Koos Grade (Vestibular Schwannoma)
Koos classification (Koos 1998) of a vestibular schwannoma (acoustic neuroma), grades I-IV, by extrameatal extension and brainstem involvement - used to stratify these tumors for radiosurgery-vs-microsurgery planning.
Open the calculator → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- Koos grade
- Grade IV - compresses the brainstem
Result: Koos grade IV: a large tumor that compresses the brainstem and displaces the fourth ventricle.
The tool opens with these values already filled in. Replace them with your own.
What the result means
- Grade I
- Intracanalicular; limited to the internal auditory canal, no extrameatal extension.
- Grade II
- Extends into the cerebellopontine angle but does not contact the brainstem.
- Grade III
- Contacts the brainstem but does not displace it.
- Grade IV
- Compresses the brainstem and displaces the fourth ventricle.
What you enter
- Koos grade
How this is calculated
Koos WT, Day JD, Matula C, Levy DI. Neurotopographic considerations in the microsurgical treatment of small acoustic neurinomas. J Neurosurg. 1998;88(3):506-512. Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.