RESUMO
One hundred cases with pneumatized sphenoid sinus were studied, based on the cranial X-ray film, sagittal tomograms and coronal CT scan as well as the observation during the course of operation. A new bilateral combination classification scheme was suggested and used in this study. It was shown that the identical type was 58% and non-identical, 42% and the former could be further divided into 5 subtypes and the latter, 10 subtypes. The incidence of supra-sphenoid-ethmoidal cell (SSEC) was 22%. Some of SSEC may be mistaken for sphenoid sinus, if the surgeons are not familiar with its anatomy. We emphasize that the bilateral combination classification is very important for selecting a suitable method from among different trans-naso-sphenoid approaches.