Middle meatal nasal recesses of the maxillary sinuses and dangerously modified nasal anatomy

Pneumatisation of the maxillary sinus (MS) is variable. The archived cone-beam computed tomography file of a54-year-old female was retrospectively evaluated anatomically. Nasal or retrobullar recesses of the MSs (NRMS) were found. The MSs were bicameral. NRMSs extended from the postero-lateral chambers of the MSs into the lateral nasal walls. Theright NRMS was reached superior to the middle turbinate and the ethmoidal bulla was applied on its anterior side. The leftNRMS had two medial pouch-like ends, one beneath the ethmoidal bulla and the other on the anterior side of the basallamella of the middle turbinate. Additional anatomical findings were the uncinate bulla, infraorbital recesses of the MS,maxillary recess of the sphenoidal sinus, and atypical posterior insertions of the superior nasal turbinates, maxillo-ethmoidosphenoidal and ethmoido-sphenoidal. The NRMS is a novel finding and could lead to erroneous endoscopic corridors if notdocumented before the interventions.