Intratumoral hemorrhage and fibrosis in vestibular schwannoma: a possible mechanism for hearing loss

The genetic landscape and possible therapeutics of neurofibromatosis type 2

Neurofibromatosis type 2 (NF2) is a genetic condition marked by the development of multiple benign tumors in the nervous system. The most common tumors associated with NF2 are bilateral vestibular schwannoma, meningioma, and ependymoma. The clinical manifestations of NF2 depend on the site of involvement. Vestibular schwannoma can present with hearing loss, dizziness, and tinnitus, while spinal tumor leads to debilitating pain, muscle weakness, or paresthesias. Clinical diagnosis of NF2 is based on the Manchester criteria, which have been updated in the last decade. NF2 is caused by loss-of-function mutations in the NF2 gene on chromosome 22, leading the merlin protein to malfunction. Over half of NF2 patients have de novo mutations, and half of this group are mosaic. NF2 can be managed by surgery, stereotactic radiosurgery, monoclonal antibody bevacizumab, and close observation. However, the nature of multiple tumors and the necessity of multiple surgeries over the lifetime, inoperable tumors like meningiomatosis with infiltration of the sinus or in the area of the lower cranial nerves, the complications caused by the operation, the malignancies induced by radiotherapy, and inefficiency of cytotoxic chemotherapy due to the benign nature of NF-related tumors have led a march toward exploring targeted therapies. Recent advances in genetics and molecular biology have allowed identifying and targeting of underlying pathways in the pathogenesis of NF2. In this review, we explain the clinicopathological characteristics of NF2, its genetic and molecular background, and the current knowledge and challenges of implementing genetics to develop efficient therapies.

Intratumoral hemorrhage in vestibular schwannomas after stereotactic radiosurgery

OBJECTIVE

Vestibular schwannomas (VSs) are benign tumors of the cerebellopontine angle that are typically managed with stereotactic radiosurgery (SRS). Intratumoral hemorrhage (ITH) of VSs is a rare occurrence that results in worsening vestibular and new cranial nerve deficits. Few reports have described the management and outcomes of this entity after SRS. To further delineate the incidence and impact of this event, the authors performed a retrospective review of their VS SRS patients at a single center.

METHODS

Between 1987 and 2022, 2058 patients with VSs underwent Gamma Knife radiosurgery (GKRS) at the University of Pittsburgh Medical Center. The authors performed a review of the prospectively maintained VS database at their center to identify patients with ITH. The presentation, management, and clinical and imaging outcomes of the patients are reported.

RESULTS

A total of 1902 VS patients had sufficient clinical and imaging follow-up data. Five Koos grade III (n = 1) and IV (n = 4) VS patients developed ITH after GKRS, resulting in a cumulative incidence rate of 0.26%. The age at presentation ranged from 62 to 79 years, and 3 patients were male. The time from VS diagnosis to GKRS ranged from 1 to 13 months, and the time from GKRS to ITH ranged from 2 to 130 months. Three patients had bleeding risk factors. One patient required urgent surgical intervention due to the ITH volume, while the other 4 patients were initially observed. Three patients remained stable and required no delayed intervention; 1 patient required delayed resection because of symptom progression and hemorrhagic expansion. Histopathological analysis revealed multiple fragments of S-100-positive cells, hemorrhage, and hemosiderin-laden macrophages. At last follow-up, 4 patients had clinically improved and 1 patient remained stable.

CONCLUSIONS

ITH after VS radiosurgery is a rare phenomenon with a cumulative incidence rate of 0.26% in this series. Patient-tailored management in the form of observation or resection is based on patient presentation, acuity, and ITH size.

Peliminary exploration on the differential diagnosis between meningioma and schwannoma using contrast-enhanced T1WI flow-sensitive black-blood sequence

Introduction

Contrast-enhanced T₁WI flow-sensitive black-blood (CE-T1WI FSBB) is a newly developed sequence which had not been widely used for differential diagnosis of brain tumors.

Methods

To quantify the pre-operative imaging features of intratumoral microbleeds and intratumoral vessels using CE-T₁WI FSBB scan and study the differences in biological behavior of meningiomas and schwannomas underlying the imaging features. Seventy-three cases of meningiomas and 24 cases of schwannomas confirmed by postoperative pathology were included. Two neuroradiologists independently counted intratumoral vessels and intratumoral microbleeds based on CE-T₁WI FSBB images. The vessel density index (VDI) and microbleed density index (MDI) were the number of intratumoral vessels and the number of intratumoral microbleeds divided by the tumor volume, respectively. The consistency test of intratumoral vessel count and intratumoral microbleed count based on CE-T₁WI FSBB were summarized using 2-way random intraclass correlation coefficients (ICC). Mann-Whitney U-test and chi-square test were used to determine significant differences between meningiomas and schwannomas, and fibrous meningiomas and epithelial meningiomas. P<0.05 was considered statistically significant.

Results

The ICC of intratumoral vessels count and intratumoral microbleeds count were 0.89 and 0.99, respectively. There were significant differences in the number of intratumoral microbleeds (P<0.01) and MDI values (P<0.01) between meningiomas and schwannomas. There were no differences in the number of intratumoral vessels (P=0.64), VDI (P=0.17), or tumor volume (P=0.33). There were also differences in the number of intratumoral microbleeds (P<0.01), the MDI value (P<0.01), and the sex of patients (P<0.05) between fibrous meningiomas and epithelial meningiomas.

Discussion

CE-T₁WI FSBB can be a new technique for differentiating schwannomas from meningiomas, and even different types of meningiomas. Schwannomas have a higher incidence of intratumoral hemorrhage, more intratumoral microbleeds, and higher MDI values than meningiomas, which provides a new basis for preoperative differential diagnosis and treatment decisions.

Progression of Hearing Loss in Observed Non-Growing Vestibular Schwannoma

OBJECTIVE

To assess hearing outcomes in observed vestibular schwannoma (VS) with focus on non-growing tumors.

STUDY DESIGN

Retrospective review.

SETTING

Two tertiary neurotology centers.

PATIENTS AND INTERVENTIONS

Patients with sporadic VS undergoing at least 3 years' observation.

MAIN OUTCOME MEASURES

Changes in pure tone averages (PTA) and word recognition scores (WRS) normalized to the contralateral ear.

RESULTS

During the study period, 39 of 105 included patients (37.1%) had tumor growth. Patients with tumor growth had a mean normalized increase in PTA of 8.0 dB HL (p = 0.008) corresponding to a normalized average worsening of their PTA of 1.8 dB per year. Patients with non-growing tumors less than 5 mm in maximal dimension did not have significant ongoing normalized hearing loss (p > 0.05). Patients with non-growing tumors more than or equal to 5 mm had a mean normalized increase in PTA of 7.4 dB HL (p = 0.001) corresponding to an average of 2.0 dB HL per year, which was similar to the loss observed in growing tumors regardless of size (p > 0.05). Normalized decline in PTA of at least 5 dB HL was seen in 72% of patients with growing tumors, 53% of patients with nongrowing tumors more than or equal to 5 mm, and 38% of patients with non-growing tumors less than 5 mm.

CONCLUSIONS

A long-term analysis of hearing outcomes in observed vestibular schwannoma is presented. With observation, VS more than or equal to 5 mm is associated with continued hearing loss even without tumor growth, while non-growing tumors less than 5 mm are not associated with continuing hearing loss. These data inform expectations for observed VS for providers and patients.

Hemorrhagic vestibular schwannoma: a case example of vestibular apoplexy syndrome. Illustrative case

BACKGROUND

Acute intratumoral hemorrhage within a vestibular schwannoma, or vestibular apoplexy, is a rare condition. Unlike the typical insidious vestibulopathy typically caused by vestibular schwannoma growth, patients with vestibular apoplexy have an acute and severe presentation with nausea and emesis in addition to severe vertigo and hearing loss. Here, the authors present an illustrative case demonstrating this rare clinical condition and an operative video detailing the surgical management.

OBSERVATIONS

A 76-year-old man presented to the emergency department with acute-onset dizziness, left-ear fullness, double vision, gait ataxia, emesis, and facial numbness. Imaging revealed a 2.8-cm hemorrhagic left cerebellopontine angle lesion extending into the left internal auditory canal, consistent with hemorrhagic vestibular schwannoma. The patient subsequently underwent a retrosigmoid craniotomy for resection of the hemorrhagic mass, and by 1 month after surgery, all his presenting symptoms had resolved, allowing his return to daily activities.

LESSONS

Vestibular schwannomas typically present with decreased hearing and chronic vestibulopathy. Acute presentation should raise the suspicion for an apoplectic event, and surgical debulking may lead to improvement in most vestibular symptoms.

Presacral Benign Schwannoma Mimics Malignancy on 18F-FDG and 68Ga-FAPI PET/CT

ABSTRACT

We present findings of FDG PET/CT and FAPI PET/CT in a 55-year-old woman with a history of black stools and low-back pain. Pelvic CT detected a giant presacral mass that was suspected to be malignant. 18F-FDG and 68Ga-FAPI PET/CT showed that the mass had intense activity. Pathological examination confirmed the mass as a benign schwannoma.

Absence of residual tumor tissue after Gamma Knife radiosurgery followed by resection of a vestibular schwannoma: illustrative case

BACKGROUND

Late pathology after vestibular schwannoma radiosurgery is uncommon. The authors presented a case of a resected hemorrhagic mass 13 years after radiosurgery, when no residual tumor was found.

OBSERVATIONS

A 56-year-old man with multiple comorbidities, including myelodysplastic syndrome cirrhosis, received Gamma Knife surgery for a left vestibular schwannoma. After 11 years of stable imaging assessments, the lesion showed gradual growth until a syncopal event occurred 2 years later, accompanied by progressive facial weakness and evidence of intralesional hemorrhage, which led to resection. However, histopathological analysis of the resected specimen showed hemorrhage and reactive tissue but no definitive residual tumor.

LESSONS

This case demonstrated histopathological evidence for the role of radiosurgery in complete elimination of tumor tissue. Radiosurgery for vestibular schwannoma carries a rare risk for intralesional hemorrhage in select patients.

Establishment of nomograms for the prediction of useful hearing loss in patients with neurofibromatosis type 2

INTRODUCTION

Treatment for vestibular schwannoma (VS) in patients with neurofibromatosis type 2 (NF2) is extremely challenging due to the high risk of hearing loss. The aim of this study was to develop nomograms for the prediction of useful hearing loss in patients with NF2.

METHODS

The nomogram was based on a retrospective study of 111 NF2 patients who underwent resection of large VS (> 2 cm) at Beijing Tiantan Hospital between 2011 and 2018. The utility of the proposed nomogram models was evaluated by receiver operating characteristic (ROC) curve, area under ROC curve (AUC), and calibration curve. The results were validated using a prospective cohort study on 33 patients consecutively enrolled at the same institution from 2019 to 2021.

RESULTS

On multivariate analysis of the primary cohort, large tumour size (> 3 cm) and long duration of symptoms (> 24 months) were independent risk factors for preoperative useful hearing loss (AAO-HNS Class D) (P = 0.001 and P = 0.011, respectively), while large tumour size (> 3 cm), poor hearing (Class C), and lobular growth were significantly related to postoperative useful hearing loss (P < 0.001, P = 0.031 and P = 0.033, respectively). Factors derived from multivariable analysis were all assembled into the nomogram. The calibration curve for probability of hearing loss showed good agreement between predictions by nomogram models and actual observation. The ROC curves showed good predictive accuracy of the nomogram models in both cohorts (AUC: 0.708 to 0.951).

CONCLUSION

The proposed nomograms resulted in accurate predictions of hearing outcomes for patients with NF2.

Losartan prevents tumor-induced hearing loss and augments radiation efficacy in NF2 schwannoma rodent models

Hearing loss is one of the most common symptoms of neurofibromatosis type 2 (NF2) caused by vestibular schwannomas (VSs). Fibrosis in the VS tumor microenvironment (TME) is associated with hearing loss in patients with NF2. We hypothesized that reducing the fibrosis using losartan, an FDA-approved antihypertensive drug that blocks fibrotic and inflammatory signaling, could improve hearing. Using NF2 mouse models, we found that losartan treatment normalized the TME by (i) reducing neuroinflammatory IL-6/STAT3 signaling and preventing hearing loss, (ii) normalizing tumor vasculature and alleviating neuro-edema, and (iii) increasing oxygen delivery and enhancing efficacy of radiation therapy. In preparation to translate these exciting findings into the clinic, we used patient samples and data and demonstrated that IL-6/STAT3 signaling inversely associated with hearing function, that elevated production of tumor-derived IL-6 was associated with reduced viability of cochlear sensory cells and neurons in ex vivo organotypic cochlear cultures, and that patients receiving angiotensin receptor blockers have no progression in VS-induced hearing loss compared with patients on other or no antihypertensives based on a retrospective analysis of patients with VS and hypertension. Our study provides the rationale and critical data for a prospective clinical trial of losartan in patients with VS.

"When the Benign Bleed" Vestibular Schwannomas with Clinically Significant Intratumoral Hemorrhage: A Case Series and Review of the Literature

Vestibular schwannomas (VSs) are slow-growing benign neoplasms commonly located at the cerebellopontine angle. Although clinically significant hemorrhagic VSs are rarely encountered with only 75 patients previously reported, they could be life threatening. We discuss the presentation and outcomes of three patients with hemorrhagic VS as well as review the literature for this phenomenon. Consecutive adult patients with a histologically proven diagnosis of VS over a 9-year period were retrospectively reviewed. Fifty adult patients were identified with three (6%) having clinically significant intratumoral hemorrhage. This was defined as patients having acute to subacute symptoms with frank radiological evidence of hemorrhage. The mean age of diagnosis was 62 ± 9 years and the male-to female ratio was 2:1. The mean duration of symptoms, namely headache, vertigo, and sensorineural hearing impairment, was 26 ± 4 days with one patient presenting with acute coma. Retrosigmoid craniotomy for tumor resection was performed for all patients. Histopathological examination revealed extensive areas of microhemorrhage with considerable macrophage infiltration. All three patients were discharged with no additional neurological deficit and good functional performance. Clinically significant hemorrhagic VSs are rare, and patients may present with acute to subacute (i.e., within a month) symptoms of hearing loss headache, facial, or trigeminal nerve palsy. Macrophage infiltration is frequently encountered in tumor specimens and reflects the pivotal role of chronic inflammation in their pathophysiology. Surgical resection can lead to good outcomes with timely intervention.

New developments in neurofibromatosis type 2 and vestibular schwannoma

Neurofibromatosis type 2 (NF2) is a rare autosomal dominant disorder characterized by the development of multiple nervous system tumors due to mutation in the NF2 tumor suppressor gene. The hallmark feature of the NF2 syndrome is the development of bilateral vestibular schwannomas (VS). Although there is nearly 100% penetrance by 60 years of age, some patients suffer from a severe form of the disease and develop multiple tumors at an early age, while others are asymptomatic until later in life. Management options for VS include surgery, stereotactic radiation, and observation with serial imaging; however, currently, there are no FDA-approved pharmacotherapies for NF2 or VS. Recent advancements in the molecular biology underlying NF2 have led to a better understanding of the etiology and pathogenesis of VS. These novel signaling pathways may be used to identify targeted therapies for these tumors. This review discusses the clinical features and treatment options for sporadic- and NF2-associated VS, the diagnostic and screening criteria, completed and ongoing clinical trials, quality of life metrics, and opportunities for future research.

Repeated spontaneous intra-tumoural and subarachnoid haemorrhage in an anticoagulated patient with a previously-irradiated vestibular Schwannoma: Case report

Subarachnoid hemorrhage caused by vestibular schwannomas (VS) is rare with no clear pathological mechanism supported in the existing literature. However, anticoagulation treatment as well as previous radiation therapy appear to be a crucial risk factor for subarachnoid haemorrhage from a VS. We report an unusual case of both intratumoural and subarachnoid haemorrhage in a patient with a VS on anticoagulation treatment previously treated with stereotactic radiosurgery. We emphasize the need for caution when considering the use of radiation therapy for treatment of VS in patients on chronic anticoagulation therapy.

Symptomatic Post-Radiosurgery Intratumoral Hemorrhage in a Case of Vestibular Schwannoma: A Case Report and Review of the Literature

Gamma knife radiosurgery (GKRS) is considered an established treatment for vestibular schwannoma (VS) in selected patients. Spontaneous intratumoral hemorrhage in VS after GKRS is very rare. In this report, we present a 63-year-old gentleman who had right-side severe sensorineural hearing loss on MRI showing a right cerebellopontine angle tumor (volume 4.96 cm3) with an internal acoustic meatus extension. He underwent GKRS with the prescription dose of 12 Gy to the 50% isodose line, covering 4.66 cm3 (i.e., 94%) of the tumor. Ten days later, he experienced a symptomatic intra-lesional hemorrhage with a mass effect over the brainstem. When symptoms did not resolve after an initial conservative approach, he underwent surgical decompression of the lesion. Postoperatively, the patient had facial palsy but was free of disabling vertigo and ataxia. At the 6-month follow-up, he was doing well without any other complaints. Although rare, an intralesional bleed can occur after GKRS in VS and should be suspected when new severe symptoms develop immediately after therapy.

Tumor-associated hemorrhage in patients with vestibular schwannoma

OBJECT

Intratumoral hemorrhage (ITH) associated with vestibular schwannomas (VS) is very rare. We retrospectively analyzed VS patients presenting with ITH in our department to further gain a better understanding of this uncommon clinical presentation.

METHODS

We treated seven patients who had VS presenting with ITH between January 2012 and June 2017. All the patients had preoperative computed tomography (CT), computed tomography angiography (CTA), and magnetic resonance imaging(MRI) done which aided in the radiological diagnosis as well as postoperative MRI to confirm the resection extent of the VS. Continuous electrophysiological monitoring of cranial nerves was carried out during surgery.

RESULTS

Of the seven patients, three were male and four were female. Their ages ranged from 42 to 71 years (average age, 57.4 years). Two patients reported a history of hypertension. Sudden onset or rapid worsening of clinical symptoms occurred in five patients at time of hemorrhage. The mean diameter of the lesions was 4.1 cm (range, 3.0-5.0 cm). No patient had a pretreatment of stereotactic radiosurgery. Gross total resection was achieved in four cases and subtotal resection in three cases. There were no surgery-related neurological deficits but one patient died 18 days after surgery. Follow-up visits were scheduled at 6 months postoperatively and two patients had tumor recurrence and received stereotactic radiosurgery again.

CONCLUSIONS

The incidence of ITH in VS is relatively rare and hypertension may highly correlate with ITH in VS. In comparison with peritumoral adhesion caused by chronic inflammation in multicystic VS with microhemorrhage,ITH caused by acute massive hemorrhage will not increase the extent of peritumoral adhesion immediately. The prognosis of surgery for patients with acute hemorrhagic VS may be better than that for microhemorrhage in multicystic VS. Besides, timely microsurgical treatment is also important to relieve symptoms.

Chances of Improvement in Cases of Vestibular Schwannoma Presenting with Facial Nerve Weakness: Presentation of Two Cases and Literature Review

Background and Study Aim  Facial nerve (FN) weakness as a presenting feature in vestibular schwannoma (VS) is extremely rare. We are presenting two different cases of VS with significant facial weakness and reviewed the literature for similar cases. Methods and Results  We are presenting two cases of VS with significant facial weakness. The first case was a 63-year-old male patient presented with 3 weeks' history of severe left-sided facial weakness (House-Brackmann [HB] grade V) and hearing loss. Magnetic resonance imaging (MRI) of the brain showed a tumor in the left internal auditory canal. Gross total removal with anatomical and physiological FN preservation was performed through a retrosigmoid approach under neurophysiological monitoring. FN function improved postoperatively to HB grade II after 16 months. The other case was 83-year-old male patient presented with sudden left-sided hearing loss and severe facial weakness (HB grade V). MRI of the brain 2.5 years before showed a left-sided (Class-T3A) cystic VS. The tumor was asymptomatic; wait-and-scan strategy was advised by the treating neurologist. Recent MRI of the brain showed approximately three times enlargement of the tumor with brain stem compression, extensive cystic changes, and suspected intratumoral hemorrhage. Surgery was performed; the tumor was subtotally removed through a retrosigmoid approach with intraoperative FN monitoring. The FN was anatomically preserved; however, physiological preservation was not possible. Severe facial weakness with incomplete lid closure persisted postoperatively. Conclusion  Surgical treatment could be offered to cases of suspected VS presenting with facial weakness, as these cases may still have a chance for improvement especially in laterally located tumors.

An unusual case of repeated intracranial hemorrhage in vestibular schwannoma

BACKGROUND

Symptomatic intratumoral hemorrhage (ITH) in vestibular schwannoma (VS) is rare. A repeated hemorrhage is, therefore, even more exceptional. Repeated ITH has been reported in four cases thus far in English literature. Here, we describe a patient with a Koos grade D VS who presented to our Skull Base team with repeated ITH and an unexpected disease course.

CASE DESCRIPTION

A 76-year-old woman presented with hearing loss due to polycystic VS on the left side. Five years later, the patient was presented with facial palsy caused by hemorrhage in the VS. The patient had an eventful medical history that necessitated the use of anti-coagulants. The patient suffered from three subsequent hemorrhages preoperatively and one hemorrhage 36 h postoperatively.

CONCLUSION

We have experienced multiple repeated hemorrhages in a patient with a polycystic VS, and despite surgical intervention, the outcome was unfavorable.

Clinically significant intratumoral hemorrhage in patients with vestibular schwannoma

OBJECTIVES

The frequency of intratumoral hemorrhage (ITH) in vestibular schwannoma (VS) remains undefined.

METHODS

Retrospective case series of all patients diagnosed with hemorrhagic VS between 2003 and 2015 at a single tertiary academic skull base center.

RESULTS

Five patients with ITH were evaluated, representing 0.4% of all newly diagnosed VS evaluated at the authors' center during this time. The median age at time of diagnosis was 66 years (range 39-83), four of five cases occurred in men, and all had sporadic unilateral tumors. The frequency of ITH among patients receiving anticoagulation was 5.6% (2 of 36), compared to only 0.2% (3 of 1356) in non-anticoagulated patients (P = 0.006), representing a 25-fold increase. At time of hemorrhage, all patients had acute onset of headache, disequilibrium, and progression of hearing loss; three reported trigeminal symptoms, and two exhibited acute moderate facial paresis. The median tumor size at diagnosis of hemorrhage was 3.1 cm (range 2.4-4.2 cm), and three patients had radiological evidence of hydrocephalus. All patients underwent microsurgical resection. There were no perioperative deaths. At a median follow-up of 25 months (3-70 months), no patient has experienced tumor recurrence.

CONCLUSION

Tumor-associated hemorrhage in VS occurs in 0.4% of cases and commonly presents with acute neurological change. The risk of clinically significant hemorrhage is greater in patients receiving anticoagulation compared to the general VS population. Prompt microsurgical resection should be pursued when possible since tumor removal may improve neurological symptoms, relieve brainstem compression, and reduce the risk of repeat hemorrhage.

LEVEL OF EVIDENCE

4. Laryngoscope, 127:1420-1426, 2017.

Hearing Outcomes After Stereotactic Radiosurgery for Vestibular Schwannomas : Mechanism of Hearing Loss and How to Preserve Hearing

The use of stereotactic radiosurgery (SRS) expanded to include the treatment of vestibular schwannomas (VSs) in 1969; since then, efforts to increase tumour control and to reduce cranial neuropathy have continued. Using the currently recommended marginal dose of 12-13 Gy, long-term reported outcomes after SRS include not only excellent tumour control rates of 92-100 % but also outstanding functional preservation of the trigeminal and facial nerves, with values of 92-100 % and 94-100 %, respectively. Nonetheless, hearing preservation remains in the range of 32-81 %. Previous studies have suggested possible prognostic factors of hearing preservation such as the Gardner-Robertson grade, radiation dose to the cochlea, transient volume expansion (TVE) after SRS, length of irradiated cochlear nerve, marginal dose to the tumour, and age. However, we still do not clearly understand why patients lose their hearing after SRS for VS.Relevant to these considerations, one study recently reported that the auditory brainstem response (ABR) wave V latency and waves I and V interval (IL_I-V) correlated well with intracanalicular pressure values and even with hearing level. The demonstration that ABR values, especially wave V latency and IL_I-V, correlate well with intracanalicular pressure suggests that patients with previously elevated intracanalicular pressure might have an increased chance of hearing loss on development of TVE, which has been recognised as a common phenomenon after SRS or stereotactic radiotherapy (SRT) for intracranial schwannomas.In our experience, the ABR IL_I-V increased during the first 12 months after SRS for VSs in patients who lost their serviceable hearing. The effect of increased ABR IL_I-V on hearing outcome also became significant over time, especially at 12 months after SRS, and was more prominent in patients with poor initial pure-tone average (PTA) and/or ABR values. We hypothesise that patients with considerable intracanalicular pressure at the time of SRS are prone to lose their serviceable hearing due to the added intracanalicular pressure induced by TVE, which usually occurs within the first 12 months after SRS for VSs. Using these findings, we suggested a classification system for the prediction of hearing outcomes after SRS for VSs. This classification system could be useful in the proper selection of management modalities for hearing preservation, especially in patients with only hearing ear schwannoma or neurofibromatosis type 2.Advances in diagnostic tools, treatment modalities, and optimisation of radiosurgical dose have improved clinical outcomes, including tumour control and cranial neuropathies, in patients with VSs. However, the preservation of hearing function still falls short of our expectation. A prediction model for hearing preservation after each treatment modality will guide the proper selection of treatment modalities and permit the appropriate timing of active treatment, which will lead to the preservation of hearing function in patients with VSs.

Case-control studies in neurosurgery

OBJECT

Observational studies, such as cohort and case-control studies, are valuable instruments in evidence-based medicine. Case-control studies, in particular, are becoming increasingly popular in the neurosurgical literature due to their low cost and relative ease of execution; however, no one has yet systematically assessed these types of studies for quality in methodology and reporting.

METHODS

The authors performed a literature search using PubMed/MEDLINE to identify all studies that explicitly identified themselves as "case-control" and were published in the JNS Publishing Group journals (Journal of Neurosurgery, Journal of Neurosurgery: Pediatrics, Journal of Neurosurgery: Spine, and Neurosurgical Focus) or Neurosurgery. Each paper was evaluated for 22 descriptive variables and then categorized as having either met or missed the basic definition of a case-control study. All studies that evaluated risk factors for a well-defined outcome were considered true case-control studies. The authors sought to identify key features or phrases that were or were not predictive of a true case-control study. Those papers that satisfied the definition were further evaluated using the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) checklist.

RESULTS

The search detected 67 papers that met the inclusion criteria, of which 32 (48%) represented true case-control studies. The frequency of true case-control studies has not changed with time. Use of odds ratios (ORs) and logistic regression (LR) analysis were strong positive predictors of true case-control studies (for odds ratios, OR 15.33 and 95% CI 4.52-51.97; for logistic regression analysis, OR 8.77 and 95% CI 2.69-28.56). Conversely, negative predictors included focus on a procedure/intervention (OR 0.35, 95% CI 0.13-0.998) and use of the word "outcome" in the Results section (OR 0.23, 95% CI 0.082-0.65). After exclusion of nested case-control studies, the negative correlation between focus on a procedure/intervention and true case-control studies was strengthened (OR 0.053, 95% CI 0.0064-0.44). There was a trend toward a negative association between the use of survival analysis or Kaplan-Meier curves and true case-control studies (OR 0.13, 95% CI 0.015-1.12). True case-control studies were no more likely than their counterparts to use a potential study design "expert" (OR 1.50, 95% CI 0.57-3.95). The overall average STROBE score was 72% (range 50-86%). Examples of reporting deficiencies were reporting of bias (28%), missing data (55%), and funding (44%).

CONCLUSIONS

The results of this analysis show that the majority of studies in the neurosurgical literature that identify themselves as "case-control" studies are, in fact, labeled incorrectly. Positive and negative predictors were identified. The authors provide several recommendations that may reverse the incorrect and inappropriate use of the term "case-control" and improve the quality of design and reporting of true case-control studies in neurosurgery.

Intratumoral haemorrhage causing an unusual clinical presentation of a vestibular schwannoma

We present a case of an elderly woman with no history of audiological disease with sudden onset of visual and hearing deficits associated with systemic clinical signs. On examination she had impairment of right CNs from V to X. CT and MR imaging demonstrated a cystic vestibular schwannoma with a rare intralesional fluid-fluid level correlated to a recent bleed. We include high quality MR images to show the acute impairment of the cranial nerves next to the tumour after acute bleeding. Our case report includes a voxel-based morphometry (VMB) analysis of the tumour that, as far as we know, has never been done before for such a tumour. VBM analysis was performed to calculate the hypothesized volume changes after the acute bleed which likely resulted in a sudden increase in the overall size of the tumour resulting in atypical clinical signs and symptoms due to the establishment of a mechanical conflict with the adjacent cranial nerves.

An update on unilateral sporadic small vestibular schwannoma

Advances in neuroimaging have increased the detection rate of small vestibular schwannomas (VSs, maximum diameter < 25 mm). Current management modalities include observation with serial imaging, stereotactic radiosurgery, and microsurgical resection. Selecting one approach over another invites speculation, and no standard management consensus has been established. Moreover, there is a distinct clinical heterogeneity among patients harboring small VSs, making standardization of management difficult. The aim of this article is to guide treating physicians toward the most plausible therapeutic option based on etiopathogenesis and the highest level of existing evidence specific to the different cohorts of hypothetical case scenarios. Hypothetical cases were created to represent 5 commonly encountered scenarios involving patients with sporadic unilateral small VSs, and the literature was reviewed with a focus on small VS. The authors extrapolated from the data to the hypothetical case scenarios, and based on the level of evidence, they discuss the most suitable patient-specific treatment strategies. They conclude that observation and imaging, stereotactic radiosurgery, and microsurgery are all important components of the management strategy. Each has unique advantages and disadvantages best suited to certain clinical scenarios. The treatment of small VS should always be tailored to the clinical, personal, and social requirements of an individual patient, and a rigid treatment protocol is not practical.

The rise and fall of "biopsy and radiate": a history of surgical nihilism in glioma treatment

Many neurosurgeons take a nihilistic approach to surgical treatment of gliomas, stating the inability to achieve a cure. Where this idea comes from is somewhat nebulous to most neurosurgeons. A review of the scientific studies supporting the commonly held beliefs about gliomas shows that these ideas regarding the surgical treatment of gliomas are based on overgeneralizations of data from older studies. One should avoid the temptation to apply them to the greater concept of what gliomas are, how they behave, and what should be done, but rather we should continue to scientifically evaluate the role of surgical resection in glioma treatment.

Audiological correlates of tumor parameters in acoustic neuromas

The objective of this study was undertaken to evaluate a correlation of pure tone audiometry, speech audiometry with tumor size, the presence of intrameatal extension, contralateral pure tone audiometry, and contralateral speech audiometry results at acoustic neuroma (AN) patients. Seventy-six patients with a unilateral-cerebellopontine angel tumor with/without internal acoustic canal (IAC) were included in this study. Data on pure tone audiometry, speech discrimination scores (SDS), speech reception thresholds (SRT), tumour size, and extension to IAC were analyzed retrospectively. As a result, patients with unilateral ANs had an asymmetric sensorineural hearing loss and had an asymmetric finding on the results of speech audiometry was present. We could not find any correlation between the size of the tumor and the hearing levels at each frequency. In addition, there appeared to be no significant correlation between the extension of tumor to the IAC and the audiological findings.