Injuries to inferior vermis and dentate nuclei predict poor neurological and neuropsychological outcome in children with malignant posterior fossa tumors

Predictive Factors for the Occurrence of Perioperative Complications in Pediatric Posterior Fossa Tumors

OBJECTIVE

Central nervous system tumors are the most common solid neoplasm in children, 60%-70% occurring in the posterior fossa. Surgery is the mainstay of treatment but surgery in the pediatric population is associated with a high risk of perioperative complications. We aimed at analyzing the perioperative complications after posterior fossa surgery in a pediatric population and identifying the associated risk factors.

METHODS

Retrospective study of all pediatric patients undergoing surgery for resection of a posterior fossa tumor between 1999 and 2019, at the University Hospital of Lausanne. Data were collected including age, clinical presentation, tumor localization, presence of preoperative hydrocephalus, timing of surgery, surgical approach, surgical team, extent of surgical resection, perisurgical complications, and histopathological diagnosis. Statistical analysis was performed to correlate the data with the risk of complications.

RESULTS

Sixty-seven patients were included. Perisurgical complications were identified in 39 patients (58.2%), of which 14 (35.9%) required corrective interventions. The perioperative mortality rate was zero. In the univariate analysis, surgery performed under emergency conditions, transvermian and telovelar approaches were statistically correlated with an increased rate of complications. Extent of resection, hydrocephalus, and Lansky index at presentation were not predictive of perioperative complications. Midline tumor, tumor volume >25 cm3, and surgery performed by a nonspecialized pediatric onconeurosurgeon were found to be independent risk factors in the multivariate analysis.

CONCLUSIONS

Surgery in the posterior fossa in the pediatric population harbors a high risk of complications. Identifying the variables contributing to these complications is important in order to improve surgical management of these patients.

[Medulloblastoma: The latest major advances]

Medulloblastoma (MB) is a malignant brain tumor that mainly affects children. It is rarely found in adults. Among the four groups of MB defined today according to molecular characteristics, group 3 is the least favorable with an overall survival rate of 50 %. Current treatments, based on surgery, radiotherapy, and chemotherapy, are not sufficiently adapted to the different characteristics of the four MB groups. However, the use of new cellular and animal models has opened new doors to interesting therapeutic avenues. In this review, we detail recent advances in MB research, with a focus on the genes and pathways that drive tumorigenesis, with particular emphasis on the animal models that have been developed to study tumor biology, as well as advances in new targeted therapies.

Investigating lesion location in relation to cerebellar mutism following pediatric tumor resection

Background and Objectives

Approximately 25% of pediatric patients who undergo cerebellar tumor resection develop cerebellar mutism syndrome (CMS). Our group recently showed that damage to the cerebellar outflow pathway is associated with increased risk of CMS. Here, we tested whether these findings replicate in an independent cohort.

Methods

We evaluated the relationship between lesion location and the development of CMS in an observational study of 56 pediatric patients who underwent cerebellar tumor resection. We hypothesized that individuals that developed CMS after surgery (CMS+), relative to those that did not (CMS-) would have lesions that preferentially intersected with: 1) the cerebellar outflow pathway, and 2) a previously generated 'lesion-symptom map' of CMS. Analyses were conducted in accordance with pre-registered hypotheses and analytic methods (https://osf.io/r8yjv/).

Results

We found supporting evidence for both hypotheses. Compared with CMS- patients, CMS+ patients (n=10) had lesions with greater overlap with the cerebellar outflow pathway (Cohen's d=.73, p=.05), and the CMS lesion-symptom map (Cohen's d=1.1, p=.004).

Discussion

These results strengthen the association of lesion location with risk of developing CMS and demonstrate generalizability across cohorts. These findings may help to inform the optimal surgical approach to pediatric cerebellar tumors.

Medulloblastomas in Pediatric and Adults

Medulloblastoma is the primary malignant embryonic tumor of the cerebellum and the most common malignant tumor of childhood, accounting up to 25% of all CNS tumors in children, but is extremely rare in adults. Despite the fact that medulloblastomas are one of the most malignant human tumors, it is worthy to note that a great breakthrough has been achieved in our understanding of oncogenesis and the development of real methods of treatment. The main objective of surgical treatment is a maximum resection of tumor with minimal impairment of neurological functions, in order to reduce the volume, remove tumor tissue, get the biopsy, and restore the cerebrospinal fluid flow. The progress of surgical techniques (using a microscope, ultrasound suction), anesthesiology, and intensive care has significantly decreased surgical mortality and increased radicality of tumor removal. Postoperative mortality is less than one percent in most studies, while neurological complications have been reported between 5-10%. Radiotherapy is the main method of treatment in patients older than 3 years, which dramatically improved the recurrence-free survival. Nevertheless, the radiation therapy without systemic chemotherapy leads to a high risk of systemic metastases. After the role of chemotherapy was statistically proven, investigations of the optimal combination of different chemotherapy regimens continued around the world. Currently, 80% of patients can already be cured, however, the quality of life of patients in the long-term period remains quite low, which depends on many factors including endocrinological, cognitive, neurological, and otoneurologic aspects. Thus, the main strategic goal of the development of neuro-oncology is to reduce the doses of radiation therapy to the CNS and the main task of international research is to optimize existing protocols and develop fundamentally new ones based on molecular genetic research in order to improve the quality of life.

Diffusion Tensor Imaging Technique Delineating the Prognosis for Cerebellar Mutism in Posterior Fossa Tumors: A New Tool

AIM

Cerebellar mutism syndrome (CMS) is a morbid complication of posterior fossa surgery in children. This review focuses on the current understanding of pathophysiology in the white matter tracts (WMT) using diffusion tensor imaging (DTI).

MATERIAL AND METHODS

A series of 38 patients operated on for posterior fossa tumors in our institute between December 2019 till May 2021 were evaluated neurologically along with characteristics of mutism and DTI imaging (fractional anisotropy) in preoperative and postoperative periods. We also noted tumor size, location, volume, brainstem compression, cerebellar peduncle involvement, extent of resection, surgical approach, and histopathology.

RESULT

Cerebellar mutism developed in five patients. The mean age, male sex, tumor size >5 cm, superior cerebellar peduncle involvement, and vermian incision were found to have positive correlation with the development of CMS. They showed reduction in fractional anisotropy in superior cerebellar peduncle (SCP) following resection; however, others' WMT did not show any significant change in fractional anisotropy values pre- or post-surgery.

CONCLUSION

Our study suggests that functional disruption of WMT, i.e., superior cerebellar peduncle and dentato-thalamo-cortical tract (DTC) is the underlying pathophysiological component of CMS. Taking this into consideration, we need to deploy techniques to limit the damage to the superior cerebellar peduncle and DTC using neurophysiological monitoring.

The Entity of Cerebellar Mutism Syndrome: A Narrative Review Centered on the Etiology, Diagnostics, Prevention, and Therapeutic Options

Cerebellar mutism syndrome (CMS), also known as posterior fossa syndrome, is an entity that entails a constellation of signs and symptoms which are recorded in a limited number of pediatric patients who have been operated on mainly for tumors involving the posterior cranial fossa, and more precisely, the region of the vermis. Medulloblastoma seems to constitute the most commonly recognized pathological substrate, associated with this entity. The most prevalent constituents of this syndrome are noted to be a, often transient, although protracted, language impairment, emotional lability, along with cerebellar and brainstem dysfunction. Apart from that, a definite proportion of involved individuals are affected by irreversible neurological defects and long-lasting neurocognitive impairment. A bulk of literature and evidence based on clinical trials exist, which reflect the continuous effort of the scientific community to highlight all perspectives of this complex phenomenon. There are several circumstances that intervene in our effort to delineate the divergent parameters that constitute the spectrum of this syndrome. In summary, this is implicated by the fact that inconsistent nomenclature, poorly defined diagnostic criteria, and uncertainty regarding risk factors and etiology are all constituents of a non-well-investigated syndrome. Currently, a preliminary consensus exists about the identification of a group of diagnostic prerequisites that are managed as sine qua non, in our aim to document the diagnosis of CMS. These include language impairment and emotional lability, as proposed by the international Board of the Posterior Fossa Society in their consensus statement. It is common concept that midline tumor location, diagnosis of medulloblastoma, younger age at diagnosis, and preoperatively established language impairment should be accepted as the most determinant predisposing conditions for the establishment of this syndrome. A well-recognized pathophysiological explanation of CMS includes disruption of the cerebellar outflow tracts, the cerebellar nuclei, and their efferent projections through the superior cerebellar peduncle. Despite the relative advancement that is recorded regarding the diagnostic section of this disease, no corresponding encouraging results are reported, regarding the available treatment options. On the contrary, it is mainly targeted toward the symptomatic relief of the affected individuals. The basic tenet of our review is centered on the presentation of a report that is dedicated to the definition of CMS etiology, diagnosis, risk factors, clinical presentation, and clinical management. Apart from that, an effort is made that attempts to elucidate the paramount priorities of the scientific forum, which are directed toward the expansion our knowledge in the era of diagnostics, prevention, and therapeutic options for patients suffering from CM, or who are at risk for development of this syndrome.

Cognitive performance of medulloblastoma tumour survivors related to the area of cerebellum damage

Background

The aim of the study was to determine the relationship between a damaged cerebellum area and the cognitive performance of medulloblastoma tumour survivors. Also, age-based differences in cognitive performance were tested.

Materials and methods

Magnetic resonance imaging (MRI) technique was used to obtain brain images of survivors. The cognitive performance was tested using Wechsler Intelligence Scale for Children Revised (WISC-R) and Wechsler Adult Intelligence Scale (WAIS). Statistical analysis was performed with highly robust permutation tests.

Results

There were two anatomical features strongly influencing the cognitive performance of survivors. The extension of the foramen of Luschka had a negative impact on the overall verbal IQ score and some non-verbal scales while the excision of the middle part of the vermis influenced scores in such scales as arithmetic and picture completing.

Conclusions

Children with postoperative damages in the area of the middle part of the vermis are more likely to suffer from cognitive dysfunctions after the end of the treatment.

Postoperative MRI features of cerebellar mutism syndrome: a retrospective cohort study

OBJECTIVE

In this study, the authors aimed to investigate the relationship between postoperative MRI features and cerebellar mutism syndrome.

METHODS

A retrospective cohort of patients who underwent tumor resection from July 2013 to March 2021 for midline posterior fossa tumors was investigated. All patients were followed up at least once. Clinical data were extracted from medical records and follow-up databases. Two neuroradiologists independently reviewed preoperative and postoperative MRI. Univariable and multivariable analyses were performed to compare the postoperative cerebellar mutism syndrome (pCMS) and non-pCMS groups. Correlation analysis was performed using the Spearman correlation coefficient analysis.

RESULTS

Of 124 patients, 47 (37.9%) developed pCMS. The median follow-up duration was 45.73 (Q1: 33.4, Q3: 64.0) months. The median duration of mutism was 45 days. The median tumor size was 48.8 (Q1: 42.1, Q3: 56.8) mm. In the univariable analysis, abnormal T2-weighted signal of the left dentate nucleus (DN) (74.5% in the pCMS group vs 36.4% in the non-pCMS group, p < 0.001), right DN (83.0% vs 40.3%, p < 0.001), left superior cerebellar peduncle (SCP) (74.5% vs 27.3%, p < 0.001), right SCP (63.8% vs 23.4%, p < 0.001), left middle cerebellar peduncle (MCP) (51.1% vs 26.0%, p = 0.008), and right MCP (61.7% vs 26.0%, p < 0.001); male sex (83.0% vs 45.5%, p < 0.001); vermis 3 impairment (49.4% vs 19.1%, p = 0.002); solid tumor (91.5% vs 72.7%, p = 0.022); and hydrocephalus (72.3% vs 45.5%, p = 0.006) were more frequent in the pCMS group than in the non-pCMS group. Multivariable logistic analysis showed that male sex (adjusted OR 4.08, p = 0.010) and the cerebro-cerebellar circuit score of T2-weighted images (adjusted OR 2.15, p < 0.001) were independent risk factors for pCMS. The cerebro-cerebellar circuit score positively correlated with the duration of mutism. In Cox regression analysis, the cerebro-cerebellar integrated circuit injury score of T2 (adjusted HR 0.790, 95% CI 0.637-0.980; p = 0.032) and injury of vermis 3 (adjusted HR 3.005, 95% CI 1.197-7.547; p = 0.019) were independently associated with the duration of mutism.

CONCLUSIONS

Male sex and cerebro-cerebellar circuit damage are independent risk factors for pCMS. The cerebro-cerebellar circuit score indicates the duration of mutism.

Cerebellar Mutism Syndrome in Pediatric Neuro-oncology: A Multidisciplinary Perspective and Call for Research Priorities

Cerebellar mutism syndrome (CMS), also known as posterior fossa syndrome, occurs in a subset of children after posterior fossa tumor resection, most commonly medulloblastoma. Patients with this syndrome exhibit often transient, although protracted, symptoms of language impairment, emotional lability, cerebellar, and brainstem dysfunction. However, many patients experience persistent neurological deficits and lasting neurocognitive impairment. Historically, research and clinical care were hindered by inconsistent nomenclature, poorly defined diagnostic criteria, and uncertainty surrounding risk factors and etiology. Proposed diagnostic criteria include two major symptoms, language impairment and emotional lability, as proposed by the international Board of the Posterior Fossa Society in their consensus statement as well as other experts in this field. Risk factors most commonly associated with development of CMS include midline tumor location, diagnosis of medulloblastoma and specific tumor subtype, younger age at diagnosis, and preoperative language impairment. A proposed etiology of CMS includes disruption of the cerebellar outflow tracts, the cerebellar nuclei, and their efferent projections through the superior cerebellar peduncle. Treatment for CMS remains supportive. Herein, we present a comprehensive overview of CMS etiology, diagnosis, risk factors, clinical presentation, and clinical management. In addition, we identify essential multidisciplinary research priorities to advance diagnostics, prevention, and intervention efforts for patients with, or at risk for, development of CMS.

Cerebellar mutism syndrome in pediatric head trauma with cerebellar injury

PURPOSE

Cerebellar mutism syndrome (CMS) after cerebellar injury in pediatric head trauma is a poorly recognized condition that is not properly diagnosed or treated in our daily practice. We aimed to clinically identify this syndrome after isolated posttraumatic cerebellar injury and to propose pathophysiological explanation.

METHODS

We retrospectively analyzed 8 consecutive children presenting with isolated cerebellar injury over 16 years. Clinical presentation, radiological type and localization of injury, clinical initial CMS symptoms, and long-term neurocognitive outcome were reviewed.

RESULTS

Out of 8 patients presenting with isolated traumatic cerebellar injury, we diagnosed 2 cases with initial clinical symptoms of CMS. Both patients had an injury damaging median structures of the posterior fossa, especially the fourth ventricle and dentate nuclei. Initial symptoms lasted more than 1 month for one patient, who still presented concentration difficulties almost 1 year after the head injury.

CONCLUSION

CMS after traumatic cerebellar injury does exist, even if it seems to be a very rare entity. It has to be better detected and studied in order to enrich pathophysiological knowledge about CMS of all etiologies and to bring our concerned patients the suitable follow-up and rehabilitative care that they could benefit from.

A CBF decrease in the left supplementary motor areas: New insight into postoperative pediatric cerebellar mutism syndrome using arterial spin labeling perfusion MRI

Postoperative pediatric cerebellar mutism syndrome (pCMS), characterized mainly by delayed onset transient mutism is a poorly understood complication that may occur after pediatric medulloblastoma (MB) resection. Our aim was to investigate postoperative changes in whole-brain cerebral blood flow (CBF) at rest in pCMS patients using arterial spin labeling (ASL) perfusion imaging. This study compared preoperative and postoperative T2-weighted signal abnormalities and CBF using a voxel-wise, whole-brain analysis in 27 children undergoing MB resection, including 11 patients who developed mutism and 16 who did not. Comparison of postoperative T2 signal abnormalities between patients who developed pCMS (mean age 7.0 years) and those who did not showed that pCMS (mean age 8.9 years) patients were significantly more likely to present with T2-weighted hyperintensities in the right dentate nucleus (DN) (p = 0.02). Comparison of preoperative and postoperative CBF in patients with pCMS showed a significant postoperative CBF decrease in the left pre-supplementary motor area (pre-SMA) (p = 0.007) and SMA (p = 0.009). In patients who did not develop pCMS, no significant differences were observed. Findings provide evidence of an association between pCMS, injury to the right DN, and left pre-SMA/SMA hypoperfusion, areas responsible for speech. This supports the relevance of CBF investigations in pCMS.

Cerebellar Volumes Associate with Behavioral Phenotypes in Prader-Willi Syndrome

The objective of this study was to investigate lobule-specific cerebellar structural alterations relevant to clinical behavioral characteristics of Prader-Willi syndrome (PWS). We performed a case-control study of 21 Japanese individuals with PWS (age; median 21.0, range 13–50 years, 14 males, 7 females) and 40 age- and sex-matched healthy controls with typical development. Participants underwent 3-Tesla magnetic resonance imaging. Three-dimensional T₁-weighted images were assessed for cerebellar lobular volume and adjusted for total intracerebellar volume (TIV) using a spatially unbiased atlas template to give a relative volume ratio. A region of interest analysis included the deep cerebellar nuclei. A correlation analysis was performed between the volumetric data and the clinical behavioral scores derived from the standard questionnaires (hyperphagia, autism, obsession, and maladaptive index) for global intelligence assessment in paired subgroups. In individuals with PWS, TIV was significantly reduced compared with that of controls (p < 0.05, family-wise error corrected; mean [standard deviation], 1014.1 [93.0] mm³). Decreased relative lobular volume ratios were observed in posterior inferior lobules with age, sex, and TIV as covariates (Crus I, Crus II, lobules VIIb, VIIIa, VIIIb, and IX). However, increased ratios were found in the dentate nuclei bilaterally in individuals with PWS (p < 0.01); the mean (standard deviation) × 10⁻³ was as follows: left, 1.58 (0.26); right, 1.67 (0.30). The altered lobular volume ratios showed negative correlations with hyperphagic and autistic characteristics and positive correlations with obsessive and intellectual characteristics. This study provides the first objective evidence of topographic patterns of volume differences in cerebellar structures consistent with clinical behavioral characteristics in individuals with PWS and strongly suggests a cerebellar contribution to altered functional brain connectivity in PWS.

A multimodal approach to the study of children treated for posterior fossa tumor: A review of the literature and a pilot study

OBJECTIVE

The aims of the present study were: (1) to review the literature on long-lasting cognitive sequelae in children treated for Posterior Fossa Tumor and (2) to investigate anatomic functional relations in a case series of 7 children treated for PFT using magnetic resonance imaging (MRI) post-processing methods.

METHODS

We retrospectively analyzed MRIs of children who underwent complete surgical resection of PFT and performed extensive neuropsychological evaluation. Tumor, ventricular volumes, and VPS insertion site were drawn on T1 volumetric MRI scans and normalized to a pediatric template. Children showed worse performances on tasks tapping executive functions, memory, visuo-motor precision, and expressive language.

RESULTS

Volumes of interest related to these functions showed a maximum overlap on the left vermis and the lateral ventricle enlargement, except for impaired narrative fluency -which was associated with left lateral ventricle enlargement- and narrative memory -which was related to the right vermis and the enlarged fourth ventricle.

CONCLUSION

Results suggest that anatomic functional relations in children treated for PFT are related to a combination of different pathophysiological factors.

Role of neoadjuvant chemotherapy in metastatic medulloblastoma: a comparative study in 92 children

BACKGROUND

Previous pilot studies have shown the feasibility of preoperative chemotherapy in patients with medulloblastoma, but benefits and risks compared with initial surgery have not been assessed.

METHODS

Two therapeutic strategies were retrospectively compared in 92 patients with metastatic medulloblastoma treated at Gustave Roussy between 2002 and 2015: surgery at diagnosis (n = 54, group A) and surgery delayed after carboplatin and etoposide-based neoadjuvant therapy (n = 38, group B). Treatment strategies were similar in both groups.

RESULTS

The rate of complete tumor excision was significantly higher in group B than in group A (93.3% vs 57.4%, P = 0.0013). Postoperative complications, chemotherapy-associated side effects, and local progressions were not increased in group B. Neoadjuvant chemotherapy led to a decrease in the primary tumor size in all patients; meanwhile 4/38 patients experienced a distant progression. The histological review of 19 matched tumor pairs (before and after chemotherapy) showed that proliferation was reduced and histological diagnosis feasible and accurate even after neoadjuvant chemotherapy. The 5-year progression-free and overall survival rates were comparable between groups. Comparison of the longitudinal neuropsychological data showed that intellectual outcome tended to be better in group B (the mean predicted intellectual quotient value was 6 points higher throughout the follow-up).

CONCLUSION

Preoperative chemotherapy is a safe and efficient strategy for metastatic medulloblastoma. It increases the rate of complete tumor excision and may improve the neuropsychological outcome without jeopardizing survival.

KEY POINTS

1. Preoperative chemotherapy increases the rate of complete tumor removal.2. No additional risk (toxic or disease progression) is linked to the delayed surgery.3. Preoperative chemotherapy could have a positive impact on the neuropsychological outcome of patients.

Surgical management of posterior fossa medulloblastoma in children: The Lyon experience

INTRODUCTION

Modern approach for the treatment of posterior fossa medulloblastomas remains a challenge for pediatric neurosurgeons and pediatric oncologists and requires a multidisciplinary approach to optimize survival and clinical results.

MATERIAL AND METHODS

We report the surgical principles of the treatment of posterior fossa medulloblastomas in children and how to avoid technical mistakes especially in very young patients. We also report our experience in a series of 64 patients operated from a medulloblastoma between 2000 and 2018 in Lyon.

RESULTS

All patients had a craniospinal MRI. Eighty-one percent of the patients (n=50) had strictly midline tumor while 19% (n=14) had lateralized one. Eleven percent (n=7) had metastasis at diagnosis on the initial MRI. Forty-one percent (n=29) had an emergency ETV to treat hydrocephaly and the intracranial hypertension. All patient underwent a direct approach and a complete removal was achieved in 78% (n=58) of the cases on the postoperative MRI realized within 48h postsurgery. Histological findings revealed classical medulloblastoma in 73% (n=46), desmoplastic medulloblastoma in 17% (n=11) and anaplastic/large cell medulloblastoma in 10% (n=7). Patients were classified as low risk in 7 cases, standard risk in 30 cases and high risk in 27 cases. Ninety-six percent (n=61) of the patient received radiotherapy. Seventy-six percent (n=48) received pre-irradiation or adjuvant chemotherapy. At last follow-up in December 2018, 65% (n=41) of the patient were in complete remission, 12% (n=8) were in relapse and 27% (n=15) had died from their disease. The overall survival at five , ten and fifteen years for all the series was of 76%, 73% and 65.7% respectively.

CONCLUSIONS

Medulloblastomas remain a chimiosensible and radiosensible disease and the complete surgical removal represents a favorable prognostic factor. The extension of surgery has also to be weighted in consideration of the new biomolecular and genetic knowledge that have to be integrated by surgeons to improve quality of life of patients.

Ataxia and mobility in children following surgical resection of posterior fossa tumour: A longitudinal cohort study

PURPOSE

To report the course of ataxia in children up to 2 years post-operatively, following surgical resection of a posterior fossa tumour (PFT).

METHODS

Thirty-five children, (median age 9 years, range 4-15) having resection of PFT, were assessed using the Scale for the Assessment and Rating of Ataxia (SARA), Brief Ataxia Rating Scale (BARS) and the mobility domain of the Paediatric Evaluation of Disability Index (PEDI-m) at initial post-operative period (baseline), 3 months, 1 year and 2 years post-operatively.

RESULTS

Baseline median scores of the SARA and BARS were 8.5 (range 0-35.5), and 7 (0-25) respectively. Ataxia improved at 3 months (median SARA and BARS reduction 3.5 and 4, respectively). Additional gradual improvements in SARA were recorded at 1 (median reduction 2) and 2 years post-operatively (median reduction 0.5). Median baseline PEDI-m was 54.75 (range 15.2-100) with improvement at 3 months (median increase 36.95) and small improvement at 1 year (median increase 2.5) and 2 years (median increase 5.8). Children with medulloblastoma and midline tumours (median baseline SARA 10 and 11, respectively) demonstrated more severe ataxia than children with low-grade gliomas and unilateral tumours (median baseline SARA 7.5 and 6.5, respectively).

CONCLUSION

The largest improvement in ataxia scores and functional mobility scores is demonstrated within the first 3 months post-operatively, but ongoing gradual improvement is observed at 2 years. Children with medulloblastoma and midline tumour demonstrated higher ataxia scores long term.

Mapping of long-term cognitive and motor deficits in pediatric cerebellar brain tumor survivors into a cerebellar white matter atlas

PURPOSE

Diaschisis of cerebrocerebellar loops contributes to cognitive and motor deficits in pediatric cerebellar brain tumor survivors. We used a cerebellar white matter atlas and hypothesized that lesion symptom mapping may reveal the critical lesions of cerebellar tracts.

METHODS

We examined 31 long-term survivors of pediatric posterior fossa tumors (13 pilocytic astrocytoma, 18 medulloblastoma). Patients underwent neuronal imaging, examination for ataxia, fine motor and cognitive function, planning abilities, and executive function. Individual consolidated cerebellar lesions were drawn manually onto patients' individual MRI and normalized into Montreal Neurologic Institute (MNI) space for further analysis with voxel-based lesion symptom mapping.

RESULTS

Lesion symptom mapping linked deficits of motor function to the superior cerebellar peduncle (SCP), deep cerebellar nuclei (interposed nucleus (IN), fastigial nucleus (FN), ventromedial dentate nucleus (DN)), and inferior vermis (VIIIa, VIIIb, IX, X). Statistical maps of deficits of intelligence and executive function mapped with minor variations to the same cerebellar structures.

CONCLUSION

We identified lesions to the SCP next to deep cerebellar nuclei as critical for limiting both motor and cognitive function in pediatric cerebellar tumor survivors. Future strategies safeguarding motor and cognitive function will have to identify patients preoperatively at risk for damage to these critical structures and adapt multimodal therapeutic options accordingly.

Long-term cognitive deficits in pediatric low-grade glioma (LGG) survivors reflect pretreatment conditions-report from the German LGG studies

Background

Disease and treatment contribute to cognitive late effects following pediatric low-grade glioma (LGG). We analyzed prospectively collected neuropsychological data of German pediatric LGG survivors and focused on the impact of hydrocephalus at diagnosis, neurofibromatosis type 1 (NF1) status, and extent of surgery.

Methods

We used the Neuropsychological Basic Diagnostic screening tool based on the Cattell-Horn-Carroll model for intelligence and the concept of cross-battery assessment at 2 and 5 years from diagnosis for 316 patients from the German pediatric LGG study and LGG registry (7.1 years median age; 45 NF1; cerebral hemispheres 16%, supratentorial midline 39%, infratentorial 45%). Hydrocephalus was classified radiologically in 137 non-NF1 patients with infratentorial tumors (95/137 complete/subtotal resection).

Results

Patients with NF1 versus non-NF1 exhibited inferior verbal short-term memory and visual processing (P < .001-.021). In non-NF1 patients, infratentorial tumor site and complete/subtotal resection were associated with sequelae in visual processing, psychomotor speed, and processing speed (P < .001-.008). Non-NF1 patients without surgical tumor reduction and/or nonsurgical treatment experienced similar deficits. Degree of hydrocephalus at diagnosis had no further impact. Psychomotor and processing speed were impaired comparably following chemo-/radiotherapy (P < .001-.021). Pretreatment factors such as NF1 or tumor site were relevant at multivariate analysis.

Conclusions

All pediatric LGG survivors are at risk to experience long-term cognitive impairments in various domains. Even surgical only management of cerebellar LGG or no treatment at all, that is, biopsy only/radiological diagnosis did not protect cognitive function. Since pattern and extent of deficits are crucial to tailor rehabilitation, neuropsychological and quality of survival assessments should be mandatory in future LGG trials.

The role of cerebellum in the child neuropsychological functioning

This chapter proposes a review of neuropsychologic and behavior findings in pediatric pathologies of the cerebellum, including cerebellar malformations, pediatric ataxias, cerebellar tumors, and other acquired cerebellar injuries during childhood. The chapter also contains reviews of the cerebellar mutism/posterior fossa syndrome, reported cognitive associations with the development of the cerebellum in typically developing children and subjects born preterm, and the role of the cerebellum in neurodevelopmental disorders such as autism spectrum disorders and developmental dyslexia. Cognitive findings in pediatric cerebellar disorders are considered in the context of known cerebellocerebral connections, internal cellular organization of the cerebellum, the idea of a universal cerebellar transform and computational internal models, and the role of the cerebellum in specific cognitive and motor functions, such as working memory, language, timing, or control of eye movements. The chapter closes with a discussion of the strengths and weaknesses of the cognitive affective syndrome as it has been described in children and some conclusions and perspectives.

Neuropsychological functioning in survivors of childhood medulloblastoma/CNS-PNET: The role of secondary medical complications

OBJECTIVE

To investigate the long-term cognitive consequences of malignant pediatric brain tumor and its treatment, and factors explaining variability in cognitive functioning among survivors. Method: A geographical cohort of survivors of pediatric medulloblastoma (MB) and supratentorial primitive neuroectodermal tumor (CNS-PNET), treated between 1974 and 2013, was invited to participate. Of the 63 surviving patients, 50 (79%) consented to participation. The participants were tested with a battery of neuropsychological tests covering a wide age range. Verbal cognition, nonverbal cognition, processing speed, attention, memory, executive functioning, and manual dexterity were assessed. The participants were between 5:5 and 51:11 years of age at time of assessment. Assessments took place on average 19 years after primary tumor resective surgery. Results: One participant had a severe intellectual disability. For the rest, IQ varied from 52 to 125, with a mean score of 88.0 (SD 19.7). Twenty-eight (56%) of the participants had full-scale IQ scores in the age-average range or above. Gender, age at operation, time since operation, the presence of secondary medical complications, and treatment variables explained 46% of the variability in IQ scores, F(4,44) =  9.5, p<.001. The presence of endocrine insufficiency in combination with either epilepsy and/or hydrocephalus was associated with lowered IQ, lowered processing speed, and memory impairments. Conclusion: Patients treated for childhood MB and CNS-PNET have a lifelong risk of medical sequelae, including impaired cognitive functioning. This study adds to the literature by demonstrating the importance of following neuropsychological functioning closely, especially processing speed, learning, and memory, in survivors who have multiple secondary medical complications.

Long-term cognitive outcome in adult survivors of an early childhood posterior fossa brain tumour

Purpose

Posterior fossa brain tumours (PFT) and their treatment in young children are often associated with subsequent cognitive impairment. However, reported follow-up periods rarely exceed 10 years. This study reports very long-term cognitive consequences of surviving an early childhood PFT.

Methods

62 adult survivors of a PFT, ascertained from a national register, diagnosed before 5 years of age, and a sibling control, received a single IQ assessment an average of 32 years (range 18–53) after initial diagnosis, using the Weschler Abbreviated Scale of Intelligence. Regression models were fitted to survivor–sibling pair differences on verbal and performance IQ (VIQ and PIQ) scores to investigate whether increasing time between PFT diagnosis and follow-up IQ assessment contributed to survivor–sibling IQ differences.

Results

At follow-up, survivors had, on average, VIQ 15 points and PIQ 19 points lower than their siblings. There was no significant effect of time since diagnosis on survivor–sibling VIQ difference. Survivors who received radiotherapy showed no significant effect of time since diagnosis on survivor–sibling PIQ difference. Survivors who did not receive radiotherapy demonstrated a trend for it to reduce.

Conclusions

VIQ and PIQ deficits persist in adulthood, suggesting the effect of a fixed injury imposing on cognitive development, rather than an ongoing pathological process.

Implications for cancer survivors

The findings will help parents and others supporting survivors of an early life PFT to identify and plan for possible cognitive outcomes, and highlight the importance of early interventions to optimize cognitive function during the developmental period.

Electronic supplementary material

The online version of this article (10.1007/s10147-020-01725-7) contains supplementary material, which is available to authorized users.

Cerebellar mutism after embolization of vermian arteriovenous malformation

BACKGROUND

Cerebellar mutism is usually associated with posterior fossa tumor surgery.

CASE REPORT

We report a case of a 17-year-old female, presented with headache and tremor after hemorrhage from a vermian arteriovenous malformation. She was successfully treated by embolization; however, on immediate postoperative, she developed persistent mutism. To the best authors' knowledge, this is the first case of cerebellar mutism after endovascular treatment reported in the medical literature.

CONCLUSION

The endovascular approach may have the same potential of complication of conventional surgery; therefore, more study is necessary to clarify the role and limits of this technique to treat cerebellar arteriovenous malformation.

Radiology of post-operative paediatric cerebellar mutism syndrome

BACKGROUND

Post-operative paediatric cerebellar mutism syndrome is a well-recognized complication following posterior fossa tumour resection in children. Over the past few decades, imaging has played an important role in understanding this disorder.

AIM

This review article aims to focus on the disorder from a radiological perspective, summarizing the salient radiological evidence related to the anatomical structures, pathophysiology, and risk factors related to this disorder.

CONCLUSION

Radiological studies have been integral to the improved understanding of this condition. Future large multicentre studies and quantitative analysis techniques will be vital in further refinement of our understanding of this complex condition.

Exercise and Physical Therapy Interventions for Children with Ataxia: A Systematic Review

The effectiveness of exercise and physical therapy for children with ataxia is poorly understood. The aim of this systematic review was to critically evaluate the range, scope and methodological quality of studies investigating the effectiveness of exercise and physical therapy interventions for children with ataxia. The following databases were searched: AMED, CENTRAL, CDSR, CINAHL, ClinicalTrials.gov, EMBASE, Ovid MEDLINE, PEDro and Web of Science. No limits were placed on language, type of study or year of publication. Two reviewers independently determined whether the studies met the inclusion criteria, extracted all relevant outcomes, and conducted methodological quality assessments. A total of 1988 studies were identified, and 124 full texts were screened. Twenty studies were included in the review. A total of 40 children (aged 5-18 years) with ataxia as a primary impairment participated in the included studies. Data were able to be extracted from eleven studies with a total of 21 children (aged 5-18 years), with a range of cerebellar pathology. The studies reported promising results but were of low methodological quality (no RCTs), used small sample sizes and were heterogeneous in terms of interventions, participants and outcomes. No firm conclusions can be made about the effectiveness of exercise and physical therapy for children with ataxia. There is a need for further high-quality child-centred research.

Diffusion Tensor Imaging Connectomics Reveals Preoperative Neural Connectivity Changes in Children with Postsurgical Posterior Fossa Syndrome

BACKGROUND AND PURPOSE

Posterior fossa syndrome (PFS), characterized by loss of language and other neurological impairments within the immediate postoperative period, occurs in approximately 25% of children who undergo surgical resection of posterior fossa tumors. Diffusion tensor imaging connectomics offer promise for elucidation of pathway-level disruption in neural connectivity of patients with this disorder. We aim to determine differences in pre- and postoperative connectomics between children with PFS and children with mild or no language deficit after surgery.

METHODS

Pre- and postoperative diffusion tensor imaging connectomics were applied and compared among patients with PFS, mild deficits, and intact language.

RESULTS

A total of 35 patients were included in the study. Twenty-three patients with preoperative data and 24 patients with postoperative data were included in the analysis. Mean ages: PFS-8.5 years, mild-3.1 years, intact language-9.4 years (P = .02). Diagnoses included medulloblastoma (44.1%), pilocytic astrocytoma (28.6%), ependymoma (8.6%), other (11.4%), and unknown (8.6%). Five (21.7%) patients had PFS, 4 (17.4%) had mild deficits, and 14 (60.9%) had intact language. The assortativity coefficient was significantly higher in patients with PFS when compared to patients with mild deficits (P = .023). In the connectometry analyses, decreased connectivity was found involving the corpus callosum, right corticothalamic pathway, and right corticostriatal pathway in patients with PFS when compared to patients with intact language.

CONCLUSIONS

Our findings revealed significant differences in preoperative neural connectivity involving the corticothalamic and other pathways among children who did, versus who did not, develop PFS postoperatively. Diffusion tensor imaging connectomics offers a unique opportunity to study the effect of the posterior fossa tumors on cerebello-cerebral networks and provide new insights into the mechanism of the structural plasticity/reorganization after surgery.

Subtle Motor Signs and Executive Functioning in Chronic Paediatric Traumatic Brain Injury: Brief Report

Background: Children with traumatic brain injury (TBI) are reported to have persistent deficits in executive functioning and subtle motor functionsAim: This study examined the relationship between subtle motor signs and executive functioning in children with TBIMethods: Eighteen children aged 13-18 years with mild to severe TBI at least one year before study participation and 16 age-matched typically-developing controls were examined using the Revised Physical and Neurological Examination of Subtle Signs (PANESS), a simplified Go/No-go task, portions of the Delis-Kaplan Executive Function System Verbal Fluency and Trail Making tests, and a Wechsler Coding testResults: There were significant associations between PANESS scores and executive functioning measures in children with TBI but not in controls. Conclusion: Results suggest that assessment of subtle motor signs may provide broader information regarding functioning after pediatric TBI.

Posterior Fossa Arachnoid Cyst in a Pediatric Population is Associated with Social Perception and Rest Cerebral Blood Flow Abnormalities

Posterior fossa arachnoid cysts (PFAC) may produce not only neurological symptoms but also other symptoms still poorly understood such as behavioral and learning deficits, awkwardness, and difficulties in social interaction. These subtle social impairments have not been formally described and their underlying brain mechanisms remain unknown. In the present case-control study, we aimed to empirically characterize social impairments in a pediatric population with PFAC using eye tracking. In addition, we investigated putative functional cortical abnormalities in these children using arterial spin labeling magnetic resonance imaging. Overall, 15 patients with PFAC (3f, age = 9.4 ± 4 years) and 43 typically developing volunteer children (16f, age = 9.3 ± 3.6 years) were enrolled in this study. Eye tracking was used to record gaze patterns during visualization of social interaction scenes. Viewing times to faces of characters and non-social background were analyzed. A voxel-wise whole-brain analysis was performed to investigate rest cerebral blood flow (CBF) abnormalities. Significantly reduced viewing time to faces was observed in patients compared with controls (p < 0.01). A ROC curve analysis revealed that 30% of PFAC patients presented viewing time to the face lower than the cutoff, while none of the controls did. The whole-brain analysis revealed a significant decrease in rest CBF in PFAC patients compared with controls bilaterally in the superior temporal gyrus and the temporoparietal junction (TPJ) (p < 0.05 FWE). These results suggest that early life PFAC may have an impact on functional activity of the temporal lobe, which could be associated with social perception deficits.

Pediatric postoperative cerebellar cognitive affective syndrome follows outflow pathway lesions

OBJECTIVE

To evaluate lesion location after pediatric cerebellar tumor resection in relation to the development of severe cognitive and affective disturbances, or cerebellar cognitive affective syndrome (CCAS).

METHODS

The postsurgical lesion location of 195 pediatric patients with cerebellar tumors was mapped onto a template brain. Individuals with CCAS were matched to 2 participants without CCAS by sex, age, and lesion volume. Lesion analyses included both a hypothesis-driven evaluation of the cerebellar outflow pathway (deep nuclei and superior cerebellar peduncles) and data-driven multivariate lesion symptom mapping. Lesion-associated networks were evaluated by comparing connectivity patterns between the lesion location of cases with and those without CCAS with resting-state functional connectivity MRI data from large normative adult and pediatric cohorts.

RESULTS

CCAS was present in 48 of 195 participants (24.6%) and was strongly associated with cerebellar outflow tract lesions (p < 0.0001). Lesion symptom mapping also highlighted the cerebellar outflow pathway, with peak findings in the fastigial nuclei extending into the inferior vermis. Lesion network mapping revealed that the cerebellar region most associated with CCAS was functionally connected to the thalamic mediodorsal nucleus, among other sites, and that higher connectivity between lesion location and the mediodorsal nucleus predicts CCAS occurrence (p < 0.01). A secondary analysis of 27 participants with mutism revealed similar localization of lesions and lesion-associated networks.

CONCLUSION

Lesions of the cerebellar outflow pathway and inferior vermis are associated with major cognitive and affective disturbances after pediatric cerebellar tumor resection, and disrupted communication between the cerebellum and the thalamic mediodorsal nucleus may be important.

The European Society of Paediatric Oncology Ependymoma-II program Core-Plus model: Development and initial implementation of a cognitive test protocol for an international brain tumour trial

It is increasingly accepted that survival alone is an inadequate measure of the success of childhood brain tumour treatments. Consequently, there is growing emphasis on capturing quality of survival. Ependymomas are the third most frequently occurring brain tumours in childhood and present significant clinical challenges. European Society of Paediatric Oncology Ependymoma II is a comprehensive international program aiming to evaluate outcomes under different treatment regimens and improve diagnostic accuracy. Importantly, there has been agreement to lower the age at which children with posterior fossa ependymoma undergo focal irradiation from three years to either eighteen months or one year of age. Hitherto radiotherapy in Europe had been reserved for children over three years due to concerns over adverse cognitive outcomes following irradiation of the developing brain. There is therefore a duty of care to include longitudinal cognitive follow-up and this has been agreed as an essential trial outcome. Discussions between representatives of 18 participating European countries over 10 years have yielded European consensus for an internationally accepted test battery for follow-up of childhood ependymoma survivors. The 'Core-Plus' model incorporates a two-tier approach to assessment by specifying core tests to establish a minimum dataset where resources are limited, whilst maintaining scope for comprehensive assessment where feasible. The challenges leading to the development of the Core-Plus model are presented alongside learning from the initial stages of the trial. We propose that this model could provide a solution for future international trials addressing both childhood brain tumours and other conditions associated with cognitive morbidity.

Neuroimaging of the component white matter connections and structures within the cerebellar-frontal pathway in posterior fossa tumor survivors

Introduction

In posterior fossa tumor survivors, lower white matter integrity (WMI) in the right cerebellar-left frontal pathway has been well documented and appears to be related to proximity to the cerebellum, radiation treatment, as well as time since treatment in both cranial radiation and surgery-only treatment groups. The current study investigated theories of transneural degeneration following cerebellar tumor resection that may underlie or relate to reductions in WMI and regional brain volumes using correlations. We hypothesized a positive relationship between the volume of the right cerebellum and known white matter output pathways, as well as with the volume of structures that receive cerebellar projections along the pathway.

Methods

Adult survivors of childhood brain tumors were recruited (n = 29; age, M = 22 years, SD = 5; 45% female). Age- and gender-matched controls were also included (n = 29). Participants completed 3 T diffusion-weighted and T1 MPRAGE MRI scans. Brain structure volume relative to intracranial vault served as regional volumetric measures. Fractional anisotropy (FA) and radial diffusivity (RD) served as WMI measures. In the survivor group, partial correlations between WMI and regional volume included controlling for disease severity.

Results

In posterior fossa tumor survivors, the volumes of the cerebellum, thalamus, and frontal lobe were correlated with WMI of the thalamic-frontal segment of the cerebellar-frontal pathway (r = 0.41–0.49, p < .05). Cerebellar atrophy was correlated with reduced WMI in the cerebellar-rubral segment (FA, r = −0.32 p > .05; RD, r = 0.53, p < .01). In the no-radiation survivor group, the regional volume of each structure along the pathway was associated with WMI in the cerebellar-rubral segment. In the radiation survivor group, significant correlations were found between the regional brain volume of each structure and the thalamic-frontal segment of the pathway.

Discussion

The results of this multimodal neuroimaging study provide correlational evidence that the mechanism of injury subsequent to brain tumor treatment may be different depending on type of treatment(s). Without radiation, the primary mechanism of injury is cerebellar tumor growth, resection, and hydrocephalus. Therefore, the most proximal connection to that injury (cerebellar-rubral pathway) was correlated with reductions in volume along the pathway. In contrast, the survivor group treated with radiation may have had possible radiation-induced demyelination of the thalamic-frontal portion of the pathway, based on a strong correlation with volume loss in the cerebellum, red nucleus, thalamus, and frontal lobe.

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Cerebellar atrophy predicted lower white matter integrity (WMI) in the cerebellar-rubral segment.

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The no-radiation group showed a correlational pattern that is consistent with possible transneural degeneration.

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The radiation group showed a correlational pattern consistent with theories of neurodevelopmental vulnerability to radiation-induced demyelination.

Intellectual, educational, and situation-based social outcome in adult survivors of childhood medulloblastoma

PURPOSE

To investigate intellectual and situation-based social outcome and educational achievement in adult survivors of childhood medulloblastoma and analyse factors influencing outcome Methods: We collected demographic, medical and cognitive data, and social and educational outcome at a mean time since the end of treatments of 14.9 years in 58 adults, aged 19-35 years, consecutively treated in a single cancer center between 1989 and 2005.

RESULTS

Ten survivors had severe intellectual disability, 12 were still studying, 23 had a regular employment and 13 were unemployed. Full Scale Intellectual Quotient, assessed 6.6 years after the end of treatments, ranged from 46 to 131. It was strongly associated with educational achievement and significantly lower in patients who experienced postoperative cerebellar mutism, and when parental education level was low.

CONCLUSION

These factors should be systematically considered at diagnosis in order to offer adequate and timely assessments and interventions.

Long-Term Supratentorial Radiologic Effects of Surgery and Local Radiation in Children with Infratentorial Ependymoma

BACKGROUND

Current standard of care for children with infratentorial ependymoma includes maximal safe resection and local radiation of 54-59 Gray. High-dose local radiation has been associated with declines in multiple cognitive domains. The anatomic and physiologic correlates of this cognitive decline remain undefined, and there have been no radiographic studies on the long-term effects of this treatment paradigm.

METHODS

A comprehensive database of pediatric brain tumor patients treated at Stanford Children's from 2004-2016 was queried. Seven patients with posterior fossa ependymoma who were treated with surgery and local radiation alone, who had no evidence of recurrent disease, and had imaging suitable for analysis were identified. Diffusion-weighted magnetic resonance imaging datasets were used to calculate apparent diffusion coefficient maps for each subject, while arterial spin labeling datasets were used to calculate maps of cerebral blood flow. Diffusion-weighted imaging and arterial spin labeling datasets of 52 age-matched healthy children were analyzed in the same fashion to enable group comparisons.

RESULTS

Several statistically significant differences were detected between the 2 groups. Cerebral blood flow was lower in the caudate and pallidum and higher in the nucleus accumbens in the ependymoma cohort compared with controls. Apparent diffusion coefficient was increased in the thalamus and trended toward decreased in the amygdala.

CONCLUSIONS

Surgery and local radiation for posterior fossa ependymoma are associated with supratentorial apparent diffusion coefficient and cerebral blood flow alterations, which may represent an anatomic and physiologic correlate to the previously published decline in neurocognitive outcomes in this population.

Microsurgical anatomy of the fourth ventricle

Anatomical description of the fourth ventricle is essential for an accurate understanding of its related tumoral pathologies and surgical approach respecting cerebellar and brainstem structures. Numerous cadaver pictures illustrate this chapter which contains V4 floor and roof description and its vascularization.

Cerebellar mutism syndrome: cause and rehabilitation

PURPOSE OF REVIEW

Mutism of cerebellar origin may occur in the context of various causes but is most frequent in children after resection of a large midline cerebellar tumour. In this review, the endeavour to reach a consensus on name and definition of postoperative mutism of cerebellar origin and associated symptoms is highlighted. In addition, progress in understanding of cause and risk factors for the syndrome is discussed as well as the rehabilitation issues.

RECENT FINDINGS

Consensus on the term cerebellar mutism syndrome (CMS) has been reached. The exact pathogenesis of CMS remains unclear. Recently, attention was drawn to the hypothesis that thermal injury might be an important mechanism in the pathogenesis of CMS. Diffusion tensor imaging tractography was found to visualize the damage to relevant pathways that are associated with persistent impairments after recovery of CMS. There is still no established treatment for CMS to date.

SUMMARY

By reaching a consensus on terminology and description of CMS, a firm basis has been created for future research. The pathogenesis of CMS seems multifactorial and important risk factors have been found. However, CMS cannot be effectively prevented yet and no established or specific treatment is available, apart from very general rehabilitation and cognitive interventions.

Neuropsychological consequences of childhood medulloblastoma and possible interventions: A review

BACKGROUND

Children who have been treated for a medulloblastoma often suffer long-term cognitive impairments that often negatively affect their academic performance and quality of life. In this article, we will review the neuropsychological consequences of childhood medulloblastoma and discuss the risk factors known to influence the presence and severity of these cognitive impairments and possible interventions to improve their quality of life.

METHODS

This narrative review was based on electronic searches of PubMed to identify all relevant studies.

RESULTS

Although many types of cognitive impairments often emerge during a child's subsequent development, the core cognitive domains that are most often affected in children treated for a medulloblastoma are processing speed, attention and working memory. The emergence and magnitude of these deficits varies greatly among patients. They are influenced by demographic (age at diagnosis, parental education), medical and treatment-related factors (perioperative complications, including posterior fossa syndrome, radiation therapy dose, etc.), and the quality of interventions such as school adaptations provided to the child or rehabilitation programs that focus on cognitive skills, behavior and psychosocial functioning.

CONCLUSION

These patients require specialized and coordinated multidisciplinary rehabilitation follow-up that provides timely and adapted assessments and culminates in personalized intervention goals being set with the patient and the family. Follow-up should be continued until referral to adult services.

Cerebellar mutism syndrome in children with brain tumours of the posterior fossa

Background

Central nervous system tumours constitute 25% of all childhood cancers; more than half are located in the posterior fossa and surgery is usually part of therapy. One of the most disabling late effects of posterior fossa tumour surgery is the cerebellar mutism syndrome (CMS) which has been reported in up to 39% of the patients but the exact incidence is uncertain since milder cases may be unrecognized. Recovery is usually incomplete. Reported risk factors are tumour type, midline location and brainstem involvement, but the exact aetiology, surgical and other risk factors, the clinical course and strategies for prevention and treatment are yet to be determined.

Methods

This observational, prospective, multicentre study will include 500 children with posterior fossa tumours. It opened late 2014 with participation from 20 Nordic and Baltic centres. From 2016, five British centres and four Dutch centres will join with a total annual accrual of 130 patients. Three other major European centres are invited to join from 2016/17. Follow-up will run for 12 months after inclusion of the last patient. All patients are treated according to local practice. Clinical data are collected through standardized online registration at pre-determined time points pre- and postoperatively. Neurological status and speech functions are examined pre-operatively and postoperatively at 1–4 weeks, 2 and 12 months. Pre- and postoperative speech samples are recorded and analysed. Imaging will be reviewed centrally. Pathology is classified according to the 2007 WHO system. Germline DNA will be collected from all patients for associations between CMS characteristics and host genome variants including pathway profiles.

Discussion

Through prospective and detailed collection of information on 1) differences in incidence and clinical course of CMS for different patient and tumour characteristics, 2) standardized surgical data and their association with CMS, 3) diversities and results of other therapeutic interventions, and 4) the role of host genome variants, we aim to achieve a better understanding of risk factors for and the clinical course of CMS - with the ultimate goal of defining strategies for prevention and treatment of this severely disabling condition.

Trial registration

Clinicaltrials.gov: NCT02300766, date of registration: November 21, 2014.

Radiation induces progenitor cell death, microglia activation, and blood-brain barrier damage in the juvenile rat cerebellum

Posterior fossa tumors are the most common childhood intracranial tumors, and radiotherapy is one of the most effective treatments. However, irradiation induces long-term adverse effects that can have significant negative impacts on the patient’s quality of life. The purpose of this study was to characterize irradiation-induced cellular and molecular changes in the cerebellum. We found that irradiation-induced cell death occurred mainly in the external germinal layer (EGL) of the juvenile rat cerebellum. The number of proliferating cells in the EGL decreased, and 82.9% of them died within 24 h after irradiation. Furthermore, irradiation induced oxidative stress, microglia accumulation, and inflammation in the cerebellum. Interestingly, blood-brain barrier damage and blood flow reduction was considerably more pronounced in the cerebellum compared to other brain regions. The cerebellar volume decreased by 39% and the migration of proliferating cells to the internal granule layer decreased by 87.5% at 16 weeks after irradiation. In the light of recent studies demonstrating that the cerebellum is important not only for motor functions, but also for cognition, and since treatment of posterior fossa tumors in children typically results in debilitating cognitive deficits, this differential susceptibility of the cerebellum to irradiation should be taken into consideration for future protective strategies.

Time knowledge difficulties following treatment for malignant cerebellar tumors

In children treated for malignant cerebellar tumors, there are only a few studies investigating temporal skills, despite the role of the cerebellum in time processing being generally acknowledged. Children's time knowledge has been defined as the correct representation and use of familiar time units. The present study compares time knowledge in 38 children treated for malignant cerebellar tumors (mean age 11.6 years) with 105 typically-developing (TD) children. The performances on all time knowledge subtests were significantly lower in the tumor group. The results also confirm a lower mean IQ in the children treated for cerebellar tumors, related to slower processing speed and poorer performance on working memory and non-verbal tasks. However, the lower IQ does not explain the considerable difficulties in the acquisition of time knowledge. These results are discussed in the light of the role of the cerebellum in time processing and in the context of two different models of temporal processing: the internal clock model and the neural network state model.

Cerebellar fMRI Activation Increases with Increasing Working Memory Demands

The aim of the present study was to explore cerebellar contributions to the central executive in n-back working memory tasks using 7-T functional magnetic imaging (fMRI). We hypothesized that cerebellar activation increased with increasing working memory demands. Activations of the cerebellar cortex and dentate nuclei were compared between 0-back (serving as a motor control task), 1-back, and 2-back working memory tasks for both verbal and abstract modalities. A block design was used. Data of 27 participants (mean age 26.6 ± 3.8 years, female/male 12:15) were included in group statistical analysis. We observed that cerebellar cortical activations increased with higher central executive demands in n-back tasks independent of task modality. As confirmed by subtraction analyses, additional bilateral activations following higher executive demands were found primarily in four distinct cerebellar areas: (i) the border region of lobule VI and crus I, (ii) inferior parts of the lateral cerebellum (lobules crus II, VIIb, VIII, IX), (iii) posterior parts of the paravermal cerebellar cortex (lobules VI, crus I, crus II), and (iv) the inferior vermis (lobules VI, VIIb, VIII, IX). Dentate activations were observed for both verbal and abstract modalities. Task-related increases were less robust and detected for the verbal n-back tasks only. These results provide further evidence that the cerebellum participates in an amodal bilateral neuronal network representing the central executive during working memory n-back tasks.

Post-operative diffusion weighted imaging as a predictor of posterior fossa syndrome permanence in paediatric medulloblastoma

PURPOSE

Posterior fossa syndrome (PFS) is a serious complication faced by neurosurgeons and their patients, especially in paediatric medulloblastoma patients. The uncertain aetiology of PFS, myriad of cited risk factors and therapeutic challenges make this phenomenon an elusive entity. The primary objective of this study was to identify associative factors related to the development of PFS in medulloblastoma patient post-tumour resection.

METHODS

This is a retrospective study based at a single institution. Patient data and all related information were collected from the hospital records, in accordance to a list of possible risk factors associated with PFS. These included pre-operative tumour volume, hydrocephalus, age, gender, extent of resection, metastasis, ventriculoperitoneal shunt insertion, post-operative meningitis and radiological changes in MRI. Additional variables included molecular and histological subtypes of each patient's medulloblastoma tumour. Statistical analysis was employed to determine evidence of each variable's significance in PFS permanence.

RESULTS

A total of 19 patients with appropriately complete data was identified. Initial univariate analysis did not show any statistical significance. However, multivariate analysis for MRI-specific changes reported bilateral DWI restricted diffusion changes involving both right and left sides of the surgical cavity was of statistical significance for PFS permanence.

CONCLUSION

The authors performed a clinical study that evaluated possible risk factors for permanent PFS in paediatric medulloblastoma patients. Analysis of collated results found that post-operative DWI restriction in bilateral regions within the surgical cavity demonstrated statistical significance as a predictor of PFS permanence-a novel finding in the current literature.

Neuropsychological improvement after posterior fossa arachnoid cyst drainage

PURPOSE

Posterior fossa arachnoid cysts (PFAC) are mostly considered as benign lesions of the cerebellum. Although many studies have shown the major role of the cerebellum in modulating movement, language, cognition, and social interaction, there are few studies on the cognitive impact and surgical decompression of PFAC.

METHODS

We present the cases of two brothers successively diagnosed with PFAC and neuropsychological delay. After multidisciplinary discussion with the boys' parents, it was decided to drain these lesions. Clinical signs, cerebral images, and neuropsychological status were assessed on admission and then 1 and 3 years after surgery.

RESULTS

At presentation, both children had mild cerebellar signs, associated with cognitive and visual-motor impairments and academic regression. CT scans revealed retrovermian cysts, which were shunted. Post-operatively, both brothers demonstrated improved visual-motor skills and behavior. At follow-up, we observed disappearance of dysarthria and academic delay and significant improvement in cognition especially at the intelligence scale and in language. Fine motor skills had improved but remained slower than the average and writing skills appeared limited.

CONCLUSION

Except for PFAC which impair cerebrospinal fluid circulation or which are responsible for a significant mass effect, most PFAC are usually considered as "asymptomatic" and do not require surgical treatment. The two cases reported herein suggest that these lesions might be responsible for some associated but potentially reversible neuropsychological impairment. In the future, clinical assessment should include neuropsychological evaluation to help inform decision for surgical decompression in these children with PFAC.

Synchronous Aberrant Cerebellar and Opercular Development in Fetuses and Neonates with Congenital Heart Disease: Correlation with Early Communicative Neurodevelopmental Outcomes, Initial Experience

Patients with congenital heart disease (CHD) demonstrate multidomain cognitive delays. Cingulo-opercular and cerebellar brain networks are critical to language functions. This is a description of our initial experience aiming to identify an anatomic correlate for CHD patients with expressive language delays. Fetal CHD patients, prospectively enrolled, underwent serial fetal (1.5T), postnatal pre- and postoperative (3T) MRI. Non-CHD patients were enrolled retrospectively from the same epoch. Comparable fetal and neonatal T2 contrast was used for manual linear cross-sectional measurement. Multivariable analysis was used for adjustments and curve fitting. Neurodevelopment was assessed with Battelle Developmental Inventory, 2nd ed. between 9 and 36 months of age. This interim analysis included patients from our longitudinal CHD study who had fetal, postnatal imaging and neurodevelopmental data-yielding a total of 62 mothers (11 CHD fetuses and 51 non-CHD fetuses). Altered brain trajectories were seen in selected cerebellar and opercular measurements in CHD patients compared with the non-CHD group. Smaller inferior cerebellar vermis measurements were associated with multiple communication-related abnormalities. Altered early structural development of the cerebellum and operculum is present in patients with CHD, which correlates with specific neurodevelopmental abnormalities.

Posterior fossa syndrome-a narrative review

Posterior fossa syndrome (PFS), or cerebellar mutism syndrome (CMS), is a collection of neurological symptoms that occur following surgical resection of a posterior fossa tumour, and is characterised by either a reduction or an absence of speech. Some authors suggest that CM is only one symptom of the CMS complex that also includes ataxia, hypotonia and irritability as well as cranial nerve deficits, neurobehavioral changes and urinary retention or incontinence. It is seen almost exclusively in children. In 1985 Rekate et al. published the first work describing CM as a clinical entity, occurring as a consequence of bilateral cerebellar injury. Other associated symptoms include visual impairment, altered mood, impaired swallowing and significant gross and fine motor deficits. The effects of this can have a devastating impact on both the patient and their carers, posing a significant clinical challenge to neurorehabilitation services. The reported incidence was between 8% and 31% of children undergoing surgery for posterior fossa tumour. The underlying pathologies include vasospasm, oedema, and axonal/neuronal injury. Neuroimaging has contributed to a better understanding of the anatomical location of postoperative injury. There have been a number of suggestions for treatment interventions for PFS. However, apart from some individual reports, there have been no clinical trials indicating possible benefit. Occupational therapy, speech and language therapy, as well as neurocognitive support, contribute to the recovery of these patients.

Post-operative pediatric cerebellar mutism syndrome and its association with hypertrophic olivary degeneration

BACKGROUND

The dentato-thalamo-cortical (DTC) pathway is recognized as the anatomical substrate for postoperative pediatric cerebellar mutism (POPCMS), a well-recognized complication affecting up to 31% of children undergoing posterior fossa brain tumour resection. The proximal structures of the DTC pathway also form a segment of the Guillain and Mollaret triangle, a neural network which when disrupted causes hypertrophic olivary degeneration (HOD) of the inferior olivary nucleus (ION). We hypothesize that there is an association between the occurrence of POPCMS and HOD and aim to evaluate this on MR imaging using qualitative and quantitative analysis of the ION in children with and without POPCMS.

METHODS

In this retrospective study we qualitatively analysed the follow up MR imaging in 48 children who underwent posterior fossa tumour resection for presence of HOD. Quantitative analysis of the ION was possible in 28 children and was performed using semi-automated segmentation followed by feature extraction and feature selection techniques and relevance of the features to POPCMS were evaluated. The diagnosis of POPCMS was made independently based on clinical and nursing assessment notes.

RESULTS

There was significant association between POPCMS and bilateral HOD (P=0.002) but not unilateral HOD. Quantitative analysis showed that hyperintensity in the left ION was the most relevant feature in children with POPCMS.

CONCLUSIONS

Bilateral HOD can serve as a reliable radiological indicator in establishing the diagnosis of POPCMS particularly in equivocal cases. The strong association of signal change due to HOD in the left ION suggests that injury to the right proximal efferent cerebellar pathway plays an important role in the causation of POPCMS.

Core deficits and quality of survival after childhood medulloblastoma: a review

Background

Medulloblastoma is the most common malignant central nervous system tumor in children. Treatment most often includes surgical resection, craniospinal irradiation, and adjuvant chemotherapy. Although survival has improved dramatically, the tumor and its treatments have devastating long-term side effects that negatively impact quality of survival (QoS). The objective was to review the literature on QoS following childhood medulloblastoma.

Methods

This narrative review is based on a Medline database search and examination of the reference lists of papers selected.

Results

Frequent problems after medulloblastoma treatment include medical complications, such as long-term neurological and sensory (hearing loss) impairments; endocrine deficits, including growth problems; and secondary tumors. Neurocognitive impairment is repeatedly reported, with decreasing cognitive performances over time. Although all cognitive domains may be affected, low processing speed, attention difficulties, and working memory difficulties are described as the core cognitive deficits resulting from both cerebellar damage and the negative effect of radiation on white matter development. Long-term psychosocial limitations include low academic achievement, unemployment, and poor community integration with social isolation. Important negative prognostic factors include young age at diagnosis, conventional craniospinal radiotherapy, presence of postoperative cerebellar mutism, and perioperative complications. The influence of environmental factors, such as family background and interventions, remains understudied.

Conclusion

Future studies should focus on the respective impact of radiation, cerebellar damage, genomic and molecular subgroup parameters, and environmental factors on cognitive and psychosocial outcomes. Long-term (probably lifelong) follow-up into adulthood is required in order to monitor development and implement timely, suitable, multi-disciplinary rehabilitation interventions and special education or support when necessary.