[Prevention of vascular complications in endonasal paranasal sinus surgery. I: Anatomic principles and surgical significance].

Anatomic and histologic investigations were performed in 59 cadaver half-heads in order to demonstrate areas of hazard at the posterior skull base during endoscopic surgery and determine morphologic features of surgical relevance. In 78% of the heads the internal carotid artery bulged into the sphenoid sinus from laterally directly behind and beyond the tuberculum for the optic nerve ("anterior bulging"). In 25% of all cases the carotid artery also bulged into the sphenoid sinus from behind ("posterior bulging"). This bulging could amount to as much as 7 mm. Additionally, the thickness of the bony wall at the point of the largest prominence could be very thin (0.1 mm), with 12% of all cases showing bony dehiscences. The width of the posterior ethmoid cells and pneumatization of the paranasal sinuses at this point differed widely, ranging from 8-24 mm. Classification of the carotid loop into five different types demonstrated that the bulgings of the internal carotid artery were larger in more curved types of the artery ("omega" and "U" types) and were smaller in less curved types ("Arkus" and "V" types).