[Gamma Knife surgery for VII nerve schwannomas]

Radical resection of VII nerve schwannomas classically implies a high risk of severe facial palsy. Due to the rarity of facial palsy after Gamma Knife surgery (GKS) of vestibular schwannomas the evaluation of GKS in this specific difficult group of patient appears rational. We have found no similar evaluation in the literature.

Among 1.000 schwannomas of the cerebello-pontine angle operated in Marseilles, France between July 1992 and March 2003, 9 have been diagnosed as originating from the VII. Criterias for this diagnosis are the involvement of the second or third portion of the VII nerve canal (7 patients) and/or peroperative observation during a previous microsurgery (2 patients). The rare facial palsy after vestibular schwannomas radiosurgery occurring usually before 18 Months have been considerated only the patients with more than 2 Years of follow-up (8 patients).

Four of these patients had the experience of a previous spontaneous facial palsy one (3 patients) or several times (1 patient). A normal motor facial function was observed only in 2 cases before GKS (House 2 in 6 patients, House 3 in one). The follow-up was 2-7 Years for the evaluable patients. None of these have developed or worsened facial palsy, two have improved their preoperative facial palsy. To date, all tumors have been evaluated. The specificity and heterogeneity of this group of patients led us to develop an original classification in 4 anatomical types presenting different clinical and surgical difficulties.

This first study demonstrates that radiosurgery allows treating these patients while preserving a normal motor facial function. Because of this advantage, GKS must be considered as a first option for all small to middle sized facial nerve schwannomas.