Management of vestibular schwannoma by fractionated stereotactic radiotherapy and associated cerebrospinal fluid malabsorption

Abstract

Object. The goal of this study was to investigate outcomes in patients with vestibular schwannoma (VS) who were treated with fractionated stereotactic radiotherapy (SRT). Methods. One hundred one patients with VS were treated with fractionated SRT at a radiation level of 40 to 50 Gy administered in 20 to 25 fractions over a 5- to 6-week period. The median tumor size in these patients was 19 mm (range 3–40 mm), and 27 tumors were larger than 25 mm. Patients were consistently followed up using magnetic resonance imaging every 6 months for 5 years in principle. The median follow-up period was 45 months. The actuarial 5-year rate of tumor control (no growth > 2 mm and no requirement for salvage surgery) was 91.4% (95% confidence interval 85.2–97.6%). Three patients with progressive tumors underwent salvage tumor resection. The actuarial 5-year rate of useful hearing preservation (Gardner—Robertson Class I or II) was 71%. The observed complications of fractionated SRT included transient facial nerve palsy (4% of patients), trigeminal neuropathy (14% of patients), and balance disturbance (17% of patients). No new permanent facial weakness occurred after fractionated SRT. Eleven patients (11%) who had progressive communicating hydrocephalus (cerebrospinal fluid malabsorption) and no evidence of tumor growth after fractionated SRT required a shunt. The symptoms of this type of hydrocephalus were similar to those of normal-pressure hydrocephalus and occurred 4 to 20 months (median 12 months) after fractionated SRT. The mean size (± standard deviation) of tumors causing symptomatic hydrocephalus (25.5 ± 7.8 mm) was significantly larger than that of other tumors (18.2 ± 8.7 mm) (p = 0.011). Only four of the 72 patients with tumors smaller than 25 mm in maximum diameter received a shunt. Conclusions. Fractionated SRT resulted in an excellent tumor control rate, even for relatively large tumors, and produced a high rate of hearing preservation that was comparable to the best results of single-fraction radiosurgery. The progression of communicating hydrocephalus should be monitored closely, particularly in patients harboring a large VS.

The newly diagnosed vestibular schwannoma: radiosurgery, resection, or observation?

“…The mean proportion of pre-and post-SRT speech discrimination was 91% and 59%, respectively. Sawamura et al 53 treated 101 patients with vestibular schwannomas using fractionated SRT to a total dose of 40-50 Gy, administered in 20-25 fractions over a 5-to 6-week period. The median follow-up period was 45 months, and the actuarial 5-year tumor control rate was 91.4%.…”

Radiotherapy for Vestibular Schwannomas: A Critical Review

“…Most institutions used a 1-2-mm margin on the contrast-enhancing tumor as seen on MRI (52,54,56,57,59,60). Using various fractionation schemes, the rate of trigeminal and facial nerve preservation has been $95% and $94%, respectively (47,(51)(52)(53)(54)(55)(56)(57)(58)(59)(60).…”

“…The current radiation dose prescribed for FSRT ranges between 40-57.6 Gy in 1.8-2-Gy/fraction (47,52,53,(55)(56)(57)(58)(59)(60). The ultimate goal of these fractionation schemes has been to improve the rate of hearing preservation.…”

Evaluation of hearing function after Gamma Knife surgery of vestibular schwannomas

“…21,28,34,39,46,53 Surgery has been the only therapeutic option available for a long time, and the costs are high mortality and morbidity rates. In the past the preservation of hearing function was a difficult goal to achieve.…”