2026 Proffered Presentations
S195: PROGNOSTIC SIGNIFICANCE OF CYSTIC MORPHOLOGY IN VESTIBULAR SCHWANNOMAS: A MULTI-INSTITUTIONAL RETROSPECTIVE ANALYSIS OF A LARGE COHORT FROM 1990 TO 2025
Kaasinath Balagurunath, BA1; Sabrina Heman-Ackah, MD, DPhil, Oxon, MSE1; Rania A Mekary, PhD, MSc, MS2; C. Eduardo Corrales, MD, Co Senior Author1; Timothy Smith, MD, PhD, MPH, Co Senior Author1; 1Brigham and Women's Hospital; 2School of Pharmacy, Massachusetts College of Pharmacy and Health Sciences (MCPHS) University
Introduction: Cystic vestibular schwannomas (VS) represent a less common tumor subtype with distinct radiographic features and uncertain prognostic impact compared to solid tumors. Leveraging a large multi-institutional cohort, this study provides a comprehensive evaluation of cystic morphology’s influence on surgical outcomes and complications over a 35-year period.
Objectives: To compare demographic, clinical, operative, and postoperative characteristics between cystic and non-cystic VS across three large tertiary referral centers in New England and to assess the independent prognostic value of cystic morphology on functional outcomes and tumor recurrence.
Methods: This retrospective cohort study included 2,139 patients who underwent VS resection between 1990 and 2025. Tumors were categorized as non-cystic (n=1,968) or cystic (n=171), if at least two separate radiology reports confirmed it. Data collected encompassed baseline demographics, lesion characteristics, surgical approach, laboratory values, and postoperative outcomes. Functional status was assessed via modified Rankin Scale (mRS), Glasgow Outcome Scale Extended (GOSE), and Barthel Index. Logistic regression was utilized to evaluate prognostic associations while accounting for key confounders: age, GTR, lesion size, operative approach, BMI, tobacco use, cystic changes, nutrition status, HRJB. To mitigate inflated type I error associated with multiple testing, t-tests and chi-square analyses were not performed.
Results: Patients with cystic VS were older (mean age 52.1 ± 17.1 years) compared to those with non-cystic tumors (49.4 ± 12.8 years). Cystic tumors were significantly larger, averaging 25.8 ± 9.0 mm versus 22.3 ± 10.4 mm in non-cystic VS. Smoking history was more prevalent in the cystic group (28.1% vs. 19.5%). Surgical management predominantly utilized the retrosigmoid approach in both groups; however, cystic tumors had notably lower rates of gross-total-resection (GTR) (45.9%) compared to non-cystic tumors (78.7%). Subtotal resection was consequently more common in cystic lesions (54.1% vs. 21.3%).
Postoperative complication rates were markedly elevated in the cystic cohort. Hydrocephalus occurred in 27.5% of cystic cases, more than double the 12.4% incidence seen in non-cystic patients. Peri-tumoral radiographic changes (diffusion restriction, T2 hyperintensity, parenchymal shrinkage, or encephalomalacia) were also significantly more frequent in cystic VS (48.5% vs. 21.9%), suggesting increased perioperative vulnerability. Radiographic tumor recurrence was nearly twice as common in cystic tumors (19.3%) compared to non-cystic counterparts (9.8%), highlighting a potential challenge in achieving durable tumor control.
Despite these differences, multivariate logistic regression adjusting for confounders revealed no statistically significant independent association between cystic morphology and adverse functional outcomes as measured by mRS, GOSE, and Barthel Index scores (OR 0.802, 95% CI 0.365–1.766, p=0.584). Similarly, cystic tumors were not predictive of hydrocephalus (OR 0.864, p=0.733), tumor recurrence (OR 1.578, p=0.362), or postoperative cerebrospinal-fluid-leak (OR 1.632, p=0.504). Postoperative functional status distributions were comparable between groups, indicating that despite higher complication rates, long-term disability was not significantly increased in the cystic VS cohort.
Conclusions: This large multi-institutional analysis highlighted cystic vestibular schwannomas as a clinically distinct entity associated with larger size, reduced resection rates, and higher postoperative complication rates. Importantly, cystic morphology was not an independent predictor of adverse functional outcomes or recurrence, underscoring the potential for effective management despite surgical challenges.
