1171. Pathogenesis of Dorsal Internal carotid artery Wall aneurysms Based on Histopathologic Examination and Microscopic Configuration

Authors: Jae Seung Bang, MD; Si Un Lee, MD; Chang Wan Oh, MD; O-Ki Kwon, MD; Gheeyoung Choe, MD; Hyoung Soo Byoun, MD; Jae Seung Bang, MD (Seoul, Republic of Korea)

Introduction> There have not been reported about the “pathology of biopsy cases” of blood blister-like aneurysm of dorsal internal carotid (ICA) wall, so the pathogenesis of such a vascular lesion remains uncertain. We first report about the biopsy pathology (not autopsy) of blood-blister-like aneurysm in two cases of ruptured dorsal ICA aneurysms. Methods> A 63-year-old woman and a 42-year-old man developed a fatal subarachnoid hemorrhage caused by the rupture of a blister-like aneurysm at the dorsal wall of the internal carotid artery. The 63-year-old woman had “superficial temporal artery (STA)-radial artery (RA)-M2 bypass and surgical trapping of ICA”. The 42-year-old man had “common carotid artery (CCA)-RA-M2 bypass and surgical trapping of ICA”. In all two cases, we obtained the pathologic specimen of ICA with blister-like aneurysm and investigated the pathologic structures. Results> BBA specimens including the adjacent internal carotid artery (ICA) walls were obtained intraoperatively. Based on the pathologic findings of these specimens, we suggest two types of BBAs, type I (sessile type-like an earthquake) and type 2 (intermediate type-like a volcano). The characteristics of type I is “intramural hematoma” caused by “dissection” and “hematoma plug”, and the characteristics of type II is “no intramural hematoma”, because of “no-dissection” and “fibrinous plug”. Because of pathologic difference, clipping on the wrap technique is originally possible in type II BBA, but impossible in type I BBA. Conclusions> This is the first report that described the pathogenesis of BBAs on the basis of histopathologic examination of biopsy specimens and intraoperative findings. However, further histopathologic reports are required to support our findings.