Salvage radiosurgery following subtotal resection of vestibular schwannomas: does timing influence tumor control?

A morphological features-based nomogram for predicting facial nerve function in the immediate postoperative period after vestibular schwannoma surgery

PURPOSE

Tumor morphology critically influences facial nerve (FN) outcomes following vestibular schwannoma (VS) surgery. This study aimed to develop a nomogram based on preoperative features for preoperative prediction of FN outcomes after VS surgery.

METHODS

A retrospective analysis included patients with sporadic VS who underwent surgical resection via the retrosigmoid approach. Tumor size was assessed using the Koos grade, the intrameatal components using the fundal fluid cap (FFC) sign, and the cerebellopontine angle cisternal components using our modified morphological subclassification. Logistic regression analysis was performed to construct a nomogram for predicting immediate postoperative FN function.

RESULTS

A total of 265 patients with VS met the inclusion criteria. Of these patients, 62 (23.4%) had poor FN function (House-Brackmann grade ≥ III) immediately after surgery. Univariate logistic regression analysis identified the Koos grade (p = 0.001), FFC sign (p = 0.023), and morphological subtype (p < 0.001) as significant predictors of poor FN function immediately after surgery. In multivariate logistic regression analysis, the FFC sign (OR 2.07, p = 0.042) and morphological subtype (OR 8.21, p < 0.001) remained statistically significant independent predictors of poor FN function. A nomogram constructed based on these indicators demonstrated good discrimination in the training cohort (area under the curve [AUC] 0.80), internal validation cohort (AUC 0.79), and external validation cohort (AUC 0.97).

CONCLUSIONS

A simple and reliable nomogram incorporating the Koos grade, FFC sign, and morphological subtype accurately predicts the risk of FN injury during surgery aimed at total resection of VS. This clinically straightforward tool can assist in patient counseling and development of more individualized surgical strategies to improve FN outcomes in patients with VS.

Residual Vestibular Schwannomas: Proposed Age-Tumor-Residual (ATR) Staging System to Predict Future Growth

OBJECTIVE

To assess growth rates of residual vestibular schwannoma after subtotal and near-total surgical resection and establishing staging system for risk of residual tumor growth.

STUDY DESIGN

Retrospective cohort study.

SETTING

Tertiary referral center.

PATIENTS

Patients with residual vestibular schwannoma after surgical resection from 2011 to 2023 identified on postoperative MRI defined as near-total resection (NTR, less than 5 mm of remaining tumor), subtotal resection (STR; 5-10 mm) and debulking (>10 mm).

MAIN OUTCOME MEASURES

Tumor growth of 2 mm or more after subtotal or near-total surgical resection of vestibular schwannoma.

RESULTS

A total of 56 patients (54% female; mean, standard deviation [SD] age 51 [17] yr) had residual tumor. Mean preoperative tumor size was 3.0 (1.1) cm, and residual tumors involved both sides with similar frequency (right: 52%). Quantitatively, 29% were NTR, 32% were STR, and 39% were debulking. With an average follow-up of 27 (SD 31) months, tumor growth occurred in 11 (20%), tumor shrinkage occurred in 16 (29%), and tumors were unchanged in 29 (51%) cases. Growing residual tumors were treated with radiation (7 patients) or a second surgical resection (4 patients). Multivariable analysis identified lower patient age, larger preoperative tumor size, and larger residual tumor size in risk of residual growth. A residual VS tumor staging system (Age, Tumor, Residual [ATR]) is proposed with most tumors in stage II (22, 42%) or stage III (23, 44%), whereas 7 (14%) tumors are stage I.

CONCLUSIONS

Approximately 80% of residual VS are stable or shrink in size. Initial observation is advocated after incomplete resection and long-term follow up is needed. Patient age less than 55 years, larger preoperative tumor size, and larger postoperative residual tumor size appear predictive of residual tumor growth.Level of Evidence: 4.

[Our approach to the treatment of vestibular schwannomas with arachnoid dissection of the facial nerve]

Preserving the function of the facial nerve is extremely important in surgery for vestibular schwannomas. Two methods of arachnoid dissection are described for resection of vestibular schwannoma via retrosigmoid approach (from the brain stem and internal auditory canal).

OBJECTIVE

To evaluate the results of arachnoid dissection of the facial nerve from internal auditory canal when resecting the vestibular schwannoma.

MATERIAL AND METHODS

We analyzed 61 patients with vestibular schwannomas. Patients were divided into 2 groups depending on surgical technique. We estimated facial nerve function before and after surgery, preoperative dimension of vestibular schwannoma and extent of resection. The influence of various factors on extent of resection and postoperative facial nerve function was studied.

RESULTS

Vestibular schwannoma resection from the brain stem was performed in 30 patients, arachnoid dissection - in 31 patients. There was no significant between-group difference. Gross total resection was performed in 78.7% of cases. Both techniques demonstrated similar results regarding extent of resection. Arachnoid dissection showed the advantage regarding facial nerve function immediately after surgery (p=0.012) and 6 months later (p<0.001). Normal facial nerve function in 6 months after arachnoid dissection was observed in 80.7% of patients. Preoperative dimension of tumor influenced facial nerve function in addition to technique of resection (p=0.001).

CONCLUSION

We identified the factors influencing facial nerve function after resection of vestibular schwannoma. Surgical technique was the most significant factor. These data expand and popularize arachnoid dissection in surgery of vestibular schwannomas.

Repeat Surgery for Vestibular Schwannomas: An Institutional Case Series

Introduction  Vestibular schwannomas (VSs) are treated with microsurgery and/or radiosurgery. Repeat resection is rare, and few studies have reported postoperative outcomes. The objective of this study was to describe clinical characteristics and outcomes in patients undergoing repeat surgery for VS. Methods  All adult (≥ 18 years) patients undergoing VS resection between 2003 and 2022 at our institution were retrospectively reviewed to identify patients who underwent repeat surgery of an ipsilateral VS following prior gross-total (GTR) or subtotal resection. Patient, radiographic, and clinical characteristics were reviewed. Primary outcomes were postoperative tumor volume, extent of resection, postoperative cranial nerve deficits, and time to further tumor progression. Results  Of 102 patients undergoing VS resection, 6 (5.9%) had undergone repeat surgery. Median (range) follow-up was 20 (5-117) months. Three patients were female. Median age was 56 (36-60) years. Median pre- and postoperative tumor volumes were 8.2 (1.8-28.2) cm 3 and 0.4 (0-3.8) cm 3 . GTR was achieved in two patients. Four patients had higher House-Brackmann scores at last follow-up, but none had tumor progression. Conclusion  In this small cohort of patients, repeat resection of recurrent or progressive VS can effectively reduce tumor volume with acceptable perioperative outcomes.

Outcomes following surgical resection of trigeminal schwannomas: a systematic review and meta-analysis

Although typically benign, trigeminal schwannomas (TS) may require surgical resection when large or symptomatic and can cause significant morbidity. This study aims to summarize the literature and synthesize outcomes following surgical resection of TS. A systematic review was performed according to PRISMA guidelines. Data extracted included patient and tumor characteristics, surgical approaches, and postoperative outcomes. Odds ratios (OR) with corresponding 95% confidence intervals (CI) were used for outcome analysis. The initial search yielded 1838 results, of which 26 studies with 974 patients undergoing surgical resection of TS were included. The mean age was 42.9 years and 58.0% were female. The mean tumor diameter was 4.7 cm, with Samii type A, B, C, and D tumors corresponding to 33.4%, 15.8%, 37.2%, and 13.6%, respectively. Over a mean symptom duration of 29 months, patients presented with trigeminal hypesthesia (58.7%), headache (32.8%), trigeminal motor weakness (22.8%), facial pain (21.3%), ataxia (19.4%), diplopia (18.7%), and visual impairment (12.0%). Surgical approaches included supratentorial (61.4%), infratentorial (15.0%), endoscopic (8.6%), combined/staged (5.3%), and anterior (5.7%) or posterior (4.0%) petrosectomy. Postoperative improvement of facial pain (83.9%) was significantly greater than trigeminal motor weakness (33.0%) or hypesthesia (29.4%). The extent of resection (EOR) was reported as gross total (GTR), near total, and subtotal in 77.7%, 7.7%, and 14.6% of cases, respectively. Over a mean follow-up time of 62.6 months, recurrence/progression was noted in 7.4% of patients at a mean time to recurrence of 44.9 months. Patients with GTR had statistically significantly lower odds of recurrence/progression (OR: 0.07; 95% CI: 0.04-0.15) compared to patients with non-GTR. This systematic review and meta-analysis report patient outcomes following surgical resection of TS. EOR was found to be an important predictor of the risk of recurrence. Facial pain was more likely to improve postoperatively than facial hypesthesia. This work reports baseline rates of post-operative complications across studies, establishing benchmarks for neurosurgeons innovating and working to improve surgical outcomes for TS patients.

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.