Table 1: Classification of frontal osteomas according to extension and implantation.

 

Computed Tomography

GRADEI

Posterior inferior implantation in frontal recess

Tumor medial to the lamina papyracea

Anteroposterior diameter of the tumor is 75% of the anteroposterior diameter of the frontal recess

GRADEII

Anteroposterior diameter of the tumor is greater than 75% of the anteroposterior diameter of the frontal recess

GRADEIII

Implantation is anterior or superior in the frontal sinus

Tumor extends lateral to the lamina papyracea

GRADEIV

The tumor occupies the entire frontal sinus