Intellectual changes after radiation for children with brain tumors: which brain structures are most important?

Pediatric CNS Radiation Oncology: Recent Developments and Novel Techniques

Radiation therapy (RT) is a cornerstone in the management of pediatric central nervous system (CNS) tumors. Recent advancements in RT delivery and techniques aim to enhance therapeutic effectiveness while minimizing both acute and long-term complications associated with pediatric brain RT. This paper highlights innovative developments in the field, including the clinical indications, benefits, and challenges of proton therapy and stereotactic radiotherapy. The ongoing refinement of risk-adapted RT volumes is highlighted, with examples of newly proposed germinoma RT volumes and hippocampal-sparing RT. Additionally, emerging experimental approaches, including FLASH therapy and theranostics, are also discussed as promising future directions. Further prospective, multi-institutional collaborative studies are essential to validate and expand upon the benefits outlined in this review.

Neuropsychological Late Effects and Quality-of-Life Outcomes in Pediatric Brain Tumor Survivors: Role of Pediatric Neurologists in Monitoring and Management

Pediatric brain tumor (PBT) survivors are at significantly increased risk of cognitive, psychosocial, and educational/vocational sequelae that impact health-related quality of life. These complications and health morbidities result in high burden on survivors and their families, particularly those already vulnerable to disparities in health care access and outcomes. Since neurological comorbidities are common in this population, neurologists are uniquely positioned to screen, treat identified symptoms, and connect families with services and resources. A tiered assessment approach can facilitate early identification of concerns and reduce barriers to care. We review common presenting conditions, highlight risk factors, and provide screening tools and recommendations to facilitate comprehensive survivorship care for PBT survivors.

Risk factors for domain-specific neurocognitive outcome in pediatric survivors of a brain tumor in the posterior fossa-Results of the HIT 2000 trial

BACKGROUND

Neurocognition can be severely affected in pediatric brain tumor survivors. We analyzed the association of cognitive functioning with radiotherapy dose, postoperative cerebellar mutism syndrome (pCMS), hydrocephalus, intraventricular methotrexate (MTX) application, tumor localization, and biology in pediatric survivors of a posterior fossa tumor.

METHODS

Subdomain-specific neurocognitive outcome data from 279 relapse-free survivors of the HIT-2000 trial (241 medulloblastoma and 38 infratentorial ependymoma) using the Neuropsychological Basic Diagnostic tool based on Cattell-Horn-Carroll's model for intelligence were analyzed.

RESULTS

Cognitive performance 5.14 years (mean; range = 1.52-13.02) after diagnosis was significantly below normal for all subtests. Processing speed and psychomotor abilities were most affected. Influencing factors were domain-specific: CSI-dose had a strong impact on most subtests. pCMS was associated with psychomotor abilities (β = -0.25 to -0.16) and processing speed (β = -0.32). Postoperative hydrocephalus correlated with crystallized intelligence (β = -0.20) and short-term memory (β = -0.15), age with crystallized intelligence (β = 0.15) and psychomotor abilities (β = -0.16 and β = -0.17). Scores for fluid intelligence (β = -0.23), short-term memory (β = -0.17) and visual processing (β = -0.25) declined, and scores for selective attention improved (β = 0.29) with time after diagnosis.

CONCLUSIONS

The dose of CSI was strongly associated with neurocognitive outcomes. Low psychomotor abilities and processing speed both in patients treated with and without CSI suggest a strong contribution of the tumor and its surgery on these functions. Future research therefore should analyze strategies to both reduce CSI dose and toxicity caused by other treatment modalities.

Clinical significance of cerebral microbleeds in patients with germinoma who underwent long-term follow-up

PURPOSE

This study identified the factors affecting cerebral microbleed (CMBs) development. Moreover, their effects on intelligence and memory and association with stroke in patients with germinoma who had long-term follow-up were evaluated.

METHODS

This study included 64 patients with germinoma who were histologically and clinically diagnosed with and treated for germinoma. These patients were evaluated cross-sectionally, with a focus on CMBs on susceptibility-weighted magnetic resonance imaging (SWI), brain atrophy assessed through volumetric analysis, and intelligence and memory.

RESULTS

The follow-up period was from 32 to 412 (median: 175.5) months. In total, 43 (67%) patients had 509 CMBs and 21 did not have CMBs. Moderate correlations were observed between the number of CMBs and time from initial treatments and recurrence was found to be a risk factor for CMB development. Increased temporal CMBs had a marginal effect on the processing speed and visual memory, whereas brain atrophy had a statistically significant effect on verbal, visual, and general memory and a marginal effect on processing speed. Before SWI acquisition and during the follow-up periods, eight strokes occurred in four patients. All of these patients had ≥ 15 CMBs on SWI before stroke onset. Meanwhile, 33 patients with < 14 CMBs or 21 patients without CMBs did not experience stroke.

CONCLUSION

Patients with a longer time from treatment initiation had a higher number of CMBs, and recurrence was a significant risk factor for CMB development. Furthermore, brain atrophy had a stronger effect on memory than CMBs. Increased CMBs predict the stroke onset.

A Prospective Study of Machine Learning-Assisted Radiation Therapy Planning for Patients Receiving 54 Gy to the Brain

PURPOSE

The capacity for machine learning (ML) to facilitate radiation therapy (RT) planning for primary brain tumors has not been described. We evaluated ML-assisted RT planning with regard to clinical acceptability, dosimetric outcomes, and planning efficiency for adults and children with primary brain tumors.

METHODS AND MATERIALS

In this prospective study, children and adults receiving 54 Gy fractionated RT for a primary brain tumor were enrolled. For each patient, one ML-assisted RT plan was created and compared with 1 or 2 plans created using standard ("manual") planning procedures. Plans were evaluated by the treating oncologist, who was blinded to the method of plan creation. The primary endpoint was the proportion of ML plans that were clinically acceptable for treatment. Secondary endpoints included the frequency with which ML plans were selected as preferable for treatment, and dosimetric differences between ML and manual plans.

RESULTS

A total of 116 manual plans and 61 ML plans were evaluated across 61 patients. Ninety-four percent of ML plans and 93% of manual plans were judged to be clinically acceptable (P = 1.0). Overall, the quality of ML plans was similar to manual plans. ML plans comprised 34.5% of all plans evaluated and were selected for treatment in 36.1% of cases (P = .82). Similar tumor target coverage was achieved between both planning methods. Normal brain (brain minus planning target volume) received an average of 1 Gy less mean dose with ML plans (compared with manual plans, P < .001). ML plans required an average of 45.8 minutes less time to create, compared with manual plans (P < .001).

CONCLUSIONS

ML-assisted automated planning creates high-quality plans for patients with brain tumors, including children. Plans created with ML assistance delivered slightly less dose to normal brain tissues and can be designed in less time.

Proton Therapy Mediates Dose Reductions to Brain Structures Associated With Cognition in Children With Medulloblastoma

PURPOSE

Emerging evidence suggests proton radiation therapy may offer cognitive sparing advantages over photon radiation therapy, yet dosimetry has not been compared previously. The purpose of this study was to examine dosimetric correlates of cognitive outcomes in children with medulloblastoma treated with proton versus photon radiation therapy.

METHODS AND MATERIALS

In this retrospective, bi-institutional study, dosimetric and cognitive data from 75 patients (39 photon and 36 proton) were analyzed. Doses to brain structures were compared between treatment modalities. Linear mixed-effects models were used to create models of global IQ and cognitive domain scores.

RESULTS

The mean dose and dose to 40% of the brain (D40) were 2.7 and 4.1 Gy less among proton-treated patients compared with photon-treated patients (P = .03 and .007, respectively). Mean doses to the left and right hippocampi were 11.2 Gy lower among proton-treated patients (P < .001 for both). Mean doses to the left and right temporal lobes were 6.9 and 7.1 Gy lower with proton treatment, respectively (P < .001 for both). Models of cognition found statistically significant associations between higher mean brain dose and reduced verbal comprehension, increased right temporal lobe D40 with reduced perceptual reasoning, and greater left temporal mean dose with reduced working memory. Higher brain D40 was associated with reduced processing speed and global IQ scores.

CONCLUSIONS

Proton therapy reduces doses to normal brain structures compared with photon treatment. This leads to reduced cognitive decline after radiation therapy across multiple intellectual endpoints. Proton therapy should be offered to children receiving radiation for medulloblastoma.

Functional network disorganization and cognitive decline following fractionated whole-brain radiation in mice

Cognitive dysfunction following radiotherapy (RT) is one of the most common complications associated with RT delivered to the brain, but the precise mechanisms behind this dysfunction are not well understood, and to date, there are no preventative measures or effective treatments. To improve patient outcomes, a better understanding of the effects of radiation on the brain's functional systems is required. Functional magnetic resonance imaging (fMRI) has shown promise in this regard, however, compared to neural activity, hemodynamic measures of brain function are slow and indirect. Understanding how RT acutely and chronically affects functional brain organization requires more direct examination of temporally evolving neural dynamics as they relate to cerebral hemodynamics for bridging with human studies. In order to adequately study the underlying mechanisms of RT-induced cognitive dysfunction, the development of clinically mimetic RT protocols in animal models is needed. To address these challenges, we developed a fractionated whole-brain RT protocol (3Gy/day for 10 days) and applied longitudinal wide field optical imaging (WFOI) of neural and hemodynamic brain activity at 1, 2, and 3 months post RT. At each time point, mice were subject to repeated behavioral testing across a variety of sensorimotor and cognitive domains. Disruptions in cortical neuronal and hemodynamic activity observed 1 month post RT were significantly worsened by 3 months. While broad changes were observed in functional brain organization post RT, brain regions most impacted by RT occurred within those overlapping with the mouse default mode network and other association areas similar to prior reports in human subjects. Further, significant cognitive deficits were observed following tests of novel object investigation and responses to auditory and contextual cues after fear conditioning. Our results fill a much-needed gap in understanding the effects of whole-brain RT on systems level brain organization and how RT affects neuronal versus hemodynamic signaling in the cortex. Having established a clinically-relevant injury model, future studies can examine therapeutic interventions designed to reduce neuroinflammation-based injury following RT. Given the overlap of sequelae that occur following RT with and without chemotherapy, these tools can also be easily incorporated to examine chemotherapy-related cognitive impairment.

Robustness and dosimetric verification of hippocampal-sparing craniospinal pencil beam scanning proton plans for pediatric medulloblastoma

Background and Purpose

Hippocampal-sparing (HS) is a method that can potentially reduce late cognitive complications for pediatric medulloblastoma (MB) patients treated with craniospinal proton therapy (PT). The aim of this study was to investigate robustness and dosimetric plan verification of pencil beam scanning HS PT.

Materials and Methods

HS and non-HS PT plans for the whole brain part of craniospinal treatment were created for 15 pediatric MB patients. A robust evaluation of the plans was performed. Plans were recalculated in a water phantom and measured field-by-field using an ion chamber detector at depths corresponding to the central part of hippocampi. All HS and non-HS fields were measured with the standard resolution of the detector and in addition 16 HS fields were measured with high resolution. Measured and planned dose distributions were compared using gamma evaluation.

Results

The median mean hippocampus dose was reduced from 22.9 Gy (RBE) to 8.9 Gy (RBE), while keeping CTV V95% above 95 % for all nominal HS plans. HS plans were relatively robust regarding hippocampus mean dose, however, less robust regarding target coverage and maximum dose compared to non-HS plans. For standard resolution measurements, median pass rates were 99.7 % for HS and 99.5 % for non-HS plans (p < 0.001). For high-resolution measurements, median pass rates were 100 % in the hippocampus region and 98.2 % in the surrounding region.

Conclusions

A substantial reduction of dose in the hippocampus region appeared feasible. Dosimetric accuracy of HS plans was comparable to non-HS plans and agreed well with planned dose distribution in the hippocampus region.

Association of ultraprocessed foods consumption and cognitive function among children aged 4-7 years: a cross-sectional data analysis

Background

Sugar-sweetened beverage (SSB) consumption has shown associations with cognitive function in preschool children, but effects of other ultraprocessed foods consumption are rarely discussed in China. This study aimed to investigate the relationship between ultraprocessed food consumption and cognitive function among preschool children in China.

Methods

A total of 325 children aged 4-7 years were included from Guangxi Zhuang Birth Cohort in Guangxi Zhuang Autonomous Region, China. Face-to-face interviews with parents using the Food Frequency Questionnaire (FFQ) was conducted to investigate the status of seven ultraprocessed foods consumption (i.e., chocolate, biscuits, candy, fast-food, ice cream, SSBs, and sweet bakery products). The mandarin-language version of the Wechsler Preschool and Primary Scale of Intelligence (WPPSI, Fourth Edition) was applied to assess the cognitive function of children. Multiple linear and logistic regression models were used to assess the associations between ultraprocessed food consumption and the full-scale intelligence quotient (FSIQ) and different domains and risk of cognitive deficit, respectively.

Results

We found that frequent consumption of candy (β = -3.34, 95% CI: -5.62∼-1.06; p = 0.004) and sweet bakery products (β = -2.77, 95% CI: -5.58∼0.04; p = 0.054) were significant associated with decreased FSIQ scores in the linear regression models. However, only frequent consumption of candy was statistically significantly associated with an increased risk of cognitive deficit (OR = 2.05, 95% CI: 1.11∼3.79; p = 0.023) in the logistic regression models. For the different domains, we found frequent consumption of candy (β = -3.85, 95% CI: -6.28∼-1.43; p = 0.002) and sweet bakery products (β = -3.48, 95% CI: -6.47∼-0.49; p = 0.023) was also significantly associated with lower Verbal Comprehension Index (VCI). When combining the seven ultraprocessed foods, we found children who frequently consumed more than two kinds of ultraprocessed foods had a significant decrease of VCI scores (β = -2.66; 95% CI: -5.12∼-0.19; p = 0.035) too.

Conclusion

Our results suggested that frequent consumption of individual (candy and sweet bakery products) and multiple ultraprocessed foods may decrease VCI scores and thereby impact cognitive function in children aged 4-7 years.

Neurocognition and mean radiotherapy dose to vulnerable brain structures: new organs at risk?

BACKGROUND

Children with brain tumors are at high risk of neurocognitive decline after radiotherapy (RT). However, there is a lack of studies on how RT doses to organs at risk (OARs) impacts neurocognition. The aim of this study was to examine dose-risk relationships for mean RT dose to different brain structures important for neurocognitive networks. We explored previously established OARs and potentially new OARs.

METHODS

A sample of 44 pediatric brain tumor survivors who had received proton and/or photon RT were included. Correlations between mean RT doses to OARs and IQ were analyzed. Previously established OARs were cochleae, optic chiasm, optic nerve, pituitary gland, hypothalamus, hippocampus and pons. Potential new OARs for RT-induced neurocognitive decline were cerebellum, vermis and thalamus.

RESULTS

Mean RT dose to different OARs correlated with several IQ subtests. Higher mean RT dose to cochleae, optic nerve, cerebellum, vermis and pons was correlated with lower performance on particularly full-scale IQ (FIQ), Perceptual Reasoning (PRI), Working Memory (WMI) and Processing Speed Index (PSI). Higher mean RT dose to hippocampus correlated with lower performance on processing speed and working memory. For those receiving whole brain RT (WBRT), higher mean RT dose to the pituitary gland correlated with lower performance on working memory.

CONCLUSION

A high dose-risk correlation was found between IQ subtests and mean RT dose in established and potential new OARs. Thus, in the lack of validated dose constraints for vulnerable brain structures, a parsimonious approach in RT planning should be considered to preserve neurocognitive networks.

Cognition and Brain System Segregation in Pediatric Brain Tumor Patients Treated with Proton Therapy

Purpose

Pediatric brain tumor patients often experience significant cognitive sequelae. Resting-state functional MRI (rsfMRI) provides a measure of brain network organization, and we hypothesize that pediatric brain tumor patients treated with proton therapy will demonstrate abnormal brain network architecture related to cognitive outcome and radiation dosimetry.

Participants and Methods

Pediatric brain tumor patients treated with proton therapy were enrolled on a prospective study of cognitive assessment using the NIH Toolbox Cognitive Domain. rsfMRI was obtained in participants able to complete unsedated MRI. Brain system segregation (BSS), a measure of brain network architecture, was calculated for the whole brain, the high-level cognition association systems, and the sensory-motor systems.

Results

Twenty-six participants were enrolled in the study for cognitive assessment, and 18 completed rsfMRI. There were baseline cognitive deficits in attention and inhibition and processing speed prior to radiation with worsening performance over time in multiple domains. Average BSS across the whole brain was significantly decreased in participants compared with healthy controls (1.089 and 1.101, respectively; P = 0.001). Average segregation of association systems was significantly lower in participants than in controls (P < 0.001) while there was no difference in the sensory motor networks (P = 0.70). Right hippocampus dose was associated with worse attention and inhibition (P < 0.05) and decreased segregation in the dorsal attention network (P < 0.05).

Conclusion

Higher mean dose to the right hippocampus correlated with worse dorsal attention network segregation and worse attention and inhibition cognitive performance. Patients demonstrated alterations in brain network organization of association systems measured with rsfMRI; however, somatosensory system segregation was no different from healthy children. Further work with preradiation rsfMRI is needed to assess the effects of surgery and presence of a tumor on brain network architecture.

Neurocognitive Performance in Adults Treated With Radiation for a Primary Brain Tumor

PURPOSE

The contributory effects of radiation dose to different brain regions on neurocognitive performance after radiation therapy (RT) for primary brain tumors is not well known.

METHODS AND MATERIALS

In this retrospective cohort study, 30 patients with brain tumors treated with photon RT were identified, and radiation dosimetric parameters across brain regions were calculated. All patients had longitudinal neurocognitive evaluations at baseline and after treatment. Generalized estimating equations were used to model each neurocognitive endpoint over time in a multivariable analysis, while adjusted for multiple comparisons of brain regions.

RESULTS

Median follow-up from RT to last assessment was 4.1 years. Fewer years of formal education and older age at the time of RT were associated with lower scores in language, verbal memory, and working memory, after adjustment for baseline scores in multivariable analyses. Higher radiation dose to specific brain regions was not associated with declines in any of the evaluated cognitive domains. On average, there was no clinically significant decline (magnitude of z score change >1) between first and last neurocognitive evaluation. Across each individual cognitive domain, fewer than 15% of patients were impaired at most recent follow-up.

CONCLUSIONS

In this small study of 30 patients treated with RT for a primary brain tumor, brain region dosimetry was not associated with decline in cognitive performance. Older age at time of RT and fewer years of formal education were associated with declines in cognitive performance, suggesting that effects of nondosimetric factors on cognitive performance should be considered alongside treatment factors and dosimetry in neuro-oncology research.

Photon versus proton whole ventricular radiotherapy for non-germinomatous germ cell tumors: A report from the Children's Oncology Group

PURPOSE

To determine if proton therapy reduces doses to cranial organs at risk (OARs) as compared to photon therapy in children with non-germinomatous germ cell tumors (NGGCT) receiving whole ventricular radiotherapy (WVRT).

METHODS AND MATERIALS

Dosimetric data for patients with NGGCT prospectively enrolled in stratum 1 of the Children's Oncology Group study ACNS1123 who received 30.6 Gy WVRT were compared. Target segmentation was standardized using a contouring atlas. Doses to cranial OARs were compared between proton and photon treatments. Clinically relevant dose-volume parameters that were analyzed included mean dose and dose to 40% of the OAR volume (D40).

RESULTS

Mean and D40 doses to the supratentorial brain, cerebellum, and bilateral temporal, parietal, and frontal lobes were statistically significantly lower amongst proton-treated patients, as compared to photon-treated patients. In a subgroup analysis of patients uniformly treated with a 3-mm planning target volume, patients who received proton therapy continued to have statistically significantly lower doses to brain OARs.

CONCLUSIONS

Children treated with proton therapy for WVRT had lower doses to normal brain structures, when compared to those treated with photon therapy. Proton therapy should be considered for patients receiving WVRT for NGGCT.

An Integrated Analysis of Clinical, Genomic, and Imaging Features Reveals Predictors of Neurocognitive Outcomes in a Longitudinal Cohort of Pediatric Cancer Survivors, Enriched with CNS Tumors (Rad ART Pro)

Background

Neurocognitive deficits in pediatric cancer survivors occur frequently; however, individual outcomes are unpredictable. We investigate clinical, genetic, and imaging predictors of neurocognition in pediatric cancer survivors, with a focus on survivors of central nervous system (CNS) tumors exposed to radiation.

Methods

One hundred eighteen patients with benign or malignant cancers (median diagnosis age: 7; 32% embryonal CNS tumors) were selected from an existing multi-institutional cohort (RadART Pro) if they had: 1) neurocognitive evaluation; 2) available DNA; 3) standard imaging. Utilizing RadART Pro, we collected clinical history, genomic sequencing, CNS imaging, and neurocognitive outcomes. We performed single nucleotide polymorphism (SNP) genotyping for candidate genes associated with neurocognition: COMT, BDNF, KIBRA, APOE, KLOTHO. Longitudinal neurocognitive testing were performed using validated computer-based CogState batteries. The imaging cohort was made of patients with available iron-sensitive (n = 28) and/or T2 FLAIR (n = 41) sequences. Cerebral microbleeds (CMB) were identified using a semi-automated algorithm. Volume of T2 FLAIR white matter lesions (WML) was measured using an automated method based on a convolutional neural network. Summary statistics were performed for patient characteristics, neurocognitive assessments, and imaging. Linear mixed effects and hierarchical models assessed patient characteristics and SNP relationship with neurocognition over time. Nested case-control analysis was performed to compare candidate gene carriers to non-carriers.

Results

CMB presence at baseline correlated with worse performance in 3 of 7 domains, including executive function. Higher baseline WML volumes correlated with worse performance in executive function and verbal learning. No candidate gene reliably predicted neurocognitive outcomes; however, APOE ϵ4 carriers trended toward worse neurocognitive function over time compared to other candidate genes and carried the highest odds of low neurocognitive performance across all domains (odds ratio 2.85, P=0.002). Hydrocephalus and seizures at diagnosis were the clinical characteristics most frequently associated with worse performance in neurocognitive domains (5 of 7 domains). Overall, executive function and verbal learning were the most frequently negatively impacted neurocognitive domains.

Conclusion

Presence of CMB, APOE ϵ4 carrier status, hydrocephalus, and seizures correlate with worse neurocognitive outcomes in pediatric cancer survivors, enriched with CNS tumors exposed to radiation. Ongoing research is underway to verify trends in larger cohorts.

Diffusion tensor imaging indices as biomarkers for cognitive changes following paediatric radiotherapy: a systematic review and meta-analysis

Diffusion tensor imaging (DTI) can detect subtle manifestations of white matter (WM) injury following paediatric radiotherapy, which may be a potential biomarker for cognitive changes. This study aimed to synthesise the relationships between DTI indices and cognitive changes following paediatric radiotherapy through systematic review and meta-analysis. PubMed and Scopus electronic databases were used to identify eligible studies. Quality assessment was performed using the National Institute of Health (NIH) Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies. Information on demographics, DTI changes, and associations to cognitive outcomes were extracted. Meta-analyses were performed on DTI changes in specific anatomical locations. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed in the preparation of this report. Eighteen studies were included (median study size: 21; range 18-146). 17/18 studies showed significant cognitive decline following irradiation. Meta-analyses found significant cognitive changes within patient's group of acute lymphoblastic leukaemia (ALL; standard mean differences [SMD] = -0.075, P = 0.01) and brain tumours (BT; SMD = -1.037, P ≤ 0.001) compared to control/baseline. Both groups also had significantly lower fractional anisotropy (FA) scores in the corpus callosum (ALL: SMD = -0.979, P = 0.002; BT: SMD = -1.025, P < 0.001). Decreased FA was consistently associated with cognitive decline. Correlation on WMFA integrity to cognitive domains was statistically significant (Z = 9.86, P < 0.001) with a large effect size (r = 0.52). White matter tract integrity of the corpus callosum measured with FA has the potential to be a biomarker for radiotherapy-related cognitive decline. Inclusion of DTI in follow-up imaging should be encouraged.

Brain network hubs and cognitive performance of survivors of childhood infratentorial tumors

BACKGROUND

Childhood infratentorial tumor patients frequently suffer from long-term cognitive deficits. As each constituent of their treatment can lead to neurotoxicity, cascade effects can lead to profound reorganization of the underlying brain network, the so-called 'connectome'. However, to date, few studies have assessed the relationship between brain network topology, the functional role of network hubs (i.e. highly connected regions), and neurocognitive outcomes in adult survivors of childhood infratentorial tumors.

METHODS

In this cross-sectional study, childhood infratentorial tumor survivors (n = 21: pilocytic astrocytoma (n = 8), ependymoma (n = 1) and medulloblastoma (n = 12)) and healthy controls (n = 21) were recruited. Using multishell diffusion-weighted MRI, microstructural organization and topology of supratentorial white matter was investigated; using a voxel-based approach, a fixel-based analysis, and a graph theoretical approach. In addition, neurocognitive subscales of the WAIS-IV intelligence test, and their relationship with nodal strength and network efficiency metrics were assessed.

RESULTS

Similar to earlier studies, we observed widespread decreases in fractional anisotropy (FA) in patients compared to controls, based on voxel-based analyses. In addition, the fixel-based analyses dissociated macro- from microstructural changes, which were encountered in in infratentorial versus supratentorial brain areas, respectively. Finally, regional reorganization (i.e. differences in local efficiency) occurred mainly in hubs, which suggests a specific vulnerability of these areas. These hubs were not only mostly affected, but also most strongly correlated with the intelligence subscales.

CONCLUSION

This study suggests that network hubs are functionally important for intellectual outcomes in infratentorial tumor survivors. Furthermore, these regions could be the primary targets of treatment toxicity. Validation of this specific hypothesis in larger samples is required.

Pediatric multicompartmental trigeminal schwannoma: illustrative case

BACKGROUND

Trigeminal schwannoma (TS) is an uncommon and histologically benign intracranial lesion that can involve any segment of the fifth cranial nerve. Given its often impressive size at diagnosis and frequent involvement of critical neurovascular structures of the skull base, it represents a challenging entity to treat. Pediatric TS is particularly rare and presents unique challenges. Similarly, tumors with extension into multiple compartments (e.g., middle cranial fossa, posterior cranial fossa, extracranial spaces) are notoriously difficult to treat surgically. Combined or staged surgical approaches are typically required to address them, with radiosurgical treatment as an adjunct.

OBSERVATIONS

The authors presented the unusual case of a 9-year-old boy with a large, recurrent multicompartmental TS involving Meckel’s cave, the cerebellopontine angle, and the infratemporal fossa. Near-total resection was achieved using a frontotemporal-orbitozygomatic craniotomy with a combined interdural and extradural approach.

LESSONS

The case report adds to the current literature on multicompartmental TSs in children and their management. The authors also provided a simplified classification of TS that can be generalized to other skull base tumors. Given a lack of precedent, the authors intended to add to the discussion regarding surgical management of these rare and challenging skull base lesions.

Retrospective study of late radiation-induced damages after focal radiotherapy for childhood brain tumors

PURPOSE

To study a robust and reproducible procedure to investigate a relation between focal brain radiotherapy (RT) low doses, neurocognitive impairment and late White Matter and Gray Matter alterations, as shown by Diffusion Tensor Imaging (DTI), in children.

METHODS AND MATERIALS

Forty-five patients (23 males and 22 females, median age at RT 6.2 years, median age at evaluations 11.1 years) who had received focal RT for brain tumors were recruited for DTI exams and neurocognitive tests. Patients' brains were parceled in 116 regions of interest (ROIs) using an available segmented atlas. After the development of an ad hoc, home-made, multimodal and highly deformable registration framework, we collected mean RT doses and DTI metrics values for each ROI. The pattern of association between cognitive scores or domains and dose or DTI values was assessed in each ROI through both considering and excluding ROIs with mean doses higher than 75% of the prescription. Subsequently, a preliminary threshold value of dose discriminating patients with and without neurocognitive impairment was selected for the most relevant associations.

RESULTS

The workflow allowed us to identify 10 ROIs where RT dose and DTI metrics were significantly associated with cognitive tests results (p<0.05). In 5/10 ROIs, RT dose and cognitive tests were associated with p<0.01 and preliminary RT threshold dose values, implying a possible cognitive or neuropsychological damage, were calculated. The analysis of domains showed that the most involved one was the "school-related activities".

CONCLUSION

This analysis, despite being conducted on a retrospective cohort of children, shows that the identification of critical brain structures and respective radiation dose thresholds is achievable by combining, with appropriate methodological tools, the large amount of data arising from different sources. This supported the design of a prospective study to gain stronger evidence.