Full-length isoform concatenation sequencing to resolve cancer transcriptome complexity.

BACKGROUND: Cancers exhibit complex transcriptomes with aberrant splicing that induces isoform-level differential expression compared to non-diseased tissues. Transcriptomic profiling using short-read sequencing has utility in providing a cost-effective approach for evaluating isoform expression, although short-read assembly displays limitations in the accurate inference of full-length transcripts. Long-read RNA sequencing (Iso-Seq), using the Pacific Biosciences (PacBio) platform, can overcome such limitations by providing full-length isoform sequence resolution which requires no read assembly and represents native expressed transcripts. A constraint of the Iso-Seq protocol is due to fewer reads output per instrument run, which, as an example, can consequently affect the detection of lowly expressed transcripts. To address these deficiencies, we developed a concatenation workflow, PacBio Full-Length Isoform Concatemer Sequencing (PB_FLIC-Seq), designed to increase the number of unique, sequenced PacBio long-reads thereby improving overall detection of unique isoforms. In addition, we anticipate that the increase in read depth will help improve the detection of moderate to low-level expressed isoforms. RESULTS: In sequencing a commercial reference (Spike-In RNA Variants; SIRV) with known isoform complexity we demonstrated a 3.4-fold increase in read output per run and improved SIRV recall when using the PB_FLIC-Seq method compared to the same samples processed with the Iso-Seq protocol. We applied this protocol to a translational cancer case, also demonstrating the utility of the PB_FLIC-Seq method for identifying differential full-length isoform expression in a pediatric diffuse midline glioma compared to its adjacent non-malignant tissue. Our data analysis revealed increased expression of extracellular matrix (ECM) genes within the tumor sample, including an isoform of the Secreted Protein Acidic and Cysteine Rich (SPARC) gene that was expressed 11,676-fold higher than in the adjacent non-malignant tissue. Finally, by using the PB_FLIC-Seq method, we detected several cancer-specific novel isoforms. CONCLUSION: This work describes a concatenation-based methodology for increasing the number of sequenced full-length isoform reads on the PacBio platform, yielding improved discovery of expressed isoforms. We applied this workflow to profile the transcriptome of a pediatric diffuse midline glioma and adjacent non-malignant tissue. Our findings of cancer-specific novel isoform expression further highlight the importance of long-read sequencing for characterization of complex tumor transcriptomes.

Oncolytic HSV-1 G207 Immunovirotherapy for Pediatric High-Grade Gliomas.

BACKGROUND: Outcomes in children and adolescents with recurrent or progressive high-grade glioma are poor, with a historical median overall survival of 5.6 months. Pediatric high-grade gliomas are largely immunologically silent or "cold," with few tumor-infiltrating lymphocytes. Preclinically, pediatric brain tumors are highly sensitive to oncolytic virotherapy with genetically engineered herpes simplex virus type 1 (HSV-1) G207, which lacks genes essential for replication in normal brain tissue. METHODS: We conducted a phase 1 trial of G207, which used a 3+3 design with four dose cohorts of children and adolescents with biopsy-confirmed recurrent or progressive supratentorial brain tumors. Patients underwent stereotactic placement of up to four intratumoral catheters. The following day, they received G207 (107 or 108 plaque-forming units) by controlled-rate infusion over a period of 6 hours. Cohorts 3 and 4 received radiation (5 Gy) to the gross tumor volume within 24 hours after G207 administration. Viral shedding from saliva, conjunctiva, and blood was assessed by culture and polymerase-chain-reaction assay. Matched pre- and post-treatment tissue samples were examined for tumor-infiltrating lymphocytes by immunohistologic analysis. RESULTS: Twelve patients 7 to 18 years of age with high-grade glioma received G207. No dose-limiting toxic effects or serious adverse events were attributed to G207 by the investigators. Twenty grade 1 adverse events were possibly related to G207. No virus shedding was detected. Radiographic, neuropathological, or clinical responses were seen in 11 patients. The median overall survival was 12.2 months (95% confidence interval, 8.0 to 16.4); as of June 5, 2020, a total of 4 of 11 patients were still alive 18 months after G207 treatment. G207 markedly increased the number of tumor-infiltrating lymphocytes. CONCLUSIONS: Intratumoral G207 alone and with radiation had an acceptable adverse-event profile with evidence of responses in patients with recurrent or progressive pediatric high-grade glioma. G207 converted immunologically "cold" tumors to "hot." (Supported by the Food and Drug Administration and others; ClinicalTrials.gov number, NCT02457845.).

Postoperative outcomes and stimulation responses for sectioned nerve roots during selective dorsal rhizotomy in cerebral palsy.

BACKGROUND: Cerebral palsy (CP) is the most cause of motor dysfunction in children. Selective dorsal rhizotomy (SDR) plays a major role in long term spasticity control. However, limited data exists on the effect of SDR on postoperative spasticity treatment requirements and supraspinal effects, and the stimulation responses of dorsal nerve roots in those with CP. METHODS: The current study included the outcome for 35 individuals undergoing SDR for motor functional outcome, spasticity, baclofen dose changes, botulinum toxin injection frequency, and spasticity related orthopedic procedures. We also report on the stimulation responses in 112 individuals who underwent SDR at our institution. RESULTS: There was a significant difference in gross motor function measures (GMFM)-66 scores at last follow up that remained present when considering only ambulatory children but not with non-ambulatory children. Ashworth scores were significantly decreased for both upper and lower extremities after SDR at all follow up points. There was a significant decrease in Baclofen dose and botulinum toxin injections requirements after SDR, but no significant difference in the need for orthopedic intervention. A total of 5502 dorsal nerve roots were tested showing a decrease in stimulation intensity and increase in grade on the right side and for descending lumbosacral levels. CONCLUSIONS: SDR improves gross motor scores during short term follow up but has additional benefits in decreasing baclofen dosing and botulinum toxin injections requirements after surgery. They stimulation responses of sectioned dorsal nerve roots adds to the limited available data and our understanding of the pathological changes that occur in CP.

Cerebral revascularization surgery reduces cerebrovascular events in children with sickle cell disease and moyamoya syndrome: Results of the stroke in sickle cell revascularization surgery retrospective study.

BACKGROUND: Recent studies suggest that cerebral revascularization surgery may be a safe and effective therapy to reduce stroke risk in patients with sickle cell disease and moyamoya syndrome (SCD-MMS). METHODS: We performed a multicenter, retrospective study of children with SCD-MMS treated with conservative management alone (conservative group)-chronic blood transfusion and/or hydroxyurea-versus conservative management plus surgical revascularization (surgery group). We monitored cerebrovascular event (CVE) rates-a composite of strokes and transient ischemic attacks. Multivariable logistic regression was used to compare CVE occurrence and multivariable Poisson regression was used to compare incidence rates between groups. Covariates in multivariable models included age at treatment start, age at moyamoya diagnosis, antiplatelet use, CVE history, and the risk period length. RESULTS: We identified 141 patients with SCD-MMS, 78 (55.3%) in the surgery group and 63 (44.7%) in the conservative group. Compared with the conservative group, preoperatively the surgery group had a younger age at moyamoya diagnosis, worse baseline modified Rankin scale scores, and increased prevalence of CVEs. Despite more severe pretreatment disease, the surgery group had reduced odds of new CVEs after surgery (odds ratio = 0.27, 95% confidence interval [CI] = 0.08-0.94, p = .040). Furthermore, comparing surgery group patients during presurgical versus postsurgical periods, CVEs odds were significantly reduced after surgery (odds ratio = 0.22, 95% CI = 0.08-0.58, p = .002). CONCLUSIONS: When added to conservative management, cerebral revascularization surgery appears to reduce the risk of CVEs in patients with SCD-MMS. A prospective study will be needed to validate these findings.

Detection of brain somatic variation in epilepsy-associated developmental lesions.

OBJECTIVE: Epilepsy-associated developmental lesions, including malformations of cortical development and low-grade developmental tumors, represent a major cause of drug-resistant seizures requiring surgical intervention in children. Brain-restricted somatic mosaicism has been implicated in the genetic etiology of these lesions; however, many contributory genes remain unidentified. METHODS: We enrolled 50 children who were undergoing epilepsy surgery into a translational research study. Resected tissue was divided for clinical neuropathologic evaluation and genomic analysis. We performed exome and RNA sequencing to identify somatic variation and we confirmed our findings using high-depth targeted DNA sequencing. RESULTS: We uncovered candidate disease-causing somatic variation affecting 28 patients (56%), as well as candidate germline variants affecting 4 patients (8%). In agreement with previous studies, we identified somatic variation affecting solute carrier family 35 member A2 (SLC35A2) and mechanistic target of rapamycin kinase (MTOR) pathway genes in patients with focal cortical dysplasia. Somatic gains of chromosome 1q were detected in 30% (3 of 10) of patients with Type I focal cortical dysplasia (FCD)s. Somatic variation in mitogen-activated protein kinase (MAPK) pathway genes (i.e., fibroblast growth factor receptor 1 [FGFR1], FGFR2, B-raf proto-oncogene, serine/threonine kinase [BRAF], and KRAS proto-oncogene, GTPase [KRAS]) was associated with low-grade epilepsy-associated developmental tumors. RNA sequencing enabled the detection of somatic structural variation that would have otherwise been missed, and which accounted for more than one-half of epilepsy-associated tumor diagnoses. Sampling across multiple anatomic regions revealed that somatic variant allele fractions vary widely within epileptogenic tissue. Finally, we identified putative disease-causing variants in genes not yet associated with focal cortical dysplasia. SIGNIFICANCE: These results further elucidate the genetic basis of structural brain abnormalities leading to focal epilepsy in children and point to new candidate disease genes.

PTEN somatic mutations contribute to spectrum of cerebral overgrowth.

Phosphatase and tensin homologue (PTEN) regulates cell growth and survival through inhibition of the mammalian target of rapamycin (MTOR) signalling pathway. Germline genetic variation of PTEN is associated with autism, macrocephaly and PTEN hamartoma tumour syndromes. The effect of developmental PTEN somatic mutations on nervous system phenotypes is not well understood, although brain somatic mosaicism of MTOR pathway genes is an emerging cause of cortical dysplasia and epilepsy in the paediatric population. Here we report two somatic variants of PTEN affecting a single patient presenting with intractable epilepsy and hemimegalencephaly that varied in clinical severity throughout the left cerebral hemisphere. High-throughput sequencing analysis of affected brain tissue identified two somatic variants in PTEN. The first variant was present in multiple cell lineages throughout the entire hemisphere and associated with mild cerebral overgrowth. The second variant was restricted to posterior brain regions and affected the opposite PTEN allele, resulting in a segmental region of more severe malformation, and the only neurons in which it was found by single-nuclei RNA-sequencing had a unique disease-related expression profile. This study reveals brain mosaicism of PTEN as a disease mechanism of hemimegalencephaly and furthermore demonstrates the varying effects of single- or bi-allelic disruption of PTEN on cortical phenotypes.

Discovery of clinically relevant fusions in pediatric cancer.

BACKGROUND: Pediatric cancers typically have a distinct genomic landscape when compared to adult cancers and frequently carry somatic gene fusion events that alter gene expression and drive tumorigenesis. Sensitive and specific detection of gene fusions through the analysis of next-generation-based RNA sequencing (RNA-Seq) data is computationally challenging and may be confounded by low tumor cellularity or underlying genomic complexity. Furthermore, numerous computational tools are available to identify fusions from supporting RNA-Seq reads, yet each algorithm demonstrates unique variability in sensitivity and precision, and no clearly superior approach currently exists. To overcome these challenges, we have developed an ensemble fusion calling approach to increase the accuracy of identifying fusions. RESULTS: Our Ensemble Fusion (EnFusion) approach utilizes seven fusion calling algorithms: Arriba, CICERO, FusionMap, FusionCatcher, JAFFA, MapSplice, and STAR-Fusion, which are packaged as a fully automated pipeline using Docker and Amazon Web Services (AWS) serverless technology. This method uses paired end RNA-Seq sequence reads as input, and the output from each algorithm is examined to identify fusions detected by a consensus of at least three algorithms. These consensus fusion results are filtered by comparison to an internal database to remove likely artifactual fusions occurring at high frequencies in our internal cohort, while a "known fusion list" prevents failure to report known pathogenic events. We have employed the EnFusion pipeline on RNA-Seq data from 229 patients with pediatric cancer or blood disorders studied under an IRB-approved protocol. The samples consist of 138 central nervous system tumors, 73 solid tumors, and 18 hematologic malignancies or disorders. The combination of an ensemble fusion-calling pipeline and a knowledge-based filtering strategy identified 67 clinically relevant fusions among our cohort (diagnostic yield of 29.3%), including RBPMS-MET, BCAN-NTRK1, and TRIM22-BRAF fusions. Following clinical confirmation and reporting in the patient's medical record, both known and novel fusions provided medically meaningful information. CONCLUSIONS: The EnFusion pipeline offers a streamlined approach to discover fusions in cancer, at higher levels of sensitivity and accuracy than single algorithm methods. Furthermore, this method accurately identifies driver fusions in pediatric cancer, providing clinical impact by contributing evidence to diagnosis and, when appropriate, indicating targeted therapies.

Efficacy of venetoclax in high risk relapsed mantle cell lymphoma (MCL) - outcomes and mutation profile from venetoclax resistant MCL patients.

Venetoclax is effective in relapsed patients with mantle cell lymphoma (MCL). Mechanisms of resistance to venetoclax in MCL are poorly understood. We describe the clinical outcomes and genomic characteristics of 24 multiply relapsed patients (median of five prior lines of therapy) who received venetoclax-based therapies; 67% had progressed on BTK inhibitors (BTKi) and 54% had blastoid or pleomorphic histology. Median follow up after venetoclax treatment was 17 months. The overall response rate was 50% and complete response (CR) rate was 21%, 16 patients had progressed and 15 died. The median progression free, overall and post venetoclax survival were 8, 13.5 and 7.3 months respectively. Whole-exome sequencing (WES) was performed on samples collected from seven patients (including five pairs; before starting venetoclax and after progression on venetoclax). The SMARCA4 and BCL2 alterations were noted only after progression, while TP53, CDKN2A, KMT2D, CELSR3, CCND1, NOTCH2 and ATM were altered 2-4-fold more frequently after progression. In two patients with serial samples, we demonstrated clonal evolution of novel SMARCA4 and KMT2C/D mutations at progression. Mutation dynamics in venetoclax resistant MCL is demonstrated. Our data indicates that venetoclax resistance in MCL is predominantly associated with non-BCL2 gene mutations. Further studies are ongoing in MCL patients to evaluate the efficacy of venetoclax in combination with other agents and understand the biology of venetoclax resistance in MCL.

Predictors of intracranial hypertension in children undergoing ICP monitoring after severe traumatic brain injury.

PURPOSE: Intracranial hypertension (ICH) is a common and treatable complication after severe traumatic brain injury (sTBI) in children. Describing the incidence and risk factors for developing ICH after sTBI could impact clinical practice. METHODS: Retrospective cohort study from 2006 to 2015 at two university-affiliated level I pediatric trauma centers of children admitted with accidental or abusive TBI, a post-resuscitation Glasgow Coma Score (GCS) of 8 or less, and an invasive intracranial pressure (ICP) monitor. Bivariate and multivariable logistic regression analysis were performed to identify demographic, injury, and imaging characteristics in patients who received ICP directed therapies for ICH (ICP > 20 mmHg). RESULTS: Eight to 5% (271/321) of monitored patients received ICP directed therapy for ICH during their PICU stay. Ninety-seven percent of patients had an abnormality on CT scan by either the Marshall or the Rotterdam score. Of the analyzed clinical and radiologic variables, only presence of hypoxia prior to PICU arrival, female sex, and a higher Injury Severity Score (ISS) were associated with increased risk of ICH (p < 0.05). CONCLUSIONS: In this retrospective study of clinical practice of ICP monitoring in children after sTBI, the vast majority of children had an abnormal CT scan and experienced ICH requiring clinical intervention. Commonly measured clinical variables and radiologic classification scores did not significantly add to the prediction for developing of ICH and further efforts are needed to define low-risk populations that would not develop ICH.

Postoperative Pain Protocol in Children after Selective Dorsal Rhizotomy.

INTRODUCTION: Selective dorsal rhizotomy (SDR) provides lasting relief of spasticity for children suffering from cerebral palsy, although controlling postoperative pain is challenging. Postoperatively, escalation of therapies to include a patient-controlled analgesia (PCA) pump and intensive care unit (ICU) admission is common. OBJECTIVES: We developed a multimodal pain management protocol that included intraoperative placement of an epidural catheter with continuous opioid administration. We present the 3-year results of protocol implementation. METHODS: With institutional review board approval, all patients who were subjected to SDR at our institution were identified for review. Hourly pain scores were recorded. Adverse effects of medication, including desaturation, nausea/vomiting, and pruritus, were also noted. Comparisons were made between patients treated with PCA and those treated with multimodal pain control using t and χ2 tests as appropriate. RESULTS: Thirty-nine patients undergoing the procedure with protocolized pain control (average age 6.8 years, 57% male) were compared to 7 PCA-treated controls (average age 6.6 years, 54% male). Pain control was satisfactory in both groups, with average pain scores of 1.5 in both groups on postoperative day 0, decreasing by postoperative day 3 to 1.1 in the PCA group and 0.5 in the protocol group. No patients under the protocol required ICU admission; all patients with PCA spent at least 1 day in the ICU. Desaturations were seen in 16 patients in the protocol group (41%), but none required ICU transfer. Treatment for pruritis was given to 57% of PCA patients and 15% of protocol patients. Treatment for nausea and vomiting was given to 100% of PCA patients and 51% of protocol patients. Medication requirements for the hospitalization were decreased from 1.1 to 0.28 doses per patient for pruritis, and from 3 to 1.1 doses per patient for nausea. CONCLUSIONS: Multimodal analgesia is an excellent alternative to PCA for postoperative pain after SDR. Actual analgesia is comparative to that of controls without the need for intensive care monitoring. Side effects of high-dose opiates were less frequent and required less medication. With the protocol, patients were safely treated outside the ICU.

Evaluation of pediatric glioma outcomes using intraoperative MRI: a multicenter cohort study.

BACKGROUND: The use of intraoperative MRI (iMRI) during treatment of gliomas may increase extent of resection (EOR), decrease need for early reoperation, and increase progression-free and overall survival, but has not been fully validated, particularly in the pediatric population. OBJECTIVE: To assess the accuracy of iMRI to identify residual tumor in pediatric patients with glioma and determine the effect of iMRI on decisions for resection, complication rates, and other outcomes. METHODS: We retrospectively analyzed a multicenter database of pediatric patients (age ≤ 18 years) who underwent resection of pathologically confirmed gliomas. RESULTS: We identified 314 patients (mean age 9.7 ± 4.6 years) with mean follow-up of 48.3 ± 33.6 months (range 0.03-182.07 months) who underwent surgery with iMRI. There were 201 (64.0%) WHO grade I tumors, 57 (18.2%) grade II, 24 (7.6%) grade III, 9 (2.9%) grade IV, and 23 (7.3%) not classified. Among 280 patients who underwent resection using iMRI, 131 (46.8%) had some residual tumor and underwent additional resection after the first iMRI. Of the 33 tissue specimens sent for pathological analysis after iMRI, 29 (87.9%) showed positive tumor pathology. Gross total resection was identified in 156 patients (55.7%), but this was limited by 69 (24.6%) patients with unknown EOR. CONCLUSIONS: Analysis of the largest multicenter database of pediatric gliomas resected using iMRI demonstrated additional tumor resection in a substantial portion of cases. However, determining the impact of iMRI on EOR and outcomes remains challenging because iMRI use varies among providers nationally. Continued refinement of iMRI techniques for use in pediatric patients with glioma may improve outcomes.

Remifentanil for Sedation of Children With Traumatic Brain Injury.

OBJECTIVE: To determine whether remifentanil would provide adequate sedation while allowing frequent and reproducible neurologic assessments in children admitted to the pediatric intensive care unit (PICU) with traumatic brain injury (TBI) during mechanical ventilation. DESIGN: Retrospective review. SETTING: Tertiary care PICU. PATIENTS: Thirty-eight patients over a 30-month period. MEASUREMENTS AND MAIN RESULTS: Median age was 9 years (interquartile range [IQR] 2.25-12 years). The median Glasgow Coma Scale (GCS) was 9 (IQR: 8-10). All patients were tracheally intubated and receiving mechanical ventilation. A continuous infusion of remifentanil was started at 0.1 µg/kg/min, and bolus doses of 0.25 to 1 µg/kg were administered every 3 to 5 minutes as needed to reach the desired sedation level. Infusions were stopped at least hourly to perform neurologic examinations. The median remifentanil dose was 0.25 µg/kg/min with an IQR of 0.1 and 0.6 µg/kg/min. The maximum dose for any patient in the cohort was 2 µg/kg/min. Median duration of therapy with remifentanil was 20 hours (IQR: 8-44 hours). Adequate sedation was achieved with sedation scores (State Behavioral Scale) meeting target levels with a median value of 100% of the time (IQR: 79%-100%). Neurologic examinations were able to be performed within a median of 9 minutes (IQR: 5-14 minutes) of pausing the infusion. No serious safety events occurred. In 68% of the patients, neurologic examinations remained reassuring during remifentanil infusion, and patients were extubated. The remaining patients were transitioned to traditional sedative agents for long-term management of their traumatic injuries once the neurologic status was deemed stable. CONCLUSION: This data suggest that remifentanil is a suitable sedative agent for use in children with TBI. It provides a rapid onset of sedation with recovery that permits reliable and reproducible clinical examination.

Advanced neuroimaging in traumatic brain injury: an overview.

Traumatic brain injury (TBI) is a common condition with many potential acute and chronic neurological consequences. Standard initial radiographic evaluation includes noncontrast head CT scanning to rapidly evaluate for pathology that might require intervention. The availability of fast, relatively inexpensive CT imaging has fundamentally changed the clinician's ability to noninvasively visualize neuroanatomy. However, in the context of TBI, limitations of head CT without contrast include poor prognostic ability, inability to analyze cerebral perfusion status, and poor visualization of underlying posttraumatic changes to brain parenchyma. Here, the authors review emerging advanced imaging for evaluation of both acute and chronic TBI and include QuickBrain MRI as an initial imaging modality. Dynamic susceptibility-weighted contrast-enhanced perfusion MRI, MR arterial spin labeling, and perfusion CT are reviewed as methods for examining cerebral blood flow following TBI. The authors evaluate MR-based diffusion tensor imaging and functional MRI for prognostication of recovery post-TBI. Finally, MR elastography, MR spectroscopy, and convolutional neural networks are examined as future tools in TBI management. Many imaging technologies are being developed and studied in TBI, and some of these may hold promise in improving the understanding and management of TBI. ABBREVIATIONS ASL = arterial spin labeling; CNN = convolutional neural network; CTP = perfusion CT; DAI = diffuse axonal injury; DMN = default mode network; DOC = disorders of consciousness; DTI = diffusion tensor imaging; FA = fractional anisotropy; fMRI = functional MRI; GCS = Glasgow Coma Scale; MD = mean diffusivity; MRE = MR elastography; MRS = MR spectroscopy; mTBI = mild TBI; NAA = N-acetylaspartate; SWI = susceptibility-weighted imaging; TBI = traumatic brain injury; UHF = ultra-high field.

A whole-genome, radiation hybrid mapping resource of hexaploid wheat.

Generating a contiguous, ordered reference sequence of a complex genome such as hexaploid wheat (2n = 6x = 42; approximately 17 GB) is a challenging task due to its large, highly repetitive, and allopolyploid genome. In wheat, ordering of whole-genome or hierarchical shotgun sequencing contigs is primarily based on recombination and comparative genomics-based approaches. However, comparative genomics approaches are limited to syntenic inference and recombination is suppressed within the pericentromeric regions of wheat chromosomes, thus, precise ordering of physical maps and sequenced contigs across the whole-genome using these approaches is nearly impossible. We developed a whole-genome radiation hybrid (WGRH) resource and tested it by genotyping a set of 115 randomly selected lines on a high-density single nucleotide polymorphism (SNP) array. At the whole-genome level, 26 299 SNP markers were mapped on the RH panel and provided an average mapping resolution of approximately 248 Kb/cR1500 with a total map length of 6866 cR1500 . The 7296 unique mapping bins provided a five- to eight-fold higher resolution than genetic maps used in similar studies. Most strikingly, the RH map had uniform bin resolution across the entire chromosome(s), including pericentromeric regions. Our research provides a valuable and low-cost resource for anchoring and ordering sequenced BAC and next generation sequencing (NGS) contigs. The WGRH developed for reference wheat line Chinese Spring (CS-WGRH), will be useful for anchoring and ordering sequenced BAC and NGS based contigs for assembling a high-quality, reference sequence of hexaploid wheat. Additionally, this study provides an excellent model for developing similar resources for other polyploid species.

Cerebellopontine angle tumors in young children, displaying cranial nerve deficits, and restricted diffusion on diffusion-weighted imaging: a new clinical triad for atypical teratoid/rhabdoid tumors.

Atypical teratoid/rhabdoid tumors (AT/RT) of the central nervous system (CNS) are rare, highly malignant neoplasms that carry a poor prognosis. Even with prompt diagnosis, gross total resection and early initiation of intensive adjuvant therapy, the majority of patients will succumb within 9-12 months of diagnosis. The CPA location in children harbors lesions along a wide spectrum varying from benign to highly malignant. Imaging features of lesions within the CPA that aid the diagnostic process will help to initiate early treatment in higher-grade lesions. We report three cases, in very young children, all with cranial nerve deficits, who displayed CPA lesions with restricted diffusion on diffusion-weighted imaging (DWI) with pathology confirming AT/RT. We propose that in young children with a CPA tumor diffusion-weighted imaging should be routinely evaluated to aid in prompt management. In addition, the diagnosis of AT/RT should be highly suggestive in infants presenting with cranial nerve findings as well as DWI restricted diffusion within the CPA.

Atlantoaxial Rotatory Subluxation in Children.

OBJECTIVES: Pediatric cervical injuries are uncommon. This study was to describe injury circumstances, clinical findings, and management among children diagnosed with atlantoaxial rotatory subluxation (AARS) to aid in its recognition and management. METHODS: Subanalysis of a large case-control study from January 2000 to December 2004 in 17 hospitals in the Pediatric Emergency Care Applied Research Network was performed. Cases were children younger than 16 years with AARS after blunt trauma (n = 55); controls were (a) children with other cervical spine injuries (other CSI, n = 485) and (b) those with normal imaging of the cervical spine (non-CSI, n = 1060). RESULTS: Children with AARS were younger (mean [SD] age, 7.7 [3.8] vs 10.7 [4.6]; Wilcoxon P < 0.01). Falls accounted for 36% of injuries; there were no diving mechanisms (vs other CSI, falls 19%, Fisher exact P < 0.01, and diving 7%, P = 0.04). Children with AARS sought medical care more than 24 hours after the injury event (21% vs 1% for non-CSI controls, P < 0.01). Clinical findings associated with AARS included neck pain (67%) and torticollis (57%) versus other CSI, pain (47%) and torticollis (5%, P < 0.01) for each, and versus non-CSI controls, pain (33%) and torticollis (6%, P < 0.01) for each. Management of AARS included no intervention (n = 6, 11%), soft or rigid collar only (n = 24, 44%), traction (n = 14, 25%), halo (n = 9, 16%), internal fixation (n = 2, 4%), and varied across institutions (P = 0.02). CONCLUSIONS: Children with AARS often have a delayed presentation with neck pain and torticollis; falls are a common injury mechanism. Treatment varied across institutions. Further work is needed to identify optimal management.

Somatic neurofibromatosis type 1 (NF1) inactivation characterizes NF1-associated pilocytic astrocytoma.

Low-grade brain tumors (pilocytic astrocytomas) arising in the neurofibromatosis type 1 (NF1) inherited cancer predisposition syndrome are hypothesized to result from a combination of germline and acquired somatic NF1 tumor suppressor gene mutations. However, genetically engineered mice (GEM) in which mono-allelic germline Nf1 gene loss is coupled with bi-allelic somatic (glial progenitor cell) Nf1 gene inactivation develop brain tumors that do not fully recapitulate the neuropathological features of the human condition. These observations raise the intriguing possibility that, while loss of neurofibromin function is necessary for NF1-associated low-grade astrocytoma development, additional genetic changes may be required for full penetrance of the human brain tumor phenotype. To identify these potential cooperating genetic mutations, we performed whole-genome sequencing (WGS) analysis of three NF1-associated pilocytic astrocytoma (PA) tumors. We found that the mechanism of somatic NF1 loss was different in each tumor (frameshift mutation, loss of heterozygosity, and methylation). In addition, tumor purity analysis revealed that these tumors had a high proportion of stromal cells, such that only 50%-60% of cells in the tumor mass exhibited somatic NF1 loss. Importantly, we identified no additional recurrent pathogenic somatic mutations, supporting a model in which neuroglial progenitor cell NF1 loss is likely sufficient for PA formation in cooperation with a proper stromal environment.

Fentanyl and Midazolam Are Ineffective in Reducing Episodic Intracranial Hypertension in Severe Pediatric Traumatic Brain Injury.

OBJECTIVE: To evaluate the clinical effectiveness of bolus-dose fentanyl and midazolam to treat episodic intracranial hypertension in children with severe traumatic brain injury. DESIGN: Retrospective cohort. SETTING: PICU in a university-affiliated children's hospital level I trauma center. PATIENTS: Thirty-one children 0-18 years of age with severe traumatic brain injury (Glasgow Coma Scale score of ≤ 8) who received bolus doses of fentanyl and/or midazolam for treatment of episodic intracranial hypertension. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The area under the curve from high-resolution intracranial pressure-time plots was calculated to represent cumulative intracranial hypertension exposure: area under the curve for intracranial pressure above 20 mm Hg (area under the curve-intracranial hypertension) was calculated in 15-minute epochs before and after administration of fentanyl and/or midazolam for the treatment of episodic intracranial hypertension. Our primary outcome measure, the difference between predrug and postdrug administration epochs (Δarea under the curve-intracranial hypertension), was calculated for all occurrences. We examined potential covariates including age, injury severity, mechanism, and time after injury; time after injury correlated with Δarea under the curve-intracranial hypertension. In a mixed-effects model, with patient as a random effect, drug/dose combination as a fixed effect, and time after injury as a covariate, intracranial hypertension increased after administration of fentanyl and/or midazolam (overall aggregate mean Δarea under the curve-intracranial hypertension = +17 mm Hg × min, 95% CI, 0-34 mm Hg × min; p = 0.04). The mean Δarea under the curve-intracranial hypertension increased significantly after administration of high-dose fentanyl (p = 0.02), low-dose midazolam (p = 0.006), and high-dose fentanyl plus low-dose midazolam (0.007). Secondary analysis using age-dependent thresholds showed no significant impact on cerebral perfusion pressure deficit (mean Δarea under the curve-cerebral perfusion pressure). CONCLUSIONS: Bolus dosing of fentanyl and midazolam fails to reduce the intracranial hypertension burden when administered for episodic intracranial hypertension. Paradoxically, we observed an overall increase in intracranial hypertension burden following drug administration, even after accounting for within-subject effects and time after injury. Future work is needed to confirm these findings in a prospective study design.

Reduction in Overt and Silent Stroke Recurrence Rate Following Cerebral Revascularization Surgery in Children with Sickle Cell Disease and Severe Cerebral Vasculopathy.

BACKGROUND: Children with sickle cell disease (SCD) and moyamoya may benefit from indirect cerebral revascularization surgery in addition to chronic blood transfusion therapy for infarct prevention. We sought to compare overt and silent infarct recurrence rates in children with SCD undergoing revascularization. METHODS: This was a retrospective cohort study of all children with SCD and moyamoya treated at two children's hospitals. Clinical events and imaging studies were reviewed. RESULTS: Twenty-seven children with SCD and confirmed moyamoya receiving chronic transfusion therapy were identified, of whom 12 underwent indirect cerebral revascularization. Two subjects had postoperative transient ischemic attacks and another had a subarachnoid blood collection, none of which caused permanent consequences. Two subjects had surgical wound infections. Among these 12 children, the rate of overt and silent infarct recurrence decreased from 13.4 infarcts/100 patient-years before revascularization to 0 infarcts/100 patient-years after revascularization (P = 0.0057); the postrevascularization infarct recurrence rate was also significantly lower than the overall infarct recurrence of 8.87 infarcts/100 patient-years in 15 children without cerebral revascularization (P = 0.025). CONCLUSIONS: The rate of overt and silent infarct recurrence was significantly lower following indirect cerebral revascularization. A prospective study of cerebral revascularization in children with SCD is needed.