WIGAND has defined a three-stage classification – see the schematic representations here:
The tumour sits on the nerve in such a way that its weight prevents the blood supply required for proper nerve function (vascular compression).
Tumour size stage A:
The tumour is limited to the inner ear canal and its size (average diameter) is between 1 and 8 mm.
Tumour size stage B:
The tumour spreads into the cerebellopontine angle and has a size of between 9 and 25 mm.
Tumour size stage C:
The tumour has contact with the brain stem and is larger than 25 mm.
SAMII defines six tumour classes:
Acoustic neuromas are often classified according to the Koos grading system.
|KOOS grade||Description||Tumor size|
|I||Small intracanalicular tumor that is located solely in the internal auditory canal (meatus acousticus internus).||< 10 mm|
|II||Mainly an intracanalicular tumor with protrusion (advancement) into the cerebellopontine angle, but without contact with the brain stem.||< 20 mm|
|III||A tumor located mainly in the cerebellopontine angle with contact with the brain stem, but without compression.||< 30 mm|
|IV||A large tumor with compression of the brain stem and the surrounding cranial nerves.||> 30 mm|