Microanatomy Based Radiosurgery For Vestibular SchwannomasMotohiro Hayashi1, Noriko Tamura1, Shoji Yomo, MD2, Mariko Nagai3, Masahiro Izawa4, Yoshikazu Okada.41Tokyo, Japan 2Saitama Gamma Knife Center, San-ai Hospital 3 San-ai Hospital RIT Kasai 4Department of Neurosurgery Keywords: vestibular schwannoma, anatomy, gamma knife, radiosurgery, image guidance
Gamma Knife surgery (GKS) has became a standard treatment ranked with surgical operation for vestibular schwannoma from the perspective of tumor control and audio-facial nerve function preservation.
We are looking forward to establish a new treatment technique, which will improve shrinkage ratio, shorten the recovery term and even to recover functioning.
91 patients were followed more than 3 years.
Along with the recent GKS system, we developed MRI sequences specific to the treatment. Newly developed sequences have enabled us to have a clear understanding of cranial nerves distribution, especially from cisternal portion to internal acoustic meatus. In addition, a fusion image with CT scan has helped us to understand anatomical relationship. At the same time we keep higher dose (80%) line area inside the tumor aiming at its shrinkage rather than just controlling it. So far, we have treated 160 cases with the above technique at our institution.
Tumor control rate was 97.8% and shrinkage one was 80.2% (84% for patients with more than 5 years follow-up), facial nerve preservation rate was 100%, hearing preservation rate was 84%, and among them, of which five (5.5%) proved to be functioning recovery case. Transient enlargement was observed in most cases, but no severe complications were found.
This is a retrospective study.
We only have preliminary results yet, but the clinical result is surely a great breakthrough as compared to the previous treatment.
We presume that longer follow-up and more treatment cases will firmly establish this method as an absolute treatment option for vestibular schwannomas. Project Roles:
M. Hayashi (), N. Tamura (), S. Yomo (), M. Nagai (), M. Izawa (), Y. Okada. ()