Typing of acoustic neuromas


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

WIGAND - Ausgangssituation
WIGAND - Ausgangssituation

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).

WIGAND - Tumorgrösse Stadium
WIGAND - Tumorgrösse Stadium

Tumour size stage A:
The tumour is limited to the inner ear canal and its size (average diameter) is between 1 and 8 mm.

WIGAND - Tumorgrösse Stadium B
WIGAND - Tumorgrösse Stadium B

Tumour size stage B:
The tumour spreads into the cerebellopontine angle and has a size of between 9 and 25 mm.

WIGAND - Tumorgrösse Stadium C
WIGAND - Tumorgrösse Stadium C

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)

KOOS grading

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

KOOS gradeDescriptionTumor size
ISmall intracanalicular tumor that is located solely in the internal auditory canal (meatus acousticus internus).< 10 mm
IIMainly an intracanalicular tumor with protrusion (advancement) into the cerebellopontine angle, but without contact with the brain stem.< 20 mm
IIIA tumor located mainly in the cerebellopontine angle with contact with the brain stem, but without compression.< 30 mm
IVA large tumor with compression of the brain stem and the surrounding cranial nerves.> 30 mm

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