The two - staged treatment of large vestibular schwannomas: surgery and gamma knife radiosurgery

Koo Van Overbeeke1, Rik van de Langenberg2, Patrick Hanssens3

1 2Dept. of Neurosurgery and ENT. University Hospital , Maastricht, The Netherlands 3Gaam Knife Center, St. Elisabeth Hospital , Tilburg, The Netherlands

Keywords: vestibular schwannoma, technique, gamma knife, radiotherapy, outcome

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     Large vestibular schwannomas ( Koos grade 3 and 4) represent a challenge to preserve the facial nerve. Although in large series anatomical preservation is reported in 80–90 % , permanent damage of the facial function remains an usual complication in more than 40%. 
     Based on the good results of LGK treatment on small non-operated vestibular schwannomas, we developed a two-stage treatment of large vestibular schwannomas : partial surgical removal of schwannoma as followed by LGK radiosurgery of the remnant.
     The first 50 cases were evaluated in detail.
     175 Large vestibular schwannomas underwent surgical partial removal followed by LGK radiosurgery. The mean volume of these tumors was 15 cc. The mean volume reduction was 75 %. The remnant of the tumor was treated by LGKradiosurgery with 11 Gy as minimum dose at the margin. The average time of LGK treatment after surgery was 8.5 months, the follow-up period 33.6 months.
     A functional facial nerve preservation( House /Brackman stage 1/2) after 6 months was found in 65 %, after 1 year in 94%. Growth control in 90 %: shrinkage was found in 46%, transient growth and shrinkage in 12 % and a stable volume in 32%. One patient had a serious complication related to surgery ( hemiparesis ). In 5 patients ( 10%) further growth was found. Of these 2 patients had a second surgery, 3 were treated for the second time with LGK radiosurgery.
     This was a retrospective review and not all patients were studied to date.
     The two-staged treatment of the large vestibular schwannomas shows very satisfactory results for the functional preservation of the facial nerve. Furthermore the tumor control rate was comparable with the gamma knife results of the non-operated small vestibular schwannomas.
     Two questions remain to be answered: 1- why do 10% of the operated vestibular schwannomas grow after treatment with LGK radiosurgery? In this respect molecular biology of the vestibular schwannoma of the same patient before and after gamma knife radiosurgery will provide a possible answer 2- do all patients need to be treated with LGK radiosurgery or should it be reserved for patients with an MRI documented growth after surgery? 


Project Roles:

K. Van Overbeeke (), R. Langenberg (), P. Hanssens ()