From: Early magnetic resonance image volumetric changes of vestibular schwannoma after Gamma Knife radiosurgery: a prospective study of 18 cases
Grade
Definition
1
Intracanalicular
2
Tumor in the cerebellopontine angle but not reaching the pons
3
Tumor reaching the pons, perhaps deforming it but not shifting it
4
Tumor deforming the pons and shifting the fourth ventricle