Olfactory Groove Meningioma: Report of 99 Cases Surgically Treated at the Catholic University School of Medicine, Rome

Endoscopic endonasal approach for olfactory groove meningioma resection: Strategies and outcomes in a retrospective case series

OBJECTIVE

Though the endoscopic endonasal approach (EEA) is a widely accepted treatment for skull base tumors, the specific use of EEA for olfactory groove meningiomas (OGMs) is debated, with variable outcomes reported in the literature. We review the surgical results of OGM resections for one surgeon including the operative approach, surgical nuances, and outcomes, with a focus on factors relating to patient selection which favor EEA over transcranial approaches.

METHODS

We retrospectively reviewed thirteen cases of endoscopic endonasal resection of olfactory groove meningiomas. Patient characteristics, clinical characteristics, surgical outcomes, and complications were analyzed. Extent of resection was determined based on volumetric analysis of pre- and postoperative MRI.

RESULTS

Anatomic characteristics that render a tumor difficult to access fully are lateral extension beyond the mid-orbit and anterior extension to the falx. Simpson Grade I resection was achieved in 11/13 (84.6 %) cases. Mean pre-operative tumor volume was 8.99 cm3 (range 2.19-16.79 cm3), and 92 % of tumors were WHO grade I. We demonstrate 2 cases of smell preservation, possible with small unilateral tumors and tumors that are confined to either the anterior or posterior portion of the cribriform plate. The post-operative CSF leak rate was 7.7 %, without prophylactic lumbar CSF drainage. The mortality rate was 7.7 % (n = 1) after infectious complications following CSF leak.

CONCLUSIONS

Endoscopic endonasal resection of olfactory groove meningiomas is an effective and safe operative method with outcomes and complication rates comparable to transcranial approaches. Key considerations include careful patient selection and familiarity with technical nuances of endoscopic endonasal approach for this specific tumor type.

Simple and safe resection of the crista galli

A critical procedure in the transcribriform approach is the resection of the crista galli. However, the standard technique for crista galli resection has several disadvantages. We reviewed the cases of patients with olfactory neuroblastomas who underwent an endoscopic endonasal transcribriform approach using a newly developed technique for crista galli resection. We performed a cadaveric study to measure the superior accessibility limits using the proposed method. We included 38 patients with olfactory neuroblastomas in this study. The tumor invaded the posterior crista galli in four patients. The anterior end of the crista galli was not invaded by the tumor. Our cadaveric study showed that the dura was approachable to the point that was 7.4 ± 1.3 mm superior and 23.2 ± 7.2 mm lateral to the foramen cecum following crista galli removal. By resecting the crista galli in advance, manipulation of the superior dura became feasible.

Fully Endoscopic Supraorbital Approach for Anterior Cranial Base Meningiomas

BACKGROUND

Anterior cranial base meningiomas include those meningiomas originating from the tuberculum sellae, the planum sphenoidale, or the olfactory groove, with surgical excision being the main treatment modality for these tumors. Conventional microscopic and endoscope-assisted versions of the supraorbital keyhole approach via an eyebrow incision emerged into minimally invasive options that are frequently utilized nowadays for treating these tumors. At the early attempts of endoscope-assisted cranial surgery, it was noted that rigid endoscopes enabled overcoming the problem of suboptimal visualization when small exposures are used. The technical specifications and design of the currently available rigid endoscopes are associated with a group of unique features that define the endoscopic view and lay the basis for its superiority over the microscopic view during brain surgery. Notwithstanding, the fully endoscopic or endoscope-controlled version of the supraorbital keyhole approach is not routinely practiced by neurosurgeons, with few series published so far. In this chapter we elaborate on the surgical technique and nuances of the fully endoscopic supraorbital approach for anterior cranial base meningiomas.

METHODS

From a prospective database of endoscopic procedures maintained by the senior author, clinical data, imaging studies, operative charts, and videos of cases undergoing fully endoscopic excision of anterior cranial base meningiomas via supraorbital approach were retrieved and analyzed. The pertinent literature was also reviewed.

RESULTS

The surgical technique of the fully endoscopic supraorbital approach for anterior cranial base meningiomas was formulated.

CONCLUSION

The fully endoscopic supraorbital approach for anterior cranial base meningiomas has many advantages over the conventional procedures. In our hands, the technique has proven to be feasible, efficient, and minimally invasive with excellent results.

Long-term postoperative health-related quality of life in patients with subfrontal meningiomas

OBJECTIVE

Subfrontal meningiomas grow insidiously in areas with high cerebral compliance and a relative scarcity of eloquent function. Symptoms develop progressively, are nonspecific, and include anosmia, changes in personality and cognition, depressive symptoms, headaches, visual disturbances, and seizures. Patients with subfrontal meningiomas carry the highest risk of developing psychological symptoms, which makes patient-reported outcome in terms of long-term health-related quality of life (HRQOL), anxiety, and depression of particular importance. This observational study aimed to investigate long-term HRQOL, anxiety, and depression in patients with subfrontal meningiomas who underwent a bifrontal craniotomy (subfrontal) approach between 2008 and 2017 at a single tertiary center. Correlations between preoperative, perioperative, and postoperative factors and HRQOL, anxiety, and depression were analyzed to detect prognostic factors.

METHODS

Seventy-seven consecutive patients who underwent operations at Rigshospitalet, Copenhagen, Denmark, between 2008 and 2017 were retrospectively analyzed. Patients were prospectively invited to respond to the Functional Assessment of Cancer Therapy-General, Functional Assessment of Cancer Therapy-Brain, and Hospital Anxiety and Depression Scale. Information regarding preoperative, perioperative, and postoperative factors were collected from the patients' medical records and scans.

RESULTS

Patients with subfrontal meningiomas exhibited better HRQOL and lower levels of anxiety and depression than general populations and other meningioma and glioblastoma cohorts. The only statistically significant prognostic factors for long-term HRQOL were number of symptoms at diagnosis and whether patients were discharged home or to a local hospital postoperatively. Tumor and peritumoral brain edema volumes were not prognostic factors.

CONCLUSIONS

Patients with subfrontal meningiomas exhibited better long-term postoperative HRQOL and were less likely to have anxiety or depression than the reference populations. This information on long-term prognosis is very valuable for patients, next of kin, and neurosurgeons and has not been previously studied in detail.

Pterional Approach for Anterior Skull Base Midline Meningiomas against "The More The Merrier" Approach: An Institutional Experience

Objective  Anterior midline skull base meningiomas involving olfactory groove, planum sphenoidale, and tuberculum sellae were usually managed with bifrontal craniotomy until the dawn of advanced microsurgical techniques. With the emergence of microsurgical techniques, midline meningiomas could be tackled solely from a unilateral pterional approach. We present our experience with pterional approach in managing anterior skull base midline meningiomas, including the technical nuances and outcomes. Methods  Fifty-nine patients who underwent excision of anterior skull base midline meningiomas through a unilateral pterional craniotomy between 2015 and 2021 were retrospectively analyzed. The surgical technique and patient outcomes in the context of visual, behavioral, olfaction, and quality of life were evaluated during the follow-up. Results  A total of 59 consecutive patients were assessed over an average follow-up period of 26.6 months. Twenty-one (35.5%) patients had planum sphenoidale meningioma. Olfactory groove and tuberculum sellae meningioma groups consist of 19 (32%) patients each. Visual disturbance was the predominant symptom with almost 68% of patients presented with it. A total of 55 (93%) patients had complete excision of the tumor with 40 patients (68%) achieving Simpson grade II excision, and 11 (19%) patients had Simpson grade I excision. Among operated cases, 24 patients (40%) had postoperative edema among which 3 (5%) patients had irritability and 1 patient had diffuse edema requiring postoperative ventilation. Only 15 (24.6%) patients had contusion of the frontal lobe and were managed conservatively. Five patients (50%) with seizures had an association with contusion. Sixty-seven percent of patients had improvements in vision and 15% of patients had a stable vision. Only eight (13%) patients had postoperative focal deficits. Ten percent of patients had new-onset anosmia. The average Karnofsky score was improved. Only two patients had recurrence during follow-up. Conclusion  A unilateral pterional craniotomy is a versatile approach for the excision of anterior midline skull base meningioma, even for the larger lesions. The ability of this approach in the visualization of posterior neurovascular structures at the earlier stages of surgery while avoiding the opposite frontal lobe retraction and frontal sinus opening makes this approach more preferable over the other approaches.

Surgical Morbidity in Relation to the Surgical Approach for Olfactory Groove Meningiomas-A Pooled Analysis of 1016 Patients and Proposal of a New Reporting System

Background: There is currently no consensus in the field regarding whether a frontal or lateral approach is superior for microsurgical resection of olfactory groove meningiomas (OGM). Due to the lack of uniformity in classifying lesions and inherent differences in reporting outcomes after varying operative approaches, the best practice for approaching these lesions is yet to be determined. Objective: This study aimed to assess various surgical approaches undertaken for OGMs, investigate procedural aspects influencing the extent of resection, and analyze the respective complication rate associated with each approach. We performed a comprehensive literature review of presenting signs and symptoms in OGM patients, their surgical management, and the reported surgical outcomes. To address the lack of uniform data reporting across studies and to take more recent translational studies into account, we developed a new classification system for OGMs that can remedy the existing deficiencies in comparability of reporting. Methods: We conducted a PRISMA-guided literature search for surgical reports on OGMs published in the MRI era using broad search terms such as 'olfactory groove meningioma' and 'surgery', which yielded 20,672 results. After title screening and removal of duplicates, we assessed 871 studies on the specific surgical management of olfactory groove meningiomas. Following the application of exclusion criteria and abstract screening, a set of 27 studies was chosen for the final analysis of a pooled cohort of these reported patient outcomes. Results: The final twenty-seven studies included in our in-depth analysis identified a total of 1016 individual patients who underwent open microsurgical resection of OGMs. The approaches used included: pterional/unilateral, bifrontal with variations, and anterior interhemispheric approaches. Across all studies, gross total resection (Simpson Grades I or II) was achieved in 91.4% of cases, and subtotal resection (Grades III and IV) was reported in 8.6% of cases. A cumulative twenty-seven percent of surgical OGM patients sustained some form of complications. Minor issues accounted for 22.2% (CSF leak, seizures, infection, transient cranial nerve palsies, hydrocephalus), whereas major issues comprised 4.7% (hemorrhage, ischemic infarct, malignant cerebral edema). We then examined the correlation between these complications and the surgical approach chosen. Among pooled cohort of 426 patients who underwent unilateral approaches, 14% experienced minor complications, and 2.1% experienced major complications. For the mixed cohort of 410 patients who underwent bifrontal approaches, 24.6% experienced minor complications, and 7% experienced major complications. Conclusions: Unilateral approaches appear to have lower complication rates for the resection of OGMs compared to bilateral approaches. However, the extent of resection is not uniformly reported, making it difficult to identify differences. The use of an improved preoperative classification and scoring system can help establish a more coherent system to select the most suitable approach and to uniformly report surgical outcomes, such as EOR and complication rates specific to a given OGM and its surgical approach.

Visual Loss As Primary Manifestation of Olfactory Groove Meningioma

Differential diagnosis of vision loss in a space-occupying lesion can be exhaustive. Olfactory groove meningioma (OGM) is a rare, benign, slow-growing tumour originating from the anterior cranial base. OGM is one of the differential diagnoses of intracranial tumours. We report a case of an OGM compressing the optic nerve and frontal lobe causing bilateral vision loss for six months. Multidisciplinary management by ophthalmologists, neurosurgeons, radiologists, and pathologists led to the diagnosis and tumour resection of OGM in the patient. Possible mechanisms of vision loss, imaging features, and treatment are discussed in this report.

Unilateral Supraorbital Keyhole Craniotomy Avoiding the Frontal Sinus for Large and Giant Olfactory-Groove Meningiomas: A Case Series

OBJECTIVE

There are several different approaches to large and giant olfactory-groove meningiomas (OGMs). Each approach has advantages and disadvantages. We present our series using a unilateral supraorbital keyhole approach avoiding the frontal sinus for the resection of large and giant OGMs without the use of fixed brain retractors or orbital rim removal.

MATERIALS AND METHODS

All consecutive patients operated on for large (>3 cm in largest diameter) and giant (>5 cm) OGMs by the senior author from 2016 to 2021 were prospectively identified and retrospectively reviewed. Patients who were operated on using an endoscopic endonasal approach were excluded. No fixed retraction was used.

RESULTS

In total, 14 consecutive patients (11 with large, 3 with giant) were included. All patients were female, with an average age ± standard deviation of 59.7 ± 11.5 years. The median [interquartile range] preoperative Karnofsky Performance Status score was 80 [80-88]. The median preoperative tumor diameter and volume were 3.8 [3.2-4.2] cm and 22.2 [10.5-25.2] cm3, respectively. All patients underwent gross total resection. The median hospital stay was 2.7 [2-3] days, with all patients being discharged to home. No patients incurred any postoperative medical and/or surgical complications. Of the 9 patients who had subjective smell preoperatively, 5 stated they had subjective olfaction after surgery.

CONCLUSIONS

We demonstrate the utility of a unilateral supraorbital keyhole approach avoiding the frontal sinus for large and giant OGMs. The potential advantages of this approach are minimizing bilateral brain manipulation, avoiding the frontal sinus and potential mucoceles, and reducing the risk of cerebrospinal fluid leaks.

The Evolution of Endoscopic Endonasal Approach for Olfactory Groove Meningiomas

BACKGROUND

There is controversy over the choice of optimal approach for olfactory groove meningiomas (OGM). The endoscopic endonasal approach (EEA) is one of the most recently described corridors, which provides direct access to the tumor base.

OBJECTIVE

To detail the evolution of the endoscopic endonasal technique over the past 2 decades and demonstrate the impact of this evolution on patient outcomes.

METHODS

This is a retrospective study based on a prospectively maintained database of consecutive cases of OGM operated on at our institution via EEA. For analysis, the whole cohort has been divided into 3 equal "eras" according to the time period during which the surgery happened, creating early, middle, and contemporary groups.

RESULTS

Seventy-five patients were included, 25 in each group. The rate of postoperative cerebrospinal fluid leak significantly decreased over time (28%, 32%, and 8% in the early, middle, and contemporary groups, respectively, P = .020). The rate of postoperative encephalomalacia was significantly lower in more recent groups (24%, 16%, and 0% in the early, middle, and contemporary groups, respectively, P = .029), as was the time to resolution of postoperative brain edema (103.9 months, 87.3 months, and 16.8 months in the early, middle, and contemporary groups, respectively, P = .020).

CONCLUSION

The endoscopic endonasal approach for OGM significantly evolved over time, achieving lower cerebrospinal fluid leak rates while providing a high rate of Simpson grade 1 resection. Technical improvements minimized the frontal lobe impact. Current data support EEA as a safe and effective corridor to treat OGM.

Olfactory Groove Meningiomas: Comprehensive assessment between the different microsurgical transcranial approaches and the Endoscopic Endonasal Approaches, systematic review and metanalysis on behalf of the EANS skull base section

•OGM surgery is much more complex than a simple debate of "from above or from below" (transcranial vs endoscopic).•Lateral Sub-frontal and Superior Interhemispheric seem the most effective, superior and versatile approaches for OGM.•Minimally Invasive Transcranial approaches showed no inferiority in OGM sized <4 ​cm.•Endoscopic Endonasal Approaches showed inferior results in surgical and in functional outcomes for OGM.

Risk Factors for Postoperative Brain Contusion and Early Outcomes in Patients with Anterior Skull Base Meningiomas Undergoing Unifrontal Surgery: Single Center Experience with 110 Patients

Background

Though frontal lobe contusion is a major cause for morbidity and prolonged hospitalization following excision of anterior skull base meningiomas, there is only limited literature on this complication. This study aimed to find out the incidence of postoperative frontal lobe contusion, identify the risk factors for its development and its impact on early postoperative outcome.

Methods

Data from 110 patients who underwent excision of anterior skull base meningiomas through a unilateral supraorbital craniotomy from 2001 to 2018 were retrospectively analyzed. The risk factors analyzed for development of postoperative contusion were tumor location, size, volume, peritumoral edema, tumor consistency, extent of resection, tumor grade and type of retraction used.

Results

Simpson grade II excision was achieved in ninety-two patients (83.6%). There was no frontal lobe contusion in eighty-two patients (74.5%). Frontal lobe contusion was noted in twenty-eight patients (25.5%), but was severe in only four patients (3.6%). On multivariate analysis, fixed retractor use (OR 11.56 [1.21-110.03]; P =0.03) and WHO grade II tumor (OR 3.29 [1.11-9.77]; P =0.03) were independently associated with postoperative frontal lobe contusion. Patients with higher contusion grade had significantly longer postoperative hospitalization (P =.02) and lower KPS score at discharge (P =.01).

Conclusions

Unilateral supraorbital craniotomy and lateral subfrontal approach is an excellent procedure for excision of anterior skull base meningiomas with minimal postoperative complications related to frontal lobe retraction. Frontal lobe contusion should be avoided with the use of dynamic retraction, since postoperative contusion prolongs hospitalization and worsens the functional outcome at discharge.

Midline Skull Base Meningiomas: Transcranial and Endonasal Perspectives

Simple Summary

Skull base meningiomas have always represented a challenge for neurosurgeons. Despite their histological nature, they may be associated with unfavorable outcomes due to their deep-seated location and the surrounding neurovascular structures. Over time, several corridors have been proposed, each one carrying its own pros and cons. During the last decades, the endoscopic endonasal route has been asserted among the classic routes for a growing number of midline and paramedian lesions. Therefore, the aim of our paper is to present a comprehensive review of the indications and techniques for the management of skull base meningiomas, emphasizing the ambivalent and complementary role of the low and high routes.

Abstract

Skull base meningiomas have always represented a challenge for neurosurgeons. Despite their histological nature, they may be associated with unfavorable outcomes due to their deep-seated location and the surrounding neurovascular structures. The state of the art of skull base meningiomas accounts for both transcranial, or high, and endonasal, or low, routes. A comprehensive review of the pertinent literature was performed to address the surgical strategies and outcomes of skull base meningioma patients treated through a transcranial approach, an endoscopic endonasal approach (EEA), or both. Three databases (PubMed, Ovid Medline, and Ovid Embase) have been searched. The review of the literature provided 328 papers reporting the surgical, oncological, and clinical results of different approaches for the treatment of skull base meningiomas. The most suitable surgical corridors for olfactory groove, tuberculum sellae, clival and petroclival and cavernous sinus meningiomas have been analyzed. The EEA was proven to be associated with a lower extent of resection rates and better clinical outcomes compared with transcranial corridors, offering the possibility of achieving the so-called maximal safe resection.

Stereotactic Radiosurgery for Olfactory Groove Meningiomas: An International, Multicenter Study

BACKGROUND

Stereotactic radiosurgery (SRS) is increasingly considered for selected olfactory groove meningiomas (OGMs).

OBJECTIVE

To investigate the safety and efficacy of SRS for OGMs.

METHODS

From 20 institutions participating in the International Radiosurgery Research Foundation, we pooled patients who underwent SRS for histologically confirmed or radiologically suspected WHO grade I OGMs and were followed for 6 mo or more after the SRS.

RESULTS

In total, 278 (median age 57 yr) patients underwent SRS for histologically confirmed (29%) or radiologically suspected (71%) WHO grade I OGMs Median treatment volume was 4.60 cm3 (range: 0.12-27.3 cm3), median prescription dose was 12 Gy, and median dose to the olfactory nerve was 11.20 Gy. During median post-SRS imaging follow-up of 39 mo (range: 6-240 mo), 43% of patients had partial or marginal response, 54% of patients had stable disease, and 3% of patients experienced progression. During median post-SRS clinical follow-up of 51 mo (range: 6-240 mo), 36 (13%) patients experienced clinical and/or radiological adverse radiation events (AREs). Elevated risk of AREs was associated with larger OGM volume (P = .009) and pre-SRS peritumoral T2/fluid-attenuated inversion-recovery signal abnormalities (P < .001). After the SRS, olfaction remained stable, improved, or deteriorated in 90%, 8%, and 2% of patients, respectively. Complete post-SRS anosmia was predicted by partial/complete anosmia before the SRS (odds ratio [OR] = 83.125; 95% CI [24.589-281.01], P < .001) and prior resection of OGM (OR = 3.919; 95% CI [1.713-8.970], P = .001).

CONCLUSION

SRS is associated with durable local control of the majority of OGM patients with acceptable safety profile. SRS allows preservation or improvement of olfactory function in the majority of OGM patients.

Absence of papilledema in large intracranial tumours

Papilledema refers to optic disc edema occurring secondary to raised intracranial pressure. In patients with intracranial tumours, tumour size might be the expected predictor of whether or not papilledema will develop, however, this is not the case in clinical practice. We report a series of 5 patients with large intracranial tumours and no evidence of papilledema and discuss the potential factors which may contribute to the lack of optic disc edema in these cases. Development of papilledema depends on both the presence of elevated intracranial pressure and transmission of elevated pressure to the subarachnoid space within the optic nerve sheath and to the optic nerve itself. We discuss how intracranial tumours may influence the physiology of the surrounding tissues, cerebrospinal fluid dynamics and cerebral venous outflow and how individual anatomic variations, particularly within the optic nerve sheath and optic canal, likely play a role in development of papilledema.

The unilateral frontotemporal approach for large and giant olfactory groove meningioma: Experience with 18 consecutive patients

AIM

Although the bifrontal approach used to be recommended for large olfactory groove meningioma (OGM), recent studies showed that large OGMs can also be resected safely via unilateral approaches. The present study aimed to discuss reasons for preferring a unilateral frontotemporal approach (UFTA), and the technical nuances and results of the UFTA, based on 18 cases.

MATERIAL AND METHODS

The clinical and surgical data of patients who had been operated on for large (4-6cm) or giant (>6cm) OGM via a UFTA between 2011 and 2018 were retrospectively collected.

RESULTS

In all, 18 patients were included. All tumors were compatible with a diagnosis of OGM in the light of peri-operative examinations. 11 cases (61%) were large and 7 (39%) giant OGM; mean diameter was 6.1cm (range, 4-10cm). Resection extent was Simpson grade II in 14 cases (78%), grade III in 1 (5%), and grade IV in 3 (17%). Sixteen cases (89%) had no peri-operative complications, while 2 patients (11%) showed cerebrospinal fluid leakage and hemorrhagic deposition in the surgical area. There were no new neurological deficits nor deaths.

CONCLUSION

The UFTA for OGM is a relatively safe and effective approach, ensuring a high total removal rate with low mortality and morbidity. This study, with a reasonable number of patients, is one of the few in the literature on the outcome of this approach.

The endoscope-assisted supraorbital "keyhole" approach for anterior skull base meningiomas: an updated meta-analysis

INTRODUCTION

The gold-standard treatment for symptomatic anterior skull base meningiomas is surgical resection. The endoscope-assisted supraorbital "keyhole" approach (eSKA) is a promising technique for surgical resection of olfactory groove (OGM) and tuberculum sellae meningioma (TSM) but has yet to be compared with the microscopic transcranial (mTCA) and the expanded endoscopic endonasal approach (EEA) in the context of existing literature.

METHODS

An updated study-level meta-analysis on surgical outcomes and complications of OGM and TSM operated with the eSKA, mTCA, and EEA was conducted using random-effect models.

RESULTS

A total of 2285 articles were screened, yielding 96 studies (2191 TSM and 1510 OGM patients). In terms of effectiveness, gross total resection incidence was highest in mTCA (89.6% TSM, 91.1% OGM), followed by eSKA (85.2% TSM, 84.9% OGM) and EEA (83.9% TSM, 82.8% OGM). Additionally, the EEA group had the highest incidence of visual improvement (81.9% TSM, 54.6% OGM), followed by eSKA (65.9% TSM, 52.9% OGM) and mTCA (63.9% TSM, 45.7% OGM). However, in terms of safety, the EEA possessed the highest cerebrospinal fluid leak incidence (9.2% TSM, 14.5% OGM), compared with eSKA (2.1% TSM, 1.6% OGM) and mTCA (1.6% TSM, 6.5% OGM). Finally, mortality and intraoperative arterial injury were 1% or lower across all subgroups.

CONCLUSIONS

In the context of diverse study populations, the eSKA appeared not to be associated with increased adverse outcomes when compared with mTCA and EEA and offered comparable effectiveness. Case-selection is paramount in establishing a role for the eSKA in anterior skull base tumours.

Strategies for Optic Pathways Decompression for Extra-Axial Tumors or Intracranial Aneurysms: A Technical Note

BACKGROUND

 Different types of skull base tumors and intracranial aneurysms may lead to compression of the optic pathways. Since most of them are biologically benign conditions, the first aim of surgery is preservation of optic nerves rather than the oncologic radicality.

MATERIALS AND METHODS

 Based on the progressive technical refinements coming from our institutional experience of optic nerve compression from aneurysms and extra-axial tumors, we analyzed the surgical steps to release nerves and chiasm during tumor debulking and aneurysm clipping.

RESULTS

 We distinguished vascular and tumor lesions according to the main direction of optic nerve compression: lateral to medial, medial to lateral, inferior to superior, and anterior to posterior. We also identified four fundamental sequential maneuvers to release the optic nerve, which are (1) falciform ligament (FL) section, (2) optic canal unroofing, (3) anterior clinoid process drilling, and (4) optic strut removal. The FL section is always recommended when a gentle manipulation of the optic nerve is required. Optic canal unroofing is suggested in case of lateral-to-medial compression (i.e., clinoid meningiomas), medial-to-lateral compression (i.e., tuberculum sellae meningiomas), and inferior-to-superior compression (i.e., suprasellar lesions). Anterior clinoidectomy and optic strut removal may be necessary in case of lateral-to-medial compression from paraclinoid aneurysms or meningiomas.

CONCLUSIONS

 Preservation of the visual function is the main goal of surgery for tumors and aneurysms causing optic nerve compression. This mandatory principle guides the approach, the timing, and the technical strategy to release the optic nerve, and is principally based on the direction of the compression vector.

Meningiomas of the Planum Sphenoidale and Tuberculum Sella

Patients with meningiomas of the planum sphenoidale and tuberculum sella often present with insidious vision loss in one or both eyes as the only sign or symptom of their disease, although other sensory, oculomotor, and even endocrine abnormalities may be seen in a minority of cases. Incidentally discovered tumors also are common, as patients may undergo neuroimaging for unrelated symptoms or events. Depending on the size and orientation of the tumor, central vision loss from optic nerve compression may be a later sign, and loss of peripheral vision in one or both eyes may not be recognized until it has progressed to areas closer to fixation. A thorough neuroophthalmologic assessment including visual field testing will help to define the extent of optic pathway involvement. Both fundus examination and optical coherence tomography of the retinal nerve fiber layer and macular ganglion cell complex will aid in determining prognosis after treatment of the tumor. Orbital surgery rarely is indicated as primary therapy for meningiomas in this location, and surgical resection or debulking is usually pursued before consideration is given to radiation therapy. Because of the long-term risk of residual tumor growth or recurrence, neuroophthalmic surveillance along with serial neuroimaging is required for years after tumor resection and/or radiation therapy.

[Application of the "five-line division method" in selecting surgical approach for spaceoccupying lesions in the saddle area and the adjacent areas]

OBJECTIVE

To explore the application of the"five-line division method "in selecting the surgical approach for occupying lesions in the saddle area and its adjacent areas.

METHODS

Based on the natural anatomic structures, 5 lines (alpha, beta, theta line and lambda, epsilon line) were drawn on the images of the craniocerebral axial plane crossing the middle of the saddle area and the craniocerebral median sagittal plane, thus dividing the saddle area and its adjacent areas into 6 regions in the axial plane (1, 2, 3, 1', 2', and 3' regions) and into 4 regions in the sagittal plane (I, II, III, and IV regions). Based on these divisions, the large space-occupying lesions in the saddle area and adjacent areas were classified and their respective surgical approaches were determined after reviewing the commonly used approaches in the saddle area and clinical experiences. We collected the data of 116 patients undergoing surgeries for space-occupying lesions involving the saddle and the adjacent areas in our hospital between September, 2014 and August, 2017, and analyzed their classifications and the corresponding surgical approaches based on the "five- line division method " to compare the consistency between the hypothetic approaches and the approaches adopted in the actual surgeries.

RESULTS

The actual surgical approaches adopted in the 116 cases were all selected under the guidance of experts in our hospital. The hypothetic surgical approaches selected based on the"five- line division method "showed a good consistency with the actually adopted approaches.

CONCLUSIONS

The"five-line division method "can spatially classify the commonly seen space-occupying lesions involving the saddle area and its adjacent area to provide assistance in the selection of surgical approaches for such lesions.

Endoscopic endonasal surgery for anterior cranial fossa meningiomas

Meningiomas along the anterior skull base arise from the midline but have historically been resected via open cranial approaches with lateral to medial trajectories. The endoscopic endonasal approach (EEA) offers a direct, inferomedial approach which has demonstrated several superior qualities for their resection. These meningiomas include tuberculum sellae, planum sphenoidale, and olfactory groove meningiomas. While early gross total resection (GTR) was lower than open approaches, EEA has currently achieved comparable rates of GTR and significantly improved postoperative visual outcomes. Rate of cerebrospinal fluid (CSF) leak was one of the early complicating features preventing widespread use of EEA. However, CSF leak rates have dramatically fallen into a tolerable range with introduction of the vascularized nasoseptal flap. Olfactory groove meningiomas often present with anosmia which is persistent after endonasal approach. Rates of other complications have proven similar between EEA and open approaches and include: vascular injury, infection, morbidity, and mortality. With the appropriate team and experience, EEA for anterior skull base meningiomas is increasingly becoming the standard for resection of these lesions. However, there are certain anatomic considerations, patient features, and other aspects which may favor the open approach over EEA, and vice versa; these must be carefully and judiciously evaluated preoperatively. Overall, resection and recurrence rates are comparable, complication rates fall within a very acceptable range, and patients experience superior cosmesis and improved visual outcome with this approach.

Classification of crista galli pneumatization and clinical considerations for anterior skull base surgery

Cerebrospinal fluid (CSF) leakage caused by frontal sinus exposure is a serious complication in the basal interhemispheric approach (BIHA). Crista galli pneumatization (CGP) is often observed on preoperative computed tomography (CT) scan. The aim of this study was to classify and describe variations in anatomical measurements of CGP. We examined CT images of 300 patients with brain tumors to assess the morphology and incidence of CGP. Crista galli were classified according to their location relative to the cribriform plate and the presence of pneumatization. The paranasal sinuses were investigated as the origin of CGP. We assessed 24 patients using the BIHA for skull base tumors; these patients were included as clinical cases to assess the range of skeletonization of the crista galli and determine the route of CSF leakage in the other 276 patients. CGP was found in 28/300 CT scans, including upper, middle, and lower type CGPs. The origin of CGPs was the frontal sinus or ethmoid sinus. All CGPs were localized in the anterior half of the crista galli. In the 24 consecutive clinical cases, there were 13 tuberculum sellae meningiomas, 3 craniopharyngiomas, and 8 with other pathologies. The preoperative crista galli height was 12.3 mm and the distance from the top of the skeletonization to the cribriform plate was 5.2 mm. CGP originating from the paranasal sinuses can lead to CSF leakage. In cases where CGP originates from the ethmoid sinus, care should be taken to seal the exposed crista galli intradurally.

Resection of Olfactory Groove Meningiomas Through Unilateral vs. Bilateral Approaches: A Systematic Review and Meta-Analysis

Introduction: Consensus is limited regarding optimal transcranial approaches (TCAs) for the surgical resection of olfactory groove meningiomas (OGMs). This systematic review and meta-analysis aims to examine operative and peri-operative outcomes of unilateral compared to bilateral TCAs for OGMs. Methods: Electronic databases were searched from inception until December 2019 for studies delineating TCAs for OGM patients. Patient demographics, pre-operative symptoms, surgical outcomes, and complications were evaluated and analyzed with a meta-analysis of proportions. Results: A total of 27 observational case series comparing 554 unilateral vs. 451 bilateral TCA patients were eligible for review. The weighted pooled incidence of gross total resection is 94.6% (95% CI, 90.7-97.5%; I ² = 59.0%; p = 0.001) for unilateral and 90.9% (95% CI, 85.6-95.4%; I ² = 58.1%; p = 0.003) for bilateral cohorts. Similarly, the incidence of OGM recurrence is 2.6% (95% CI, 0.4-6.0%; I ² = 53.1%; p = 0.012) and 4.7% (95% CI, 1.4-9.2%; I ² = 55.3%; p = 0.006), respectively. Differences in oncologic outcomes were not found to be statistically significant (p = 0.21 and 0.35, respectively). Statistically significant differences in complication rates in bilateral vs. unilateral TCA cohorts include meningitis (1.0 vs. 0.0%; p = 0.022) and mortality (3.2 vs. 0.2%; p = 0.007). Conclusions: While both cohorts have similar oncologic outcomes, bilateral TCA patients exhibit higher post-operative complication rates. This may be explained by underlying tumor characteristics necessitating more radical resection but may also indicate increased morbidity with bilateral approaches. However, evidence from more controlled, comparative studies is warranted to further support these findings.

Proximal Branches of the Anterior Cerebral Artery: Anatomic Study and Applications to Endoscopic Endonasal Surgery

BACKGROUND

The endoscopic endonasal approach is a surgical alternative for midline anterior skull base tumors. A detailed understanding of the proximal anterior cerebral artery (ACA) branches' anatomy from an endonasal perspective is essential for avoiding vascular complications.

OBJECTIVE

To evaluate, from an endonasal perspective, the anatomic variations of the ACA and its proximal branches, specifically the recurrent artery of Heubner (RAH), and the fronto-orbital (FOA) and frontopolar (FPA) arteries.

METHODS

We study the origin, course, branching pattern, diameter, and relationship between the proximal ACA branches and the optic apparatus and olfactory tract in 25 head specimens.

RESULTS

The RAH was present in all hemispheres and originated within 3 ± 1.5 mm of the AcomA, with a 0.4 ± 0.1 mm diameter. Based on its relationship with the A1 segment, we observed three RAH courses: anterior (40%), superior (22%), and posterior (38%). The FOA was present in all cases, a mean of 6 ± 4 mm from the AcomA, with a 0.7 ± 0.4 mm diameter. The FOA arose mainly from the A2 (70%), with three courses in relation to the olfactory tract: crossing its proximal third (54%), crossing its middle third (31%), and running parallel to it along the gyrus rectus (15%). The FPA was present in 92% of the hemispheres, a mean of 10 ± 5 mm from the AcomA, always arising from the A2 and coursing anteriorly within the interhemispheric fissure towards the frontal pole.

CONCLUSION

The RAH, FOA, and FPA can be differentiated by origin, course, and destination using the A1 segment, olfactory tract, and interhemispheric fissure, respectively, as surgical landmarks.

Results of Transcranial Resection of Olfactory Groove Meningiomas in Relation to Imaging-Based Case Selection Criteria for the Endoscopic Approach

BACKGROUND

Endoscopic endonasal surgery (EES) is increasingly used for olfactory groove meningiomas (OGMs). The role of EES for large (≥4 cm) or complex OGMs is debated. Specific imaging features have been reported to affect the degree of gross total resection (GTR) and complications following EES for OGMs. The influence of these factors on transcranial resection (TCR) is unknown.

OBJECTIVE

To examine the impact of specific imaging features on outcome following TCR to provide a standard for large and endoscopically less favorable OGMs against which endoscopic outcomes can be compared.

METHODS

Retrospective study of patients undergoing TCR for OGMs 2002 to 2016.

RESULTS

Fifty patients (mean age 62.1 yr, mean maximum tumor diameter 5.04 cm and average tumor volume of 48.8 cm3) were studied. Simpson grade 1 and 2 resections were achieved in 80% and 12%, respectively. A favorable functional outcome (modified Rankin Scale [mRS] 0-2) was attained in 86%. The degree of resection, mRS, mortality (4%), recurrence (6%), infection (8%), and cerebrospinal fluid leak requiring intervention (12%) were not associated with tumor calcification, absence of cortical cuff, T2 hyperintensity, tumor configuration, tumor extension beyond midpoint of superior orbital roof, or extension to posterior wall of frontal sinus. There was no difference in resection rates but a trend towards greater complications between 3 arbitrarily divided groups of large meningiomas of increasing complexity based on extensive extension or vascular adherence.

CONCLUSION

Favorable outcomes can be achieved with TCR for large and complex OGMs Factors that may preclude endoscopic resection do not negatively affect outcome following TCR.

Cost-effectiveness of endoscopic endonasal vs transcranial approaches for olfactory groove meningioma

BACKGROUND

Endoscopic endonasal approaches (EEAs) have been adopted as an alternative to standard transcranial approaches for olfactory groove meningiomas (OGMs). However, the relative cost-effectiveness remains controversial.

METHODS

Cost-utility analysis from a societal perspective comparing EEA vs transcranial approaches for OGM was used in this study. Surgical treatment was modeled using decision analysis, and a Markov model was adopted over a 20-year horizon. Parameters were obtained from literature review. Costs were expressed in 2017 Canadian dollars.

RESULTS

In the base case, EEA was cost-effective compared with transcranial surgery with an incremental cost-effectiveness ratio of $33 523 ($30 475 USD)/QALY. There was a 55% likelihood that EEA was cost-effective at a willingness-to-pay of $50 000/QALY. EEA remained cost-effective at a cerebrospinal fluid leak rate below 60%, gross total resection rate above 25%, and base cost less than $66 174 ($60 158 USD).

CONCLUSION

EEA may be a cost-effective alternative to transcranial approaches for selected OGM.

Gamma Knife radiosurgery for intracranial benign meningiomas: follow-up outcome in 130 patients

OBJECTIVEThe authors retrospectively analyzed the follow-up data in 130 patients with intracranial benign meningiomas after Gamma Knife radiosurgery (GKRS), evaluated the tumor progression-free survival (PFS) rate and neurological function preservation rate, and determined the predictors by univariate and multivariate survival analysis.METHODSThis cohort of 130 patients with intracranial benign meningiomas underwent GKRS between May 2012 and May 2015 at the Second Hospital of Tianjin Medical University. The median age was 54.5 years (range 25-81 years), and women outnumbered men at a ratio of 4.65:1. All clinical and radiological data were obtained for analysis. No patient had undergone prior traditional radiotherapy or chemotherapy. The median tumor volume was 3.68 cm3 (range 0.23-45.78 cm3). A median margin dose of 12.0 Gy (range 10.0-16.0 Gy) was delivered to the tumor with a median isodose line of 50% (range 50%-60%).RESULTSDuring a median follow-up of 36.5 months (range 12-80 months), tumor volume regressed in 37 patients (28.5%), was unchanged in 86 patients (66.2%), and increased in 7 patients (5.4%). The actuarial tumor progression-free survival (PFS) rate was 98%, 94%, and 87% at 1, 3, and 5 years, respectively, after GKRS. Tumor recurred in 7 patients at a median follow-up of 32 months (range 12-56 months). Tumor volume ≥ 10 cm3 (p = 0.012, hazard ratio [HR] 8.25, 95% CI 1.60-42.65) and pre-GKRS Karnofsky Performance Scale score < 90 (p = 0.006, HR 9.31, 95% CI 1.88-46.22) were independent unfavorable predictors of PFS rate after GKRS. Of the 130 patients, 101 (77.7%) presented with one or more neurological symptoms or signs before GKRS. Neurological symptoms or signs improved in 40 (30.8%) patients, remained stable in 83 (63.8%), and deteriorated in 7 (5.4%) after GKRS. Two (1.5%) patients developed new cranial nerve (CN) deficit. Tumor volume ≥ 10 cm3 (p = 0.042, HR = 4.73, 95% CI 1.06-21.17) and pre-GKRS CN deficit (p = 0.045, HR = 4.35, 95% CI 0.84-22.48) were independent unfavorable predictors for improvement in neurological symptoms or signs. Six (4.6%) patients developed new or worsening peritumoral edema with a median follow-up of 4.5 months (range 2-7 months).CONCLUSIONSGKRS provided good local tumor control and high neurological function preservation in patients with intracranial benign meningiomas. Patients with tumor volume < 10 cm3, pre-GKRS Karnofsky Performance Scale score ≥ 90, and no pre-GKRS CN deficit (I-VIII) can benefit from stereotactic radiosurgery. It can be considered as the primary or adjuvant management of intracranial benign meningiomas.

Anatomical Variations in the Location of Veins Draining Into the Anterior Superior Sagittal Sinus: Implications for the Transbasal Approach

BACKGROUND

Many approaches are used for midline anterior cranial fossa meningioma resection. In the subfrontal approach, the anterior superior sagittal sinus (SSS) is commonly ligated to release the anterior falx. The transbasal approach allows access to the origin of the anterior SSS, allowing for maximum venous preservation.

OBJECTIVE

To investigate variations in the first and second veins draining into the SSS.

METHODS

We performed stepwise dissections for a transbasal level 1 approach on 8 anatomic specimens. We visualized the first and second veins draining into the sinus and measured the distance from the foramen cecum to these veins. We also measured the orbital bar height to determine the length of sagittal sinus that could be preserved with orbital bar removal.

RESULTS

The distance between the foramen cecum and the first vein ranged from 4 to 36 mm while the distance to the second vein ranged from 6 to 48 mm. The mean orbital bar height was 26.4 mm. Based on these measurements, with a traditional bicoronal craniotomy without orbital bar removal, 81% of first veins and 58% of second veins would be sacrificed.

CONCLUSION

A supraorbital bar or nasofrontal osteotomy, part of the transbasal skull base approach, is helpful to preserve the first and second veins when ligating the anterior SSS. Based on this study, it may be difficult to preserve these veins without orbital bar removal. Preservation of these veins may be of clinical importance when approaching midline anterior fossa pathologies.

Factors affecting serum lactate in patients with intracranial tumors - A report of our series and review of the literature

Background

A hyperlactemia may occur in the presence of tissue hypoperfusion, in diseases affecting metabolism and in cases of malignant neoplasm. However, the factors affecting the serum lactate levels in patients submitted to craniotomy for the resection of an intracranial tumor have been investigated only marginally. Here, we assessed the factors possibly affecting the levels of serum lactate in intracranial tumors and carried out a thorough literature review on this topic.

Methods

All patients submitted to elective craniotomy from January 2017 to August 2018 for the resection of a glioblastoma (GBM; 101 cases) and a benign meningioma (WHO I; 105 cases) were included in this study. The sex, age, histological diagnosis, body mass index (BMI), and diabetes were assessed as possible factors affecting the level of the preoperative and postoperative serum lactate in these patients.

Results

We found that preoperative hyperlactemia (> 2 mmol/l) was more frequent in patients with GBM than in patients with meningioma (P = 0.0003). Moreover, a strong correlation between a preoperative lactemia and postoperative lactemia (P < 0.0001) was observed. On univariate analysis, we found increased preoperative serum lactate levels in GBM patients (P = 0.0022) and in patients with a BMI ≥30 (P = 0.0068). Postoperative serum lactate levels were significantly higher in GBM patients (P = 0.0003). On multivariate logistic regression analysis, a diagnosis of GBM was an independent factor for higher level of preoperative (P = 0.0005) and postoperative (P < 0.0001) serum lactate.

Conclusion

The malignant phenotype of GBM is the strongest factor associated with a pre- and postoperative hyperlactemia in patients submitted to craniotomy for the resection of an intracranial tumor.

Indications, feasibility, safety, and efficacy of CyberKnife radiotherapy for the treatment of olfactory groove meningiomas: a single institutional retrospective series

Purpose

To assess the safety and efficacy of CyberKnife® radiotherapy (CKRT) for the treatment of olfactory groove meningiomas (OGMs).

Methods

A retrospective review was performed of 13 patients with OGM treated with CKRT from September 2005 to May 2018 at our institution. Nine patients were treated primarily with CKRT, 3 for residual disease following resection, and 1 for disease recurrence.

Results

Five patients were treated with stereotactic radiosurgery (SRS), 6 with hypofractionated stereotactic radiotherapy (HSRT), and 2 with fractionated stereotactic radiotherapy (FSRT). The median tumor volume was 8.12 cm³. The median prescribed dose was 14.8 Gy for SRS, 27.3 Gy for HSRT, and 50.2 Gy for FSRT. The median maximal dose delivered was 32.27 Gy. Median post treatment follow-up was 48 months. Twelve of 13 patients yielded a 100% regional control rate with a median tumor volume reduction of 31.7%. Six of the 12 patients had reduced tumor volumes while the other 6 had no changes. The thirteenth patient had significant radiation-induced edema requiring surgical decompression. Twelve patients were alive and neurologically stable at the time of the review. One patient died from pneumonia unrelated to his CKRT treatment.

Conclusions

CKRT appears to be safe and effective for the treatment of OGMs.

Decision-making algorithm for minimally invasive approaches to anterior skull base meningiomas

OBJECTIVE Anterior skull base meningiomas are benign lesions that cause neurological symptoms through mass effect on adjacent neurovascular structures. While traditional transcranial approaches have proven to be effective at removing these tumors, minimally invasive approaches that involve using an endoscope offer the possibility of reducing brain and nerve retraction, minimizing incision size, and speeding patient recovery; however, appropriate case selection and results in large series are lacking. METHODS The authors developed an algorithm for selecting a supraorbital keyhole minicraniotomy (SKM) for olfactory groove meningiomas or an expanded endoscopic endonasal approach (EEA) for tuberculum sella (TS) or planum sphenoidale (PS) meningiomas based on the presence or absence of olfaction and the anatomical extent of the tumor. Where neither approach is appropriate, a standard transcranial approach is utilized. The authors describe rates of gross-total resection (GTR), olfactory outcomes, and visual outcomes, as well as complications, for 7 subgroups of patients. Exceptions to the algorithm are also discussed. RESULTS The series of 57 patients harbored 57 anterior skull base meningiomas; the mean tumor volume was 14.7 ± 15.4 cm³ (range 2.2-66.1 cm³), and the mean follow-up duration was 42.2 ± 37.1 months (range 2-144 months). Of 19 patients with olfactory groove meningiomas, 10 had preserved olfaction and underwent SKM, and preservation of olfaction in was seen in 60%. Of 9 patients who presented without olfaction, 8 had cribriform plate invasion and underwent combined SKM and EEA (n = 3), bifrontal craniotomy (n = 3), or EEA (n = 2), and one patient without both olfaction and cribriform plate invasion underwent SKM. GTR was achieved in 94.7%. Of 38 TS/PS meningiomas, 36 of the lesions were treated according to the algorithm. Of these 36 meningiomas, 30 were treated by EEA and 6 by craniotomy. GTR was achieved in 97.2%, with no visual deterioration and one CSF leak that resolved by placement of a lumbar drain. Two patients with tumors that, based on the algorithm, were not amenable to an EEA underwent EEA nonetheless: one had GTR and the other had a residual tumor that was followed and removed via craniotomy 9 years later. CONCLUSIONS Utilizing a simple algorithm aimed at preserving olfaction and vision and based on maximizing use of minimally invasive approaches and selective use of transcranial approaches, the authors found that excellent outcomes can be achieved for anterior skull base meningiomas.

Transbasal versus endoscopic endonasal versus combined approaches for olfactory groove meningiomas: importance of approach selection

OBJECTIVE There has been much debate regarding the optimal surgical approach for resecting olfactory groove meningiomas (OGMs). In this paper, the authors analyzed the factors involved in approach selection and reviewed the surgical outcomes in a series of OGMs. METHODS A retrospective review of 28 consecutive OGMs from a prospective database was conducted. Each tumor was treated via one of 3 approaches: transbasal approach (n = 15), pure endoscopic endonasal approach (EEA; n = 5), and combined (endoscope-assisted) transbasal-EEA (n = 8). RESULTS The mean tumor volume was greatest in the transbasal (92.02 cm³) and combined (101.15 cm³) groups. Both groups had significant lateral dural extension over the orbits (transbasal 73.3%, p < 0.001; combined 100%), while the transbasal group had the most cerebral edema (73.3%, p < 0.001) and vascular involvement (66.7%, p < 0.001), and the least presence of a cortical cuff (33.3%, p = 0.019). All tumors in the combined group were recurrent tumors that invaded into the sinonasal cavity. The purely EEA group had the smallest mean tumor volume (33.33 cm³), all with a cortical cuff and no lateral dural extension. Gross-total resection was achieved in 80% of transbasal, 100% of EEA, and 62.5% of combined cases. Near-total resection (> 95%) was achieved in 20% of transbasal and 37.5% of combined cases, all due to tumor adherence to the critical neurovascular structures. The rate of CSF leakage was 0% in the transbasal and combined groups, and there was 1 leak in the EEA group (20%), resulting in an overall CSF leakage rate of 3.6%. Olfaction was preserved in 66.7% in the transbasal group. There was no significant difference in length of stay or 30-day readmission rate between the 3 groups. The mean modified Rankin Scale score was 0.79 after the transbasal approach, 2.0 after EEA, and 2.4 after the combined approach (p = 0.0604). The mean follow-up was 14.5 months (range 1-76 months). CONCLUSIONS The transbasal approach provided the best clinical outcomes with the lowest rate of complications for large tumors (> 40 mm) and for smaller tumors (< 40 mm) with intact olfaction. The role of EEA appears to be limited to smaller, appropriately selected tumors in which olfaction is already absent. EEA also plays an important adjunctive role when combined with the transbasal approach for recurrent OGMs invading the sinonasal cavity. Careful patient selection using an individualized, tailored strategy is important to optimize surgical outcomes.

Innovations in the Art of Microneurosurgery for Reaching Deep-Seated Cerebral Lesions

Deep-seated cerebral lesions have fascinated and frustrated countless surgical innovators since the dawn of the microneurosurgical era. To determine the optimal approach, the microneurosurgeon must take into account the characteristics and location of the pathological lesion as well as the operator's range of technical expertise. Increasingly, microneurosurgeons must select between multiple operative corridors that can provide access to the surgical target. Innovative trajectories have emerged for many indications that provide more flexible operative angles and superior exposure but result in longer working distances and more technically demanding maneuvers. In this article, we highlight 4 innovative surgical corridors and compare their strengths and weaknesses against those of more conventional approaches. Our goal is to use these examples to illustrate the following principles of microneurosurgical innovation: (1) discover more efficient and flexible exposures with superior working angles; (2) ensure maximal early protection of critical neurovascular structures; and (3) effectively handle target pathology with minimal disruption of normal tissues.

Small Extended Bifrontal Approach for Midline Anterior Skull Base Meningiomas: Our Experience with 54 Consecutive Patients

OBJECTIVE

To describe the technique of a small extended bifrontal approach and review the clinical outcome of patients with midline anterior skull base (MASB) meningiomas treated using this technique.

METHODS

The small extended bifrontal craniotomy extends inferiorly to the nasofrontal suture without entering the orbit, superiorly 3 cm above the supraorbital rim, and laterally 3 cm to the midline on both sides. A review of a prospectively acquired database was performed of 54 consecutive patients with MASB meningiomas who underwent this craniotomy.

RESULTS

Twenty-nine patients with olfactory groove meningiomas, 2 with planum sphenoidale meningiomas (PSMs), and 23 with tuberculum sellae meningiomas (TSMs) were treated using this technique. Gross total resection was achieved in all patients. Of 29 patients with olfactory groove meningiomas, 12 (41.4%) had normal olfaction at presentation and 8 had preservation of olfaction postoperatively. Of 25 patients with TSMs/PSMs, 23 (92.0%) had preoperative visual impairment, with 13 showing improved vision (56.5%), 8 unchanging (34.8%), and 2 deteriorating (8.7%) after surgery. The most common complications were anosmia and hyposmia, which occurred in 5 patients (20.0%) and 3 patients (12.0%) with TSMs/PSMs, respectively. No mortality was reported. There was no recurrence in all patients after a mean follow-up of 39.5 months (range, 16-64 months).

CONCLUSIONS

The small extended bifrontal approach is a safe and effective technique for resection of MASB meningiomas, which provides adequate surgical exposure with less approach-related morbidity. It is an excellent alternative for surgeons who favor the bifrontal approach and its extended variations.

Olfactory groove and tuberculum sellae meningioma resection by endoscopic endonasal approach versus transcranial approach: A systematic review and meta-analysis of comparative studies

Intracranial meningiomas such as olfactory groove meningioma (OGM) and tuberculum sellae meningioma (TSM) arising at the anterior skull base are amenable to surgical resection. Traditionally, this has been achieved by transcranial approaches (TCAs), however, there has been an evolution in an endoscopic endonasal approach (EEA) within recent years. The aim of this systematic review and meta-analysis was to determine if the EEA was superior to the TCA in managing these anterior skull base meningioma based on comparative studies only, and highlight the limitations of the current literature. Searches of seven electronic databases from inception to April 2018 were conducted following Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines. There were 1479 articles identified for screening. Data were extracted and analyzed using meta-analysis of proportions. A total of 10 comparative studies satisfied criteria for inclusions. Resection by the EEA resulted in significantly less likelihood of worse vision (OR, 0.318; p = 0.039) when compared to TCA in OGM. However, EEA resulted also in significantly greater likelihoods of olfactory loss in OGM (OR, 4.511; p = 0.038) and TSM (OR, 3.075; p = 0.017), and CSF leak (OR, 3.854; p = 0.013) in TSM. In terms of surgical and prognosis outcomes, there was no statistically significant trend in favor of either approach in OGM or TSM. The EEA appears to confer a different postoperative complication profile when compared to the TCA in resecting OGM vs TSM which validates previous case-series comparisons. There is a need for longer-term studies that are larger, prospective, randomized in order to fully elucidate efficacy given slow tendency for progression of meningioma in order to develop a more rigorous approach selection algorithm.

Skull base versus non-skull base meningioma surgery in the elderly

To compare outcomes after surgery for skull base meningiomas (SBMs) with non-skull base meningiomas (NSBMs) in the elderly. Overall, 128 consecutive patients ≥ 70 years of age with intracranial SBMs operated between 1990 and 2010 were compared to 193 consecutive patients ≥ 70 years of age with NSBMs operated within the same time period. Median age at surgery was 75.0 years (mean 75.7, range 70.0-92.4). Follow-up was complete with median 4.7 years (mean 5.5, range 0-19). The female-to-male ratio was 2.8 for SBMs and 1.3 for NSBMs (p < 0.005). The groups had similar preoperative KPS (median 80, range 20-100), but SBMs presented significantly more frequently with raised ICP (RR = 2.2, p < 0.005) and less frequently with seizures (RR = 0.6, p < 0.05). WHO I was significantly more frequent in SBMs (p < 0.005). Gross-total resection (GTR) was less frequent in SBMs (63 vs 82%) (RR = 2.1, p < 0.0001). SBMs were similar to NSBMs with respect to neurological outcome at 6-12 months, reoperations for hematomas, postoperative infections, and 30-day mortality. Retreatment rates and time to retreatments were also similar. There were no differences between the two groups with respect to risk of retreatment and overall survival (OS) at 5, 10, 15, and 20 years. In elderly patients with SBMs selected to surgical treatment, the risks of surgery, risk of retreatment, and OS were similar to NBSMs. Therefore, surgery for SBMs may be considered as safe as NSBMs in the elderly population.

The endoscopic endonasal approach is not superior to the microscopic transcranial approach for anterior skull base meningiomas-a meta-analysis

Object

In the past decade, the endonasal transsphenoidal approach (eTSA) has become an alternative to the microsurgical transcranial approach (mTCA) for tuberculum sellae meningiomas (TSMs) and olfactory groove meningiomas (OGMs). The aim of this meta-analysis was to evaluate which approach offered the best surgical outcomes.

Methods

A systematic review of the literature from 2004 and meta-analysis were conducted in accordance with the PRISMA guidelines. Pooled incidence was calculated for gross total resection (GTR), visual improvement, cerebrospinal fluid (CSF) leak, intraoperative arterial injury, and mortality, comparing eTSA and mTCA, with p-interaction values.

Results

Of 1684 studies, 64 case series were included in the meta-analysis. Using the fixed-effects model, the GTR rate was significantly higher among mTCA patients for OGM (eTSA: 70.9% vs. mTCA: 88.5%, p-interaction < 0.01), but not significantly higher for TSM (eTSA: 83.0% vs. mTCA: 85.8%, p-interaction = 0.34). Despite considerable heterogeneity, visual improvement was higher for eTSA than mTCA for TSM (p-interaction < 0.01), but not for OGM (p-interaction = 0.33). CSF leak was significantly higher among eTSA patients for both OGM (eTSA: 25.1% vs. mTCA: 10.5%, p-interaction < 0.01) and TSM (eTSA: 19.3%, vs. mTCA: 5.81%, p-interaction < 0.01). Intraoperative arterial injury was higher among eTSA (4.89%) than mTCA patients (1.86%) for TSM (p-interaction = 0.03), but not for OGM resection (p-interaction = 0.10). Mortality was not significantly different between eTSA and mTCA patients for both TSM (p-interaction = 0.14) and OGM resection (p-interaction = 0.88). Random-effect models yielded similar results.

Conclusion

In this meta-analysis, eTSA was not shown to be superior to mTCA for resection of both OGMs and TSMs.

Electronic supplementary material

The online version of this article (10.1007/s00701-017-3390-y) contains supplementary material, which is available to authorized users.

Limitations of the endonasal endoscopic approach in treating olfactory groove meningiomas. A systematic review

OBJECTIVE

To review current management strategies for olfactory groove meningioma (OGM)s and the recent literature comparing endoscopic endonasal (EEA) with traditional transcranial (TCA) approaches.

METHODS

A PubMed search of the recent literature (2011-2016) was performed to examine outcomes following EEA and TCA for OGM. The extent of resection, visual outcome, postoperative complications and recurrence rates were analyzed using percentages and proportions, the Fischer exact test and the Student's t-test using Graphpad PRISM 7.0Aa (San Diego, CA) software.

RESULTS

There were 444 patients in the TCA group with a mean diameter of 4.61 (±1.17) cm and 101 patients in the EEA group with a mean diameter of 3.55 (± 0.58) cm (p = 0.0589). GTR was achieved in 90.9% (404/444) in the TCA group and 70.2% (71/101) in the EEA group (p < 0.0001). Of the patients with preoperative visual disturbances, 80.7% (21/26) of patients in the EEA cohort had an improvement in vision compared to 12.83%(29/226) in the TCA group (p < 0.0001). Olfaction was lost in 61% of TCA and in 100% of EEA patients. CSF leaks and meningitis occurred in 25.7% and 4.95% of EEA patients and 6.3% and 1.12% of TCA patients, respectively (p < 0.0001; p = 0.023).

CONCLUSIONS

Our updated literature review demonstrates that despite more experience with endoscopic resection and skull base reconstruction, the literature still supports TCA over EEA with respect to the extent of resection and complications. EEA may be an option in selected cases where visual improvement is the main goal of surgery and postoperative anosmia is acceptable to the patient or in medium-sized tumors with existing preoperative anosmia. Nevertheless, based on our results, it seems more prudent at this time to use TCA for the majority of OGMs.

SMO mutation status defines a distinct and frequent molecular subgroup in olfactory groove meningiomas

Background

Meningiomas are the most common primary intracranial tumors in adults. Identification of SMO and AKT1 mutations in meningiomas has raised the hope for targeted therapies. It would be useful to know the precise frequency of these mutations in anatomical subgroups and clarify their prognostic value.

Methods

We used the Sanger sequencing technique to characterize 79 samples of olfactory groove meningiomas for SMO (L412F and W535L) and AKT1E17K mutations. We reviewed clinical data to assess the prognostic value of these mutations in this anatomical subgroup.

Results

Out of the 79 patients with olfactory groove meningiomas, we identified targetable mutations in 34 patients (43%) (22 patients [28%] with SMO mutation-L412F almost exclusively-and 12 patients [15%] with AKT1 mutation). Meningiomas in the SMO-mutant group had an overall 36% recurrence rate, significantly higher than in the AKT1-mutant group (16%) and in the "SMO and AKT1 wildtype" group (11%) (χ2 test, P = .04). All late recurrences (after 5 y) occurred in the SMO-mutant group. Among grade I meningiomas, the SMO-mutant group was identified as having a significantly poorer prognosis. World Health Organization histological grade II (P = .006) and incomplete resection (P = .001) were independently associated with shorter recurrence-free survival.

Conclusion

Molecular diagnosis of SMOL412F/W535L and AKT1E17K mutations improves prognostic evaluation in olfactory groove meningiomas and opens new therapeutic perspectives with SMO or AKT inhibitors for recurrent cases.

Phantosmia and Dysgeusia following Endoscopic Transcribriform Approaches to Olfactory Groove Meningiomas

The endoscopic, endonasal transcribriform approach (EETA) is an important technique used to directly access the anterior skull base and is increasingly being used in the management of olfactory groove meningiomas (OGMs). As this approach requires removal of the cribriform plate and olfactory epithelium en route to the tumor, patients are anosmic postoperatively. Here, we report the development of phantosmia and dysgeusia in two patients who underwent EETAs for OGMs, which has not yet been reported in the literature. We hypothesize that phantosmia and dysgeusia may result from aberrant neuronal signals or misinterpretation centrally from the remaining distal portions of the olfactory and taste pathways. Since EETAs are newer than traditional open craniotomy-based techniques, reporting these outcomes will be important to appropriately counsel patients preoperatively.

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.

Elevated E2F7 expression predicts poor prognosis in human patients with gliomas

E2F transcription factors have been studied extensively in a broad range of organisms as major regulators of cell cycle, apoptosis, and differentiation. The E2F family includes the atypical member E2F7, which has been rarely studied in gliomas. The aim of this study is to determine the expression status of E2F7 in gliomas, its relationship to clinicopathological features, and patients' outcome. The mRNA levels of E2F7 in the human brain and different grades of gliomas were analysed using datasets from the publically available Oncomine database. One of the most significant co-expression factors, CDK1, together with E2F7, was further validated by immunohistochemistry in 90 different grades of gliomas. Furthermore, univariate and multivariate analyses were performed to identify prognostic variables relative to patient and tumour characteristics and treatment modalities. E2F7 mRNA expression was found to be elevated in gliomas by Oncomine-database analysis. Immunohistochemistry showed an increase in E2F7 labelling index in high- versus low-grade gliomas (62.1±11.8% vs. 18.9±10.2%, p<0.0001). There was a positive correlation between E2F7 and CDK1 immunoreactivity (Spearman r=0.446, p=0.037). Clinicopathological evaluation suggested that E2F7 expression was associated with tumour grade (p<0.0001) and recurrence (p=0.025). In Cox multivariate analysis, pathological classification and recurrence were independent prognostic factors of gliomas, and E2F7 was significantly related to progression-free survival (p=0.011), but not overall survival (p=0.062). Our findings suggested that E2F7 might act as an independent prognostic factor of gliomas and might constitute a potential therapeutic target for this disease.

Olfactory Groove Meningiomas: Comparison of Extent of Frontal Lobe Changes After Lateral and Bifrontal Approaches

OBJECTIVE

Olfactory groove meningiomas often are behaviorally silent. Numerous surgical approaches have been described in the literature for the successful removal of these meningiomas. Lateral (pterional/frontolateral) and anterior (bifrontal/fronto-orbito-basal) approaches with their various modifications remain the 2 major corridors in resecting them. In this study, we discuss our experience in microsurgical treatment of these tumors at our institution and assess the extent of frontal lobe damage after the resection of tumor.

METHODS

We reviewed the medical records of patients who underwent surgical excision of olfactory groove meningiomas from 1990 to 2014. To measure the extent of frontal lobe damage via lateral and anterior approaches, we measured the volume of porencephalic cave in the postoperative magnetic resonance imaging by using Brainlab software. The ratio of volume of porencephalic cave to tumor was measured between 2 sides and 2 approaches.

RESULTS

Fifty-seven patients with olfactory groove meningiomas, who underwent 62 microsurgical resection procedures in 1990-2014 were included in the study (74% were more than 5 cm at presentation). Pterional and bifrontal craniotomies were the most commonly used approaches. At follow-up, the volume of porencephalic cave after lateral approach was significantly less in the side contralateral to craniotomy irrespective of tumor size. The difference between ratio of volume of porencephalic cave and initial tumor was significantly less after lateral approaches, when compared to anterior approaches.

CONCLUSIONS

Lateral approaches (pterional/frontolateral) resulted in less frontal lobe change and better olfactory preservation in comparison to anterior approaches in present series.

Endoscopic Endonasal Approach for Olfactory Groove Meningiomas: Operative Technique and Nuances

Olfactory groove meningiomas represent approximately 10% of all intracranial meningiomas. Because these tumors originate at the ventral skull base, the endonasal route provides direct access to the tumor blood supply for early devascularization and removal of the underlying hyperostotic bone at the cranial base. In carefully selected patients, these tumors can be totally removed without additional brain retraction or manipulation. In this report, we describe the surgical technique and operative nuances for removal of olfactory groove meningiomas using the endoscopic endonasal approach, and also discuss the indications, limitations, complication avoidance and management, and postoperative care.

Long-Term Results of Stereotactic Radiosurgery for Skull Base Meningiomas

BACKGROUND:

Gamma knife radiosurgery (GKRS) is well established in the management of inaccessible, recurrent, or residual benign skull base meningiomas. Most series report clinical outcome parameters and complications in the short intermediate period after radiosurgery. Reports of long-term tumor control and neurological status are still lacking.

OBJECTIVE:

To report the presentation, treatment, and long-term outcome of skull base meningiomas after GKRS.

METHODS:

From a prospectively collected institutional review board-approved database, we selected patients with a World Health Organization grade I skull base meningioma treated with a single-session GKRS and a minimum of 60 months follow-up. One hundred thirty-five patients, 54.1% males (n = 73), form the cohort. Median age was 54 years (19–80). Median tumor volume was 4.7 cm3 (0.5–23). Median margin dose was 15 Gy (7.5–36). Median follow-up was 102.5 months (60.1–235.4). Patient and tumor characteristics were assessed to determine the predictors of neurological function and tumor progression.

RESULTS:

At last follow-up, tumor volume control was achieved in 88.1% (n = 119). Post-GKRS clinical improvement or stability was reported in 61.5%. The 5-, 10-, and 15-year actuarial progression-free survival rates were 100%, 95.4%, and 68.8%, respectively. Favorable outcome (both tumor control and clinical preservation/improvement) was attained in 60.8% (n = 79). Pre-GKRS performance status (Karnofsky Performance Scale) was shown to influence tumor progression (P = .001) and post-GKRS clinical improvement/preservation (P = .003).

CONCLUSION:

GKRS offers a highly durable rate of tumor control for World Health Organization grade I skull base meningiomas, with an acceptably low incidence of neurological deficits. The Karnofsky Performance Scale at the time of radiosurgery serves as a reliable long-term predictor of overall outcome.

Resection of olfactory groove meningioma - a review of complications and prognostic factors

INTRODUCTION

High complication rates have been cited following olfactory groove meningioma (OGM) resection but data are lacking on attendant risk factors. We aimed to review the complications following OGM resection and identify prognostic factors.

METHODS

A retrospective review was performed on 34 consecutive patients who underwent primary OGM resection at a single London institution between March 2008 and February 2013. Collected data included patient comorbidities, pre-operative corticosteroid use, tumour characteristics, imaging features, operative details, extent of resection, histology, use of elective post-operative ventilation, complications, recurrence and mortality.

RESULTS

Complication rate was 39%. 58% of complications required intensive care or re-operation. Higher complication rates occurred with OGM > 40 mm diameter versus ≤ 40 mm (53 vs. 28%; p = 0.16); OGM with versus without severe perilesional oedema (59 vs. 19%; p = 0.26), more evident when corrected for tumour size; and patients receiving 1-2 days versus 3-5 days of pre-operative dexamethasone (75 vs. 19%; p = 0.016). Patients who were electively ventilated post-operatively versus those who were not had higher risk tumours but a lower complication rate (17 vs. 44%; p = 0.36) and a higher proportion making a good recovery (83 vs. 55%; p = 0.20). Complete versus incomplete resection had a higher complication rate (50 vs. 23%; p = 0.16) but no recurrence (0 vs. 25%; p = 0.07).

CONCLUSION

Risk of morbidity with OGM resection is high. Higher complication risk is associated with larger tumours and greater perilesional oedema. Pre-operative dexamethasone for 3-5 days versus shorter periods may reduce the risk of complications. We describe a characteristic pattern of perilesional oedema termed 'sabre-tooth' sign, whose presence is associated with a higher complication rate and may represent an important radiological prognostic sign. Elective post-operative ventilation for patients with high-risk tumours may reduce the risk of complications.

Unilateral Tailored Fronto-Orbital Approach for Giant Olfactory Groove Meningiomas: Technical Nuances

OBJECTIVE

Giant olfactory groove meningiomas (maximum diameter ≥6 cm) remain a surgical challenge. Historically, extensive anterior and antero-lateral approaches have been the primary approaches for removal of such large tumors with limitations and morbidity pertaining to each approach. Herein, the authors describe a minimally invasive, unilateral, tailored fronto-orbital approach for resection of these complex lesions with an emphasis on preservation of the anterior cerebral arteries and olfactory nerves.

METHODS

A 4-stage approach using neuronavigation is performed: 1) predefined corridor, 2) identification of the ipsilateral anterior cerebral artery, 3) postdefined corridor, and 4) tumor base. The details of this approach are described below in a stepwise fashion and supplemented by a sample of 3 cases utilizing this technique.

RESULTS

In the 3 representative cases in which this technique was used, gross total resection was achieved without injury to any of the adjacent neurovascular structures. Significant sellar extension can be resected through a second stage endoscopic endonasal approach.

CONCLUSION

Giant olfactory groove meningiomas (≥6 cm) can be safely and completely resected with this 4-stage, unilateral fronto-orbital technique. Furthermore, early identification and preservation of the adjacent critical neurovascular structures can be achieved. This technique avoids the inherent limitations and morbidity associated with the more classic pterional and bifrontal approaches respectively while minimizing normal tissue disruption.