Vestibular Schwannoma Research Articles

Understanding Permeability Changes in Vestibular Schwannomas as Part of the Dynamic Response to Radiosurgery Using Golden-Angle Radial Sparse Parallel Imaging: A Retrospective Study

BACKGROUND AND OBJECTIVES: Vestibular schwannomas demonstrate different responses after stereotactic radiosurgery (SRS), commonly including a transient loss of internal enhancement on postcontrast T1-weighted MRI thought to be due to an early reduction in tumor vascularity. We used dynamic contrast-enhanced based golden-angle radial sparse parallel (GRASP) MRI to characterize the vascular permeability changes underlying this phenomenon, with correlations to long-term tumor regression. METHODS: Consecutive patients with vestibular schwannoma who underwent SRS between 2017 and 2019, had a transient loss of enhancement after SRS, and had long-term longitudinal GRASP studies (6, 18, and 30 months) were included in this retrospective cohort analysis (n = 19). Using GRAVIS (https://gravis-imaging.org/gravis/), an analysis pipeline for GRASP studies, we extracted the key parameters normalized to the venous sinus from a region of interest within the tumor. RESULTS: The peak, area under the curve (AUC), and wash-in phase slope were significantly reduced at 6, 18, and 30 months after SRS (corrected P < .05), even while the internal enhancement returned in the tumors. Larger pre-SRS tumors were more likely to have a greater reduction in peak (P = .013) and AUC (P = .029) at 6 months. In a subset of patients (N = 13) with long-term follow-up, the median percentage reduction in tumor volume was 58% at a median of 62 months. These patients showed a strong correlation between peak, AUC, and wash-in phase slope changes at 6 months and tumor volume at the last follow-up. CONCLUSION: After SRS and loss of internal contrast uptake within vestibular schwannomas, a slow vascular permeability dynamic persisted, suggesting the presence of postradiation processes such as fibrosis. We show for the first time, using GRASP, a quantitative assessment of the vascular radiobiological effect.

Deciphering the causal landscape: genetic insights into sporadic vestibular schwannoma risk factors through Mendelian Randomization

BackgroundSporadic vestibular schwannoma, a benign tumor affecting the vestibulocochlear nerve, poses significant health challenges due to its impact on hearing, balance, and facial nerve function. Despite known associations with genetic mutations and environmental factors, the causality between potential risk factors and sporadic vestibular schwannoma remains underexplored.ObjectiveThis study aims to investigate the causal effects of various genetically predicted risk factors on sporadic vestibular schwannoma utilizing a Two-Sample Mendelian Randomization (MR) approach to enhance understanding of its etiology and inform prevention strategies.MethodsLeveraging data from genome-wide association studies (GWAS), we analyzed 29 risk factors across five categories: related diseases, lifestyle habits, nutritional status, learning ability, and laboratory indicators. The MR analysis employed instrumental variables (IVs) derived from single nucleotide polymorphisms (SNPs) to assess causal relationships, overcoming traditional observational study limitations.ResultsOur findings highlight significant associations between sporadic vestibular schwannoma and factors such as ovarian cancer, uterine fibroids and lifestyle habits including dietary intake and alcohol consumption. Notably, higher educational attainment and specific laboratory indicators like high-density lipoprotein (HDL) cholesterol levels were linked to altered disease risk. These results suggest a multifaceted etiology involving hormonal, cardiovascular, gastrointestinal, immune, and metabolic pathways.ConclusionThis comprehensive MR study provides novel insights into the diverse risk factors contributing to sporadic vestibular schwannoma, emphasizing the role of genetic predispositions, hormonal influences, and lifestyle choices in its development. The associations identified underscore the need for a multidisciplinary research approach and targeted public health strategies to mitigate sporadic vestibular schwannoma risk. Further research into the underlying mechanisms of these associations is crucial for developing effective interventions and improving patient outcomes.

Delayed Facial Nerve Dysfunction Following CyberKnife® Radiosurgery for Vestibular Schwannoma.

The incidence and risk factors for facial nerve dysfunction (FND) following CyberKnife® therapy for vestibular schwannoma (VS) remain poorly understood. This study investigates whether differential radiation doses to vulnerable segments of the facial nerve may be associated with FND outcomes. Patients were identified who underwent CyberKnife® radiosurgery for VS at a single institution. Basic demographics, tumor characteristics, and facial nerve function were collected. Total radiation doses to tumor, internal auditory canal (IAC), and labyrinthine segment of facial nerve (LSFN) were evaluated. Six out of 64 patients experienced FND following CyberKnife® treatment for VS (9.38%, 6/64). Patients with FND were compared to those without FND (control). Of the 64 patients, complete radiation records were obtained for 30 patients (6 FND vs. 24 control). There were no significant differences in demographic or tumor characteristics between control and FND cohorts. More severe FND (HB ≥ 4) had significantly larger tumors (3.74 vs. 1.27 cm3, p = 0.037) with directionally decreased time to FND (3.50 vs. 33.5 months, p = 0.106) than patients with HB < 4, respectively. There were directionally, nonsignificant differences between maximum radiation doses to the LSFN (2492.4 vs. 2557.0 cGy, p = 0.121) and IAC (2877.3 vs. 2895.5 cGy, p = 0.824) between the control and FND cohorts, respectively. FND may represent an underrecognized sequelae of CyberKnife® radiosurgery for VS that can occur many months following treatment. Further studies are needed to elucidate the effect of differential radiation exposure to the facial nerve with FND following treatment. 3 (Retrospective Cohort Study) Laryngoscope, 134:5080-5086, 2024.

Comparing Cochlear Implant Outcomes in 100 Patients With Sporadic Vestibular Schwannoma Managed With Observation, Radiosurgery, or Microsurgery: A Multi-Institutional Review.

To compare cochlear implant (CI) speech perception outcomes in patients with sporadic vestibular schwannoma (VS) managed with observation, radiosurgery, or microsurgery. Retrospective review. Eleven tertiary academic medical centers. One hundred patients with sporadic VS who received an ipsilateral CI. Ipsilateral cochlear implantation. Pure-tone thresholds, monosyllabic speech perception testing scores, and rates of open-set speech acquisition. Of the 100 patients studied, 54 underwent microsurgery, 26 underwent radiosurgery, 19 continued observation, and 1 underwent multimodal therapy. Among all patients, the median post-implantation pure-tone average was 31 dB (interquartile range [IQR] 25-39 dB) and the median monosyllabic speech perception score was 30% (IQR 0-60%) at a median of 12 months (IQR 5-25 months) post-implantation. Patients who were managed with microsurgery (median speech perception score 11%, IQR 0-52%) exhibited poorer implant outcomes overall compared with those managed with observation (median speech perception score 52%, IQR 40-72%) or radiosurgery (median speech perception score 30%, IQR 16-60%). Open-set speech perception was achieved in 61% of patients managed with microsurgery, 100% with observation, and 80% with radiosurgery. In a multivariable setting, those managed with observation (p = 0.02) or who underwent radiosurgery (p = 0.04) were significantly more likely to achieve open-set speech perception compared with patients who underwent microsurgery. Cochlear implants offer benefit in selected patients with sporadic VS. Although achieved in over half of people after microsurgery, open-set speech perception is more reliably attained in patients who are treated with observation or radiosurgery compared with microsurgical resection. These data may inform patient counseling and VS tumor management in people who may benefit from implantation.

A Scoping Review on Vestibulopathy After Microsurgical Resection of Vestibular Schwannoma—The Forgotten Symptom

BACKGROUND AND OBJECTIVES: Although half of patients with vestibular schwannoma (VS) experience some form of vestibular dysfunction, it is rarely the most prominent symptom. The effect of VS resection on preexisting vestibulopathy remains poorly understood. Our objective was to perform a scoping review to elucidate the incidence and role of postoperative vestibulopathy after microsurgery (MS) as it relates to long-term quality of life (QOL) and predictors of recovery and to identify optimal management of vestibulopathy as a presenting symptom. METHODS: Studies were identified using the PubMed database published in the English language peer-reviewed recent literature (2000-2023) using MeSH and tiab terms, and additional studies identified from a secondary review of reference lists. RESULTS: Thirty-one articles were selected and reviewed. The literature quotes a wide range for the incidence of postoperative vestibulopathy after MS (4%-100%). Persistent vertigo universally demonstrates a strong negative effect on long-term QOL. Potential predictors of poor vestibular compensation include sex, advanced age, and tumor size. Few studies examine postoperative vertigo compared with preoperative baseline. Studies are inconsistent and variable in their use of measurement tools to assess vestibulopathy and QOL. Improvement in baseline vestibulopathy can be seen in long-term post-MS, particularly in patients with severe or disabling vertigo, although outcomes relative to other treatment modalities are otherwise similar. CONCLUSION: Further understanding of predictors and comparative management strategies for vestibulopathy would be valuable in addressing an important negative influence on QOL in patients with VS. Prospective studies factoring preoperative baseline and using standardized measurement tools are needed.

Comparative analysis of audiovestibular testing results in vestibular schwannomas

Objective:This study aimed to analyze the results of auditory and vestibular function tests in patients with unilateral vestibular schwannoma and explore their association with tumor size. Methods:Clinical data from 81 patients diagnosed with unilateral vestibular schwannoma who underwent pure-tone audiometry（PTA）, cervical and ocular vestibular evoked myogenic potentials（c/oVEMP）, as well as video head impulse test（vHIT）, and subsequently underwent surgical treatment, were retrospectively analyzed. Patients were categorized into groups based on tumor size: small （≤ 15 mm）, medium（16-30 mm）, and large （>30 mm）, determined by the maximum tumor diameter on contrast-enhanced MRI scans. Results:PTA results indicated hearing loss in 73 cases（90.1%）; vestibular function tests revealed abnormal rates for the anterior semicircular canal, horizontal semicircular canal, posterior semicircular canal, utricle, and saccule at 29.6%, 77.8%, 54.3%, 90.1%, and 92.6%, respectively. Statistically, no significant differences were found in preoperative hearing test results among patients in different groups（F=0.393, P=0.676）. However, significant differences were observed in horizontal semicircular canal gain（r=-0.248, P=0.025）, abnormal rates of horizontal semicircular canal catch-up saccades（r=0.507, P<0.001）, as well as cVEMP（χ²=15.111, P=0.004） and oVEMP thresholds（χ²=18.948, P<0.001） across varying tumor size groups. Conclusion:The extent of hearing loss in patients with vestibular schwannoma is not correlated with tumor size, whereas the degree of vestibular dysfunction demonstrates a correlation with tumor size.

Medially Migrating Vestibular Schwannomas: A Review of 10 Cases.

To analyze cases of medial migration of vestibular schwannomas to propose an underlying mechanism. Retrospective chart review. Ten patients from one institution with sporadic vestibular schwannomas that demonstrated medial migration toward the cerebellopontine angle on serial imaging were reviewed. Among the 10 patients studied, 8 patients underwent stereotactic radiosurgery and 2 were managed with wait-and-scan. All serial imaging was analyzed throughout follow-up. Volumetric and linear measurements were used to assess vestibular schwannoma growth. The fundal fluid cap length was measured from the most lateral end of the neoplasm within the internal auditory canal to the medial end of the cochlea. Pure tone averages of 0.5, 1, 2, and 3 kHz, word recognition scores, and AAO-HNS hearing class were used to assess levels of hearing loss per patient. Tumor growth exhibited a positive correlation with medial migration. Of the 10 patients studied, 9 exhibited tumor volume growth from initial to most recent imaging. Median changes in tumor volumes and fundal fluid cap lengths from initial diagnosis to the most recent imaging regardless of intervention were 130 mm3 (range 1,400-2,970) and 2.8 mm (range 1.8-6.0), respectively. Migration was noted in 4 patients prior to any intervention, in 4 patients postradiosurgery, and in 2 patients before and after radiosurgery. Therefore, half of the tumors studied migrated before an intervention and half migrated postradiosurgery. No correlation of migration and hearing decline was observed. Medial migration of vestibular schwannoma is associated with an increase in tumor volume, supporting a "tumor squeeze" mechanism within a conical internal auditory canal toward the wider porus acusticus and cerebellopontine angle.

Endolymphatic sac and duct as an anatomical repair to achieve complete exposure of the internal auditory canal through the retrosigmoid approach: Anatomical study.

The retrosigmoid approach (RSA) is used in a wide variety of pathologies in the cerebellopontine angle (CPA), especially according to the findings, it can preserve hearing function during the resection of vestibular schwannomas (VS). Complete exposure of the fundus of the internal auditory canal (IAC) could jeopardize the integrity of the otic capsule and subsequently cause profound hearing loss and chronic disabling vertigo. Great variability has been described in labyrinthine structures and to date there is no clear data on the distances of these structures to safely expose the IAC fundus. ObjectiveEstablish reference values of the endolymphatic sac and duct to achieve safe and complete exposure of the IAC through the RSA. MethodologyThis is a cross-sectional descriptive study where complete dissection of the endolymphatic sac and duct (ELSD) was performed on 20 preserved human temporal bones, measuring the distances of nine anatomical structures underlying or closely related to the ELSD. ResultsWhen evaluating the variability between the structures, the distance between the ELSD to the acoustic pore (AP) had little variability and remained constant in all specimens. The distance between the AP and the common cross (CC) presented in our study had the lowest coefficient of variation. The distance that had the greatest variability was the measurement of the jugular foramen (JF) both by retrosigmoid and translabyrinthine approaches (RSA-TLA). The rest of the variables remained stable. ConclusionsThe ELSD is a safe anatomical technique for dissection and exposure of the IAC during RSA in VS surgeries. In our study, the structures evaluated present little variability with the exception of the distances between the ELSD and the JF, which in some cases the JF exceeds the lower limit of the ELSD and IAC.

Management of treatment-naïve Koos grade IV vestibular schwannomas using hypofractionated Gamma Knife radiosurgery: a retrospective single-institution study.

While single-fraction Gamma Knife radiosurgery (GKRS) has shown efficacy in managing vestibular schwannomas (VSs), some concerns have been raised regarding its safety profile, particularly in the context of hearing preservation. Hypofractionation has emerged as a promising approach to improving the safety profile. This retrospective, single-institution study evaluated patient outcomes following hypofractionated GKRS (hf-GKRS) for treatment-naïve Koos grade IV VSs. This study involved all patients with treatment-naïve Koos grade IV VSs who underwent hf-GKRS (3 or 5 fractions) between January 2018 and June 2021, with a follow-up period of ≥ 36 months. The outcomes assessed included local control (LC), the preservation of serviceable hearing as determined by the Gardner-Robertson hearing scale, and procedure-related adverse events. Twenty-nine patients (14 females, median age 49 years) were treated with three different dose regimens: 21 patients received 18Gy in 3 fractions, 6 patients received 20Gy in 5 fractions, and 2 patients received 25Gy in 5 fractions. Prior to treatment, 13 patients (44.8%) had serviceable hearing, one (3.4%) presented with facial palsy, and four (13.8%) had trigeminal nerve dysfunction. The median tumor volume was 10.8 cm3. During a median radiological follow-up period of 60 months (range, 36-78 months), LC was achieved in all patients. All 13 patients retained serviceable hearing at the last follow-up. Trigeminal nerve dysfunction occurred in one patient (3.4%), while another patient (3.4%) needed a ventriculoperitoneal shunt insertion due to new-onset hydrocephalus. No new-onset facial palsy was observed. hf-GKRS shows promise as an effective and safe primary or adjuvant treatment for Koos grade IV VSs with non-life-threatening or debilitating symptoms. Future studies with larger cohorts and extended follow-up periods are needed to validate these findings and to refine fractionation schemes.

Risk Analysis of Radiosurgery for Vestibular Schwannoma: Systematic Review and Comparative Study of 10-Year Outcomes

Abstract Background Determine the benefit of stereotactic radiosurgery (SRS) compared to no treatment for sporadic vestibular schwannoma (VS) by calculating epidemiologic risk using 10-year data; apply the analysis to VS that have demonstrated linear growth. Methods PubMed, Google Scholar, Web of Science, and Cochrane Library are systematically reviewed for VS tumor control 10 years after SRS and compared to an historical cohort of untreated VS (primary risk analysis). Subgroups of VS limited by size and observed growth are compared to the untreated cohort (secondary analysis). Results Twenty-four studies of 4,079 SRS-treated VS exhibited tumor control in 90.93% (87.0%-100%; SD 4.1%), while 1959 untreated VS exhibited control in 65.24%. SRS reduces the absolute risk (ARR) of tumor progression by 25.7% compared to no treatment. The number needed to treat (NNT) is 4 (3.892, 95% CI: 3.619 to 4.210). Subgroup analyses of (1) VS with definite linear growth before SRS result in similar ARR 29.4% and NNT 4 (3.395, 95% CI: 2.966-3.968), and (2) Koos 1 VS result in lower ARR 18.31% and higher NNT 6 (5.209; 95% CI: 4.018 - 7.401). Conclusions This “best-available” case-control study of 10-year data reveals that ARR and NNT are similar for VS with and without definite pre-treatment linear growth. These comparisons may be applied to CPA diameters less than 2 cm. Results for Koos 1 tumors are different. This analysis quantifies the therapeutic benefit of SRS by comparative risk analysis. The level of evidence on this topic is low.

A four-hit mechanism is sufficient for meningioma development.

Meningiomas are central nervous system tumors whose incidence increases with age. Benign meningioma pathogenesis involves germline or somatic mutation of target genes, such as NF2, leading to clonal expansion. We used an established cancer epidemiology model to investigate the number of rate-limiting steps sufficient for benign meningioma development. Incidence data was obtained from the Surveillance, Epidemiology and End Results Program (SEER) for nonmalignant meningioma from 2004 to 2020. Age-adjusted incidence rates per 100,000 person-years were divided into 5-year bands. This was repeated for vestibular schwannomas as a negative control. The Armitage-Doll methodology was applied. Mathematical solutions correcting for volatile tumor microenvironments were applied to fit higher-order models using polynomial regression when appropriate. A 75:25 training:test split was utilized for validation. 222,509 cases of benign meningiomas were identified. We noted strong linear relationships between log-transformed incidence and age across the cohort and multiple subpopulations: male, white, black, Hispanic, Asian/Pacific Islander, and American Indian subpopulations all demonstrated R2 = 0.99. Slopes were between 3.1 and 3.4, suggesting a four-step process for benign meningioma development. Female patients exhibited nonlinear deviations, but the corrected model demonstrated R2 = 0.99 with a four-hit pathway. This model performed robustly on test data with R2 = 0.99. Vestibular schwannomas demonstrated a slope of 2.1 with R2 = 0.99, suggesting a separate three-step process. Four mutations are uniquely required for the development of benign meningiomas. Correcting for volatile tumor microenvironments reliably accounted for nonlinear deviations in behavior. Further studies are warranted to elucidate genomic findings suggestive of key mutations in this pathway.

Dynamic contrast-enhanced and diffusion-weighted MR imaging for predicting tumor growth of sporadic vestibular schwannomas: a prospective study.

Advanced MR imaging, such as diffusion-weighted (DWI) and dynamic contrast-enhanced (DCE) imaging, may provide valuable non-invasive information on intrinsic tumor biology. This study aims to evaluate apparent diffusion coefficient (ADC) and DCE-MRI-derived microvascular parameter values (Ktrans, ve, and vp) as potential imaging predictors for future sporadic vestibular schwannoma (VS) growth. In this prospective cohort study, patients with newly diagnosed unilateral sporadic VS and an initial wait-and-scan strategy were enrolled between January 2021 and January 2023. Patients underwent a single timepoint comprehensive MRI protocol, including DWI and DCE-MRI sequences. The estimated values of ADC, Ktrans, ve, and vp were calculated using established pipelines on a voxelwise basis within the delineated tumor region of interest. Associations of the estimated parameter values with volumetric growth were evaluated in uni- and multivariable logistic regression and survival analyses. Of the 110 analyzed patients, 70 (64%) exhibited growth during follow-up. A significant correlation was primarily observed between the DCE-MRI-derived parameters and VS growth. The combination of mean Ktrans (P<0.001) and ve (P<0.001) tumor values provided an internally validated model with an AUC of 0.85 for growth, yielding a sensitivity of 89% and specificity of 73% at the optimized cutoff value. Only the mean ADC values were found to be significantly higher in shrinking tumors (P=0.04). The strongly significant correlation observed between VS growth and Ktrans and ve tumor values indicates great potential of the non-invasive DCE-MRI for individualized VS management in clinical practice. External validation is needed to further substantiate these findings.

Analgesia After Vestibular Schwannoma Surgery in Europe—Potential for Reduction of Postoperative Opioid Usage

Analgesia After Vestibular Schwannoma Surgery in Europe—Potential for Reduction of Postoperative Opioid Usage

Intraoperative Electrical Stapedius Reflex Testing to Monitor Cochlear Nerve Integrity during Simultaneous Vestibular Schwannoma Resection and Cochlear Implantation

Intraoperative Electrical Stapedius Reflex Testing to Monitor Cochlear Nerve Integrity during Simultaneous Vestibular Schwannoma Resection and Cochlear Implantation

NEW TECHNOLOGIES AVAILABLE FOR MICRONEUROSURGICAL REMOVAL OF ACOUSTIC NEUROMAS

Introduction The aim of this study was to analyze the results of microsurgery removal of acoustic neuromas (AN) using new technologies: flexible hand-held laser fiber, Sonopet Ultrasound Aspirator, Facial Nerve “detector” monopolar stimulation (for localize position and course of facial nerve), BAER’s with level specific (LS) CE-Chirp stimulus for hearing preservation, endoscope for IAC final check, and injectable bone substitute for closure. We report a retrospective nonrandomized clinical study on 300 cases consecutively operated on. Material and Methods From July, 2010 to December, 2023, 350 consecutive patients suffering from AN have been operated on with microneurosurgical technique by key-hole retrosigmoid approach. In majority of cases tumor resection was performed with the aid of a handheld flexible laser fiber. In the same period, Sonopet Ultrasound aspirator was used for tumor debulking and/or opening of the internal auditory meatus and canal. From May 2015, hearing preservation by means LS CE-Chirp BAER was attempted in patients with preoperative socially useful hearing (AAO-HNS class A and B). In addition, we check the removal of tumor inside the internal auditory canal (IAC) by using the flexible and/or rigid endoscope, for completing tumor removal near the fundus. Results Overall time from incision to skin suture changed in relation to size of tumor (from 165 to 575 minutes) and was not affected by the use of hand-held laser. Facial nerve function was clinically assessed with the House-Brackmann (HB) scale preoperatively, in the early postoperative period (after 1 week), and at 6-month follow-up. In 3 cases a preoperative facial nerve palsy was observed (HB III and HB IV, respectively). In the remaining cases, 6 months after surgery facial nerve preservation rate (HB I) was 92%, Hearing preservation rate (AAO-HNS A and B, pre- and postoperatively) was 52% in eligible cases. Total and “nearly total” removal of tumor was possible in about 80% of cases. Dura closure was performed with underlaying autologous pericranium. Injectable bone substitute in the gaps after bone flap repositioning minimized postoperative CSF leakage and improved the aesthetic result. Conclusions The use of new technologies (handheld flexible laser fibers, Sonopet Ultrasound Aspirator, fluoreceine, Nimbus facial nerve continuous monitoring, LS CE-Chirp BAER, endoscope for IAC final check) in AN microsurgery seems to be safe and efficacious and facilitates tumor resection, especially in ‘‘difficult’’ conditions (e.g., large size, highly vascularized, or hard tumors). The good functional outcome following conventional microsurgery seems to be further improved and the extent of tumor removal could be increased with the proper use of the new technologies available in the neurosurgical armamentarium.

TIPS AND TRICKS IN SURGICAL TREATMENT OF LARGE VESTIBULAR SCHWANNOMAS

Vestibular schwannomas (VS) frequently referred to as acoustic neuromas are the most common tumours of the cerebellopontine angle. They are benign, generally slow-growing tumors that arise from the vestibular portion of the eighth cranial nerve. For patients with large vestibular schwannomas or those exhibiting symptoms from the tumor’s mass effect, surgical intervention remains the preferred treatment approach. This paper discusses the surgical management of patients with large vestibular schwannomas operated in our department and emphasizes the use of intraoperative monitoring for preserving facial nerve function. We review the key surgical steps and highlight the importance of preoperative planning, patient position, and the use of microsurgical techniques to optimize the surgical outcome. Gross total resection of large vestibular schwannomas is associated with worse facial nerve outcomes. Our preferred treatment strategy, especially for older patients, is planned subtotal resection followed by periodic imaging evaluation and radiotherapy in cases of documented tumor growth. This approach may lead to superior facial nerve preservation and improved quality of life for individuals with large vestibular schwannomas. Conclusion The optimal treatment approach for vestibular schwannoma remains a subject of debate. Gross total resection has traditionally been the gold standard for large tumors, but this is often accompanied by a higher risk of postoperative facial nerve dysfunction. Planned subtotal resection with the goal of preserving facial nerve function, followed by closed observation is an alternative approach.

NOT THE USUAL SUSPECTS: GLIOBLASTOMA OF THE CEREBELLOPONTINE ANGLE MASQUERADING AS A VESTIBULAR SCHWANNOMA

Introduction Most tumoral processes involving the cerebellopontine angle (CPA) are extraneuraxial and usually comprise of vestibular schwannomas and meningiomas, followed by less common lesions such as epidermoid cysts, metastases and arachnoid cysts. Glioblastomas located in the CPA are rarely diagnosed. Uncommonly, intraneuraxial tumors in the CPA may grow in an exophytic manner compressing the surrounding cranial nerves, resembling the clinical picture of a more common extraneuraxial tumour. Clinical Case A 47 year old male presented to our department accusing gait imbalance, vertigo, vomiting and nausea, symptoms that started 2 months prior to admission. Upon neurological examination, the patient additionally presented right facial paresis and hypoesthesia, right sided hypoacusis, hypogeusia and diplopia. A contrast enhanced cerebral MRI revealed a right cerebellopontine angle mass with inhomogenous contrast enhancement, relatively well delineated, exerting mass effect on the cerebellum and pons with reduced perilesional edema but with involvement of the internal acoustic meatus. The indication for surgical removal of the tumour was made. The patient was placed in sitting position and a right retrosigmoid approach was performed using the operating microscope. Upon retraction of the cerebellar hemisphere, a greyish, highly vascularized and soft lesion was seen, exhibiting a spread growth, engulfing the V, VII and VIII nerves, without infiltrating them, resembling anything but a schwannoma. A frozen section of the tumour revealed a surprising result: high grade glioma. The surgical excision continued in a piece-meal fashion, using the ultrasonic aspirator with preservation of the cranial nerves until an almost complete removal was achieved. The immediate postop evolution of the patient was favourable. Nevertheless, the final histopathological diagnosis confirmed a grade IV glioblastoma. Oncological treatmend followed, but the tumour relapsed in 2 months after surgery, the control MRI revealing a multilocular tumoral dissemination in the cerebellum and brainstem which was surgically unsalvageable. Conclusion Glioblastoma of the CPA, manifesting both imagistically and clinically as a vestibular schwannoma is a rare entity but nevertheless extant, that dramatically changes the prognosis and postop evolution of a patient. Physicians involved in the diagnosis and treatment of such tumours must always be suspicious of the usual suspects in the CPA.

RARE TUMORS OF POSTERIOR CRANIAL FOSSA IN ADULTS

Objectives Tumors arising in the posterior cranial fossa pertain to a special category of neoplasm in the manner that they can cause cerebellar syndrome, obstructive hydrocephalus, brainstem compression – cranial nerve dysfunction – and herniation. In the cerebellopontine angle, the most common tumors are acoustic neuromas followed by meningiomas. Among the petroclival tumors, the most common benign tumors are meningiomas and the most common malign tumors are chordomas and metastases. Among jugular foramen tumors, the common tumors are schwannomas, paragangliomas and meningiomas. We report our unit’s experience with the neurosurgical management of rare posterior cranial fossa tumors as compared to the main literature results, taking into consideration the clinical, radiological aspects and the outcome. Materials and Methods Retrospective analysis of a single unit cohort of patients diagnosed with rare posterior cranial fossa tumors, who underwent surgical treatment in the Neurosurgery I Department of the University Emergency Hospital Bucharest between 2017 and 2024. Relevant literature review was analyzed, as well as serial clinical examinations, imaging studies, and operative records were taken into consideration. Conclusions Depending on the location, size, and pathology of the posterior cranial fossa tumors, there are different treatment options, which include microsurgical resection, observation, stereotactic radiotherapy. These type of lesions still represent a challenge and require electing the most suitable approach whilst preserving the neurologic function of the patient.

Target-aware cross-modality unsupervised domain adaptation for vestibular schwannoma and cochlea segmentation

There is growing interest in research on segmentation for the vestibular schwannoma (VS) and cochlea using high-resolution T2 (hrT2) imaging over contrast-enhanced T1 (ceT1) imaging due to the contrast agent side effects. However, the hrT2 imaging remains a problem of insufficient annotated data, which is fatal for building more robust segmentation models. To address the issue, recent studies have adopted unsupervised domain adaptation approaches that translate ceT1 images to hrT2 images. However, previous studies did not consider the size and visual characteristics of the target objects, such as VS and cochlea, during image translation. Specifically, those works simply performed normalization on the entire image without considering its significant impact on the quality of the translated images. These approaches tend to erase the small target objects, making it difficult to preserve the structure of these objects when generating pseudo-target images. Furthermore, they may also struggle to accurately reflect the unique style of the target objects within the images. Therefore, we propose a target-aware unsupervised domain adaptation framework, designed for translating target objects, each tailored to their unique visual characteristics and size using target-aware normalization. We demonstrate the superiority of the proposed framework on a publicly available challenge dataset. Codes are available at https://github.com/Bokyeong-Kang/TANQ.

Pneumatization pattern of the temporal bone with volumetric assessment and its impact on the frequency of cerebrospinal fluid leak in patients undergoing vestibular schwannoma surgery via the retrosigmoid approach.

Vestibular schwannomas are benign tumors that account for 8% of all intracranial tumors. Due to their location in the cerebellopontine angle and internal auditory canal, access to these lesions requires disruption of the temporal bone. The pneumatization of this bone varies between individuals, and literature reports suggest that it may influence the frequency of cerebrospinal fluid leaks. In our study, we assessed whether the pneumatization of the temporal bone differs in individuals with or without cerebrospinal fluid leak. We conducted a retrospective analysis that initially included 143 individuals, of whom 103 were ultimately qualified for the study. We analyzed the clinical data of the patients and the radiological characteristics of the pneumatization of the temporal bone using volumetric methods, additionally relying on classifications of temporal bone pneumatization. Pneumatization of the temporal bone in patients operated on for vestibular schwannoma with cerebrospinal fluid leakage was significantly higher compared to the group without leakage (Right: 11.15 [IQR 8.93-12.83] vs. 13.25 [IQR 10.15-15.53]; p = 0.040; Left: 10.95 [IQR 9.5-12.26] vs. 14.4 [IQR 13.03-15.7]; p = 0.012). Additionally, a higher degree of pneumatization of the petrous apex was significantly more frequent in the group with cerebrospinal fluid leak in both left (p < 0.001) and right (p < 0.001) side. The analyzed data suggest that greater pneumatization of the temporal bone and a higher degree of petrous apex pneumatization in the classification of temporal bone pneumatization may be associated with an increased risk of cerebrospinal fluid leak. To draw causal inferences, prospective studies in this area are necessary.