Koos grading scale
The Koos grading scale is frequently used as a classification system for vestibular schwannomas.
- grade 1: small intracanalicular tumor
- grade 2: small tumor with protrusion into the cerebellopontine cistern (CPA); no contact with the brainstem
- grade 3: tumor occupying the cerebellopontine cistern with no brainstem displacement
- grade 4: large tumor with brainstem and cranial nerve displacement
A recent cross-sectional study proved its inter- and intra-reliability, demonstrating that the Koos classification system is a reliable method.