Neurological dysfunction associated with postoperative cerebellar mutism

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.

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.

Perioperative risk factors for long-term intelligence in children with postoperative cerebellar mutism syndrome after medulloblastoma surgery

OBJECTIVE

Approximately 7%-50% of children with medulloblastoma (MB) develop postoperative cerebellar mutism syndrome (pCMS). pCMS has a short-term negative impact on intelligence, but effects on long-term outcomes are contradictory. The aim of this study was to assess long-term effects of pCMS in MB patients on aspects of intelligence quotient (IQ) and its perioperative risk factors.

METHODS

In this single-center retrospective cohort study, 31 children were included (14 pCMS). Perioperative risk factors included brainstem invasion, vermis incision, hydrocephalus, tumor size, severity of pCMS, neurological symptoms, mean body temperature (BT) on days 1-4 post surgery, and age at resection. Age-appropriate Wechsler Intelligence tests were assessed at least 2 years after tumor resection.

RESULTS

Mean interval between tumor resection and neuropsychological evaluation was 3.9 years in pCMS and 4 years and 11 months in the no-pCMS group. No significant differences in IQ scores were found between groups. The pCMS group had a clinically relevant difference of 10 points when compared to age norms on verbal IQ (VIQ). Bilateral pyramidal and swallowing problems were risk factors for lower performance. In the overall group, tumor size, younger age at surgery, and raised mean BT were negatively correlated with aspects of IQ.

CONCLUSIONS

We found a clinically significant reduction of VIQ in the pCMS patient group. pCMS patients with a larger tumor size, younger age at surgery, a higher mean BT in the first days after surgery, bilateral pyramidal symptoms, and swallowing problems 10 days post surgery are more at risk for VIQ deficits at long-term.

Neuroimaging Study Investigating the Supraspinal Control of Lower Urinary Tract Function in Man With Orthotopic Ileal Neobladder

Introduction: Recent studies employing functional imaging methodology have revealed reference brain regions of urinary tract function, namely, the midbrain periaqueductal gray matter, thalamus, and cingulate and prefrontal cortices. The orthotopic ileal neobladder is a desirable method for urinary diversion after radical cystectomy, but its supraspinal control remains unknown. We aimed to evaluate brain activity while maintaining urinary urgency and voluntary urinary control in male subjects with ileal orthotopic neobladders by performing functional MRI (fMRI) during a block design experiment. Materials and Methods: Patients were recruited at the Sun Yat-sen Memorial Hospital of the Sun Yat-sen University from October 2017 to May 2019. Two tasks were performed during fMRI scanning: (1) repeated infusion and withdrawal of sterile saline solution into and out of the neobladder to simulate urgency; and (2) repeated contraction of the pelvic floor muscle with a full neobladder to induce inhibition of micturition since the subjects were asked not to urinate. The obtained data were visualized and statistically analyzed. Results: Sixteen subjects were recruited in the study, and data were obtained from 10 subjects: mean age 60.1 years, average postoperative time 20.2 months, and daytime continence rate 100%. The parahippocampus, frontal lobe, vermis, and anterior cingulate cortex were activated with large bladder volumes, and the thalamus and caudate nucleus were deactivated during voluntary urinary control. Conclusion: A complex supraspinal program is involved during ileal orthotopic neobladder control, which is significantly different from that with normal bladders, in which the original intestine visceral volume sensation is preserved.

Fourth ventricle tumors in children: complications and influence of surgical approach

OBJECTIVES

The goal of this study was to characterize the complications and morbidity related to the surgical management of pediatric fourth ventricle tumors.

METHODS

All patients referred to the authors' institution with posterior fossa tumors from 2002 to 2018 inclusive were screened to include only true fourth ventricle tumors. Preoperative imaging and clinical notes were reviewed to extract data on presenting symptoms; surgical episodes, techniques, and adjuncts; tumor histology; and postoperative complications.

RESULTS

Three hundred fifty-four children with posterior fossa tumors were treated during the study period; of these, 185 tumors were in the fourth ventricle, and 167 fourth ventricle tumors with full data sets were included in this analysis. One hundred patients were male (mean age ± SD, 5.98 ± 4.12 years). The most common presenting symptom was vomiting (63.5%). The most common tumor types, in order, were medulloblastoma (94 cases) > pilocytic astrocytoma (30 cases) > ependymoma (30 cases) > choroid plexus neoplasms (5 cases) > atypical teratoid/rhabdoid tumor (4 cases), with 4 miscellaneous lesions. Of the 67.1% of patients who presented with hydrocephalus, 45.5% had an external ventricular drain inserted (66.7% of these prior to tumor surgery, 56.9% frontal); these patients were more likely to undergo ventriculoperitoneal shunt (VPS) placement at a later date (p = 0.00673). Twenty-two had an endoscopic third ventriculostomy, of whom 8 later underwent VPS placement. Overall, 19.7% of patients had a VPS sited during treatment.Across the whole series, the transvermian approach was more frequent than the telovelar approach (64.1% vs 33.0%); however, the telovelar approach was significantly more common in the latter half of the series (p < 0.001). Gross-total resection was achieved in 70.7%. The most common postoperative deficit was cerebellar mutism syndrome (CMS; 28.7%), followed by new weakness (24.0%), cranial neuropathy (18.0%), and new gait abnormality/ataxia (12.6%). Use of intraoperative ultrasonography significantly reduced the incidence of CMS (p = 0.0365). There was no significant difference in the rate of CMS between telovelar or transvermian approaches (p = 0.745), and multivariate logistic regression modeling did not reveal any statistically significant relationships between CMS and surgical approach.

CONCLUSIONS

Surgical management of pediatric fourth ventricle tumors continues to evolve, and resection is increasingly performed through the telovelar route. CMS is enduringly the major postoperative complication in this patient population.

Pediatric posterior fossa tumors outcomes: Experience in a tertiary care center in the Middle East

BACKGROUND

Among all childhood cancers, brain tumors are second only to leukemia in incidence and are the most common solid pediatric tumors. More than 60 % of pediatric brain tumors are infra-tentorial. The first-line treatment for most infra-tentorial tumors in pediatric patients is surgical resection, with the goal of gross-total resection, relief of symptoms and hydrocephalus, and increased survival. The proximity to the fourth ventricle, and therefore, the cerebrospinal fluid (CSF) pathways, predisposes children with posterior fossa tumors to the development of obstructive hydrocephalus and multiple other co-morbidities pre and post-surgery.

OBJECTIVES

This study aims to present our series of pediatric posterior fossa tumor surgeries in the Neurosurgical Department at the American University of Beirut Medical Center(AUBMC) and perform internal quality control for our single-institution consecutive series as one of the largest referral and tertiary care centers in the region. The second purpose of this retrospective study is to weigh the risks of surgery against the presumed advantages and to have specific knowledge about the complication rates, especially those related to the CSF pathway, comparing our results to those in the literature.

METHODS

All pediatric patients (< 18 years of age), referred to our center from different regions in the middle east, and surgically treated for a posterior fossa tumor from June 2006 to June 2018 at the American University of Beirut Medical Center were included. A thorough review of all medical charts was performed to validate all the database records.

RESULTS

The patient sample consisted of 64 patients having a mean age of 6.19 ± 4.42 years and 59.37 % of whom were males. The most common tumor pathology was pilocytic astrocytoma (40.62 %) followed by medulloblastoma (35.93 %) and ependymoma. The most common type of tumor that was seen in patients that developed mutism postoperatively (n = 6, 9.37 %) was medulloblastoma (n = 4, 66.66 %). In this patient sample, 12.28 % (n = 7) of the patients developed hydrocephalus postoperatively.Midline tumors were more associated with the development of mutism(OR = 4.632, p = 0.306) and hydrocephalus (OR = 5.056, p = 0.135) postoperatively, albeit not statistically significantly.The presence of a preoperative shunt was shown to be protective against the development of CSF leak (OR = 0.636, p = 0.767), as none of the patients that came in with CSF diversion developed a CSF leak after their surgery.

CONCLUSION

This study from a single center experience accompanied by a thorough literature review sheds light on the complications frequently encountered after posterior fossa tumor surgery in children. These included transient cerebellar mutism, CSF leak, and hydrocephalus as seen in some of our patients. Our findings highlight the need for prospective studies with well-defined protocols directed at assessing novel ways and approaches to minimize the risk of these complications.

Endoscopic assisted craniotomy for resection of fourth ventricular lesions and confirmation of aqueductal patency via a suboccipital median aperture approach

Adequate exposure to fourth ventricular (4V) lesions located adjacent to the cerebral aqueduct and superior medullary velum often mandates extensive telovelar dissection. We assessed the utility of endoscopic assistance via a median aperture approach during suboccipital resection of 4V lesions. We retrospectively reviewed a series of nine patients who underwent suboccipital resection of a 4V lesion via an endoscopic-assisted median aperture approach from 2011 to 2018. Our series included the following pathology: ependymoma (2), rosette-forming glioneuronal tumors (2), pilocytic astrocytoma (1), metastatic melanoma (1), epidermoid cyst (1), organized hematoma (1), and neurocysticercosis (1). Preoperative symptoms included headache (n = 8, 88.9%), nausea (n = 5, 55.6%), vomiting, dizziness, and gait disturbance (n = 4 each, 44.5%). In four cases, the endoscope was used for the majority of the resection or to resect additional tumor located rostrally in the 4V following maximal microscopic resection. In five patients, it was used to confirm extent of resection and patency of the cerebral aqueduct. Gross total resection was achieved in five patients (55.6%). No postoperative complications were attributed to use of the endoscope for additional resection. No patients required immediate CSF diversion, and one patient underwent ventriculoperitoneal (VP) shunt insertion over one year after initial biopsy/fenestration due to tumor progression. Our series is the first to demonstrate the utility of angled endoscopic assistance via a median aperture approach during microsurgical approaches for a variety of 4V lesions. Confirmation of patency of the cerebral aqueduct may help avoid requirements for CSF diversion.

Cerebellum and micturition: what do we know? A systematic review

Aims

Micturition depends on a complex voluntary and involuntarily neuronal network located at various levels of the nervous system. The mechanism is highly dependent on the hierarchical organization of central nervous system pathways. If the role of the cortex and brainstem centres is well established, the role of other subcortical areas structures, such as the cerebellum is poorly understood. We are interested in discussing the current knowledge on the role of cerebellum in micturition.

Methods

A systematic search is performed in the medical literature, using the PubMed database with the keyword « cerebellum ». The latter is combined with «urination » OR « micturition » OR « urinary bladder ».

Results

Thirty-one articles were selected, focussing on micturition and describing the role of the cerebellum. They were grouped in 6 animal experimental studies, 20 functional brain imaging in micturition and 5 clinical studies.

Conclusions

Although very heterogeneous, experimental and clinical data clearly indicate the cerebellum role in the micturition control. Cerebellum modulates the micturition reflex and participates to the bladder sensory-motor information processing. The cerebellum is involved in the reflex micturition modulation through direct or indirect pathways to major brainstem or forebrain centres.

Quantitative MRI in post-operative paediatric cerebellar mutism syndrome

Post-operative paediatric cerebellar mutism syndrome (pCMS) occurs in around 25% of children undergoing surgery for cerebellar and fourth ventricular tumours. Reversible mutism is the hallmark of a syndrome which comprises severe motor, cognitive and linguistic deficits. Recent evidence from advanced neuroimaging studies has led to the current theoretical understanding of the condition as a form of diaschisis contingent on damage to efferent cerebellar circuitry. Tractography data derived from diffusion MRI studies have shown disruption of the dentato-rubro-thalamo-cortical tract in patients with pCMS, and perfusion studies have indicated widespread supratentorial regions which may give rise to the florid signs and symptoms of pCMS. Given the difficulties in predicting pCMS from standard structural MRI, this review discusses findings from quantitative MRI modalities which have contributed to our understanding of this debilitating syndrome, and considers the goals and challenges which lie ahead in the field.

Cerebellar mutism syndrome: cause and rehabilitation

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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

Neuropsychological consequences of childhood medulloblastoma and possible interventions: A review

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Post-operative paediatric cerebellar mutism syndrome: time to move beyond structural MRI

PURPOSE

To determine the value of structural magnetic resonance imaging (MRI) in predicting post-operative paediatric cerebellar mutism syndrome (pCMS) in children undergoing surgical treatment for medulloblastoma.

METHODS

Retrospective cohort study design. Electronic/paper case note review of all children with medulloblastoma presenting to Great Ormond Street Hospital between 2003 and 2013. The diagnosis of pCMS was established through a scoring system incorporating mutism, ataxia, behavioural disturbance and cranial nerve deficits. MRI scans performed at three time points were assessed by neuroradiologists blinded to the diagnosis of pCMS.

RESULTS

Of 56 children included, 12 (21.4%) developed pCMS as judged by a core symptom of mutism. pCMS was more common in those aged 5 or younger. There was no statistically significant difference in pre-operative distortion or signal change of the dentate or red nuclei or superior cerebellar peduncles (SCPs) between those who did and did not develop pCMS. In both early (median 5 days) and late (median 31 months) post-operative scans, T2-weighted signal change in SCPs was more common in the pCMS group (p = 0.040 and 0.046 respectively). Late scans also showed statistically significant signal change in the dentate nuclei (p = 0.024).

CONCLUSIONS

The development of pCMS could not be linked to any observable changes on pre-operative structural MRI scans. Post-operative T2-weighted signal change in the SCPs and dentate nuclei underlines the role of cerebellar efferent injury in pCMS. Further research using advanced quantitative MRI sequences is warranted given the inability of conventional pre-surgical MRI to predict pCMS.

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.

Cerebellar Mutism Syndrome following Midline Posterior Fossa Tumor Resection in Children: An Institutional Experience

Aim:

Cerebellar mutism (CM) syndrome is a well-known and annoying complication of posterior fossa surgery in the pediatric age group. Risk factors such as the type of tumor, size, involvement of posterior fossa structures and hydrocephalus, and postoperative cerebellar swelling for CM were investigated in this study.

Materials and Methods:

A consecutive series of 33 children with midline posterior fossa tumors were operated at the SMS Medical College and Hospital, Department of Neurosurgery, Jaipur India, between September 2015 and December 2016. Their speech and neuroradiological studies were systematically analyzed both preoperatively and postoperatively.

Results:

CM syndrome (CMS) developed in six children (18.18%) in the early postoperative period. The pre- and post-operative irritability, medulloblastoma histology, maximum size more than 45 mm, involvement of superior cerebellar peduncles, and vermian incision were significant single independent risk factors. In addition, male gender also associated with a higher risk for CMS. The latency for the development of mutism ranged from 1 to 12 days (mean 3.5 days). The speech returned to normal in all patients. All cases with CMS accompanied by cerebellar ataxia.

Conclusion:

The medulloblastoma, irritability, maximum size more than 45 mm, involvement of superior cerebellar peduncles, and vermian incision were significant single independent risk factors for postoperative pediatric CMS. Mutism after posterior fossa tumor resection is also accompanied with ataxia. CM usually has a self-limiting course and a favorable prognosis.

Posterior fossa syndrome-a narrative review

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

Posterior fossa syndrome with a large inflammatory ponto-mesencephalic lesion

Demonstration of a posterior fossa syndrome (PFS) in a 32-year-old male patient with clinically isolated syndrome which subsequently developed into relapsing-remitting Multiple Sclerosis. The patient suffered from double vision, coordination problems including unsteady gait and atactic dysarthria, concentration difficulties, as well as adynamia and impaired decision making. The patient clinically presented a cerebellar and dysexecutive syndrome. Cerebral magnetic resonance imaging (MRI) revealed a contrast enhancing ponto-mesencephalic lesion with a volume of 4.8cm³. Neuropsychological tests showed pronounced executive dysfunctions, reduced visuoconstructive skills, attentional deficits, echolalia, and non-fluent speech production. After cortisone and plasmapheresis, the cerebellar syndrome improved but manual fine motor skills and executive dysfunctions persisted. After three months, symptoms remitted except for a slight gait imbalance. After six months, neuropsychological tests were normal except for a moderate attention deficit. MRI revealed a clear regression of the ponto-mesencephalic lesion to a volume of 2.4cm³ without contrast enhancement. This case report intends to provide an overview of the symptomatology and etiology of PFS and offers new insights into its pathomechanism demonstrating a pontine disconnection syndrome caused by a large demyelinating plaque.

Longitudinal cerebellar diffusion tensor imaging changes in posterior fossa syndrome

Posterior fossa syndrome is a severe transient loss of language that frequently complicates resection of tumors of the cerebellum. The associated pathophysiology and relevant anatomy to this language deficit remains controversial. We performed a retrospective analysis of all cerebellar tumor resections at Seattle Children's Hospital from 2010 to 2015. Diffusion tensor imaging was performed on each of the patients as part of their clinical scan. Patients included in the study were divided into groups based on language functioning following resection: intact (N = 19), mild deficit (N = 19), and posterior fossa syndrome (N = 9). Patients with posterior fossa syndrome showed white matter changes evidenced by reductions in fractional anisotropy in the left and right superior cerebellar peduncle following resection, and these changes were still evident 1-year after surgery. These changes were greater in the superior cerebellar peduncle than elsewhere in the cerebellum. Prior to surgery, posterior fossa patients did not show changes in fractional anisotropy however differences were observed in mean and radial diffusivity measures in comparison to other groups which may provide a radiographic marker of those at greatest risk of developing post-operative language loss.

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.

Identifying quantitative imaging features of posterior fossa syndrome in longitudinal MRI

Up to 25% of children who undergo brain tumor resection surgery in the posterior fossa develop posterior fossa syndrome (PFS). This syndrome is characterized by mutism and disturbance in speech. Our hypothesis is that there is a correlation between PFS and the occurrence of hypertrophic olivary degeneration (HOD) in structures within the posterior fossa, known as the inferior olivary nuclei (ION). HOD is exhibited as an increase in size and intensity of the ION on an MR image. Longitudinal MRI datasets of 28 patients were acquired consisting of pre-, intra-, and postoperative scans. A semiautomated segmentation process was used to segment the ION on each MR image. A full set of imaging features describing the first- and second-order statistics and size of the ION were extracted for each image. Feature selection techniques were used to identify the most relevant features among the MRI features, demographics, and data based on neuroradiological assessment. A support vector machine was used to analyze the discriminative features selected by a generative k-nearest neighbor algorithm. The results indicate the presence of hyperintensity in the left ION as the most diagnostically relevant feature, providing a statistically significant improvement in the classification of patients ([Formula: see text]) when using this feature alone.

Posterior fossa syndrome following brain tumour resection: review of pathophysiology and a new hypothesis on its pathogenesis

INTRODUCTION

Posterior fossa syndrome (PFS), also known as cerebellar mutism syndrome (CMS), is a severe complication affecting children following surgery for posterior fossa brain tumours. Its incidence varies between 8 and 31 %, and its exact pathogenesis remains unclear. In this article, we aim to review the existing theories on its pathogenesis and propose a new hypothesis.

DISCUSSION

There is varying level of evidence on existing theories on the pathogenesis of PFS following surgery. These include cerebellar perfusion deficits due to vasospasm, oedema or axonal injury due to direct surgical injury and neuronal dysfunction. There is emerging evidence that interruption of the dentato-thalamo-cortical (DTC) pathway is responsible for PFS. Based on our experience with intraoperative MRI, radiological and pathological evidence on heat-related brain injury, we propose a new hypothesis implicating thermal injury resulting from the use of the Cavitron Ultrasonic Aspirator (CUSA) as an important mechanism in the pathogenesis of PFS.

CONCLUSION

The pathogenesis of PFS is likely to be multifactorial with direct injury from surgery being a major factor. We believe that thermal injury in addition to mechanical injury to the proximal segment of the DTC plays an important role in the pathogenesis of PFS and should be considered in future research related to the aetiology, prevention and management of PFS.

Ionizing Radiation Perturbs Cell Cycle Progression of Neural Precursors in the Subventricular Zone Without Affecting Their Long-Term Self-Renewal

Damage to normal human brain cells from exposure to ionizing radiation may occur during the course of radiotherapy or from accidental exposure. Delayed effects may complicate the immediate effects resulting in neurodegeneration and cognitive decline. We examined cellular and molecular changes associated with exposure of neural stem/progenitor cells (NSPs) to ¹³⁷Cs γ-ray doses in the range of 0 to 8 Gy. Subventricular zone NSPs isolated from newborn mouse pups were analyzed for proliferation, self-renewal, and differentiation, shortly after irradiation. Strikingly, there was no apparent increase in the fraction of dying cells after irradiation, and the number of single cells that formed neurospheres showed no significant change from control. Upon differentiation, irradiated neural precursors did not differ in their ability to generate neurons, astrocytes, and oligodendrocytes. By contrast, progression of NSPs through the cell cycle decreased dramatically after exposure to 8 Gy (p < .001). Mice at postnatal day 10 were exposed to 8 Gy of γ rays delivered to the whole body and NSPs of the subventricular zone were analyzed using a four-color flow cytometry panel combined with ethynyl deoxyuridine incorporation. Similar flow cytometric analyses were performed on NSPs cultured as neurospheres. These studies revealed that neither the percentage of neural stem cells nor their proliferation was affected. By contrast, γ-irradiation decreased the proliferation of two classes of multipotent cells and increased the proliferation of a specific glial-restricted precursor. Altogether, these results support the conclusion that primitive neural precursors are radioresistant, but their proliferation is slowed down as a consequence of γ-ray exposure.

Diffusion abnormalities on intraoperative magnetic resonance imaging as an early predictor for the risk of posterior fossa syndrome

BACKGROUND

Posterior fossa syndrome (PFS) is an important complication of posterior fossa surgery in children. The pathophysiology of this condition remains unclear, but there is evidence implicating surgical injury of the proximal efferent cerebellar pathway (pECP) and the cerebellar vermis to PFS. We aimed to evaluate if diffusion abnormalities involving these structures on the final intraoperative MRI can predict the development of PFS.

METHODS

Diffusion-weighted imaging from 31 posterior fossa resections were anonymized and evaluated for abnormalities involving the dentate nucleus, superior cerebellar peduncle, and the mesencephalic tegmentum forming the pECP, vermis, and middle cerebellar peduncle. The case notes were independently evaluated for evidence of PFS.

RESULTS

The diffusion imaging in 28 cases was of optimal quality for evaluation. Diffusion abnormalities were identified in 10 cases, 7 of which involved the pECP. Retrospective evaluation revealed evidence of PFS in 6 cases. There was a significant association between abnormalities involving pECP structures (P = .001) and development of PFS. Bilateral involvement of pECP (P = .006) was a highly specific risk factor for predicting the development of PFS. Diffusion abnormality of the inferior vermis was significantly associated with PFS (P = .001) but may not represent a risk factor in isolation.

CONCLUSION

This study demonstrates the feasibility of identifying children at risk for developing PFS at the earliest stage post tumor resection and thus adds to the growing evidence base on its pathophysiology.

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.

Cerebellar Mutism Syndrome After Posterior Fossa Surgery: A Report of Two Cases of Pilocytic Astrocytoma

Cerebellar mutism is a type of syndrome including decreased speech, hypotonia, ataxia and emotional instability which occurs after posterior fossa surgery. It has been first reported by Rekate et al. and Yonemasu in 1985. It is well known that long tract signs and lower cranial nerve involvement are not seen with this syndrome and understanding is preserved. However, the pathophysiology of cerebellar mutism has not been well clarified yet. It is mainly seen in patients with medulloblastoma and brainstem involvement. In this report, we present two extraordinary cases of cerebellar mutism after posterior fossa surgery. They were considered extraordinary because their hystopathological analysis results yielded pilocytic astrocytoma which is out of the predefined risk factors.

Cerebellar mutism

Mutism of cerebellar origin is a well-described clinical entity that complicates operations for posterior fossa tumors, especially in children. This review focuses on the current understanding of principal pathophysiological aspects and risk factors, epidemiology, clinical characteristics, treatment strategies, and outcome considerations. The PubMed database was searched using the term cerebellar mutism and relevant definitions to identify publications in the English-language literature. Pertinent publications were selected from the reference lists of the previously identified articles. Over the last few years an increasing number of prospective studies and reviews have provided valuable information regarding the cerebellar mutism syndrome. Importantly, the clarification of principal terminology that surrounds the wide clinical spectrum of the syndrome results in more focused research and more effective identification of this entity. In children who undergo surgery for medulloblastoma the incidence of cerebellar mutism syndrome was reported to be 24%, and significant risk factors so far are brainstem involvement and midline location of the tumor. The dentate-thalamo-cortical tracts and lesions that affect their integrity are considered significant pathophysiological issues, especially the tract that originates in the right cerebellar hemisphere. Moderate and severe forms of the cerebellar mutism syndrome are the most frequent types during the initial presentation, and the overall neurocognitive outcome is not as favorable as thought in the earlier publications. Advanced neuroimaging techniques could contribute to identification of high-risk patients preoperatively and allow for more effective surgical planning that should focus on maximal tumor resection with minimal risk to important neural structures. Properly designed multicenter trials are needed to provide stronger evidence regarding effective prevention of cerebellar mutism and the best therapeutic approaches for such patients with a combination of pharmacological agents and multidisciplinary speech and behavior augmentation.

Diffusion tensor imaging of the superior cerebellar peduncle identifies patients with posterior fossa syndrome

INTRODUCTION

Posterior fossa tumors are the most common brain tumor of children. Aggressive resection correlates with long-term survival. A high incidence of posterior fossa syndrome (PFS), impairing the quality of life in many survivors, has been attributed to damage to bilateral dentate nucleus or to cerebellar output pathways. Using diffusion tensor imaging (DTI), we examined the involvement of the dentothalamic tracts, specifically the superior cerebellar peduncle (SCP), in patients with posterior fossa tumors and the association with PFS.

METHODS

DTI studies were performed postoperatively in patients with midline (n = 12), lateral cerebellar tumors (n = 4), and controls. The location and visibility of the SCP were determined. The postoperative course was recorded, especially with regard to PFS, cranial nerve deficits, and oculomotor function.

RESULTS

The SCP travels immediately adjacent to the lateral wall of the fourth ventricle and just medial to the middle cerebellar peduncle. Patients with midline tumors that still had observable SCP did not develop posterior fossa syndrome (N = 7). SCPs were absent, on either preoperative (N = 1, no postoperative study available) or postoperative studies (N = 4), in the five patients who developed PFS. Oculomotor deficits of tracking were observed in patients independent of PFS or SCP involvement.

CONCLUSION

PFS can occur with bilateral injury to the outflow from dentate nuclei. In children with PFS, this may occur due to bilateral injury to the superior cerebellar peduncle. These tracts sit immediately adjacent to the wall of the ventricle and are highly vulnerable when an aggressive resection for these tumors is performed.

Splitting of the cerebellar vermis in juvenile rats--effects on social behavior, vocalization and motor activity

Radical resection of malignant midline tumors of the posterior fossa in childhood followed by adjuvant therapies like chemotherapy or radiotherapy often leads to longterm survival and even healing of such patients. Therefore, quality of life becomes particular important. Postoperative neurological deficits, such as cerebellar mutism and ataxia have been attributed to splitting of the cerebellar vermis to remove these tumors. Here, we tested the effect of vermian splitting in juvenile rats on social behavior, vocalization and motor activity. Juvenile male Sprague Dawley rats, aged 23 days, underwent vermian splitting under general anesthesia after medial suboccipital craniotomy (lesioned group, n=16). In sham-lesioned rats, only craniotomy was performed and the dura was opened with release of cerebrospinal fluid (n=16). Naïve rats served as controls (n=14). All groups were tested on day 0 (before surgery), and on days 1-4 and 7 after surgery for locomotor activity, motor coordination, social behavior, and ultrasound vocalization during social interaction. Finally, splitting of the vermis was histologically verified. Social interaction was reduced for two days after surgery in lesioned rats compared to sham-lesioned rats and controls. Vocalization was decreased for one day compared to controls. Locomotor activity was disturbed for several days after surgery in both lesioned and sham-lesioned rats as compared to controls. Deficient social behavior and vocalization after surgery are related to vermian splitting in juvenile rats. These results indicate that similar to the human context vermian splitting can reduce communicative drive in the early postsurgical phase.

Fronto-cerebellar fiber tractography in pediatric patients following posterior fossa tumor surgery

OBJECTIVE

Fronto-cerebellar association fibers (FCF) are involved in neurocognitive regulatory circuitry. This may also be relevant for cerebellar mutism syndrome (CMS) as a complication following posterior fossa tumor removal in children. In the present study, we investigated FCF by diffusion tensor imaging in affected children and controls.

METHODS

Diffusion-weighted MR imaging at 3 T (GE) allowed tractography of FCF using a fiber tracking algorithm software (Brainlab 2.6) in 29 patients after posterior fossa tumor removal and in 10 healthy peers. Fiber tract volumes were assessed and fiber signals were evaluated in a semiquantitative manner along the anatomical course.

RESULTS

Volumes of FCF revealed significant diminished values in pediatric patients with symptoms of CMS (19.3 ± 11.7 cm(3)) when compared with patients without symptoms of CMS (26.9 ± 11.9 cm(3)) and with healthy peers (36.5 ± 13.82 cm(3)). In medulloblastoma patients, the volume of FCF was also significantly reduced in patients with symptoms of CMS despite having the same antitumor therapy. In semiquantitative analysis of the fiber tract signals, differences were observed in the superior cerebellar peduncles and midline cerebellar structures in patients with symptoms of CMS.

CONCLUSION

Using DTI, which allows the visualization of fronto-cerebellar fiber tracts, lower FCF tract volumes and diminished fiber signal intensities at the level of the superior cerebellar peduncles and in midline cerebellar structures were identified in patients with postoperative symptoms of CMS. Our study refers to the role of a neural circuitry between frontal lobes and the cerebellum being involved in neurocognitive impairment after posterior fossa tumor treatment in children.

Clinical and neuroanatomical predictors of cerebellar mutism syndrome

Cerebellar mutism syndrome (CMS) is an important medical challenge in the management of pediatric posterior fossa brain tumors, because it occurs in a subset of children following tumor resection. A definitive clinical profile and neuroanatomical substrate associated with CMS remains unclear. We investigated the relationship between presurgical and clinical variables and the incidence of CMS, along with diffusion tensor imaging, to characterize the integrity of cerebello-thalamo-cerebral white matter pathways. Seventeen children with posterior fossa tumors and CMS, 34 children with posterior fossa tumors without CMS, and 28 healthy children were enrolled in this study. Bilateral cerebello-thalamo-cerebral pathways were delineated and segmented into anatomical regions. Mean integrity measures for each region were compared among children with CMS, children without CMS, and healthy children. Left-handedness, medulloblastoma histology, and larger tumor size distinguished between patients with CMS and patients without CMS (P < .04). Right cerebellar white matter within the cerebello-thalamo-cerebral pathway was compromised in children with CMS relative to children without CMS and healthy children (P < .02). We provide a potential schema for CMS risk among children treated for posterior fossa tumors. Left-handed children treated for medulloblastoma may be the most at risk for CMS, and unilateral, localized damage within the cerebello-thalamo-cerebral pathway at the level of the right cerebellum is implicated in the presentation of CMS. This disruption in communication between the right cerebellum and left frontal cortex may contribute to speech-language problems observed in children with CMS. Our findings may be relevant for surgical planning and speech-language therapy to mitigate symptoms of CMS.

Auditory-perceptual speech analysis in children with cerebellar tumours: a long-term follow-up study

Mutism and Subsequent Dysarthria (MSD) and the Posterior Fossa Syndrome (PFS) have become well-recognized clinical entities which may develop after resection of cerebellar tumours. However, speech characteristics following a period of mutism have not been documented in much detail. This study carried out a perceptual speech analysis in 24 children and adolescents (of whom 12 became mute in the immediate postoperative phase) 1-12.2 years after cerebellar tumour resection. The most prominent speech deficits in this study were distorted vowels, slow rate, voice tremor, and monopitch. Factors influencing long-term speech disturbances are presence or absence of postoperative PFS, the localisation of the surgical lesion and the type of adjuvant treatment. Long-term speech deficits may be present up to 12 years post-surgery. The speech deficits found in children and adolescents with cerebellar lesions following cerebellar tumour surgery do not necessarily resemble adult speech characteristics of ataxic dysarthria.

The cerebellum and neuropsychiatric disorders

Relative to non-human primates, in humans the cerebellum, and prefrontal cortex are brain regions which have undergone major evolutionary changes. In recent decades, progress in molecular biology and advances in the development of functional neuroimaging analysis have shown that the evolution of the human cerebellum was accompanied by the acquisition of more functions than were previously deduced from human post-mortem studies and animal experimentation. These new cerebellar functions included the control of attention and other cognitive functions, emotions and mood, and social behavior, which were all thought to represent cortical functions. The importance of this new view of cerebellar physiology has been confirmed by the frequency of neuropsychiatric disorders in individuals with cerebellar abnormalities. The information collected in this review emphasizes the importance of cerebellar studies in establishing the physiological substrate of mental diseases.

Speech Pathology Services to Children With Cancer and Nonmalignant Hematological Disorders

Children with cancer and nonmalignant hematological disorders may require speech pathology (SP) support; however, limited evidence is available describing prevalence and severity of swallowing/feeding and communication impairments in this population. A retrospective chart review of 70 children referred to SP at the newly formed Queensland Children’s Cancer Centre was conducted to describe the prevalence and severity of swallowing/feeding and communication dysfunction, and the association between impairment, oncology and hematology diagnosis, and service utilization (time and occasions of service). Swallowing/feeding disorders were the most commonly observed impairments at initial assessment (58.6%). Children with central nervous system tumors ( P = .03) and nonmalignant hematological disorder ( P = .03) had significantly higher rates of feeding impairment than other oncology and hematology diagnostic groups. Children with central nervous system tumors had the highest rates of oral phase ( P = .01) and pharyngeal phase ( P = .01) dysphagia (swallowing disorder). No significant difference was found between diagnostic groups for intensity of SP service delivery. Prospective research is required to examine prevalence and severity of disorders, and service utilization in a more established clinic, and to investigate interactions between cancer treatment and swallowing/feeding and communication dysfunction.

Short-term neurological outcome of children after surgery for brain tumors: incidence and characteristics in a pediatric intensive care unit

PURPOSE

The main treatment for majority of pediatric brain tumors relies on surgery. In postoperative period, patients require monitoring in a pediatric intensive care unit (PICU). In this study, we analyzed the incidence of postoperative neurological complications and the outcome of neurological impairment in individual patients.

PATIENTS AND METHODS

Our retrospective single-center study concerned all patients who were admitted to the PICU of the University Hospital of Angers between 2002 and 2008, after brain tumor resection. Population, perioperative data, and outcome through the stay in PICU have been analyzed.

RESULTS

We reported 117 neurosurgical procedures. Majority of children (85.3%) were affected by neurological deficit before surgery: cranial nerve palsy and cerebellar syndrome were the most frequent impairment. In the first 2 days, neurological symptoms improved for 27 patients (23.7%), especially in children with preoperative cerebellar syndrome, convulsions, or endocrine disorders. Mean length of stay in PICU was correlated with the severity of neurological impairment (p = 0.006). Five children presented a transient mutism after surgery for infratentorial tumors (n = 5/54, 9.2%). Eight spontaneous cerebral spinal fluid leaks occurred precociously after surgery, and neurological infections complicated half of them. Neurological infections occurred in 12 patients (ten meningitis, one ventriculitis, and one brain abscess). One patient died after surgery.

CONCLUSIONS

All these complications and their risk factors have to be systematically searched for in order to decrease postoperative morbidity of brain tumors in children. They justify neurosurgeons and anesthesiologists specialized in these pathologies.

Cerebellar mutism: review of the literature

PURPOSE

Cerebellar mutism is a common complication of posterior fossa surgery in children. This article reviews current status with respect to incidence, anatomical substrate, pathophysiology, risk factors, surgical considerations, treatment options, prognosis and prevention.

METHODS

We reviewed all peer-reviewed English publications on cerebellar mutism between the years of 1985 and 2009. The majority were found by searching for ‘cerebellar mutism’ and ‘posterior fossa syndrome’ in PubMed. Additional cases were identified by cross-checking reference lists.

RESULTS

The overall incidence of postoperative cerebellar mutism is 11-29%, and patients with medulloblastomas and/or brainstem invasion are at a greater risk of developing it than those with other kinds of tumors and/or without brainstem invasion. Permanent sequelae in the form of both motor- and non-motor-related speech deficits are common, especially when the right cerebellar hemisphere is involved. The mutism is caused by bilateral pertubation of the dentate nuclei and their efferent pathways, which emphasizes the need to explore surgical methods that spare these structures. The pathophysiological mechanisms of delayed onset and resolution of cerebellar mutism are not clear, but axonal damage, edema, perfusional defects and metabolic disturbances may be involved.

CONCLUSION

The incidence of cerebellar mutism is well documented in children with medulloblastoma, but precise figures for those with astrocytoma and ependymoma are lacking. Further anatomical, functional imaging and neuropsychological studies are needed to clarify the pathophysiological mechanisms in order to define preventive measures during surgery. Randomized, controlled trials of the effects of different medication and post-operative speech therapy are necessary for improving treatment.

Posterior fossa syndrome after posterior fossa surgery in children with brain tumors

BACKGROUND

Posterior fossa syndrome (PFS) is defined as the temporary and complete loss of speech after posterior fossa surgery. The goal of this study was to identify incidence and risk factors for PFS and to determine accompanying neurobehavioral and psychologic problems.

PROCEDURE

Between May 2007 and April 2009, children with brain tumors having posterior fossa surgery were evaluated neurologically and psychologically in preoperative and postoperative period.

RESULTS

PFS developed in 9 patients among 36 (25%) included in the study. Mutism continued for 120 days in one patient. Histopathological diagnosis (P = 0.05), location of the tumor (P = 0.05) and socioeconomic level of the family (P = 0.06) gave the significant results in relation with the PFS by univariate analyses. In multivariate analysis the risk of developing PFS was found 7.2 times higher in patients with medulloblastoma, 6.7 times higher in tumors located at the midline, 5.7 times higher in families with low socioecnomic level. Intelligence quotients of the patients in PFS and other group (P = 0.85) with Wechsler Intelligence Scale for Children and the results of the Denver II Developmental Screening Test were not significant statistically (P = 0.5).

CONCLUSION

The diagnosis of medulloblastoma, midline location of the tumor and low socioeconomic level of the families are important risk factors for the development of PFS. These findings support the hypothesis that temporary ischemia and edema due to retracted and manipulated dentate nuclei and superior cerebellar pedincles may be the cause of mutism.

Correlation between pre- or postoperative MRI findings and cerebellar sequelae in patients with medulloblastomas

INTRODUCTION

Immediate and delayed cerebellar dysfunction may be expected after surgical resection of a medulloblastoma. We investigated whether pre-operative and delayed post-operative MRI may correlate with such sequelae.

MATERIAL AND METHODS

The data of 31 patients in continuous complete remission after removal of medulloblastoma, irradiation and chemotherapy, were retrospectively reviewed. Magnetic Resonance Imaging (MRI) was analyzed for the following items: preoperative MRI (ratio of the surface of the tumor/posterior fossa, presence of ventricular dilatation or tonsilar hernia, involvement of the dentate nucleus) and delayed post-operative MRI (amount of cerebellar parenchyma removed, degree of cerebellar atrophy, presence of T1 hypointense regions in remaining cerebellar area and removal of region containing dentate nucleus). These data were correlated with immediate and long-term cerebellar syndrome and daily life repercussions.

RESULTS

On preoperative MRI, the ratio of the surface of the tumor/posterior fossa and the presence of tonsilar hernia were significantly correlated with long-term sequelae on speech (respectively P = 0.027 and P = 0.05). Initial supratentorial ventricular dilatation was correlated with ability to sustain adequately daily tasks (P = 0.002). On delayed MRI, cerebellar atrophy was inversely correlated with ability to sustain daily tasks (P = 0.002). Hypointense T1 territory in remaining cerebellar parenchyma significantly correlated with immediate post-operative cerebellar syndrome (P = 0.01) and showed a tendency for post-operative mutism (P = 0.087) but was not correlated with any long-term sequelae.

CONCLUSION

Increased cranial pressure on initial MRI and cerebellar atrophy detected on subsequent MRI studies correlated with immediate and long-term cerebellar sequelae.

The contribution of the cerebellum to cognition in Spinocerebellar Ataxia Type 6

This study sought evidence for a specific cerebellar contribution to cognition by characterising the cognitive phenotype of Spinocerebellar Ataxia Type 6 (SCA-6); an autosomal dominant genetic disease which causes a highly specific late-onset cerebellar degeneration. A comprehensive neuropsychological assessment was administered to 27 patients with genetically confirmed SCA-6. General intellectual ability, memory and executive function were examined using internationally standardised tests (Wechsler Adult Intelligence Scale-III, Wechsler Memory Scale-III, Delis and Kaplan Executive Function System, Brixton Spatial Anticipation test). The patient group showed no evidence of intellectual or memory decline. However, tests of executive function involving skills of cognitive flexibility, inhibition of response and verbal reasoning and abstraction demonstrated significant impairment at the group level with large effect sizes. The results demonstrate an executive deficit due to SCA-6 that can be conceptualised as parallel to the motor difficulties suffered by these patients: the data support a role for the cerebellum in the regulation and coordination of cognitive, as well as motor processes that is relevant to individual performance.

Neurocognitive outcome 12 months following cerebellar mutism syndrome in pediatric patients with medulloblastoma

The aim is to prospectively assess early neurocognitive outcome of children who developed cerebellar mutism syndrome (CMS) following surgical resection of a posterior fossa embryonal tumor, compared with carefully matched control patients. Children who were enrolled on an ongoing IRB-approved protocol for treatment of embryonal tumors, were diagnosed with postoperative CMS, and had completed prospectively planned neuropsychological evaluation at 12 months postdiagnosis were considered eligible. The cognitive outcomes of these patients were examined in comparison to patients without CMS from the same treatment protocol and matched with regard to primary diagnosis, age at diagnosis, and risk/corresponding treatment (n = 22 pairs). Seventeen were also matched according to gender, and 14 were also matched according to race. High-risk patients received 36-39.6 Gy CSI and 3D conformal boost to the primary site to 55.8-59.4 Gy. Average-risk patients received 23.4 Gy CSI and 3D conformal boost to the primary site to 55.8 Gy. Significant group differences were found on multiple cognitive outcomes. While the matched control patients exhibited performance in the average range, patients who developed CMS postsurgery were found to have significantly lower performance in processing speed, attention, working memory, executive processes, cognitive efficiency, reading, spelling, and math. Patients treated for medulloblastoma who experience postoperative CMS show an increased risk for neurocognitive impairment, evident as early as 12 months following diagnosis. This study highlights the need for careful follow-up with neuropsychological evaluation and for obtaining critical support for patients and their families.

Rhesus macaque as an animal model for posterior fossa syndrome following tumor resection

BACKGROUND/AIMS

Posterior fossa tumors are the most common brain tumors in children. Surgeons usually remove these tumors via a midline incision through the posterior vermis of the cerebellum. Though often effective, this surgery causes hypotonia, ataxia, oculomotor deficits, transient mutism, difficulty in swallowing and nausea. To date, there is no animal model that mimics these complications. We found that the rhesus macaque is a good model for the consequences of this surgery.

METHODS

We made a midline incision through the cerebellar vermis of one monkey to mimic the posterior fossa surgery. Then, we closely monitored the monkey for deficits following the surgery.

RESULTS

In the first few days, the monkey exhibited nausea, hypotonia, ataxia, difficulty in swallowing and an absence of vocalization. At 28 days, we recorded eye movements and found severe deficits in the accuracy of rapid eye movements and smooth pursuit of a target. Additionally, the animal had trouble fixating and a rightward-beating nystagmus. Oculomotor signs persisted until we sacrificed the animal 99 days after surgery, but the other effects resolved by 37 days.

CONCLUSION

Our surgery in a monkey caused the same postsurgical signs observed in humans. We expect to use this model to improve the posterior fossa surgery methods.

Postoperative cerebellar mutism syndrome following treatment of medulloblastoma: neuroradiographic features and origin

OBJECT

The origin and long-term outcome of cerebellar mutism syndrome (CMS), a postoperative syndrome of diminished speech, hypotonia, and ataxia that affects approximately 25% of patients with medulloblastoma, is poorly elucidated. The current study was undertaken to determine factors associated with development of CMS, a means to determine its severity or cause, and outcomes of patients with this syndrome.

METHODS

The study included 28 children with medulloblastoma who either underwent an operation or were referred to the authors' institution soon after surgery. Eleven (39%) of these children had CMS. The preoperative, immediate postoperative, and 1-year postoperative MR images were reviewed by a neuroradiologist blinded to diagnosis of CMS. The severity of mutism and neurological and neurocognitive outcomes were examined.

RESULTS

Preoperative MR images showed no differences in tumor size, hydrocephalus, or peritumoral edema in patients with and without CMS. An association with brainstem invasion was significant (p < 0.05), and there was a trend toward an association with involvement of the cerebellomedullary angle (p = 0.08). Images obtained immediately postoperatively showed cerebellar edema in 92% of all patients; there were trends for more middle and superior cerebellar peduncle edema in patients with CMS (p = 0.05 and 0.07, respectively). At 1 year postoperatively, patients with CMS showed more moderate to severe atrophy/gliosis of total cerebellum (p < 0.01), vermis (p < 0.01), and brainstem (p < 0.05). Mean IQ was 16 points lower in patients with CMS (IQ = 84.2 +/- 15.8) compared with those without CMS (IQ = 100.4 +/- 17.4), with a trend toward significance (p = 0.07).

CONCLUSIONS

This study demonstrates that CMS is associated with postoperative damage to the cerebellum and brainstem, damage not predicted by immediate postoperative MR imaging, and with poorer associated functional outcome.

Surgical considerations in fourth ventricular ependymoma with the transcerebellomedullary fissure approach in focus

INTRODUCTION

Within the existing consensus for the best management of pediatric infratentorial ependymomas (PIE), surgery is the most important stage, where complete removal should be the perfect aim, before complementing it with chemo- or radiotherapy. That, however, remains a challenge even for the most skillful surgeons because of the vicinity of important brainstem and cranial nerve structures involved and is particularly difficult in lateral extensions.

MATERIALS AND METHODS

The paper analyzes the current trends of PIE treatment with emphasis on resection difficulties created by lateral extensions. Anatomical analysis and clinical application of the cerebellomedullary fissure dissection has created specific approaches, providing safe route to the lateral recess and cerebellopontine area by dividing safely tenia and tonsils and biventer lobes retraction.

DISCUSSION AND CONCLUSION

Bilateral and unilateral approaches have been developed. This approach prevents the damage of transvermian access and the resulting cerebellar mutism in some cases. Indications, technique and benefits of transcerebellomedullary fissure types of approaches are discussed.

Incidence, risks, and sequelae of posterior fossa syndrome in pediatric medulloblastoma

PURPOSE

To investigate the incidence, risks, severity, and sequelae of posterior fossa syndrome (PFS) in children with medulloblastoma.

METHODS AND MATERIALS

Between 1990 and 2007, 63 children with medulloblastoma at Emory University and Children's Healthcare of Atlanta were treated with craniectomy followed by radiation. Fifty-one patients were assigned to a standard-risk group, and 12 patients were assigned to a high-risk group. Five patients had <1.5-cm(2) residual tumor, 4 had >or=1.5-cm(2) residual tumor, and the remainder had no residual tumor. Eleven patients had disseminated disease. Patients received craniospinal irradiation at a typical dose of 23.4 Gy or 36 Gy for standard- or high-risk disease, respectively. The posterior fossa was given a total dose of 54 or 55.8 Gy. Nearly all patients received chemotherapy following cooperative group protocols.

RESULTS

Median follow-up was 7 years. PFS developed in 18 patients (29%). On univariate analysis, brainstem invasion, midline tumor location, younger age, and the absence of radiographic residual tumor were found to be predictors of PFS; the last two variables remained significant on multivariate analysis. From 1990 to 2000 and from 2001 to 2007, the proportions of patients with no radiographic residual tumor were 77% and 94%, respectively. During the same eras, the proportions of patients with PFS were 17% and 39%. Only 4 patients had complete recovery at last follow-up.

CONCLUSIONS

The incidence of PFS increased in the latter study period and is proportional to more aggressive surgery. Children with midline tumors exhibiting brainstem invasion are at increased risk. With the increased incidence of PFS and the permanent morbidity in many patients, the risks and benefits of complete tumor removal in all patients need to be reexamined.

The cerebellar mutism syndrome and its relation to cerebellar cognitive function and the cerebellar cognitive affective disorder

The postoperative cerebellar mutism syndrome (CMS), consisting of diminished speech output, hypotonia, ataxia, and emotional lability, occurs after surgery in up to 25% of patients with medulloblastoma and occasionally after removal of other posterior fossa tumors. Although the mutism is transient, speech rarely normalizes and the syndrome is associated with long-term adverse neurological, cognitive, and psychological sequelae. The clinical, neuroradiographic, and neuropsychological findings associated with CMS as well as possible mechanisms of injury are reviewed. Theories about the pathophysiology of CMS have evolved along with our understanding of the cerebellum as an important structure in the distributive neurocircuitry underlying complex speech, cognition, and behavior. CMS shares many similarities with the cerebellar cognitive affective syndrome, more commonly described in adults and consisting of disturbances of executive function, visuospatial skills, nonmotor language, and affect regulation. Future directions include more thorough neuropsychological characterization, functional and diffusion tensor imaging studies, and investigations into the underlying differences that may make some patients more vulnerable to CMS.