraphic sac and absent or less severe intracranial anomalies. There is ambiguity in the literature regarding terminology because of the paucity of cases. We present cases of the most common type of cervicothoracic cystic dysraphism and emphasize differences from lumbosacral myelomeningocele. Patient outcome depends on the presence of associated anomalies and whether complete surgical resection is performed. Imaging plays a critical role in surgical planning, screening the central nervous system for additional anomalies, and in the postoperative setting for evaluation of retethering.

Recessive Inactivating Mutations in TBCK, Encoding a Rab GTPase-Activating Protein, Cause Severe Infantile Syndromic Encephalopathy.

Infantile encephalopathies are a group of clinically and biologically heterogeneous disorders for which the genetic basis remains largely unknown. Here, we report a syndromic neonatal encephalopathy characterized by profound developmental disability, severe hypotonia, seizures, diminished respiratory drive requiring mechanical ventilation, brain atrophy, dysgenesis of the corpus callosum, cerebellar vermis hypoplasia, and facial dysmorphism. Biallelic inactivating mutations in TBCK (TBC1-domain-containing kinase) were independently identified by whole-exome sequencing as the cause of this condition in four unrelated families. Matching these families was facilitated by the sharing of phenotypic profiles and WES data in a recently released web-based tool (Geno2MP) that links phenotypic information to rare variants in families with Mendelian traits. TBCK is a putative GTPase-activating protein (GAP) for small GTPases of the Rab family and has been shown to control cell growth and proliferation, actin-cytoskeleton dynamics, and mTOR signaling. Two of the three mutations (c.376C>T [p.Arg126(∗)] and c.1363A>T [p.Lys455(∗)]) are predicted to truncate the protein, and loss of the major TBCK isoform was confirmed in primary fibroblasts from one affected individual. The third mutation, c.1532G>A (p.Arg511His), alters a conserved residue within the TBC1 domain. Structural analysis implicated Arg511 as a required residue for Rab-GAP function, and in silico homology modeling predicted impaired GAP function in the corresponding mutant. These results suggest that loss of Rab-GAP activity is the underlying mechanism of disease. In contrast to other disorders caused by dysregulated mTOR signaling associated with focal or global brain overgrowth, impaired TBCK function results in progressive loss of brain volume.

Visual sensory and ocular motor function in children with polymicrogyria: relationship to magnetic resonance imaging.

PURPOSE: To assess visual and ocular motor function in children with polymicrogyria (PMG). METHODS: The medical records of 15 children (0.4-4 years of age) with PMG documented by magnetic resonance imaging (MRI) and with age-corrected visual acuity measured by Teller acuity cards were reviewed retrospectively. Cortical function was assessed by pattern visually evoked potentials (VEP). Ocular motor function was assessed by video-oculography or clinical assessment. Results were compared to age-matched controls. RESULTS: Extent of PMG involvement varied from bilateral fronto-parietal to bilateral-diffuse. Nine children had involvement of the occipital lobe. Visual acuity at presentation was normal in 5 children (≥20/40 Snellen equivalent for age) and subnormal in 10 (average 20/200 equivalent). Visual acuity was similar in children with or without involvement of the occipital lobe (P = 0.4). Follow-up visual acuity was available for 9 children; 3 improved and 6 failed to improve (5 of whom had seizures). PMG involving the occipital lobe significantly reduced VEP amplitude and signal-to-noise ratios. Three infants without visually-guided behaviors had VEP responses. All 3 children with cytomegalovirus-related PMG without retinal disease had preserved visual function despite generalized MRI abnormalities. CONCLUSIONS: All children with PMG had recordable visual function either by visual acuity or VEP testing, however the majority did not show longitudinal improvement in acuity. Seizures may impose limits on visual acuity development. Children with cytomegalovirus-related PMG, microcephaly, and developmental delay can have normal visual acuity. Children with a recordable VEP but without visually guided behaviors may have a defect in sensorimotor transformation.

Two Hundred Thirty-Six Children With Developmental Hydrocephalus: Causes and Clinical Consequences.

Few systematic assessments of developmental forms of hydrocephalus exist. We reviewed magnetic resonance images (MRIs) and clinical records of patients with infancy-onset hydrocephalus. Among 411 infants, 236 had hydrocephalus with no recognizable extrinsic cause. These children were assigned to 1 of 5 subtypes and compared on the basis of clinical characteristics and developmental and surgical outcomes. At an average age of 5.3 years, 72% of children were walking independently and 87% could eat by mouth; in addition, 18% had epilepsy. Distinct patterns of associated malformations and syndromes were observed within each subtype. On average, children with aqueductal obstruction, cysts, and encephaloceles had worse clinical outcomes than those with other forms of developmental hydrocephalus. Overall, 53% of surgically treated patients experienced at least 1 shunt failure, but hydrocephalus associated with posterior fossa crowding required fewer shunt revisions. We conclude that each subtype of developmental hydrocephalus is associated with distinct clinical characteristics, syndromology, and outcomes, suggesting differences in underlying mechanisms.