Introduction: Superiorly projecting (SP) Anterior Communicating Artery (AcomA) aneurysms are described in the literature as a homogenous group. Clinically and microsurgically, these aneurysms vary in multiple important characteristics. We propose a new microsurgical classification system for these complex aneurysms and review its implications regarding presentation, microsurgical techniques and outcome.
Methods: This retrospective analysis is based on data of patients (2005-2013) undergoing clipping of SP AcomA aneurysms. The classification system is based on the virtual 2D microsurgical spatial plane created by the proximal A2 segments and its relationship to the aneurysm within the superior quadrant. (Figs. 1, 2). Determination of aneurysm type was assessed by intraoperative observations and images. Type 1 classification is defined by bisection of the aneurismal dome by the A2 plane. Type 2 is defined by dome projection posterior to this plane. Sagittal rotation of the plane defines Types 3a, b. (Figs. 3-6). We analyzed clinical presentation, aneurysmal morphology, angiographic characteristics, intra-operative technique and outcome in respect to classification types. Neurological outcomes were assessed using the GOS, and patient outcomes were expressed in terms of changes from preoperative baseline.
Results: There were 43 SP AcomA aneurysms. 3D angiographic images predicted classification type in 78%. Type 1 aneurysms presented more often with SAH (95.7%, P<0.05). There was no statistical significant difference between the types regarding patient demographics or aneurysm morphology, size, neck or dome/neck ratio. Distinct micro-dissection techniques apply to each type. Fenestrated clips were used frequently in Type 2 aneurysms (86% p=0.0032); these clips were not appropriate for type 3A. Patients with Type 2 lesions experienced higher rate of neurological worsening (57.1% p=0.046), as well as high mortality rate (46%).
Conclusions: The proposed classification system for SP AcomA aneurysms has significant implications regarding surgical planning, micro-dissection, clipping, and outcome and may be a determinate for endovascular treatment in selected cases.
Patient Care: The proposed classification system has important implications on pre operative microsurgical planning and on intra operative micro-dissection and clipping techniques. The classification system may be a determinant for endovascular treatment in selected cases.
Learning Objectives: By the conclusion of this session, participants should be able to describe the importance of the subtypes of superiorly projecting AcomA aneurysms relative to anatomy, surgical technique and outcome