Combined approach for the management of large vestibular schwannomas: Planned subtotal resection followed by gamma knife surgery in a series of 20 consecutive cases

Introduction The management of large lesions of the skull base, such as vestibular schwannomas (VS) is challenging. Microsurgery remains the main treatment option. Combined approaches (planned subtotal resection followed by gamma knife surgery (GKS) for residual tumor long-term control) are being increasingly considered to reduce the risk of neurological deficits following complete resection. The current study aims to prospectively evaluate the safety-efficacy of combined approach in patients with large VS. Materials and methods We present our experience with planned subtotal resection followed by gamma knife surgery (GKS) in a consecutive a series of 20 patients with large vestibular schwannomas, treated between 2009 and 2014 in Lausanne University Hospital, Switzerland. Clinical and radiological data and audiograms were prospectively collected for all patients, before and after surgery, before and after GKS, at regular intervals, in dedicated case-report forms. Additionally, for GKS, dose-planning parameters were registered. Results Twenty patients (6 males and 14 females) with large VS had been treated by this approach. The mean age at the time of surgery was 51.6 years (range 34.4–73.4). The mean presurgical diameter was 36.7 (range 26.1–45). The mean presurgical tumor volume was 15.9 cm3 (range 5 34.9). Three patients (15%) needed a second surgical intervention because of high volume of the tumor remnant considered too large for a safe GKS. The mean follow-up after surgery was 27.2 months (range 6–61.3). The timing of GKS was decided on the basis of the residual tumor shape and size following surgery. The mean duration between surgery and GKS was 7.6 months (range 4 13.9, median 6 months). The mean tumor volume at the time of GKS was 4.1 cm3 (range 0.5–12.8). The mean prescription isodose volume was 6.3 cm3 (range 0.8–15.5). The mean number of isocenters was 20.4 (range 11–31) and the mean marginal prescription dose was 11.7 Gy (range 11–12). We did not have any major complications in our series. Postoperative status showed normal facial nerve function (House-Brackmann grade I) in all patients. Six patients with useful pre-operative hearing (GR class 1) underwent surgery with the aim to preserve cochlear nerve function; of these patients, 5 (83.3%) of them remained in GR class 1 and one (16.7%) lost hearing (GR class 5). Two patients having GR class 3 at baseline remained in the same GR class, but the tonal audiometry improved in one of them during fo