Facial nerve preservation after vestibular schwannoma Gamma Knife radiosurgery.
OBJECTIVE
Facial nerve preservation is a critical measure of clinical outcome after vestibular schwannoma treatment. Gamma Knife radiosurgery has evolved into a practical treatment modality for vestibular schwannoma patients, with several reported series from a variety of centers. In this study, we report the results of an objective analysis of reported facial nerve outcomes after the treatment of vestibular schwannomas with Gamma Knife radiosurgery.


METHODS
A Boolean Pub Med search of the English language literature revealed a total of 23 published studies reporting assessable and quantifiable outcome data regarding facial nerve function in 2,204 patients who were treated with Gamma Knife radiosurgery for vestibular schwannoma. Inclusion criteria for articles were: (1) Facial nerve preservation rates were reported specifically for vestibular schwannoma, (2) Facial nerve functional outcome was reported using the House-Brackmann classification (HBC) for facial nerve function, (3) Tumor size was documented, and (4) Gamma Knife radiosurgery was the only radiosurgical modality used in the report. The data were then aggregated and analyzed based on radiation doses delivered, tumor volume, and patient age.


RESULTS
An overall facial nerve preservation rate of 96.2% was found after Gamma Knife radiosurgery for vestibular schwannoma in our analysis. Patients receiving less than or equal to 13 Gy of radiation at the marginal dose had a better facial nerve preservation rate than those who received higher doses (<or=13 Gy = 98.5% vs. >13 Gy = 94.7%, P < 0.0001). Patients with a tumor volume less than or equal to 1.5 cm(3) also had a greater facial nerve preservation rate than patients with tumors greater than 1.5 cm(3) (<or=1.5 cm(3) 99.5% vs. >1.5 cm(3) 95.5%, P < 0.0001). Superior facial nerve preservation was also noted in patients younger than or equal to 60 years of age (96.8 vs. 89.4%, P < 0.0001). The average reported follow up duration in this systematic review was 54.1 +/- 31.3 months.


CONCLUSIONS
Our analysis of case series data aggregated from multiple centers suggests that a facial nerve preservation rate of 96.2% can be expected after Gamma knife radiosurgery for vestibular schwannoma. Younger patients with smaller tumors less than 1.5 cm(3) and treated with lower doses of radiation less than 13 Gy will likely have better facial nerve preservation rates after Gamma Knife radiosurgery for vestibular schwannoma.
Department of Neurological Surgery, University of California at San Francisco, San Francisco, CA 94143, USA.
Isaac
I
Yang
Michael E
ME
Sughrue
Seunggu J
SJ
Han
Shanna
S
Fang
Derick
D
Aranda
Steven W
SW
Cheung
Lawrence H
LH
Pitts
Andrew T
AT
Parsa
D000367:Age Factors; D005154:Facial Nerve / Q000528:radiation effects* / Q000601:surgery; D020220:Facial Nerve Injuries / Q000453:epidemiology* / Q000209:etiology*; D006801:Humans; D008875:Middle Aged; D009464:Neuroma, Acoustic / Q000473:pathology / Q000601:surgery*; D011183:Postoperative Complications / Q000453:epidemiology / Q000209:etiology; D016634:Radiosurgery / Q000009:adverse effects* / Q000379:methods; D011879:Radiotherapy Dosage