Surgery on anterior foramen magnum meningiomas using a conventional posterior suboccipital approach: a report on an experience with 17 cases

Ovoid Foramen Magnum Shape is Associated with Increased Complications and Decreased Extent of Resection for Anterolateral Foramen Magnum Meningiomas

Background  Antero-laterally located meningiomas of the foramen magnum (FM) pose significant surgical resection challenges. The effect of FM shape on surgical resection of FM meningiomas has not been previously studied. The present study investigates how FM shape effects the extent of tumor resection and complication rates in antero-lateral FM meningiomas. Materials and Methods  This retrospective study included 16 consecutive patients with antero-lateral FM meningiomas operated on by a single surgeon. FMs were classified as ovoid ( n  = 8) and nonovoid ( n  = 8) using radiographic evaluation. Results  Sixteen patients were examined: seven males and nine females (mean age of 58.5, and range of 29 to 81 years). Gross total resection was achieved in 81% of patients, with tumor encased vertebral arteries in 44%. Patient characteristics were similar including age, sex, preoperative tumor volume, relationship of vertebral artery with tumor, preoperative Karnofsky performance score (KPS), symptom duration, and presence of lower cranial nerve symptoms. The ovoid FM group had lower volumetric extents of resection without statistical significance (93 ± 10 vs. 100 ± 0%, p  = 0.069), more intraoperative blood loss (319 ± 75 vs. 219 ± 75 mL, p  = 0.019), more complications per patient (1.9 ± 1.8 vs. 0.3 ± 0.4, p  = 0.039), and poorer postoperative KPS (80 ± 21 vs. 96 ± 5, p  = 0.007). Hypoglossal nerve palsy was more frequent in the ovoid FM group (38 vs. 13%). Conclusion  This is the first study demonstrating that ovoid FMs may pose surgical challenges, poorer operative outcomes, and lower rates of extent of resection. Preoperative radiological investigation including morphometric FM measurement to determine if FMs are ovoid or nonovoid can improve surgical planning and complication avoidance.

Foramen magnum meningioma: Series of 20 cases. Complications, risk factors for relapse, and follow-up

Introduction:

Meningiomas account for 2.2% to 2.5% of all cerebral tumors, of which only 2% are located in the foramen magnum. Foramen magnum meningiomas (FMMs) are commonly found in women, with a mean age at onset of 52 years old. They generally behave more aggressively than other meningiomas.

Materials and Methods:

We performed epidemiological, anatomical and surgical analyses of 20 patients diagnosed with FMMs who underwent surgical treatment from 1999 to 2019 at Santa Paula Hospital in Sao Paulo. This case series was compared with previously published ones to better understand this relatively rare disease.

Results:

Twenty patients were included, with a mean follow-up of 110 months. Their mean age was 37.8 years old. The mean preoperative Karnofsky performance status scale (KPS) was 84%. We found a female (65%) and left hemisphere predominance (50%). Involvement of both hemispheres was found in 25% of patients. FMM locations were anterior, anterolateral, lateral and posterior, in 45%, 35%, 10%, and 10%, respectively. Simpson resection grades I, II, and III were achieved in 25%, 60%, and 15% of cases, respectively. Mean postoperative KPS was 79%. Three patients with anterior and bilateral located meningiomas had a worse postoperative KPS in comparison to the preoperative one.

Conclusion:

Anterior and bilateral FMMs seem to be related to a worse prognosis. A gross total resection can reduce the recurrence rates. The KPS is worse in patients with recurrence.

An investigation of craniocervical stability post-condylectomy

Background:

Occipital condylectomy is often necessary to gain surgical access to various neurological pathologies. As the lateral limit of the craniovertebral junction (CVJ), partial condylectomy can lead to iatrogenic craniocervical instability. What was once considered an inoperable location is now the target of various complex neurosurgical procedures such as tumor resection and aneurysm clipping.

Methods:

In this study, we will review the anatomical structure of the CVJ and provide the first comprehensive assessment of studies investigating craniovertebral stability following condylectomy with the transcondylar surgical approaches. Furthermore, we discuss future considerations that must be evaluated to optimize the chances of preserving craniocervical stability postcondylectomy.

Results:

The current findings postulate upward of 75% of the occipital condyle can be resected without significantly affecting mobility of the CVJ. The current findings have only examined overall dimensions and have not established a significant correlation into how the shape of the occipital condyles can affect mobility. Occipitocervical fusion should only be considered after 50% condyle resection. In terms of indicators of anatomical stability, components of range of motion (ROM) such as the neutral zone (NZ) and the elastic zone (EZ) have been discussed as potential measures of craniocervical mobility. These components differ by the sense that the NZ has little ligament tension, whereas the EZ does represent ROM where ligaments experience tension. NZ is a more sensitive indicator of instability when measuring for instability postcondylectomy.

Conclusion:

Various transcondylar approaches have been developed to access this region including extreme-lateral and far-lateral condylectomy, with hopes of preserving as much of the condyle as possible and maintaining postoperative craniocervical stability.

Foramen magnum meningiomas: a systematic review and meta-analysis

Foramen magnum meningiomas (FMMs) account for 1.8–3.2% of all meningiomas. With this systematic review and meta-analysis, our goal is to detail epidemiology, clinical features, surgical aspects, and outcomes of this rare pathology. Using PRISMA 2015 guidelines, we reviewed case series, mixed series, or retrospective observational cohorts with description of surgical technique, patient and lesion characteristics, and pre- and postoperative clinical status. A meta-analysis was performed to search for correlations between meningioma characteristics and rate of gross total resection (GTR). We considered 33 retrospective studies or case series, including 1053 patients, mostly females (53.8%), with a mean age of 52 years. The mean follow-up was of 51 months (range 0–258 months). 65.6% of meningiomas were anterior, and the mean diameter was of 29 mm, treated with different surgical approaches. Postoperatively, 17.2% suffered complications (both surgery- and non-surgery-related) and 2.5% had a recurrence. The Karnofsky performance score improved in average after surgical treatment (75 vs. 81, p < 0.001). Our meta-analysis shows significant rates of GTR in cohorts with a majority of posterior and laterally located FMM (p = 0.025) and with a mean tumor less than 25 mm (p < 0.05). FMM is a rare and challenging pathology whose treatment should be multidisciplinary, focusing on quality of life. Surgery still remains the gold standard and aim at maximal resection with neurological function preservation. Adjuvant therapies are needed in case of subtotal removal, non-grade I lesions, or recurrence. Specific risk factors for recurrence, other than Simpson grading, need further research.

Far-Lateral Approach for Ventral and Ventrolateral Upper Cervical Meningiomas: A Case Series and Literature Review

STUDY DESIGN

Retrospective cohort study.

PURPOSE

To evaluate the safety and efficacy of the far-lateral approach in the resection of ventral and ventrolateral upper cervical meningiomas.

OVERVIEW OF LITERATURE

Upper cervical meningiomas are a common disease entity. These lesions can be surgically treated via many accesses. The far-lateral approach is a very appealing technique for these lesions.

METHODS

We assessed 23 patients with a mean age of 57.3±15 years. According to the Japanese Orthopedic Association (JOA) scale; eight patients had grade 0, nine had grade I, and six had grade II. All patients underwent plain radiography and magnetic resonance imaging of the cervical spine. The foramen magnum was involved in 10 patients, C1-2 in seven, C2-3 in four, and C3-4 in two. All patients were operated via the far-lateral approach.

RESULTS

Gross total resection was achieved in 21 patients. Sixteen lesions were psammomatous, five were fibroblastic, and two were meningothelial meningiomas. The mean operative duration was 135±40 minutes, while the mean operative blood loss was 450±210 mL, and the mean hospital stay was 4.3±2.2 days. At the final follow-up that was conducted at 27.6±21 months and as per the JOA score; 16 patients were classified into grade 0 and 7 into grade II. The condition of none of our patients deteriorated postoperatively. There was no significant correlation of the clinical outcome with tumor level, pathological subtype of the tumor, symptom duration, age, and sex. There was no significant correlation of tumor resection completeness with tumor level, tumor pathological subtype, or tumor topography (ventral or ventrolateral).

CONCLUSIONS

The far-lateral approach is a safe and effective access for ventral and ventrolateral cervical meningiomas. It allows direct access to tumor with no spinal cord or nerve roots traction, and thus may yield a fairly better outcome than the standard posterior approach.

External syringomyelia in longstanding benign foramen magnum tumors

BACKGROUND

The effect of benign foramen magnum tumours on cranial and spinal dimensions and cerebrospinal fluid (CSF) spaces is unclear. In this study, we measured alterations in cerebrospinal fluid (CSF) spaces in the spinal canal and in the posterior cranial fossa distant from the site of benign foramen magnum tumors.

METHODS

Twenty-nine magnetic resonance imaging scans of patients with foramen magnum tumors (8 meningiomas and 21 C2 neurinomas) were identified for radiological morphometric analysis and compared with normal control scans. The anterior-posterior distance between the pontomedullary junction and the clivus, the spinal canal diameter, spinal cord diameter, and cord-canal ratios were measured at the C6 and T2 levels.

RESULTS

The mean spinal canal diameter was significantly higher in tumor scans at both the C6 and T2 spinal levels than in controls (13.8 mm vs. 11.4 mm at C6; p<0.0001, and 12.9 mm vs. 11.9 mm at T2; P=0.01). Further, the mean cord:canal ratio was significantly lower in tumor scans at both levels (0.49 vs. 0.64 at C6; P<0.0001, and 0.45 vs. 0.54 at T2; P=0.0009). There was no significant difference in mean anteroposterior distance from the clivus to the pontomedullary junction (10.4 mm vs. 10.3 mm; P=0.91).

CONCLUSION

In the presence of benign foramen magnum tumors, the spinal canal diameter and CSF volume in the spinal canal increased at the C6 and T2 levels, distant from the tumor site, a phenomenon we describe as "external syringomyelia".

Our surgical experience in foramen magnum meningiomas: clinical series of 11 cases

INTRODUCTION

We aimed to discuss surgical approaches and results that we applied foramen magnum meningiomas.

METHODS

We retrospectively investigated 11 foramen magnum meningioma cases, who had been operated between the dates of February 2012 and March 2017.

RESULTS

Eight of the patients were females and 3 of the patients were males, the age range was 32-75 and the age average was 60.8. 5 of the tumors were anatomically localized as posterolateral, 2 of them were localized as anterolateral, 2 of them were localized as lateral and 2 of them were localized as anterior according to the brain stem or spinal cord. Posterior far lateral (4 patients) approach including C1 laminoplasty (7 patients) and 1/3 condyle resection was surgically applied to the patients with median suboccipital craniotomy. Gross total excision was applied to 82% of the patients (9 patients) and subtotal mass excision was applied to 18% (2 patients) of the patients. The most frequent post-operative complications were temporary lower cranial nerve (CN IX and X ) palsy in our 2 anterior localized cases (18%) and also cerebrospinal fluid (CSF) fistula in our 1 anterior localized case with difficulty in swallowing (dysphagia). Karnofsky scores of the patients, who were followed for 18 months in post-operative 12 and 48 months of average, in the last follow-up were 80 and no post-operative mortality occurred.

CONCLUSION

Posterior midline suboccipital and far lateral approaches that we apply in our own series were appropriate approaches for foramen magnum meningiomas.

Surgical Outcomes, Complications, and Management Strategies for Foramen Magnum Meningiomas

Objectives  Foramen magnum meningiomas (FMM) are complex lesions because of their proximity to the brain stem and posterior cerebrovasculature. The objective of this study is to report surgical outcomes and complications after resection of FMM. Methods  A retrospective chart review was conducted on patients with FMM from 1998 to 2015. Univariate logistic regression and recursive partitioning analysis were used to identify risk factors associated with complications and extent of resection (EOR). Results  We identified 28 patients with FMM. Median follow-up was 5.9 years. Tumors were World Health Organization grade I (92.9%) or grade II (7.1%). The vertebral artery was completely encased (25%), partially encased (11%), or not encased (64%). Median size was 11.9 cm 3 . EOR was gross total (39%) and subtotal (61%). The observed recurrence rate was 4% ( n  = 1). There were 38 complications in 12 patients (43%), and 6 patients (21%) had complications requiring additional surgery. Complications included cerebrospinal fluid leak/hydrocephalus ( n  = 7, 25%), weakness ( n  = 4, 14%), numbness ( n  = 4, 14%), and cranial nerve deficits: IX, X ( n  = 4, 14%), XI ( n  = 2, 7%), XII ( n  = 5, 18%). Medical complications included pneumonia ( n  = 1, 4%) and meningitis ( n  = 1, 4%). Tumor volume greater than 14 cm 3 (odds ratio [OR] = 21.7, p  = 0.0010), any vertebral artery encasement (OR 6.1, p  = 0.0386), and subtotal resection (OR 6.4, p  = 0.0398) were significantly associated with complications. Tumor volume greater than 14 cm 3 was also significantly associated with subtotal resection (OR 8.3, p  = 0.0201). Conclusions  Resection of FMM carries perioperative morbidity that increases with larger tumor size. Despite the morbidity, long-term recurrence-free survival is achievable with maximal safe resection and adjuvant radiation.

Lateral suboccipital retrosigmoid retrocondylar approach for foramen magnum meningiomas

Objective

The objective of the study was to describe our approach and the surgical technique and analyze its safety and the outcome for foramen magnum meningiomas (FMMs).

Methods

From 1986 to 2016, 15 FMM patients were operated on using the lateral suboccipital retrocondylar approach.

Results

In this series, there were 12 (80%) female and 3 (20%) male patients. The patients ranged in age from 33 to 63 years. There was no operative dead, but two patients died during the follow-up period, which varied from 1 to 24 years (mean, 10.2 years). Twelve patients (80%) achieved Glasgow Outcome Scale 4 or 5. Gross total resection was achieved in 13 (86.6.7%) patients.

Conclusions

The majority of FMM can be safely removed using the lateral suboccipital retrocondylar approach without condylar resection, associated to meticulous microsurgical technique.

Foramen magnum meningioma's management: the experience of the department of neurosurgery in Marrakesh

Our study is a retrospective analysis of the clinical data, surgical outcomes, histological finding and prognosis of foramen magnum meningiomas through a serie of 8 cases operated at the department of neurosurgery at Mohammed VI medical university hospital, Marrakesh. From January 2002 to December 2015. There were 3 male and 5 female patients (mean age, 46.75 years). Cervico-occipital pain (100%) and motor deficit (100%) were the most common presenting symptoms. MRI was the most appropriate diagnostic tool in visualizing tumors of this region. All operations were performed by the posterior approach and gross total resection was achieved in 7 cases. Surgical mortality was 20%. 3 other patients had complications like CSF leak (25%), meningitis (12,5%) and transient worsening of neurological deficit (12.5%) but made neurological recovery later. Foramen magnum meningiomas have long been regarded as difficult lesions both in terms of diagnosis and management. However, with the availability of MR imaging, newer surgical techniques and skull base exposures, the excision of these lesions is becoming easier and safer.

Fully Endoscopic Minimally Invasive Transrectus Capitis Posterior Muscle Triangle Approach to the Posterolateral Condyle and Jugular Tubercle

Background  We evaluated a transrectus capitis posterior muscle triangle approach to the posterolateral foramen magnum, occipital condyles, jugular tubercle, and the fourth ventricle. We also assessed factors that affect the amount of bone removal required. Objective  To evaluate if the proposed approach is as effective as standard open approaches to expose the lateral portion of the foramen magnum. Methods  The proposed minimally invasive fully endoscopic approach was performed in 15 cadaveric specimens using 4-mm (0- and 45-degree) endoscopes. Results  Using a 5-cm straight paramedian incision, the rectus capitis posterior minor and major muscles were partially removed unilaterally, providing a corridor through the muscles to reach the foramen magnum region. After meticulous soft tissue dissection, key anatomical landmarks can be identified such as the greater occipital nerve, the vertebral artery that wraps around the atlanto-occipital joint, and the bony protuberance that heralds the occipital condyle. A suboccipital craniotomy associated with the transcondylar, supracondylar or paracondylar approach is performed depending on the amount of bone removal desired to maximize the surgical view. By doing so, the jugular foramen can be exposed laterally as well as the fourth ventricle medially. Conclusion  The proposed endoscopic approach can provide access through the transrectus capitis posterior muscle triangle leading directly to the occipital condyle. A stepwise approach is critical to gain a surgical corridor to the inferolateral petroclival region and the fourth ventricle.

Foramen Magnum Meningioma: a Case Report and Review of Literature

Introduction:

Meningiomas are slow-growing benign tumors that arise at any location where arachnoid cells reside. Although meningiomas account for a sizable proportion of all primary intracranial neoplasms (14.3–19%), only 1.8 to 3.2% arise at the foramen magnum. Their indolent development at the craniocervical junction makes clinical diagnosis complex and often leads to a long interval between onset of symptoms and diagnosis.

Case report:

We report a case of a 79-year-old male patient, presented with ataxia and sense of threatening fainting during verticalization. Magnetic resonance imaging revealed the presence of meningioma in the right side of craniospinal junction.

The anatomical perspective of human occipital condyle in relation to the hypoglossal canal, condylar canal, and jugular foramen and its surgical significance

Background:

The transcondylar approach (TCA) has gained importance in recent era which enables shorter and direct route to access the lesions ventral to the brainstem. The important step in this approach is resection of the occipital condyle (OC). The detailed knowledge of bony anatomy of OC and its relation to the hypoglossal canal (HC), condylar canal (CC), and jugular foramen (JF) is very important to avoid any iatrogenic injury during craniovertebral surgeries. The aim of the present study is to conduct a morphometric and morphological study and note the variations of the OC and the structures surrounding it in North Indian population.

Materials and Methods:

The study was carried out on 100 OC. Morphometric measurements of OC and the distances of HC and JF from the posterior end of OC were noted. In addition, the extent of the HC and JF in relation to OC, presence or absence of CC, shape of the OC, and its articular facet were also noted.

Results:

The incidence of short OC was seen in 13% skulls. The most common shape of OC was oval or rhomboid. Even though the articular facet was convex in majority of skulls but flat (10%) and concave (1%) were also observed. The external and internal distance of HC from the posterior end of OC was13.83 mm and 10.66 mm on the right side and 15.02 mm and 11.89 mm on the left side. The OC was related in its middle 1/3 to the HC in 15% skulls and to the whole extent of JF in 3% skulls. Thirty-four percent skulls displayed the septa in the HC. The CC was present bilaterally in 38% skulls and unilaterally in 40% skulls.

Conclusion:

The OC and related structures such as HC, CC, and JF are likely to have variations in respect to morphometry and morphology. This study may prove helpful to neurosurgeons operating in this field, especially during TCA where neurovascular structures emerging from these canals and foramen are more vulnerable to injury.

Craniovertebral junction 360°: A combined microscopic and endoscopic anatomical study

Objectives:

Craniovertebral junction (CVJ) can be approached from various corridors depending on the location and extent of disease. A three-dimensional understanding of anatomy of CVJ is paramount for safe surgery in this region. Aim of this cadaveric study is to elucidate combined microscopic and endoscopic anatomy of critical neurovascular structures in this area in relation to bony and muscular landmarks.

Materials and Methods:

Eight fresh-frozen cadaveric heads injected with color silicon were used for this study. A stepwise dissection was done from anterior, posterior, and lateral sides with reference to bony and muscular landmarks. Anterior approach was done endonasal endoscopically. Posterior and lateral approaches were done with a microscope. In two specimens, both anterior and posterior approaches were done to delineate the course of vertebral artery and lower cranial nerves from ventral and dorsal aspects.

Results:

CVJ can be accessed through three corridors, namely, anterior, posterior, and lateral. Access to clivus, foreman magnum, occipital cervical joint, odontoid, and atlantoaxial joint was studied anteriorly with an endoscope. Superior and inferior clival lines, supracondylar groove, hypoglossal canal, arch of atlas and body of axis, and occipitocervical joint act as useful bony landmarks whereas longus capitis and rectus capitis anterior are related muscles to this approach. In posterior approach, spinous process of axis, arch of atlas, C2 ganglion, and transverse process of atlas and axis are bony landmarks. Rectus capitis posterior major, superior oblique, inferior oblique, and rectus capitis lateralis (RCLa) are muscles related to this approach. Occipital condyles, transverse process of atlas, and jugular tubercle are main bony landmarks in lateral corridor whereas RCLa and posterior belly of digastric muscle are the main muscular landmarks.

Conclusion:

With advances in endoscopic and microscopic techniques, access to lesions and bony anomalies around CVJ is becoming easier and straightforward. A combination of microscopic and endoscopic techniques is more useful to understand this anatomy and may aid in the development of future combined approaches.

Gamma Knife radiosurgery for posterior fossa meningiomas: a multicenter study

OBJECT

Posterior fossa meningiomas represent a common yet challenging clinical entity. They are often associated with neurovascular structures and adjacent to the brainstem. Resection can be undertaken for posterior fossa meningiomas, but residual or recurrent tumor is frequent. Stereotactic radiosurgery (SRS) has been used to treat meningiomas, and this study evaluates the outcome of this approach for those located in the posterior fossa.

METHODS

At 7 medical centers participating in the North American Gamma Knife Consortium, 675 patients undergoing SRS for a posterior fossa meningioma were identified, and clinical and radiological data were obtained for these cases. Females outnumbered males at a ratio of 3.8 to 1, and the median patient age was 57.6 years (range 12-89 years). Prior resection was performed in 43.3% of the patient sample. The mean tumor volume was 6.5 cm(3), and a median margin dose of 13.6 Gy (range 8-40 Gy) was delivered to the tumor.

RESULTS

At a mean follow-up of 60.1 months, tumor control was achieved in 91.2% of cases. Actuarial tumor control was 95%, 92%, and 81% at 3, 5, and 10 years after radiosurgery. Factors predictive of tumor progression included age greater than 65 years (hazard ratio [HR] 2.36, 95% CI 1.30-4.29, p = 0.005), prior history of radiotherapy (HR 5.19, 95% CI 1.69-15.94, p = 0.004), and increasing tumor volume (HR 1.05, 95% CI 1.01-1.08, p = 0.005). Clinical stability or improvement was achieved in 92.3% of patients. Increasing tumor volume (odds ratio [OR] 1.06, 95% CI 1.01-1.10, p = 0.009) and clival, petrous, or cerebellopontine angle location as compared with petroclival, tentorial, and foramen magnum location (OR 1.95, 95% CI 1.05-3.65, p = 0.036) were predictive of neurological decline after radiosurgery. After radiosurgery, ventriculoperitoneal shunt placement, resection, and radiation therapy were performed in 1.6%, 3.6%, and 1.5%, respectively.

CONCLUSIONS

Stereotactic radiosurgery affords a high rate of tumor control and neurological preservation for patients with posterior fossa meningiomas. Those with a smaller tumor volume and no prior radiation therapy were more likely to have a favorable response after radiosurgery. Rarely, additional procedures may be required for hydrocephalus or tumor progression.

Extramedullary foramen magnum tumors and their surgical management: An experience with 29 cases

Introduction:

Surgical management of foramen magnum (FM) tumors is challenging by virtue of their location and vital neurovascular relationships. The ideal approach to anterior/anterolateral tumors continue to evoke controversy even in the modern era. In this article, we present and discuss our experience in the surgical management of these tumors.

Materials and Methods:

This retrospective study includes 29 consecutive patients (mean age 36.6 years, M: F = 2.63:1) of extramedullary tumors at the surgical foramen magnum, operated at our center, between 2007 and 2012.

Results:

Their mean duration of symptoms was 14. 6 months. A majority of the patients presented with motor symptoms (quadri/paraparesis, n = 21, 72.4%), neck pain with/without suboccipital radiation (n = 16, 55.2%) and sensory symptoms like tingling/numbness (n = 16, 55.2%). There were nine extradural (31%) and 20 intradural tumors (69%). Most of the tumors were located posterolateral to the neuraxis (n = 13, 44.8%). Nerve sheath tumors (n = 11, 38%) and meningiomas (n = 5, 17.2%) were the most commonly encountered histologies in our series. The standard posterior approach was the most frequently employed surgical approach (n = 20, 69%). Operative mortality and morbidity were 3.4 and 18.9%, respectively. At a mean follow-up of 27.3 months, 13 out of the 18 available patients improved.

Conclusion:

A majority of the foramen magnum tumors are amenable to excision via the standard posterior approach. Small anterior dural-based meningiomas/recurrent tumors may require a lateral approach like the far lateral approach.

Quantitative Anatomical Study of Tailored Far-Lateral Approach for the VA-PICA Regions

Objective The extent of the far-lateral approach (FLA) has not yet been quantified for the region of the vertebral and posterior inferior cerebellar arteries (VA-PICA). We quantitatively analyzed six main sequential steps of the FLA. Methods A modified small FLA (msFLA) and a classic large FLA (clFLA) were performed sequentially on both sides of five cadaveric heads. A frameless navigational system was used to quantify the angle of attack for the origin (T1) and lateral medullary segment (T2) of the PICA and the surgical area of exposure above and below the vagus nerve (cranial nerve [CN] X). Results The total area of exposure above CN X increased significantly (p < 0.05) from the msFLA to the clFLA. However, the surgical exposure area below CN X did not change (p > 0.05). C1 hemilaminectomy increased (p < 0.05) the vertical angle of attack, and drilling the posteromedial third of the occipital condyle increased (p < 0.05) the horizontal angle of attack to the origin of the PICA. Conclusions For the VA-PICA region, the msFLA offered a similar practical surgical working area and similar angles of attack when compared with the clFLA. The FLA should be tailored based on the location, size, and pathology of lesions and on the exposure required for effective surgical treatment.

The far-lateral approach for foramen magnum meningiomas

Foramen magnum meningiomas (FMMs) are slow growing, most often intradural and extramedullary tumors that pose significant challenges to the skull base neurosurgeon. The indolent clinical course of FMMs and their insidious onset of symptoms are important factors that contribute to delayed diagnosis and relative large size at the time of presentation. Symptoms are often produced by compression of surrounding structures (such as the medulla oblongata, upper cervical spinal cord, lower cranial nerves, and vertebral artery) within a critically confined space. Since the initial pathological description of a FMM in 1872, various surgical approaches have been described with the aim of achieving radical tumor resection. The surgical treatment of FMMs has evolved considerably over the last 4 decades due to the progress in microsurgical techniques and development of a multitude of skull base approaches. Posterior and posterolateral FMMs can be safely resected via a standard midline suboccipital approach. However, controversy still exits regarding the optimal management of anterior or anterolateral lesions. Independently of technical variations and the degree of bone removal, all modern surgical approaches to the lower clivus and anterior foramen magnum derive from the posterolateral (or far-lateral) craniotomy originally described by Roberto Heros and Bernard George. This paper is a review of the surgical management of FMMs, with emphasis on the far-lateral approach and its variations. Clinical presentation, imaging findings, important neuroanatomical correlations, recurrence rates, and outcomes are discussed.

Conventional Posterior Approach without Far Lateral Approach for Ventral Foramen Magnum Meningiomas

Objective

We present our experience of conventional posterior approach without fat lateral approach for ventral foramen magnum (FM) meningioma (FM meningioma) and tried to evaluate the approach is applicable to ventral FM meningioma.

Methods

From January 1999 to March 2011, 11 patients with a ventral FM meningioma underwent a conventional posterior approach without further extension of lateral bony window. The tumor was removed through a working space between the dura and arachnoid membrane at the cervicomedullary junction with minimal retraction of medulla, spinal cord or cerebellum. Care should be taken not to violate arachnoid membrane.

Results

Preoperatively, six patients were of Nurick grade 1, three were of grade 2, and two were of grade 3. Median follow-up period was 55 months (range, 20-163 months). The extent of resection was Simpson grade I in one case and Simpson grade II in remaining 10 cases. Clinical symptoms improved in eight patients and stable in three patients. There were no recurrences during the follow-up period. Postoperative morbidities included one pseudomeningocele and one transient dysphagia with dysarthria.

Conclusion

Ventral FM meningiomas can be removed gross totally using a posterior approach without fat lateral approach. The arachnoid membrane can then be exploited as an anatomical barrier. However, this approach should be taken with a thorough understanding of its anatomical limitation.

Primary calcified rhabdoid meningioma of the cranio-cervical junction: A case report and review of literature

Rhabdoid meningioma (RM) is a relatively new, rare, and aggressive subtype of meningioma, classified as Grade III malignancy in 2000, 2007 versions of WHO classification of the central nervous system. We reviewed the data available from all published cases of RMs. To the best of our knowledge, there are more than 100 published cases of RMs; none have documented extensive calcification or origin from the cranio cervical junction. We report the first case of a totally calcified (stony mass), primary RM, at the cranio cervical junction. Also, we highlighted the role of the transcondylar approach to achieve microscopic total removal of such a challenging lesion. A 37 year old female, allergic to erythromycin, presented with 5 years of progressive right upper extremity numbness and weakness, right facial numbness, and occipital pain. Imaging demonstrated a large calcified mass at the right posterior–lateral margin of the cranio cervical junction, encasing the right vertebral artery and right PICA loop. Patient underwent microscopic total resection of the lesion. Pathological diagnosis was confirmed as RM with atypical features. Subsequently, the patient received postoperative intensity modulated radiotherapy (IMRT) on the tumor bed, and close follow up imaging showed no recurrence 2 years after surgery. We report the first case of a primary RM originating from the cranial cervical junction; also, it is the first case to present with extensive calcification in this morphological subtype. We also conclude that RM has now become a feature of newly diagnosed cases and not only a disease of recurrent cases as it was thought in the past. Since RMs are typically considered aggressive, total surgical resection with close follow up and postoperative adjuvant radiation should be considered. However, the adjuvant therapy of each separate case of RM should be tailored according to its particular histopathologic profile.

Foramen magnum meningiomas: To drill or not to drill the occipital condyle? A series of 12 patients

BACKGROUND

Despite the development of microsurgery and cranial base techniques, the surgical management of Foramen Magnum Meningiomas (FMM) continues to be a technical challenge to neurosurgeons. Controversy concerning the utility of systematic condyle drilling for approaching FMM has been raised. Our aim was to describe the surgical technique, analyze its safety, and the postoperative outcome in 12 consecutive FMM patients.

METHODS

From 1986 to 2011, 12 patients with FMM underwent operations in the Department of Neurosurgery at Servidores do Estado Hospital and in a private clinic. All patients were operated using a standard suboccipital craniectomy, preserving the occipital condyle, opening of the Foramen Magnum, and ipsilateral removal of the posterior arch of C1.

RESULTS

There was no operative mortality, nine patients achieved Glasgow Outcome Scale 4 or 5. Condylar resection was not deemed necessary in any case. Gross total resection was achieved in nine patients. After surgery, four patients developed lower cranial nerve weakness. There was no significant postoperative complication in the remaining patients. The average follow-up is 8.2 years.

CONCLUSION

The vast majority of FMM can be safely removed with a retrocondylar lateral suboccipital approach without condylar resection, using meticulous microsurgical techniques.

Posterior fossa meningioma "our experience" in 64 cases

Background:

Posterior fossa meningiomas are 20% of all intracranial meningiomas. These are slow-growing tumors thus become large before presentation. Microsurgical resection is the treatment of choice for the majority of these lesions, but variable locations, large size at diagnosis, frequent encroachment of neural and vascular structures, and their potentially invasive behavior are some of the features of these tumors that make their resection challenging.

Materials and Methods:

We studied 64 cases of posterior fossa meningioma operated in last 6 years, and analysed the technical difficulties encountered during excision of these tumors. Postoperative complications and outcomes of these patients were also analysed.

Results:

Gross total excision was achieved in 72% cases. Partial excision or subtotal excision was more in petroclival, jugular foramen with extra cranial extension, tentorial with intrasinus extension and ventral foramen magnum. Postoperative complication in form of new or aggravation of existing neurological deficit was found in 33% cases and CSF leak in 12.5% cases. We encountered the recurrence of total 10 cases (16%) over mean follow-up of 4 years. Most of the recurrent cases were seen in petroclival and tentorial subgroups with partial or subtotal excision.

Conclusion:

Posterior fossa meningiomas are difficult to excise due to close relation to cranial nerves and vessels. Use of microscope, CUSA, intraoperative nerve monitor help in removal and preserving surrounding important anatomical structures. Although neurological deterioration is common postoperatively, recovery does occur completely after total removal thus increasing the recurrence free period and improving the outcome.

Classification system of foramen magnum meningiomas

Background:

Foramen magnum meningiomas (FMMs) are challenging tumors. We report a classification system based on our experience of 107 tumors.

Materials and Methods:

The three main algorithm criteria included the compartment of development of the tumor, its dural insertion, and its relation to the vertebral artery.

Results:

The compartment of development was most of the time intradural (101/107, 94.4%) and less frequently extradural (3/107, 2.8%) or both intra-extradural. (3/107, 2.8%). When developed inside the intradural compartment, FMMs were subdivided into posterior (6/104, 5.8%), lateral (57/104, 54.8%), and anterior (41/104, 39.4%), if their insertion was respectively posterior to the dentate ligament, anterior to the dentate ligament without or with extension over the midline. Anterior and lateral intradural lesions grew below (77/98, 78.6%), above (16/98, 16.3%), or on both sides (5/98, 5.1%) of the VA. Only three cases of extraduralFMMs (3/107, 2.8%) were resected by an antero-lateral approach while all the other ones (104/107, 97.2%) were removed successfully by a postero-lateral approach. Lower cranial nerves were displaced superiorly in FMM growing below the VA but their position cannot be anticipated in other situations.

Conclusions:

This classification system helps for defining the best surgical approach but also for anticipating the position of the lower cranial nerves and therefore for reducing the surgical morbidity.

Gamma knife radiosurgery of meningiomas involving the foramen magnum

Background:

Foramen magnum meningiomas represent a challenging clinical entity. Although resection is performed for those with a mass effect, complete resection is not always feasible. For some patients, stereotactic radiosurgery may be used as the primary treatment modality. We evaluatedthe long-term outcome of Gamma Knife radiosurgery (GKRS) for the treatment of patientswith a foramen magnum meningioma.

Materials and Methods:

Between 1991 and 2005, 222 patients with a meningioma in the posterior fossa were treated with GKRS at the University of Virginia. Of these patients, 5 had meningiomas involving the foramen magnum. At the time of GKRS, the median age of the patients was 60 years (range, 51–78). Three patients were treated with radiosurgery following an initial resection and 2 were treated with upfront radiosurgery. The patients were assessed clinically and radiologically at routine intervals following GKRS.

Results:

The median tumor volume was 6.8 cc (range 1.9–17 cc). The GKRS tumor received a marginal dose of 12 Gy (range 10–15), and the median number of isocenters was 5 (range 3–19). The mean follow-up was 6 years (range 4–13). One lesion increased in size following GKRS requiring a second treatment, resulting in size stabilization. At the time of the last follow-up, all meningiomas had either demonstrated no growth (n = 4) or reduction in size (n = 1). No patients experienced post-radiotherapy complications.

Conclusions:

GKRS affords a high rate of tumor control and preservation of neurologic function for patients with foramen magnum meningiomas. Further study of its role in the neurosurgical management of such patients seems warranted.

Approaches to anterior and anterolateral foramen magnum lesions: A critical review

Foramen magnum (FM) lesions represent some of the most complex cases for the modern neurosurgeon because of their location near vital brainstem structures, the vertebral arteries, and lower cranial nerves. In particular, anterior or anterolaterally located FM tumors have traditionally been most difficult to resect with high morbidity and mortality resulting from approaches through the posterior midline or transorally. For many neurosurgeons, the far lateral, extreme lateral approach, and more recently, endoscopic endonasal approaches have become the preferred modern methods for the resection of anterior or anterolateral FM tumors. In this review, we examine both operative and non-operative approaches to FM tumors, including surgical anatomy, surgical technique, and indications for operative intervention in these complex cases. In addition, we compared outcomes from prior series.

Juxtacondylar approach in temporal paraganglioma surgery: when and why?

As it became clear that patients with paraganglioma (PGL) syndromes had a higher risk of multifocal tumors, we changed our surgical strategy to avoid the possibility of bilateral cranial nerve paralysis. The juxtacondylar approach offers advantages for some jugular foramen tumors, including types C and D temporal PGLs. This approach allows exposure of the jugular foramen without skeletonizing or transposing the facial nerve. It improves the surgeon's ability to distinguish between the pars vascularis and the pars nervosa at the jugular foramen, and it helps to save functioning of the lower cranial nerves. There is already considerable experience using the juxtacondylar approach for patients suffering from schwannomas and meningiomas involving the jugular foramen. Some limitations have been noted for using the juxtacondylar approach with jugular PGLs that are related to their vascular nature. In this article we demonstrate its use for the management of eight patients with locally advanced temporal PGLs and how it can be combined with an infratemporal fossa approach.

Contemporary surgical outcome for skull base meningiomas

Although surgical excision of meningioma and its dural base is the most common primary management, skull base meningiomas are quite different, and contemporary management usually consists of multimodal treatment with the aim of achieving the best possible functional outcome and quality of life (QOL) for these patients. As surgery plays an important role in the treatment of skull base meningiomas, it is crucial for neurosurgeons to appreciate the surgical outcome and QOL after meningioma surgery. Outcome is usually measured for meningiomas in terms of morbidity, mortality, time to recurrence, and QOL. The extent of resection, tumor grade, proliferative markers, and tumor location are significant factors in predicting the surgical outcome. Therefore, we address each of these factors in detail in this review. Advances in recent decades in microsurgical techniques, neuroimaging modalities, neuroanesthesia, and perioperative intensive care have substantially improved the surgical outcome; therefore, most surgical outcomes discussed in this review are cited from contemporary literature (2000 to the present) in order to depict the surgical outcome of contemporary microsurgery.

Gamma Knife surgery of meningiomas located in the posterior fossa: factors predictive of outcome and remission

Object

Although numerous studies have analyzed the role of stereotactic radiosurgery for intracranial meningiomas, few studies have assessed outcomes of posterior fossa meningiomas after stereotactic radiosurgery. In this study, the authors evaluate the outcomes of posterior fossa meningiomas treated with Gamma Knife surgery (GKS). The authors also assess factors predictive of new postoperative neurological deficits and tumor progression.

Methods

A retrospective review was performed of a prospectively compiled database documenting the outcomes of 152 patients with posterior fossa meningiomas treated at the University of Virginia from 1990 to 2006. All patients had a minimum follow-up of 24 months. There were 30 males and 122 females, with a median age of 58 years (range 12–82 years). Seventy-five patients were treated with radiosurgery initially, and 77 patients were treated with GKS after resection. Patients were assessed clinically and radiographically at routine intervals following GKS. Factors predictive of new neurological deficit following GKS were assessed via univariate and multivariate analysis, and Kaplan-Meier analysis and Cox multivariate regression analysis were used to assess factors predictive of tumor progression.

Results

Patients had meningiomas centered over the tentorium (35 patients, 23%), cerebellopontine angle (43 patients, 28%), petroclival region (28 patients, 18%), petrous region (6 patients, 4%), and clivus (40 patients, 26%). The median follow-up was 7 years (range 2–16 years). The mean preradiosurgical tumor volume was 5.7 cm3 (range 0.3–33 cm3), and mean postradiosurgical tumor volume was 4.9 cm3 (range 0.1–33 cm3). At last follow-up, 55 patients (36%) displayed no change in tumor volume, 78 (51%) displayed a decrease in volume, and 19 (13%) displayed an increase in volume. Kaplan-Meier analysis demonstrated radiographic progression-free survival at 3, 5, and 10 years to be 98%, 96%, and 78%, respectively. In Cox multivariable analysis, pre-GKS covariates associated with tumor progression included age greater than 65 years (hazard ratio [HR] 3.24, 95% CI 1.12–9.37; p = 0.03) and a low dose to the tumor margin (HR 0.76, 95% CI 0.60–0.97; p = 0.03), and post-GKS covariates included shunt-dependent hydrocephalus (HR 25.0, 95% CI 3.72–100.0; p = 0.001). At last clinical follow-up, 139 patients (91%) demonstrated no change or improvement in their neurological condition, and 13 patients showed symptom deterioration (9%). In multivariate analysis, the only factors predictive of new or worsening symptoms were clival or petrous location (OR 4.0, 95% CI 1.1–13.7; p = 0.03).

Conclusions

Gamma Knife surgery offers an acceptable rate of tumor control for posterior fossa meningiomas and accomplishes this with a low incidence of neurological deficits. In patients selected for GKS, tumor progression is associated with age greater than 65 years and decreasing dose to the tumor margin. Clival- or petrous-based locations are predictive of an increased risk of new or worsening neurological deficit following GKS.

Dorsal approaches to intradural extramedullary tumors of the craniovertebral junction

Tumors of the craniovertebral junction (CVJ) pose significant challenges to cranial and spine surgeons. Familiarity with the complex anatomy and avoidance of injury to neurologic and vascular structures are essential to success. Multiple surgical approaches to address lesions at the CVJ have been promoted, including ventral and dorsal-based trajectories. However, optimal selection of the surgical vector to manage the pathology requires a firm understanding of the limitations and advantages of each approach. The selection of the best surgical trajectory must include several factors, such as obtaining the optimal exposure of the region of interest, avoiding injury to critical neurologic or vascular structures, identification of normal anatomical landmarks, the familiarity and comfort level of the surgeon to the approach, and the need for fixation. This review article focuses on dorsal approaches to the CVJ and the advantages and limitations in managing intradural extramedullary tumors.

Retrospective analysis of peripheral nerve sheath tumors of the second cervical nerve root in 60 surgically treated patients

Object

This study is a retrospective analysis of 60 surgically treated patients with 64 peripheral nerve sheath tumors (PNSTs) at the second cervical (C-2) nerve root. The anatomical subtleties of these tumors and their implications for surgical strategy when compared with other spinal PNSTs and other tumors in the foramen magnum region are reviewed.

Methods

Sixty patients with C-2 PNSTs treated surgically in the Department of Neurosurgery at King Edward VII Memorial Hospital and Seth Gordhandas Sunderdas Medical College between 1992 and 2006 were studied. All patients underwent magnetic resonance imaging. Tumors were divided into 3 groups depending on their anatomical location identified during surgery. Those tumors located within or extending into the spinal dural tube were called Type A, those located within the dural tube of the C-2 ganglion were labeled as Type B, and tumors extending laterally into the paraspinal region were labeled as Type C. Follow-up durations ranged from 6 months to 15 years (mean 64 months).

Results

There were 38 male and 22 female patients in the study, who ranged in age from 6 to 62 years (mean 28 years). Nine patients had clinical features indicative of neurofibromatosis (NF). The mean duration of symptoms at the time of presentation was 27 months (range 4 days–5 years). Two patients had no specific symptoms related to the C-2 PNST, 6 patients had only local symptoms such as neck pain or stiffness, and 52 patients had symptoms of varying degrees of myelopathy. There were 5 solely Type A tumors, 7 Type A + B tumors, 31 Type B tumors, and 21 Type B + C tumors. All Type A, A + B, and B tumors were totally resected. Seven of 21 Type B + C tumors were partially resected, and the remainder were completely resected. All patients postoperatively reported varying improvement in their preoperative symptoms. Except for patients with NF who were disabled by other tumors, the rest of the patients resumed their normal life style. There have been no cases of symptomatic tumor recurrence.

Conclusions

The majority of PNSTs located at the C-2 level in these patients probably arose from the large C-2 ganglion and are limited within the dural confines or are interdural in location. In contrast to other spinal PNSTs, the location of C-2 PNSTs is in most cases posterior to the lateral mass of the atlas and axis and the atlantoaxial joint and is exposed to the posterior without any bone cover. Radical tumor resection is safe, resolution of clinical symptoms is rapid, and recurrence rates are extremely low. In a selected number of cases, bone work for tumor exposure and resection can be entirely avoided.

The extended endoscopic endonasal approach to the clivus and cranio-vertebral junction: anatomical study

OBJECT

Lesions located in the retroclival area and at the level of the cranio-vertebral junction are typically approached through a variety of anterior, antero-lateral and postero-lateral skull-based approach, either alone or in combination. The aim of this anatomical study was to demonstrate the possibility of an endoscopic endonasal approach to the clivus and cranio-vertebral junction.

MATERIALS AND METHODS

Five fresh cadaver heads injected with colored latex were used. A modified endonasal endoscopic approach was made through two nostrils in all cases. Endoscopic dissections were performed using rigid endoscopes, 4 mm in diameter, 18 cm in length, with 0 degrees lenses.

RESULTS

Access to the clivus was possible using a lower trajectory when compared to that necessary for the sellar region. The sphenoid sinus is entered, and its inferior wall is completely removed, permitting the union of the sphenoidal and rhinopharyngeal parts of the clivus. The entire clivus can be removed, and the cranio-vertebral junction is opened, removing the anterior arch of atlas and the odontoid process. After the opening of the dura, the anterior surface of the pons and upper spinal cord with corresponding nerves and vasculature are visible.

CONCLUSION

The endoscopic endonasal approach to the clivus and cranio-vertebral junction could be a valid alternative for surgical treatment of anterior lesions of these regions. Adequate endoscopic skill, lab training on cadavers and dedicated tools are required for clinical applications of the approach.

Technical strategies to approach aneurysms of the vertebral and posterior inferior cerebellar arteries

Object

Aneurysms of the vertebral artery (VA) and proximal posterior inferior cerebellar artery (PICA) are rare and challenging lesions, as they are located in front of the brainstem and surrounded by the lower cranial nerves. Many different approaches have been described for their treatment, and have yielded different results. With the use of different examples of lesions, the authors describe their surgical strategy in the management of VA and PICA aneurysms.

Methods

The far-lateral approach was used, and the potential of its different extensions according to the specific anatomical location and configuration of different types of aneurysms is emphasized.

Conclusions

With the present knowledge of the microsurgical anatomy in the region of the foramen magnum, the far-lateral approach can be tailored to the specific anatomical and morphological configuration of an aneurysm in this region with good surgical results.

Endoscopic endonasal surgery of the midline skull base: anatomical study and clinical considerations

Object

The midline skull base is an anatomical area that extends from the anterior limit of the cranial fossa down to the anterior border of the foramen magnum. Resection of lesions involving this area requires a variety of innovative skull base approaches. These include anterior, anterolateral, and posterolateral routes, performed either alone or in combination, and resection via these routes often requires extensive neurovascular manipulation. The goals in this study were to define the application of the endoscopic endonasal approach and to become more familiar with the views and skills associated with the technique by using cadaveric specimens.

Methods

To assess the feasibility of the endonasal route for the surgical management of lesions in the midline skull base, five fresh cadaver heads injected with colored latex were dissected using a modified endoscopic endonasal approach.

Full access to the skull base and the cisternal space around it is possible with this route. From the crista galli to the spinomedullary junction, with incision of the dura mater, a complete visualization of the carotid and vertebrobasilar arterial systems and of all 12 of the cranial nerves is obtainable.

Conclusions

The major potential advantage of the endoscopic endonasal approach to the skull base is that it provides a direct anatomical route to the lesion without traversing any major neurovascular structures, obviating brain retraction. Many tumors grow in a medial-to-lateral direction, displacing structures laterally as they expand, creating natural corridors for their resection via an anteromedial approach.

Potential disadvantages of this procedure include the relatively restricted working space and the danger of an inadequate dural repair with cerebrospinal fluid (CSF) leakage and potential for meningitis resulting. These approaches often require a large opening of the dura mater over the tuberculum sellae and posterior planum sphenoidale, or retroclival space. In addition, they typically involve large intraoperative CSF leaks, which necessitate precise and effective dural closure.

[Microsurgical resection of jugular foramen tumors with hearing preservation and without facial nerve palsy]

BACKGROUND

The juxtacondylar microsurgical approach is an adequate alternative to the classical infratemporal approach for the resection of tumors of the jugular foramen.

PATIENTS AND METHODS

Retrospectively, we report on our experience with eight patients suffering from tumors of the jugular foramen with different etiologies, who were treated successfully via the juxtacondylar approach with interdisciplinary cooperation.

RESULTS

The advantage of the juxtacondylar approach is that there is no need to expose and transpose the facial nerve. Additionally, reduction or translocation of the posterior wall of the auditory canal and removal of the ossicular chain are not necessary.

CONCLUSIONS

Tumors of the jugular foramen can be safely removed without damaging the facial nerve or auditory capacity, with a comparatively much better overview over the vascular and neural structures of the jugular foramen. This more neurosurgically orientated skull base approach is not very well known in the ENT surgical literature.