Frontal infundibular cells: pathway to the frontal sinus.

A frontal infundibular cell (FIC) is an uncommon anatomic variant of an anterior ethmoid pneumatization that originates from the frontal recess and typically extends into the lumen of the frontal sinus ostium. FICs may show several anatomic variants that impact the anatomy of the frontal recess. Familiarity with these variants is required for safe endoscopic sinus surgical procedures. We conducted a retrospective chart review, examining 1,040 frontal recesses in 520 adults with no frontal sinus disease, to explore the anatomy of the healthy frontal recess and to describe the prevalence of FICs in patients without a history of conditions that cause frontal pneumatization. Review of axial and coronal computed tomography data, which were reformatted for sagittal reconstruction, was performed at a computer workstation. Bent and Kuhn's classification was used to define types of FICs. We identified 167 patients (32.1%) as having unilateral or bilateral FICs. Type I infundibular cells were the most common type (found in 15.7% of the entire study population). Type II and type III FICs were found in 3.8% and 12.1%, respectively; type IV FICs were present in 0.4%. The FIC has not been emphasized as an important potential cause of frontal sinus obstruction in the radiology literature, but clinicians should specifically watch for it on all routine computed tomography of the frontal sinus. Fine-cut computed tomography scans aid in the identification of each individual cell and allow the surgeon to formulate a clear and precise surgical plan. A surgical plan with a thorough understanding of the anatomy enables confident dissection of this complex and difficult area.