Auditory Preservation in Elderly Patients Undergoing Gamma Knife® Radiosurgery for Vestibular Schwannoma

by Al Ozpinar, MD; Matthew Pease, MD; and Edward A. Monaco III, MD, PhD

Vestibular schwannomas are benign tumors that arise from cranial nerve eight, the hearing nerve. Management of these tumors in elderly patients is a controversial topic. Its incidence is approximately 1 in 100,000 person-years, and the median age of diagnosis is approximately 55 years of age, with a mean growth rate that ranges between 1 and 4mm per year.

Many physicians advocate a conservative approach, but a considerable number of tumors (6-20%) will eventually require definitive intervention. Micro-surgical resection has been shown to be safe in the elderly, but these  patients fare worse after open surgery in terms of recovery and overall mortality than their younger counterparts. Gamma Knife® radiosurgery (GKRS) has the benefit of being less invasive than open brain surgery, and it is well established as a definitive treatment in younger patients with vestibular schwannomas.

Data on GKRS in the management of vestibular schwannomas in elderly patients is, however, lacking. The records of 60 patients aged 80-95 (20 male, 40 female), with a mean age of 83.5 years treated with GKRS for vestibular schwannomas at our institution between 1988 and 2011 were retrospectively reviewed. Demographic, GKRS dose planning, clinical and radiographic data, Gardner-Robertson (GR) grades, and outcome data were evaluated before and after GKRS.

Following GKRS, follow-up interval ranged from 3.7-155.1 months (mean=38.8). At the time of the analysis, 40 patients had died, and 17 were lost to follow-up. The median overall survival (OS) was 123.4 months following GKRS (range 4.83-227.7 months, 95% CI=76.9-144). Twenty-seven tumors (57%) were stably controlled and 15 decreased in size (32%). Progression was found in three (6%) patients. Six patients (12.5%) experienced adverse radiation effects. At the time of GKRS, 37 (79%) patients had serviceable hearing on the ipsilateral side of their vestibular schwannomas (22 with GR I, 15 with GR II). At the time of follow-up audiometric testing, out of these 37 patients with serviceable hearing, 17 (36%) patients maintained serviceable hearing and 13 (26%) patients lost serviceable hearing but still maintained some degree of hearing (GR III or GR IV).

This data (about 50% preservation of GR class of hearing) is consistent with previous literature in younger patients. In patients with vestibular schwannomas aged 80-95 years, Gamma Knife radiosurgery provides tumor control, hearing preservation, and a minimal side effect profile. Gamma Knife radiosurgery should be considered as a viable treatment strategy in elderly patients who require intervention for vestibular schwannomas.