Reduced-dose radiosurgery for vestibular schwannomas.
OBJECTIVE
To evaluate tumor control and complications associated with low-dose radiosurgery for vestibular schwannomas.


METHODS
Between December 1993 and January 2000, 47 patients with vestibular schwannomas were treated at our center with gamma knife radiosurgery. The marginal tumor doses ranged from 7.5 to 14.0 Gy (median, 12.0 Gy) for patients treated after microsurgery and from 10.0 to 15.0 Gy (median, 12.0 Gy) for patients in whom radiosurgery was the primary treatment. The median maximum tumor diameter was 18 mm (range, 3-50 mm). Evaluation included audiometry, neurological examination, and serial imaging tests. A survey was conducted at the time of analysis.


RESULTS
Follow-up data were available for 45 patients and ranged from 1 to 7 years (median, 3.6 yr). In 43 patients (96%), tumor control (no radiographic progression or surgical resection) was observed. All 33 previously untreated patients had tumor control. Transient facial weakness, experienced in two patients (4%), had resolved completely within 6 months. No patient developed trigeminal neuropathy. Hearing was diminished from baseline in 12% of patients with useful hearing (Gardner-Robertson Class III). However, all patients with pretreatment hearing Gardner-Robertson Class I or II maintained testable hearing (Class I to III) at the most recent examination.


CONCLUSIONS
Low-dose radiosurgery in this series provided comparable local control and decreased incidences of complications in relation to other reports. Additional follow-up will allow more definitive conclusions to be reached regarding the ultimate rates of tumor control and hearing preservation. Nevertheless, the current dose used for vestibular schwannomas at the University of Maryland Medical Center is 12.0 Gy to the tumor periphery.
Petit
J H
JH
Department of Neurological Surgery, University of Maryland Medical Center, Baltimore, Maryland 21201-1595, USA. jpetit001@maryland.edu
Hudes
R S
RS
Chen
T T
TT
Eisenberg
H M
HM
Simard
J M
JM
Chin
L S
LS
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001301:Audiometry, Pure-Tone; D005260:Female; D005500:Follow-Up Studies; D006319:Hearing Loss, Sensorineural / Q000175:diagnosis; D006801:Humans; D008297:Male; D008875:Middle Aged; D009460:Neurologic Examination; D009464:Neuroma, Acoustic / Q000601:surgery*; D011183:Postoperative Complications / Q000175:diagnosis; D016634:Radiosurgery / Q000379:methods*