Complication Of Posterior Fossa Surgery Research Articles

Outcomes and Complications of Posterior Fossa Surgery in Sitting Versus Park-Bench Positions

Background/Objectives: Patient positioning during surgery can influence intra- and postoperative complications. Therefore, we assessed the impact of the sitting and park-bench positions on anesthetic parameters and complications in neurosurgical patients. Methods and Patients: For this retrospective study, 314 adults who underwent neurosurgical procedures for posterior fossa pathologies were divided into two groups: sitting (n = 231) and park-bench (n = 83). The following data were collected, monitored, recorded, and compared: age, sex, tumor type, surgical approach, cardiovascular and respiratory complications, and postoperative surgical complications. The association of hypotension with the position was further investigated through multivariate logistic regression models by adjusting for CO2 decrease, desaturation, and documented gas embolism. Results: The average age was significantly lower in the sitting group (55 years, interquartile range (IQR) = 43–63; female proportion = 59.74%) than in the park-bench group (62 years, IQR = 45–74; female proportion = 57.83%) (p < 0.001). Cerebellopontine angle tumors were detected in 37.23% of the patients who underwent an operation in the sitting position and in 7.26% who underwent an operation in the park-bench position (p < 0.001). Patients in the sitting position had significantly greater anesthetic complication (91.77% vs. 71.08%, p < 0.001), hypotension (61.9% vs. 16.87%), and >2 mmHg CO2 decrease (35.06% vs. 15.66%, p < 0.001) incidences. Hypoxemia and death occurred more frequently in the park-bench group (8.43% vs. 1.73% and 6.03% vs. 1.3%, respectively). Conclusions: Compared with the park-bench position, the sitting position was associated with a greater specific anesthetic complication incidence and lower postoperative mortality rate, indicating a need for careful risk-benefit assessment when selecting each individual patient’s surgical position.

IMG-01. LONGITUDINAL SIGNAL CHANGES IN THE DENTATE AND INFERIOR OLIVARY NUCLEI IN PATIENTS WITH CEREBELLAR MUTISM SYNDROME

Abstract BACKGROUND Cerebellar mutism syndrome (CMS) is a complication of posterior fossa surgery with an acute impairment in speech, and long-term neurocognitive deficits. Lesion mapping studies suggest the cognitive symptoms are associated with dentatorubrolivary damage1. We hypothesize that CMS patients will demonstrate more longitudinal MRI signal abnormalities in the dentate and inferior olivary nuclei as compared to non-CMS patients. METHODS MRI brains on 40 pediatric medulloblastoma patients between 2013-2015 were retrospectively reviewed by a neuroradiologist blinded to the diagnosis at pre-operative and immediate, 6-month, 12 month and most recent post-operative time points. The dentate and inferior olivary nuclei were scored for restricted diffusion, T1 and T2 hypo-and hyperintensity. A linear regression with different scores on CMS status (YES vs NO) was applied, after adjusting for age. RESULTS In the dentate nuclei, there was significantly higher T2 hypointensity in the CMS group on immediate (difference is 0.4084, p=0.0467) and most recent (difference is 0.7190, p=0.0386) post-operative MRIs. The CMS group had significantly higher T1 hyperintensity on the 1-year (difference is 0.9254, p=0.0108) and most recent (difference is 1.3291, p<0.001) post-operative MRIs. In the inferior olivary nuclei, there was significantly higher T2 hyperintensity on the 6-month (difference is 0.71, p=0.0045) and 1-year (difference is 0.6356, p=0.0162) post-operative MRIs. CONCLUSION The immediate post-operative findings are suggestive of a hemorrhagic, rather than an ischemic process in the dentate nuclei. On long-term follow up, the signal changes in the dentate and the inferior olivary nuclei represent dystrophic mineralization and hypertrophic degeneration, due to inflammation and axonal degeneration within the dentatorubroolivary tract2

Asymptomatic Postoperative Cerebral Venous Sinus Thrombosis After Posterior Fossa Tumor Surgery: Incidence, Risk Factors, and Therapeutic Options.

Cerebral venous sinus thrombosis (CVST) is a known complication of posterior fossa surgery near the sigmoid and transverse sinus. The incidence and treatment of postoperative asymptomatic CVST are controversial. To analyze incidence, risk factors, and management of asymptomatic postoperative CVST after posterior fossa tumor surgery. In this retrospective, single-center study, we included all patients who underwent posterior fossa tumor surgery in the semisitting position between January 2013 and December 2020. All patients underwent preoperative and postoperative imaging using MRI with/without additional computed tomography angiography. We analyzed the effect of demographic and surgical data on the incidence of postoperative CVST. Furthermore, therapeutic anticoagulation or conservative treatment for postoperative CVST and the incidence of intracranial hemorrhage were investigated. In total, 266 patients were included. Thirty-three of 266 (12.4%) patients developed postoperative CVST. All patients were asymptomatic. Thirteen of 33 patients received therapeutic anticoagulation, and 20 patients did not. Univariate analysis showed that age ( P = .56), sex ( P = .20), American Society of Anesthesiology status ( P = .13), body mass index ( P = .60), and length of surgery ( P = .176) were not statistically correlated with postoperative CVST. Multivariate analysis revealed that meningioma ( P < .001, odds ratio 11.3, CI 95% 4.1-31.2) and vestibular schwannoma ( P = .013, odds ratio 4.4, CI 95% 1.3-16.3) are risk factors for the development of new postoperative CVST. The use of therapeutic anticoagulation to treat postoperative CVST was associated with a higher rate of intracranial hemorrhage (n = 4, P = .017). Tumor entity influences the incidence of postoperative CVST. In clinically asymptomatic patients, careful decision making is necessary whether to initiate therapeutic anticoagulation or not.

Microsurgical Neurovascular Anatomy of the Brain: The Posterior Circulation (Part II)

Introduction:Vascular complications of posterior fossa surgery are often deadly although widely preventable through in-depth knowledge of the microsurgical neurovascular anatomy of the infratentorial region and careful surgical planning. The target of this study is to provide a synoptic overview of the normal anatomy and anatomic variants of the infratentorial neurovascular system, critical to safely operate tumors and neurovascular pathologies of the posterior fossa.Methods:Two fresh-frozen and five formalin-fixed cadaveric heads were used. Cervical arteries and internal jugular veins were injected with red and blue latex, respectively. The heads were dissected under a surgical microscope, with magnifications ranging between 3x to 40x, focusing on the infratentorial region. The infratentorial arteries, their collaterals and perforating branches, the brainstem and cerebellar veins, the tentorial venous sinuses, and the relative vascular territories were summarized according to a synoptic approach.Results:The vertebral artery, basilar artery (BA), and posterior cerebral artery (PCA) are the main sources of the arterial supply of the brainstem and cerebellum through the posterior inferior cerebellar artery (PICA), the anterior inferior cerebellar artery (AICA), the superior cerebellar artery (SCA), and the perforating arteries. The perforating arteries of the vertebrobasilar system derive from the PICA, BA, AICA, SCA, and PCA, and provide for a key contribution to the vascularization of the midbrain, pons, medulla oblongata, fourth ventricle, cerebellar and cerebral peduncles, thalamus, hypothalamus, subthalamus, posterior part of the internal capsule, and optic tract. The distal segments and branches of the PCA also add a significant arterial supply to the temporal, occipital, and parietal lobes. The venous outflow of the posterior fossa is a prerogative of the internal jugular veins via the tentorial venous sinuses.Conclusion:A perfect mastery of the arterial, venous, and cisternal anatomy of the infratentorial region is vital for the planning and execution of the whole range of posterior fossa approaches.

Cerebellar swelling after surgery for medulloblastoma with leptomeningeal dissemination in children. A case based-update

ObjectDespite the improvement in the overall management of medulloblastomas in recent years, certain phenomena and in particular postoperative cerebellar swelling remain an enigma. This rare complication, little described in the literature, is nonetheless life threatening for the patients. Case reportsWe report our experience about two children who developed severe cerebellar swelling with hydrocephalus and upward herniation soon after a gross total resection of a fourth ventricle medulloblastoma by a telo-velar approach. Despite rapid management of ventricular dilation and optimal medical intensive treatment of intracranial hypertension, both children died quickly after the surgery. Pathological examination analyses were in favour of anaplastic/large cell medulloblastoma. DiscussionDiffuse cerebellar swelling with upward herniation may occur postoperatively in young children with anaplastic/large cell medulloblastoma with leptomeningeal spread. In the literature, only 4 cases have been so far described with delayed onset of symptoms. Two children survived with an aggressive management (decompressive surgery and early radio-chemotherapy). ConclusionCerebellar swelling is an unrecognised and sudden complication of posterior fossa surgery for metastatic anaplastic medulloblastoma with leptomeningeal dissemination in young children. An initial less invasive surgical approach could be considered in such cases, in order to prevent this complication with potentially tragic issue, and which cannot be managed with a CSF shunt alone.

Surgical approach to the posterior fossa in children, including anesthetic considerations and complications: The prone and the sitting position. Technical note

IntroductionMedulloblastoma (MB) in children is, in most cases, a midline lesion located in the posterior fossa, with a high tendency to invade the fourth ventricle (and sometimes its floor). MethodsIn this technical note, we present both the sitting and the prone position for children with medulloblastoma. These positions will be described together by deliberately deciding not to oppose one against the other. The park bench position, seldom used in pediatric neurosurgery is not described here. The latter procedure can be useful, however, for MB located more laterally or within the cerebellopontine angle. ResultsThe aim of this technical note is to provide the reader with a step by step procedure (from installation to closure), at least from the author's point of view. A special focus regarding anesthetic considerations is also provided. This anesthesia requires perfect coordination and communication between both the anesthetic and surgical teams. Complications of posterior fossa surgery are mentioned as well. Some of the advantages and disadvantages of each positions are mentioned. ConclusionOnly careful installation, respect of certain surgical principles (careful attention of the vermis and dentate nuclei for example), knowledge of anatomy, closure and perioperative monitoring, screening and immediate correction of potentially devastating complications will enable surgeons to obtain the best results from their surgery.

Hemifacial Spasm Associated with Chiari Type I Malformation: Surgical Considerations and Case Report

AbstractHemifacial spasm (HS) is a movement disorder characterized by paroxysmal and irregular contractions of the muscles innervated by the facial nerve. Chiari malformation type I (CM I) is a congenital disease characterized by caudal migration of the cerebellar tonsils, and surgical decompression of foramen magnum structures has been used for treatment. The association of HS with CM I is rare, and its pathophysiology and therapeutics are speculative. There are only a few cases reported in the literature concerning this association. The decompression of the posterior fossa for the treatment of CM I has been reported to relieve the symptoms of HS, suggesting a relation between these diseases. However, the possible complications of posterior fossa surgery cannot be underrated. We report the case of a 66-year-old patient, in ambulatory follow-up due to right HS, no longer responding to botulinum toxin treatment. Magnetic resonance imaging (MRI) of the skull revealed compression of the facial nerve and CM I. The patient underwent surgery for HS by neurovascular microdecompression of the facial nerve via right lateral suboccipital craniectomy, but presented significant clinical worsening in the postoperative period even though the cerebellum edema related to surgical manipulation was mild. Due to the clinical worsening, the patient underwent a median suboccipital craniectomy with decompression of the foramen magnum structures. After this second surgery, the patient had progressive improvement and was discharged from the hospital for ambulatory care.

Postoperative posterior fossa pseudomeningocele: risk factors and management strategies

Background: Pseudomeningocele is a considerable morbidity after posterior fossa surgery. Its incidence and optimal management strategies are quite unclear. Hence the objective of this study is to define the risk factors and evaluate the management strategies and to study the incidence and morbidity of postoperative posterior fossa pseudomeningocele.Methods: A retrospective study of 33 patients undergone posterior fossa surgery for variety of diseases in the department of neurosurgery, Saveetha Medical College and Hospital from January 2015 to December 2018 with emphasis on incidence of pseudomeningocele,its morbidity and treatment strategies.Results: Out of 33 posterior fossa surgeries performed, 9 developed pseudomeningocele. Hence the incidence of pseudomeningocele in hospital is 27.27%. Out of 9 patients who developed pseudomeningocele, 6 patients were symptomatic, and aspiration was done to 5 patients and one patient underwent resurgery. That one patient underwent subgaleal-peritoneal shunt, excision of recurrent tumor was performed after which the symptoms subsided.Conclusions: Psudomeningocele is a well-known complication of posterior fossa surgery. The risk factors for pseudomeningocele formation after posterior fossa surgery has been evaluated. Age, sex and type of surgery are found to be a risk factors in our study. Conservative management is effective in most cases to reduce the symptoms. Surgical intervention is advocated, only when conservative treatment fails. Preventive measures like careful perioperative planning, strict adherence to aseptic techniques, usage of autologous pericranium with dural sealant augmentation, polyethylene glycol hydrogel dural sealant can be adopted.

Posterior Fossa

The posterior fossa houses essential brainstem nuclei, cranial nerves, cerebral vasculature, and mechanisms for cerebrospinal fluid drainage. Anesthetic considerations for posterior fossa surgery include thorough preoperative evaluation, intraoperative monitoring, and anesthetic planning to allow neurophysiological monitoring. Careful positioning is imperative to optimize surgical conditions and to risk stratify patients for complications, including venous air embolus. Venous air embolus is a common complication of posterior fossa surgery given the plentitude of venous channels in the posterior fossa, and rapid recognition is key to managing this complication. Posterior fossa surgery also has a number of other known complications including postoperative apnea, prolonged ventilation, and possible brainstem stroke. This review contains 4 tables, 1 video, and 31 references. Keywords: Posterior fossa surgery, Brainstem surgery, Neuroanesthesiology, Venous air embolism/embolus, Sitting craniotomy, Prone craniotomy, Transesophageal echocardiogram, Neurophysiologic monitoring

Cerebral venous sinus thrombosis after vestibular schwannoma surgery: a call for evidence-based management guidelines

OBJECTIVE Postoperative cerebral venous sinus thrombosis (CVST) is an uncommon complication of posterior fossa surgery. The true incidence of and optimal management strategy for this entity are largely unknown. Herein, the authors report their institutional incidence and management experience of postoperative CVST after vestibular schwannoma surgery. METHODS The authors undertook a retrospective review of all vestibular schwannoma cases that had been treated with microsurgical resection at a single institution from December 2011 to September 2017. Patient and tumor characteristics, risk factors, length of stay, surgical approaches, sinus characteristics, CVST management, complications, and follow-up were analyzed. RESULTS A total of 116 patients underwent resection of vestibular schwannoma. The incidence of postoperative CVST was 6.0% (7 patients). All 7 patients developed lateral CVST ipsilateral to the lesion. Four cases occurred after translabyrinthine approaches, 3 occurred after retrosigmoid approaches, and none occurred following middle cranial fossa approaches. Patients were managed with anticoagulation or antiplatelet therapy. Although patients were generally asymptomatic, one patient experienced intraparenchymal hemorrhage, epidural hemorrhage, and obstructive hydrocephalus, likely as a result of the anticoagulation therapy. However, all 7 patients had a modified Rankin scale score of 1 at the last follow-up. CONCLUSIONS Postoperative CVST is an infrequent complication, with an incidence of 6.0% among 116 patients who had undergone vestibular schwannoma surgery at one institution. Moreover, the management of postoperative CVST with anticoagulation therapy poses a serious dilemma to neurosurgeons. Given the paucity of reports in the literature and the low incidence of CVST, additional studies are needed to better understand the cause of thrombus formation and help to establish evidence-based guidelines for CVST management and prevention.

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.

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

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. 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. 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. 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.

Unexpected ruptured aneurysm during posterior fossa surgery

Background and importanceSurgery is the recommended treatment for unique significant cerebellar metastasis, particularly in cases of hydrocephalus. Complications of posterior fossa surgery are associated with high risk of morbidity and mortality. We present a unique case of unexpected peroperative rupture of a cerebellar superior artery aneurysm during posterior fossa surgery. Clinical presentationDuring posterior cranial fossa surgery, severe arterial bleeding occurred in front of the medulla oblongata. Immediate postoperative computed tomographic (CT) angiography revealed a fusiform aneurysm from a distal branch of the left superior cerebellar artery. ConclusionTo our knowledge, this is the first reported operative case of unexpected infratentorial ruptured aneurysm during posterior fossa surgery.

Cerebellar Mutism After Posterior Fossa Tumor Resection

Cerebellar mutism (also known as posterior fossa syndrome) is a relatively common complication of posterior fossa surgery for primary brain tumors in children. Many children with cerebellar mutism experience long-term adverse neurological, cognitive, and psychological sequelae and require extensive interdisciplinary support. This study illustrates a typical case of cerebellar mutism in a child after resection of medulloblastoma, followed by a review of associated symptoms, clinical course, and modulating factors. Additionally, recommendations for providing educational support to children with cerebellar mutism are explored.

Subdural hygroma following posterior fossa tumor resection

Subdural hygroma is an unusual complication of posterior fossa tumor surgery. We present two cases where patients developed subdural hygroma following posterior fossa surgery for brain tumors. This rare complication manifested with headaches, nausea, unsteadiness and nystagmus two weeks after seemingly uncomplicated surgery. There have been a few such cases described in the literature; mostly following foramen magnum decompression. The exact etiology of subdural hygroma post-posterior fossa surgery remains unknown; however, there are speculations that external hydrocephalus and intracranial hypotension may play a part. After exhausting conservative options, both patients underwent ventriculo-peritoneal shunting, which resulted in the resolution of their symptoms with corresponding resolution of the subdural hygroma on radiological imaging. We present two cases where subdural hygroma following surgery was successfully treated with a ventriculo-peritoneal shunt. We also highlight the paucity in literature regarding subdural hygroma as a complication of posterior fossa surgery and suggest management of such patients.

Transient mutism and cerebellar ischemic stroke: case report

Abstract The ischemic stroke is one of the most common conditions in our hospitals, representing 50% of revenues of neurology services. A variety of processes is cerebral ischemic myocardial cerebellum. Cerebellar infarction is not a rare disease, representing between 2 to 4% of all cerebrovascular events in clinical and autopsy series, and their ratio is 4-5 times higher than cerebellar hemorrhage. Although it is increasingly documented, it rarely Recognized stills like a phenomenon. Mutism occurs primarily in children and occasionally in adults as a well-recognized complication of posterior fossa surgery. Rarely been reported transient mutism associated with cerebellar infarction as isolated episode

Dysphagia as a Complication of Posterior Fossa Surgery in Adults

Dysphagia is a swallowing dysfunction and a known complication after posterior fossa surgery. It may lead to aspiration, dehydration, and malnutrition, all lifethreatening complications. Swallowing is a complex process that is activated in several phases, each involving both sensory and motor fibers. To understand the implications of dysphagia, we will briefly review the anatomy and physiology of the swallowing process. The first phase is the oral preparatory stage, or food mastication starting after the food is introduced into the mouth. This stage involves the trigeminal nerve that innervates the mastication muscles, the facial nerve that innervates the labial and buccinator muscles, and the hypoglossal nerve that innervates the tongue to move the food to the posterior teeth. This is followed by the oral stage, when the food is moved to the posterior part of the oral cavity, mainly controlled by the tongue (hypoglossal nerve). The third part is the pharyngeal stage, a reflex action that transports the food through the pharynx to the esophagus, but not to the nasopharynx or larynx that should be closed, thus protecting the airway from aspiration (mediated by cranial nerves IXeXI). The esophageal stage is a reflexive stage that transports the food by the esophageal peristaltic movement and relaxation of the lower esophageal sphincter (again, mediated by cranial nerves IXeXI). The posterior fossa is a small region containing the brain stem, cerebellum, and fourth ventricle and controls many vital functions, such as speech, hearing, movement, sensation, and swallowing. Expansion of a mass in the posterior fossa occurs at the expense of the normal structures in the region and may result in brain stem or cerebellar dysfunction. Less than 5% of all adult tumors originate in the posterior fossa, whereas approximately 50% of primary central nervous system tumors occurring in

Cerebellar Mutism After Pineal Tumour Excision: A Case Report

Cerebellar mutism syndrome (CMS) was first described by Rekate et al in 1985. This syndrome is a common complication of posterior fossa surgery in children with range of 11-29% and usually manifests as diminished speech, hypotonia, and ataxia. The cause is due to bilateral pertubation of the dentate nuclei and their efferent pathways by edema, perfusional defects, axonal damage or metabolic disturbances. Other rare causes of CMS like acute subdural hematoma of the posterior fossa, head injury, brainstem glioma surgery, meningitis and basilar artery occlusion have also been reported. CMS after supracerebellar resection of the pineal tumor is a very rare with very few cases reported. We report such a case in a 10- year old boy who underwent excision of a pineal tumor through the infratentorial supracerebellar route. Key Words: Cerebellar mutism; hydrocephalus; pineal tumor; posterior fossa. DOI: 10.3126/jnps.v31i2.4167 J Nep Paedtr Soc 2010;31(2):124-126

Novel Use of Zolpidem in Cerebellar Mutism Syndrome

Cerebellar mutism syndrome (CMS) is a complication of posterior fossa surgery seen primarily in pediatric patients after resection of medulloblastoma. CMS is characterized by mutism, ataxia, hypotonia, and irritability. Currently, there is no therapy of proven efficacy. Zolpidem, although primarily used as a sedative, has been shown to alleviate mutism and promote arousal in similar neurologic and psychiatric disorders. Here, we describe a child with severe CMS in whom zolpidem seemed to increase arousal, accelerate the resolution of mutism, and decrease emotional lability. Our report suggests that clinicians should consider using zolpidem for patients with CMS.

Cerebellar mutism

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. 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. 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. 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.