Cerebellocerebral diaschisis is the likely mechanism of postsurgical posterior fossa syndrome in pediatric patients with midline cerebellar tumors

Apathy in Alzheimer's disease: Eye movements characteristics and neurostructural basis

BACKGROUND

We sought to evaluate the characteristics of eye movements in Alzheimer's disease (AD) patients with apathy (AD-A) and their ability to identify AD-A and explore the shared neurostructure of eye movements and apathy.

METHODS

Total 32 normal controls, 36 AD-A, and 72 AD with no apathy (AD-NA) patients were recruited. Parameters of smooth pursuit, fixation, prosaccade, and antisaccade were compared among the three groups. Correlation analyses were conducted among apathy score, eye movement parameters, and gray matter volume (GMV) in AD patients. Receiver operating characteristic curves were used to determine the power of eye movement parameters to identify AD-A group.

RESULTS

AD-A group exhibited a longer start-up duration of smooth pursuit, latencies of gap and overlap prosaccades than AD-NA and normal control groups. In AD patients, apathy score was positively correlated with the latency of overlap prosaccade. The GMV of right pregenual anterior cingulate cortex (ACC) and left supracallosal ACC were negatively correlated with apathy score. Regions shared by apathy and the latency of overlap prosaccade included right pregenual ACC and left supracallosal ACC. The area under curve discriminated AD-A from AD-NA gropu by combining start-up duration, latencies of gap and overlap prosaccade, and demographic information was 0.812.

CONCLUSIONS

AD-A patients exhibit delayed initiation in eye movements, and the more prominent apathy indicates prolonged latency of overlap prosaccade in AD patients. Apathy and the latency of overlap prosaccade share a neurostructural basis in AD patients. Our results contribute to providing a new method for early identification and severity assessment for AD-A.

Tumour volume as a predictor of postoperative speech impairment in children undergoing resection of posterior fossa tumours: a prospective, multicentre study

BACKGROUND

Cerebellar Mutism Syndrome (CMS) is a neurological complication of posterior fossa (PF) tumour surgery in children, and postoperative speech impairment (POSI) is the cardinal symptom of CMS. The role of tumour volume on the risk of POSI remains unexplored. This study investigates the association between tumour volume and the risk of POSI.

METHODS

We included 360 patients from the European CMS study with available preoperative T1-weighted contrast-enhanced brain MRI. Speech status was assessed within two weeks postoperatively and categorised into three levels: habitual speech, severely reduced speech, and mutism. Tumour volumes were calculated using the BrainLab Elements SmartBrush™, a semi-automated segmentation tool. We used proportional odds models to estimate the odds ratio (OR) with adjustments for tumour location, pathology, and age. Based on the primary analysis, a risk stratification model for medulloblastoma patients was constructed, and the optimal volume cut-off was determined with Youden's Index.

RESULTS

We found no effect of the overall tumour volume on the risk of POSI. This result did not change when adjusted for tumour location, pathology, and age. We found an association between tumour volume of medulloblastoma and the risk of POSI (unadjusted OR of 1.04 per increase in cm3 (95% CI 1.01;1.07, p = 0.01)), which did not change when adjusting for tumour location and age. The risk stratification cut-off for the tumour volume of medulloblastoma was calculated to be 16,5 cm3. Patients with medulloblastoma and preoperative tumour volumes below 16,5 cm3 had an absolute risk of 13% for POSI (low-risk group), whereas patients with preoperative tumour volumes above 16,5 cm3 had an absolute risk of 50% for POSI (high-risk group).

CONCLUSION

Our data showed an association between preoperative tumour volume and the risk of POSI in children with medulloblastoma, while no association was found for the volume of other tumour types. We suggest a straightforward cut-off risk model for assessing the risk of POSI in children with medulloblastoma based on preoperative tumour volume. This approach can aid clinicians in informing patients and parents about the complications related to CMS following PF tumour surgery in children.

CLINICAL TRIALS

ID NCT02300766 (October 2014).

Radiological Predictors of Cognitive Impairment in Paediatric Brain Tumours Using Multiparametric Magnetic Resonance Imaging: A Review of Current Practice, Challenges and Future Directions

Paediatric brain tumours and their treatments are associated with long-term cognitive impairment. While the aetiology of cognitive impairment is complex and multifactorial, multiparametric Magnetic Resonance Imaging (MRI) can identify many risk factors including tumour location, damage to eloquent structures and tumour phenotype. Hydrocephalus and raised intracranial pressure can be observed, along with risk factors for post-operative paediatric cerebellar mutism syndrome or epilepsy. MRI can also identify complications of surgery or radiotherapy and monitor treatment response. Advanced imaging sequences provide valuable information about tumour and brain physiology, but clinical use is limited by extended scanning times and difficulties in processing and analysis. Brain eloquence classifications exist, but focus on adults with neurological deficits and are outdated. For the analysis of childhood tumours, limited numbers within tumour subgroups and the investigation of long-term outcomes necessitate using historical scans and/or multi-site collaboration. Variable imaging quality and differing acquisition parameters limit the use of segmentation algorithms and radiomic analysis. Harmonisation can standardise imaging in collaborative research, but can be challenging, while data-sharing produces further logistical challenges. Consequently, most research consists of small single-centre studies limited to regional analyses of tumour location. Technological advances reducing scanning times increase the feasibility of clinical acquisition of high-resolution standardised imaging including advanced physiological sequences. The RAPNO and SIOPE paediatric brain tumour imaging guidelines have improved image standardisation, which will benefit future collaborative imaging research. Modern machine learning techniques provide more nuanced approaches for integration and analysis of the complex and multifactorial data involved in cognitive outcome prediction.

Medical management of cerebellar mutism syndrome at a quaternary children's hospital

PURPOSE

We aimed to evaluate the efficacy of selective serotonin reuptake inhibitors (SSRIs) in treating cerebellar mutism syndrome (CMS).

METHODS

We retrospectively reviewed all pediatric patients who underwent a posterior fossa tumor resection between May 2007 to September 2022 at a single quaternary pediatric hospital. We evaluated clinical presentation and hospital course, including imaging findings, pathology, and surgical approaches. Propensity score matching was used to compare the symptom duration of patients who received SSRIs versus those who did not.

RESULTS

A total of 292 patients met the criteria with 25% (n = 73) being diagnosed with CMS. Several factors were significantly associated with a CMS diagnosis, such as pre-operative hydrocephalus (p = 0.002), a vermis-splitting approach (p = 0.007), tumor in the fourth ventricle (p = 0.010), medulloblastoma diagnosis (p = 0.009), and postoperative complication (p < 0.001). Of the patients diagnosed with CMS, 32.9% (n = 24) received SSRI treatment, specifically fluoxetine (n = 18) and sertraline (n = 6). Overall, treatment did not decrease the duration of CMS symptoms or shorten the inpatient rehab course compared to matched controls. However, within the cohort of fluoxetine-treated patients, earlier initiation of medication was significantly correlated with a shorter duration of mutism (p = 0.007).

CONCLUSIONS

We report the largest cohort of CMS patients treated with SSRIs. The lack of overall clinical benefit when compared to untreated patients in our study may be due to the length of delay in starting an SSRI, since early initiation of fluoxetine correlated with shorter CMS symptoms. These results support the importance of early clinical detection of CMS and potentially treating CMS early in the patient's postoperative course.

Neuroimaging of postoperative pediatric cerebellar mutism syndrome: a systematic review

Background

Postoperative pediatric cerebellar mutism syndrome (ppCMS) poses serious morbidity after posterior fossa tumor surgery. Neuroimaging studies aim to understand its pathophysiology, yet these vary in methodology and outcome measures. Therefore, we systematically reviewed the current literature to evaluate the evidence for differences in neuroimaging features between children with and without ppCMS.

Methods

Following PRISMA guidelines, a systematic review was conducted by searching for original articles on neuroimaging in children undergoing posterior fossa tumor surgery, comparing patients with and without ppCMS. Articles were selected based on predefined eligibility criteria. Data were systematically extracted, and risk of bias was evaluated.

Results

From the 866 articles identified, 50 studies fulfilled the inclusion criteria. Studies were categorized into 3 imaging domains: structural, diffusion, and functional imaging. Risk of bias assessment revealed a medium risk in most articles, predominantly due to unclear ppCMS definition and qualitative image analysis without blinding for ppCMS diagnosis. Preoperative structural imaging showed the association of ppCMS with midline tumor localization and involvement of the brainstem, superior cerebellar peduncle (SCP), or middle cerebellar peduncle. Postoperative structural and diffusion imaging highlighted SCP injury with reduced white matter integrity, while functional imaging demonstrated hypoperfusion in frontal lobes. Late follow-up showed T2-weighted hyperintensities in the inferior olivary nuclei of ppCMS patients.

Conclusion

Neuroimaging features suggest that ppCMS is associated with efferent cerebellar pathway injury and hypoperfusion in frontal lobes, with level 2 a/b evidence. Large-scale prospective longitudinal neuroimaging studies comparing pre- and postoperative imaging are needed to further elucidate the pathophysiological mechanism of ppCMS.

Secondary cerebro-cerebellar and intra-cerebellar dysfunction in cerebellar mutism syndrome

BACKGROUND

Cerebellar mutism syndrome (CMS) is characterized by deficits of speech, movement, and affect that can occur following tumor removal from the posterior fossa. The role of cerebro-cerebellar tract injuries in the etiology of CMS remains unclear, with recent studies suggesting that cerebro-cerebellar dysfunction may be related to chronic, rather than transient, symptomatology.

METHODS

We measured functional connectivity between the cerebellar cortex and functional nodes throughout the brain using fMRI acquired after tumor removal but prior to adjuvant therapy in a cohort of 70 patients diagnosed with medulloblastoma. Surgical lesions were mapped to the infratentorial anatomy, and connectivity with cerebral cortex was tested for statistical dependence on extent of cerebellar outflow pathway injury.

RESULTS

CMS diagnosis was associated with an increase in connectivity between the right cerebellar and left cerebral hemisphere, maximally between cerebellum and ventromedial prefrontal cortex (VM-PFC). Connectivity dependence on cerebellar outflow was significant for some speech nodes but not for VM-PFC, suggesting altered input to the cerebellum. Connectivity between posterior regions of cerebellar cortex and ipsilateral dentate nuclei was abnormal in CMS participants, maximally within the right cerebellar hemisphere.

CONCLUSIONS

The functional abnormalities we identified are notably upstream of where causal surgical injury is thought to occur, indicating a secondary phenomenon. The VM-PFC is involved in several functions that may be relevant to the symptomatology of CMS, including emotional control and motor learning. We hypothesize that these abnormalities may reflect maladaptive learning within the cerebellum consequent to disordered motor and limbic function by the periaqueductal gray and other critical midbrain targets.

Cerebellar mutism syndrome caused by bilateral cerebellar hemorrhage in adults: a case report and review of the literature

Cerebellar mutism syndrome (CMS) is a frequent complication of surgical intervention on posterior fossa in children. It has been only occasionally reported in adults and its features have not been fully characterized. In children and in young adults, medulloblastoma is the main reason for neurosurgery. A single case of postsurgical CMS is presented in an adult patient with a cerebellar hemorrhage and a systematic review of the published individual cases of CMS in adults was done. Literature review of individual cases found 30 patients, 18/30 (60%) males, from 20 to 71 years at diagnosis. All but one case was post-surgical, but in one of the post-surgical cases iatrogenic basilar artery occlusion was proposed as cause for CMS. The causes were: primary tumors of the posterior fossa in 16/22 (72.7%) metastasis in 3/30 (10%), ischemia in 3/30 (10%) cerebellar hemorrhage in 3/30 (10%), and benign lesions in 2/30 (6.7%) patients. 8/30 patients (26.7%) were reported as having persistent or incomplete resolution of CMS within 12 months. CMS is a rare occurrence in adults and spontaneous cerebellar hemorrhage has been reported in 3/30 (10%) adult patients. The generally accepted hypothesis is that CMS results from bilateral damage to the dentate nucleus or the dentate-rubro-thalamic tract, leading to cerebro-cerebellar diaschisis. Several causes might contribute in adults. The prognosis of CMS is slightly worse in adults than in children, but two thirds of cases show a complete resolution within 6 months.

Neuroanatomy of cerebellar mutism syndrome: the role of lesion location

Approximately 25% of paediatric patients who undergo cerebellar tumour resection develop cerebellar mutism syndrome. Our group recently showed that damage to the cerebellar deep nuclei and superior cerebellar peduncles, which we refer to as the cerebellar outflow pathway, is associated with an increased risk of cerebellar mutism syndrome. Here, we tested whether these findings replicate in an independent cohort. We evaluated the relationship between lesion location and the development of cerebellar mutism syndrome in an observational study of 56 paediatric patients ranging from five months to 14 years of age who underwent cerebellar tumour resection. We hypothesized that individuals who developed cerebellar mutism syndrome after surgery, relative to those who did not, would have lesions that preferentially intersect with: (i) the cerebellar outflow pathway and (ii) a previously generated 'lesion-symptom map' of cerebellar mutism syndrome. Analyses were conducted in accordance with pre-registered hypotheses and analytic methods (https://osf.io/r8yjv/). We found supporting evidence for both hypotheses. Compared to patients who did not develop cerebellar mutism syndrome, patients with cerebellar mutism syndrome (n = 10) had lesions with greater overlap with the cerebellar outflow pathway (Cohen's d = 0.73, P = 0.05), and the cerebellar mutism syndrome lesion-symptom map (Cohen's d = 1.1, P = 0.004). These results strengthen the association of lesion location with the risk of developing cerebellar mutism syndrome and demonstrate generalizability across cohorts. These findings may help to inform the optimal surgical approach to paediatric cerebellar tumours.

Adaptive, behavioral, and emotional outcomes following postoperative pediatric cerebellar mutism syndrome in survivors treated for medulloblastoma

OBJECTIVE

Patients who experience postoperative pediatric cerebellar mutism syndrome (CMS) during treatment for medulloblastoma have long-term deficits in neurocognitive functioning; however, the consequences on functional or adaptive outcomes are unknown. The purpose of the present study was to compare adaptive, behavioral, and emotional functioning between survivors with and those without a history of CMS.

METHODS

The authors examined outcomes in 45 survivors (15 with CMS and 30 without CMS). Comprehensive neuropsychological evaluations, which included parent-report measures of adaptive, behavioral, and emotional functioning, were completed at a median of 2.90 years following craniospinal irradiation.

RESULTS

Adaptive functioning was significantly worse in the CMS group for practical and general adaptive skills compared with the group without CMS. Rates of impairment in practical, conceptual, and general adaptive skills in the CMS group exceeded expected rates in the general population. Despite having lower overall intellectual functioning, working memory, and processing speed, IQ and related cognitive processes were uncorrelated with adaptive outcomes in the CMS group. No significant group differences or increased rates of impairment were observed for behavioral and emotional outcomes.

CONCLUSIONS

Survivors with CMS, compared with those without CMS, are rated as having significant deficits in overall or general adaptive functioning, with specific weakness in practical skills several years posttreatment. Findings from this study demonstrate the high risk for ongoing functional deficits despite acute recovery from symptoms of CMS, highlighting the need for intervention to mitigate such risk.

Postoperative cerebellar mutism syndrome is an acquired autism-like network disturbance

BACKGROUND

Cerebellar mutism syndrome (CMS) is a common and debilitating complication of posterior fossa tumor surgery in children. Affected children exhibit communication and social impairments that overlap phenomenologically with subsets of deficits exhibited by children with Autism spectrum disorder (ASD). Although both CMS and ASD are thought to involve disrupted cerebro-cerebellar circuitry, they are considered independent conditions due to an incomplete understanding of their shared neural substrates.

METHODS

In this study, we analyzed postoperative cerebellar lesions from 90 children undergoing posterior fossa resection of medulloblastoma, 30 of whom developed CMS. Lesion locations were mapped to a standard atlas, and the networks functionally connected to each lesion were computed in normative adult and pediatric datasets. Generalizability to ASD was assessed using an independent cohort of children with ASD and matched controls (n = 427).

RESULTS

Lesions in children who developed CMS involved the vermis and inferomedial cerebellar lobules. They engaged large-scale cerebellothalamocortical circuits with a preponderance for the prefrontal and parietal cortices in the pediatric and adult connectomes, respectively. Moreover, with increasing connectomic age, CMS-associated lesions demonstrated stronger connectivity to the midbrain/red nuclei, thalami and inferior parietal lobules and weaker connectivity to the prefrontal cortex. Importantly, the CMS-associated lesion network was independently reproduced in ASD and correlated with communication and social deficits, but not repetitive behaviors.

CONCLUSIONS

Our findings indicate that CMS-associated lesions may result in an ASD-like network disturbance that occurs during sensitive windows of brain development. A common network disturbance between CMS and ASD may inform improved treatment strategies for affected children.

Characterising the Long-Term Language Impairments of Children Following Cerebellar Tumour Surgery by Extracting Psycholinguistic Properties from Spontaneous Language

Following cerebellar tumour surgery, children may suffer impairments of spontaneous language. Yet, the language processing deficits underlying these impairments are poorly understood. This study is the first to try to identify these deficits for four levels of language processing in cerebellar tumour survivors. The spontaneous language of twelve patients who underwent cerebellar tumour surgery (age range 3-24 years) was compared against his or her controls using individual case statistics. A distinction was made between patients who experienced postoperative cerebellar mutism syndrome (pCMS) and those who did not. Time since surgery ranged between 11 months and 12;3 years. In order to identify the impaired language processing levels at each processing level (i.e., lexical, semantic, phonological and/or morphosyntactic) nouns and verbs produced in the spontaneous language samples were rated for psycholinguistic variables (e.g., concreteness). Standard spontaneous language measures (e.g., type-token ratio) were calculated as well. First, inter-individual heterogeneity was observed in the spontaneous language outcomes in both groups. Nine out of twelve patients showed language processing deficits three of whom were diagnosed with pCMS. Results implied impairments across all levels of language processing. In the pCMS-group, the impairments observed were predominantly morphosyntactic and semantic, but the variability in nature of the spontaneous language impairments was larger in the non-pCMS-group. Patients treated with cerebellar tumour surgery may show long-term spontaneous language impairments irrespective of a previous pCMS diagnosis. Individualised and comprehensive postoperative language assessments seem necessary, given the inter-individual heterogeneity in the language outcomes.

Laser interstitial thermal therapy in pediatric cerebellar epilepsy

Cerebellar lesional epilepsy is rare, commonly manifesting in early life and posing diagnostic and treatment challenges. Seizure semiology may be subtle, with repetitive eye blinking, face twitching, and irregular breathing, while EEG commonly remains unremarkable. Pharmacoresistance is the rule, and surgical intervention is the only treatment with the potential for cure. Novel minimally invasive techniques, such as laser interstitial thermal therapy (LITT), are emerging for surgically less accessible, deep-seated epileptogenic lesions. We report the case of a patient who presented with peculiar eye and face movements occurring episodically and stereotypically since the first weeks of life and was later diagnosed with cerebellar epilepsy related to a hamartoma. Refractory daily seizures, unresponsive to antiseizure medication, were followed by increasingly prominent gait ataxia and delayed speech development. Staged LITT was performed in two consecutive sessions at 3 and 4 years, leading to seizure cessation, neurological improvement, and developmental gains over a postsurgical follow-up period of 8 months. Our case highlights cerebellar lesional epilepsy as a rare but important differential diagnosis in children with paroxysmal disorders predominantly involving the face. Furthermore, we illustrate the radiological correlates of neurocognitive deficit related to the cerebellar lesion, manifesting as cerebello-cerebral diaschisis. Most importantly, our observations showcase LITT as a safe and effective therapeutic approach in cerebellar lesional epilepsy and an attractive alternative to open brain surgery, especially for deep-seated lesions in the pediatric population.

Cerebellar mutism is linked to midbrain volatility and desynchronization from speech cortices

Cerebellar mutism syndrome is a disorder of speech, movement and affect that can occur after tumour removal from the posterior fossa. Projections from the fastigial nuclei to the periaqueductal grey area were recently implicated in its pathogenesis, but the functional consequences of damaging these projections remain poorly understood. Here, we examine functional MRI data from patients treated for medulloblastoma to identify functional changes in key brain areas that comprise the motor system for speech, which occur along the timeline of acute speech impairment in cerebellar mutism syndrome. One hundred and twenty-four participants, all with medulloblastoma, contributed to the study: 45 with cerebellar mutism syndrome, 11 patients with severe postoperative deficits other than mutism, and 68 without either (asymptomatic). We first performed a data-driven parcellation to spatially define functional nodes relevant to the cohort that align with brain regions critical for the motor control of speech. We then estimated functional connectivity between these nodes during the initial postoperative imaging sessions to identify functional deficits associated with the acute phase of the disorder. We further analysed how functional connectivity changed over time within a subset of participants that had suitable imaging acquired over the course of recovery. Signal dispersion was also measured in the periaqueductal grey area and red nuclei to estimate activity in midbrain regions considered key targets of the cerebellum with suspected involvement in cerebellar mutism pathogenesis. We found evidence of periaqueductal grey dysfunction in the acute phase of the disorder, with abnormal volatility and desynchronization with neocortical language nodes. Functional connectivity with periaqueductal grey was restored in imaging sessions that occurred after speech recovery and was further shown to be increased with left dorsolateral prefrontal cortex. The amygdalae were also broadly hyperconnected with neocortical nodes in the acute phase. Stable connectivity differences between groups were broadly present throughout the cerebrum, and one of the most substantial differences-between Broca's area and the supplementary motor area-was found to be inversely related to cerebellar outflow pathway damage in the mutism group. These results reveal systemic changes in the speech motor system of patients with mutism, centred on limbic areas tasked with the control of phonation. These findings provide further support for the hypothesis that periaqueductal grey dysfunction (following cerebellar surgical injury) contributes to the transient postoperative non-verbal episode commonly observed in cerebellar mutism syndrome but highlights a potential role of intact cerebellocortical projections in chronic features of the disorder.

Medulloblastomas, CNS embryonal tumors, and cerebellar mutism syndrome: advances in care and future directions

Central nervous system (CNS) embryonal tumors, commonly found in pediatric patients, represent a heterogeneous mix of lesions with an overall poor (though improving) prognosis. Medulloblastomas are by far the most frequently encountered and most widely studied subtype, though others include atypical teratoid/rhabdoid tumors (AT/RTs), embryonal tumor with multilayered rosettes (ETMRs), and CNS neuroblastomas, FOX-R2 activated. The classification, diagnosis, and treatment of these lesions have evolved drastically over the years as their molecular underpinnings have been elucidated. We describe the most recent 2021 WHO Classification system, discuss current understanding of the genetic basis, and demonstrate current thinking in treatment for these highly complex tumors. Since surgical resection continues to remain a mainstay of treatment, preventing and managing surgical complications, especially cerebellar mutism syndrome (CMS), is paramount. We describe the current theories for the etiology of CMS and two centers' experience in mitigating its risks. As our surgical toolbox continues to evolve along with our understanding of these tumors, we hope future patients can benefit from both improved overall survival and quality of life.

Large-scale brain networks and intra-axial tumor surgery: a narrative review of functional mapping techniques, critical needs, and scientific opportunities

In recent years, a paradigm shift in neuroscience has been occurring from "localizationism," or the idea that the brain is organized into separately functioning modules, toward "connectomics," or the idea that interconnected nodes form networks as the underlying substrates of behavior and thought. Accordingly, our understanding of mechanisms of neurological function, dysfunction, and recovery has evolved to include connections, disconnections, and reconnections. Brain tumors provide a unique opportunity to probe large-scale neural networks with focal and sometimes reversible lesions, allowing neuroscientists the unique opportunity to directly test newly formed hypotheses about underlying brain structural-functional relationships and network properties. Moreover, if a more complete model of neurological dysfunction is to be defined as a "disconnectome," potential avenues for recovery might be mapped through a "reconnectome." Such insight may open the door to novel therapeutic approaches where previous attempts have failed. In this review, we briefly delve into the most clinically relevant neural networks and brain mapping techniques, and we examine how they are being applied to modern neurosurgical brain tumor practices. We then explore how brain tumors might teach us more about mechanisms of global brain dysfunction and recovery through pre- and postoperative longitudinal connectomic and behavioral analyses.

Neuroanatomy of Cerebellar Mutism Syndrome: The Role of Lesion Location

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

The Cerebellar Mutism Syndrome: Risk Assessment, Prevention and Treatment

Cerebellar mutism syndrome (CMS) has received increasing attention over the last decades as a complication of posterior fossa tumour surgery in children. Risk factors, aetiological aspects, and treatment measures of the syndrome have been investigated, yet the incidence of CMS remains unchanged. Overall, we are currently able to identify patients at risk, but we are unable to prevent it from occurring.Once CMS sets in, several symptomatic pharmacological treatments have been suggested, but only in smaller case series and not in randomized controlled trials, and it is not clear whether the treatment or time itself had a helpful effect.Within weeks to months, most patients regain their ability to speak after a phase with mutism or severely reduced speech; however, many patients continue to have speech and language deficits. At this point, anti-cancer treatment with chemotherapy and radiotherapy may be of focus more than the prognosis of CMS; however, many patients continue to have speech and language problems for months and years to come, and they are at high risk of other neurocognitive sequelae as well.Without reliable measures to prevent or treat the syndrome, we may look towards improving the prognosis of speech and neurocognitive functioning in these patients. As speech and language impairment is the cardinal symptom and late effect of CMS, the effect of intense and early-onset speech and language therapy as a standard of care in these patients should be investigated in relation to its effect on regaining speech capacity.

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.

Cerebellar mutism syndrome: From pathophysiology to rehabilitation

Cerebellar mutism syndrome (CMS) is a common complication following surgical resection of childhood tumors arising in the posterior fossa. Alteration of linguistic production, up to muteness and emotional lability, generally reported at least 24 h after the intervention, is the hallmark of post-operative CMS. Other associated traits include hypotonia and other cerebellar motor signs, cerebellar cognitive-affective syndrome, motor deficits from the involvement of the long pathways, and cranial neuropathies. Recovery usually takes 6 months, but most children are burdened with long-term residual deficits. The pathogenic mechanism is likely due to the damage occurring to the proximal efferent cerebellar pathway, including the dentate nucleus, the superior cerebellar peduncle, and its decussation in the mesencephalic tegmentum. Proven risk factors include brain stem invasion, diagnosis of medulloblastoma, midline localization, tumor size, invasion of the fourth ventricle, invasion of the superior cerebellar peduncle, left-handedness, and incision of the vermis. Currently, rehabilitation is the cornerstone of the treatment of patients with cerebellar mutism syndrome, and it must consider the three main impaired domains, namely speech, cognition/behavior, and movement.

Power and connectivity changes on electroencephalogram in postoperative cerebellar mutism

INTRODUCTION

Cerebellar mutism syndrome is a debilitating postoperative neurological complication following posterior fossa surgery in children. It is characterized by a significant lack or loss of speech. Injury to the dentato-thalamo-cortical pathway is thought to be the main anatomical substrate of cerebellar mutism syndrome; however, few studies have investigated the physiological changes using computed electroencephalogram.

CASE REPORT

Herein, we report a case of a nine-year-old girl who developed cerebellar mutism syndrome after excision of an ependymoma of the fourth ventricle and was followed up with evaluation of aphasia, gross motor function, and scalp electroencephalograms. Her language, dysmetria and gait ataxia gradually improved until day 605 after onset. Computed electroencephalogram analyses were performed for the relative power spectrum and connectivity at each frequency band. On the three electroencephalograms at days 109, 299, and 605 after onset, the relative power spectrum at the delta band transiently decreased and then increased, and the relative power spectrums at theta, beta, and gamma bands transiently increased and then decreased. Only the relative power spectrum in the alpha band continuously increased in the occipital area. Additionally, brain connectivity in the delta, beta, and gamma bands increased continuously.

CONCLUSION

We report a case of cerebellar mutism syndrome with recovery of language, dysmetria and gait ataxia in 20 months. Electroencephalogram analyses indicated transient changes in the powers of brain activity and continuous improvements in connectivity during the long follow-up, reflecting the plasticity and remodeling of brain function after cerebellar mutism syndrome. Power and connectivity analyses for EEG might be a tool to investigate underlying pathophysiology of cerebellar mutism syndrome.

A case of postoperative cerebellar mutism with hyperphagia in a child following gross total resection of medulloblastoma occupying the cerebellar vermis

INTRODUCTION

Cerebellar mutism syndrome is a well-known complication following posterior fossa tumor resection. Its incidence is markedly increased among patients with medulloblastoma. Patients typically present with an inability to communicate verbally due to disruption of the dentato-thalamocortical pathway.

CASE DESCRIPTION

We present a unique case of cerebellar mutism in a three-year-old girl who underwent gross total resection of medulloblastoma occupying the cerebellar vermis. In addition to mutism, the patient developed hyperphagia.

DISCUSSION

This case report aims to contribute to current understanding of the role of cerebello-hypothalamic connections in cerebellar mutism and their clinical significance.

Arterial Spin-Labeling Perfusion Metrics in Pediatric Posterior Fossa Tumor Surgery

BACKGROUND AND PURPOSE

Pediatric posterior fossa tumors often present with hydrocephalus; postoperatively, up to 25% of patients develop cerebellar mutism syndrome. Arterial spin-labeling is a noninvasive means of quantifying CBF and bolus arrival time. The aim of this study was to investigate how changes in perfusion metrics in children with posterior fossa tumors are modulated by cerebellar mutism syndrome and hydrocephalus requiring pre-resection CSF diversion.

MATERIALS AND METHODS

Forty-four patients were prospectively scanned at 3 time points (preoperatively, postoperatively, and at 3-month follow-up) with single- and multi-inflow time arterial spin-labeling sequences. Regional analyses of CBF and bolus arrival time were conducted using coregistered anatomic parcellations. ANOVA and multivariable, linear mixed-effects modeling analysis approaches were used. The study was registered at clinicaltrials.gov (NCT03471026).

RESULTS

CBF increased after tumor resection and at follow-up scanning (P = .045). Bolus arrival time decreased after tumor resection and at follow-up scanning (P = .018). Bolus arrival time was prolonged (P = .058) following the midline approach, compared with cerebellar hemispheric surgical approaches to posterior fossa tumors. Multivariable linear mixed-effects modeling showed that regional perfusion changes were more pronounced in the 6 children who presented with symptomatic obstructive hydrocephalus requiring pre-resection CSF diversion, with hydrocephalus lowering the baseline mean CBF by 20.5 (standard error, 6.27) mL/100g/min. Children diagnosed with cerebellar mutism syndrome (8/44, 18.2%) had significantly higher CBF at follow-up imaging than those who were not (P = .040), but no differences in pre- or postoperative perfusion parameters were seen.

CONCLUSIONS

Multi-inflow time arterial spin-labeling shows promise as a noninvasive tool to evaluate cerebral perfusion in the setting of pediatric obstructive hydrocephalus and demonstrates increased CBF following resolution of cerebellar mutism syndrome.

Left-handedness should not be overrated as a risk factor for postoperative speech impairment in children after posterior fossa tumour surgery: a prospective European multicentre study

PURPOSE

Cerebellar mutism syndrome (CMS) is a severe neurological complication of posterior fossa tumour surgery in children, and postoperative speech impairment (POSI) is the main component. Left-handedness was previously suggested as a strong risk factor for POSI. The aim of this study was to investigate the relationship between handedness and the risk of POSI.

METHODS

We prospectively included children (aged < 18 years) undergoing surgery for posterior fossa tumours in 26 European centres. Handedness was assessed pre-operatively and postoperative speech status was categorised as either POSI (mutism or reduced speech) or habitual speech, based on the postoperative clinical assessment. Logistic regression was used in the risk factor analysis of POSI as a dichotomous outcome.

RESULTS

Of the 500 children included, 37 (7%) were excluded from the present analysis due to enrolment at a reoperation; another 213 (43%) due to missing data about surgery (n = 37) and/or handedness (n = 146) and/or postoperative speech status (n = 53). Out of the remaining 250 (50%) patients, 20 (8%) were left-handed and 230 (92%) were right-handed. POSI was observed equally frequently regardless of handedness (5/20 [25%] in left-handed, 61/230 [27%] in right-handed, OR: 1.08 [95% CI: 0.40-3.44], p = 0.882), also when adjusted for tumour histology, location and age.

CONCLUSION

We found no difference in the risk of POSI associated with handedness. Our data do not support the hypothesis that handedness should be of clinical relevance in the risk assessment of CMS.

Posterior fossa syndrome in a population of children and young adults with medulloblastoma: a retrospective, multicenter Italian study on incidence and pathophysiology in a histologically homogeneous and consecutive series of 136 patients

INTRODUCTION

Posterior fossa syndrome (PFS) is a set of debilitating complications that can occur after surgery for posterior fossa tumors. This study aimed to assess the preoperative radiological and surgical risk factors for the onset of PFS in a histologically homogeneous population of children with medulloblastoma and compare it to a similar population of young adults.

METHODS

Included patients underwent posterior fossa surgery for medulloblastoma at 11 Italian neurosurgical wards (2003-2019) and were referred to Fondazione IRCCS Istituto Nazionale dei Tumori in Milan (INT) for postoperative treatments. We collected patients' pre- and post-operative clinical, surgical and radiological data from the INT charts. To compare the distribution of variables, we used the Mann-Whitney and Fisher tests for continuous and categorical variables, respectively.

RESULTS

136 patients (109 children and 27 young adults) were included in the study. Among children, 29 (27%) developed PFS, and all of them had tumors at midline site with invasion of the fourth ventricle. Radiological evidence of involvement of the right superior (39% versus 12%; p = 0.011) or middle cerebellar peduncles (52% versus 18%; p = 0.002) seemed more common in children who developed PFS. Young adults showed an expected lower incidence of PFS (4 out of 27; 15%), that may be due to anatomical, physiological and oncological elements.

CONCLUSIONS

This study confirmed some factors known to be associated with PFS onset and shed light on other debated issues. Our findings enhance an already hypothesized role of cerebellar language lateralization. The analysis of a population of young adults may shed more light on the often-neglected existence of PFS in non-pediatric patients.

The shifting role of the cerebellum in executive, emotional and social processing across the lifespan

The cerebellum's anatomical and functional organization and network interactions between the cerebellum and the cerebral cortex and subcortical structures are dynamic across the lifespan. Executive, emotional and social (EES) functions have likewise evolved during human development from contributing to primitive behaviors during infancy and childhood to being able to modulate complex actions in adults. In this review, we address how the importance of the cerebellum in the processing of EES functions might change across development. This evolution is driven by the macroscopic and microscopic modifications of the cerebellum that are occurring during development including its increasing connectivity with distant supra-tentorial cortical and sub-cortical regions. As a result of anatomical and functional changes, neuroimaging and clinical data indicate that the importance of the role of the cerebellum in human EES-related networks shifts from being crucial in newborns and young children to being only supportive later in life. In early life, given the immaturity of cortically mediated EES functions, EES functions and motor control and perception are more closely interrelated. At that time, the cerebellum due to its important role in motor control and sequencing makes EES functions more reliant on these computational properties that compute spatial distance, motor intent, and assist in the execution of sequences of behavior related to their developing EES expression. As the cortical brain matures, EES functions and decisions become less dependent upon these aspects of motor behavior and more dependent upon high-order cognitive and social conceptual processes. At that time, the cerebellum assumes a supportive role in these EES-related behaviors by computing their motor and sequential features. We suspect that this evolving role of the cerebellum has complicated the interpretation of its contribution to EES computational demands.

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.

Spatiotemporal changes in along-tract profilometry of cerebellar peduncles in cerebellar mutism syndrome

Cerebellar mutism syndrome, characterised by mutism, emotional lability and cerebellar motor signs, occurs in up to 39% of children following resection of medulloblastoma, the most common malignant posterior fossa tumour of childhood. Its pathophysiology remains unclear, but prior studies have implicated damage to the superior cerebellar peduncles. In this study, the objective was to conduct high-resolution spatial profilometry of the cerebellar peduncles and identify anatomic biomarkers of cerebellar mutism syndrome. In this retrospective study, twenty-eight children with medulloblastoma (mean age 8.8 ± 3.8 years) underwent diffusion MRI at four timepoints over one year. Forty-nine healthy children (9.0 ± 4.2 years), scanned at a single timepoint, served as age- and sex-matched controls. Automated Fibre Quantification was used to segment cerebellar peduncles and compute fractional anisotropy (FA) at 30 nodes along each tract. Thirteen patients developed cerebellar mutism syndrome. FA was significantly lower in the distal third of the left superior cerebellar peduncle pre-operatively in all patients compared to controls (FA in proximal third 0.228, middle and distal thirds 0.270, p = 0.01, Cohen's d = 0.927). Pre-operative differences in FA did not predict cerebellar mutism syndrome. However, post-operative reductions in FA were highly specific to the distal left superior cerebellar peduncle, and were most pronounced in children with cerebellar mutism syndrome compared to those without at the 1-4 month follow up (0.325 vs 0.512, p = 0.042, d = 1.36) and at the 1-year follow up (0.342, vs 0.484, p = 0.038, d = 1.12). High spatial resolution cerebellar profilometry indicated a site-specific alteration of the distal segment of the superior cerebellar peduncle seen in cerebellar mutism syndrome which may have important surgical implications in the treatment of these devastating tumours of childhood.

Networking of the Human Cerebellum: From Anatomo-Functional Development to Neurosurgical Implications

In the past, the cerebellum was considered to be substantially involved in sensory-motor coordination. However, a growing number of neuroanatomical, neuroimaging, clinical and lesion studies have now provided converging evidence on the implication of the cerebellum in a variety of cognitive, affective, social, and behavioral processes as well. These findings suggest a complex anatomo-functional organization of the cerebellum, involving a dense network of cortical territories and reciprocal connections with many supra-tentorial association areas. The final architecture of cerebellar networks results from a complex, highly protracted, and continuous development from childhood to adulthood, leading to integration between short-distance connections and long-range extra-cerebellar circuits. In this review, we summarize the current evidence on the anatomo-functional organization of the cerebellar connectome. We will focus on the maturation process of afferent and efferent neuronal circuitry, and the involvement of these networks in different aspects of neurocognitive processing. The final section will be devoted to identifying possible implications of this knowledge in neurosurgical practice, especially in the case of posterior fossa tumor resection, and to discuss reliable strategies to improve the quality of approaches while reducing postsurgical morbidity.

Pretreatment Normal WM Magnetization Transfer Ratio Predicts Risk of Radiation Necrosis in Patients with Medulloblastoma

BACKGROUND AND PURPOSE

Radiation necrosis, for which abnormal WM enhancement is a hallmark, is an uncommon complication of craniospinal irradiation in children with medulloblastoma. The magnetization transfer ratio measures macromolecular content, dominated by myelin in the WM. We investigated whether the pretreatment supratentorial (nonsurgical) WM magnetization transfer ratio could predict patients at risk for radiation necrosis after radiation therapy for medulloblastoma.

MATERIALS AND METHODS

Ninety-five eligible patients with medulloblastoma (41% female; mean age, 11.0 [SD, 5.4]  years) had baseline balanced steady-state free precession MR imaging before proton or photon radiation therapy. Associations among baseline supratentorial magnetization transfer ratio, radiation necrosis (spontaneously resolving/improving parenchymal enhancement within the radiation field)³, age, and the presence of visible brain metastases were explored by logistic regression and parametric/nonparametric techniques as appropriate.

RESULTS

Twenty-three of 95 (24.2%) children (44% female; mean age, 10.7 [SD, 6.7] years) developed radiation necrosis after radiation therapy (19 infratentorial, 1 supratentorial, 3 both). The mean pretreatment supratentorial WM magnetization transfer ratio was significantly lower in these children (43.18 versus 43.50, P = .03). There was no association between the supratentorial WM magnetization transfer ratio and age, sex, risk/treatment stratum, or the presence of visible brain metastases.

CONCLUSIONS

A lower baseline supratentorial WM magnetization transfer ratio may indicate underlying structural WM susceptibility to radiation necrosis and may identify children at risk for developing radiation necrosis after craniospinal irradiation for medulloblastoma.

Improved prediction of postoperative paediatric cerebellar mutism syndrome using an artificial neural network

Background

Postoperative paediatric cerebellar mutism syndrome (pCMS) is a common but severe complication which may arise following the resection of posterior fossa tumours in children. Two previous studies have aimed to preoperatively predict pCMS, with varying results. In this work, we examine the generalisation of these models and determine if pCMS can be predicted more accurately using an artificial neural network (ANN).

Methods

An overview of reviews was performed to identify risk factors for pCMS, and a retrospective dataset collected as per these defined risk factors from children undergoing resection of primary posterior fossa tumours. The ANN was trained on this dataset and its performance evaluated in comparison to logistic regression and other predictive indices via analysis of receiver operator characteristic curves. Area under the curve (AUC) and accuracy were calculated and compared using a Wilcoxon signed rank test, with p&lt;0.05 considered statistically significant.

Results

204 children were included, of whom 80 developed pCMS. The performance of the ANN (AUC 0.949; accuracy 90.9%) exceeded that of logistic regression (p&lt;0.05) and both external models (p&lt;0.001).

Conclusion

Using an ANN, we show improved prediction of pCMS in comparison to previous models and conventional methods.

Delayed cerebral atrophy after cerebellar stroke: topographical relation and clinical impact

Remote dysconnectivity following cerebellar ischaemic stroke may have a negative impact on supratentorial brain tissue. Since the cerebellum is connected to the individual cerebral lobes via contralateral tracts, cerebellar lesion topography might determine the distribution of contralateral supratentorial brain tissue changes. We investigated (i) the occurrence of delayed cerebral atrophy after cerebellar ischaemic stroke and its relationship to infarct volume; (ii) whether cerebellar stroke topography determines supratentorial atrophy location; and (iii) how cortical atrophy after cerebellar stroke impacts clinical outcome. We performed longitudinal volumetric MRI analysis of patients with isolated cerebellar stroke from the Swiss Stroke Registry database. Stroke location and volume were determined at baseline MRI. Delayed cerebral atrophy was measured as supratentorial cortical volumetric change at follow-up, in contralateral target as compared to ipsilateral reference-areas. In patients with bilateral stroke, both hemispheres were analysed separately. We obtained maps of how cerebellar lesion topography, determines the probability of delayed atrophy per distinct cerebral lobe. Clinical performance was measured with the National Institutes of Health Stroke Scale and modified Rankin Scale. In 29 patients (age 58 ± 18; 9 females; median follow-up: 6.2 months), with 36 datasets (7 patients with bilateral cerebellar stroke), delayed cerebral atrophy occurred in 28 (78%) datasets. A multivariable generalized linear model for a Poisson distribution showed that infarct volume (milliliter) in bilateral stroke patients was positively associated with the number of atrophic target areas (Rate ratio = 1.08; P = 0.01). Lobe-specific cerebral atrophy related to distinct topographical cerebellar stroke patterns. By ordinal logistic regression (shift analysis), more atrophic areas predicted higher 3-month mRS scores in patients with low baseline scores (baseline score 3–5: Odds ratio = 1.34; P = 0.02; baseline score 0–2: OR = 0.71; P = 0.19). Our results indicate that (i) isolated cerebellar ischaemic stroke commonly results in delayed cerebral atrophy and stroke volume determines the severity of cerebral atrophy in patients with bilateral stroke; (ii) cerebellar stroke topography affects the location of delayed cerebral atrophy; and (iii) delayed cerebral atrophy negatively impacts clinical outcome.

The medical therapy for cerebellar mutism syndrome: a case report and literature review

PURPOSE

Cerebellar mutism syndrome (CMS) represents a major complication affecting many children that undergo surgery for posterior fossa lesions. Etiology and pathophysiology are still not fully understood. CMS deeply influences quality of life and recovery of these patients. An effective treatment has not been defined yet. This case-based review aims at analyzing the available evidence and knowledge to better delineate this phenomenon and to determine whether CMS can be successfully treated with pharmacological therapy.

METHODS

Systematic research and retrieval of databases were conducted analyzing all papers where medical treatment of CMS was reported. A summary of the latest understanding and reports regarding definition, clinical manifestations, pathophysiology, management, and outcome of CMS has been conducted.

RESULTS

Consensus on definition of this syndrome is lacking. CMS is the term accepted by the Posterior Fossa Society in 2016. Pathophysiology is still poorly understood but the most likely mechanism is injury along proximal components of the efferent cerebellar pathway. Nine papers describing positive effects of pharmacological therapy for CMS have been identified. Fluoxetine, zolpidem, bromocriptine, and midazolam are the drugs that seem to alleviate symptoms of CMS and improve recovery. To date, cognitive rehabilitation and physiotherapy are the only treatment options available.

CONCLUSION

CMS has deep impact on affected children and their families. Despite attempts to identify preventive measures and treatment, cases still occur on a regular basis. Pharmacological treatments have been proposed to help reduce the symptoms of CMS with some promising results, but reports are limited; therefore, further studies are needed.

Cerebellar Mutism Syndrome: An Overview of the Pathophysiology in Relation to the Cerebrocerebellar Anatomy, Risk Factors, Potential Treatments, and Outcomes

Cerebellar mutism syndrome (CMS) is one the most disabling postoperative neurological complications after posterior fossa surgery in children. CMS is characterized by a transient mutism with a typical onset demonstrated within 2 days postoperatively accompanied by associated ataxia, hypotonia, and irritability. Several hypotheses for the anatomical basis of pathophysiology and risk factors have been suggested. However, a definitive theory and treatment protocols have not yet been determined. Animal histological and electrophysiological studies and more recent human imaging studies have demonstrated the existence of a compartmentalized representation of cerebellar function, the understanding of which might provide more information on the pathophysiology. Damage to the dentatothalamocortical pathway and cerebrocerebellar diaschisis have been described as the anatomical substrate to the CMS. The risk factors, which include tumor type, brainstem invasion, tumor localization, tumor size, and vermal splitting technique, have not yet been clearly elucidated. The efficacy of potential pharmacological and speech therapies has been studied in small trials. Long-term motor speech deficits and associated cognitive and behavioral disturbances have now been found to be common among CMS survivors, affecting their development and requiring rehabilitation, leading to significant financial effects on the healthcare system and distress to the family. The aim of the present review was to outline the cerebellar anatomy and function and its connections in relationship to the pathophysiology and to refine the risk factors and treatment strategies for CMS.

Cerebellum and Prematurity: A Complex Interplay Between Disruptive and Dysmaturational Events

The cerebellum plays a critical regulatory role in motor coordination, cognition, behavior, language, memory, and learning, hence overseeing a multiplicity of functions. Cerebellar development begins during early embryonic development, lasting until the first postnatal years. Particularly, the greatest increase of its volume occurs during the third trimester of pregnancy, which represents a critical period for cerebellar maturation. Preterm birth and all the related prenatal and perinatal contingencies may determine both dysmaturative and lesional events, potentially involving the developing cerebellum, and contributing to the constellation of the neuropsychiatric outcomes with several implications in setting-up clinical follow-up and early intervention.

Living with the cerebellar mutism syndrome: long-term challenges of the diagnosis

BACKGROUND

After posterior fossa tumour surgery, up to 39% of children experience postoperative cerebellar mutism syndrome (CMS) characterized by mutism and other motor and cognitive impairments. There is a lack of knowledge on the patient-reported challenges and long-term needs. Consequently, no specific recommendations exist for rehabilitative and supportive interventions for patients with CMS. The aims of this study were to explore the patients' experiences related to the sequelae of CMS, to identify challenges and needs regarding support and rehabilitation in the period of growing from child to adult and to add perspectives for future developments of supportive care and rehabilitative guidelines.

METHODS

Ten semi-structured interviews were conducted with young adults diagnosed with CMS as children. A thematic analysis identified four themes describing challenges impacting aspects of the participants' lives.

RESULTS

Four main themes were identified and highlight the rehabilitative need for focus on verbal and non-verbal communication skills in addition to the physical impairments. We found that brain tumour survivors with CMS can benefit from social and educational rehabilitation, straightforward and truthful information, support in structuring their everyday lives and increased public knowledge of CMS.

CONCLUSION

Children with CMS face a variety of challenges affecting many aspects of their everyday lives. They should be entitled to the elements of a current rehabilitation initiative for childhood cancer to support patients' social disability and educational decline. Finally, we identified a need for an official information publication.

Clinical features, neurologic recovery, and risk factors of postoperative posterior fossa syndrome and delayed recovery: a prospective study

BACKGROUND

Posterior fossa syndrome (PFS) is a known consequence of medulloblastoma resection. Our aim was to clinically define PFS, its evolution over time, and ascertain risk factors for its development and poor recovery.

METHODS

Children with medulloblastoma treated at St Jude Children's Research Hospital from 6/2013 to 7/2019 received standardized neurological examinations, before and periodically after radiation therapy. Most (98.3%) were enrolled on the ongoing multi-institutional protocol (SJMB12; NCT01878617).

RESULTS

Sixty (34%) of 178 evaluated children had PFS. Forty (23%) had complete mutism (PFS1) and 20 (11%) had diminished speech (PFS2). All children with PFS had severe ataxia and 42.5% of PFS1 had movement disorders. By multivariable analysis, younger age (P = .0005) and surgery in a low-volume surgery center (P = .0146) increased PFS risk, while Sonic Hedgehog tumors had reduced risk (P = .0025). Speech and gait returned in PFS1/PFS2 children at a median of 2.3/0.7 and 2.1/1.5 months, respectively, however, 12 (44.4%) of 27 PFS1 children with 12 months of follow-up were nonambulatory at 1 year. Movement disorder (P = .037) and high ataxia score (P < .0001) were associated with delayed speech recovery. Older age (P = .0147) and high ataxia score (P < .0001) were associated with delayed gait return. Symptoms improved in all children but no child with PFS had normal neurologic examination at a median of 23 months after surgery.

CONCLUSIONS

Categorizing PFS into types 1 and 2 has prognostic relevance. Almost half of the children with PFS1 with 12-month follow-up were nonambulatory. Surgical experience was a major modifiable contributor to the development of PFS.

Association between cerebral perfusion and paediatric postoperative cerebellar mutism syndrome after posterior fossa surgery-a systematic review

BACKGROUND

Paediatric postoperative cerebellar mutism syndrome (ppCMS) is a common complication following the resection of a cerebellar tumour in children. It is hypothesized that loss of integrity of the cerebellar output tracts results in a cerebello-cerebral "diaschisis" and reduced function of supratentorial areas of the brain.

METHODS

We performed a systematic review of the literature according to the PRISMA guidelines, in order to evaluate the evidence for hypoperfusion or hypofunction in the cerebral hemispheres in patients with ppCMS. Articles were selected based on the predefined eligibility criteria and quality assessment.

RESULTS

Five studies were included, consisting of three prospective cohort studies, one retrospective cohort study and one retrospective case control study. Arterial spin labelling (ASL) perfusion MRI, dynamic susceptibility contrast (DSC) perfusion MRI and single photon emission computed tomography (SPECT) were used to measure the cerebral and cerebellar tissue perfusion or metabolic activity. Reduced cerebral perfusion was predominantly demonstrated in the frontal lobe.

CONCLUSIONS

This systematic review shows that, after posterior fossa tumour resection, cerebral perfusion is reduced in ppCMS patients compared to patients without ppCMS. Well-powered prospective studies, including preoperative imaging, are needed to ascertain the cause and role of hypoperfusion in the pathophysiology of the syndrome.

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.

Exclusive Hyperfractionated Radiation Therapy and Reduced Boost Volume for Standard-Risk Medulloblastoma: Pooled Analysis of the 2 French Multicentric Studies MSFOP98 and MSFOP 2007 and Correlation With Molecular Subgroups

PURPOSE

Medulloblastoma has recently been characterized as a heterogeneous disease with 4 distinct molecular subgroups: wingless (WNT), sonic hedgehog (SHH), group 3, and group 4, with a new definition of risk stratification. We report progression-free survival, overall survival, and long-term cognitive effects in children with standard-risk medulloblastoma exclusively treated with hyperfractionated radiation therapy (HFRT), reduced boost volume, and online quality control, and we explore the prognostic value of biological characteristics in this chemotherapy-naïve population.

METHODS AND MATERIALS

Patients with standard-risk medulloblastoma were enrolled in 2 successive prospective multicentric studies, MSFOP 98 and MSFOP 2007, and received exclusive HFRT (36 Gy, 1 Gy/fraction twice daily) to the craniospinal axis followed by a boost at 68 Gy restricted to the tumor bed (1.5 cm margin), with online quality assurance before treatment. Patients with MYC or MYCN amplification were not excluded at the time of the study. We report progression-free survival and overall survival in the global population, and according to molecular subgroups as per World Health Organization 2016 molecular classification, and we present cognitive evaluations based on the Wechsler scale.

RESULTS

Data from 114 patients included in the MSFOP 98 trial from December 1998 to October 2001 (n = 48) and in the MSFOP 2007 from October 2008 to July 2013 (n = 66) were analyzed. With a median follow-up of 16.2 (range, 6.4-19.6) years for the MSFOP 98 cohort and 6.5 (1.6-9.6) years for the MSFOP 2007 cohort, 5-year overall survival and progression-free survival in the global population were 84% (74%-89%) and 74% (65%-81%), respectively. Molecular classification was determined for 91 patients (WNT [n = 19], SHH [n = 12], and non-WNT/non-SHH [n = 60]-including group 3 [n = 9], group 4 [n = 29], and not specified [n = 22]). Our results showed more favorable outcome for the WNT-activated subgroup and a worse prognosis for SHH-activated patients. Three patients had isolated extra-central nervous system relapse. The slope of neurocognitive decline in the global population was shallower than that observed in patients with a normofractionated regimen combined with chemotherapy.

CONCLUSIONS

HFRT led to a 5-year survival rate similar to other treatments combined with chemotherapy, with a reduced treatment duration of only 6 weeks. We confirm the MSFOP 98 results and the prognostic value of molecular status in patients with medulloblastoma, even in the absence of chemotherapy. Intelligence quotient was more preserved in children with medulloblastoma who received exclusive HFRT and reduced local boost, and intelligence quotient decline was delayed compared with patients receiving standard regimen. HFRT may be appropriate for patients who do not consent to or are not eligible for prospective clinical trials; for patients from developing countries for whom aplasia or ileus may be difficult to manage in a context of high cost/effectiveness constraints; and for whom shortened duration of RT may be easier to implement.

The supplementary motor area syndrome and the cerebellar mutism syndrome: a pathoanatomical relationship?

PURPOSE

The supplementary motor area (SMA) syndrome affects adults after tumour resection in SMA neighbouring motor cortex. Cerebellar mutism syndrome (CMS) affects children after tumour resection in the posterior fossa. Both syndromes include disturbances in speech and motor function. The causes of the syndromes are unknown; however, surgical damage to the dentato-thalamo-cortical pathway (DTCP) has been associated with CMS. Thus, an anatomical link between the areas associated with the syndromes is possible. We discuss the syndromes and their possible relationship through the DTCP.

METHODS

We identified 61 articles (cohort studies, case reports and reviews) in MEDLINE and Embase searching for CMS, SMA syndrome or DTCP or synonyms and reviewed for evidence linking CMS and SMA.

RESULTS

We found that SMA syndrome and CMS are similar regarding (1) surgical causation; (2) symptoms including speech impairment, disturbance in motor function and facial dysfunction; (3) delayed onset; (4) the courses of the syndromes are transient; and (5) long-term sequelae are seen in both. Relevant differences include age predominance of adults in SMA syndrome versus children in CMS.

CONCLUSIONS

The similarities of the two syndromes could be traced back to their mutual connection through the DTCP and their membership to a cerebro-cerebellar circuit. The connectivity network could explain the emotional changes and speech reduction in CMS. The difference in time of post-surgical onset may be related to the anatomical distance between the surgical damage to the cerebellum and the SMA, respectively, and the effector neural loop underpinning symptoms.

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.

Cerebellar mutism syndrome: current approaches to minimize risk for CMS

PURPOSE

Cerebellar mutism syndrome (CMS) is a serious source of morbidity following posterior fossa surgery in the pediatric population. However, methods for effectively decreasing its incidence and impact remain unclear. It is our aim to examine the impact of adjusting surgical factors, namely the use of a telovelar approach and avoidance of cavitronic ultrasonic aspirator, on the incidence of CMS in our population as well as outlining potential pre-, intra-, and postoperative factors that may contribute to its development.

METHODS

Retrospective review was performed to identify patients undergoing posterior fossa surgery for resection of a medulloblastoma. Demographic, surgical, and postoperative data were collected. These data were analyzed for possible correlations to the risk of developing CMS via univariate analysis. For factors found to be significant, a multivariate analysis was performed to assess their independence.

RESULTS

Seven of 65 patients (10.8%) developed CMS postoperatively. Factors found to be significantly associated with a higher risk of CMS were the degree of retraction utilized during the procedure (p = 0.0000) and incision of the vermis (p = 0.0294). Although they did not reach the threshold of statistical significance, tumor vascularity (p = 0.19), adoption of a transvermian approach (p = 0.19), and lack of intraoperative imaging (p = 0.17) exhibited strongly suggestive trends towards a correlation with CMS.

DISCUSSION

In an effort to reduce the incidence and severity of CMS in our population, our institution adopted surgical practices that minimize tissue trauma and mitigate postoperative edema. This included the use of a telovelar over a transvermian approach to obviate the need for vermian incision, avoidance of the CUSA, and minimization of heavy retraction during surgery. This was successful in reducing the incidence of CMS from 39% in our medulloblastoma patients to 10.8%. The development of CMS after posterior fossa surgery appears to be a "two-hit" phenomenon requiring a combination of existing predisposition, surgical injury, and postoperative exacerbation. Therefore, it is critical to identify the factors involved at each stage and investigate treatments to target them appropriately.

The Cerebellar Cognitive Affective Syndrome-a Meta-analysis

The cerebellar cognitive affective syndrome (CCAS) was first described by Schmahmann and Sherman in 1998. Despite their clear depiction of the syndrome, it is our experience that the CCAS has not yet found solid ground as a disease entity in routine clinical practice. This made us question the dimension of the CCAS in cerebellar patients. We performed a systematic review of the literature according to the PRISMA guidelines, in order to answer the question whether patients with acquired isolated cerebellar lesions perform significantly worse on neuropsychological testing compared to healthy controls. Studies were selected based on the predefined eligibility criteria and quality assessment. The systematic search resulted in ten studies, mainly observational cohorts consecutively including adult patients with isolated cerebellar lesions. Patients were compared to healthy controls, and neuropsychological investigation was done within one year of diagnosis. Meta-analysis of the twelve tests that were done in two or more studies showed that cerebellar patients perform significantly worse on Phonemic Fluency, Semantic Fluency, Stroop Test (naming, reading and interference), Block Design test and WMS-R visual memory. Cerebellar patients have significant and relevant deficits in the visuospatial, language and executive function domain. This meta-analysis therefore emphasizes the importance of the cerebellar cognitive affective syndrome as described by Schmahmann and Sherman.

Posterior fossa syndrome and increased mean diffusivity in the olivary bodies

OBJECTIVE

Posterior fossa syndrome (PFS) is a common postoperative complication following resection of posterior fossa tumors in children. It typically presents 1 to 2 days after surgery with mutism, ataxia, emotional lability, and other behavioral symptoms. Recent structural MRI studies have found an association between PFS and hypertrophic olivary degeneration, which is detectable as T2 hyperintensity in the inferior olivary nuclei (IONs) months after surgery. In this study, the authors investigated whether immediate postoperative diffusion tensor imaging (DTI) of the ION can serve as an early imaging marker of PFS.

METHODS

The authors retrospectively reviewed pediatric brain tumor patients treated at their institution, Lucile Packard Children's Hospital at Stanford, from 2004 to 2016. They compared the immediate postoperative DTI studies obtained in 6 medulloblastoma patients who developed PFS to those of 6 age-matched controls.

RESULTS

Patients with PFS had statistically significant increased mean diffusivity (MD) in the left ION (1085.17 ± 215.51 vs 860.17 ± 102.64, p = 0.044) and variably increased MD in the right ION (923.17 ± 119.2 vs 873.67 ± 60.16, p = 0.385) compared with age-matched controls. Patients with PFS had downward trending fractional anisotropy (FA) in both the left (0.28 ± 0.06 vs 0.23 ± 0.03, p = 0.085) and right (0.29 ± 0.06 vs 0.25 ± 0.02, p = 0.164) IONs compared with age-matched controls, although neither of these values reached statistical significance.

CONCLUSIONS

Increased MD in the ION is associated with development of PFS. ION MD changes may represent an early imaging marker of PFS.

Arterial spin labeling perfusion changes of the frontal lobes in children with posterior fossa syndrome

OBJECTIVE

Posterior fossa syndrome (PFS) is a common complication following the resection of posterior fossa tumors in children. The pathophysiology of PFS remains incompletely elucidated; however, the wide-ranging symptoms of PFS suggest the possibility of widespread cortical dysfunction. In this study, the authors utilized arterial spin labeling (ASL), an MR perfusion modality that provides quantitative measurements of cerebral blood flow without the use of intravenous contrast, to assess cortical blood flow in patients with PFS.

METHODS

A database of medulloblastoma treated at the authors' institution from 2004 to 2016 was retrospectively reviewed, and 14 patients with PFS were identified. Immediate postoperative ASL for patients with PFS and medulloblastoma patients who did not develop PFS were compared. Additionally, in patients with PFS, ASL following the return of speech was compared with immediate postoperative ASL.

RESULTS

On immediate postoperative ASL, patients who subsequently developed PFS had statistically significant decreases in right frontal lobe perfusion and a trend toward decreased perfusion in the left frontal lobe compared with controls. Patients with PFS had statistically significant increases in bilateral frontal lobe perfusion after the resolution of symptoms compared with their immediate postoperative imaging findings.

CONCLUSIONS

ASL perfusion imaging identifies decreased frontal lobe blood flow as a strong physiological correlate of PFS that is consistent with the symptomatology of PFS. This is the first study to demonstrate that decreases in frontal lobe perfusion are present in the immediate postoperative period and resolve with the resolution of symptoms, suggesting a physiological explanation for the transient symptoms of PFS.

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.

Intelligence and posterior fossa tumors in Brazilian youth

Central nervous system tumors are the most frequent solid neoplasms in childhood and are frequently located in posterior fossa (PF). In Brazil, this diagnosis is associated to high mortality rates and this context is increasingly worrisome outside of large urban centers in which delayed diagnosis and defaulting from treatment compromise survivorship. Moreover, the lesion and therapeutic toxicity compromise cognitive domains. This study investigated the impact of PF tumors and their treatments on the intellectual capacity of 37 children and adolescents aged 6 to 16, divided into two groups: patients with low grade tumors, submitted only to neurosurgery (G1) and with tumors of higher malignancy submitted to neurosurgery, chemotherapy, and/or radiotherapy (G2). Using the Wechsler Intelligence Scales for Children, data reveal that G1 presented preserved mean performance, while G2 presented low average performance. Cluster-type analysis divided the participants into two groups regarding intelligence, clinical and sociodemographic variables. Inferential statistical analysis highlighted the influence of antineoplastic treatment on nonverbal domains. Mother's schooling demonstrated influence on verbal domains, revealing an important dissociation pattern. The results suggest the relevance of sociocultural factors on the expression of the damage, as well as the administration of radiotherapy at critical neurodevelopmental stages.