Treatment of Patients with Vestibular Schwanommas Using Gamma Knife Radiosurgery

Abstract

Gamma Knife radiosurgery (GKRS) has proved to be a safe and effective approach for small- to medium-sized vestibular schwannomas (VSs). Since VSs are histologically benign tumors, it is essential to elucidate long-term results, particularly when applied to young patients with a long life expectancy. In our analysis of 440 patients harboring VSs with a median tumor volume of 2.8 cm³ and treated at a median marginal dose of 12.8 Gy, the actuarial 5- and 10-year or longer progression-free survival was 93 and 92 %, respectively, with a median follow-up period of 12.5 years. With respect to functional outcomes, facial palsy as an adverse radiation effect seldom develops after GKRS using current radiosurgical techniques with a marginal dose of 13 Gy or less. Even if facial palsy develops, it is commonly transient. Hearing preservation after GKRS depends on hearing function at the time of treatment, treatment dose or follow-up period after treatment. In limited patients who retain Gardner-Robertson Class I hearing, a hearing preservation rate seems to be nearly 70 % at present. Special attention should be paid for delayed adverse radiation effects including malignant change and cyst formation, although such complications appear to be extremely rare.

In conclusions, GKRS is currently a reasonable alternative to microsurgical resection for small- to medium-sized VSs. From our experience for more than 20 years, GKRS is safe and effective in the long term. Management strategies including ‘wait-and-see’ approach, microsurgery and stereotactic radiosurgery should be decided for each patient, considering various factors such as age, comorbidities, tumor size, preserved hearing level or patients’ preference.