A new CBCT-based classification of posterior extramural ethmoid cells

Area of Science:

• Anatomy
• Radiology
• Otolaryngology

Background:

• Posterior ethmoid (PE) cells can exhibit extramural expansion, leading to anatomical variations.
• Onodi cells, a specific type of sphenoethmoidal cell, extend towards the optic canal.
• Accurate identification of these cells is vital for clinical management.

Purpose of the Study:

• To evaluate the prevalence of extramural expansion of posterior ethmoid cells using Cone Beam Computed Tomography (CBCT).
• To propose anatomical criteria and a classification system for Onodi cells based on their relationship with the sphenoid sinus.

Main Methods:

• Cone Beam Computed Tomography (CBCT) scans were analyzed from 513 outpatient clinic patients.
• The study included 199 men and 314 women with a mean age of 36 years.

Main Results:

• Sphenoethmoidal cells were identified in 66 of 513 patients (89 cells), showing significant anatomical diversity.
• Predominant Onodi cell variants included superior (48.2%), superolateral (19.2%), and lateral (18%).
• Other variants like supraseptal and inferolateral sphenoethmoidal cells were also observed.

Conclusions:

• An updated classification for Onodi cells was proposed, considering their spatial relationship with adjacent structures.
• Posterior extramural ethmoid cells can mimic the sphenoid sinus on imaging, necessitating precise differentiation.
• Correct radiological assessment is essential to determine the origin of inflammation and guide appropriate treatment.