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 3 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 3 in CVSs; 4.75 ± 6.48 cm 3 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.