Gamma Knife radiosurgery for larger-volume vestibular schwannomas. Clinical article.
OBJECTIVE
Stereotactic radiosurgery (SRS) is an important management option for patients with small- and medium-sized vestibular schwannomas. To assess the potential role of SRS in larger tumors, the authors reviewed their recent experience.


METHODS
Between 1994 and 2008, 65 patients with vestibular schwannomas between 3 and 4 cm in one extracanalicular maximum diameter (median tumor volume 9 ml) underwent Gamma Knife surgery. Seventeen patients (26%) had previously undergone resection.


RESULTS
The median follow-up duration was 36 months (range 1-146 months). At the first planned imaging follow-up at 6 months, 5 tumors (8%) were slightly expanded, 53 (82%) were stable in size, and 7 (11%) were smaller. Two patients (3%) underwent resection within 6 months due to progressive symptoms. Two years later, with 63 tumors overall after the 2 post-SRS resections, 16 tumors (25%) had a volume reduction of more than 50%, 22 (35%) tumors had a volume reduction of 10-50%, 18 (29%) were stable in volume (volume change < 10%), and 7 (11%) had larger volumes (5 of the 7 patients underwent resection and 1 of the 7 underwent repeat SRS). Eighteen (82%) of 22 patients with serviceable hearing before SRS still had serviceable hearing after SRS more than 2 years later. Three patients (5%) developed symptomatic hydrocephalus and underwent placement of a ventriculoperitoneal shunt. In 4 patients (6%) trigeminal sensory dysfunction developed, and in 1 patient (2%) mild facial weakness (House-Brackmann Grade II) developed after SRS. In univariate analysis, patients who had a previous resection (p = 0.010), those with a tumor volume exceeding 10 ml (p = 0.05), and those with Koos Grade 4 tumors (p = 0.02) had less likelihood of tumor control after SRS.


CONCLUSIONS
Although microsurgical resection remains the primary management choice in patients with low comorbidities, most vestibular schwannomas with a maximum diameter less than 4 cm and without significant mass effect can be managed satisfactorily with Gamma Knife radiosurgery.
Yang
Huai-Che
HC
Department of Neurological Surgery, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA.
Kano
Hideyuki
H
Awan
Nasir Raza
NR
Lunsford
L Dade
LD
Niranjan
Ajay
A
Flickinger
John C
JC
Novotny
Josef
J
Bhatnagar
Jagdish P
JP
Kondziolka
Douglas
D
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003390:Cranial Nerve Neoplasms / Q000473:pathology / Q000601:surgery*; D004307:Dose-Response Relationship, Radiation; D005155:Facial Nerve Diseases / Q000453:epidemiology / Q000209:etiology; D005260:Female; D005500:Follow-Up Studies; D006311:Hearing Disorders / Q000453:epidemiology / Q000209:etiology; D006801:Humans; D053208:Kaplan-Meier Estimate; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009464:Neuroma, Acoustic / Q000473:pathology / Q000601:surgery*; D011183:Postoperative Complications / Q000453:epidemiology; D016634:Radiosurgery / Q000009:adverse effects; D012189:Retrospective Studies; D012308:Risk Management; D016019:Survival Analysis; D016896:Treatment Outcome; D015837:Vestibular Diseases / Q000473:pathology / Q000601:surgery*; D055815:Young Adult