Sphenomaxillary Plate: Landmine or Landmark?

Abstract

Objectives: Sphenomaxillary plate (SMP) is an inconstant bony septum separating the maxillary and sphenoid sinuses. Neglecting the SMP during endoscopic sinus surgery may lead to mistaking the sphenoid sinus for the posterior ethmoid cell with potentially dangerous consequences. However, its proper identification may allow planned sphenoidotomy through the posterior wall of the maxillary sinus or to enlarge transnasal or transethmoidal sphenoidotomy. The aim of this study was to evaluate (1) the incidence and morphology of the SMP and (2) possibility and safety of trans-SMP sphenoidotomy. Methods: In the radioanatomical part of the study multiplanar reconstruction analysis of 117 consecutive paranasal sinus CT scans was conducted. In the clinical part of the research, trans-SMP sphenoidotomy was performed in consecutive patients operated on for chronic rhinosinusitis. Results: The SMP was found in 25% of sides (34% of patients). It was constantly located superolateral to the posterior insertion of the middle turbinate. The SMP formed the prominence on the posterior wall of the maxillary sinus that could be identified using volume rendering in 11% of sides (19% of patients). 30 trans-SMP sphenoidotomies were performed in 18 patients. The SMP prominence was identified in 15 sides. In absence of SMP prominence, identification of the SMP was still possible using other anatomical landmarks. Conclusions: The SMP is present in over 30% Caucasian subjects at least on one side. Sphenoidotomy through the SMP is feasible and safe.