Proteins involved in regulating bone invasion in skull base meningiomas

Endoscopic Extended Transsphenoidal Surgery for Transbasal Tuberculum Sellae Meningioma: 2-Dimensional Operative Video

Transbasal meningiomas1 are a rare group of tumors that grow intracranially, invade the skull base, and propagate extracranially; they are usually located at the level of the olfactory cribra and sphenoid wing.1-4 Transbasal tuberculum sellae meningiomas are a subset of these tumors, which extend into the suprasellar and sphenoid regions. The traditional transcranial approach for some transbasal meningiomas has recently evolved toward the transnasal endoscopic approach, which allows the removal of both the intranasal and intracranial components, reducing the manipulation of the optic nerves and neurovascular structures. Nevertheless, specific anatomical criteria must be present; the knowledge of specific anatomy5,6 and the surgeon's experience are fundamental for reaching the most favorable outcome.7-11 In this video, we present the case of a 50-year-old woman with a history of progressive visual impairment and scotoma in the left inferotemporal quadrant. Radiological examinations suggested a transbasal tuberculum meningioma that extended into the suprasellar region, sphenoid sinus, and optic canals. An endoscopic transtuberculum approach with intraoperative visual-evoked potentials12 was performed, allowing an early devascularization with the preservation of the superior hypophyseal arteries and the removal of the component extending in the medial portion of both optic canals. The postoperative MRI documented a gross total resection without complications. The patient reported an immediate improvement of the visual symptoms. Histopathology documented a meningioma (CNS World Health Organization grade 1) with bone invasion. The patient consented to the procedure and to the publication of her image; Institutional Review Board approval was not required for this single case report.

A rare case of meningioma recurrence on a titanium mesh cranioplasty

Cranioplasty with titanium mesh provides a stable and cosmetically sound option for the correction of extensive skull bone defects following trauma or tumour surgery with osseous involvement. Meningiomas are for the most part benign lesions that are amenable to surgical cure, however lesions with extradural extension pose additional challenges not only due to increased technical difficulty in achieving gross total resection but also because of distinct biological behaviour. We describe the case of a 43-years-old woman that had been submitted to gross total resection of a WHO grade I falcine and superior sagittal sinus secretory meningioma with extradural and bone extension and cranioplasty with a titanium mesh who had a recurrence 4 years later as two tumour masses on top of the titanium mesh with no adjacent soft tissue invasion, and without dural involvement. To our knowledge, this is the first reported case of meningioma growth on top of titanium cranioplasty material. Seeded or incompletely removed tumoral cells might have exploited the biocompatibility of titanium to promote tumour regrowth.

Superficial meningioma with bone involvement: surgical strategies and clinical outcomes

INTRODUCTION

Meningiomas with bone involvement account for 4.5-17% of all intracranial meningiomas. Little is known about whether these meningiomas (WHO grade I) behave differently than meningiomas without bone involvement. We sought to study the relatively uncommon imaging manifestations of meningioma and to evaluate their clinical significance.

METHODS

A single-institution retrospective cohort study of surgically treated superficial meningioma patients between 2011 and 2022 was conducted. Age, sex, preoperative imaging, operative data, and surgical outcomes were reviewed. Imaging variables and outcomes were reported for patients with bone-invading meningiomas and compared with those with nonbone-invading meningiomas. Univariate analyses were also conducted.

RESULTS

Of 577 total superficial meningiomas treated surgically, 47 (8.1%) exhibited bone invasion. Most bone-invading meningiomas were parasagittal (n = 29, 61.7%). A total of 12.7% (n = 6) of patients with bone-invading meningioma had recurrence, whereas 9.1% (n = 48) of patients with non-bone-invading meningioma had recurrence (p = 0.426). No significant difference in the median time to recurrence was observed between patients with bone-invading meningiomas and patients with nonbone-invading meningiomas (69.8 months, Q1:53.1; Q3:81.4 months vs. 69.7 months, Q1:47.5; Q3:96.7; p = 0.638).

CONCLUSIONS

Superficial meningioma with bone involvement had similar outcomes compared to those of superficial meningioma without bone involvement. Hyperostosis in meningioma (WHO grade I) may not be a surrogate for aggressive meningioma behavior.

Osteopontin and Ki-67 expression in World Health Organization graded canine meningioma

Osteopontin (OPN) is a matrix protein involved in tumour initiation and progression. In human meningioma, OPN has been correlated with World Health Organization (WHO) grade, brain invasion and recurrence. The aim of this study was to investigate OPN as a possible malignancy marker in canine meningioma by correlating its expression to WHO grade and proliferative activity as measured by the Ki-67 labelling index (LI). Thirty-five formalin-fixed, paraffin-embedded canine meningioma samples were classified according to the current human WHO classification. Evaluation of OPN expression was performed by immunohistochemical (IHC) labelling and calculation of the OPN intensity score (IS), OPN IHC score and Allred score. The scores were compared with WHO grades, Ki-67 LI, location and invasiveness. Nineteen meningiomas were graded as WHO grade I (54.3%), nine as grade II (25.7%) and seven as grade III (20.0%). Twenty-six tumours were located intracranially, four were retrobulbar and five were spinal meningiomas. In all specimens OPN expression was detected in moderate to high degrees. Neither the OPN scores nor the Ki-67 LIs were correlated with WHO grades. However, the OPN IS and OPN IHC score were significantly higher in WHO grade I samples compared with grade II samples (P <0.05). The OPN IS and OPN IHC score were significantly lower in meningioma samples that invaded surrounding tissues (P = 0.01 and 0.019, respectively). The results indicate a generally high expression of OPN in canine meningioma independent of WHO grade. Further research into the role of OPN as a possible therapeutic target or predictor of recurrence is warranted.

Skull Base Meningiomas

Skull base meningiomas are among the most challenging meningiomas to treat clinically due to their deep location, involvement or encasement of adjacent essential neurovascular structures (such as key arteries, cranial nerves, veins, and venous sinuses), and their often-large size prior to diagnosis. Although multimodal treatment strategies continue to evolve with advances in stereotactic and fractionated radiotherapy, surgical resection remains the mainstay of treatment for these tumors. Resection of these tumors however is challenging from a technical standpoint, and requires expertise in several skull-base surgical approaches that rely on adequate bony removal, minimization of brain retraction, and respect for nearby neurovascular structures. These skull base meningiomas originate from a variety of different structures including, but are not limited to: the clinoid processes, tuberculum sellae, dorsum sellae, sphenoid wing, petrous/petroclival area, falcotentorial region, cerebellopontine angle, and foramen magnum. In this chapter, we will cover the common anatomical areas in the skull base from which these tumors arise, and the specific or optimal surgical approaches and other treatment modalities for meningiomas in these such locations.

Benign Meningioma With Rare Radiological and Behavioral Features

BACKGROUND

Meningiomas are usually dura-based primary nonmalignant neoplasms of the central nervous system. It is extremely rare that a meningioma is located at the convexity of the brain, but shows no dura attachment and causes osteolysis of the skull.

CASE PRESENTATION

A 57-year-old woman presented with an incidentally discovered scalp lump on the head. Neurological deficits were not found. Radiological examination revealed a localized osteolytic lesion in the right parietal bone, which was initially diagnosed as a bone tumor and was surgically resected. At surgery, a tumor mass was found located at the brain convexity without dura attachment. It was tightly attached to the brain parenchyma and had no distinct boundary from the brain. The mass was rather small, but resulted in significant osteolysis of the skull and destruction of the dura. Simpson grade I resection of the tumor was performed. Histological and immunohistochemical results indicated a meningothelial meningioma.

CONCLUSIONS

Both preoperative and intraoperative diagnoses are difficult for this case. Knowledge of this case is crucial for clinicians to be aware of this entity because it can be easily confused with bone tumors. Further research on the relationship between meningioma and bone metabolism is required to investigate the mechanism of osteolysis.

Bone Invasive Meningioma: Recent Advances and Therapeutic Perspectives

Meningioma is the most common primary neoplasm of the central nervous system (CNS). Generally, these tumors are benign and have a good prognosis. However, treatment can be challenging in cases with aggressive variants and poor prognoses. Among various prognostic factors that have been clinically investigated, bone invasion remains controversial owing to a limited number of assessments. Recent study reported that bone invasion was not associated with WHO grades, progression, or recurrence. Whereas, patients with longer-recurrence tended to have a higher incidence of bone invasion. Furthermore, bone invasion may be a primary preoperative predictor of the extent of surgical resection. Increasing such evidence highlights the potential of translational studies to understand bone invasion as a prognostic factor of meningiomas. Therefore, this mini-review summarizes recent advances in pathophysiology and diagnostic modalities and discusses future research directions and therapeutic strategies for meningiomas with bone invasion.

Primary Intraosseous Osteolytic Meningioma with Aggressive Clinical Behaviour: Clinico-Pathologic Correlation and Proposed New Clinical Classification

(1) Introduction: Primary intraosseous osteolytic meningiomas (PIOM) are non-dural-based tumors predominantly presenting an osteolytic component with or without hyperostotic reactions. They are a subset of primary extradural meningiomas (PEM). In this study, we present a peculiar case with a systematic literature review and propose a new classification considering the limitations of previous classification systems. (2) Materials and Methods: Using a systematic search protocol in Google Scholar, PubMed, and Scopus databases, we extracted all case studies on PIOM published from inception to December 2020. A 46-year-old female patient form Dhaka, Bangladesh, was also described. The search protocol was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. (3) Results: Here, we present a 46-year-old female patient with PIOM who successfully underwent bifrontal craniotomy and gross total removal (GTR) of the tumor. At 6-month follow-up, no tumor recurrence was shown. Including our new case, 55 total cases from 47 articles were included in the analysis. PIOMs were in closer frequency among males (56.4%) and females (43.6%). The most common tumor location was the frontal and parietal calvarium, most commonly in the frontal bone (29.1%). Surgical resection was the predominant modality of treatment (87.3%); only 1.8% of patients were treated with radiotherapy, and 5.4% received a combination of surgery and radiotherapy. Gross total resection (GTR) was achieved in 80% of cases. Extracranial extension was reported in 41.8% of cases, dural invasion in 47.3%, and recurrence in 7.3%. Whole-body 68 Ga-DOTATOC PET/CT has also been reported as a useful tool both for differential diagnosis, radiotherapy contouring, and follow-up. Current treatments such as hydroxyurea and bevacizumab have variable success rates. We have also suggested a new classification which would provide a simple common ground for further research in this field. (4) Conclusions: Surgical resection, especially GTR, is the treatment of choice for PIOM, with a high GTR rate and low risk of complications and mortality. More research is needed on the differential diagnosis and specific treatment of PIOM.

Comprehensive proteomic analysis reveals distinct functional modules associated with skull base and supratentorial meningiomas and perturbations in collagen pathway components

Meningiomas are brain tumors that originate from the meninges and has been primarily classified into three grades by the current WHO guidelines. Although widely prevalent and can be managed by surgery there are instances when the tumors are located in difficult regions. This results in considerable challenges for complete surgical resection and further clinical management. While the genetic signature of the skull base tumors is now known to be different from the non-skull base tumors, there is a lack of information at the functional aspects of these tumors at the proteomic level. Thus, the current study thereby aims to obtain mechanistic insights between the two radiologically distinct groups of meningiomas, namely the skull base & supratentorial (non-skull base-NSB) regions. We have employed a comprehensive mass spectrometry-based label-free quantitative proteomic analysis in Skull base and supratentorial meningiomas. Further, we have used an Artificial Neural Networking employing a sparse Multilayer perceptron (MLP) architecture to predict protein concordance. A patient-derived spectral library has been employed for a novel peptide-level validation of proteins that are specific to the radiological regions using the SRM assay based targeted proteomics approach. The comprehensive proteomics enabled the identification of nearly 4000 proteins with high confidence (1%FDR ≥ 2 unique peptides) among which 170 proteins were differentially abundant in Skull base vs Supratentorial tumors (p-value ≤0.05). In silico analysis enabled mapping of the major alterations and hinted towards an overall perturbation of extracellular matrix and collagen biosynthesis components in the non-skull base meningiomas and a prominent perturbation of molecular trafficking in the skull base meningiomas. Therefore, this study has yielded novel insights into the functional association of the proteins that are differentially abundant in the two radiological subgroups. SIGNIFICANCE: In the current study, we have performed label-free proteomic analysis on fresh frozen tissue of 14 Supratentorial (NSB) and 7 Skull base meningiomas to assess perturbations in the global proteome, we have further employed an in-depth in silico analysis to map the pathways that have enabled functional mapping of the differentially abundant proteins in the Skull base and Supratentorial tumors. The findings from the above were also subjected to a machine learning-based neural networking to find out the proteins that have the most concordance of occurrence to determine the most influential proteins of the network. We further validated the differential abundance of identified protein markers in a larger patient cohort of Skull base and Supratentorial employing targeted proteomics approach to validate key protein candidates emerging from ours and other recent studies. The previous studies that have explored the skull base and convexity meningiomas have been able to reveal alterations in the genetic mutations in these tumor types. However, there are not many studies that have explored the functional aspects of these tumors, especially at the proteome level. We have attempted for the first time to map the functional modules associated with altered proteins in these tumors and have been able to identify that there is a possibility that the Skull base meningiomas to be considerably different from the Non-skull base (NSB) tumors in terms of the perturbed pathways. Our study employed global as well as targeted proteomics to examine the proteomic alterations in these two tumor groups. The study indicates that proteins that were more abundant in Skull base tumors were part of molecular transport components, non-skull base proteins majorly mapped to the components of extracellular matrix remodeling pathways. In conclusion, this study substantiates the distinction in the proteomic signatures in the skull base and supratentorial meningiomas paving way for further investigation of the identified markers for determining if some of these proteins can be used for therapeutic interventions for cases that pose considerable challenges for complete resection.

Brain-invasive meningiomas: molecular mechanisms and potential therapeutic options

Meningiomas are the most commonly diagnosed benign intracranial adult tumors. Subsets of meningiomas that present with extensive invasion into surrounding brain areas have high recurrence rates, resulting in difficulties for complete resection, substantially increased mortality of patients, and are therapeutically challenging for neurosurgeons. Exciting new data have provided insights into the understanding of the molecular machinery of invasion. Moreover, clinical trials for several novel approaches have been launched. Here, we will highlight the mechanisms which govern brain invasion and new promising therapeutic approaches for brain-invasive meningiomas, including pharmacological approaches targeting three major aspects of tumor cell invasion: extracellular matrix degradation, cell adhesion, and growth factors, as well as other innovative treatments such as immunotherapy, hormone therapy, Tumor Treating Fields, and biodegradable copolymers (wafers), impregnated chemotherapy. Those ongoing studies can offer more diversified possibilities of potential treatments for brain-invasive meningiomas, and help to increase the survival benefits for patients.

Radiomic features of magnetic resonance images as novel preoperative predictive factors of bone invasion in meningiomas

PURPOSE

Bone invasion in meningiomas is a prognostic determinant, and a priori knowledge may alter surgical techniques. Here, we aim to predict bone invasion in meningiomas using radiomic signatures based on preoperative, contrast-enhanced T1-weighted (T1C) and T2-weighted (T2) magnetic resonance imaging (MRI).

METHODS

In this retrospective study, 490 patients diagnosed with meningiomas, including WHO grade I (448cases), grade II (38cases), and grade III (4cases), were enrolled and 213 out of 490 cases (43.5 %) had bone invasion. The patients were randomly divided into training (n = 343) and test (n = 147) datasets at a 7:3 ratio. For each patient, 1227 radiomic features were extracted from T1C and T2, respectively. Spearman's correlation and least absolute shrinkage and selection operator (LASSO) regression analyses were performed to select the most informative features. Subsequently, a 5-fold cross-validation was used to compare the performance of different classification algorithms, and logistic regression was chosen to predict the risk of bone invasion.

RESULTS

Eight radiomic features were selected from T1C and T2 respectively, and three models were built using radiomic features. The radiomic models derived from T1C alone or a combination of T1C and T2 had the best performance in predicting risk of bone invasion, with areas under the curve in the training dataset of 0.714 [95 % CI, 0.660-0.768] and 0.722 [95 % CI, 0.668-0.776] and in the test datasets of 0.715 [95 % CI, 0.632-0.798] and 0.713 [95 % CI, 0.628-0.798], respectively.

CONCLUSIONS

The radiomic model may aid clinicians with preoperative prediction of bone invasion by meningiomas, which can help in predicting prognosis and devising surgical strategies.

Fibrous Meningioma with Skull Invasion

In patients with meningiomas, the presence of skull invasion is known to be a predictor of aggressive clinical behavior, which may negatively influence patient outcomes. In the present report, we discuss a case of fibrous meningioma with skull invasion. A 42-year-old woman was referred to our department presenting with hyperostosis in the right parietal bone. T1-weighted magnetic resonance imaging with gadolinium enhancement revealed prominent enhancement of the intraosseous lesion and dura mater. Following the removal of the tumor body and bone lesion, we performed immunohistochemical staining for osteopontin (OPN), matrix metalloproteinase- 2 (MMP2), and integrin β-1 (CD29). The tumor body was immunoreactive for OPN and CD29, but not MMP2, whereas, the bone lesion was immunoreactive for all the three antigens. The present case suggests that OPN, MMP2, and CD29 play key regulatory roles in bone invasion.

Challenging the osseous component of sphenoorbital meningiomas

BACKGROUND

Intraosseous growth is a unique feature of sphenoorbital meningiomas (SOM). Its close relation to neurovascular structures limits complete surgical resection and possibly contributes to the high recurrence rate.

OBJECTIVE

To evaluate the growth behavior of intraosseous remnants and develop a protocol for precise intraoperative visualization of intraosseous SOM.

METHODS

We included 31 patients operated for SOM from 2004 to 2017. The growth velocity of the intraosseous tumor component was volumetrically calculated in 20 cases. To improve accuracy of image guidance, we implemented a specialized bone surface-based registration algorithm. For intraoperative bone visualization, we included CT in multimodality continuous image guidance in 23 patients. The extent of resection (EOR) was compared with a standard MR-only navigation group (n = 8).

RESULTS

In 11/20 cases (55%), a progressive regrowth of the intraosseous SOM remnant was noted during a mean follow-up of 52 months (range 20-132 months). We observed a mean increase of 6.2 cm3 (range 0.2-23.7 cm3) per patient and side during the follow-up period. Bone surface-based registration was significantly more accurate than skin surface-based registration (mean 0.7 ± 0.4 mm and 1.9 ± 0.7 mm, p < 0.001). The EOR of the intraosseous component was significantly higher using CT + MRI navigation compared with controls (96% vs. 81%, p = 0.044).

CONCLUSION

Quantitative assessment of the biological behavior of intraosseous remnants revealed a continuous slow growth rate independent of the soft tumor component of more than half of SOM. According to our data, application of a multimodal image guidance provided high accuracy and significantly increased the resection rate of the intraosseous component of SOM.

Brain invasion in meningiomas-clinical considerations and impact of neuropathological evaluation: a systematic review

With the release of the 2016 edition of the World Health Organization (WHO) Classification of Central Nervous System Tumors, brain invasion in meningiomas has been added as a stand-alone criterion for atypia and can therefore impact grading and indirectly adjuvant therapy. Regarding this rising clinical importance, we have reviewed the current knowledge about brain invasion with emphasis on its implications on current and future clinical practice. We found various definitions of brain invasion and approaches for evaluation in surgically obtained specimens described over the past decades. This heterogeneity is reflected by weak correlation with prognosis and remains controversial. Similarly, associated clinical factors are largely unknown. Preoperative, imaging-guided detection of brain invasion is unspecific, and intraoperative assessment using standard and new high-magnification microscopic techniques remains imprecise. Despite the increasing knowledge about molecular alterations of the tumor/ brain surface, pharmacotherapeutic options targeting brain invasive meningiomas are lacking. Finally, we summarize the impact of brain invasion on histopathological grading in the WHO classifications of brain tumors since 1979.In conclusion, standardized neurosurgical sampling and neuropathological analyses could improve diagnostic reliability and reproducibility of future studies. Further research is needed to improve pre- and intraoperative visualization of brain invasion and to develop adjuvant, targeted therapies.

DICER governs characteristics of glioma stem cells and the resulting tumors in xenograft mouse models of glioblastoma

The RNAse III endonuclease DICER is a key regulator of microRNA (miRNA) biogenesis and is frequently decreased in a variety of malignancies. We characterized the role of DICER in glioblastoma (GB), specifically demonstrating its effects on the ability of glioma stem-like cells (GSCs) to form tumors in a mouse model of GB. DICER silencing in GSCs reduced their stem cell characteristics, while tumors arising from these cells were more aggressive, larger in volume, and displayed a higher proliferation index and lineage differentiation. The resulting tumors, however, were more sensitive to radiation treatment. Our results demonstrate that DICER silencing enhances the tumorigenic potential of GSCs, providing a platform for analysis of specific relevant miRNAs and development of potentially novel therapies against GB.

Transfrontal-Sinus-Subcranial Approach to Olfactory Groove Meningiomas: Surgical Results and Clinical and Functional Outcome in a Consecutive Series of 21 Patients

BACKGROUND

The transfrontal-sinus-subcranial approach (TFSSA) allows for direct exposure and removal of olfactory groove meningiomas (OGMs), without any brain retraction. Compared with other skull base approaches (e.g., fronto-orbitobasal, transbasal, subcranial, fronto-orbitozygomatic, and one-and-half approach), it could offer the same advantages but is less invasive.

OBJECTIVE

We report the results in a series of 21 consecutive patients with OGMs and operated on through TFSSA, to propose a viable alternative approach.

METHODS

Mean maximum tumor diameter was 45.9 ± 3.4 mm (range, 25-70 mm). The aim of surgery was Simpson grade I removal. Surgical, clinical, and functional outcomes were reported. Mean follow-up was 87 ± 7 months (range, 36-176 months).

RESULTS

In all patients, magnetic resonance imaging after surgery confirmed complete tumor removal. The recurrence-free survival rate was 100% and 85.7% at 5 and 10 years, respectively. Surgery-related mortality and major morbidity were 0% and 4.8%, respectively. Risk of anosmia significantly correlates with meningioma size (P < 0.001) and smell sense was preserved only in patients with tumors less than 4 cm in maximum diameter (4/7; 57.1%). A significant improvement of Mini Mental Standard Examination score was recorded at follow-up (P < 0.001) and no patients worsened their cognitive profile. Visual function improved in 7/8 (87.5%). Karnofsky Performance Scale score after surgery significantly increased (P < 0.001). According to the Glasgow Outcome Score, good outcome was achieved in 20 patients (95.2%).

CONCLUSIONS

Based on reported results, TFSSA allows complete tumor removal with good outcome and low complication rate. It may be proposed as a safe and effective approach to treat large and giant OGMs.

Nano-mechanical signature of brain tumours

Glioblastoma (GBM) and meningothelial meningioma (MM) are the most frequent malignant and benign brain lesions, respectively. Mechanical cues play a major role in the progression of both malignancies that is modulated by the occurrence of aberrant physical interactions between neoplastic cells and the extracellular matrix (ECM). Here we investigate the nano-mechanical properties of human GBM and MM tissues by atomic force microscopy. Our measures unveil the mechanical fingerprint of the main hallmark features of both lesions, such as necrosis in GBM and dural infiltration in MM. These findings have the potential to positively impact on the development of novel AFM-based diagnostic methods to assess the tumour grade. Most importantly, they provide a quantitative description of the tumour-induced mechanical modifications in the brain ECM, thus being of potential help in the search for novel ECM targets for brain tumours and especially for GBM that, despite years of intense research, has still very limited therapeutic options.

Advances in computed tomography evaluation of skull base diseases

Introduction Computed tomography (CT) is a key component in the evaluation of skull base diseases. With its ability to clearly delineate the osseous anatomy, CT can provide not only important tips to diagnosis but also key information for surgical planning.

Objectives The purpose of this article is to describe some of the main CT imaging features that contribute to the diagnosis of skull base tumors, review recent knowledge related to bony manifestations of these conditions, and summarize recent technological advances in CT that contribute to image quality and improved diagnosis.

Data Synthesis Recent advances in CT technology allow fine-detailed evaluation of the bony anatomy using submillimetric sections. Dual-energy CT material decomposition capabilities allow clear separation between contrast material, bone, and soft tissues with many clinical applications in the skull base. Dual-energy technology has also the ability to decrease image degradation from metallic hardwares using some techniques that can result in similar or even decreased radiation to patients.

Conclusions CT is very useful in the evaluation of skull base diseases, and recent technological advances can increase disease conspicuity resulting in improved diagnostic capabilities and enhanced surgical planning.

Meningiomas of the cerebellopontine angle: radiological differences in tumors with internal auditory canal involvement and their influence on surgical outcome

This study explored the clinical, radiological, and pathological characteristics of cerebellopontine angle (CPA) meningiomas with internal auditory canal (IAC) involvement. The pre- and postoperative MR images of 193 consecutive patients with pathologically diagnosed meningioma centered around the IAC were analyzed, focusing on changes in the IAC, maximal axial tumor volume, peritumoral brain edema, and postoperative residual tumor. Patient age, sex, tumor volume, postoperative residual tumor, and pathological subtype were compared in patients with and without IAC involvement by the tumor and among the different types of IAC involvement. The results showed that the 71 patients (36.8%) with IAC involvement had a higher ratio of peritumoral edema (χ²=5.922, P=0.015), postoperative residual tumor (χ²=22.183, P< 0.001), and a predominance of the meningothelial subtype (χ²=5.89, P=0 .015). Peritumoral edema was a risk factor for IAC involvement (P=0.016, OR=2.186). Radiologically, IAC involvement could be distinguished as intruding (31%, 22/71), filled (29.6%, 21/71), and dilated (39.4%, 28/71). Patients with intruding IAC were significantly older (54.5±9.54 years, P=0.021) and had the lowest postoperative residual tumor values (42%, χ²=7.865, P= 0.005), while those with filled IAC were more likely to be female (95%, χ²=9.404, P=0.009).Our observations provide the basis for a morphological classification of IAC involvement by CPA meningiomas and further insight into the clinical features of these tumors.

Indicators of a Reduced Intercarotid Artery Distance in Patients Undergoing Endoscopic Transsphenoidal Surgery

Objective To identify clinicopathologic factors associated with a reduced intercarotid distance (ICD) and subgroups at risk for internal carotid artery injury during transsphenoidal surgery. Design A retrospective case-control study. Setting This study was conducted at the McGill University Health Centre, a university-affiliated tertiary care center. Participants Patients with a sellar or parasellar tumor and nontumor controls were included in the study. Main Outcome Measures The smallest distance between the internal carotid arteries at the clival, cavernous, and paraclinoid segments on coronal magnetic resonance imaging was measured. Demographic profiles, cephalometric measurements, tumor dimensions, and sphenoid configuration were assessed as potential determinants of the ICD. Results A total of 212 cases and 34 controls were analyzed. Widening of the ICD at the three segments of the internal carotid arteries was found in patients with pituitary macroadenomas (p < 0.01). Patients with a growth hormone-secreting adenoma had a markedly reduced ICD at the clivus compared with controls (1.59 cm versus 1.77 cm; p = 0.02; 95% confidence interval [CI], 0.03-0.32). The paraclinoid ICD was reduced in patients with an anterior fossa meningioma (1.24 cm versus 1.33 cm; p = 0.04; 95% CI, 0.01-0.45). Conclusion Identifying clinicopathologic factors affecting the ICD can help surgeons recognize constraints to endoscopic access of the skull base and avoid inadvertent arterial injury.