Kuhn classification
Kuhn classification is an anatomical classification for the subtypes of frontal cells:
- type 1 (~37%): a single air cell above the agger nasi cell
- type 2 (~19%): two or more air cells above the agger nasi cell
- type 3 (~7%): a single large cell above the agger nasi cell that extends into the frontal sinus
- type 4 (rare): cells are entirely contained within the frontal sinus