gms | German Medical Science

Objective: Microsurgical resection of solely intracanalicular acoustic neurinoma (iAN) is challenging. The risk of hearing loss is described with up to 40% and N. VII disturbance ranging from 4 -16%. Stereotactic Radiosurgery (SRS) has evolved as alternative first-line treatment for small AN. Here we report about the long-term follow-up of an unique cohort of patients with iAN after LINAC or Cyberknife^® based radiosurgery.

Method: In this single center retrospective analysis we included all patients with iAN who underwent single session LINAC or Cyberknife^® based radiosurgery between 1993 and 2015 and had a minimum follow-up of 5 months. Patient data were analyzed in terms of radiological tumor- and clinical symptom control, preservation of hearing and incidence of complications or unexpected side effects.

Results: 51 patients (f/m =22/29, median age 54 ± 12, range 20-77 years) were identified. Mean tumor volume was 0.24 ± 0.12 cm³ (range, 0.1-0.68 cm³), the mean marginal dose was 12.6 ± 0.6 Gy (range, 11.0-14.0 Gy) and the prescription isodose was 75 ± 7.5% (range, 47-86%). Mean follow-up was 38 months (range, 5-142 months). Radiological tumor control was observed at 6 and 12 months follow-up with 100% and at 24 months with 96%. Functional hearing prior to SRS remained stable in 75% (n=18/24) at last follow-up. No radiation induced adverse effects were observed; one case developed transient facial palsy (House and Brackmann II) after 12 months and another case sustained hemifacial spasm after three months resolving six months after SRS.

Conclusions: SRS for iAN shows long-term a reliable tumor control with a high rate of hearing preservation without considerable permanent side effects and can be proposed as save and effective treatment alternative to microsurgical resection.