[Preservation of hearing function in the radiosurgical treatment of unilateral vestibular schwannomas. Preliminary results].
BACKGROUND
Preservation of functional hearing can be now attempted during the surgical treatment of a vestibular schwannomas. The probability of functional hearing preservation for each of the neurosurgical approaches is currently under evaluation. We report here a preliminary evaluation of our radiosurgical experience.


METHODS
In Marseilles, we performed 800 gamma-knife procedures for cochleovestibular schwannomas by between July 1992 and December 2000. These patients were evaluated systematically according to a prospective methodology. We report here the study of the population of 211 patients with unilateral schwannoma and a functional preoperative hearing (Gardner and Robertson 1 or 2) treated as first intention, with a follow-up longer than two years.


RESULTS
Hearing was improved with the radiosurgery in 3% of cases with a average gain of 10 decibels. Average loss in decibel on the four main frequencies (500, 1,000, 2,000, 4,000 Hz) was 17 dB. The probability of functional hearing preservation with radio surgery was high: 73%. However, this probability depended on numerous factors related to the patient and to the "operative technique". The main parameters of predictability were limited preoperative tonal loss, Gardner and Robertson stage 1 (versus 2), multiisocentric planning, peripheral dose lower than 13 Gy. So a Gardner and Robertson stage 1 intracanalicular tumor treated in accordance with "the state of the art" with a gamma-knife and a marginal dose inferior to 13 Gy has a probability of functional conservation at 2 years greater than 95%.


CONCLUSIONS
Our results are preliminary and they require the confirmation of a more extensive and more prolonged follow-up. However, the large size of this population and the systematic methodology should help us in determining more precisely the place of radiosurgery and especially to better inform the patients of their chances of hearing preservation according to their individual risk profile.
Regis
J
J
Service de Neurochirurgie Fonctionnelle et Stéréotaxie, Hôpital d'Adultes de la Timone, 264, rue Saint-Pierre, 13385 Marseille Cedex 05. jregis@ap-hm.fr
Delsanti
Ch
Ch
Roche
Ph
P
Soumare
O
O
Dufour
H
H
Porcheron
D
D
Peragut
J-C
JC
Thomassin
J-M
JM
Pellet
W
W
D005500:Follow-Up Studies; D007839:Functional Laterality / Q000502:physiology*; D006311:Hearing Disorders / Q000175:diagnosis / Q000453:epidemiology / Q000209:etiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D009367:Neoplasm Staging; D009464:Neuroma, Acoustic / Q000150:complications* / Q000473:pathology / Q000601:surgery*; D011182:Postoperative Care; D011300:Preoperative Care; D011446:Prospective Studies; D016634:Radiosurgery / Q000295:instrumentation*; D012720:Severity of Illness Index