[Atypical pneumatization of the paranasal sinus system].

200 CT scans of adult patients with paranasal sinus problems seen in the ENT Department either in the University Hospital in Berne, Switzerland, or in the University Hospital in Munich, Germany, were analysed. Among these we found 9 striking abnormalities of paranasal sinus anatomy. We found abnormalities which caused clinical symptoms, such as an infected concha bullosa, a fine-septated infected maxillary sinus, a pneumosinus dilatans of the frontal sinus with aesthetic problems, and a cellula orbito-ethmoidalis with sinusitis. Some of these abnormalities were found by coincidence, such as a cellula orbito-sphenoidalis and an extreme pneumatisation of the sinus sphenoidalis with a pneumatised processus pterygoideus. 2 cases show the importance of preoperative evaluation of a possible abnormal sinus to avoid operative complications: a sinus sphenoidalis with a pneumatisated clivus and an intraluminal a. carotis interna. The other case involved an optic nerve running free through the sphenoidal sinus. In conclusion we stress the importance of preoperative CT examination and the choice of a coronary or axial CT scan, which reveals any abnormal anatomy of the paranasal sinus pneumatisation and thus increases the safety and efficiency of paranasal sinus surgery.