11. Karnofsky ≥ 50 for patients > 16 years of age and Lansky ≥ 60 for patients ≤ 16 years of age (See Appendix I for the Karnofsky-Lansky Scores). Patients who are unable to walk because of paralysis, but who are up in a wheelchair, will be considered ambulatory for the purpose of assessing the performance score. Patients with posterior fossa syndrome/cerebellar mutism demonstrating clear improvement post-surgically can be enrolled based on physician discretion.