Koos grading scale

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The Koos grading scale  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 proved its inter- and intra-reliability, demonstrating that the Koos classification system is a reliable method.