Cystic vestibular schwannomas: surgical considerations and outcomes

Concurrent fibrous dysplasia is associated with a high incidence of cystic formation in vestibular schwannomas

BACKGROUND

Fibrous dysplasia (FD) is a rare hereditary bone disorder, typically accompanied by a seemingly-high percentage of cystic changes in central nerve system tumors. This study aimed to investigate the associations between concurrent FD lesions and the cystic formation of vestibular schwannoma (VS).

METHODS

Patients with VSs in our institution from January 2020 to September 2022 were retrospectively included. Based on the contrasted MRI, VSs were grouped as the cystic and solid type. Concurrent FD was diagnosed based on the radiological findings. A logistic analysis was applied to investigate the relationship between concurrent FD and cystic VSs. The effect of the interaction between gender and concurrent FD on the cystic formation of VSs was further analyzed.

RESULTS

The current study included 1255 patients with VSs (681 females with a median age of 47 years). Of them, 142 (11.3%) were with cystic VSs. A higher percentage of cystic VSs was observed in female patients (P = 0.021), patients with concurrent FDs (P < 0.001) and those with a larger VS volume (P < 0.001). An increasing trend in percentage of cystic VSs was found among patients with from 0 to ≥ 3 FD lesions (P for trend as < 0.001). A multivariate logistic analysis identified concurrent FD (odds ratio, 6.58; 95%CI, 1.66-26.09; P = 0.007) and VS volume (odds ratio, 1.55; 95%CI, 1.66-1.70; P < 0.001) as independent risk factors related to the cystic formation.

CONCLUSION

Concurrent FD is associated with a high incidence of cystic formation in VSs, which provides a new breakthrough point to investigate the underlying mechanism of cystic formation of VSs.

Comparison of Postoperative Outcomes in Cystic Versus Solid Vestibular Schwannoma in a Multi-institutional Cohort

OBJECTIVE

Cystic vestibular schwannomas (cVSs) have more variable and less favorable clinical outcomes after microsurgical resection compared with solid VS (sVS). This study compares the preoperative presentation and postoperative outcomes between cVS and sVS.

STUDY DESIGN

Retrospective cohort study.

SETTING

Two tertiary skull base referral centers.

METHODS

Consecutive adult patients who underwent VS resection from 2016 to 2021 were included. Univariate and multivariate analyses compared differences in baseline symptoms and postoperative outcomes between cVS and sVS.

RESULTS

There were a total of 315 patients (64% female; mean age, 54 yrs) and 46 (15%) were cystic. cVS were significantly larger than sVS (maximum diameter, 28 vs. 18 mm, p < 0.001) and had higher rates of dysphagia and dysphonia preoperatively (p < 0.02). cVSs were more likely to undergo translabyrinthine resection (76 vs. 50%, p = 0.001) and have a higher rate of subtotal resection (STR) compared with sVS (30 vs. 13%, p = 0.003). At latest follow-up, fewer cVS achieved good facial nerve (FN) outcome (House-Brackmann [HB] I/II) (80 vs. 90%, p = 0.048). Subanalysis of cVS and sVS matched in tumor size, and surgical approach did not show differences in the rate of STR or FN outcomes (HB I/II, 82 vs. 78%, p = 0.79).

CONCLUSION

In this large multi-institutional series, cVSs represent a distinct entity and are characterized by larger tumor size and higher incidence of atypical symptoms. Although cVSs were more likely to undergo STR and portend worse FN outcomes than sVSs, this may be due to their larger tumor size rather than the presence of the cystic component.

Cystic schwannoma of the distal forearm. Case presentation

Schwannomas are well-encapsulated, benign tumors arising from Schwann cell constituting the nerve sheaths. We report a case of a cystic conventional schwannoma, measuring 2.5×3 cm, located in the distal forearm of a 33-year-old female patient with no sign of neurofibromatosis type 2 or type 3. The mass was painless, but Tinel’s sign was positive. Ultrasonography showed a soft tissue cystic mass diagnosed as being synovial cyst in the left distal forearm. Surgical resection was performed without any complications. Histopathological examinations oriented the diagnosis to a schwannoma, but immunohistochemical stainings proved the tumor origin in Schwann cells and made the differential diagnosis with other pathologies, like neurofibroma, leiomyoma, epithelial cyst, synovial cyst, or ganglion cyst.

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.

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.

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.

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.