Mapping neural dynamics underlying saccade preparation and execution and their relation to reaction time and direction errors

Our ability to control and inhibit automatic behaviors is crucial for negotiating complex environments, all of which require rapid communication between sensory, motor, and cognitive networks. Here, we measured neuromagnetic brain activity to investigate the neural timing of cortical areas needed for inhibitory control, while 14 healthy young adults performed an interleaved prosaccade (look at a peripheral visual stimulus) and antisaccade (look away from stimulus) task. Analysis of how neural activity relates to saccade reaction time (SRT) and occurrence of direction errors (look at stimulus on antisaccade trials) provides insight into inhibitory control. Neuromagnetic source activity was used to extract stimulus‐aligned and saccade‐aligned activity to examine temporal differences between prosaccade and antisaccade trials in brain regions associated with saccade control. For stimulus‐aligned antisaccade trials, a longer SRT was associated with delayed onset of neural activity within the ipsilateral parietal eye field (PEF) and bilateral frontal eye field (FEF). Saccade‐aligned activity demonstrated peak activation 10ms before saccade‐onset within the contralateral PEF for prosaccade trials and within the bilateral FEF for antisaccade trials. In addition, failure to inhibit prosaccades on anti‐saccade trials was associated with increased activity prior to saccade onset within the FEF contralateral to the peripheral stimulus. This work on dynamic activity adds to our knowledge that direction errors were due, at least in part, to a failure to inhibit automatic prosaccades. These findings provide novel evidence in humans regarding the temporal dynamics within oculomotor areas needed for saccade programming and the role frontal brain regions have on top‐down inhibitory control.

Tracking Inhibitory Control in Youth With ADHD: A Multi-Modal Neuroimaging Approach

BACKGROUND

A decreased ability to inhibit a speeded motor response is a well-studied deficit in Attention Deficit Hyperactivity Disorder (ADHD), and has been proposed as an endophenotype. Inhibitory control has been assessed reliably with the Stop Signal Task (SST) and is associated with prior documented differences in regional brain function using f-MRI. Here, we advance on these findings by examining their structural connectivity and white matter integrity with the goal of identifying a network underlying a core cognitive deficit in ADHD.

METHODS

Healthy controls (N=16) and youth diagnosed with ADHD (N=60) were recruited through the Province of Ontario Neurodevelopmental Disorders Network (POND) and the Hospital for Sick Children. An f-MRI activation difference map was co-registered with each participant's white matter imaging data, representing the specific network nodes where ADHD youth diverged significantly from controls while performing the SST. Probabilistic tractography was applied from these nodes, and white matter integrity indices such as fractional anisotropy (FA) within the tracts of interest were contrasted between the groups and correlated with SST output measures, including the measure of inhibitory control, the stop signal reaction time (SSRT).

RESULTS

The tracts that connected the network nodes belonged primarily to the inferior fronto-occipital fasciculus (IFOF) and cingulum. ADHD subjects showed trend differences in FA compared to controls between right inferior frontal gyrus (IFG) and right superior temporal gyrus (P= 0.09), right IFG and right posterior cingulate (P= 0.01), right anterior cingulate to posterior cingulate (p= 0.08), and between left middle temporal gyrus (BA 39) and left posterior cingulate (P=0.02). A trend correlation was found between radial diffusivity within IFG to STG white matter (IFOF) and SSRT.

CONCLUSIONS

We identified potential white matter tracts related to deficient inhibitory control, elucidating the brain mechanisms of an important cognitive deficit in ADHD. These findings could be integrated into future endophenotypic biomarker studies, incorporating altogether brain structure, function, and behavior for future studies of ADHD and other psychiatric conditions that exhibit this deficit.

Disrupted network connectivity in pediatric brain tumor survivors is a signature of injury

Cognition is compromised in pediatric brain tumor survivors but the neurophysiological basis of this compromise remains unclear. We hypothesized that reduced neural synchronization across brain networks is involved. To test this, we evaluated group differences using a retrospective cohort comparison design between 24 pediatric brain tumor survivors [11.81 ± 3.27)] and 24 age matched healthy children [12.04 ± 3.28)] in functional connectivity within a cerebellar network to examine local effects of the tumor, a whole brain network to examine diffuse effects of treatment (i.e., chemotherapy and radiation), and across multiple intrinsic connectivity networks. Neural activity was recorded during magnetoencephalography scanning while participants were at rest and functional connectivity within networks was measured using the phase lag index. We corroborated our findings using a computational model representing the local tumor effects on neural synchrony. Compared to healthy children, pediatric brain tumor survivors show increased functional connectivity for theta and beta frequency bands within the cerebellar network and increased functional connectivity for the theta band within the whole brain network that again localized to the cerebellum. Computational modeling showed that increased synchrony in the theta bad is observed following local clustering as well as sparse interarea brain connectivity. We also observed increased functional connectivity for the alpha frequency band in the ventral attention network and decreased functional connectivity within the gamma frequency band in the motor network within paedatric brain tumor survivors versus healthy children. Notably, increased gamma functional connectivity within the motor network predicted decreased reaction time on behavioral tasks in pediatric brain tumor survivors. Disrupted network synchrony may be a signature of neurological injury and disease.

Medulloblastoma has a global impact on health related quality of life: Findings from an international cohort

Background

Understanding the global impact of medulloblastoma on health related quality of life (HRQL) is critical to characterizing the broad impact of this disease and realizing the benefits of modern treatments. We evaluated HRQL in an international cohort of pediatric medulloblastoma patients.

Methods

Seventy‐six patients were selected from 10 sites across North America, Europe, and Asia, who participated in the Medulloblastoma Advanced Genomics International Consortium (MAGIC). The Health Utilities Index (HUI) was administered to patients and/or parents at each site. Responses were used to determine overall HRQL and attributes (ie specific subdomains). The impact of various demographic and medical variables on HRQL was considered—including molecular subgroup.

Results

The majority of patients reported having moderate or severe overall burden of morbidity for both the HUI2 and HUI3 (HUI2 = 60%; HUI3 = 72.1%) when proxy‐assessed. Self‐care in the HUI2 was rated as higher (ie better outcome) for patients from Western versus Eastern sites, P = .02. Patients with nonmetastatic status had higher values (ie better outcomes) for the HUI3 hearing, HUI3 pain, and HUI2 pain, all P < .05. Patients treated with a gross total resection also had better outcomes for the HUI3 hearing (P = .04). However, those who underwent a gross total resection reported having worse outcomes on the HUI3 vision (P = .02). No differences in HRQL were evident as a function of subgroup.

Conclusions

By examining an international sample of survivors, we characterized the worldwide impact of medulloblastoma. This is a critical first step in developing global standards for evaluating long‐term outcomes.

Facial emotion recognition in children treated for posterior fossa tumours and typically developing children: A divergence of predictors

Facial emotion recognition (FER) deficits are evident and pervasive across neurodevelopmental, psychiatric, and acquired brain disorders in children, including children treated for brain tumours. Such deficits are thought to perpetuate challenges with social relationships and decrease quality of life. The present study combined eye-tracking, neuroimaging and cognitive assessments to evaluate if visual attention, brain structure, and general cognitive function contribute to FER in children treated for posterior fossa (PF) tumours (patients: n = 36) and typically developing children (controls: n = 18). To assess FER, all participants completed the Diagnostic Analysis of Nonverbal Accuracy (DANVA2), a computerized task that measures FER using photographs, while their eye-movements were recorded. Patients made more FER errors than controls (p < .01). Although we detected subtle deficits in visual attention and general cognitive function in patients, we found no associations with FER. Compared to controls, patients had evidence of white matter (WM) damage, (i.e., lower fractional anisotropy [FA] and higher radial diffusivity [RD]), in multiple regions throughout the brain (all p < .05), but not in specific WM tracts associated with FER. Despite the distributed WM differences between groups, WM predicted FER in controls only. In patients, factors associated with their disease and treatment predicted FER. Our study provides insight into predictors of FER that may be unique to children treated for PF tumours, and highlights a divergence in associations between brain structure and behavioural outcomes in clinical and typically developing populations; a concept that may be broadly applicable to other neurodevelopmental and clinical populations that experience FER deficits.

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Children treated for brain tumours have difficultly recognizing facial emotions.

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White matter predicts facial emotion recognition (FER) in typical development.

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Medical factors predict FER deficits in children treated for brain tumours.

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Brain-behaviour relations can diverge in the typical and atypical developing brain.

White matter plasticity and maturation in human cognition

White matter plasticity likely plays a critical role in supporting cognitive development. However, few studies have used the imaging methods specific to white matter tissue structure or experimental designs sensitive to change in white matter necessary to elucidate these relations. Here we briefly review novel imaging approaches that provide more specific information regarding white matter microstructure. Furthermore, we highlight recent studies that provide greater clarity regarding the relations between changes in white matter and cognition maturation in both healthy children and adolescents and those with white matter insult. Finally, we examine the hypothesis that white matter is linked to cognitive function via its impact on neural synchronization. We test this hypothesis in a population of children and adolescents with recurrent demyelinating syndromes. Specifically, we evaluate group differences in white matter microstructure within the optic radiation; and neural phase synchrony in visual cortex during a visual task between 25 patients and 28 typically developing age-matched controls. Children and adolescents with demyelinating syndromes show evidence of myelin and axonal compromise and this compromise predicts reduced phase synchrony during a visual task compared to typically developing controls. We investigate one plausible mechanism at play in this relationship using a computational model of gamma generation in early visual cortical areas. Overall, our findings show a fundamental connection between white matter microstructure and neural synchronization that may be critical for cognitive processing. In the future, longitudinal or interventional studies can build upon our knowledge of these exciting relations between white matter, neural communication, and cognition.

Cognitive Implications of Ototoxicity in Pediatric Patients With Embryonal Brain Tumors

PURPOSE

Sensorineural hearing loss (SNHL) is associated with intellectual and academic declines in children treated for embryonal brain tumors. This study expands upon existing research by examining core neurocognitive processes that may result in reading difficulties in children with treatment-related ototoxicity.

PATIENTS AND METHODS

Prospectively gathered, serial, neuropsychological and audiology data for 260 children and young adults age 3 to 21 years (mean, 9.15 years) enrolled in a multisite research and treatment protocol, which included surgery, risk-adapted craniospinal irradiation (average risk, n = 186; high risk, n = 74), and chemotherapy, were analyzed using linear mixed models. Participants were assessed at baseline and up to 5 years after diagnosis and grouped according to degree of SNHL. Included were 196 children with intact hearing or mild to moderate SNHL (Chang grade 0, 1a, 1b, or 2a) and 64 children with severe SNHL (Chang grade 2b or greater). Performance on eight neurocognitive variables targeting reading outcomes (eg, phonemics, fluency, comprehension) and contributory cognitive processes (eg, working memory, processing speed) was analyzed.

RESULTS

Participants with severe SNHL performed significantly worse on all variables compared with children with normal or mild to moderate SNHL (P ≤ .05), except for tasks assessing awareness of sounds and working memory. Controlling for age at diagnosis and risk-adapted craniospinal irradiation dose, performance on the following four variables remained significantly lower for children with severe SNHL: phonemic skills, phonetic decoding, reading comprehension, and speed of information processing (P ≤ .05).

CONCLUSION

Children with severe SNHL exhibit greater reading difficulties over time. Specifically, they seem to struggle most with phonological skills and processing speed, which affect higher level skills such as reading comprehension.

Survival and functional outcomes of molecularly defined childhood posterior fossa ependymoma: Cure at a cost

BACKGROUND

Posterior fossa ependymoma (PFE) comprises 2 groups, PF group A (PFA) and PF group B (PFB), with stark differences in outcome. However, to the authors' knowledge, the long-term outcomes of PFA ependymoma have not been described fully. The objective of the current study was to identify predictors of survival and neurocognitive outcome in a large consecutive cohort of subgrouped patients with PFE over 30 years.

METHODS

Demographic, survival, and neurocognitive data were collected from consecutive patients diagnosed with PFE from 1985 through 2014 at the Hospital for Sick Children in Toronto, Ontario, Canada. Subgroup was assigned using genome-wide methylation array and/or immunoreactivity to histone H3 K27 trimethylation (H3K27me3).

RESULTS

A total of 72 PFE cases were identified, 89% of which were PFA. There were no disease recurrences noted among patients with PFB. The 10-year progression-free survival rate for all patients with PFA was poor at 37.1% (95% confidence interval, 25.9%-53.1%). Analysis of consecutive 10-year epochs revealed significant improvements in progression-free survival and/or overall survival over time. This pertains to the increase in the rate of gross (macroscopic) total resection from 35% to 77% and the use of upfront radiotherapy increasing from 65% to 96% over the observed period and confirmed in a multivariable model. Using a mixed linear model, analysis of longitudinal neuropsychological outcomes restricted to patients with PFA who were treated with focal irradiation demonstrated significant continuous declines in the full-scale intelligence quotient over time with upfront conformal radiotherapy, even when correcting for hydrocephalus, number of surgeries, and age at diagnosis (-1.33 ± 0.42 points/year; P = .0042).

CONCLUSIONS

Data from a molecularly informed large cohort of patients with PFE clearly indicate improved survival over time, related to more aggressive surgery and upfront radiotherapy. However, to the best of the authors' knowledge, the current study is the first, in a subgrouped cohort, to demonstrate that this approach results in reduced neurocognitive outcomes over time.

Early changes in white matter predict intellectual outcome in children treated for posterior fossa tumors

Purpose

Prospective and longitudinal neuroimaging studies of posterior fossa tumors are scarce. Here we evaluate the early changes in white matter and intellectual outcome up to 3 years after diagnosis.

Patients and methods

Twenty-two children with posterior fossa tumors and 24 similarly-aged healthy children participated. Patients included: (a) 12 individuals who received surgery, cranial-spinal radiation (CSR), and focal radiation to the tumor bed (CSR group) and (b) 10 individuals who received local therapy, either surgery only or surgery and focal radiation to the tumor bed (Local group). Diffusion tensor imaging (DTI) and intelligence measures were obtained an average of 3 months after diagnosis and then at 12, 24, and 36 months later. DTI tractography and voxel-wise approaches were employed. The Neurological Predictor Scale was used to summarize the type and amount of treatment for PF tumor patients. Linear mixed modelling was used to evaluate group differences at baseline and changes over time in DTI metrics for both the specific white matter tracts and voxel-wise, as well as for intelligence measures.

Results

Based on tractography, patients treated with CSR had significantly higher Axial and Mean diffusivity in the cortical-spinal tracts (CST) 3 month after diagnosis – particularly on the right side, p < .003, compared to healthy children. Mean diffusivity in right CST decreased over time in this group of patients, p = .001. No differences compared to controls were evident in specific tracts for the Local group, p > .10. Voxel-wise analyses revealed multiple areas of white matter compromise in both patients groups. Notably, both patient groups had lower scores on intelligence measures compared to the Control group: The CSR group displayed lower performance 3 months following diagnosis, ps < 0.001, and their performance remained stable over time ps > 0.10, whereas the Local group displayed no differences at 3 months, ps> 0.10, but their performance declined over time, ps < 0.01. At baseline, higher MD in right CST predicted lower Perceptual Reasoning scores across all participants, p = .001. Furthermore, lower FA in left IFOF at baseline predicted decline in Processing Speed over time, p = .001. In patients, more aggressive treatment protocols and presence of mutism were related to lower performance on intelligence measures at baseline, ps < 0.04.

Conclusions

Children treated with CSR displayed diffuse white matter compromise and poor intellectual outcome shortly after radiation treatment. There was evidence of subsequent growth of white matter structure, but stable intellectual insult. Conversely, in children treated with either surgery only or surgery and focal radiation to the tumor bed we observed less compromise of white matter early following treatment and no intellectual insult compared to healthy children. However, declines in intellectual function were evident for these children, though their performance remained within the average normative range. Overall, results suggest that early intervention is necessary to circumvent these deficits.

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There are early deficits to intellect and white matter shortly after treatment

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Early deficits were observed only after cranial-spinal radiation

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Intellectual deficits are generally stable over time

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White matter indices, mutism, and treatment predicted intellectual outcome

Posterior fossa syndrome and long-term neuropsychological outcomes among children treated for medulloblastoma on a multi-institutional, prospective study

Background

Patients treated for medulloblastoma who experience posterior fossa syndrome (PFS) demonstrate increased risk for neurocognitive impairment at one year post diagnosis. The aim of the study was to examine longitudinal trajectories of neuropsychological outcomes in patients who experienced PFS compared with patients who did not.

Methods

Participants were 36 patients (22 males) who experienced PFS and 36 comparison patients (21 males) who were matched on age at diagnosis and treatment exposure but did not experience PFS. All patients underwent serial evaluation of neurocognitive functioning spanning 1 to 5 years post diagnosis.

Results

The PFS group demonstrated lower estimated mean scores at 1, 3, and 5 years post diagnosis on measures of general intellectual ability, processing speed, broad attention, working memory, and spatial relations compared with the non-PFS group. The PFS group exhibited estimated mean scores that were at least one standard deviation below the mean for intellectual ability, processing speed, and broad attention across all time points and for working memory by 5 years post diagnosis. Processing speed was stable over time. Attention and working memory declined over time. Despite some change over time, caregiver ratings of executive function and behavior problem symptoms remained within the average range.

Conclusion

Compared with patients who do not experience PFS, patients who experience PFS exhibit greater neurocognitive impairment, show little recovery over time, and decline further in some domains. Findings highlight the particularly high risk for long-term neurocognitive problems in patients who experience PFS and the need for close follow-up and intervention.

Development of short-range white matter in healthy children and adolescents

Neural communication is facilitated by intricate networks of white matter (WM) comprised of both long and short range connections. The maturation of long range WM connections has been extensively characterized, with projection, commissural, and association tracts showing unique trajectories with age. There, however, remains a limited understanding of age-related changes occurring within short range WM connections, or U-fibers. These connections are important for local connectivity within lobes and facilitate regional cortical function and greater network economy. Recent studies have explored the maturation of U-fibers primarily using cross-sectional study designs. Here, we analyzed diffusion tensor imaging (DTI) data for healthy children and adolescents in both a cross-sectional (n = 78; mean age = 13.04 ± 3.27 years) and a primarily longitudinal (n = 26; mean age = 10.78 ± 2.69 years) cohort. We found significant age-related differences in fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD) and radial diffusivity (RD) across the frontal, parietal, and temporal lobes of participants within the cross-sectional cohort. By contrast, we report significant age-related differences in only FA for participants within the longitudinal cohort. Specifically, larger FA values were observed with age in frontal, parietal, and temporal lobes of the left hemisphere. Our results extend previous findings restricted to long range WM to demonstrate regional changes in the microstructure of short range WM during childhood and adolescence. These changes possibly reflect continued myelination and axonal organization of short range WM with increasing age in more anterior regions of the left hemisphere. Hum Brain Mapp 39:204-217, 2018. © 2017 Wiley Periodicals, Inc.

Exercise training for neural recovery in a restricted sample of pediatric brain tumor survivors: a controlled clinical trial with crossover of training versus no training

Background

Exercise promotes repair processes in the mouse brain and improves cognition in both mice and humans. It is not known whether these benefits translate to human brain injury, particularly the significant injury observed in children treated for brain tumors.

Methods

We conducted a clinical trial with crossover of exercise training versus no training in a restricted sample of children treated with radiation for brain tumors. The primary outcome was change in brain structure using MRI measures of white matter (ie, fractional anisotropy [FA]) and hippocampal volume [mm3]). The secondary outcome was change in reaction time (RT)/accuracy across tests of attention, processing speed, and short-term memory. Linear mixed modeling was used to test the effects of time, training, training setting, and carryover.

Results

Twenty-eight participants completed training in either a group (n=16) or a combined group/home (n=12) setting. Training resulted in increased white matter FA (Δ=0.05, P<.001). A carryover effect was observed for participants ~12 weeks after training (Δ=0.05, P<.001). Training effects were observed for hippocampal volume (Δ=130.98mm3; P=.001) and mean RT (Δ=-457.04ms, P=0.36) but only in the group setting. Related carryover effects for hippocampal volume (Δ=222.81mm3, P=.001), and RT (Δ=-814.90ms, P=.005) were also observed. Decreased RT was predicted by increased FA (R=-0.62, P=.01). There were no changes in accuracy.

Conclusions

Exercise training is an effective means for promoting white matter and hippocampal recovery and improving reaction time in children treated with cranial radiation for brain tumors.

Repetitive Transcranial Magnetic Stimulation for the Treatment of Executive Function Deficits in Autism Spectrum Disorder: Clinical Trial Approach

OBJECTIVE

Executive function (EF) deficits in patients with autism spectrum disorder (ASD) are ubiquitous and understudied. Further, there are no effective, neuroscience-based treatments to address this impairing feature of ASD. Repetitive transcranial magnetic stimulation (rTMS) has demonstrated promise in addressing EF deficits in adult neuropsychiatric disorders. This article will outline the design of a novel randomized-controlled trial of bilateral, 20 Hz, rTMS applied to the dorsolateral prefrontal cortex (DLPFC) for treatment of EF deficits in ASD that is currently ongoing. We describe prior therapeutic rTMS research for ASD and prior rTMS trials targeting EFs in adult neuropsychiatric disorders. A neurophysiological rationale for rTMS treatment of EF deficits in ASD is presented.

METHODS

An ongoing protocol will enroll participants aged 16-35 with ASD and no intellectual disability. Psychotropic medications will be continued during the 4-week trial of active 20 Hz versus sham rTMS applied to the DLPFC. Twenty, active treatment sessions consisting of 25 stimulation trains at a 90% motor threshold will be administered. The primary outcome measure is the Cambridge Neuropsychological Test Automated Battery (CANTAB) spatial working memory task. At present, recruitment, enrollment, and treatment within the described clinical trial are ongoing.

CONCLUSIONS

EF deficits are common and impairing symptoms of ASD. There are no evidence-based treatments for EF deficits in ASD. The protocol described here will provide important preliminary data on the feasibility and efficacy of 20 Hz rTMS to DLPFC for EF deficits in ASD.

Neurocognitive outcome in children with sensorineural hearing loss after treatment of malignant embryonal brain tumors

2029

Background: Neurological side effects associated with childhood brain tumors and their treatments contribute to long term neurocognitive morbidity. The aims of this study were to identify the incidence of sensorineural hearing loss (SNHL) in a large sample of children treated for malignant brain tumors, and to evaluate the potential relationship between SNHL and intellectual functioning following the completion of treatment. Methods: We conducted a prospective follow-up study at a single center with review of 119 patients treated for embryonal brain tumors at the Hospital for Sick Children, between 1996-2015, to analyze the impact of significant SNHL (Chang > 2b) on intellectual function. Hearing was assessed post-treatment (median age: 13.5y (+4.5)) and the median age for neurocognitive testing was 12.8y (+ 4.1). The median interval from time of diagnosis was 5.8y (+ 3.7). Results: Severe SNHL was identified in half the patients (50.4%, n = 60/119). We identified a subset of patients (n = 61) who had assessments of intellectual function. In this cohort, intellectual function was significantly poorer in the group with severe SNHL, even after controlling for the effect of craniospinal radiation (severe SNHL 22.4 Gy + 13.3, no or mild hearing loss 20.4 Gy +12.8) and boost dose and volume. Children experiencing severe SNHL had lower overall IQ (severe SNHL 72.4 + 16.6; no/mild hearing loss 92.0 + 20.5) p < 0.001 and in significantly lower verbal comprehension (severe SNHL 78.7 + 15.9; no/mild hearing loss 94.7 + 13.8) p < 0.001, and working memory (severe SNHL 78.2+ 17.6; no/mild hearing loss 94.8 + 16.4) p < 0.001, scores. Conclusions: Hearing loss is a much more significant complication in children with embryonal brain tumors than previously estimated. We show the profound impact of hearing loss on intellectual deficit in children. Namely, patients with severe SNHL have difficulty using and understanding verbal language, and they have a reduced ability to concentrate and manipulate information in short-term memory. Our results have implications on future trial designs and follow-up of children treated for embryonal brain tumors.

Intellectual Outcome in Molecular Subgroups of Medulloblastoma

Purpose

To evaluate intellectual functioning and the implications of limiting radiation exposure in the four biologically distinct subgroups of medulloblastoma: wingless (WNT), sonic hedgehog (SHH), Group 3, and Group 4.

Patients and Methods

A total of 121 patients with medulloblastoma (n = 51, Group 4; n = 25, Group 3; n = 28, SHH; and n = 17, WNT), who were treated between 1991 and 2013 at the Hospital for Sick Children (Toronto, Ontario, Canada), Children’s National Health System (Washington, DC), or the Lucile Packard Children’s Hospital (Palo Alto, CA), had intellectual assessments. First, we compared intellectual trajectories between subgroups. Next, we evaluated the effect of treatment with reduced-dose craniospinal irradiation (CSI) plus a tumor bed boost versus treatments that deliver higher CSI doses and/or larger boost volumes to the brain (all other treatments) within subgroups. Linear mixed modeling was used to determine the stability or change in intelligence scores over time.

Results

Intellectual outcomes declined comparably in each subgroup except for processing speed; SHH declined less than Group 3 ( P = .04). SHH had the lowest incidence of cerebellar mutism and motor deficits. Treatment with reduced-dose CSI plus a tumor bed boost was associated with preserved intellectual functioning in WNT and Group 4 patients considered together (ie, subgroups containing patients who are candidates for therapy de-escalation), and not in Group 3 or SHH. Across all subgroups, patients in the all other treatments group declined over time (all P < .05).

Conclusion

SHH patients appear to have the most distinct functional (ie, motor deficits and mutism) outcomes and a unique processing speed trajectory. Only WNT and Group 4 patients seem to benefit from limiting radiation exposure. Our findings highlight the value of conducting subgroup-specific analyses, and can be used to inform novel biologically based treatment protocols for patients with medulloblastoma.

Vulnerability of white matter to insult during childhood: evidence from patients treated for medulloblastoma

OBJECTIVE Craniospinal irradiation damages the white matter in children treated for medulloblastoma, but the treatment-intensity effects are unclear. In a cross-sectional retrospective study, the effects of treatment with the least intensive radiation protocol versus protocols that delivered more radiation to the brain, in addition to the effects of continuous radiation dose, on white matter architecture were evaluated. METHODS Diffusion tensor imaging was used to assess fractional anisotropy, mean diffusivity, radial diffusivity, and axial diffusivity. First, regional white matter analyses and tract-based spatial statistics were conducted in 34 medulloblastoma patients and 38 healthy controls. Patients were stratified according to those treated with 1) the least intensive radiation protocol, specifically reduced-dose craniospinal irradiation plus a boost to the tumor bed only (n = 17), or 2) any other dose and boost combination that delivered more radiation to the brain, which was also termed the "all-other-treatments" group (n = 17), and comprised patients treated with standard-dose craniospinal irradiation plus a posterior fossa boost, standard-dose craniospinal irradiation plus a tumor bed boost, or reduced-dose craniospinal irradiation plus a posterior fossa boost. Second, voxel-wise dose-distribution analyses were conducted on a separate cohort of medulloblastoma patients (n = 15). RESULTS The all-other-treatments group, but not the reduced-dose craniospinal irradiation plus tumor bed group, had lower fractional anisotropy and higher radial diffusivity than controls in all brain regions (all p < 0.05). The reduced-dose craniospinal irradiation plus tumor bed boost group had higher fractional anisotropy (p = 0.05) and lower radial diffusivity (p = 0.04) in the temporal region, and higher fractional anisotropy in the frontal region (p = 0.04), than the all-other-treatments group. Linear mixed-effects modeling revealed that the dose and age at diagnosis together 1) better predicted fractional anisotropy in the temporal region than models with either alone (p < 0.005), but 2) did not better predict fractional anisotropy in comparison with dose alone in the occipital region (p > 0.05). CONCLUSIONS Together, the results show that white matter damage has a clear association with increasing radiation dose, and that treatment with reduced-dose craniospinal irradiation plus tumor bed boost appears to preserve white matter in some brain regions.

Prognostic value of medulloblastoma extent of resection after accounting for molecular subgroup: a retrospective integrated clinical and molecular analysis

Background

Incomplete surgical resection of medulloblastoma is controversially considered a marker of high-risk disease; driving aggressive surgical resections, “second-look” surgeries, and/or intensified chemoradiotherapy. All prior publications evaluating the clinical importance of extent of resection (EOR) failed to account for molecular subgroup. We analysed the prognostic value of EOR across 787 medulloblastoma samples in a subgroup-specific manner.

Methods

We retrospectively identified patients from Medulloblastoma Advanced Genomics International Consortium (MAGIC) centres with a histological diagnosis of medulloblastoma and complete extent of resection and survival data. Specimens were collected from 35 international institutions. Medulloblastoma subgroup affiliation was determined using nanoString gene expression profiling on frozen or formalin-fixed paraffin-embedded tissues. Extent of resection (EOR) based on post-operative imaging was classified as gross total (GTR), near total (NTR, <1·5cm²), or subtotal (STR, ≥ 1·5cm²). Overall survival (OS) and progression-free survival (PFS) multivariable analyses including subgroup, age, metastatic status, geographical location of therapy (North America/Australia vs world), and adjuvant therapy regimen were performed. The primary endpoint was the impact of surgical EOR by molecular subgroup and other clinical variables on OS and PFS.

Findings

787 medulloblastoma patients (86 WNT, 242 SHH, 163 Group 3, and 296 Group 4) were included in a multivariable Cox model of PFS and OS. The marked benefit of EOR in the overall cohort was greatly attenuated after including molecular subgroup in the multivariable analysis. There was an observed PFS benefit of GTR over STR (hazard ration [HR] 1·45, 95% CI; 1·07–1·96, p=0·02) but there was no observed PFS or OS benefit of GTR over NTR (HR 1·05, 0·71–1·53, p=0·82 and HR 1·14, 0·75–1·72, p=0.55). There was no statistically significant survival benefit to greater EOR for patients with WNT, SHH, or Group 3 patients (HR 1·03, 0·67–1·58, p=0·9 for STR vs. GTR). There was a PFS benefit for GTR over STR in patients with Group 4 medulloblastoma (HR1·97, 1·22–3·17, p=0·01), particularly those with metastatic disease (HR 2·22, 1–4·93, p=0·05). A nomogram based on this multivariable cox proportional hazards model shows the comparably smaller impact of EOR on relative risk for PFS and OS than subgroup affiliation, metastatic status, radiation dose, and adjuvant chemotherapy.

Interpretation

The prognostic benefit of EOR for patients with medulloblastoma is attenuated after accounting for molecular subgroup affiliation. Although maximal safe surgical resection should remain the standard of care, surgical removal of small residual portions of medulloblastoma is not recommended when the likelihood of neurological morbidity is high as there is no definitive benefit to GTR over NTR. Our results suggest a re-evaluation of the long-term implications of intensified craniospinal irradiation (36 Gy) in children with small residual portions of medulloblastoma.

Funding

Funding Canadian Cancer Society Research Institute, Terry Fox Research Institute, Canadian Institutes of Health Research, National Institutes of Health, Pediatric Brain Tumor Foundation, Garron Family Chair in Childhood Cancer Research.

Relationship between ventricular size, white matter injury, and neurocognition in children with stable, treated hydrocephalus

OBJECT

Larger-than-normal ventricles can persist in children following hydrocephalus treatment, even if they are asymptomatic and clinically well. This study aims to answer the following question: do large ventricles result in brain injuries that are detectable on diffusion tensor imaging (DTI) and/or in measurable neurocognitive deficits in children with stable, treated hydrocephalus that are not seen in children with small ventricles?

METHODS

For this prospective study, we recruited 23 children (age range 8-18 years) with hydrocephalus due to aqueductal stenosis or tectal glioma who were asymptomatic following hydrocephalus treatment that had been performed at least 2 years earlier. All patients underwent detailed DTI and a full battery of neuropsychological tests. Correlation analysis was performed to assess the relationship between DTI parameters, neurocognitive tests, and ventricular size. The false-discovery rate method was used to adjust for multiple comparisons.

RESULTS

The median age of these 23 children at the time of assessment was 15.0 years (interquartile range [IQR] 12.1-17.6 years), and the median age at the first hydrocephalus treatment was 5.8 years (IQR 2.2 months-12.8 years). At the time of assessment, 17 children had undergone endoscopic third ventriculostomy and 6 children had received a shunt. After adjusting for multiple comparisons, there were no significant correlations between any neurocognitive test and ventricular volume, any DTI parameter and ventricular volume, or any DTI parameter and neurocognitive test.

CONCLUSIONS

Our data do not show an association between large ventricular size and additional white matter injury or worse neurocognitive deficits in asymptomatic children with stable, treated hydrocephalus caused by a discrete blockage of the cerebral aqueduct. Further investigations using larger patient samples are needed to validate these results.