The "rete mirabile" of the clivus and the dorsum sellae. A microanatomical study.

The osteofibrous space underneath the dura mater of the dorsoclival area was studied with respect to the arterial branches arising from the internal carotid artery at this level. Special attention was given to the main variations of branching and anastomosing patterns found in this area. Our results indicate that the meningohypophyseal trunk is the main supplier of the dorsoclival area. The dorsal meningeal artery was present in all cases. In the course of this vessel three main variations were observed. The inferior hypophyseal and the tentorial artery also contributed to the arterial supply of this region. A large number of anastomoses between the internal and external carotid artery was present as well. Because of the refinement of microsurgical and interventional techniques pathological lesions like tumors and vascular malformations of the dorsoclival area are frequently accessible. The knowledge of the microvascular anatomy of the clivus and the dorsum sellae is important as the rich collateral network found in this area may contribute to the arterial supply of pathological lesions arising here.