Transcerebellomedullary fissure approach to lesions of the fourth ventricle: less is more?

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.

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.

Median trans-atlanto-occipital membrane microsurgical approach to the posterior cranial fossa without craniotomy

Minimally invasive approaches are becoming increasingly popular and contributing to improving the results of the surgical treatment of a wide variety of intracranial pathologies. Fifteen patients with posterior cranial fossa tumors underwent microsurgery through the atlanto-occipital membrane without resection of any bone structures. Tumors were localized in the brainstem in 8 patients and in the fourth ventricle in 7 patients. According to preoperative MRI and CT scans, the distance between the posterior arch of the atlas and the opisthion ranged from 9.9 to 16.5 mm (median 13 mm). The surgery was performed with the patient in the prone position and the head flexed. The trajectory of the surgical approach was directed from the skin incision located above the C2 spinous process 3.5-4 cm rostral along the midline. Total tumor resection was performed in 10 patients, subtotal resection in 2 patients, partial resection in 1 patient, and open biopsy in 2 patients. Surgical complications occurred in only 1 patient (meningoencephalitis). This minimally invasive trans-atlanto-occipital membrane approach for posterior cranial fossa tumors provides adequate visualization of the caudal part of the fourth ventricle and brainstem when the anthropometric parameters of the patient are suitable.

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.

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.

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.

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

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

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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.

Modafinil in the rehabilitation of a patient with post-surgical posterior fossa syndrome: a lesson to be learned?

Disorders of the cerebellum may present with motor, cognitive, behavioral and affective symptoms. There is a growing interest in developing neuroanatomical models of symptoms generation that involve the cerebellum and the cerebello-cortical connections. We describe an exciting first case report of successful use of Modafinil in an adult patient with post-operative posterior fossa syndrome. Following resection of a melanoma metastasis in the cerebellum the patient developed striking affective and behavioral symptoms in the form of withdrawn flat mood and disengagement. This neurobehavioral presentation severely impacted on his quality of life, independence, and ability to engage in the neuro-rehabilitative program. Pharmacological treatment with Modafinil ameliorated these emotional and behavioral aspects, and also fatigue. Treatment with Modafinil hence affected recovery and outcome for the patient. To our knowledge, this is the first description of a successful pharmacological intervention in an adult with post-surgical posterior fossa syndrome and negative neurobehavioral presentation. Our findings illustrate the variability of the presentation of post-operative posterior fossa syndrome in adults, and the importance of delivering targeted treatment to maximize the benefits of neurorehabilitation. The manuscript highlights the following points: 1. post-operative consequences currently under the wide umbrella of posterior fossa syndrome, can indeed manifest in adults; 2. a wide spectrum of neurobehavioral symptoms can occur, including a presentation with predominantly negative features; 3. the type of neurobehavioral presentation should guide the treatment choice with particular consideration of drugs that potentially modulate the cerebello-frontal connections; 4. Modafinil can be a candidate for effective treatment in presentations with predominantly negative behavioral symptoms.

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.

Non-surgical transient cerebellar mutism-case report and systematic review

INTRODUCTION

Transient cerebellar mutism has been well recognized in literature as a complication of posterior fossa tumor resection. It is marked by profound impairment of fluency, articulation, and modulation of speech, irritability and autistic features and typically resolves within days to months. Underlying pathophysiology is debated, but currently unknown.

METHODS

We present a case of a child with similar clinical findings after cerebellitis, demonstration of diffuse cerebellar signal changes, swelling, and protruding tonsils at the level of foramen magnum.

DISCUSSION

To support the hypothesis that this clinical syndrome may occur in a non-surgical context, we present a review of literature of non-surgical transient cerebellar mutism.

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.

The midline suboccipital subtonsillar approach to the cerebellomedullary cistern: how I do it

BACKGROUND

Lesions lateral to the lower brainstem in an area extending from the foraminae of Luschka to the foramen magnum are rare and include different pathologies. There is no consensus on an ideal surgical approach.

METHOD

To gain access to this area, we use the midline suboccipital subtonsillar approach (STA). This midline approach with unilateral retraction of the cerebellar tonsil enables entry into the cerebellomedullary cistern.

CONCLUSIONS

The STA offers excellent access with a panoramic view of the cerebellomedullary cistern and its structures and therefore can be useful for a number of different pathologies in the lower petroclival area.

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.

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.

Microsurgical management of pediatric ependymomas of the fourth ventricle via the trans-cerebellomedullary fissure approach: A review of 26 cases

In the present study, the microsurgical management of 26 ependymomas of the fourth ventricle in children via the trans-cerebellomedullary fissure (CMF) approach was reviewed and evaluated. Clinical data were obtained from 26 ependymomas of the fourth ventricle treated with microsurgery using the trans-CMF approach from March 2006 to September 2010 at the Department of Neurosurgery of The First Affiliated Hospital of China Medical University (Shenyang, China). These data were collected and analyzed. Suboccipital median posterior fossa craniotomy and trans-CMF approach were performed in all cases for the microsurgical removal of the tumors. An additional incision was performed in the inferior medullary velum of 5 patients, in order to obtain adequate exposure of the tumors. As a result, all tumors were well exposed during surgery. Gross total resection (GTR) was achieved in 22 cases, near total resection (NTR) in 3 cases and subtotal resection (STR) in 1 case. All excised tumors were pathologically confirmed. No mortality occurred intraoperatively, and no patient presented with mutism or any other surgery-related complications. One patient suffered from postoperative hydrocephalus and received ventriculoperitoneal shunting, which relieved the symptoms. Over the 3.0-7.5-year follow-up period (mean, 4.8 years), tumor relapse occurred in 1 case with GTR, 2 cases with NTR and 1 case with STR. In total, 3 patients succumbed to tumor relapse and 4 were lost to follow-up. According to the literature and the clinical experience of the present authors, the trans-CMF approach provides safe and sufficient access to the fourth ventricle without the requirement of an incision in the inferior vermis. This approach prevents damage to the normal cerebellum and improves the surgical outcome. Tumor removal, restoration of cerebrospinal fluid circulation and preservation of brainstem function are factors that should be taken into consideration during surgery. For patients with residual tumors, adjuvant radiotherapy and/or chemotherapy may be beneficial.

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.

Telo-velar approach to fourth-ventricle tumours: how I do it

BACKGROUND

The "telo-velar" approach is an alternative to cerebellar splitting to gain access to the fourth ventricle through the so-called cerebello-medullary fissure (CMF).

METHOD

In this approach, the CMF is exposed and access to the ventricle is obtained by incising the tela chorioidea and inferior medullary velum. This approach enables the exploration of the entire ventricle cavity from the obex to the aqueduct.

CONCLUSIONS

The exposure of the fourth ventricle is satisfactory and the floor of the fourth ventricle can be visualised early and protected. The extent of resection and outcome are satisfactory in most patients, including those with large tumours or lesions attached to the lateral or superolateral recesses of the ventricle. The deep rostral tumour attachment is the main limitation of the telo-velar approach.

KEY POINTS

• Early exposure of the interface lesion-floor of the fourth ventricle favours a safer tumour dissection. • We feel that resection of tonsils is not necessary in the surgical setting. • The posterior arch of C1 should be removed only if the tonsils are below the level of the foramen magnum. • The improved access to the lateral recess of the ventricle makes the telo-velar approach particularly effective in lesions attached to cerebellar peduncles. • The wide dissection of the cerebello-medullary fissure and gentle tonsils retraction may prevent from the occurrence of cerebellar mutism or other major cerebellar dysfunctions. • Even the bilateral opening of the CMF does not result in cerebellar mutism if wide and cautious dissection, avoiding retraction and vascular injuries, is obtained. • The exposure of the fourth ventricle was satisfactory also in patients harbouring lesions attached to the lateral or even the superolateral recesses of the ventricle. • A deep rostral tumour attachment seems to be, at least in our experience, the main specific limitation of the telo-velar approach. • The risk of hydrocephalus can be reduced by opening of the fissure bilaterally, exposing the aqueduct, and by cisterna magna-fourth ventricle communication augmentation. • The EVD is taken in place for 48-72 h to prevent possible abrupt increase of the intracranial pressure and to favour wound closure.

Exposure of wide cerebellomedullary cisterns for vascular lesion surgeries in cerebellomedullary cisterns: opening of unilateral cerebellomedullary fissures combined with lateral foramen magnum approach

OBJECTIVE

To clarify microsurgical anatomic features of the cerebellomedullary fissure (CMF), the natural cleavage plane between the cerebellum and the medulla, and its relationship to the cerebellomedullary cistern (CMC) and to describe a surgical technique that uses the unilateral trans-CMF approach for CMC surgeries.

METHODS

In the anatomic study, 2 formalin-fixed cadaver heads were used. In the clinical study, 3 patients with vertebral artery-posterior inferior cerebellar artery aneurysms and 3 patients with glossopharyngeal neuralgia were surgically treated through the unilateral trans-CMF approach combined with the transcondylar fossa approach, which is a lateral foramen magnum approach.

RESULTS

The CMC was present at the lateral end of the CMF. The CMF was closed by arachnoidal adhesion, and the cerebellar hemisphere was superiorly attached to the cerebellar peduncle. After the unilateral CMF was completely opened, the cerebellar hemisphere was easily retracted rostrodorsally. Clinically, almost completely opening the unilateral CMF markedly enabled the retraction of the biventral lobule to obtain a wide surgical field safely for vascular CMC lesions. We present 2 representative cases.

CONCLUSION

Combined unilateral trans-CMF/lateral foramen magnum approaches provide a wide and close surgical field in the CMC, allowing easy and safe CMC surgery.