Typing of acoustic neuromas

WIGAND has defined a three-stage classification – see the schematic representations here:

Initial situation:
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:

• 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)

Acoustic neuromas are often classified according to the Koos grading system.