Study on the angiographic classification of internal carotid artery paraclinoid aneurysms

Background There are a variety of nomenclatures and classification systems of paraclinoid aneurysms, most of which have been proposed for neurosurgical purpose . This article aims to develop an improved classification method which can be used during endovascular management on paraclinoid aneurysms and to summarize the main nomenclatures and classification systems of paraclinoid aneurysms. Methods One hundred and twenty-six patients with 142 saccular paraclinoid aneurysms, who were treated with endovascular embolization in our hospital during January 2009 to December 2011, were tried to be classified as Type Ⅰ(ophthalmic artery aneurysms) and Type Ⅱ(superior hypophyseal artery aneurysms). Each type was further divided into two subtypes according to their relative position to an imaginary bisector that separated ophthalmic artery and posterior communicating artery. Among the four subtypes, Type Ⅰa and Ⅱa referred to aneurysms arising from internal carotid artery (ICA) proximal to the bisector, while Type Ⅰb and Ⅱb referred to aneurysms arising from ICA distal to the bisector. Results All of the 142 paraclinoid aneurysms were classified successfully. According to our classification system, there were 45 aneurysms belonging to Type Ⅰa, accounting for 31.69% ( 45/142 ), and 11 aneurysms belonging to Type Ⅰb, accounting for 7.75% (11/142 ). Besides, 78 aneurysms were TypeⅡa, accounting for 54.93% (78/142 ), and 8 aneurysms were Type Ⅱb, accounting for 5.63% (8 /142 ). Conclusion A number of classification systems have been proposed by different groups. It is important to choose suitable classification method in clinical practice, so as to formulate optimal treatment strategy.