Radiosurgery for type II neurofibromatosis.

A summary of our radiosurgical experience treating type II neurofibromatosis (NF2) vestibular schwannomas (VSs), based on a retrospective consecutive series of 122 tumours in 92 patients, with an extended series of a further 22 patients (906 patient-years of follow-up) to investigate the risk of malignancy after radiosurgery. With current techniques, we estimate that 8 years after radiosurgery for NF2 VS, 20% of patients will have required further treatment, 50% will be well controlled, and in 30% there will have been some concern about control, but they will have been managed conservatively. Three years after treatment, approximately 40% retain their functional hearing, 40% have some deterioration, 20% becoming deaf in that ear. The risk of facial palsy was 5%. Two malignancies were recorded after radiosurgery, in one the malignant behaviour preceded treatment. This is less than the previously reported rate of spontaneously developing malignant gliomas in NF2. Whilst the clinical results are far worse than those achieved treating sporadic tumours, this applies equally to the results of surgery or observation when treating NF2 tumours. It is important therefore that these patients are given advice specific for NF2. Considering this, we believe that radiosurgery remains a valuable minimally invasive treatment option for selected NF2 patients.