Radiologic anatomy of the paranasal sinuses

The anatomy of the paranasal sinuses is complex and variable, changing from patient to patient, and even from side to side in the same patient. This complexity results from the variable patterns of sinus ventilation and drainage dictated by independent sinus development. Sinus ventilation and drainage determines intrasinus mucociliary health, which also determines the effi ciency of sinus growth and pneumatization. The fi nal individual sinus confi guration is additionally infl uenced by the evolving growth of neighboring sinuses, competing for space as they pneumatize the facial bones and skull base, also in competition with erupting teeth in the maxilla and the ever-constant intracranial pressure gradients along the skull base. The complex interaction of all these factors over time dictates an endless combination of anatomic variations that force the rhinologist to evaluate each side of the face as a completely independent anatomic, functional and surgical entity. Recent signifi cant advances in computed tomography (CT), especially the introduction of multidetector helical scanning and the routine availability of computer workstations, have made demonstration of this complex anatomy easier and more useful to rhinologic surgical planning. This improvement in imaging clarity and multiplanar demonstration of sinus complex anatomy is now of even more clinical relevance in view of the extensive developments in powered instruments, better endoscopic devices and surgical navigation with CT cross-registration.