Koos grading scale

The Koos grading scale ¹ is frequently used as a classification system for vestibular schwannomas.

Classification

• 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

Reliability

A recent cross-sectional study ² proved its inter- and intra-reliability, demonstrating that the Koos classification system is a reliable method.