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 5cm(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 (20.4413.85cm(3) in CVSs; 4.75 +/- 6.48cm(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.