Telovelar Approach to Fourth Ventricle Tumors: Highlights and Limitations

Telovelar vs. Transvermian approach for the fourth ventricle tumors: A systematic review and meta-analysis

BACKGROUND

Tumors in the fourth ventricle can be critical due to the small size of the fourth ventricle, which causes symptoms to be detected even in the presence of lesser mass effects. A proper surgical approach to the fourth ventricle poses challenges due to its deep location and proximity to vital compartments within the brainstem. The two commonly used approaches to these tumors are the transvermian and telovelar approaches.

METHODS

A comprehensive systematic study was conducted based on a literature search of the databases. All case controls, cohorts, and case series including patients with fourth ventricle tumors, who were operated on with either telovelar or transvermian approaches were considered eligible. The evaluated outcomes were comparative postoperative complications of the telovelar vs. transvermian approach. After screening and data extraction, a meta-analysis was performed whenever adequate quantitative data were available.

RESULTS

Seven studies with a total number of 848 patients, discussed both telovelar and transvermian approaches, with comparative reporting of outcomes in each group. Postoperative outcomes including cranial nerve deficit, mutism, diplopia, CSF leak, need for CSF diversion, and postoperative gait disturbance were not significantly different between telovelar and transvermian approaches.

CONCLUSION

Postoperative complications were not significantly different between telovelar and transvermian approaches. Moreover, it could be proposed that such complications would be more likely to be a multifactorial matter concerning the patient's clinical condition, tumor characteristics, and surgeon's experience, rather than the surgical approach alone.

Anatomical Step-by-Step Dissection of Midline Suboccipital Approaches to the Fourth Ventricle for Trainees: Surgical Anatomy of the Telovelar, Transvermian, and Superior Transvelar Routes, Surgical Principles, and Illustrative Cases

Introduction  Safe, effective access to the fourth ventricle for oncologic resection remains challenging given the depth of location, restricted posterior fossa boundaries, and surrounding eloquent neuroanatomy. Despite description in the literature, a practical step-by step dissection guide of the suboccipital approaches to the fourth ventricle targeted to all training levels is lacking. Methods  Two formalin-fixed, latex-injected specimens were dissected under microscopic magnification and endoscopic visualization. Dissections of the telovelar, transvermian, and supracerebellar infratentorial-superior transvelar approaches were performed by one neurosurgery resident (D.D.D.), under guidance of senior authors. The dissections were supplemented with representative clinical cases to highlight pertinent surgical principles. Results  The telovelar and transvermian corridors afford excellent access to the caudal two-thirds of the fourth ventricle with the former approach offering expanded access to the lateral recess, foramen of Luschka, adjacent skull base, and cerebellopontine angle. The supracerebellar infratentorial-superior transvelar approach reaches the rostral third of the fourth ventricle, the cerebral aqueduct, and dorsal mesencephalon. Key steps described include positioning and skin incision, myofascial dissection, burr hole and craniotomy, durotomy, the aforementioned transventricular routes, and identification of relevant skull base landmarks. Conclusion  The midline suboccipital craniotomy represents a foundational cranial approach, particularly for lesions involving the fourth ventricle. Operatively oriented resources that combine stepwise neuroanatomic dissections with representative cases provide a crucial foundation for neurosurgical training. We present a comprehensive guide for trainees in the surgical anatomy laboratory to optimize familiarity with fourth ventricle approaches, mastery of relevant microsurgical anatomy, and simultaneous preparation for learning in the operating room.

Treatment of brainstem and fourth ventricle lesions by the full neuroendoscopic telovelar approach

OBJECTIVE

To explore the surgical techniques, advantages, and disadvantages of neuroendoscopic telovelar approach in the treatment of brainstem and fourth ventricle lesions.

METHODS

The clinical data of 5 patients treated by neuroendoscopic telovelar approach from March 2020 to March 2022 were analyzed retrospectively.

RESULTS

Among the 5 patients, there were 3 cavernous hemangiomas in pontine arm and 2 tumors in brainstem and fourth ventricle. All patients could successfully complete the operation, and 4 patients recovered well, other 1 patient discharged automatically for serious complications of other systems after the operation.

CONCLUSION

The telovelar approach has gained popularity as a safe and effective strategy for lesions in fourth ventricular and brainstem. However, without removing the posterior arch of the atlas, it is difficult to enter the upper part of the fourth ventricle under a microscope. Transcranial neuroendoscopy can effectively compensate for the shortcomings of microscopy, whether used as an auxiliary measure for microsurgery or alone with proficient endoscopic techniques, it will provide greater application in minimally invasive surgery for fourth ventricle and brainstem lesions. By utilizing the excellent degree of freedom of transcranial neuroendoscopy, there is no need to open the posterior arch of the atlas, making the surgery more minimally invasive. However, the sample size of this study is small, and it was completed under the very mature neuroendoscopic technology of our team. Its general safety and practicality still require extensive clinical research validation.

Predictors of postoperative complications and functional outcomes in pediatric patients with surgically treated fourth ventricle tumors

BACKGROUND

Tumors of the fourth ventricle are frequently treated pathologies in pediatric neurosurgery. Data regarding predictors for permanent neurological deficits, long-term functional outcomes, cerebellar mutism (CM), the extent of resection (EOR), and oncological outcomes are scarce. We attempt to contribute to this topic with an analysis of our institutional cohort.

METHODS

A retrospective single-center study of patients aged ≤ 19 years who underwent primary surgical resection of a fourth ventricular tumor over a 15-year period (2006-2021). Predictors analyzed included age, gender, surgical approach, anatomical pattern, tumor grade, EOR, tumor volume, and others as appropriate.

RESULTS

One hundred six patients were included (64 males, mean age 7.3 years). The rate of permanent neurological deficit was 24.2%; lateral tumor extension (p = 0.036) and tumor volume greater than 38 cm3 (p = 0.020) were significant predictors. The presence of a deficit was the only significant predictor of reduced (less than 90) Lansky score (p = 0.005). CM occurred in 20.8% of patients and was influenced by medulloblastoma histology (p = 0.011), lateral tumor extension (p = 0.017), and male gender (p = 0.021). No significant difference between the transvermian and telovelar approach in the development of CM was detected (p = 0.478). No significant predictor was found for the EOR. EOR was not found to be a significant predictor of overall survival for both low-grade and high-grade tumors; however, gross total resection (GTR) was protective against tumor recurrence compared to near-total or subtotal resection (p < 0.001). In addition, survival was found to be better in older patients (≥ 7.0 years, p = 0.019).

CONCLUSION

The overall rate of postoperative complications remains high due to the eloquent localization. Older patients (> 7 years) have been found to have better outcomes and prognosis. Achieving GTR whenever feasible and safe has been shown to be critical for tumor recurrence. CM was more common in patients with medulloblastoma and in patients with tumors extending through the foramen of Luschka. The telovelar approach uses a safe and anatomically sparing corridor; however, it has not been associated with a lower incidence of CM and neurological sequelae in our series, showing that each case should be assessed on an individual basis.

Endoscopic trans-Magendie foramen biopsy of the superior medullary velum: Technical note

BACKGROUND

Surgery of the fourth ventricle is challenging due to the presence of several surrounding delicate structures. Traditional approaches do not offer an easy visualization of these areas, especially those on the roof. Thanks to the most recent developments in neurosurgical endoscopy, it is possible to access the fourth ventricle via physiological pathways, avoiding unnecessary stress or damage to the nervous and vascular structures.

METHODS

We present the case of a patient with a lesion at the lingula-superior medullary velum, and an history of surgically resected lung and pancreatic adenocarcinomas. An endoscopic biopsy of the lesion through the foramen of Magendie was performed. The few reports on this endoscopic approach were also critically reviewed.

RESULTS

The retrograde endoscopic exploration through a suboccipital, trans-Magendie foramen approach using a flexible endoscope allowed the clear visualization of the superior medullary velum and the possibility to obtain diagnostic biopsies of the lesion with a minimally invasive technique.

CONCLUSIONS

The trans-Magendie navigation with a flexible endoscope is a safe and elegant technique to approach lesions located in any point of the fourth ventricle, particularly in its rostral portion.

Posterior fossa choroidplexus papilloma in the pediatric population: case series and literature review

Choroid plexus papillomas (CPPs) are rare benign neoplasms which are particularly uncommon in the posterior fossa in children. We herein present a case series of five patients treated at a tertiary care hospital. A comprehensive literature review was also carried out. The patients treated at the tertiary care hospital were aged between 4 and 16 years. Gross total resection (GTR) was initially achieved in two patients. All patients showed clinical improvement. Moreover, 27 articles published between 1975 and 2021 were selected for the literature review, totaling 46 patients; with the 5 patients previously described, the total sample was composed of 51 cases, With a mean age was 8.2 years. The lesions were located either in the fourth ventricle (65.3%) or the cerebellopontine angle (34.7%). Hydrocephalus was present preoperatively in 66.7% of the patients, and a permanent shunt was required in 31.6% of the cases. The GTR procedure was feasible in 64.5%, and 93.8% showed clinical improvement. For CPPs, GTR is the gold standard treatment and should be attempted whenever feasible, especially because the role of the adjuvant treatment remains controversial. Neuromonitoring is a valuable tool to achieve maximal safe resection. Hydrocephalus is common and must be recognized and promptly treated. Most patients will need a permanent shunt. Though there is still controversy on its efficacy, endoscopic third ventriculostomy is a safe procedure, and was the authors' first choice to treat hydrocephalus.

Management of Intraventricular Meningiomas

Intraventricular meningiomas (IVM) are intracranial tumors that originate from collections of arachnoid cells within the choroid plexus. The incidence of meningiomas is estimated to be about 97.5 per 100,000 individuals in the United States with IVMs constituting 0.7% to 3%. Positive outcomes have been observed with surgical treatment of intraventricular meningiomas. This review explores elements of surgical care and management of patients with IVM, highlighting nuances in surgical approaches, their indications, and considerations.

Microsurgical Management of Fourth Ventricle Lesions Via the Median Suboccipital Keyhole Telovelar Approach

In this 2-year retrospective analysis, 13 patients with fourth ventricle lesions who underwent microsurgical resection via the midline suboccipital keyhole telovelar approach were analyzed. This is the first study to investigate the surgical outcome and complications of using this approach to resect various types of lesions in the fourth ventricle. We aimed to clarify whether this approach has met its promise of lesion dissection. Three patients (23.1%) had intraoperative extraventricular drains. There were no immediate postoperative deaths. Gross total resection was achieved in 84.6% of the cases. The Fisher exact test showed there was no statistically significant correlation between lesion location, lesion size, brainstem invasion, and extent of resection. About two third (69.2%) of the cases were free of complications. New or worsening gait/focal motor disturbance (15.4%) was the most common neurological deficit in the immediate postoperative period. One patient (7.7%) had worse gait disturbance/motor deficit following surgical intervention. Two patients (15.4%) developed meningitis. Two patients (15.4%) required postoperative cerebrospinal fluid diversion after tumor resection, of these 2 patients, 1 (7.7%) eventually needed a permanent shunt. There were no cases of cerebellar mutism and bulbar paralysis. The median suboccipital keyhole telovelar approach provides relative wide access to resect most fourth ventricle tumors completely and with satisfactory results. In contrast, this requires the appropriate patient selection and skilled surgeons.

Medulloblastomas in Pediatric and Adults

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

The Cerebellar Mutism Syndrome: Risk Assessment, Prevention and Treatment

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

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

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

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.

Fourth Ventricle Tumors: A Review of Series Treated With Microsurgical Technique

Tumors of the IV ventricle represent 1–5% of all intracranial lesions; they are implicated in 2/3 of the tumors of the ventricular system. According to modern standards, the first treatment stage for this pathology is microsurgical removal. Currently, for the removal of neoplasms of the IV ventricle and brainstem, the median suboccipital approach is widely used, followed by one of the microapproaches. Moreover, with the development of microsurgical techniques, keyhole approaches are now beginning to be utilized. However, surgical treatment of these tumors remains a challenge for neurosurgeons due to the proximity of functionally important anatomical structures (the brainstem, the cerebellum, pathways, vessels, etc.) of the posterior cranial fossa. Therefore, surgery in this area is associated with the possible occurrence of a wide range of postoperative complications. The authors provide a review of series of fourth ventricle tumors treated with microsurgical technique.

The Clinical and Prognostic Impact of the Choice of Surgical Approach to Fourth Ventricular Tumors in a Single-Center, Single-Surgeon Cohort of 92 Consecutive Pediatric Patients

Objective

A single-institution cohort of 92 consecutive pediatric patients harboring tumors involving the fourth ventricle, surgically treated via the telovelar or transvermian approach, was retrospectively reviewed in order to analyze the impact of surgical route on surgery-related outcomes and cumulative survival.

Methods

Clinical, radiological, surgical, and pathology details were retrospectively analyzed. We selected n = 6 surgery-related clinical and radiological outcomes: transient and permanent neurological deficits, duration of assisted ventilation, postoperative new onset medical events, postoperative cerebellar mutism, and extent of resection. We built univariate and multivariate logistic models to analyze the significance of relationships between the surgical routes and the outcomes. Cumulative survival (CS) was estimated by the cohort approach.

Results

There were 53 girls and 39 boys (mean age, 83 months). Telovelar approach was performed in 51 cases and transvermian approach in 41 cases. Early postoperative MRI studies showed complete removal in 57 cases (62%) and measurable residual tumor in 35 cases (38%). The average tumor residual volume was 1,316 cm³ (range, 0.016-4.231 cm³; median value, 0.9875 cm³). Residual disease was more often detected on immediate postop MRI after telovelar approach, but the difference was not significant. Cerebellar mutism was observed in 10 cases (11%). No significant difference in the onset of cerebellar mutism was detected between telovelar and transvermian approach. The choice of surgical approach did not significantly modify any other postoperative outcome and 1-/3-year CS of high-grade surgically treated tumors.

Conclusions

With the limitation of a single-center, single-surgeon retrospective series, our findings offer significant data to reconsider the real impact of the choice of the surgical route to the fourth ventricle on the incidence of cerebellar mutism and surgery-related morbidity. This seems to be in line with some recent reports in the literature. Surgical approach to the fourth ventricle should be individualized according to the location of the tumor, degree of vermian infiltration, and lateral and upward extension. Telovelar and transvermian approaches should not be considered alternative but complementary. Pediatric neurosurgeons should fully master both approaches and choose the one that they consider the best for the patient based on a thorough and careful evaluation of pre-operative imaging.

Second-look surgery after pediatric brain tumor resection – Single center analysis of morbidity and volumetric efficacy

Introduction

Postoperative residual tumor can occur for intentional or unintentional reasons. Decision-making regarding second-look surgery has to weigh molecular biology, probability of total resection and prognostic relevance against potential additional morbidity. In interdisciplinary tumor boards the neurosurgeon has to estimate risk and efficacy of second-look surgery in individual cases, based on precise data.

Research question

Aim of this study was to provide such data by analyzing morbidity and volumetric efficacy of second-look surgery at a designated pediatric neuro-oncology unit.

Material and methods

Children who received second-look surgery in 2007–2018 after incomplete resections were analyzed retrospectively. Measurements were performed on early postoperative magnetic resonance imaging, comparing axial diameter-based measurement as well as computer-assisted volumetric analysis.

Results

59 patients (37% of the overall cohort; 21 female; mean age: 8 ​± ​5 years) received a subtotal (n ​= ​35) or near total (n ​= ​24) resection. After interdisciplinary case review, 12 of these patients received second-look surgery mainly for residual ependymoma. This led to further tumor volume reduction in all cases (new degrees of resection: subtotal ​= ​2, near total ​= ​6, gross total ​= ​4). No new permanent morbidity or perioperative mortality was observed.

Discussion and conclusion

Second-look surgery did not increase mortality and permanent morbidity, had an 8% rate of transient morbidity and achieved tumor volume reduction above 95% in 75% of selected cases, with 4 additional gross total resections. Second-look surgery is safe and effective with regard to volumetric outcome parameters even in cases with good initial resections, although the role of second-look surgery regarding oncological outcome has to be further investigated in times of personalized molecular medicine.

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Second-look surgery after incomplete initial resection of a pediatric brain tumor does not increase mortality and permanent surgical morbidity.

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It achieves a reduction of tumor volume above 95% in 75% of selected cases, with 4 additional gross total resections per 12 patients undergoing second-look surgery.

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Irrespective of two-dimensional or three-dimensional measurement methodology, criteria for near total resection correspond well and consistently showed an extent of resection above 95%.

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In the era of molecular and personalized medicine, children with specific tumors and molecular biology (e.g. PF-EPN-A ependymoma or group 4 medulloblastoma) might be candidates for second-look surgery after interdisciplinary review. This study gives the neurosurgeon accessible information to precisely characterize the neurosurgical implications of second-look surgery in such tumor board discussions.

Current treatments of medulloblastoma

PURPOSE OF REVIEW

The biological knowledge and the new biopathological classification of medulloblastoma subtypes have dramatically changed the therapeutic indications, taking into account not only age and staging but also biopathological risk criteria. This review covers the multidisciplinary approach including surgery, radiation oncology and medical treatments.

RECENT FINDINGS

The neurosurgical management of tumor-related hydrocephalus has been modified by the introduction of third ventriculostomy. The initial complete excision is no longer always the first choice, to preserve neurological function. The recent technical improvements of radiotherapy are also implemented to optimize outcome in terms of survival as well as quality of survival. The different medical treatments are adapted according to age and risk factors. The role of high-dose chemotherapy with autologous hematopoietic stem cell rescue has become larger in the high-risk situations.

SUMMARY

The rarity of the disease and the high-level of technicity of diagnosis, biopathological subtyping and treatments justifies the referral of these patients to highly specialized centers where all these techniques can be routinely applied, most often in the context of international prospective studies.

Postoperative speech impairment and surgical approach to posterior fossa tumours in children: a prospective European multicentre cohort study

BACKGROUND

Brain tumours are the most common solid tumours in childhood. Half of these tumours occur in the posterior fossa, where surgical removal is complicated by the risk of cerebellar mutism syndrome, of which postoperative speech impairment (POSI) is a cardinal symptom, in up to 25% of patients. The surgical approach to midline tumours, mostly undertaken by transvermian or telovelar routes, has been proposed to influence the risk of POSI. We aimed to investigate the risk of developing POSI, the time course of its resolution, and its association with surgical approach and other clinical factors.

METHODS

In this observational prospective multicentre cohort study, we included children (aged <18 years) undergoing primary surgery for a posterior fossa tumour at 26 centres in nine European countries. Within 72 h of surgery, the operating neurosurgeon reported details on the tumour location, surgical approach used, duration of surgery, use of traction, and other predetermined factors, using a standardised surgical report form. At 2 weeks, 2 months, and 1 year after surgery, a follow-up questionnaire was filled out by a paediatrician or neurosurgeon, including neurological examination and assessment of speech. Speech was classified as mutism, reduced speech, or habitual speech. POSI was defined as either mutism or severely reduced speech. Ordinal logistic regression was used to analyse the risk of POSI.

FINDINGS

Between Aug 11, 2014, and Aug 24, 2020, we recruited 500 children. 426 (85%) patients underwent primary tumour surgery and had data available for further analysis. 192 (45%) patients were female, 234 (55%) patients were male, 81 (19%) patients were aged 0-2 years, 129 (30%) were aged 3-6 years, and 216 (51%) were aged 7-17 years. 0f 376 with known postoperative speech status, 112 (30%) developed POSI, 53 (14%) developed mutism (median 1 day [IQR 0-2]; range 0-10 days), and 59 (16%) developed reduced speech after surgery (0 days [0-1]; 0-4 days). Mutually adjusted analyses indicated that the independent risk factors for development of POSI were younger age (linear spline, p=0·0087), tumour location (four levels, p=0·0010), and tumour histology (five levels, p=0·0030); surgical approach (six levels) was not a significant risk factor (p=0·091). Tumour location outside the fourth ventricle and brainstem had a lower risk of POSI (with fourth ventricle as reference, odds ratio (OR) for cerebellar vermis 0·34 [95% CI 0·14-0·77] and OR for cerebellar hemispheres 0·23 [0·07-0·70]). Compared with pilocytic or pilomyxoid astrocytoma, a higher risk of POSI was seen for medulloblastoma (OR 2·85 [1·47-5·60]) and atypical teratoid rhabdoid tumour (10·30 [2·10-54·45]). We did not find an increased risk of POSI for transvermian surgical approach compared with telovelar (0·89 [0·46-1·73]). Probability of speech improvement from mutism reached 50% around 16 days after mutism onset.

INTERPRETATION

Our data suggest that a midline tumour location, younger age, and high-grade tumour histology all increase the risk of speech impairment after posterior fossa tumour surgery. We found no evidence to recommend a preference for telovelar over transvermian surgical approach in the management of posterior fossa tumours in children in relation to the risk of developing POSI.

FUNDING

The Danish Childhood Cancer Foundation, the Swedish Childhood Cancer Foundation, the UK Brain Tumour Charity, the Danish Cancer Society, Det Kgl Kjøbenhavnske Skydeselskab og Danske Broderskab, the Danish Capitol Regions Research Fund, Dagmar Marshall Foundation, Rigshospitalet's Research Fund, and Brainstrust.

Surgical considerations for maximal safe resection of exophytic brainstem glioma in the pediatric age group

Background:

Brainstem glioma is the leading cause of morbidity and mortality among all central nervous system tumors, especially in childhood as it represents about 20% of all pediatric brain tumors. Therefore, this study aimed to present our experience in a tertiary center in a developing country with limited resources for the surgical management of exophytic brainstem gliomas.

Methods:

This retrospective study included pediatric patients with brainstem (midbrain, pontine, or medullary) focal or diffuse gliomas whether low or high grade that had dorsal, ventral, or lateral exophytic component who were presented to our hospitals from January 2019 to January 2021. The patients’ data were collected, such as age, sex, preoperative and postoperative clinical condition, radiological data, surgical approach, extent of tumor removal, histopathology, follow-up period, and adjuvant therapy.

Results:

A total of 23 patients were included in this study. The telovelar approach was used in 17 patients, the supracerebellar infratentorial approach in three patients, and the retrosigmoid, transcerebellar, and occipital transtentorial approach once for each patient. Twenty patients underwent near-total excision, and three underwent subtotal excision. Two-thirds of our cases (17 patients) were low-grade gliomas, with the remaining one-third comprising entirely of either anaplastic astrocytoma (five patients) or glioblastoma multiforme (one patient). The follow-up period of the patients extended from 3 months to 24 months.

Conclusion:

Exophytic brainstem glioma surgery can result in good outcomes with minimal complications when near-total excision is attempted through a properly chosen approach and adherence to some surgical techniques and considerations.

Surgical outcome of children with medulloblastoma: a retrospective study of a 405-patient series from Children's Cancer Hospital Egypt (CCHE-57357)

PURPOSE

To analyze the impact of increasing the extent of resection (EOR) on the survival rates and on the surgical outcome of children with medulloblastoma.

METHODS

A series of consecutive 405 children operated for medulloblastoma between July 2007 and April 2018 was identified. The details of pre-operative data, surgical interventions, post-operative complications, and survival rates were analyzed.

RESULTS

The Kaplan-Meier (KM) analysis showed no advantage of gross total resection (GTR) over near and subtotal resection regarding over all (OS) (p=0.557) and progression free survival (PFS) (p=0.146). In the same time, increasing the EOR was not associated with higher morbidity. Tumor dissemination at onset correlated to worse OS (KM: p=0.003, OR 1.999, 95% CI: 1.242-3.127; p = 0.004) and PFS (KM: p<0.001, Cox: OR 2.171, 95% CI: 1.406-3.353; p<0.001). OS was significantly affected in patients < 3 years old (KM: p=0.011, OR 2.036, 95% CI: 1.229-3.374; p = 0.006), while PFS was worse among patients who had pre-op seizures (KM: p=0.036, Cox: OR 2.852, 95% CI: 1.046-7.773; p=0.041) or post-op pseudomeningocele (KM: p=0.021, Cox: OR 2.311, 95% CI: 1.123-4.754; p=0.023).

CONCLUSIONS

Although surgical excision of medulloblastoma is the standard of care, there was no significant benefit for GTR over near or subtotal resection on the OS or PFS rates that are mainly influenced by the patient's age and tumor dissemination. However, GTR should be targeted, as it is not associated with increased incidence of mutism or other surgery-related complications.

Endoscope-Assisted Neuroportal Transcerebellar Approach to the Fourth Ventricle: An Anatomical Study

BACKGROUND AND STUDY AIMS

 Minimally invasive approaches to deep-seated lesions still represent a fundamental issue in modern neurosurgery. Tubular retractors allow to enhance the operability of intraventricular lesions, minimizing the risk of damages to brain parenchyma. Increasing interest for portal devices has been mainly focused on supratentorial pathologies, while transportal approaches in the posterior cranial fossa have been rarely described. In the present study, the authors aimed to investigate the surgical exposure and operability obtained with a microsurgical neuroportal transcerebellar approach targeting the fourth ventricle, assisted by endoscopic exploration.

MATERIAL AND METHODS

 Six cadaveric specimens were provided for anatomical microsurgical dissection and Vycor ViewSite Brain Access System was used as tubular retractor. Surgical feasibility of the neuroportal transcerebellar approach was demonstrated through a definable and measurable parameter, the operability score.

RESULTS

 The neuroport provided a surgical corridor away from eloquent structures to target the whole fourth ventricle cavity, preventing injury to cerebellar nuclei and white matter pathways and, potentially, minimizing the risk of surgical morbidity. Maximal operability was reached in the pontomedullary junction and medullary area of the ventricular floor. Transportal endoscopic assistance contributed to a further extension of surgical exposure in blind spots, corresponding to the ipsilateral lateral recess, the uppermost part of the fourth ventricle, and the obex.

CONCLUSION

 The neuroportal transcerebellar approach represents a viable alternative route to the fourth ventricle, avoiding vermian splitting or subarachnoid dissection of the cerebellomedullary cistern. Endoscopic assistance enhances the exposure of the surgical field and accomplishes a valid instrument for intraventricular orientation to ease microsurgical procedures.

Resection of a recurrent medulloblastoma in the anterior middle part of the aqueduct with a flexible endoscope: a case report

Resection or biopsy of intraventricular brain tumors using an endoscope has become common, but the limitations of these procedures are not clear. Manipulation to access a tumor that arises from the blind angle of the rigid endoscope, such as the anterior part of the aqueduct, is limited. We report here that we successfully resected a recurrent medulloblastoma in the anterior part of the aqueduct using only a flexible endoscope. This method appears to be suitable for poorly vascularized and suctionable tumors that arise in the blind angle of a rigid endoscope.

Surgical management of the fourth ventricular tumors using telovelar approach and the role of neuroendoscopy: Post-operative outcome and long-term results in a series of 52 cases

OBJECTIVES

The telovelar approach is a surgical method performed through natural corridors of the brain to access the fourth ventricle. The aim of this study is to assess the results of this approach as well as the role of neuroendoscopy in surgical management of fourth ventricle tumors.

MATERIAL AND METHODS

A retrospective study was designed, and a series of 52 consecutive patients (32 male, 20 female) with fourth ventricle tumor undergoing telovelar approach was undertaken. In 10 patients (19 %) with a tumor invading the rostral fourth ventricle, an adjustable angle endoscope was also used to ensure total resection of the tumor.

RESULTS

Complete resection was obtained in majority of patients (94 %). 30 patients (57 %) required insertion of an external ventricular drain which was discontinued in all patients after 72 h. 2 patients (4 %) underwent permanent ventriculoperitoneal shunt. The postoperative complications included meningitis (8 %), transient facial nerve paralysis (8 %), transient sixth cranial nerve paralysis (6 %) and transient unilateral absence of the gag reflex (4 %). No patient experienced mutism and there was a mortality rate of 2 % (1 case) in current study.

CONCLUSION

In our experience, a high rate of total resection of the fourth ventricle tumors could be achieved with the telovelar approach associated with a low risk of surgical morbidity and mortality. Moreover, the use of an adjustable angle endoscope could be useful in patients with a tumor involving the rostral fourth ventricle to ensure total resection of the tumor and also to minimize the extent of telovelar dissection.

Intraventricular neuroepithelial tumors: surgical outcome, technical considerations and review of literature

Background

Intraventricular neuroepithelial tumors (IVT) are rare lesions and comprise different pathological entities such as ependymomas, subependymomas and central neurocytomas. The treatment of choice is neurosurgical resection, which can be challenging due to their intraventricular location. Different surgical approaches to the ventricles are described. Here we report a large series of IVTs, its postoperative outcome at a single tertiary center and discuss suitable surgical approaches.

Methods

We performed a retrospective chart review at a single tertiary neurosurgical center between 03/2009–05/2019. We included patients that underwent resection of an IVT emphasizing on surgical approach, extent of resection, clinical outcome and postoperative complications.

Results

Forty five IVTs were resected from 03/2009 to 05/2019, 13 ependymomas, 21 subependymomas, 10 central neurocytomas and one glioependymal cyst. Median age was 52,5 years with 55.6% (25) male and 44.4% (20) female patients. Gross total resection was achieved in 93.3% (42/45). 84.6% (11/13) of ependymomas, 100% (12/21) of subependymomas, 90% (9/10) of central neurocytomas and one glioependymal cyst were completely removed. Postoperative rate of new neurological deficits was 26.6% (12/45). Postoperative new permanent cranial nerve deficits occurred in one case with 4th ventricle subependymoma and one in 4th ventricle ependymoma. Postoperative KPSS was 90% (IR 80–100). 31.1% of the patients improved in KPSS, 48.9% remained unchanged and 20% declined. Postoperative adverse events rate was 20.0%. Surgery-related mortality was 2.2%. The rate of shunt/cisternostomy-dependent hydrocephalus was 13.3% (6/45). 15.4% of resected ependymomas underwent adjuvant radiotherapy. Mean follow-up was 26,9 (±30.1) months.

Conclusion

Our surgical findings emphasize satisfactory complete resection throughout all entities. Surgical treatment can remain feasible, if institutional experience is given. Satisfying long-term survival and cure is possible by complete removal. Gross total resection should always be performed under function-remaining aspects due to mostly benign or slow growing nature of IVTs. Further data is needed to evaluate standard of care and alternative therapy options in rare cases of tumor recurrence or in case of patient collective not suitable for operative resection.

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.

Cerebellar mutism syndrome: current approaches to minimize risk for CMS

PURPOSE

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

METHODS

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

RESULTS

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

DISCUSSION

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

Evolution of cerebellomedullary fissure opening: its effects on posterior fossa surgeries from the fourth ventricle to the brainstem

Surgical approaches to the fourth ventricle and its surrounding brainstem regions have changed significantly in the previous 30 years, after the establishment of cerebellomedullary fissure (CMF) opening. With the development of CMF opening techniques, CMF opening surgeries have become widely used for the treatment of various pathologies and have contributed to the improvement of surgical results in posterior fossa surgeries. We here review the historical progress of CMF opening surgeries to help the future progression of neurosurgical treatments. The authors studied the available literature to clarify how CMF opening surgeries have developed and progressed, and how much the idea and development of CMF opening techniques have affected the advancement of posterior fossa surgeries. With the establishment of angiography, anatomical studies on CMF in the 1960s were performed mainly to clarify vascular anatomy on radiological images. After reporting the microsurgical anatomy of CMF in a cadaveric study in 1982, one of the authors (T.M.) first proposed the clinical usefulness of CMF opening in 1992. This new method enabled wide exposure of the fourth ventricle without causing vermian splitting syndrome, and it took the place of the standard approach instead of the conventional transvermian approach. Several authors reported their experiences using this method from the end of the twentieth century to the early twenty-first century, and the naming of the approach, "telovelar approach" by Mussi and Rhoton in 2000 contributed to the global spread of CMF opening surgeries. The approach has become widely applied not only for tumors but also for vascular and brainstem lesions, and has assisted in the development of their surgical treatments, and brought up the idea of various fissure dissection in the posterior fossa. Studies of microsurgical anatomy of the fourth ventricle, including the CMF, has led to new surgical approaches represented by the transCMF/telovelar approach. The CMF opening method caused a revolution in posterior fossa surgeries. The idea was developed based on the experience gained while dissecting the CMF (the roof of the fourth ventricle) in the laboratory. Anatomical studies using cadaveric specimens, particularly their dissection by surgeons themselves, together with a deep understanding of brain anatomy are essential for further advancements in neurosurgical treatments.

Telovelar surgical approach

Surgical access to lesions in the fourth ventricle may be achieved utilizing transvermian or transtelovelar trajectories. We performed a search of the PubMed database for studies describing the microsurgical details and evaluating the clinical utility of the telovelar surgical approach. The telovelar approach has proven to be a safe, effective, and versatile alternative to the transvermian approach. The operative strategy utilizes midline suboccipital craniotomy without or with C1 laminectomy, followed by cerebellar hemispheric and tonsillar retraction, and wide durotomy. Access is generously provided to the fourth ventricle from calamus scriptorius to Sylvian aqueduct and foramen Luschkae bilaterally. Anatomic dissection studies evaluating and comparing the relative benefits of the operative exposure offered by these approaches have demonstrated improved access to the lateral recess gained by the telovelar trajectory and facilitated exposure of rostral reaches of the fourth ventricle by the vermian trajectory. In general, operative exposure may be significantly improved with tonsillar retraction or resection, bilateral telovelar opening, and performing C1 laminectomy in order to improve access to the rostral fourth ventricle, which may be variably combined depending on location of pathology. Cerebellar mutism, a high incidence of which occurs with vermian approaches, is not commonly observed with use of the telovelar trajectory, though injury to the dentate nuclei may precipitate this syndrome. Deficits incurred with the vermian approach may include cerebellar mutism, dysequilibrium, truncal ataxia, posterior fossa syndrome, cranial nucleopathies and nerve palsies, and vascular injury to the posterior inferior cerebellar artery. The telovelar surgical approach has proven a safe and useful alternative to the transvermian trajectory. A significantly lower incidence of cerebellar mutism and cerebellogenic deficits represents the principal advantage of the telovelar approach. Further studies are necessary in order to prospectively evaluate and compare extents of resection, morbidity, and mortality utilizing the telovelar versus vermian approaches for microsurgically resecting fourth ventricular tumors.

Telovelar approach for microsurgical resection of fourth ventricular subependymoma arising from rhomboid fossa: operative video and technical nuances

Fourth ventricular tumors have traditionally been removed via transvermian approaches, which can result in potential dysequilibrium and mutism. The telovelar approach is an excellent alternative to widely expose fourth ventricular tumors without transgressing the cerebellar vermis. This is achieved by opening the cerebellomedullary fissure and incising the tela choroidea and inferior medullary velum, which form the lower half of the roof of the fourth ventricle. In this operative video manuscript, the authors demonstrate microsurgical resection of a fourth ventricular subependymoma arising from the rhomboid fossa via the telovelar approach. The key technical nuance in this video is to demonstrate a gentle and safe technique to identify a dissectable plane to peel the tumor off of the rhomboid fossa using a microspreading technique with fine micro-bayonetted forceps. A gross-total resection was achieved, and the patient was neurologically intact.

The video can be found here: https://youtu.be/ZEHHbUGb9zk.

Fourth Ventricular Meningiomas

OBJECTIVE

Fourth ventricular meningiomas (FVMs) are extremely rare. Here, we report a series of 11 patients at a single institution. A comprehensive literature analysis is conducted.

METHODS

Information about 11 patient was extracted from the patient data. Reports of cases in English were obtained from the literature. Including our 11 patients, 71 patients were analyzed in this study.

RESULTS

The most common age of onset was from the third decade to sixth decade of life. The female/male ratio was about 1.16:1. The most frequent subtype of meningioma was fibrous meningioma. FVMs had specific imaging features, such as calcification (20%), peritumoral edema (30.3%), heterogeneous enhancement (22.5%), cystic formation (4.3%), and hydrocephalus (52.8%). The proportion of total tumor resection was about 94.9%, with 15.3% of postoperative complications. During follow-up, the recurrent rate of FVMs was about 6.8%. There was no significant difference in the analysis of correlation between hydrocephalus and the maximum diameter of tumors, correlation between hydrocephalus and the volume of tumor, or correlation between peritumoral edema and the volume of tumor, as well as correlation between heterogeneous enhancement and the grade of meningiomas.

CONCLUSIONS

FVMs have their own characteristics in age of onset, gender ratio, histologic types, and imaging features. The recommended treatment is surgical treatment via the telovelar approach with suboccipital craniotomy/craniectomy. Adjuvant therapy is needed in some high-grade meningiomas and in patients undergoing partial resection. The prognosis is relatively good, with fewer postoperative complications and a higher rate of total resection.

Long-term impairment of social behavior, vocalizations and motor activity induced by bilateral lesions of the fastigial nucleus in juvenile rats

The cerebellum is increasingly recognized to be involved in limbic and cognitive-associative functioning. Cerebellar cognitive affective syndromes may result from various types of injuries. Cerebellar mutism may occur in children after resection of midline tumors in the posterior fossa, which has been thought to be related to damage to the cerebellar vermis. Here, we investigated whether bilateral lesions of the fastigial nucleus, which is located within the upper vermis, would affect social behavior in a rat model. Juvenile male Sprague-Dawley rats, aged 23 days, underwent bilateral thermocoagulation of the fastigial nucleus via stereotaxically implanted electrodes under general anesthesia. Electrodes were inserted without application of electric current in a sham-lesion group and naïve rats served as additional controls. All groups underwent standardized examination before surgery and on specific time points up to 49 days after surgery to investigate locomotor activity, motor coordination, social behavior, and ultrasound vocalizations during social interaction. Finally, lesions were verified histologically. Playing behavior and vocalizations were reduced up to 4 weeks after surgery in rats of the lesion group compared to rats with sham-lesions and controls. After surgery in rats of the lesion group, locomotor activity was disturbed for 3 days as compared to sham-lesion rats, but for 4 weeks as compared to controls. Motor coordination measured by the rotarod and balance beam test was compromised until adulthood. Bilateral lesions of the fastigial nucleus in juvenile rats cause a severe and long-lasting reduction of social interaction and motor coordination in juvenile rats, which has some similarities to cerebellar cognitive affective syndromes in the human context. This indicates a modulating role of the fastigial nucleus with regard to neural circuitries relevant for social behavior, such as the limbic system and the prefrontal cortex.

Microsurgical Management of Fourth Ventricle Astrocytoma via Median Suboccipital Keyhole Approach: Review of 12 Cases

OBJECTIVE

To investigate the clinical effect and surgical techniques of fourth ventricle astrocytoma resection through the median suboccipital keyhole approach.

METHODS

Twelve patients received tumor resection through the median suboccipital keyhole approach in our department. A 4-cm median suboccipital excision starting 1 cm under the foramen magnum region and directed vertically upward was applied. The fourth ventricle was exposed through a cerebellomedullary fissure approach within a bone hole ≈2.5 cm in diameter. All clinical data (including preoperative/postoperative symptoms, magnetic resonance imaging scan, intraoperative findings, tumor resection rate, and surgical complications) were collected and analyzed.

RESULTS

In our treatment group, the mean maximum tumor diameter was 3.48 ± 1.3 cm and the mean tumor volume was 34.79 ± 20.70 cm³. The complete resection rate was 92%. The average operative blood loss was 127.0 ± 24.6 mL; the mean craniotomy time was 26.4 ± 6.0 minutes; the mean tumor resection time was 190.3 ± 31.2 minutes; the mean cranial closure time was 42.3 ± 6.1 minutes; and the average hospitalization time was 13.6 ± 2.4 days. The mean Glasgow Outcome Scale score before discharge was 4.92.

CONCLUSIONS

If appropriate microneurosurgical techniques are used via the median suboccipital keyhole approach, the fourth ventricle astrocytoma may be accessed and resected safely with shorter surgery time, reduced hemorrhage during operation, low incidence of postoperative complications, good recovery, and shorter hospitalization time.

The Tonsillouvular Fissure Approach: Access to Dorsal and Lateral Aspects of the Fourth Ventricle

OBJECTIVE

Although approaches to the fourth ventricle (FV) have been studied well, approaches to the lesions located in the dorsal and lateral aspects of the FV have not been shown in anatomic or clinical studies. The aim of this study is to show for the first time in the literature the tonsillouvular fissure approach (TUFA) in anatomic dissections and its use in surgical series.

METHODS

For anatomic studies, 4 formalin-fixed human cadaveric heads infused with colored silicone and 10 cerebellar specimens were dissected in a stepwise manner. Records of 12 patients operated on via TUFA were also retrospectively reviewed.

RESULTS

Neurosurgical anatomy and critical steps of TUFA were described in detail. Among 12 patients with lesions around the FV (4 cavernous malformation, 2 pilocytic astrocytoma, 2 hemangioblastoma, 1 B-cell lymphoma, 1 metastatic papillary carcinoma, 1 dermoid cyst, and 1 arteriovenous malformation), 11 gross total and 1 subtotal resection were achieved via TUFA without any mortality or morbidity. Comparative analyses of 4 surgical approaches to FV (TUFA, telovelar/cerebellomedullary fissure, supratonsillar/tonsillobiventral lobule fissure, and transvermian approaches) were also presented.

CONCLUSIONS

TUFA provides a direct route and excellent surgical view to lesions around the FV, particularly on dorsal and lateral aspects, inferior vermis, and medial part of the dentate nucleus and cerebellar peduncles. It minimizes traversing the normal cerebellar tissue compared with a transvermian approach.

Midline Suboccipital Endoscopic Transcerebellomedullary Fissure Keyhole Approach

OBJECTIVE

To study the endoscopic anatomy of the 4th ventricle and lateral brainstem regions via the midline suboccipital endoscopic transcerebellomedullary fissure keyhole approach assisted by a neuronavigation system and discuss the feasibility and indications of this approach.

MATERIALS AND METHODS

Craniotomy procedures performed via the midline suboccipital endoscopic transcerebellomedullary fissure keyhole approach were simulated on 8 adult cadaveric heads fixed by formalin, and the related anatomic structures in the 4th ventricles or around the brainstem were observed through the 0° endoscope or alternatively 30° one. A neuronavigation system was used to measure the exposed area of the floor of 4th ventricle, the maximum exposure range, the length of the floor of 4th ventricle, the shortest distance from the midpoint of posterior arch of atlas to the opening of the aqueduct in the 4th ventricle and to the jugular foramen on both sides, respectively.

RESULTS

All the anatomic structures within the 4th ventricle and partial anatomic landmarks around brainstem were identified by means of the midline suboccipital endoscopic transcerebellomedullary fissure keyhole approach. The exposed area of the floor of 4th ventricle is 459.68 ± 73.71 mm. However, the total exposed area is 1601.70 ± 200.76 mm. The length of the floor of 4th ventricle is 36.08 ± 2.63 mm. The shortest distance from the midpoint of posterior arch of atlas to the opening of the aqueduct in the 4th ventricle is 63.87 ± 2.97 mm, to the jugular foramen on both sides, respectively, is 40.11 ± 2.47 mm/40.30 ± 2.31 mm.

CONCLUSIONS

Midline suboccipital endoscopic transcerebellomedullary fissure keyhole approach can basically meet the medial and lateral route of the transcerebellomedullary fissure approach. A tumor within the 4th ventricle or near the jugular tubercle extending into the 4th ventricle through the cerebellomedullary fissure can be removed by this approach.

The surgical treatment of tumors of the fourth ventricle: a single-institution experience

OBJECTIVE

Fourth ventricle tumors are rare, and surgical series are typically small, comprising a single pathology, or focused exclusively on pediatric populations. This study investigated surgical outcome and complications following fourth ventricle tumor resection in a diverse patient population. This is the largest cohort of fourth ventricle tumors described in the literature to date.

METHODS

This is an 18-year (1993–2010) retrospective review of 55 cases involving patients undergoing surgery for tumors of the fourth ventricle. Data included patient demographic characteristics, pathological and radiographic tumor characteristics, and surgical factors (approach, surgical adjuncts, extent of resection, etc.). The neurological and medical complications following resection were collected and outcomes at 30 days, 90 days, 6 months, and 1 year were reviewed to determine patient recovery. Patient, tumor, and surgical factors were analyzed to determine factors associated with the frequently encountered postoperative neurological complications.

RESULTS

There were no postoperative deaths. Gross-total resection was achieved in 75% of cases. Forty-five percent of patients experienced at least 1 major neurological complication, while 31% had minor complications only. New or worsening gait/focal motor disturbance (56%), speech/swallowing deficits (38%), and cranial nerve deficits (31%) were the most common neurological deficits in the immediate postoperative period. Of these, cranial nerve deficits were the least likely to resolve at follow-up. Multivariate analysis showed that patients undergoing a transvermian approach had a higher incidence of postoperative cranial nerve deficits, gait disturbance, and speech/swallowing deficits than those treated with a telovelar approach. The use of surgical adjuncts (intraoperative navigation, neurophysiological monitoring) did not significantly affect neurological outcome. Twenty-two percent of patients required postoperative CSF diversion following tumor resection. Patients who required intraoperative ventriculostomy, those undergoing a transvermian approach, and pediatric patients (< 18 years old) were all more likely to require postoperative CSF diversion. Twenty percent of patients suffered at least 1 medical complication following tumor resection. Most complications were respiratory, with the most common being postoperative respiratory failure (14%), followed by pneumonia (13%).

CONCLUSIONS

The occurrence of complications after fourth ventricle tumor surgery is not rare. Postoperative neurological sequelae were frequent, but a substantial number of patients had neurological improvement at long-term followup. Of the neurological complications analyzed, postoperative cranial nerve deficits were the least likely to completely resolve at follow-up. Of all the patient, tumor, and surgical variables included in the analysis, surgical approach had the most significant impact on neurological morbidity, with the telovelar approach being associated with less morbidity.

Chiari I malformation: surgical technique, indications and limits

BACKGROUND

Chiari malformation type I (CM-I) is a rare disease characterised by herniation of cerebellar tonsils below the foramen magnum with associated anomalies of posterior fossa. We describe here the surgical technique, indications and limits of surgical treatment.

METHOD

The authors describe the surgical technique, including: posterior fossa decompression, opening of the foramen of Magendie and duraplasty in case of CM-I.

CONCLUSIONS

Posterior fossa decompression plus duraplasty is a safe and effective procedure for patients with CM-I malformation.

Endoscopic-Assisted Median Aperture Approach for Resection of Fourth Ventricular Tumor and Confirmation of Patency of Cerebral Aqueduct Using an Adjustable-Angle Endoscope: Technical Case Report

BACKGROUND AND IMPORTANCE: Open microsurgical approaches to the roof of the fourth ventricle via a telovelar approach typically require cerebellar retraction and/or splitting of the vermis and may be associated with postoperative neurological morbidities. In this case report and technical note, we describe the use of an adjustable-angle endoscope inserted into the median aperture via suboccipital craniotomy, resulting in enhanced visualization of the roof of the fourth ventricle and cerebral aqueduct and maximal safe tumor resection.

CLINICAL PRESENTATION: A 49-yr-old woman with obstructive hydrocephalus and a fourth ventricular mass that was not fully visible with the use of an operative microscope.

CONCLUSION: Direct visualization of the roof of the fourth ventricle, including the superior medullary velum and cerebral aqueduct, can be facilitated with an adjustable angle endoscope inserted into the median aperture via suboccipital craniotomy to minimize the degree of telovelar dissection and vermis splitting.

Posterior fossa syndrome with delayed MR evidence of unilateral superior cerebellar peduncle (SCP) damage

Posterior fossa syndrome (PFS) is a well-known sequela of midline posterior fossa tumor resection. Patients typically exhibit transient behavioral, motor, and oculomotor disturbances that resolve within a few weeks to several months after surgery. The underlying pathophysiology of PFS is not completely understood, but contemporary literature has implicated injury to the dentate nucleus and/or exiting dentatothalamocortical fiber bundles as a causative factor. The authors present a case of a young male who developed a delayed variant of PFS typified by motor deficits and demonstrated diffusion restriction in the ipsilateral superior cerebellar peduncle. Because the correlation between PFS and the superior cerebellar peduncle injury is poorly described in the literature, particularly with regard to relevant radiographic imaging, the authors of this report hope their findings will contribute to that insufficient body of evidence.

Tonsillobiventral fissure approach to the lateral recess of the fourth ventricle

OBJECTIVE Surgical access to the lateral recess of the fourth ventricle (LR) is suboptimal with existing transvermian and telovelar approaches because of limited lateral exposure, significant retraction of the cerebellar tonsil, and steep trajectories near brainstem perforator arteries. The goal in this study was to assess surgical exposure of the tonsillobiventral fissure approach to the LR, and to describe the relevant anatomy. METHODS Two formaldehyde-fixed cerebella were used to study the anatomical relationships of the LR. Also, the tonsillobiventral fissure approach was simulated in 8 specimens through a lateral suboccipital craniotomy. RESULTS The pattern of the cerebellar folia and the cortical branches of the posterior inferior cerebellar artery were key landmarks to identifying the tonsillobiventral fissure. Splitting the tonsillobiventral fissure allowed a direct and safe surgical trajectory to the LR and into the cerebellopontine cistern. The proposed approach reduces cervical flexion and optimizes the surgical angle of attack. CONCLUSIONS The tonsillobiventral fissure approach is a feasible and effective option for exposing the LR. This approach has more favorable trajectories and positions for the patient and the surgeon, and it should be added to the armamentarium for lesions in this location.

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.

Cerebellar mutism

INTRODUCTION

Cerebellar mutism (CM) is defined as a peculiar form of mutism that may complicate the surgical excision of posterior cranial fossa tumor. The incidence is variable in the literature, occurring in up to one third of cases in some series. Commonly occurring peculiar features of CM are delayed onset following surgery, limited duration, and spontaneous recovery usually associated with dysarthria.

METHODS

A review has been performed concerning anatomical substrates and circuits actually considered to be involved in the development of cerebellar mutism, as well as risk factors for its development that have been documented in the literature. Attention has also been given to the long-term prognosis and the possibilities of rehabilitation that can be considered in these children, which has been compared with the authors' institutional experience.

RESULTS AND CONCLUSIONS

Tumor infiltration of the brainstem seems to represent the most relevant feature related to the development of CM, along with the histological diagnosis of medulloblastoma. On the other hand, hydrocephalus does not represent an independent risk factor. The higher rate of CM in children seems to be related to the higher incidence in children of tumors with malignant histology and brain stem involvement. Surgical technique does not seem to have a definite role; in particular, the use of a telovelar approach as compared to vermian split to reach the fourth ventricle extension of the tumor has not been demonstrated to prevent the development of cerebellar mutism. Concerning long-term prognosis, around one third of the children who develop cerebellar mutism after surgery have a persistent dysarthria, the remaining ones showing a residual phonological impairment. Long-term dysarthric features tend to be more severe and less prone to recovery in children presenting at diagnosis with associated combined procedural memory and defective neurocognitive functions.