An intramural macrocyst of an acoustic neurinoma rupturing after gamma knife radiosurgery: a case report.

We want to describe the rare case when an intramural macrocyst within an acoustic neurinoma (ACN) treated by gamma knife radiosurgery (GKRS) ruptured, followed by an impressive decrease of tumor volume and improvement of neurological symptoms. In a 59-year-old female patient, a large ACN with a hugh intramural macrocyst was diagnosed. As she refused open surgery, we performed GKRS covering the tumor margin and the cyst with 11 Gy. Seven months after treatment symptoms worsened slightly. Magnetic resonance imaging (MRI) revealed no significant change of tumor volume. One year after GKRS she felt a sensation behind her treated ear, followed by an immediate improvement of all her symptoms. Trigeminal hypaesthesia and vertigo disappeared, tinnitus ameliorated. A control MRI showed the cystic compartment no longer, the solid part shrunk within the following six years. Within the whole follow-up period hearing was stable. To our knowledge this is the first report of a macrocyst within an ACN to rupture after GKRS.