The Peculiar Cystic Vestibular Schwannoma: A Single-Center Experience

Cystic vestibular schwannoma - a subgroup analysis from a comparative study between radiosurgery and microsurgery

Some vestibular schwannoma (VS) show cystic morphology. It is known that these cystic VS bear different risk profiles compared to solid VS in surgical treatment. Still, there has not been a direct comparative study comparing both SRS and SURGERY effectiveness in cystic VS. This retrospective bi-center cohort study aims to analyze the management of cystic VS compared to solid VS in a dual center study with both microsurgery (SURGERY) and stereotactic radiosurgery (SRS). Cystic morphology was defined as presence of any T2-hyperintense and Gadolinium-contrast-negative cyst of any size in the pre-interventional MRI. A matched subgroup analysis was carried out by determining a subgroup of matched SURGERY-treated solid VS and SRS-treated solid VS. Functional status, and post-interventional tumor volume size was then compared. From 2005 to 2011, N = 901 patients with primary and solitary VS were treated in both study sites. Of these, 6% showed cystic morphology. The incidence of cystic VS increased with tumor size: 1.75% in Koos I, 4.07% in Koos II, 4.84% in Koos III, and the highest incidence with 15.43% in Koos IV. Shunt-Dependency was significantly more often in cystic VS compared to solid VS (p = 0.024) and patients with cystic VS presented with significantly worse Charlson Comorbidity Index (CCI) compared to solid VS (p < 0.001). The rate of GTR was 87% in cystic VS and therefore significantly lower, compared to 96% in solid VS (p = 0.037). The incidence of dynamic volume change (decrease and increase) after SRS was significantly more common in cystic VS compared to the matched solid VS (p = 0.042). The incidence of tumor progression with SRS in cystic VS was 25%. When comparing EOR in the SURGERY-treated cystic to solid VS, the rate for tumor recurrence was significantly lower in GTR with 4% compared to STR with 50% (p = 0.042). Tumor control in cystic VS is superior in SURGERY, when treated with a high extent of resection grade, compared to SRS. Therapeutic response of SRS was worse in cystic compared to solid VS. However, when cystic VS was treated surgically, the rate of GTR is lower compared to the overall, and solid VS cohort. The significantly higher number of patients with relevant post-operative facial palsy in cystic VS is accredited to the increased tumor size not its sole cystic morphology. Cystic VS should be surgically treated in specialized centers.

Vestibular schwannoma with fluid-fluid levels mimicking aneurysm bone cyst

Of 6%-8%, cerebral tumors are intracranial schwannomas, also known as neurinomas, which frequently arise from the nerve sheath. Eighth cranial nerve (CN VIII), also known as the vestibulocochlear nerve, is the site of genesis of the majority of schwannomas, which account for 80%-90% of cerebellopontine angle tumors. In this paper, we intended to describe an uncommon cystic vestibular schwannoma with multiple fluid-fluid levels. Surgical excision was performed using the translabyrinthine approach. The report highlights schwannomas' adherence to and invasion of adjacent anatomical structures. We discuss a number of differential diagnoses, the pathophysiology of fluid-fluid levels, and the imaging features of cystic vestibular schwannomas.

Management and outcome of unusual pediatric brain tumors: challenges experienced at a tertiary care center of a developing country

PURPOSE

Primary brain tumors are the most frequent solid pediatric tumors, accounting for 40-50% of all cancers in children. Eighty to ninety percent of the 250,000 new cases of pediatric cancer each year are discovered in low and middle-income nations, where nearly 88 percent of the world's children reside. This article aims to emphasize the unusual presentation, management, and surgical outcome of complex pediatric brain tumors.

METHODS

We performed a retrospective study of patients who were admitted to the neurosurgery department with unusual pediatric brain tumors between March 1, 2019, and March 1, 2022. The study included pediatric patients up to age 18 years. We included those pediatric brain tumors whose (i) location was uncommon, or (ii) presented with unusual clinical presentation, or (iii) histopathology suggested to be a rare tumor, or (iv) radiological features were atypical.

RESULTS

We included 9 cases of rare unusual pediatric brain tumors. Three out of 9 cases required preoperative embolization due to its hypervascular nature on digital subtraction angiography (DSA). All patients underwent surgical excision within 24-48 h of tumor devascularization. One out of 9 cases died in follow-up period due to pleural effusion and distant metastasis to lungs.

CONCLUSION

Treatment considerations for unusual pediatric brain tumors include a comprehensive multidisciplinary approach, including community-based screening and proper referral system for early treatment, a variety of treatment modalities, and sophisticated follow-up strategy. Government shall work in coherence with tertiary centers to spread social awareness and provide various financial scheme to prevent treatment dropouts.

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 < 24 months 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 12 months (range, 1-147 months). At GKRS, the median cVS volume was 6.95 cm3 (range, 4.1-22 cm3). The median marginal dose was 12 Gy (range, 10-12 Gy). The mean radiological and clinical follow-up periods were 62.2 ± 34.04 months (range, 24-169 months) and 94.9 ± 45.41 months (range, 24-175 months), respectively. At 2, 6, and 12 years, 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 53.5 months, 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

OBJECTIVE

To determine the natural history of cystic vestibular schwannomas (VS).

STUDY DESIGN

Retrospective cohort.

SETTING

Single tertiary academic hospital.

PATIENTS

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.

MAIN OUTCOME MEASURES

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).

RESULTS

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.

CONCLUSIONS

Cystic tumors demonstrate a wide variability in growth rate. Larger, multi-center studies will be required to further compare this relationship to solid tumors.

Comparison of surgical outcomes in cystic and solid vestibular schwannomas: a systematic review and meta-analysis

Most studies reported that cystic vestibular schwannoma (CVS) surgery has a less favourable prognosis than solid vestibular schwannoma (SVS) surgery. However, some studies report that it is unclear whether surgical outcomes for these conditions exhibit significant differences. The aim of this meta-analysis was to pool the current literature and describe and analyse any differences in the clinical symptoms and surgical outcomes among CVS and SVS. PubMed, Embase, and Cochrane databases were searched following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines through April 22, 2020. Outcomes were analysed using a meta-analysis of the proportions. The results of the search yielded 17 studies that met the criteria for inclusion and analysis, involving 3074 participants (including 821 patients with CVSs and 2253 patients with SVSs). No significant differences in the extent of tumour resection (gross-total resection versus non-gross-total resection; RR, 0.93; 95% CI, 0.86-1.01; p = 0.096) and most other outcomes were noted between CVS and SVS cohorts. However, facial nerve function (House-Brackmann Grade I or II versus III or more) of CVS patients was worse (RR, 0.86; 95% CI, 0.78-0.93; p < 0.001) compared with SVS patients with more than 1 year of follow-up after surgery. The criteria of cystic acoustic neuroma needs to be further unified, and prospective cohort studies with larger sample sizes should be performed for further verification of these results in the future.

Equivalent Efficacy and Safety of Radiosurgery for Cystic and Solid Vestibular Schwannomas: A Systematic Review

BACKGROUND

Cystic vestibular schwannomas (VS) are associated with unpredictable growth behavior and potentially worse surgical outcomes compared with their solid counterparts. Growth control and potential adverse effects of radiosurgery for cystic VS have created concerns surrounding this modality. We sought to compare the treatment efficacy and safety profile of radiosurgery between cystic and solid VS through a systematic review.

METHODS

PubMed, EMBASE, Web of Science, and Cochrane were searched for related terms and studies reporting radiosurgical outcomes of cystic and solid VS. A meta-analysis was performed to compare the rates of tumor control. Random-effect models with generic inverse variance method was used to calculate overall pooled estimates. Study quality was assessed with the Newcastle Ottawa Criteria.

RESULTS

In total, 2989 studies were retrieved, and 6 including 1358 VS (79.89% solid; 20.11% cystic, median follow-up range 31.8-150 months) were selected. The median maximal dose was 25 Gy (range, 13-36 Gy) and the median marginal tumor dose was 12 Gy (10-18 Gy). There was no difference between cystic and solid VS (risk ratio, 1.02; 95% confidence interval 0.94-1.10; P = 0.69; I2 = 78%). Transient enlargement of cystic tumors may be associated with trigeminal or facial neuropathy.

CONCLUSIONS

The evidence collected by this study suggests that radiosurgery for cystic VS exhibits effective tumor control probabilities similar to solid VS. Consensus definitions and standard criteria are needed in the future to better understand the patterns of tumor growth and response to treatment following radiosurgery for cystic VS, as well as long-term neurological and functional outcomes.

Comparison of Surgical Outcomes and Recurrence Rates of Cystic and Solid Vestibular Schwannomas

Objective  Cystic vestibular schwannomas (CVSs) are anecdotally believed to have worse clinical and tumor-control outcomes than solid vestibular schwannomas (SVSs); however, no data have been reported to support this belief. In this study, we characterize the clinical outcomes of patients with CVSs versus those with SVSs. Design  This is a retrospective review of prospectively collected data. Setting  This study is set at single high-volume neurosurgical institute. Participants  We queried a database for details on all patients diagnosed with vestibular schwannomas between January 2009 and January 2014. Main Outcome Measures  Records were retrospectively reviewed and analyzed using univariate and multivariate analyses to study the differences in clinical outcomes and tumor progression or recurrence. Results  Of a total of 112 tumors, 24% ( n  = 27) were CVSs and 76% ( n  = 85) were SVSs. Univariate analysis identified the extent of resection, Koos grade, and tumor diameter as significant predictors of recurrence ( p  ≤ 0.005). However, tumor diameter was the only significant predictor of recurrence in the multivariate analysis ( p  = 0.007). Cystic change was not a predictor of recurrence in the univariate or multivariate analysis ( p  ≥ 0.40). Postoperative facial nerve and hearing outcomes were similar for both CVSs and SVSs ( p  ≥ 0.47). Conclusion  Postoperative facial nerve outcome, hearing, tumor progression, and recurrence are similar for patients with CVSs and SVSs. As CVS growth patterns and responses to radiation are unpredictable, we favor microsurgical resection over radiosurgery as the initial treatment. Our data do not support the commonly held belief that cystic tumors behave more aggressively than solid tumors or are associated with increased postoperative facial nerve deficits.

Facial nerve outcome and extent of resection in cystic versus solid vestibular schwannomas in radiosurgery era

OBJECTIVE Cystic vestibular schwannomas (CVSs) are a subgroup of vestibular schwannomas (VSs) that are reported to be associated with unpredictable clinical behavior and unfavorable postoperative outcomes. The authors aimed to review their experience with microsurgical treatment of CVSs in terms of extent of resection and postoperative facial nerve (FN) function and compare these outcomes with those of their solid counterparts. METHODS Two hundred-eleven VS patients were treated surgically between 2006 and 2017. Tumors were defined as cystic when preoperative neuroimaging demonstrated cyst formation that was confirmed by intraoperative findings. Solid VS (SVSs) with similar classes were used for comparison. Clinical data of the patients were reviewed retrospectively, including clinical notes and images, as well as operative, pathology, and neuroradiology reports. RESULTS Thirty-two patients (20 males and 12 females) with a mean age of 52.2 years (range 17-77 years) underwent microsurgical resection of 33 CVSs (mean size 3.6 cm, range 1.5-5 cm). Forty-nine patients (26 males and 23 females) with a mean age of 49.9 years (range 21-75 years) underwent microsurgical resection of 49 SVSs (mean size 3 cm, range 2-4.5 cm). All operations were performed via either a retrosigmoid or a translabyrinthine approach. Gross-total resection was achieved in 30 cases in the CVS group (90.9%) and 37 in the SVS group (75.5%). The main reason for subtotal and near-total resection was adherence of the tumor to the brainstem and/or FN in both groups. None of the patients with subtotal or near-total resection in the CVS group demonstrated symptomatic regrowth of the tumor during the mean follow-up period of 41.6 months (range 18-82 months). The FN was anatomically preserved in all patients in both groups. Good FN outcomes were achieved in 15 of CVS (grade I-II; 45.5%) and 35 of SVS (71.4%) surgeries at discharge. Good and fair FN functions were noted in 22 (grade I-II; 81.5%) and 5 (grade III only; 18.5%) of the CVS patients, respectively, at the 1-year follow-up; none of the patients showed poor FN function. CONCLUSIONS Surgery of CVSs does not necessarily result in poor outcomes in terms of the extent of resection and FN function. Special care should be exercised to preserve anatomical continuity of the FN during surgery, since long-term FN function outcomes are much more satisfactory than short-term results. High rates of gross-total resection and good FN outcomes in our study may also suggest that microsurgery stands as the treatment of choice in select cases of large CVSs and SVSs in the era of radiosurgery.

Comparison of Clinical Characteristics and Surgical Outcomes of Cystic and Solid Vestibular Schwannomas

OBJECTIVE

The aim of this study was to compare the clinical characteristics of cystic vestibular schwannomas (CVSs) and solid vestibular schwannomas (SVSs).

STUDY DESIGN

Retrospective review.

SETTING

Tertiary care center.

PATIENTS

A total of 220 patients who underwent microsurgery for vestibular schwannomas between 2007 and 2016.

INTERVENTION

CVSs were defined as cystic components ≥1/3 of total tumor volume based on automated volume measurement. Tumors larger than 5 cm were defined as large tumors.

MAIN OUTCOME MEASURES

Clinical characteristics and surgical outcomes, including preoperative symptoms, hearing threshold, vestibular function, tumor volume, extent of resection, facial nerve outcomes, and nonfacial complications were evaluated.

RESULTS

Tumor volume was significantly larger in CVSs (20.44 ± 13.85 cm in CVSs; 4.75 ± 6.48 cm in SVSs, p < 0.001) and the proportion of larger tumors was also greater in CVSs (66.0% in CVSs; 11.4% in SVSs, p < 0.001). Preoperative dizziness was highly prevalent in CVSs (32.1% in CVSs; 18.6% in SVSs, p = 0.038) and postoperative facial nerve outcomes were significantly worse in CVSs (67.9% favorable rate in CVSs; 87.4% favorable rate in SVSs, p = 0.001). When the comparison was limited to large tumors, no clinical characteristics or surgical outcomes were significantly different. Tumor volume had a greater effect than tumor type on the surgical outcomes. The odds ratios for subtotal resection and unfavorable facial nerve function with a large tumor were 5.77 (confidence interval [CI]: 1.52-21.95, p = 0.010) and 5.34 (CI: 1.41-20.22, p = 0.014), respectively.

CONCLUSION

CVSs tend to be larger than SVSs. Tumor volume, not cystic component, is thought to be a major determinant of surgical outcomes.

Efficacy of cyst-cisternal shunt for refractory cyst regrowth of cystic vestibular schwannomas

Vestibular schwannomas (VSs) are generally benign and slow-growing tumors, and microsurgical resection is the commonly recommended treatment. Some reports suggested that inserting a cystoperitoneal shunt was effective for treatment of cystic VSs; however, there was no report of a cyst-cisternal shunt which diverts cyst fluid into cistern. We report a case of cystic VS with repeated cyst regrowth within weeks after repeated surgeries. We prevented further recurrence using cyst-cisternal shunt. This technique may be a new treatment option for refractory cyst regrowth of cystic VSs.

Acute Presentation of Vestibular Schwannoma Secondary to Intratumoral Hemorrhage: A Case Report and Literature Review

BACKGROUND

Vestibular schwannomas (VS) are common slow-growing tumors that typically present with the insidious progression of unilateral hearing loss, tinnitus, vertigo, and gait imbalance. Clinically significant intratumoral acute hemorrhage is exceedingly rare and can present with the acute onset of symptoms, neurologic deterioration, and significant dysfunction of cranial nerves VII and VIII. We discuss a 40-year-old man who developed mild hearing loss and headaches over the course of a month before presenting with a large acutely hemorrhagic vestibular schwannoma. In addition, we review the current literature pertaining to this pathology.

CASE PRESENTATION

A previously healthy 40-year-old man with a 1-month history of mild headaches, dizziness, and left-sided hearing loss, tinnitus, and facial numbness presented with the acute onset of severe headache, vomiting, complete left-sided hearing loss, and left-sided facial weakness. Computed tomography and magnetic resonance imaging revealed a 4.1 × 2.7 cm hemorrhagic mass in the left cerebellopontine angle most consistent with VS. The patient subsequently underwent a retrosigmoid craniotomy and resection of the tumor. Pathology was consistent with hemorrhagic VS. Imaging at 1-year follow-up demonstrated no residual or recurrent disease, and facial motor function had completely recovered.

CONCLUSIONS

Histologically, vascular abnormalities and microhemorrhages are nearly ubiquitous across vestibular schwannomas and may contribute to cystic degeneration and rapid tumor growth. However, clinically significant hemorrhage is rarely encountered and is more commonly associated with more profound neurologic sequelae and cranial nerve VII dysfunction. Surgical resection at the time of presentation should be strongly considered to remove the risk of repeat hemorrhage and further deterioration. Our case represents a typical presentation and clinical course for a patient presenting with this rarely encountered pathology.

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.

Diagnostics and therapy of vestibular schwannomas - an interdisciplinary challenge

Vestibular schwannomas (VS) expand slowly in the internal auditory canal, in the cerebellopontine angle, inside the cochlear and the labyrinth. Larger tumors can displace and compress the brainstem. With an annual incidence of 1:100,000 vestibular schwannoma represent 6-7% of all intracranial tumors. In the cerebellopontine angle they are by far the most neoplasm with 90% of all lesions located in this region. Magnetic resonance imaging (MRI), audiometry, and vestibular diagnostics are the mainstays of the clinical workup for patients harboring tumors. The first part of this paper delivers an overview of tumor stages, the most common grading scales for facial nerve function and hearing as well as a short introduction to the examination of vestibular function. Upholding or improving quality of life is the central concern in counseling and treating a patient with vestibular schwannoma. Preservation of neuronal function is essential and the management options - watchful waiting, microsurgery and stereotactic radiation - should be custom-tailored to the individual situation of the patient. Continuing interdisciplinary exchange is important to monitor treatment quality and to improve treatment results. Recently, several articles and reviews have been published on the topic of vestibular schwannoma. On the occasion of the 88^th annual meeting of the German Society of Oto-Rhino-Laryngology, Head and Neck surgery a special volume of the journal "HNO" will be printed. Hence this presentation has been designed to deviate from the traditional standard which commonly consists of a pure literature review. The current paper was conceptually woven around a series of interdisciplinary cases that outline examples for every stage of the disease that show characteristic results for management options to date. Systematic clinical decision pathways have been deduced from our experience and from results reported in the literature. These pathways are graphically outlined after the case presentations. Important criteria for decision making are size and growth rate of the tumor, hearing of the patient and the probability of total tumor resection with preservation of hearing and facial nerve function, age and comorbidity of the patient, best possible control of vertigo and tinnitus and last but not least the patient's preference and choice. In addition to this, the experience and the results of a given center with each treatment modality will figure in the decision making process. We will discuss findings that are reported in the literature regarding facial nerve function, hearing, vertigo, tinnitus, and headache and reflect on recent studies on their influence on the patient's quality of life. Vertigo plays an essential role in this framework since it is an independent predictor of quality of life and a patient's dependence on social welfare. Pathognomonic bilateral vestibular schwannomas that occur in patients suffering from neurofibromatosis typ-2 (NF2) differ from spontaneous unilateral tumors in their biologic behavior. Treatment of neurofibromatosis type-2 patients requires a multidisciplinary team, especially because of the multitude of separate intracranial and spinal lesions. Off-label chemotherapy with Bevacizumab can stabilize tumor size of vestibular schwannomas and even improve hearing over longer periods of time. Hearing rehabilitation in NF2 patients can be achieved with cochlear and auditory brainstem implants.

Magnetic resonance imaging characteristics and the prediction of outcome of vestibular schwannomas following Gamma Knife radiosurgery

OBJECTIVE

Gamma Knife surgery (GKS) is a promising treatment modality for patients with vestibular schwannomas (VSs), but a small percentage of patients have persistent postradiosurgical tumor growth. The aim of this study was to determine the clinical and quantitative MRI features of VS as predictors of long-term tumor control after GKS.

METHODS

The authors performed a retrospective study of all patients with VS treated with GKS using the Leksell Gamma Knife Unit between 2005 and 2013 at their institution. A total of 187 patients who had a minimum of 24 months of clinical and radiological assessment after radiosurgery were included in this study. Those who underwent a craniotomy with tumor removal before and after GKS were excluded. Study patients comprised 85 (45.5%) males and 102 (54.5%) females, with a median age of 52.2 years (range 20.4–82.3 years). Tumor volumes, enhancing patterns, and apparent diffusion coefficient (ADC) values were measured by region of interest (ROI) analysis of the whole tumor by serial MRI before and after GKS.

RESULTS

The median follow-up period was 60.8 months (range 24–128.9 months), and the median treated tumor volume was 3.54 cm3 (0.1–16.2 cm3). At last follow-up, imaging studies indicated that 150 tumors (80.2%) showed decreased tumor volume, 20 (10.7%) had stabilized, and 17 (9.1%) continued to grow following radiosurgery. The postradiosurgical outcome was not significantly correlated with pretreatment volumes or postradiosurgical enhancing patterns. Tumors that showed regression within the initial 12 months following radiosurgery were more likely to have a larger volume reduction ratio at last follow-up than those that did not (volume reduction ratio 55% vs 23.6%, respectively; p < 0.001). Compared with solid VSs, cystic VSs were more likely to regress or stabilize in the initial postradiosurgical 6–12-month period and during extended follow-up. Cystic VSs exhibited a greater volume reduction ratio at last follow-up (cystic vs solid: 67.6% ± 24.1% vs 31.8% ± 51.9%; p < 0.001). The mean preradiosurgical maximum ADC (ADCmax) values of all VSs were significantly higher for those with tumor regression or stabilization at last follow-up compared with those with progression (2.391 vs 1.826 × 10−3 mm2/sec; p = 0.010).

CONCLUSIONS

Loss of central enhancement after radiosurgery was a common phenomenon, but it did not correlate with tumor volume outcome. Preradiosurgical MRI features including cystic components and ADCmax values can be helpful as predictors of treatment outcome.

Stereotactic Radiosurgery for Cystic Vestibular Schwannomas

BACKGROUND

The optimum treatment for cystic vestibular schwannoma (VS) remains controversial. Anecdotally, many treating physicians feel that cystic VSs do not respond to stereotactic radiosurgery (SRS) as well as noncystic tumors.

OBJECTIVE

To present outcomes after treatment of predominantly cystic VS with SRS.

METHODS

A prospectively maintained clinical database of patients undergoing Gamma Knife (Elekta Instruments, Stockholm, Sweden) radiosurgery (GKRS) for VS at a single tertiary academic referral center was retrospectively reviewed. Patients diagnosed with cystic VS who were treated with GKRS between 1997 and 2014 were analyzed. Size-matched solid tumors treated with GKRS during this period were selected as controls.

RESULTS

Twenty patients (12 women; median age at treatment, 56 years; range, 36-85 years) with cystic VS met inclusion criteria. The median radiologic follow-up within the cystic group was 63 months (range, 17-201 months), and the median change in tumor size was -4.9 mm (range, -10.4 to 9.3 mm). Sixteen tumors (80%) shrank, 2 (10%) remained stable, and 2 (10%) enlarged, accounting for a tumor control rate of 90%. The median radiologic follow-up in the noncystic control group was 67 months (range, 6-141 months), and the median change in size was -2.0 mm (range, -10.4 to 2.5 mm). Tumor control in the solid group was 90%. Comparing only those tumors that decreased in size showed that there was a trend toward a greater reduction within the cystic group ( P = .05).

CONCLUSION

The present study demonstrates that tumor control after SRS for cystic VS may not differ from that of noncystic VS in selected cases.

Clinical comparison of two subtypes of cystic vestibular schwannoma: surgical considerations and outcomes

Cystic vestibular schwannoma (CVS) is classified as Type A and Type B based on the overall cyst location and cyst wall thickness in magnetic resonance imaging. A retrospective analysis was performed to compare surgical considerations and outcomes between Type A and Type B groups of CVS. We selected 188 patients diagnostic for CVS with surgical resection, and divided them into Type A and Type B groups. General information, preoperative symptoms, the result of neuroimaging, and audiological tests were recorded. Surgical approach, completeness of tumor resection, and intraoperative facial nerve (FN) integrity were taken down. After operation, the short-term and long-term FN functions, complications, and recurrence rate were evaluated. The total tumor removal rate in Type A group was higher than that in Type B group (86.1 vs 72.5 %, p = 0.021). Anatomical FN integrity was preserved in 173 patients (92.0 %), with no significant differences between Type A and Type B. FN function was better in Type A group at hospital discharge. Besides, a good FN function rate was inversely proportional to the tumor size. The long-term FN function and all of the complications had no significant differences between the two groups. Patients in the Type B group are prone to have a lower total tumor removal rate and transient FN dysfunction. The long-term FN function was similar in both groups. Tumor size is another important indication of FN function. All postoperative complications occurred in patients with a tumor larger than grade 3, regardless of the subtypes of CVS.