| Grade | Tumor |
| T1 | Purely intracanalicular |
| T2 | Intrameatal or extrameatal |
| T3a | Filling the cerebellopontine cistern |
| T3b | Reaching the brainstem |
| T4a | Compression of the brainstem |
| T4b | Compression of the brainstem with dislocation of the fourth ventricle |