Novel classification of foramen magnum meningiomas predicted by topographic position relative to neurovascular bundle

PURPOSE

Proximity to critical neurovascular structures can create significant obstacles during surgical resection of foramen magnum meningiomas (FMMs) to the detriment of treatment outcomes. We propose a new classification that defines the tumor's relationship to neurovascular structures and assess correlation with postoperative outcomes.

METHODS

In this retrospective review, 41 consecutive patients underwent primary resection of FMMs through a far lateral approach. Groups defined based on tumor-neurovascular bundle configuration included Type 1, bundle ventral to tumor; Type 2a-c, bundle superior, inferior, or splayed, respectively; Type 3, bundle dorsal; and Type 4, nerves and/or vertebral artery encased by tumor.

RESULTS

The 41 patients (range 29-81 years old) had maximal tumor diameter averaging 30.1 mm (range 12.7-56 mm). Preoperatively, 17 (41%) patients had cranial nerve (CN) dysfunction, 12 (29%) had motor weakness and/or myelopathy, and 9 (22%) had sensory deficits. Tumor type was relevant to surgical outcomes: specifically, Type 4 demonstrated lower rates of gross total resection (65%) and worse immediate postoperative CN outcomes. Long-term findings showed Types 2, 3, and 4 demonstrated higher rates of permanent cranial neuropathy. Although patients with Type 4 tumors had overall higher ICU and hospital length of stay, there was no difference in tumor configuration and rates of postoperative complications or 30-day readmission.

CONCLUSION

The four main types of FMMs in this proposed classification reflected a gradual increase in surgical difficulty and worse outcomes. Further studies are warranted in larger cohorts to confirm its reliability in predicting postoperative outcomes and possibly directing management decisions.

Accuracy of sex estimation by morphometric evaluation of foramen magnum using computed tomography - a systematic review and meta-analysis

The objective of this study is to determine whether the morphometric evaluation of the foramen magnum using computed tomography can be used as an accurate tool in estimating the sex of an individual. An extensive search of the databases, PubMed, ProQuest, Google Scholar, and Scopus, was carried out to procure articles that fulfilled the inclusion criteria. The AQUA tool was used to assess the quality of the included studies. A random effects model was used for the meta-analysis of the eligible studies using the STATA software, version 16, 2019 at 95% CI and p ≤ 0.05. Eleven eligible articles that measured the transverse and sagittal diameters of the foramen magnum using computed tomography were included in this study. The sagittal diameter of the foramen magnum was greater than the transverse diameter, and both the diameters were greater in males than in females. Meta-analysis revealed that both transverse and sagittal diameters were more reliable for male sex estimation. Since there is a dimensional variation between the male and female foramen magnum, it can be used for initial sex identification and also as an auxiliary to other advanced methods of sex estimation.

Detailed Anatomy of Bridging Veins Around the Foramen Magnum: a Multicenter Study Using Three-dimensional Angiography

BACKGROUND AND PURPOSE

There has been limited literature regarding the bridging veins (BVs) of the medulla oblongata around the foramen magnum (FM). The present study aims to analyze the normal angioarchitecture of the BVs around the FM using slab MIP images of three-dimensional (3D) angiography.

METHODS

We collected 3D angiography data of posterior fossa veins and analyzed the BVs around the FM using slab MIP images. We analyzed the course, outlet, and number of BVs around the FM. We also examined the detection rate and mean diameter of each BV.

RESULTS

Of 57 patients, 55 patients (96%) had any BV. The median number of BVs was two (range: 0-5). The BVs originate from the perimedullary veins and run anterolaterally to join the anterior condylar vein (ACV), inferior petrosal sinus, sigmoid sinus, or jugular bulb, inferolaterally to join the suboccipital cavernous sinus (SCS), laterally or posterolaterally to join the marginal sinus (MS), and posteriorly to join the MS or occipital sinus. We classified BVs into five subtypes according to the draining location: ACV, jugular foramen (JF), MS, SCS, and cerebellomedullary cistern (CMC). ACV, JF, MS, SCS, and CMC BVs were detected in 11 (19%), 18 (32%), 32 (56%), 20 (35%), and 16 (28%) patients, respectively. The mean diameter of the BVs other than CMC was 0.6 mm, and that of CMC BV was 0.8 mm.

CONCLUSION

Using venous data from 3D angiography, we detected FM BVs in most cases, and the BVs were connected in various directions.

Surgical treatment of marginal sinus dural arteriovenous fistula: a narrative review

BACKGROUND

Dural arteriovenous fistulas of the marginal sinus (DAVFms) are uncommon and complex, with varied symptoms. Their complexity is heightened by the region's dense anastomotic network, posing risks for endovascular treatment. Surgical intervention can be effective, but this depends on thorough pre-operative understanding and optimal intra-operative visualization of the fistula.

OBJECTIVE

To review the relevant anatomy, presentation patterns of DAVFms, and provide insights for surgical treatment.

METHODS

Recent literature on DAVFms was reviewed, and three surgical cases are discussed to highlight treatment principles.

RESULTS

The symptoms of a DAVFms vary depending on its venous drainage pattern. Drainage may be either ascending towards the cranial compartment or descending towards the spinal canal. Patients suffering from DAVFms may experience hemorrhage, particularly when venous drainage is directed upwards. Congestive symptoms of the spinal cord or brainstem can occur in cases of downward venous drainage. Compared to the endovascular approach, open surgery has a higher success rate in obliterating the fistula and yields better outcomes in cases of perimedullary venous drainage. Achieving surgical success necessitates thorough preoperative evaluation and adequate surgical exposure. Brainstem hyperintensity observed on T2-weighted MRI scans is linked to a poorer prognosis for recovery.

CONCLUSION

Treating complex DAVFms often requires surgery, as endovascular methods may not be feasible. Successful surgery hinges on a precise understanding of the fistula's venous architecture and its spatial relationships, assessed using digital substraction angiography (DSA), angio-MRI, and angio-CT. Optimal intraoperative exposure is crucial for effective surgery.

Bridging veins at the craniocervical junction: from anatomy to clinical significance in dural arteriovenous shunts

PURPOSE

Bridging veins (BVs) serve as a route of pial venous reflux, and its anatomy is essential to understand the pathophysiology of dural arteriovenous shunts (dAVSs) around the craniocervical junction (CCJ) (from the jugular foramen level to the atlantal level). However, the anatomical variations of the BVs and their proximal connections remained poorly elucidated. This study aimed to radiologically investigate the anatomy of the bridging veins around CCJ and discuss the clinical significance of these BVs in the dAVS.

METHODS

We investigated normal venous anatomy of the BVs from the jugular foramen level to the atlantal level using preoperative computed tomography digital subtraction venography in patients undergoing elective neurosurgery. BVs affected by the dAVSs in the same region were also evaluated. The three types of dAVS, craniocervical junction, anterior condylar, and proximal sigmoid sinus, were investigated.

RESULTS

We identified six BV groups: superolateral, anterolateral, lateral, posterior, inferolateral, and inferoposterior. The superolateral and inferolateral groups, connected with the proximal sigmoid sinus and suboccipital cavernous sinus, respectively, were the largest groups. Each group has a specific downstream venous connection. The association with dVASs was observed only in the inferolateral group, which was typically the sole venous drainage in most dAVSs at the CCJ.

CONCLUSION

We reported detailed anatomy of BVs from the jugular level to the atlantal level, which enhanced our understanding of the pathophysiology of dAVSs in the corresponding region.

Re-imagining early cloverleaf skull deformity management from front to back approach-30 years on

The cloverleaf skull deformity remains among the most complicated craniofacial conditions to successfully manage. Many cases achieve largely unsatisfactory outcomes due to the requirement for frequent reoperation on the cranial vault and failure to deal with all the elements of the craniofaciostenosis in a timely fashion. Early cranial vault surgery without addressing the cranial base deformity and its attendant cerebrospinal fluid flow changes is invariably challenging and disappointing. A recent focus on the expansion of the posterior cranial vault as a primary procedure with the greater volume change allows a delay in fronto-orbital advancement and reduced need for repeat surgery. We herein describe three cases of complex multisuture craniosynostosis with cloverleaf skull deformity who underwent neonatal posterior cranial vault decompression along with foramen magnum decompression. Our report examines the safety and rationale for this pre-emptive surgical approach to simultaneously deal with the cranial vault and craniocervical junction abnormalities and thus change the early trajectory of these complex cases.

Unravelling the pathogenesis of foramen magnum stenosis in patients with severe achondroplasia: a CT-based comparison with age-matched controls and FGFR3 craniosynostosis syndromes

OBJECTIVE

Foramen magnum(FM) stenosis can be responsible for acute and chronic damage to the cervicomedullary junction in children with achondroplasia. The bony anatomy and patterns of suture fusion of the FM in this context are incompletely understood, yet becoming increasingly important in the light of novel medical therapies for achondroplasia. The objective of this study was to describe and quantify bony anatomy and fusion patterns of FM stenosis in patients with achondroplasia using CT scans, comparing them to age-matched controls and other FGFR3 craniosynostosis patients.

METHODS

Patients with achondroplasia and severe FM stenosis, classified as achondroplasia foramen magnum score(AFMS) grades 3 and 4, were identified from a departmental operative database. All had pre-operative CT scans of the craniocervical junction. Measurements obtained comprised sagittal diameter (SD), transverse diameter (TD), foramen magnum area, and opisthion thickness. Anterior and posterior interoccipital synchondroses (AIOS and PIOS) were graded by the extent of fusion. These measurements were then compared with CT scans from 3 age-matched groups: the normal control group, children with Muenke syndrome, and children with Crouzon syndrome with acanthosis nigricans (CSAN).

RESULTS

CT scans were reviewed in 23 cases of patients with achondroplasia, 23 normal controls, 20 Muenke, and 15 CSAN. Children with achondroplasia had significantly smaller sagittal diameter (mean 16.2 ± 2.4 mm) compared to other groups (control 31.7 ± 2.4 mm, p < 0.0001; Muenke 31.7 ± 3.5 mm, p < 0.0001; and CSAN 23.1 ± 3.4 mm, p < 0.0001) and transverse diameters (mean 14.3 ± 1.8 mm) compared with other groups (control 26.5 ± 3.2 mm, p < 0.0001; Muenke 24.1 ± 2.6 mm, p < 0.0001; CSAN 19.1 ± 2.6 mm, p < 0.0001). This translated into a surface area which was 3.4 times smaller in the achondroplasia group compared with the control group. The median grade of the AIOS fusion achondroplasia group was 3.0 (IQR 3.0-5.0), which was significantly higher compared with the control group (1.0, IQR 1.0-1.0, p < 0.0001), Muenke group (1.0, IQR 1.0-1.0, p < 0.0001), and CSAN (2.0, IQR 1.0-2.0, p < 0.0002). Median PIOS fusion grade was also highest in the achondroplasia group (5.0, IQR 4.0-5.0) compared with control (1.0, IQR 1.0-1.0, p < 0.0001), Muenke (2.5, IQR 1.3-3.0, p < 0.0001), and CSAN (4.0, IQR 4.0-4.0, p = 0.2). Distinct bony opisthion spurs projecting into the foramen magnum were seen in achondroplasia patients but not others, resulting in characteristic crescent and cloverleaf shapes.

CONCLUSION

Patients with AFMS stages 3 and 4 have significantly reduced FM diameters, with surface area 3.4 times smaller than age-matched controls. This is associated with premature fusion of the AIOS and PIOS in comparison with controls and other FGFR3-related conditions. The presence of thickened opisthion bony spurs contributes to stenosis in achondroplasia. Understanding and quantifying bony changes at the FM of patients with achondroplasia will be important in the future quantitative evaluation of emerging medical therapies.

New minimally-invasive approach in adult for Chiari I malformation

BACKGROUND

Chiari I malformation is defined by tonsillar herniation through the foramen magnum. There is no consensus on the treatment of Chiari malformation. A simple follow-up is recommended for asymptomatic cases. The classic approach is the midline sub-occipital craniotomy.

METHODS

For four years, we operated on six patients with Chiari malformation I using our endoscopic minimally invasive sub-occipital approach. We compared the results with six other patients operated by the classical sub-occipital approach.

RESULTS

Patients operated by endoscopic approach had shorter hospital stays, and wounds healed faster and smoother. Mid-term results were similar in the two groups.

CONCLUSION

This paper proposes a new endoscopic Minimally invasive paramedian sub-occipital approach for Chiari malformation I. Although the number of cases is limited, the results look promising. We need to gather more cases to have significant numbers to perform a global comparison between the two approaches and assess the advantages and disadvantages of each technique.

Approaching Intradural Lesions of the Anterior Foramen Magnum and Craniocervical Junction: Anatomical Comparison of the Open Posterolateral and Anterior Extended Endonasal Endoscopic Approaches

BACKGROUND

Lesions of the foramen magnum (FM) and craniocervical junction area are traditionally managed surgically through anterior, anterolateral, and posterolateral skull-base approaches. This anatomical study aimed to compare the usefulness of a modified extended endoscopic approach, the so-called far-medial endonasal approach (FMEA), versus the traditional posterolateral far-lateral approach (FLA).

METHODS

Ten fixed silicon-injected heads specimens were used in the Skull Base ENT-Neurosurgery Laboratory of the University Hospital of Strasbourg, France. A total of 20 FLAs and 10 FMEAs were realized. A high-resolution computed tomography scan was performed for quantitative analysis of the different approaches. The analysis aimed to estimate the extent of surgical exposure and freedom of movement (maneuverability) through the operating channel using a polygonal surface model to obtain a morphometric estimation of the area of interest (surface and volume) on postdissection computed tomography scans using Slicer 3D software.

RESULTS

FMEA allows for a more direct route to the anterior FM, with wider brainstem exposure compared with the FLA and an excellent visualization of all anterior midline structures. The limitations of the FMEA include the deep and narrow surgical corridor and difficulty in reaching lesions located laterally over the jugular foramen and hypoglossal canal.

CONCLUSIONS

The FMEA and FLA are both effective surgical routes to reach FM and craniocervical junction lesions. Modern skull base surgeons should have a good command of both because they appear complementary. This anatomical study provides the tools for comprehensive preoperative evaluations and selection of the most appropriate surgical approach.

Clinical and anatomical importance of foramen magnum and craniocervical junction structures in the perspective of surgical approaches

This study was conducted to investigate the clinical and anatomical importance of the relevant region from the perspective of surgical approaches by determining the morphometric analysis of the craniocervical junction and foramen magnum (FM) region and determining their distances from important anatomical points. This research was carried out with 59 skulls found at the Anatomy Laboratories of Erciyes and Ankara Medipol University. Metric measurements of FM and condyle, FM shape, condyle-fossa relationship, and pharyngeal tubercle (PT) were made in mm-based dry bone samples of unknown age and sex. The distance between the anterior notches and the FM was 87.01±4.35, the distance between the anterior notches and the PT was 77.70±4.24, the distance between the PT-sphenooccipital junction was 13.23±2.42, and the FM index was 81.86±7.47. The anteroposterior and transverse lengths of FM were determined as 33.80±2.99 and 27.72±2.30, respectively. The morphometric and morphological data available regarding the craniocervical junction showed significant differences between populations. Comprehensive knowledge of this topic will provide a better approach to treat Arnold Chiari Malformation, FM meningiomas, and other posterior cranial fossa lesions. Therefore, we believe that FM and craniocervical junction morphology will be a guide not only for anatomists, but also for radiologists, neurosurgeons, ENT surgeons, and orthopedists.

Effect of Body Mass Index on Chiari Malformation 1 Tonsil Ectopia Length in Adults

OBJECTIVE

Diagnosis of Chiari I malformation (CM-1) is based on measurements of the inferior extension of the cerebellar tonsils into the foramen magnum on cranial or cervical spine magnetic resonance imaging. Imaging may be obtained before the patient is referred to the neurosurgical specialist. The length of time raises questions about the possibility that body mass index (BMI) fluctuations could affect the measurement of ectopia length. However, previous literature on BMI and CM-1 has reported conflicting findings on BMI.

METHODS

We conducted a retrospective chart review of 161 patients who were referred to a single neurosurgeon for CM-1 consultation. Patients with multiple recorded BMI values (n = 71) were compared to see if BMI changes correlated with changes in ectopia length. In addition, we compared and tested 154 recorded ectopia lengths from the patients (1 per patient) and patient BMI values with Pearson correlation and Welch t tests to determine if BMI changes either influenced or were associated with ectopia changes.

RESULTS

For the 71 patients with multiple BMI values, change in ectopia length ranged from -4.6-9.8 mm but was not statistically significant (r = 0.019; P = 0.88). For the 154 measured ectopia lengths, changes in BMI did not correlate with ectopia length (P > 0.05). Likewise, differences in ectopia length between patients in normal, overweight, and obese categories were not statistically significant (|tstat| < |tcrit|, P > 0.05).

CONCLUSIONS

In individual patients, we found that BMI and changes in BMI were not accompanied by changes in tonsil ectopia length.

Retrospective evaluation of the morpometric and morphological anatomy of the occipital condyle, hypoglossal canal and foramen magnum in Turkish populaton with CBCT

PURPOSE

The aim of this study is to morphometrically and morphologically examine the occipital condyle, which is an important anatomical region in terms of surgery and forensic medicine, and its surrounding structures, to evaluate the change in mean values according to gender and age, and to evaluate the correlation of the measurements obtained.

METHODS

180 (90 men, 90 women) CBCT images selected from the archive of Ankara University Faculty of Dentistry. Occipital Condyle length and width, Hypoglossal Canal-Basion distance, Hypoglossal Canal-Opistion distance, Hypoglossal Canal-Occipital Condyle anterior and posterior border distance, Occipital Condyle thickness, Hypoglossal Canal length, the widest diameter of Hypoglossal Canal, the narrowest diameter of the Hypoglossal Canal, the length of the Jugular Tubercle, the width of the Jugular Tubercle, the anterior intercondylar distance, the posterior intercondylar distance, and the Foramen Magnum index were measured. At the same time, the presence of septum or spicule in the hypoglossal canal and protrusion of the occipital condyle were evaluated. The relationship of age, gender, anterior and posterior intercondylar distance, and foramen magnum index measurements with all measurements were examined.

RESULTS

In our study, all measurements were repeated 1 month after the first measurements to evaluate the intra-observer agreement, and the agreement between the obtained measurements and the first measurements was evaluated by calculating the intraclass correlation coefficient and 95% confidence intervals. Men's measurements were found to be significantly higher than women's measurements. When the coefficients of concordance in all measurements were examined, it was observed that there was a perfect concordance.

CONCLUSION

When the results of the study are evaluated, it is seen that the values ​​obtained are generally close to the studies related to CT. Considering this, an idea can be gained as to whether CBCT, which has a lower dose and less cost, can be used as an alternative to CT in studies to be conducted with more comprehensive and different methods in skull base surgical planning.

Compromised bilaterality in the small African pangolin (Phataginus tricuspis) - An expression of or compensation for developmental errors; asymmetry, elliptical Fourier analyses and modularity

We present a postnatal evaluation of skull developmental signaling in small African pangolin emphasizing structural, and cognitive trend in ontogeny for assessment of developmental instability, proper identification and classification, forty digitally processed skulls and foramen magnum from different geo-locations were assessed for asymmetry, foramen magnum shape and modularity using geometric and Elliptical Fourier analyses. Multivariate analysis of regression demonstrated low (p < 0.5) but directional fluctuating asymmetry (F₁₅₃₉ = 3.4045, F₈₈₂ = 3.2665, dorsal and ventral views). Allometric trajectories followed rostrocaudal, caudolateral directions; Intercepts for shape/size predictions were parallel. Mahalanobis distances between centroids (2.42) were significant (p < 0.01). The variance-covariance matrix in ontogeny lies between 0.0017 and 0.56. Foramen magnum outline descriptors by incremental harmonics revealed first 4 effective PCs defined 96.98% of shape properties and 3.02% constituted finerdetails. 74.1% accuracy decline after size factor elimination. Modulation PCA of covariance matrix and asymmetry component was 88.38% and 7.48% (PC1 and 2), respectively, the variance % predicted 10.08%. The studied samples confirmed 'handedness' and fluctuating asymmetries. Foramen magnum shape assumed priority over size in ontogeny with profound asymmetry (from the 5th harmonic), suggestive of compensations to lateralization in neural integration modules.

A new supportive approach in the diagnosis of Chiari malformation type 1 in pediatric patients

PURPOSE

Chiari malformation type 1 (CM-1) is a posterior fossa anomaly characterized by herniation of the cerebellar tonsils from the foramen magnum (FM). This study compares FM, medulla spinalis (MS), and herniated cerebellar tonsils ratios by making area measurements from axial plane MRI in CM-1 patients and the control group.

METHODS

Our study evaluated 30 pediatric patients with CM-1 and 30 people in the control group. The lengths of the McRae line, twining line, and clivus line were measured on the posterior cranial fossa evaluation. The areas of FM (A_FM), MS (A_MS), and herniated cerebellar tonsils (A_TONSILS) were measured by axial images.

RESULTS

As a result of area measurements obtained from axial cross-sectional MRI, a statistically significant difference was found between CM-1 patients and the control group. According to the results of the ROC analysis, if an individual's A_MS/A_FM value is above 17.9% or the A_TONSILS/A_FM value is above 18.4%, it can be interpreted as a CM-1 patient.

CONCLUSION

It will be easier to diagnose the patient with the new approach we obtained from axial MR images in addition to sagittal MR images. This method can be a guide in some cases when the surgeons are undecided.

Foramen magnum meningioma approached by the midline subtonsilar approach - Revisiting Cushing's classification of craniospinal meningiomas

Background

The management of foramen magnum meningiomas (FMMs) has been a challenge for skull base neurosurgeons. Since the initial description of a FMM in 1872, various surgical approaches have been described. Posterior and posterolateral FMMs are safely removed through a standard midline suboccipital approach. Nevertheless, we still face controversy regarding the management of anterior or anterolateral lesions.

Case Description

A 47-year-old patient presented with progressive headaches, unsteadiness, and tremor. Magnetic resonance imaging showed an FMM that caused significant displacement of the brainstem.

Conclusion

This operative video highlights a safe and effective surgical technique for the resection of an anterior foramen magnum meningioma.

Far Lateral Approach: "Trans-tumor Approach" on Huge Dumbbell-Shape Neurofibroma of Anterior Foramen Magnum Without Craniectomy-Anatomical Consideration and New Trend

The foramen magnum approach is always challenging because of the relationships between vital neurovascular structures in this area. Several approaches have been described, among them, the far lateral approach remains a cornerstone for the resection of anterior or anterolateral processes of the foramen magnum. This approach displays two main steps: the first is cervical, whereas the second is cranial.We report the case of a 63 year-old woman admitted for a progressive quadriplegia with swallowing disorders revealing a process of the anterior and anterolateral part of the foramen magnum. A cervical step of a far lateral approach without opening the foramen magnum achieved a near total resection of the process via a trans-tumor corridor and confirmed a dumbbell shape neurofibroma. The postoperative period showed a resolution of swallowing disorders and a progressive improvement of muscular strength. At 8 months follow-up, she was asymptomatic and able to walk with a normal balance. The surgical technique and anatomical correlation of this trans-tumor approach are discussed.

Far-Lateral Approach for Foramen Magnum Meningioma: An Anatomical Study with Special Reference to Bulbopontine Junction

Intracranial meningiomas are sometimes located anteriorly to the foramen magnum and can cause disabling long tract symptoms. The far-lateral approach has been developed to provide an extensive view over the bulbopontine junction and the surrounding lower cranial nerves and upper spinal nerves with a good control on the vertebral artery, allowing the safe resection of such tumors. It is the report of a case with anatomical study before and after the removal of the meningioma. The use of the far-lateral approach allowed us to (1) control the vertebral artery in its V3 (Atlantic extradural) and V4 (intradural) portion (2) have an optimal visibility on the lower cranial nerves, the upper spinal nerves, and the bulbopontine junction, and (3) perform a Simpson 2 resection of the tumor that was inserted between the lower clivus and the upper odontoid process. Beyond its interest for the safe resection of tumors located anteriorly to the foramen magnum, the far-lateral approach is of particular anatomical interest. It allowed us to review the anatomy of the craniocervical junction.

Sex estimation using foramen magnum measurements, discriminant analyses and artificial neural networks on an eastern Turkish population sample

BACKGROUND

Although many studies have been conducted using the foramen magnum for sex estimation, recent findings have indicated that the discriminant and regression models obtained from the foramen magnum may not be reliable. Artificial Neural Networks, was used as a classification technique in sex estimation studies on some other bones, did not used in sex estimation studies on the foramen magnum until now. The aim of this study was sex estimation on an Eastern Turkish population sample using foramen magnum measurements, discriminant analyses and Artificial Neural Networks.

METHODOLOGY

The study was performed on the CT images of a total of 720 cases, comprising 360 males and 360 females. For sex estimation, discriminant analysis and Artificial Neural Networks were used.

RESULTS

The accuracy rate was 86.7% with discriminant analysis and when sex estimation accuracy was determined according to cases with posterior probabilities above 95%, the accuracy ranged from 0% to 33.3%. With the use of the discriminant formulas of 2 other studies, obtained from different Turkish samples, sex could be determined at a rate of 84.6%. Some formulas were found to be unsuccessful in sex estimation. Sex estimation accuracy of 88.2% was achieved with Artificial Neural Networks.

CONCLUSION

In this study, it was found that sex could be determined to some extent with discriminant formulas from other samples from the same population, although some formulas were unsuccessful. With the use of image processing techniques and machine learning algorithms, better results can be obtained in sex estimation.

Chiari Type 1 malformation: CSF flow dynamics and morphology in the posterior fossa and craniocervical junction and correlation of these findings with syrinx formation

BACKGROUND

Chiari type 1 malformation (CMI) is a disorder in which cerebellar tonsils descend below the foramen magnum. Although syringomyelia associated with CMI thought to be caused by hypoplastic posterior fossa and stenosis at the craniocervical junction; it has characteristic neurological and radiological features and the exact mechanism of syringomyelia remains unknown.

PURPOSE

The purposes of this study were to gain insight into morphological changes in posterior fossa and to find whether there is a difference in aqueductal stroke volume (ASV) between CMI with syrinx and without syrinx which may be an underlying mechanism of syrinx development.

MATERIALS AND METHODS

We consecutively evaluated 85 patients with Chiari malformation between January 2017 and December 2019 who had undergone phase-contrast MRI examination for CSF flow and between 18-60-years-old. We divided patients into two groups as subjects with syrinx (n=19) and without syrinx (n=66). After evaluating morphological changes, peak and average velocity (cm/s), forward and reverse flow volume (μl), net forward flow volume (μl), ASV (aqueductal stroke volume) (μl), aqueductus Sylvi (AS) area (mm²), and prepontine cistern diameter to AS diameter ratio (PPC/AS) were calculated. Distribution of variables from two groups was evaluated by using Shapiro-Wilk normality test. Independent t test was used for groups comparison.

RESULTS

The forward and reverse volumes were statistically significantly higher in patients with syrinx (P=0.021, P=0.005 respectively). ASV was significantly increased in patients with syringomyelia (P=0.014). The PPC/AS was significantly lower in patients with syrinx compared to those without (P <0.001). AS area was significantly larger in those with syrinx. (P=0.022). The diameter of foramen magnum was significantly lower in patients with syrinx than those without (P <0.0001). The diameter of the herniated tonsilla at the foramen magnum level was found to be significantly lower in those with syrinx (P=0.011).

CONCLUSION

Foramen magnum diameter, ASV, diameter of herniated tonsil, and PPC/AS ratio are important factors in syrinx development.

Basilar invagination: a tilt of the foramen magnum

OBJECTIVES

Congenital basilar invagination (BI) is a craniocervical deformity marked by odontoid prolapse into the skull base. The foramen magnum angle (FMA), which is formed by Chamberlain's line and McRae's line has not been fully studied. The study aimed to investigate the FMA and its relationship with other craniocervical parameters.

METHODS

Participants were divided into controls, type A BI and type B BI. Parameters included Chamberlain line violation (CLV), atlantodental interval, clivus height, clivus anteroposterior dimension, FMA, basal angle, clivo-axial angle, head and neck flexion angle, Boogard's angle, and subaxial cervical spine lordosis angle. Comparision of these parameters among the three groups and correlation analysis between FMA and other parameters was performed. The significance level was set at P<0.05.

RESULTS

A total of 111 controls, 111 type A BI patients, and 62 type B BI patients were enrolled. The FMAs in the control, type A BI, and type B BI groups were 6.21 (3.67,8.71), 22.16±6.61, and 22.39 (17.27, 31.08) °, respectively. Correlation analysis revealed correlations between the FMA and other variables. In the two BI subgroups, FMA was significantly correlated with CLV, clivus height, clivus anteroposterior dimension, basal angle, clivo-axial angle, and Boogard's angle.

CONCLUSION

The FMA in patients with BI was approximately 22° and approximately 6° in controls, indicating that the FM in BI had a greater tilt. As a pathological condition, FMA can reflect the degree of BI. Clivus hypogenesis is a reason for excessive tilt of the FM.

The Forgotten Intermediate Condylar Canal: Anatomic Study with Application to Skull Base Surgery

BACKGROUND

The intermediate condylar canal, which lies lateral to the occipital condyles and medial to the jugular foramen, is rarely mentioned in textbooks, even those devoted to the skull base. Therefore the present anatomic study was performed to better elucidate these structures.

METHODS

We studied 100 adult skulls (200 sides) to better understand the prevalence and anatomy of the intermediate condylar canal.

RESULTS

An intermediate canal was found on 6 of 200 sides (3%). On average, these canals traveled 7.1 mm lateral to the occipital condyle and had a mean of 2.2 mm posteromedial to the jugular foramen. Anteriorly, these canals opened into the external surface of the hypoglossal canal and, when present, were just medial to a paracondylar process for which there was a strong positive correlation. The length of the canals ranged from 5 to 7.8 mm. In all, there were 3 partial canals and 3 complete canals. One left canal communicated anteriorly at the confluence of the inferior opening of a septated (bifurcated) hypoglossal canal and an unnamed foramen medial to the jugular foramen. These canals were distinct from posterior condylar canals when the latter was present.

CONCLUSIONS

Knowledge of the anatomic variants at the base of the skull may help minimize complications during surgical procedures that employ a paracondylar or transcondylar approach or approaches to the jugular foramen.

Coincidental Nasopharyngeal Carcinoma and Ventral Foramen Magnum Meningioma: Case Report and Review of the Literature

Multiple primary tumors at adjacent site are rare. We report a rare case of coincidentally found nasopharyngeal cancer and ventral foramen magnum meningioma. The 68-year-old male patient presented with a year history of ataxia. Radiological examination revealed lesions in the nasopharyngeal space and ventral foramen magnum. A needle aspiration biopsy for nasopharyngeal space and surgical removal for foramen magnum lesion were performed. The pathological diagnoses were nasopharyngeal cancer and meningioma, respectively. The concomitant occurrence of these two tumors is very rare and there is no known association between these two tumors. We report a case of ventral foramen magnum meningioma simultaneously present with nasopharyngeal carcinoma.

The (extended) achondroplasia foramen magnum score has good observer reliability

BACKGROUND

Achondroplasia is the most common skeletal dysplasia. A significant complication is foramen magnum stenosis. When severe, compression of the spinal cord may result in sleep apnea, sudden respiratory arrest and death. To avoid complications, surgical decompression of the craniocervical junction is offered in at-risk cases. However, practice varies among centres. To standardize magnetic resonance (MR) reporting, the achondroplasia foramen magnum score was recently developed. The reliability of the score has not been assessed.

OBJECTIVE

To assess the interobserver reliability of the achondroplasia foramen magnum score.

MATERIALS AND METHODS

Base of skull imaging of children with achondroplasia under the care of Sheffield Children's Hospital was retrospectively and independently reviewed by four observers using the achondroplasia foramen magnum score. Two-way random-effects intraclass coefficient (ICC) was used to assess inter- and intra-observer reliability.

RESULTS

Forty-nine eligible cases and five controls were included. Of these, 10 were scored normal, 17 had a median score of 1 (mild narrowing), 11 had a median score of 2 (effacement of cerebral spinal fluid), 10 had a score of 3 (compression of cord) and 6 had a median score of 4 (cord myelopathic change). Interobserver ICC was 0.72 (95% confidence interval = 0.62-0.81). Intra-observer ICC ranged from 0.60 to 0.86. Reasons for reader disagreement included flow void artefact, subtle T2 cord signal and myelopathic T2 cord change disproportionate to canal narrowing.

CONCLUSION

The achondroplasia foramen magnum score has good interobserver reliability. Imaging features leading to interobserver disagreement have been identified. Further research is required to prospectively validate the score against clinical outcomes.

The foramen magnum in scaphocephaly

PURPOSE

The foramen magnum (FM) presents various alterations in craniosynostoses, such as brachycephaly or Crouzon syndrome. However, to date, no study has been devoted to its morphology and morphometry in scaphocephaly, which is the most common of cranial deformities resulting from premature fusion of cranial sutures.

METHODS

We assessed the morphology and morphometry of FM using preoperative thin-cut CT scans of 107 children with non-syndromic sagittal craniosynostosis aged 1-12 months (mean age 5.38 months). A series of sagittal and transverse dimensions were taken and the FM area was calculated in each case. Obtained data were compared to the age-matched control group of 101 normocephalic children.

RESULTS

Dolichotrematous type of FM was dominant in the scaphocephaly group and observed in 63/107 cases (58.9%). The mean FM area in the scaphocephaly group was 519.64 mm² and was significantly smaller compared to the control group (p = 0.0011). The transverse diameter and anterior sagittal diameter were also significantly smaller (p = 0.0112 and p = 0.0003, respectively).

CONCLUSION

The area of FM in scaphocephaly is smaller compared to normal individuals. This is associated with a significant reduction of the width of FM in children with sagittal craniosynostosis. FM in scaphocephaly is larger than in other reported series of children with brachycephaly or Crouzon syndrome.

Endoscope-Assisted Resection of Extra-Axial Premedullary Neurenteric Cyst via Far Lateral-Supracondylar Approach: 2-Dimensional Operative Video

Neurenteric cysts are rare congenital lesions that may compress the ventral brainstem.1-9 In this operative video, we illustrate the surgical treatment of an intradural extra-axial neurenteric cyst extending from the lower pons to the craniocervical junction. The patient, an asymptomatic 52-yr-old female, underwent surveillance imaging of the premedullary lesion for 14 yr without progression. However, after developing progressive strain-induced headaches, imaging revealed a significant enlargement of the lesion with brainstem compression and partial obstruction of the foramen magnum. Therefore, surgical resection was pursued. The patient consented to the procedure. The patient underwent a lateral suboccipital craniotomy and C1 laminectomy through a far lateral approach. The lesion was immediately visualized upon opening the dura. After identifying the cranial nerves, we resected the tumor while taking care to preserve the neurovascular elements of the cerebellopontine angle and foramen magnum. During the resection, we unexpectedly encountered a firm nodule that was adherent to the right posterior inferior cerebellar artery. This was meticulously dissected and removed en bloc using intraoperative indocyanine green (ICG) angiography. The cavity was inspected with 0-degree and 30-degree endoscopes to ensure complete resection of the lesion. Gross total resection was confirmed on postoperative magnetic resonance imaging. The patient was neurologically intact with no cranial nerve abnormalities and discharged home on postoperative day 3. This case demonstrates that the far lateral-supracondylar approach affords safe access to the ventral pontomedullary and craniocervical junctions and that intraoperative adjuncts, including ICG angiography and endoscopic visualization, can facilitate complete lesion resection with excellent clinical outcomes.

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.

craniocervical junction lesions

PURPOSE

Dural arteriovenous fistulas (AVFs) draining to medullary bridging vein (MBV) are located at foramen magnum (FM) and craniocervical junction (CCJ). Such fistulas are rare but pose a challenge to endovascular management. This study was undertaken to assess clinical manifestations, angiographic features, and outcomes of endovascular treatment in patients with MBV dural AVFs.

METHODS

A number of our patients (N = 22) were diagnosed with MBV dural AVF and treated by endovascular means. There were 9 FM lesions and 13 CCJ lesions. We reviewed clinical records and imaging studies to define clinical characteristics, vascular anatomic details, and treatment outcomes, comparing FM- and CCJ-level subsets.

RESULTS

Subjects ranged from 37 to 74 years of age (mean, 57.7 years) with male predominance (2.7:1). They presented with intracranial hemorrhage (11/22, 50%), myelopathy (8/22, 36%), or nonspecific symptoms (3/22, 14%). In 17 patients (77.3%), the shunts showed complete or near-complete occlusion following endovascular treatment (FM, 100%; CCJ, 61.5%). However, seven patients experienced ischemic events (FM, 11.1%; CCJ, 46.2%) and one patient sustained a hemorrhagic complication. No hemorrhages recurred during follow-up monitoring, and myelopathic symptoms abated.

CONCLUSION

MBV dural AVFs are highly aggressive lesions for which proper diagnosis and treatment are of utmost importance. Although transarterial embolization proved highly successful in FM lesions, shunt occlusion was less frequent in the CCJ subset, with greater risk of ischemic complications.

Foramen Magnum Dural Arteriovenous Fistula Presenting With Thoracic Myelopathy: Technical Case Report With 2-Dimensional Operative Video

BACKGROUND AND IMPORTANCE

Dural arteriovenous fistulas (dAVFs) are vascular abnormalities of the central nervous system that can cause a wide array of neurological dysfunction depending on their location, flow, and propensity to rupture. Symptomatic dAVFs at the cranio-cervical junction usually result in hemorrhage or cervical myelopathy. Distantly located dAVFs of the foramen magnum are a rare cause of thoracic intrinsic myelopathy.

CLINICAL PRESENTATION

An 83-yr-old man presented with progressive lower extremity weakness, numbness, and difficulty walking along with episodes of bowel incontinence. Magnetic resonance imaging of the cervical spine demonstrated multilevel cervical disc disease with stenosis and longitudinal cervical cord signal change extending into the upper thoracic spinal cord. Cerebral and spinal angiography revealed a dAVF in the lateral foramen magnum region. Given the location, feeding vasculature, and morphology of the fistula, endovascular embolization was not attempted. Microsurgical resection with confirmative indocyanine green fluorescent imaging was performed with adequate obliteration of the fistula. The patient's neurological baseline was preserved postoperatively with improvement of lower extremity numbness.

CONCLUSION

We present a brief overview of this neuropathologic entity and demonstrate microsurgical resection of a foramen magnum dAVF through operative video. Craniocervical dAVFs should remain on the differential diagnosis of patients presenting with progressive thoracolumbar myelopathy.

Increase of the clivus-canal angle in patients with basilar invagination, without atlantoaxial displacement, treated with a simple maneuver of indirect decompression of the odontoid with the head clamp, during posterior occipitocervical arthrodesis

Background:

Basilar invagination (BI) can be defined as the insinuation of the content of the craniovertebral junction through the foramen magnum toward the posterior fossa. BI is a prevalent condition in Northeast Brazil. The present study describes the changes in the clivus-canal angle (CCA) in the postoperative period in patients with symptomatic BI operated by a posterior approach, using a simple technique of indirect reduction of the odontoid associated with occipitocervical fixation.

Methods:

Patients underwent radiological evaluations by magnetic resonance imaging in the pre and postoperative periods, where the height of the odontoid tip was measured in relation to the Chamberlain line and the ACC. All patients underwent posterior occipitocervical fixation with specific maneuvers of distraction and extension of the cephalic segment with the aid of a head clamp with three fixation points for anterior reduction of the odontoid.

Results:

Among the 8 patients evaluated in the series, all had increased ACC in the postoperative period, with a mean of 14.81 ± 1.54°, and statistically significant difference between the pre and postoperative periods (P < 0.05).

Conclusion:

The indirect surgical reduction of the odontoid process by a posterior approach through the manipulation (distraction-extension) of a “Mayfield” type of head clamp followed by occipitocervical fixation proved to be effective in improving the ACC, being easily reproducible.

Neuroendoscopic treatment of giant cystic craniopharyngioma in the foramen magnum: report of two cases

Pediatric craniopharyngioma is typically characterized by cystic changes and calcifications. It can grow from the suprasellar area to the posterior fossa (4%). This work reports that it is very rare for craniopharyngioma to grow from the suprasellar area to or beyond the level of the foramen magnum. Twelve patients with this disease have undergone one or several microsurgeries, and the microsurgical approaches are different. Among them, two cases died, and most of the remaining patients had certain complications such as endocrine dysfunction, nerve palsy, and subdural effusion. We treated two patients whose tumors had grown to the level of the foramen magnum, one of which reached C2 levels. Both cases were treated with a neuroendoscopy. There were no deaths and no complications. Our cases are the longest follow-up of this type of craniopharyngioma.

Foramen Magnum Angle: A New Parameter for Basilar Invagination of Type B

OBJECTIVE

To describe the foramen magnum angle (FMA) as a new parameter for basilar invagination (BI) type B.

METHODS

The FMA was performed on sagittal slice of magnetic resonance imaging (MRI) as a line from the hard palate to the opisthion (angle vertex), and another line from the opisthion to the basion. The MRIs from 31 participants with BI type B and 96 controls were used. Intraclass correlation coefficient, descriptive data, and receiver operating characteristic (ROC) curve were used for statistical analysis at the 95% confidence interval.

RESULTS

The interobserver agreement of the FMA was 0.952. Patients with BI type B had a FMA significantly greater (25.9° ± 9.3°) than control participants (11.6° ± 4.9°) (P < 0.001). The area under the ROC curve showed a diagnostic value of 0.947. The FMA showed sensitivity 0.900 and specificity 0.854 for the cutoff criterion 17° (P < 0.001).

CONCLUSIONS

The FMA had an optimal diagnostic value that provided complementary evidence to investigate BI type B.

Comparison of two surgical techniques in Chiari Malformation Type 1 Patients: Duraplasty alone vs duraplasty with arachnoid dissection

OBJECT

Optimal surgical technique to restore the cerebrospinal fluid flow through the foramen magnum remains to be debated in Chiari malformation type 1 (CM-1) patients.

METHOD

This study included 46 patients with CM-1 who underwent surgical treatment by one of two methods: posterior fossa bone decompression (BD) with arachnoid preserving duraplasty (Group 1) and BD with duraplasty and arachnoid dissection (Group 2). Complaints of the patient population and neurological findings were assessed with Neck Disability Index (NDI) and Europe Quality of Life 5 Dimensions (EQ-5D) in pre- and postoperative periods.

RESULTS

NDI and EQ-5D scores improved in overall patient population and in each individual surgical group. Both groups showed a significant decrease in size of syringomyelia cavity. Complications resulting in recurrent treatments and re-operations occurred in 15% of patients (n = 7); six of them were from Group 2.

CONCLUSION

CM-1 patients benefit significantly from surgical treatment. Duraplasty should be included to surgical technique. Avoiding arachnoid dissection may lead to better results regarding complication rates.

Posterior fossa extra-axial variations of medulloblastoma: a pictorial review as a primer for radiologists

Manifestations of an atypical variant of medulloblastoma of the posterior fossa in extra-axial locations have been reported, and key questions concerning its interpretation have been raised previously. This review illustrated the clinico-radiological and histopathological features of the posterior fossa extra-axial medulloblastoma and described possible management strategies. We thoroughly reviewed all atypical anatomical locations of medulloblastoma reported within the posterior fossa and extra-axial spaces. The main characteristics of diagnostic imaging and histopathological results, primarily the distinctive radiopathological characteristics, were summarized to distinguish between intra- and extra-axial medulloblastoma, or pathologies mimicking this tumor. Most cases of posterior fossa extra-axial medulloblastoma have been reported in the cerebellopontine angle, followed by the tentorial and lateral cerebellar locations. The dural tail sign, which is commonly observed in meningioma, is rarely seen in intra- or extra-axial medulloblastoma and might be associated with other benign or malignant lesions. In addition to magnetic resonance imaging, the proposed new imaging techniques, including advances in modern neuroimaging modalities, were discussed, as potentially efficient modalities for characterizing extra-axial medulloblastoma. Radionuclide imaging and magnetic resonance perfusion imaging are practical alternatives to limit the number of differential diagnoses. We believe that medulloblastoma cases are likely under-reported because of publication bias and frequent tumors in unusual locations. Addressing these issues would help establish a more accurate understanding of this entity.

Chiari malformations in children: An overview

Chiari malformations encompass various radiological and clinical entities, sharing the herniation of the rhombencephalic structures through the foramen magnum as a common characteristic. They can be symptomatic or asymptomatic. The therapeutic strategies for these malformations differ on the basis of the diverse pathophysiologic processes that cause them. As Chiari malformations are caused by various pathophysiologic processes, they must be recognized promptly to select the best treatment for each single case.

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.

Long-term results of gamma knife radiosurgery for foramen magnum meningiomas

Outcomes of 37 patients of foramen magnum meningioma (FMM) were evaluated, and the related literature was reviewed to determine the efficacy of Gamma Knife radiosurgery (GKRS) for treating patients with FMM. We present the largest series reported from a single institution with the longest follow-up to date. The database of patients who underwent GKRS for FMM between 2007 and 2019 was evaluated retrospectively. A total of 37 patients with radiological and pathological features consistent with FMM were included in this series. Thirty-three patients were female, and 4 were male. The median age was 58 years (range, 23-74 years). The most common symptom at diagnosis was headache (64.9%). Twelve patients had a history of microsurgical resection. The median duration from the initial onset of symptoms to GKRS was 12 months (range 1-140 months). Among the 37 tumors, eight (21.6%) were located ventrally, 24 (64.9%) laterally, and five (13.5%) dorsally. The median target volume was 3.30 cm³ (range, 0.6-17.6 cm³). Thirty-five patients (95%) were treated with single fraction GKRS, and two patients (5%) were treated with hypofractionated GKRS. The median clinical follow-up was 80 months (range, 18-151 months), while the median radiological follow-up was 84 months (range, 18-144 months). At the last clinical follow-up after GKRS, 27 patients (73%) had improved symptoms, and none had worsened pre-GKRS symptoms. At the last radiological follow-up after GKRS, 23 tumors (62.2%) remained stable, 13 (35.1%) decreased in size, and 1 (2.7%) increased in size. Tumor control, including stable and regressed tumors, was achieved in 97.3% of patients. Our cohort demonstrates that GKRS is an effective and safe treatment for patients with either primary or recurrent/residual FMM.

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.

Endoscopic Transfontanellar Approach of a Cyst Anterior to the Brainstem Crossing the Foramen Magnum-Part II: Success of Multiple Fenestrations: Two-Dimensional Operative Video

Premature infants with severe germinal matrix/intraventricular hemorrhage are at high risk of posthemorrhagic ventricular dilation and hydrocephalus (Video 1). We report a 4-month-old premature infant with grade III intraventricular hemorrhage and compartmentalized hydrocephalus with an unusual craniospinal cyst. The cyst extended anteriorly from the mesencephalon to the posterior wall of C6, causing severe compression of the brainstem and spinal cord. An endoscopic procedure was performed first to achieve a unique cranial fenestration, which is detailed in "Endoscopic Transfontanellar Approach of a Cyst Anterior to the Brainstem Crossing the Foramen Magnum-Part I: Failure of Unique Fenestration." One month later the clinical picture recurred. Magnetic resonance imaging revealed hydrocephalus and cyst recurrence. A second procedure with endoscopic fenestration and shunt revision was needed. The same right transfontanellar approach was chosen, using a straight 30° endoscope. The procedure and surgical technique are explained in a step-by-step fashion. Extreme care was taken to align the head and the cervical spine. This allowed access to the extreme caudal cyst membrane posterior to C6 to create multiple transfixing fenestrations of the cyst. At 18-month follow-up, the child demonstrated almost normal neurological and psychomotor development with no cyst recurrence or hydrocephalus. Our report underlines the importance of performing multiple fenestrations of such cysts. We believe that performing a transfixing fenestration through the cyst allows cerebrospinal fluid flow and prevents recurrence, as, for instance, has been shown for suprasellar arachnoid cysts.

Sex estimation from foramen magnum parameters in adult Turkish population: A computed tomography study

Identification of skeletal relics is crucial for medicolegal purposes. Sex estimation is one of the critical parts providing the identification of skeletal relics. In forensic practice, sex estimation requires multidisciplinary studies of such as forensic medicine, anatomy, dentistry and radiology. Recently, radiological studies on this subject have been increasing with the developing technology. The objective of this study is to examine the usage of radiological dimensions of foramen magnum for sex estimation in human skulls by developing discriminant functions in Turkish population. We analyzed 600 (300 males and 300 females) Computerized Tomography (CT) images of Turkish individuals aged between 21 and 50. Four measurements were obtained from CT images. All measurements in males were significantly greater than in females, and they provided the higher sex classification accuracy. The area of the foramen magnum calculated by Radinsky's formula was the best measurement for sex estimation with a 75% accuracy rate. In conclusion, the CT images of foramen magnum show sexual dimorphism in our population. To use population specific data would be the most appropriate approach for sex estimation.

Neurenteric Cyst Masquerading as Acute Flaccid Paralysis in a 2-Month-Old Infant

BACKGROUND

Neurenteric cysts rarely present in infancy. Compressive myelopathy or meningitis are the usual presenting features of these cysts in infants.

CASE DESCRIPTION

We discuss a case of intradural extramedullary neurenteric cyst at the cervicomedullary junction in a 2-month-old infant who presented with features of acute onset flaccid upper limb weakness. The cyst was excised completely and the child improved.

CONCLUSIONS

Although rare, compressive lesions such as neurenteric cysts may present with acute flaccid paralysis in very young children. Differentiating from other causes and timely intervention bears an excellent outcome.

Ossified Anterior Foramen Magnum Meningioma: Report of Long-Term Surgical Outcome

BACKGROUND

Technical surgery-related issues for large ossified/calcified meningioma that encased one or both vertebral arteries located anterior to brainstem in the region of foramen magnum are discussed. Relatively long-term outcome of successful surgery is reported.

CASE DESCRIPTION

Three women were operated on for symptoms of progressive quadriparesis. Investigations revealed ossified meningioma located anterior to the brainstem. One or both vertebral arteries were encased within the confines of the tumor. Large size, bone-hard consistency, location anterior to the brainstem, and intimate vascular relationship made the surgery a formidable surgical problem. A midline posterior suboccipital approach was used to resect these tumors. Radical tumor resection was achieved in all cases successfully. Tumor drilling or heavy tumor breaking instruments were not necessary to debulk the tumor. Histologic examination in all 3 cases revealed psammomatous meningioma. During the follow-up period that ranged from 2 to 12 years, all 3 patients were leading a normal life, and there has been no documented recurrence in any case.

CONCLUSIONS

Successful resection of "ossified" meningioma is associated with satisfactory long-term clinical outcome.

New developments in the management of achondroplasia

Achondroplasia is the most common form of disproportionate short stature. A dominantly inherited FGFR3 mutation permanently activates the fibroblast growth factor receptor 3 (FGFR3) and its downstream mitogen-activated protein kinase (MAPK) signalling pathway. This inhibits chondrocyte differentiation and puts a break on growth plate function, in addition to causing serious medical complications such as foramen magnum and spinal stenosis and upper airway narrowing. A great deal has been learned about complications and consequences of FGFR3 activation and management guidance is evolving aimed to reduce the increased mortality and morbidity in this condition, particularly deaths from spinal cord compression and sleep apnoea in infants and small children. To date, no drugs are licensed for treatment of achondroplasia. Here, we report on the various substances in the drug development pipeline which target elements in molecular disease mechanism such as FGF (fibroblast growth factor) ligands, FGFR3, MAPK signalling as well as the C‑type natriuretic peptide receptor NPR‑B (natriuretic peptide receptor B).

Endoscopic Endonasal Approach to Foramen Magnum Meningioma: Two-Dimensional Surgical Video

Even for the most experienced neurosurgeons, foramen magnum meningiomas represent a surgical challenge owing to their delicate position surrounded by the brainstem, lower cranial nerves, and vertebral arteries. The treatment goal is gross total resection, but choosing the most appropriate approach is crucial. Basically, 3 surgical approaches are commonly used: posterolateral approach (far-lateral), anterolateral approach (extreme-lateral), and posterior midline approach. However, over the years, skull base surgery has evolved from standard open craniotomies to the use of microscopes and, more recently, to the development of endoscopic techniques. The endoscopic endonasal approach (EEA) permits a direct extradural route without brain retraction and shorter postoperative recovery. In contrast to the oral route, the soft palate and retropharyngeal soft tissues are preserved, allowing patients to resume a regular diet on the first postoperative day. Despite the advantages, the EEA is yet not widely used for treating foramen magnum meningiomas, even in cases where EEA use is possible. The EEA is feasible especially in cases with no vascular encasements and with a limited inferior extension allowing minimal manipulation of lower cranial nerves. Care must be taken with tumors with a more lateral and caudal extension (below the tip of the odontoid process), when a far lateral approach may be the best approach. In this surgical Video 1, we present the surgical details with a stepwise narrative of the EEA for ventrolateral foramen magnum meningiomas through an illustrative case of a 48-year-old woman. Institutional informed consent was obtained for surgery and publication of this video.

Foramen magnum meningiomas

The foramen magnum meningioma (FMM) is one of most challenging tumors among all the meningiomas because of its distinctive location, clinical course, insidious onset, and the relative large size of the tumor during presentation. These tumors are slow-growing and clinical symptoms vary according to involvement of different structures including the spinal cord, vertebral artery, lower cranial nerves, and medulla oblongata. Controversies regarding appropriate surgical approach for resection of tumor in this unique location continue. Tumors in the posterior or posterolateral region of the foramen magnum is accessible by midline suboccipital approach. The anterior and anterolateral tumors are encountered by various modifications of the far lateral approach. Drilling of condylar fossa is adequate in most of the cases as tumors often create a surgical corridor. However, an anterior tumor with significant extension on both sides of midline may require variable amounts of condyle resection. Here we review the FMMs with an emphasis on surgical approaches.

Mirror meningioma at foramen magnum: Enigma in management of a very rare case

Background:

We report a very rare case of bilateral foramen magnum mirror meningioma and discuss difficulties in managing the surgical challenge. To the best of our knowledge, mirror foramen magnum meningioma (FMM) has been reported only once in literature. FMMs are rare and also a great challenge for neurosurgeons due to the complex anatomy of this area. The purpose of this article is to illustrate the rare occurrence of bilateral meningioma in the foramen magnum and the difficulties in managing the surgical challenge.

Case Description:

A case of a 45-year-old female presented with neck pain, paresthesia in all four limbs, and difficulty in walking for 1 year duration. Magnetic resonance imaging revealed well-defined lobulated dural based mass lesion at foramen magnum on both sides. The left vertebral artery (VA) was encased within the lesion while the right VA was seen abutting it. Tumor was resected gross totally on the right side. However, during the resection of the medial part of the left side tumor, it was found to be adhered to the VA. Since the mass was adherent to the left VA, subtotal resection was done.

Conclusion:

There is no single best surgical approach for FMMs and the optimal approach should be defined according to the localization and the extent of the tumor to minimize the extent of resultant morbidity. Although complete excision of the tumor is the aim of surgery, it is safer to leave portions of tumor that is adherent to critical structures which can be managed by Gamma Knife radiosurgery.

The Clock Is Ticking - Brain Atrophy in Case of Acute Trauma?

Objective

Brain atrophy and brain herniation are gaining a lot of attention separately, but a limited amount of studies connected them together, and because of this, we are going to review and examine the subject in the current meta-analysis.

Methods

The authors collected data reporting brain atrophy of alcoholic and schizophrenic cause, as well as data on control patients, all of which was published on MEDLINE between 1996 and 2018. The included 11 articles were processed with a statistical program.

Results

We found that the pericerebral space is unequal among the groups, while the intracranial volume is strongly correlated to the biggest foramen of the body. The effect of this inequality, however, is expressed in emergency cases, where the patients with brain atrophy will have more time before the final stage of brain herniation.

Conclusion

The current study raises a controversial issue that requires careful investigation and high attention from the health care personnel.

Intradural Lipoma at the Craniocervical Junction Presenting with Progressing Hemiparesis: A Case Report

Intradural spinal lipomas are rare in an adult population. They are mostly asymptomatic and usually associated with spinal dysraphism in a pediatric population. We report a rare case of spinal lipoma without dysraphism and with progressing hemiparesis. A 60-year-old woman had incidental lipoma at the craniocervical junction observed for more than 5 years. Recently, she developed right-sided hemiparesis and sensory disturbance. Radiological studies revealed a large lipoma compressing the dorsal medulla and C1–C2 spinal cord. Standard midline suboccipital craniotomy and C1 laminectomy were performed, and the lipoma was removed subtotally. The lipoma showed severe adhesion to the dorsal medulla and C1 spinal cord; therefore, the excision was limited as internal debulking. Her neurological deficit subsided within 6 months after the decompressive surgery. Considering the benign nature of lipoma, internal decompression is a reasonable management for this lesion.

Craniocervical Rosai-Dorfman Disease Involving the Vertebral Artery: Case Report and Literature Review

BACKGROUND

Rosai-Dorfman disease (RDD), also known as sinus histiocytosis with massive lymphadenopathy, is a rare non-Langerhans cell reactive histiocytic disorder that rarely occurs in the central nervous system (CNS). Extranodal RDD most frequently involves the skin, upper respiratory tract, soft tissue, gastrointestinal tracts, bones, breast, and CNS.

CASE DESCRIPTION

RDD of the CNS infiltrates most commonly the dura of the sella, cavernous sinus, and the periclival regions. It is usually clinically and radiologically mistaken for meningioma because of its focal dural-based aspect. RDD is confirmed histologically by lymphoplasmacytic cells and histiocytes of varying size showing emperipolesis (lymphocytophagocytosis). To date, only 4 cases of RDD displaying spinal cord compression secondary to craniocervical junction involvement have been reported.

CONCLUSION

We report the case of a patient diagnosed with RDD localized at the foramen magnum extending to the base of the odontoid process and involving the V4 segment vertebral artery.

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.

Complete Resection of an Intradural Extramedullary Foramen Magnum Cavernous Malformation

Only few case reports of intradural extramedullary-located cavernous angiomas are available. This report describes an extra-axial hemorrhagic lesion located on the lateral surface of the medulla oblongata at the foramen magnum. Follow-up magnetic resonance imaing clearly demonstrated growth of the lesion, probably due to repetitive intralesional hemorrhaging. Initially, a right vertebral artery aneurysm or an arteriovenous malformation was suspected. Digital subtraction angiography excluded these differential diagnoses, although doubt remained concerning the possibility of a thrombosed aneurysm. Preoperatively, the lesion did not had the typical macroscopical aspect of a cavernoma and appeared rather as an expansive encapsulated multicystic vascular lesion. Nevertheless, pathologic analysis confirmed the diagnosis of a cavernous hemangioma. Complete microsurgical resection was obtained without neurologic impairment.