Supraorbital air cells

• Pneumatized cells extending posteriorly and superiorly over the orbit, arising from the anterior ethmoid air cells and frontal recess
• Posterior wall of these cells located at the skull base, which can mimic septated frontal sinuses
• Cells typically identified as multiple air-filled compartments in the orbital plate of the frontal bone posterior to the main frontal sinus

• Supraorbital air cells appear as air-density (CT) or T2/FLAIR hyperintense (MRI) cells that pneumatize the orbital plate of the frontal bone posterior to the frontal sinus and frontal recess.
• These cells originate from the anterior ethmoid air cells and extend posteriorly and superiorly over the orbit, with a posterior wall at the level of the skull base.
• The cells usually drain into the lateral aspect of the frontal recess, and may be solitary or multiple (present in approximately 25-35% of individuals, with multiple cells in up to 5%).
• On CT, the posterior wall corresponds to the cribriform plate and anterior skull base, which is an important anatomic landmark to distinguish these cells from a normal frontal sinus.
• The anterior ethmoidal artery is typically visible as a linear density or flow void coursing freely through the ethmoid air cell compartment within or adjacent to these cells.
• Supraorbital air cells may expand to partially obstruct the frontal recess, which is clinically relevant as obstruction of the frontal recess can contribute to frontal sinusitis.

• Septated frontal sinus: distinguished by the location of the posterior wall at the skull base rather than within normal frontal sinus pneumatization, and by the cells' origin from the anterior ethmoid cells rather than the frontal sinus proper.
• Dehiscent anterior ethmoid air cells: distinguished by the location relative to the orbit and frontal recess; supraorbital cells are specifically posterior and superior to the orbit.
• Frontal recess obstruction from polyps or inflammation: can coexist with supraorbital air cells, but the cells themselves are normal pneumatized compartments rather than pathologic masses.

When reporting supraorbital air cells on pre-operative sinus imaging, clearly describe their location (posterior and superior to the orbit, within the orbital plate of the frontal bone), note whether they obstruct or contribute to obstruction of the frontal recess, and explicitly identify the course of the anterior ethmoidal artery to alert the surgeon to the risk of injury.

• Mistaking supraorbital air cells for an abnormal, septated frontal sinus—remember that these cells are normal pneumatization originating from the anterior ethmoid air cells, not a pathologic process.
• Confusing supraorbital air cells with the frontal recess itself on pre-operative imaging, which can lead to mislocalization of obstruction and surgical planning errors.
• Failing to identify and describe the course of the anterior ethmoidal artery in the presence of supraorbital air cells, increasing the risk of vascular injury during FESS.
• Overlooking multiple supraorbital air cells (present in up to 5% of individuals), which may have greater impact on frontal recess obstruction and surgical difficulty.