Acoustic neuroma classification/staging

WIGAND has defined a trinomial classification:

Tumour size stage A: The tumour is limited to the inner auditory passage and is 1-8 mm (average diameter) in size. Tumour size stage B: The tumour has spread up to the cerebellopontine angle and is 9-25 mm in size. Tumour size stage C: The tumour has made contact with the brainstem and is bigger than 25 mm.

SAMII defines six tumour classes:

T1: clear intrameatal tumour (in the bony ear canal) T2: intra and extrameatal tumour part (within and outside of the bony ear canal) T3a: Tumour fills the cerebellopontine cistern (between the cerebellum and brainstem) T3b: Tumour reaches the brainstem T4: Tumour compromises the brainstem T4b: Tumour compromises the brainstem and displaces the four ventricles (cerebral ventricle)