institutional review board approval was obtained , with informed consent being waived . from july 2002 to september 2013 , a total of 42 patients having 45 vadas were treated with endovascular treatment at single institution . the study group consisted of 23 males and 19 females ( mean age , 52 years ; age range , 36 to 80 years ) . of the 45 vadas , decision of endovascular treatment method was based on the angiographic characteristics of vadas , presence or absence of sah , and clinical presentations . internal trapping by detachable coils was primarily considered when the vada was located in proximal or distal to origin site of pica . stent implantation or stent - assisted coil embolization was considered in cases of unruptured aneurysms with posteroinferior cerebellar artery ( pica ) involvement . as a result , various endovascular strategies were used : internal trapping with coils ( n=26 ) , stent - assisted coil embolization ( n=14 ) , and stent implantation only ( n=5 ) . the diagnosis of vada was based on the characteristic appearances revealed on mra , computed tomography angiography ( cta ) or conventional angiography . vada was located in right vertebral artery in 28 cases and in left vertebral artery in 17 cases . involved vertebral artery was dominant artery in 10 cases and non - dominant in 19 cases . 19 vadas were located distal to the origin of pica , 18 vadas were proximal to that of pica , and 8 vadas were pica involvement type . immediate angiographic results were classified as complete or incomplete occlusion based on the completion angiography . follow - up angiographic results were evaluated with cta , mra , or dsa more than 3 months later . these results were classified as complete occlusion , antegrade recanalization , no change , complete occlusion with vessel remodeling , and recanalization . the clinical data was reviewed retrospectively by a neurologist using the hunt and hess grading system ( h&h grade ) and modified rankin scale ( mrs ) at 3-months . clinical outcomes were assessed at 3months after endovascular treatment . in patients with unruptured vada , institutional review board approval was obtained , with informed consent being waived . from july 2002 to september 2013 , a total of 42 patients having 45 vadas were treated with endovascular treatment at single institution . the study group consisted of 23 males and 19 females ( mean age , 52 years ; age range , 36 to 80 years ) . of the 45 vadas , decision of endovascular treatment method was based on the angiographic characteristics of vadas , presence or absence of sah , and clinical presentations . internal trapping by detachable coils was primarily considered when the vada was located in proximal or distal to origin site of pica . stent implantation or stent - assisted coil embolization was considered in cases of unruptured aneurysms with posteroinferior cerebellar artery ( pica ) involvement . as a result , various endovascular strategies were used : internal trapping with coils ( n=26 ) , stent - assisted coil embolization ( n=14 ) , and stent implantation only ( n=5 ) . the diagnosis of vada was based on the characteristic appearances revealed on mra , computed tomography angiography ( cta ) or conventional angiography . vada was located in right vertebral artery in 28 cases and in left vertebral artery in 17 cases . involved vertebral artery was dominant artery in 10 cases and non - dominant in 19 cases . 19 vadas were located distal to the origin of pica , 18 vadas were proximal to that of pica , and 8 vadas were pica involvement type . immediate angiographic results were classified as complete or incomplete occlusion based on the completion angiography . follow - up angiographic results were evaluated with cta , mra , or dsa more than 3 months later . these results were classified as complete occlusion , antegrade recanalization , no change , complete occlusion with vessel remodeling , and recanalization . the clinical data was reviewed retrospectively by a neurologist using the hunt and hess grading system ( h&h grade ) and modified rankin scale ( mrs ) at 3-months . clinical outcomes were assessed at 3months after endovascular treatment . in patients with unruptured vada , favorable outcome was defined as mrs 0 and 1 . of 17 ruptured vadas , 5 cases initially presented with poor grades ( 4 or 5 ) , 8 cases with grade 3 , 2 cases with grade 2 , and 1 patient with grade 1 . results of immediate and follow up imaging studies in ruptured vadas are presented in the table . in ruptured cases ( n=17 ) , endovascular treatment consisted of internal trapping with coil embolization ( n=13 ) and stent - assisted coil embolization using self - expandable stent ( n=4 ) . immediate angiographic results revealed complete occlusion in 14 cases and incomplete occlusion in 3 cases . follow up imaging study in 7 cases treated with internal trapping revealed complete occlusion in 6 cases and antegrade recanalization in 1 case ( fig . follow up imaging studies showed no change in 1 case and complete occlusion with vessel remodeling in 1 case ( fig . 2 ) . there were 6 procedure - related complications : lateral medullary infarction ( n=2 ) , embolic infarction ( n=2 ) , unintended arterial occlusion ( n=1 ) , and parent artery dissection ( n=1 ) . favorable outcome ( mrs 0 and 1 ) was achieved in 5 patients and poor outcome in 8 patients . of 28 unruptured vadas , 25 vadas initially presented with headache , 2 with hemiparesis , and 1 with lateral medullary infarction . results of immediate and follow - up imaging studies in unruptured vadas are presented in table . in unruptured cases , internal trapping was performed in 13 cases , stent - assisted coil embolization in 10 cases , and stent implantation only in 5 cases . all vadas treated with internal trapping showed complete occlusion on immediate post - procedural angiography . immediate angiographic results in 10 cases treated with stent - assisted coliling showed complete occlusion in 4 cases and incomplete occlusion in 6 cases . follow - up angiographic studies were available in 22 cases . in 9 cases treated with internal trapping , complete occlusion occurred in 8 cases and antegrade recanalization in 1 case . in 9 cases treated with stent - assisted coil embolization , complete occlusion with vessel remodeling occurred in 3 cases , no change in 5 cases , and recanalization in 1 case . of these , a patient with recanalization on follow - up after stent - assisted coil embolization underwent retreatment with internal trapping using detachable coils ( fig.3 ) . in cases treated with stenting only , 4 ) , decrease of sac in size in 1 case , and no change in 1 case . favorable outcome ( mrs 0 - 1 ) was achieved in 26 cases and poor outcome ( mrs 2 - 5 ) in 2 cases . of 17 ruptured vadas , 5 cases initially presented with poor grades ( 4 or 5 ) , 8 cases with grade 3 , 2 cases with grade 2 , and 1 patient with grade 1 . results of immediate and follow up imaging studies in ruptured vadas are presented in the table . in ruptured cases ( n=17 ) , endovascular treatment consisted of internal trapping with coil embolization ( n=13 ) and stent - assisted coil embolization using self - expandable stent ( n=4 ) . immediate angiographic results revealed complete occlusion in 14 cases and incomplete occlusion in 3 cases . follow up imaging study in 7 cases treated with internal trapping revealed complete occlusion in 6 cases and antegrade recanalization in 1 case ( fig . follow up imaging studies showed no change in 1 case and complete occlusion with vessel remodeling in 1 case ( fig . 2 ) . there were 6 procedure - related complications : lateral medullary infarction ( n=2 ) , embolic infarction ( n=2 ) , unintended arterial occlusion ( n=1 ) , and parent artery dissection ( n=1 ) . favorable outcome ( mrs 0 and 1 ) was achieved in 5 patients and poor outcome in 8 patients . of 28 unruptured vadas , 25 vadas initially presented with headache , 2 with hemiparesis , and 1 with lateral medullary infarction . results of immediate and follow - up imaging studies in unruptured vadas are presented in table . in unruptured cases , internal trapping was performed in 13 cases , stent - assisted coil embolization in 10 cases , and stent implantation only in 5 cases . all vadas treated with internal trapping showed complete occlusion on immediate post - procedural angiography . immediate angiographic results in 10 cases treated with stent - assisted coliling showed complete occlusion in 4 cases and incomplete occlusion in 6 cases . follow - up angiographic studies were available in 22 cases . in 9 cases treated with internal trapping , complete occlusion occurred in 8 cases and antegrade recanalization in 1 case . in 9 cases treated with stent - assisted coil embolization , complete occlusion with vessel remodeling occurred in 3 cases , no change in 5 cases , and recanalization in 1 case . of these , a patient with recanalization on follow - up after stent - assisted coil embolization underwent retreatment with internal trapping using detachable coils ( fig.3 ) . in cases treated with stenting only , complete occlusion with vessel remodeling occurred in 2 cases ( fig . 4 ) , decrease of sac in size in 1 case , and no change in 1 case . favorable outcome ( mrs 0 - 1 ) was achieved in 26 cases and poor outcome ( mrs 2 - 5 ) in 2 cases . primary mechanism of the arterial dissection is disruption of the internal elastic lamina . after disruption , leukocyte and macrophage infiltration , endothelial coverage , and neointima formation follow subsequently . ruptured vada shows high incidence ( over 70% ) of rebleeding within 24 hours which results in poor clinical outcome [ 3 , 9 , 10 ] . two main concepts in the endovascular treatment of the vada are deconstructive and reconstructive techniques for the parent vessels . first , deconstructive techniques can be performed by balloon or coil embolization [ 11 , 12 , 13 , 14 , 15 , 16 ] . multiple studies regarding direct occlusion of the pathologic segment were reported [ 17 , 18 ] . however , there were several case reports of antegrade recanalization after endovascular treatment for ruptured vadas [ 19 , 20 ] . the mechanism of the antegrade recanalization can be explained as following ; ( 1 ) if microcatheter navigate into the false lumen and occlude the false lumen with detachable coils , true lumen dilates into the normal diameter as false lumen collapses ( 2 ) . detachable coils were insufficient to cover the entry of the dissecting aneurysm . in our case , there was one ruptured vada case which showed antegrade recanalization 6 months after internal trapping ( fig . 1 ) . especially in case of vada involving pica in dominant side , alternative technique such as proximal occlusion can be considered . however , proximal occlusion technique can cause retrograde flow from the contralateral vertebral artery resulting in rebleeding . in our study , although there were 8 cases of vadas involving picas , none of those was treated in proximal occlusion technique . canton et al .   and lopes et al .   reported the mechanism of endovascular stent deployment in vada . they suggested flexible stents reduces the stresses acting on the aneurysm wall which results in true lumen expansion and parent artery reconstruction finally . histologically , complete endothelialization of the stent and fibroelastic tissue formation along the aneurysmal neck explain mechanism of the stent deployment strategy . in recent reports , outcome of endovascular treatment with stenting in ruptured or unruptured vada is favorable . although unruptured vadas usually show benign clinical course , the natural course of the unruptured vadas is still unknown and treatment guideline remains controversial . administration of antiplatelet or anticoagulant in patients with unruptured vadas and ischemic presentations may exacerbate aneurysmal dissection and cause rupture of the aneurysm . risk of bleeding from unruptured vada was higher than previous reports and endovascular treatment should be considered in some cases , such as in cases of increased size of aneurysmal dilatation during follow - up period and when double lumen sign is visible in the acute stage . for making a decision of parent artery occlusion in cases of unruptured vada , there are several factors to be considered : risk of bleeding in conservative treatment ; risk of ischemic complications during procedure ; blood supply from the anterior and posterior spinal artery , perforating arteries , and patency of contralateral vertebral artery ; and relationship between aneurysm and pica . reconstructive techniques , stent placement with or without coil embolization , aims at the preservation of the vertebral artery flow . this technique , as well as parent artery occlusion , show favorable results in unruptured vada cases according to several reports [ 4 , 23 ] . in our study , clinical and radiologic results were satisfactory in upruptured patients treated with internal trapping and stent placement with or without coils . only one case revealed recanalization of the dissecting aneurysm after 1 year , which was retreated with internal trapping ( fig . although pica has rich pial anastomoses , there have been case reports of pica infarction on follow up images after endovascular procedure . they suggested that thromboembolism due to coil loop herniation into the pica origin and occlusion of a perforating artery was possible causes of the pica territory infarction . however , as well as procedural complication , recurrent ischemia in unruptured vada patients may be attributable to thrombotic occlusion of the stenotic lesion , distal emboli , to further occlusion of perforating arteries originating from the va due to progression of the dissection . the major limitations of our study were the small number of cases and the retrospective nature of the study . in conclusion , endovascular treatment of vada appears to be safe and effective in both ruptured and unruptured cases . follow - up angiographic study is needed because parent artery recanalization or aneurysmal recurrence can occur .
purposeto report angiographic and clinical results of endovascular treatment in 45 intracranial vertebral artery dissecting aneurysms ( vadas).materials and methodsfrom july 2002 to september 2013 , a total of 42 patients with 45 vadas received endovascular treatment . 
 endovascular treatment consisted of internal trapping with detachable coils , stent - assisted coiling , and stenting only . 
 immediate and follow - up angiographic findings and clinical outcome were retrospectively reviewed.resultsthere were 17 ruptured vadas and 28 unruptured vadas . 
 overall , 26 vadas were treated with internal trapping , 14 with stent - assisted coil embolization , and 5 with stenting only . 
 immediate angiographic results revealed complete occlusion in 31 cases and incomplete occlusion in 14 cases . 
 follow - up imaging studies were available in 31 cases . on follow - up 
 imaging , antegrade recanalization occurred in 2 of 16 cases treated with internal trapping . 
 aneurysmal recurrence occurred in one case treated with stent - assisted coiling . 
 procedural complications occurred in 8 patients . in cases of unruptured vada , favorable outcome ( 
 mrs 0 and 1 ) was achieved in 26 cases and poor outcome ( mrs 2 - 5 ) in 2 cases . 
 there was no mortality in patients with unruptured vadas.conclusionendovascular treatment of intracranial vada appears to be safe and effective . 
 follow - up angiographic study is needed because parent artery recanalization or aneurysmal recurrence can occur .