Symptoms before and after posterior fossa surgery in pediatric patients

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: the importance of preoperative language assessment

Children undergoing surgical removal of tumors in the posterior cranial fossa can encounter a varied and complex constellation of neurological symptoms, called cerebellar mutism, defined as a disturbance in the planning and programming of motor language with preserved understanding, behavioral disorders such as inattention, visual-spatial disorganization, personality change, as well as ataxia and dysmetria. In the last years, several groups have been trying to establish risk factors or even predictive scores in order to be able at least in part to predict the appearance of speech disorders before surgery. We report on a child with pilocytic astrocytoma of the cerebellar vermis who had already been diagnosed with developmental linguistic delay two years earlier. This disorder initially worsened after surgery and later improved in the following 12 months. The aim of this paper is to emphasize the importance of preoperative neuropsychological evaluation. The present case, along with those reported in the literature, suggests that the risk of long-term cerebellar mutism is higher in children with preoperative speech disorders. In these patients a thorough assessment of cognitive and linguistic functions is therefore necessary to better evaluate the risk of cerebellar mutism after surgery.

Prospective longitudinal decline in cognitive-communication skills following treatment for childhood brain tumor

BACKGROUND

The effect of childhood brain tumor and its treatments on the developing brain are recognized to cause late-occurring structural and functional changes, inclusive of neurocognitive and communication disturbances.

AIMS

The aim of the present study was to investigate changes in function in the prospective cognitive-communication and language abilities of two children surviving childhood brain tumor (CBT) over a 12-month period post-treatment.

METHODS

The comprehensive language and cognitive-communication abilities of two cases (male aged 7;8-8;8, female aged 10;9-11;9) were assessed at two timepoints over a 12-month period: six months and 18 months following completion of CBT cancer treatment.

RESULTS

Findings revealed a sharp decline in problem solving abilities over a 12-month period in the early stages of recovery from CBT in both cases examined, despite no or mild-moderate deficits in cognitive-communication or language function at initial assessment. Pre-literacy skills were noted to deteriorate on one task for one child, despite intact abilities at first assessment.

CONCLUSIONS

The findings of progressive deterioration of cognitive-communication skills in both children treated for CBT highlights a clear need for ongoing surveillance and full comprehensive assessment across development. The critical need for ongoing management after discharge and implementation of early intervention throughout development is highlighted.

Communication and swallowing outcomes of children diagnosed with childhood brain tumor or leukemia: A systematic review

The purpose of this systematic review was to appraise and synthesize evidence on communication and swallowing outcomes associated with childhood brain tumor or leukemia (CBTL). A comprehensive database and grey literature search was conducted. Studies included: (a) peer-reviewed research published between 1998 and 2019, (b) English language, (c) children aged 0-16 years diagnosed with CBTL, and (d) used outcome measures focused on communication and/or swallowing. Quality assessment was completed and certainty of evidence rated using Grading of Recommendations Assessment, Development and Evaluation (GRADE). Fifty-seven studies met inclusion criteria: 46 examined communication, seven examined swallowing, and four considered both. Most studies were descriptive and prospective. Communication difficulties were frequently reported and apparent at one or more points from diagnosis to survivorship. Swallowing difficulties were frequently reported during oncology treatment. Despite quality assessment revealing methodological shortcomings, results have implications for clinical services and future research.

Cerebellar mutism: the predictive role of preoperative language evaluation

BACKGROUND

The association between preoperative language impairment and development of cerebellar mutism after surgical treatment of posterior fossa tumors has gained increasing interest in recent years based on the concept that both local compression/infiltration of the infratentorial periventricular anatomical structures involved in speech and language, as well as an increased distraction of supratentorial periventricular anatomical structures, due to an associated hydrocephalus, involved in the coordination of speech circuits, might lead to the subclinical presence of language disturbances already at diagnosis, predicting the development of a cerebellar mutism syndrome after tumor removal.

METHODS

A thorough review of the literature on the subject has been performed, together with a review of our institutional experience reporting the related long-term (10 years) results.

RESULTS AND CONCLUSIONS

According to our institutional experience, 20/70 (28.5%) children presented preoperative language impairment and developed cerebellar mutism after surgery. A residual impairment persists in 75% of the cases at a follow-up of 2 years, and in 50% of the cases at 10 years, a finding which actually depicts cerebellar mutism no more as a transient deficit but among long-term sequelae. The appearance of complex dysarthria in the postoperative period is a negative prognostic factor for the long-term persistence of speech disturbances.

Establishing reproducible predictors of cerebellar mutism syndrome based on pre-operative imaging

PURPOSE

To establish some explicit, feasible, and reproducible predictors for CMS.

MATERIALS AND METHODS

This study was a retrospective case study. Data were obtained from 82 patients with medulloblastoma at a single center, Beijing Tiantan Hospital. Based on medical records, we created two independent samples: the CMS group comprising 23 patients and the non-CMS group comprising 23 patients. Pre-operative imaging was studied by performing quantitative assessments of specific indicators.

RESULTS

The CMS group showed greater differences in pre-operative imaging data with the non-CMS group. The A_axi/d_axi ratio in pre-operative MR imaging captured in the axial plane was used to quantify the compression of the cerebellum and brainstem, and significant differences were observed between the CMS group and non-CMS group (p = 0.0002). In the sagittal plane, D_sag*d_sag was used to quantify the area of the tumor that invaded the brainstem, and significant differences were observed between the two groups (p = 0.0003). In the coronal plane, A_cor/d_cor was used to quantify the compression of the upper functional brain region, and significant differences were noted between the two groups (p = 0.0219). Additionally, Evans' index was introduced to quantify the degree of hydrocephalus. The CMS group tended to show an increased Evans' index (p = 0.0027).

CONCLUSION

Based on pre-operative imaging data, some reproducible predictors, such as A_axi/d_axi, D_sag*d_sag, A_cor/d_cor, and Evans' index, were established.

MRI features as a helpful tool to predict the molecular subgroups of medulloblastoma: state of the art

Medulloblastoma is the most common malignant pediatric brain tumor. Medulloblastoma should not be viewed as a single disease, but as a heterogeneous mixture of various subgroups with distinct characteristics. Based on genomic profiles, four distinct molecular subgroups are identified: Wingless (WNT), Sonic Hedgehog (SHH), Group 3 and Group 4. Each of these subgroups are associated with specific genetic aberrations, typical age of onset as well as survival prognosis. Magnetic resonance imaging (MRI) is performed for all patients with brain tumors, and has a key role in the diagnosis, surgical guidance and follow up of patients with medulloblastoma. Several studies indicate MRI as a promising tool for early detection of medulloblastoma subgroups. The early identification of the subgroup can influence the extent of surgical resection, radiotherapy and chemotherapy targeted treatments. In this article, we review the state of the art in MRI-facilitated medulloblastoma subgrouping, with a summary of the main MRI features in medulloblastoma and a brief discussion on molecular characterization of medulloblastoma subgroups. The main focus of the article is MRI features that correlate with medulloblastoma subtypes, as well as features suggestive of molecular subgroups. Finally, we briefly discuss the latest trends in MRI studies and latest developments in molecular characterization.

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.

Cerebellar mutism syndrome

Cerebellar mutism most commonly, but not exclusively, develops in children after surgery for midline cerebellar or intraventricular tumors in the posterior fossa, typically medulloblastoma. Cerebellar mutism syndrome (CMS) comprises a complex set of neurologic and neurocognitive signs and symptoms, the cardinal and central component of which is an initially profound but usually reversible speech disorder. As such, CMS is currently recognized as an extreme form of the so-called cerebellar cognitive affective syndrome (Schmahmann syndrome). The putative cause of CMS is a substantial surgical injury to the proximal components of the bilateral efferent cerebellar pathways, disrupting cerebellar input to the supratentorial brain. The resultant cerebellocerebral diaschisis may lead to supratentorial cortical perfusion depression with frontal predominance. The speech disorder is, therefore, likely an apraxia. As our understanding of the mechanism and the clinical spectrum of CMS evolves, clinically useful preoperative risk stratification schemes, adjustments to surgical strategies and techniques, and possible early therapeutic-rehabilitative measures are being sought and developed to reduce the burden of this severe and particularly handicapping chronic morbidity on affected individuals and their families.

Consensus paper on post-operative pediatric cerebellar mutism syndrome: the Iceland Delphi results

INTRODUCTION

Confusion has surrounded the description of post-operative mutism and associated morbidity in pediatric patients with cerebellar tumors for years. The heterogeneity of definitions and diagnostic features has hampered research progress within the field, and to date, no international guidelines exist on diagnosis, prevention, treatment, or follow-up of this debilitating condition. An international group of clinicians and researchers from multiple relevant disciplines recently formed a cohesive panel to formulate a new working definition and agree upon standardized methods for diagnosis and follow-up.

METHODS

Consensus was obtained using the modified nominal group technique, involving four rounds of online Delphi questionnaires interspersed with a structured consensus conference with lectures, group work, and open discussion sessions.

RESULTS

A new, proposed definition of "post-operative pediatric CMS" was formed, preliminary recommendations for diagnostic and follow-up procedures were created, two working groups on a new scoring scale and risk prediction and prevention were established, and areas were identified where further information is needed.

DISCUSSION

The consensus process was motivated by desire to further research and improve quality of life for pediatric brain tumor patients. The Delphi rounds identified relevant topics and established basic agreement, while face-to-face engagement helped resolve matters of conflict and refine terminology. The new definition is intended to provide a more solid foundation for future clinical and research work. It is thought as a consensus for moving forward and hopefully paves the way to developing a standard approach to this challenging problem with the advent of better scoring methods and ultimate goal of reducing the risk of CMS.

Molecular subgroups of medulloblastoma identification using noninvasive magnetic resonance spectroscopy

BACKGROUND

Medulloblastomas in children can be categorized into 4 molecular subgroups with differing clinical characteristics, such that subgroup determination aids in prognostication and risk-adaptive treatment strategies. Magnetic resonance spectroscopy (MRS) is a widely available, noninvasive tool that is used to determine the metabolic characteristics of tumors and provide diagnostic information without the need for tumor tissue. In this study, we investigated the hypothesis that metabolite concentrations measured by MRS would differ between molecular subgroups of medulloblastoma and allow accurate subgroup determination.

METHODS

MRS was used to measure metabolites in medulloblastomas across molecular subgroups (SHH = 12, Groups 3/4 = 17, WNT = 1). Levels of 14 metabolites were analyzed to determine those that were the most discriminant for medulloblastoma subgroups in order to construct a multivariable classifier for distinguishing between combined Group 3/4 and SHH tumors.

RESULTS

Medulloblastomas across molecular subgroups revealed distinct spectral features. Group 3 and Group 4 tumors demonstrated metabolic profiles with readily detectable taurine, lower levels of lipids, and high levels of creatine. SHH tumors showed prominent choline and lipid with low levels of creatine and little or no evidence of taurine. A 5-metabolite subgroup classifier inclusive of creatine, myo-inositol, taurine, aspartate, and lipid 13a was developed that could discriminate between Group 3/4 and SHH medulloblastomas with excellent accuracy (cross-validated area under the curve [AUC] = 0.88).

CONCLUSIONS

The data show that medulloblastomas of Group 3/4 differ metabolically as measured using MRS when compared with SHH molecular subgroups. MRS is a useful and accurate tool to determine medulloblastoma molecular subgroups.

Cause and outcome of cerebellar mutism: evidence from a systematic review

PURPOSE

Cerebellar mutism is a serious neurosurgical complication after posterior fossa surgery, but the cause, incidence and outcome remain incompletely defined. The aim of this paper was to identify and review all reports of this phenomenon to better delineate and improve the evidence base.

METHODS

A systematic search and retrieval of databases was conducted using advanced search techniques. Review/outcomes criteria were developed, and study quality was determined.

RESULTS

The retrieval identified 2,281 papers of which 96 were relevant, identifying 650 children with cerebellar mutism. Causative factors, clinical features and outcomes were reported variably; papers focussed on multiple areas, the majority reporting incidence in single or series of case studies with little or no analysis further than description.

CONCLUSIONS

The complexity and variability of data reporting, likely contributing factors and outcomes make cerebellar mutism difficult to predict in incidence and the degree of impact that may ensue. A clear and accepted universal definition would help improve reporting, as would the application of agreed outcome measures. Clear and consistent reporting of surgical technique remains absent. Recommendations for practice are provided.