Retromaxillary Pneumatization of Posterior Ethmoid Air Cells: Novel Description and Surgical Implications.

Objective: Retromaxillary pneumatization of posterior ethmoid (PE) air cells is an area that is yet to have appropriate description in rhinologic literature.

Study Design: Case series with chart review.

Setting: Tertiary care hospital.

Subjects And Methods: First, 524 sides in 262 paranasal sinus computed tomography scans were analyzed: 350 normal sides were examined for PE pneumatization lateral to the sagittal plane of the medial wall of maxillary sinus posteriorly, and 174 diseased sides were similarly reviewed to check how pathology may affect identification and measurements. Following that, 153 operated sides in 84 cases prepared for revision endoscopic sinus surgery (ESS) were studied for residual diseased cells at different anatomic locations.

Results: Overall, retromaxillary PE pneumatization was identifiable in 416 of the 524 sides (79.4%). Lateral retromaxillary extension varied from 0.5 to 12.3 mm (mean ± SD, 4.8 ± 2.3 mm). This area of pneumatization is bounded anteroinferiorly by the junction between the posterior and superior walls of the maxillary sinus. Three cell types were described depending on the degree of lateral extension (type I, <3 mm; type II, 3-6 mm; type III, >6 mm). This cell, which we refer to as the Herzallah cell, was distinguishable from the anterior ethmoid Haller cell and was found to have residual disease in 50.3% of cases prepared for revision ESS.

Conclusion: Retromaxillary extension of PE air cells varies considerably and requires attention during ESS. Residual undissected retromaxillary cell is a common finding in revision ESS and can contribute to inadequate disease clearance.