PT  - JOURNAL ARTICLE
AU  - Nakamura, Hiroyuki
AU  - Jokura, Hidefumi
AU  - Takahashi, Kou
AU  - Boku, Nagatoshi
AU  - Akabane, Atsuya
AU  - Yoshimoto, Takashi
TI  - Serial Follow-up MR Imaging after Gamma Knife Radiosurgery for Vestibular Schwannoma
DP  - 2000 Sep 01
TA  - American Journal of Neuroradiology
PG  - 1540--1546
VI  - 21
IP  - 8
4099  - http://www.ajnr.org/content/21/8/1540.short
4100  - http://www.ajnr.org/content/21/8/1540.full
SO  - Am. J. Neuroradiol.2000 Sep 01; 21
AB  - BACKGROUND AND PURPOSE: Gamma knife radiosurgery has become an important treatment option for vestibular schwannoma. The effect of treatment can be assessed only by neuroimaging. We analyzed the evolution of follow-up MR imaging findings after gamma knife radiosurgery to provide information for the clinical management of these tumors.METHODS: Changes in tumor volume and enhancement were assessed visually on 341 follow-up MR studies obtained in 78 of 86 consecutive patients with unilateral vestibular schwannoma who underwent gamma knife radiosurgery.RESULTS: Follow-up MR studies were obtained between 10 and 63 months (mean, 34 months) after treatment. Tumor control rate was 81%. Changes in tumor volume were classified as temporary enlargement (41%), no change or sustained regression (34%), alternating enlargement and regression (13%), or continuous enlargement (12%). Temporary enlargement occurred within 2 years after radiosurgery. Changes in tumor enhancement were classified as transient loss of enhancement (84%), continuous increase in enhancement (5%), or no change in enhancement (11%). There was no significant correlation between changes in tumor volume and tumor enhancement. Areas of T2 hyperintensity in adjacent brain tissue appeared in 31% of patients.CONCLUSION: Dynamic changes in vestibular schwannoma are seen on serial follow-up MR studies obtained after gamma knife radiosurgery. An increase in tumor size up to 2 years after radiosurgery is likely to be followed by regression. Changes in contrast enhancement are not predictive of clinical outcome. Neuroimaging follow-up is recommended.