The Koos classification is used for the anatomical classification of Vestibular schwannomas and was published by Koos et al[^1] in 1998.
Classification
Koos grade | Definition |
Koos grade I | The tumor is located exclusively within the Internal acoustic meatus. |
Koos grade II | The tumor extends to the Cerebellopontine angle without involvement of the brainstem. |
Koos grade III | The tumor fills the entire cerebellopontine angle. |
Koos grade IV | The tumor displaces the brainstem and the adjacent Cranial nerves. |
