Long-term complications following gamma knife radiosurgery of vestibular schwannomas.

Since its inception in 1969, Gamma Knife radiosurgery (GKR) for vestibular schwannomas has been documented as an efficient and safe procedure based on more than 8,000 treatments worldwide. The author's personal experience comprises 669 treatments for patients with vestibular schwannoma between 1969-1997. This experience demonstrates long-term growth control, usually with shrinkage, in 95% of unilateral tumors. In the mid-1970s, early facial weakness occurred in 38% and facial numbness in 33%. This has gradually decreased to less than 2% in the 1990s. Preservation of hearing (unchanged or almost unchanged) is currently achieved in 65 to 70%. Tinnitus is rarely changed by the treatment. The risks of intracranial bleeding, infection and CSF leak are avoided because of the noninvasive nature of the treatment. Hydrocephalus directly induced by the tumor occurred in 9.2% of patients. On the other hand, a treatment%related peritumoral reaction sufficient to block the CSF circulation and require shunt insertion was seen in only 1.4%. Based on experiences worldwide, the incidence of secondary neoplasia seems to be 0.1%. The effectiveness of GKR together with its low complication rate makes it a suitable treatment for anyone, regardless of age and general health. With few exceptions, schwannomas with an intracranial size of up to approximately 3 cm are suitable for GKR.