Spatial anatomy of the nasofrontal recess on the CT using multiplanar reconstruction technique.

OBJECTIVE To clarify the spatial orientation relevant to the endoscopic sinus surgery (ESS) for the frontal sinus. METHODS Various dimensions of structures around the frontal recess were measured on 256 CT images of 128 Japanese patients using the multiplanar reconstruction technique. Measurements done in this study were: the distance from the nostril to the narrowest point of the frontal recess (D1), and the distance from the narrowest point of the frontal recess to the bony wall of the anterior skull base on an extension of the same line (D2). The smallest anterior-posterior (D3) and right-left (D4) diameters of the "route to the frontal sinus," a site containing the narrowest airspace in the frontal recess, being surrounded by the posterior edge of maxillary bone anteriorly, by the bony wall of the anterior skull base posteriorly, by the middle turbinate medially, and by the medial orbital bony wall laterally, respectively, on the parasagittal and coronal planes. The angle between the line connecting the nostril to the lowest portion of the frontal process of the maxilla and frontal bone, and the line connecting the lowest portion of the frontal process to the narrowest portion of the frontal recess (A1). RESULTS The mean values D1-D4 were 55.9, 9.4, 6.9 and 8.2mm. In 154 of 256 sides, A1 ranged from 129.5 degrees to 175.7 degrees. CONCLUSION The present study provides important information about the spatial anatomy of the nasofrontal recess, which is essential for avoiding complications of an ESS for the frontal sinus.