Cystic Vestibular Schwannomas Research Articles

Case report: Cystic vestibular schwannoma

Background: Cerebellopontine angle tumors are a severe condition because of their life-threatening and functional loss potential, explained by the narrowness of the posterior fossa. The vestibular schwannoma, or acoustic neuroma, is a benign, well-circumscribed extraaxial tumor that arises from Schwann cells of the vestibulocochlear cranial nerve. The tumor is usually mainly solid, but can sometimes develop small cystic areas, due to degenerative modifications, causing microcyst formation. The coalescent of small cysts leading to forming a larger one, and responsible of a predominant cystic contingent, is rare, which makes interesting the case we are about to present. Case report: We are about to report the case of a 64-year-old male patient, with no particular medical history, which clinical interview has noted only tinnitus as a present symptom. He had experienced one year ago several disequilibrium and dizziness episodes, who have subsequently stopped over time, without any particular treatment. He also felt a little loss of hearing, especially in the left ear, but thought it was probably age related. No clinical abnormality including the facial nerve palsy was found. The MRI showed a stage 4 (Koos classification) left cystic vestibular schwannoma. This lesion was compressing the left vertebral and basilar arteries, the brain stream, the left cerebellar hemisphere, the left middle cerebellar peduncle, and the fourth ventricle, causing a triventricular hydrocephalus. After reviewing all potential therapeutic options, the patient declined surgery and decided to postpone the treatment. Conclusion: MRI is definitely the best way to explore the posterior fossa, especially the cerebellopontine angle, and helps us differentiate between all numerous tumors than can develop in this space.

Identifying Tumor Microenvironment Biomarkers in Adherent and Cystic Vestibular Schwannomas.

A subset of vestibular schwannomas (VSs), including cystic tumors, have higher postoperative morbidity because of the presence of adhesions between the tumor, facial nerve (FN), and brainstem. We identify tumor microenvironment (TME) biomarkers to better classify these tumors and predict the degree of tumor adherence. Retrospective case series. Tertiary skull base referral center. Adult patients with cystic and solid VS matched in tumor size who underwent surgical resection were included. Expressions of seven biomarkers of extracellular matrix remodeling and tumor immune response were quantified via immunohistochemistry. The distribution of CD45+ immune cells was evaluated in intratumoral and perivascular compartments. The degree of tumor adherence was categorized as none, adherent to FN, or adherent to both FN and brainstem. Twenty-eight patients were included. Cystic VSs were significantly more adherent than solid VSs ( p = 0.02). Patients with adherent VS had shorter duration of symptoms and were more likely to undergo subtotal resection. In solid tumors, matrix metalloproteinase (MMP)-2 expression ( p = 0.02) and CD163+ macrophage infiltration ( p = 0.007) were correlated with tumor size. Linear discriminant analyses (LDAs) demonstrated MMP-2, MMP-14, CD80, CD163, and perivascular CD45 to be individually predictive of the degree of tumor adherence (all p < 0.05), with perivascular CD45 being the best independent predictor ( p = 0.005). An LDA model including these biomarkers demonstrated 100% accurate discrimination of all three levels of tumor adherence ( p = 0.04). Adherent VS have a distinct proinflammatory TME characterized by elevated MMP expression, enrichment of tumor-associated macrophages, and perivascular immune cell infiltration.

RADT-23. STEREOTACTIC RADIOSURGERY FOR CYSTIC VESTIBULAR SCHWANNOMA - A SYSTEMATIC REVIEW

Abstract BACKGROUND Cystic vestibular schwannoma, also historically known as cystic acoustic neuroma, is a benign intracranial tumor that can form between the pons and the cerebellum in an area known as the cerebellopontine angle. These brain tumors can be treated with radiotherapy, surgical resection, or radiosurgery. However, there is no consensus on which treatment modality is the most effective with minimal to no complications. METHODS A comprehensive review of clinical articles reporting stereotactic radiosurgery treatment for cystic vestibular schwannoma was performed. PubMed, Web of Science, Cochrane, Scopus, and Embase were independently queried and the PRISMA guidelines were followed throughout the screening process. We identified high-quality studies representing data from 186 patients. We extracted patient demographics, tumor characteristics, type of stereotactic radiosurgery, dosage, tumor control rate, and follow-up time. All the available data points were used to evaluate the effect of stereotactic radiosurgery on tumor control rate for cystic vestibular schwannoma. RESULTS A total of 186 patients underwent stereotactic radiosurgery with Gamma Knife (n = 178) and CyberKnife (n = 8). The average tumor volume was 6.47 cm3 (range 4.82 – 8.4 cm3, SD ± 1.8). The average marginal and maximum doses were 12.8 Gy (12.5 -13 Gy, SD ± 0.25) and 24.9 Gy (23.8 - 26 Gy, SD ± 1.10), respectively. The average follow-up time was 63.5 months (53.5 – 74 months, SD ± 10.2). Following stereotactic radiosurgery treatment for cystic vestibular schwannoma across all studies, almost 92% of patients had tumor control at follow-up, (95%-CI: 91.4 - 91.6). CONCLUSIONS Our systematic review revealed that stereotactic radiosurgery can provide adequate tumor control for cystic vestibular schwannoma. Therefore, stereotactic radiosurgery is an effective treatment choice in patients with cystic vestibular schwannoma.

Cytokine Profiling of Cyst Fluid and Tumor-Associated Macrophages in Cystic Vestibular Schwannoma.

The vestibular schwannoma (VS) secretome can initiate monocyte recruitment and macrophage polarization to M1 (proinflammatory) and/or M2 (protumorigenic) phenotypes, which in turn secrete additional cytokines that contribute to the tumor microenvironment. Profiling cyst fluid and cerebrospinal fluid (CSF) in cystic VS provides a unique opportunity to understand mechanisms that may contribute to tumor progression and cyst formation. Cystic VSs secrete high levels of cytokines into cyst fluid and express abundant M1 and M2 macrophages. Tumor, CSF, and cyst fluid were prospectively collected from 10 cystic VS patients. Eighty cytokines were measured in fluid samples using cytokine arrays and compared with normal CSF from normal donors. Immunofluorescence was performed for CD80 + M1 and CD163 + M2 macrophage markers. Demographic, audiometric, and radiographic information was obtained through retrospective chart review. Cyst fluid expressed more osteopontin and monocyte chemotactic protein-1 (MCP-1; p < 0.0001), when compared with normal CSF. Cyst fluid also expressed more protein ( p = 0.0020), particularly MCP-1 ( p < 0.0001), than paired CSF from the same subjects. MCP-1 expression in cyst fluid correlated with CD80 + staining in VS tissue ( r = 0.8852; p = 0.0015) but not CD163 + staining. Cyst fluid from cystic VS harbored high levels of osteopontin and MCP-1, which are cytokines important in monocyte recruitment and macrophage polarization. MCP-1 may have a significant role in molding the tumor microenvironment, by polarizing monocytes to CD80 + M1 macrophages in cystic VS. Further investigations into the role of cytokines and macrophages in VS may lead to new avenues for therapeutic intervention.

P11.38.A CYSTIC VESTIBULAR SCHWANNOMA - A SUBGROUP ANALYSIS FROM A COMPARATIVE STUDY BETWEEN RADIOSURGERY AND MICROSURGERY

Abstract BACKGROUND Some vestibular schwannoma (VS), show cystic morphology. It is known that these cystic vestibular schwannomas (cVS) bear different surgical risk profile compared to non-cystic VS (ncVS) in surgical treatment. This study aims to analyze the management of cVS compared to ncVS in a dual center study of surgically (SURG) and radiosurgically (SRS) treated VS patients. MATERIAL AND METHODS This is a retrospective multi-center cohort study. Data was retrospectively collected from two large centers involved in the treatment of vestibular schwannomas for patients between 2005 und 2011 to enable long-term follow-up (FU). Tumor size was classified by Koos Classification. Previously treated VS and VS associated with Neurofibromatosis were excluded. Clinical state was reported by House and Brackmann (H&amp;B) and Gardner-Robertson (G&amp;R) scale (with H&amp;B and G&amp;R 1-2 considered as good outcome), and Recurrence-free-survival (RFS) was assessed radiographically by contrast-enhanced MR imaging. Data on VS-associated symptoms like trigeminal affection, tinnitus, and vertigo/imbalance were also collected. RESULTS The study population included N=901 patients, who were treated in both centers. N=559 (62%) patients were treated by SRS, and N=342 (38%) patients by SURGERY. N=55 (6%) of all patients showed cystic MR-morphology. These were more often treated by SURG (N=31/55, 58%) compared to ncVS (N=311/845, 37%) (p=0.002). Patients with cVS were indifferent in mean age compared to ncVS. The rate of women was higher in cVS (64%), compared to ncVS (55%) (p=0.001). The overall incidence of recurrence was 16% in cVS (8% in ncVS). Tumor control was worse in cVS treated by SRS (N=6/24, 25%) compared to SURGERY (N=3/32, 9%). When surgically treated, gross total resection (GTR) was achieved in 87% in cVS, whereas this rate was higher in non-cystic VS at 96% (p=0.001). The number of patients N=5/32 (16%) with postoperative relevant facial palsy (HB&amp;gt;2) was significantly higher in cVS (ncVS: N=28/310; 9%). CONCLUSION Tumor control in cVS is significantly worse in SRS compared to SURG and SRS-treated ncVS. However, when cVS is treated surgically, the rate of GTR is lower and the number of patients with relevant postoperative facial palsy higher compared to ncVS. Cystic morphology in VS poses a challenge in management (both SRS and SURG) compared to non-cystic tumors. Treatmend decision and patients' consultation should contemplate and address negative prognostic factor of cystic morphology in VS.

OS09.7.A THE ROLE OF MICROSURGERY IN THE FIRST LINE TREATMENT OF VESTIBULAR SCHWANNOMA: IT IS ALL ABOUT THE ODDS

Abstract BACKGROUND Given the risk for a deterioration of facial function (FDR), first-line (1stline) microsurgery (MS) is discouraged in vestibular schwannoma (VS). In contrast, 1stline radiosurgery (SRS) preserves facial function but has a higher recurrence rate (RR). As salvage VS surgery is very challenging, it could be reasonable to accept a slightly increased FDR of 1stline MS in favor of the lower RR. The aim of the present study was to determine the FDR and RR values of salvage surgery and to calculate the break-even point of MS in the 1stline VS treatment. MATERIAL AND METHODS This retrospective study analyzed all patients with unilateral VS undergoing microsurgery between 03/2008 and 10/2021 (n=1470). We identified patient with 2ndline MS after previous MS (MS-MS) or radiosurgery (SRS-MS) as well as patients with 3rdline MS (MS-SRS-MS). After reviewing patients’ clinical and imaging data, we determined FDR and RR for each cohort. This data was compared to a 1stline MS cohort (CTRL) with a follow-up of at least 10 years (n=572). A mathematical prediction model (MPM) was applied to calculate the odds ratio (OR) of different treatment strategies (i.e., MS-MS, SRS-MS, MS-SRS-MS) depending on different FDR and RR values. RESULTS We identified 48 patients with 2ndline and 11 patients with 3rdline MS after failed MS/SRS. Time to recurrence in relation to the initial treatment was shortest in SRS-MS (35±34 mo) compared to MS-MS (128±179 mo) and MS-SRS-MS (38±17 mo). These patients had a significant worse preoperative facial function than CTRL patients. Extent-of-resection (EOR) was diminished in 2ndline (79% and 75%) compared to 1stline MS (97%). Both the FDR and RR were significantly increased in MS-MS (FDR:17%, RR:14%) and SRS-MS (FDR:45%, RR:5%) compared to CTRL (FDR:12%, RR:4%). Notably, MS-SRS-MS was associated with the highest FDR (60%) while having the lowest GTR rate (54%). MPM indicated that FDR&amp;lt;15% and RR&amp;lt;5% justify a 1stline MS. In the present cohort, these criteria were met for Koos 1-3 tumors (FDR:0-7%, RR:0-3%). CONCLUSION Recurrent VS surgeries fare much worse considering FDR, EOR and RR than first-line surgeries. Hence, reducing the RR of the first-line VS treatment is required. In smaller VS, the surgical oncofunctional outcome can reach the break-even point favoring microsurgery over radiosurgery as first-line treatment option. However, in situations with high FDR (e.g., large or cystic VS) a more conservative surgical approach might be beneficial.

Morphology of intra tumoral cystic vestibular schwannoma and their response to gammaknife radiosurgery

BackgroundCystic vestibular schwannoma (CVS) traditionally considered as poor responder to gammaknife radiosurgery (GKRS). Their longterm radiobiological behavior is less known. Here we discuss 38 cases with intra tumoral cyst CVS primarily treated with GKRS. Tumor morphology was assessed to understand their response to GKRS. MethodsTotal 38 patients(21 male and 17 female with median age of 41.7 years) of CVS treated with GKRS were retrospectively analysed. Tumors were divided as predominantly (greater than50% of total tumor volume) cystic or solid. They were subclassified as type 1 (predominantly cystic CVS, single cyst), type 2 (predominantly solid CVS, single cysts), type 3 (multicystic CVS). The entire cyst was incorporated for radiosurgery. The results were compared with volume matched control of 58 solid tumors(SVS). ResultThe median tumor volume of CVS was 5.8 cc. The median tumor volume reduction was 44.5 % at a median follow-up of 68.5 months (30–110 months). Median tumor volume reduction was 68.5 %, 34.0%, 11.0.%, 30.5% at a median follow up of 52.5months, 66 months, 78.6 months, 96.5 months for type 1 CVS, type 2 CVS, type 3 CVS and SVS respectively. One patient with multicystic CVS showed increased tumor volume and expired after 9 months of surgery.The tumor volume reduction in type 1CVS was statistically significant as compared to type 3 CVS and SVS. However the tumor volume reduction among other groups did not differ significantly. ConclusionIntra tumoral cystic components respond better to gammaknife radiosurgery in CVS. Tumor with single cyst respond better than multicystic vestibular schwannoma.

Association Between Pseudoprogression of Vestibular Schwannoma After Radiosurgery and Radiological Features of Solid and Cystic Components.

The pathophysiology of vestibular schwannoma (VS) pseudoprogression after Gamma Knife radiosurgery (GKRS) remains unclear. Radiological features in pretreatment magnetic resonance images may help predict VS pseudoprogression. This study used VS radiological features quantified using an automated segmentation algorithm to predict pseudoprogression after GKRS treatment. This is a retrospective study comprising 330 patients with VS who received GKRS. After image preprocessing and T2W/contrast-enhanced T1-weighted image (CET1W) image generation, with fuzzy C-means clustering, VSs were segmented into solid and cystic components and classified as solid and cystic. Relevant radiological features were then extracted. The response to GKRS was classified into "nonpseudoprogression" and "pseudoprogression/fluctuation". The Z test for two proportions was used to compare solid and cystic VS for the likelihood of pseudoprogression/fluctuation. Logistic regression was used to assess the correlation between clinical variables and radiological features and response to GKRS. The likelihood of pseudoprogression/fluctuation after GKRS was significantly higher for solid VS compared with cystic VS (55% vs 31%, P < .001). For the entire VS cohort, multivariable logistic regression revealed that a lower mean tumor signal intensity (SI) in T2W/CET1W images was associated with pseudoprogression/fluctuation after GKRS ( P = .001). For the solid VS subgroup, a lower mean tumor SI in T2W/CET1W images ( P = .035) was associated with pseudoprogression/fluctuation after GKRS. For the cystic VS subgroup, a lower mean SI of the cystic component in T2W/CET1W images ( P = .040) was associated with pseudoprogression/fluctuation after GKRS. Pseudoprogression is more likely to occur in solid VS compared with cystic VS. Quantitative radiological features in pretreatment magnetic resonance images were associated with pseudoprogression after GKRS. In T2W/CET1W images, solid VS with a lower mean tumor SI and cystic VS with a lower mean SI of cystic component were more likely to have pseudoprogression after GKRS. These radiological features can help predict the likelihood of pseudoprogression after GKRS.

Surgical treatment of cystic vestibular schwannoma (clinical case)

Objective: to demonstrate the result of successful treatment of a patient with cystic vestibular schwannoma. Currently, there is no single approach to choosing a surgical treatment method of cystic vestibular schwannoma. When choosing tactics, neurosurgeons are guided, as a rule, by the location of the tumor and the thickness of its walls. Emptying the cyst can also lead to a change in the existing relationship of the tumor with neighboring structures, especially with the facial nerve. The chosen method of treatment of this disease in the form of total removal of cystic vestibular schwannoma under the control of neurophysiological monitoring made it possible to achieve early activation of the patient and avoid postoperative complications, preserve the function the facial and trigeminal nerves involved in the tumor capsule.

Perfusion-weighted imaging in vestibular schwannoma: the influence that cystic status and tumor size have on perfusion profiles.

The perfusion profile of vestibular schwannomas (VSs) and the factors that influence it have yet to be determined. Twenty patients with sporadic VS were analyzed by calculating parameters related to the extravascular extracellular space (EES)-the volume transfer constant between a vessel and the EES (Ktrans); the EES volume per unit of tissue volume (Ve); and the rate transfer constant between EES and blood plasma (Kep)-as well as the relative cerebral blood volume (rCBV), and by correlating those parameters with the size of the tumor and its structure (solid, cystic, or heterogeneous). Although Ktrans, Ve, and Kep were measurable in all tumors, rCBV was measurable only in large tumors. We detected a positive correlation between Ktrans and rCBV (r = 0.62, p = 0.031), a negative correlation between Ve and Kep (r = -0.51, p = 0.021), and a positive correlation between Ktrans and Ve only in solid VSs (r = 0.64, p = 0.048). Comparing the means for small and large VSs, we found that the former showed lower Ktrans (0.13 vs. 0.029, p < 0.001), higher Kep (0.68 vs. 0.46, p = 0.037), and lower Ve (0.45 vs. 0.83, p < 0.001). The mean Ktrans was lower in the cystic portions of cystic VSs than in their solid portions (0.14 vs. 0.32, p < 0.001), as was the mean Ve (0.37 vs. 0.78, p < 0.001). There were positive correlations between the solid and cystic portions for Ktrans (r = 0.71, p = 0.048) and Kep (r = 0.74, p = 0.037). In VS, tumor size appears to be consistently associated with perfusion values. In cystic VS, the cystic portions seem to have lower Ktrans and Ve than do the solid portions.

Long-term results of upfront, single-session Gamma Knife radiosurgery for large cystic vestibular schwannomas.

Anecdotally, cystic vestibular schwannomas (cVSs) are regarded to have unpredictable biologic activity with poorer clinical results, and most studies showed a less favorable prognosis following surgery. While stereotactic radiosurgery (SRS) is a well-established therapeutic option for small- to medium-sized VSs, cVSs are often larger, thus making upfront SRS more complicated. The purpose of this retrospective study was to assess the efficacy and safety of upfront SRS for large cVSs. The authors reviewed the data of 54 patients who received upfront, single-session Gamma Knife radiosurgery (GKRS) with a diagnosis of large cVS (> 4 cm3). Patients with neurofibromatosis type 2, multiple VSs, or recurrent VSs and < 24months of clinical and neuroimaging follow-up were excluded. Hearing loss (48.1%) was the primary presenting symptom. The majority of cVSs were Koos grade IV (66.7%), and the most prevalent cyst pattern was "mixed pattern of small and big cysts" (46.3%). The median time between diagnosis and GKRS was 12months (range, 1-147months). At GKRS, the median cVS volume was 6.95 cm3 (range, 4.1-22 cm3). The median marginal dose was 12Gy (range, 10-12Gy). The mean radiological and clinical follow-up periods were 62.2 ± 34.04months (range, 24-169months) and 94.9 ± 45.41months (range, 24-175months), respectively. At 2, 6, and 12years, the tumor control rates were 100%, 95.7%, and 85.0%, respectively. Tumor shrinkage occurred in 92.6% of patients (n = 50), tumor volume remained stable in 5.6% of patients (n = 3), and tumor growth occurred in 1.9% of patients (n = 1). At a median follow-up of 53.5months, the pre-GKRS tumor volume significantly decreased to 2.35 cm3 (p < 0.001). While Koos grade 3 patients had a greater possibility of attaining higher volume reduction, "multiple small thick-walled cyst pattern" and smaller tumor volumes decreased the likelihood of achieving higher volume reduction. Serviceable hearing (Gardner-Robertson Scale I-II) was present in 16.7% of patients prior to GKRS and it was preserved in all of these patients following GKRS. After GKRS, 1.9% of patients (n = 1) had new-onset trigeminal neuralgia. There was no new-onset facial palsy, hemifacial spasm, or hydrocephalus. Contrary to what was believed, our findings suggest that upfront GKRS seems to be a safe and effective treatment option for large cVSs.

Natural History of Cystic Vestibular Schwannomas.

To determine the natural history of cystic vestibular schwannomas (VS). Retrospective cohort. Single tertiary academic hospital. Adults diagnosed with cystic VS who had at least 2 MRIs performed at least 6 months apart between 2008 and 2016 with no intervening treatment. Volumetric growth rates of both the entire tumor and individual cystic and solid components were measured. Linear growth rate of the entire tumor was assessed using the largest diameter parallel to the petrous face at the cerebellopontine angle (CPA). Twenty-one patients met inclusion criteria. The average volumetric growth rate of the tumor was 1.1 ± 2 (range: -1.2 to 7.8), while the average growth rate of the cystic component was 0.8 ± 1.6 (range: -0.5 to 5.3) cm3/year. The CPA diameter of the tumor demonstrated an average linear growth rate of was 1.2 ± 4.4 (range: -8to 13.5) mm/year. With regards to tumor diameter, 9/21 (42.9%) remained stable, 3/21 (14.2%) decreased in size, while 9/21 (42.9%) increased in size. Cystic tumors demonstrate a wide variability in growth rate. Larger, multi-center studies will be required to further compare this relationship to solid tumors.

Letter to the Editor Regarding “Postoperative Functional Preservation of Facial Nerve in Cystic Vestibular Schwannoma”

Letter to the Editor Regarding “Postoperative Functional Preservation of Facial Nerve in Cystic Vestibular Schwannoma”

In Reply to the Letter to the Editor Regarding “Postoperative Functional Preservation of Facial Nerve in Cystic Vestibular Schwannoma”

In Reply to the Letter to the Editor Regarding “Postoperative Functional Preservation of Facial Nerve in Cystic Vestibular Schwannoma”

Quantitative assessment of brainstem distortion in vestibular schwannoma and its implication in occurrence of hydrocephalus

Purpose Anatomical distortion directly affects the clinical status of patients with vestibular schwannomas (VSs). It may vary for a given tumor size due to variability in posterior fossa anatomy. We aimed to quantitatively assess brainstem distortion (BSD) and review its role in occurrence of hydrocephalus associated with VSs. Methods Sixty-six patients with small (<3 cm, n= 8; 12.1%); large (3–4 cm; n= 26; 39.4%) and giant (>4 cm; n= 32; 48.5%) VSs were included. Cystic VSs were excluded. Tumor size, tumor-extent, linear displacement (LD; distance between line bisecting pons (line 1) and posterior fossa midline (line 2)) and angular distortion (AD; angle subtended between lines 1 and 2) in axial-T2-MRI section through pons, and their effect on hydrocephalus were assessed. Results Significant BSD occurred in a younger age (p value = .004/.003), larger-sized tumor (p value = .001/.002), hydrocephalus (p value = .001/.001), trigeminal (V) nerve palsy (p value = .004/.003) and long tract signs (p value = .001/.034). Tumors crossing midline had significant association with hydrocephalus (p value = .003). LD increased progressively even for 4–5 cm-sized tumors while AD stabilized. Receiver operating characteristic (ROC) curve revealed that diagnostic accuracy of LD (area under the ROC curve (AUROC): 78.9% (95% CI: 67.2%, 90.5%, p  < .001)), AD (AUROC:77.6% (95% CI:65.8%, 89.5%, p  < .001)) and LD × AD (AUROC:80.3% (95% CI: 69.2%, 91.2%, p  < .001)) for predicting occurrence of hydrocephalus was better than tumor size (AUROC: 66.7% (95% CI: 53.5%, 79.9%, p  < .05). Cut-off values of LD and AD for predicting occurrence of hydrocephalus were 6.25 mm and 14.6°, respectively. Hydrocephalus was significantly more when both LD was greater than  6.25 mm and AD was greater than 14.5° (p value = .034). The role of LD and AD in influencing hydrocephalus was greater than categorization based on tumor size (Spearman’s correlation coefficient: 0.535 and 0.248, respectively). Hydrocephalus occurred at a lesser cut-off value of LD and AD when compared to long tract signs. Conclusions LD and AD values in VSs have a significantly greater influence in the development of hydrocephalus compared to tumor size, and may aid, more reliably, in the prediction of hydrocephalus.

Post SRS Serial Cellular Density Mapping for Response Assessment in Vestibular Schwannoma

Diffusion-weighted (DW) imaging detects cellular changes. Loss of tumor cells post radiosurgery results in alteration in the Cellular density and thus changes in apparent diffusion coefficients (ADCs). Low ADC values represent a higher tumor cellularity, a higher tumor-grade and may even be a marker for a higher tumor activity. Purpose of the study is to investigate the clinical usefulness of ADC values for evaluating VSs and to assess the correlation of DW imaging measurements with radiosurgical effects on the tumors.The authors conducted a retrospective evaluation involving 36 patients harboring solid (28 pts.) or cystic vestibular schwannomas (8 pts.) who underwent single fraction Linac based SRS. The patients underwent serial MR imaging, including DW imaging, before SRS and at 6mo. intervals thereupon following the procedure. The ADCs were calculated from echo-planar DW images, and mean ADC values were compared at each follow-up. To minimize the effect of diffusion anisotropy, an average of the values obtained for the 3 diffusion directions was calculated to provide the trace of the diffusion tensor. Data were analyzed using a t-test to compare the mean ADC values obtained before & after SRS.The mean follow-up period in this study was 32.5 months (range 16 -56 months). Imaging studies demonstrated a reduction in tumor volume in 22 patients (61.3%) and tumor growth arrest in 11 patients (33%). There was tumor enlargement at 18, 36, and 42 months in the remaining 3 patients (8.3%). The mean ADC value before SRS for all solid VSs was 1.2 ± 0.17 × 10-3 mm2/second, which significantly increased 6 months after SRS and continued to increase with time (P = 0.0076). The mean ADC value for treated solid tumors as of the last mean follow-up of 36 months (range 18-60 months) was 1.92 ± 0.26 × 10-3 mm2/second (range 1.60-2.7 × 10-3 mm2/second), which was significantly higher than that before SRS (P = 0.0001). Tumor volumes were positively related to ADC values (P = 0.03). The mean ADC value before SRS for all cystic VSs was 2.09 ± 0.24 × 10-3 mm2/second (range 1.80-2.58 × 10-3 mm2/second). The mean ADC value for treated cystic tumors as of the last mean follow-up of 38 months (range 18-48 months) was 1.9 ± 0.42 × 10-3 mm2/second. In 3 patients harboring solid VSs, the tumor enlarged after SRS but the ADC values were higher than those before SRS.ADC changes precede the real change in tumor size detected on routine follow-up MR images. ADC values of solid tumors significantly increased, even before a change in tumor volume was evident and should be incorporated in VS routine MR imaging post SRS.V. Shankar: None. V. Sai Shreya: None. R. Kumar: None. C. Haritha: None. A.K. Karthikayan: None. R. Adhityan: None. P. Bhavya: None. H. Vyas: None. A. Bhange: None.

Quantification of tumor response of cystic vestibular schwannoma to Gamma Knife radiosurgery by using artificial intelligence.

Gamma Knife radiosurgery (GKRS) is a common treatment modality for vestibular schwannoma (VS). The ability to predict treatment response is important in patient counseling and decision-making. The authors developed an algorithm that can automatically segment and differentiate cystic and solid tumor components of VS. They also investigated associations between the quantified radiological features of each component and tumor response after GKRS. This is a retrospective study comprising 323 patients with VS treated with GKRS. After preprocessing and generation of pretreatment T2-weighted (T2W)/T1-weighted with contrast (T1WC) images, the authors segmented VSs into cystic and solid components by using fuzzy C-means clustering. Quantitative radiological features of the entire tumor and its cystic and solid components were extracted. Linear regression models were implemented to correlate clinical variables and radiological features with the specific growth rate (SGR) of VS after GKRS. A multivariable linear regression model of radiological features of the entire tumor demonstrated that a higher tumor mean signal intensity (SI) on T2W/T1WC images (p < 0.001) was associated with a lower SGR after GKRS. Similarly, a multivariable linear regression model using radiological features of cystic and solid tumor components demonstrated that a higher solid component mean SI (p = 0.039) and a higher cystic component mean SI (p = 0.004) on T2W/T1WC images were associated with a lower SGR after GKRS. A larger cystic component proportion (p = 0.085) was associated with a trend toward a lower SGR after GKRS. Radiological features of VSs on pretreatment MRI that were quantified using fuzzy C-means were associated with tumor response after GKRS. Tumors with a higher tumor mean SI, a higher solid component mean SI, and a higher cystic component mean SI on T2W/T1WC images were more likely to regress in volume after GKRS. Those with a larger cystic component proportion also trended toward regression after GKRS. Further refinement of the algorithm may allow direct prediction of tumor response.

Retrosigmoid approach for giant cystic vestibular schwannoma: subperineural dissection technique for facial nerve preservation.

In this illustrative video, the authors demonstrate retrosigmoid resection of a giant cystic vestibular schwannoma using the subperineural dissection technique to preserve facial nerve function. This thin layer of perineurium arising from the vestibular nerves is used as a protective buffer to shield the facial and cochlear nerves from direct microdissection trauma. A near-total resection was achieved, and the patient had an immediate postoperative House-Brackmann grade I facial nerve function. The operative nuances and pearls of technique for safe cranial nerve and brainstem dissection, as well as the intraoperative decision and technique to leave the least amount of residual adherent tumor, are demonstrated.The video can be found here: https://stream.cadmore.media/r10.3171/2021.7.FOCVID21128

Facial Nerve Function Outcome and Risk Factors in Resection of Large Cystic Vestibular Schwannomas.

Objective  Cystic vestibular schwannomas (VS) in contrast to solid VS tend to have accelerated growth, larger volume, rapid/atypical presentation, lobulated/adherent surface, and unpredictable course of the cranial nerves. Cystic VS are surgically challenging, with worse clinical outcomes and higher rate of subtotal resection (STR). Methods  We retrospectively analyzed postoperative outcomes of 125 patients with cystic VS, operated between years 2005 and 2019 in our center. We confronted the extent of the resection and House-Brackmann (HB) grade of facial palsy with the results of comparable cohort of patients with solid VS operated in our center and literature review by Thakur et al. 1 Results  Translabyrinthine approach was preferred for resection of large, cystic VS (97.6%). Gross-total resection (GTR) was achieved in 78 patients (62.4%), near-total resection (NTR) with remnant (<4 × 4 × 2 mm) in 43 patients (34.4%), and STR in 4 patients (3.2%). NTR/STR were significantly associated with higher age, tumor volume >5 cm 3 , retrosigmoid approach, high-riding jugular bulb, tumor adherence to the brain stem, and facial nerve ( p  = 0.016; 0.003; 0.005; 0.025; 0.001; and <0.00001, respectively). One year after the surgery, 76% of patients had HB grades 1 to 2, 16% had HB grades 3 to 4, and 8% had HB grades 5 to 6 palsy. Worse outcome (HB grades 3 to 6) was associated with preoperative facial palsy, tumor volume >25 cm 3 , and cyst over the brain stem ( p  = 0.045; 0.014; and 0.05, respectively). Comparable solid VS operated in our center had significantly higher HB grades 1 to 2 rate than our cystic VS (94% versus 76%; p  = 0.03). Comparing our results with literature review, our HB grades 1 to 2 rate was significantly higher (76% versus 39%; p  = 0.0001). Tumor control rate 5 years after surgery was 95.8%. Conclusion  Our study confirmed that microsurgery of cystic VS has worse outcomes of facial nerve preservation and extent of resection compared with solid VS. Greater attention should be paid to the above-mentioned risk factors.

Outcomes of Fractionated Radiosurgery in Cystic Vestibular Schwannoma

Evaluate outcomes of fractionated SRS in predominantly cystic vestibular schwannoma. Patients undergoing fractionated Radiosurgery for VS were retrospectively reviewed. Patients with cystic tumors were considered candidates for SRS only if they did not have symptomatic or significant radiologic brainstem compression. VSs containing dominant intra-tumoral or peri-tumoral cyst(s) > 50% of the total tumor diameter by greatest linear axial CPA dimension, single or multicystic, were included for study. Pre-treatment clinical and radiographic features, including AAO-HNS hearing class, history of facial weakness, current facial and trigeminal nerve function, AAO-HNS tumor size, and intratumoral vs peritumoral cysts were captured. All Patients underwent treatment on C-Arm Linac with CBCT image guidance to a dose of 25gy/5#. Patients underwent MRI surveillance every 6 months for the first year, annually thereafter for the subsequent 2 years, and then every other year. 15 patients (12 women; median age at treatment, 53 years; range, 36-85 years) with cystic VS met inclusion criteria. The median radiologic follow-up within the cystic group was 48 months (range, 17-100 months), and the median change in tumor size was − 4.3mm. 12 tumors (80%) shrank, 2 (13%) remained stable (experienced significant cyst enlargement within 1 year after treatment, followed by spontaneous cyst shrinkage back to the original pretreatment size), and 1 patient (7%) experienced cyst enlargement of 9 mm over 21 months and underwent retrolabyrinthine subtotal tumor removal and cyst decompression enlarged. Tumor control rate in cystic group of 93%. The median radiologic follow-up in the non-cystic control group, comprising of 53 pts. was 67 months (range, 6-141 months), and the median change in size was −2.0 mm. Tumor control in the solid group was 94%. Comparing only those tumors that decreased in size showed that there was a trend toward a greater reduction within the cystic group, intratumoral being better than peri-tumoral cystic VSs (P = .05). The present study demonstrates that tumor control after fractionated SRS for dominant intratumoral cystic VS may not differ from that of noncystic VS in properly selected cases suggesting that intratumoral cysts have a different behavior compared with those with peripheral cystic components, latter may result from trapped arachnoid or a hemorrhage-related process making them, thus, more susceptible to growth despite control of the solid portion of the tumor.