Combined Approach for Large Vestibular Schwannomas: Planned Subtotal Resection Followed by Gamma Knife Surgery: An Update on a Series of 40 Consecutive Cases

Background: The surgical management of large vestibular schwannomas (VS) yields a high risk for the facial and cochlear nerve functions. Gamma Knife radiosurgery (GKRS) allows optimal functional results in small- and medium-size VS, but cannot be used upfront in large VS because of the high rate of volume-related side effects.

Methods: To develop of a new treatment paradigm of combined approach with microsurgery and GKS, aiming at optimal functional outcome for the facial and cochlear nerves in patients with large VS (i.e., Koos grade IV). To perform planned subtotal resection followed by GKRS in a consecutive a series of patients with large VS. Data pertaining to patient characteristics, surgical and dosimetric features and outcome were collected prospectively at time of treatment and during the follow-up course.

Results: A consecutive a series of 40 patients was treated between 2010 and January 2017. The mean presurgical tumor volume was 12 cm3 (1.47–34.9). All cases had normal facial nerve function (HB I) before surgery, except for one who was in HB IV. Postoperative status showed normal facial nerve function (House-Brackmann grade I) in all patients. In a subgroup of 22 patients in which cochlear nerve preservation was attempted at surgery (patients with residual hearing before surgery), 21 of them (95.4%) retained residual hearing. Among them, 16 patients had normal hearing (Gardner-Robertson class 1) before surgery, and 13 (81.2%) retained normal hearing after surgery. The mean duration between surgery and GKRS was 6.2 months (4–13.9, median 6 months). The mean tumor volume at the time of GKRS was 3.6 cm3 (0.5–12.8), which corresponds to a mean residual volume of 31.4% (range 3.6–50.2) of the pre-operative volume. There was a tendency toward larger postoperative residual volume in patients with attempt to cochlear nerve preservation. The mean marginal prescription dose for GKS was 11.9 Gy (range 11–12, median 12 Gy). Following GKRS, there were no new neurological deficits, with facial and hearing functions remaining identical to that after surgery. The mean follow-up after surgery was 31 months (range 3–72).

Conclusion: Our data suggest that the management of large VS with planned subtotal resection followed by GKRS may yield an excellent clinical outcome with respect to retaining facial and cochlear nerve functions. Our results with this approach are comparable to those obtained with GKRS alone in small- and medium-size VS.

 

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No conflict of interest has been declared by the author(s).