[X-ray computed tomographic study of the ethmoid and middle meatus. II. Radio-anatomy (axial incidence) and morphological variations].

Chronic rhinosinusitis endoscopic surgery needs an accurate evaluation of diseases and paranasal sinus anatomic variations. High resolution CT by thin section (2 mm) allow this pre-operative assessment. An anatomical study of the ethmoid air cell system is always possible in axial plane. The bidimensional CT exploration (axial and coronal plane) displays the anatomic variations of ostiomeatal unit, that have been reported to predispose sinusitis. They are nasal septal deviation, pneumatization and paradoxical curvature of the middle turbinate, pneumatization of unciform process, Haller's cells, prominent agger nasi cell and ethmoid bulla. The endoscopic endonasal surgery landmarks, the individual morphologic variations, the topographic relations to the orbit and to the brain are also well shown by CT.