A New Paradigm: How to Study the Exact Location of a Paraclinoid Aneurysm and the Cavernous Sinus in the Preoperative Stage through Imaging

*Sérgio Tadeu Fernandes, Hugo Leonardo Dória-Netto and Edson Bernaldino Neto*

## **Abstract**

Intracranial aneurysms (IAs) found in the subarachnoid compartment of the internal carotid artery are at risk of rupturing and producing hemorrhage into this space, producing all the known serious pathological manifestations of subarachnoid hemorrhage. On the other hand, those who are exclusively in the intracavernous segment have this negligible risk. It is in this context that a peculiar class of IAs fits, the paraclinoid aneurysms, which are characterized by their complex anatomical relationships with the optic apparatus, anterior clinoid process, the first supraclinoidal arterial branches of the carotid artery, the oculomotor nerve and the segment mainly said clinoid, which is delimited by the proximal and distal dural rings. It is of crucial importance, and challenging, to determine the location of paraclinoid aneurysms and their exact relationship with the cavernous sinus, given the need to establish an adequate line of treatment for each case. Through preoperative studies of 3 t Magnetic Resonance, comparison with 3D bio models and microsurgical exploration, it was possible to accurately demarcate these anatomical relationships. Therefore, today it is possible to establish the accurate location of the paraclinoid aneurysm in relation to the cavernous sinus by means of MR images and to carry out an adequate, effective, and safe operative planning.

**Keywords:** paraclinoid, aneurysm, cavernous sinus, oculomotor, microsurgical anatomy
