Morphological aspects of blister aneurysms and nuances for surgical treatment

Object Blister aneurysms of the supraclinoid part of the internal carotid artery (ICA) are known for their high morbidity
and mortality rates related to treatment, regardless of whether the treatment is surgical or endovascular. However, this
grim prognosis is based on results that indiscriminately group all blister aneurysms together without taking into account
the heterogeneous appearance of these lesions. The goal of this study was 2-fold: to determine whether different blister
aneurysm morphologies present different pitfalls, which would then require different surgical strategies, as well as to
determine whether there are identifiable subgroups of these types of aneurysms based on morphology.
Methods The authors reviewed the charts, cerebral catheter angiograms, surgical reports, and intraoperative videos
of all ICA blister aneurysms treated surgically at the Centre Hospitalier de l’Université de Montréal from 2005 to 2012 to
investigate whether there was a relationship between morphology and pitfalls, and whether different surgical strategies had
been used according to these pitfalls. During this review process the authors noted 4 distinct morphological aspects. These
4 aspects led to a review of the English and French literature on blister aneurysms in which imaging was available, to determine
whether other cases could also be classified into the same 4 subgroups based on these morphological aspects.
Results The retrospective review of the authors’ series of 10 patients allowed a division into 4 distinct subtypes:
Type I (classic), Type II (berry-like), Type III (longitudinal), and Type IV (circumferential). These subtypes may at times
be progressive stages in the arterial anomaly, and could represent a continuum. Each subtype described in this paper
presented its own pitfalls and required specific surgical adaptations. Upon reviewing the literature the authors retained
35 studies involving a total of 61 cases of blister aneurysms, and all cases were able to be classified into 1 of these 4
distinct subtypes.
Conclusions Although they share some common characteristics, blister aneurysms may be divided into distinct subtypes,
suggestive of a continuum. Such a classification with a detailed description of each type of blister aneurysm would
allow for better recognition to anticipate complications during intervention and better assess the different treatment strategies
according to the subtypes.
http://thejns.org/doi/abs/10.3171/2014.11.JNS141004
Key Words blister aneurysm; clipping; subarachnoid hemorrhage; cerebral aneurysm morphology; vascular
disorders; surgical technique