aneurysms at the origin of the posterior inferior cerebellar artery ( pica ) remain a challenge for neurosurgeons because the close proximity to the brainstem and lower cranial nerves poses a high risk for surgical clipping.1)14)15 ) aside from such anatomic unchangeability of adjacent structures , complex anatomic features of pica origin aneurysms themselves also add high risks for both surgical and endovascular treatments.16)19 ) however , in the past decade , there have been substantial advances in device technologies and endovascular techniques . as a result , the number of patients who are not candidates for endovascular treatment is decreasing . in particular , the " self expanding stent technology " and " supercompliant balloon technology " have revolutionized the methods and results of endovascular treatment.14)22 ) combining a self expanding stent with a " cross - over technique " , which uses an inter - arterial communication as an access route to the other vascular part,9)12 ) the authors herein report on a bilateral approach for stent - assisted coiling of two complex pica origin aneurysms . a 71-year - old woman who had no past medical history presented to our emergency room with a sudden thunderclap headache , nausea , and vomiting . on neurological examination , the score on the glasgow coma scale was 11 ( e3v3m5 ) and isocoric pupil response was observed . initial computed tomography ( ct ) and ct angiography showed fischer grade 4 subarachnoid hemorrhage ( sah ) and a ruptured left pica aneurysm ( fig . cerebral angiography and 3d image reconstruction showed a left pica origin aneurysm measuring 7 mm in length with a dome to neck ratio of 0.7 and pica incorporation into the sac ( fig . 1c and 1d ) . as a treatment option , in view of anticipated surgical difficulty and patient 's preference , our neurovascular team decided on endovascular treatment . the use of a multi - catheter or balloon remodeling technique is likely to have a high risk of pica occlusion during coil embolization of this complex aneurysm ; therefore , coiling with placement of a stent in the vertebral artery ( va)-aneurysm - pica path was planned . however , an antegrade approach to the pica appeared to be very difficult and too risky , so a retrograde approach via the contralateral va was decided . for selection of the left pica arising from the aneurysm , a 6f guiding catheter was placed in the right va , an excelsior sl-10 microcatheter ( striker , fremont , ca ) was introduced into the right va via the guiding catheter to cross over the vertebrovertebral junction to the left va , and the microcatheter over a synchro-14 guidewire ( striker , fremont , ca ) was able to select the left pica smoothly ( fig . after being placed in the left pica , the excelsior microcatheter was exchanged for a rebar-18 microcatheter ( ev3 inc , irvine , ca ) that was compatible with a stent delivery system . another 6f guiding catheter was introduced into the left va and an excelsior sl-10 microcatheter was placed in that aneurysm through the guiding catheter for coil delivery . the right vertebral artery was non - dominant and smaller than the left vertebral artery . however , the size of the right vertebral artery was sufficient to accept the rebar-18 microcatheter . after deployment of a solitaireab stent ( ev3 inc , irvine , ca ) for protection of the pica ( fig . 1f ) , a total of eight detachable coils were packed in the aneurysm . as only a 20-mm - long stent ( 4  20 ) was available at that time , it covered the left pica , aneurysm neck , left va , and a short segment of the right va , in order . the patient received dual anti - platelet therapy for 30 days , and continued life - long aspirin . at the four - month follow - up evaluation , a previously healthy 43-year - old man visited our emergency room complaining of a severe headache for six hours . except for nuchal rigidity , brain ct showed right premedullary sah and minimal intraventricular hemorrhage mainly in the fourth ventricle , three - dimensional ct angiography showed a ruptured right pica origin aneurysm , and cerebral angiography was successively performed for visualization of anatomic details of the aneurysm . it had a maximal size of 11 mm and a low dome - to - neck ratio of 0.9 , and gave rise to the pica , which was incorporated into the sac ( fig . aiming at both aneurysm occlusion and pica preservation , coiling with placement of a stent in the va - aneurysm - pica path was considered the best method . all procedural steps were similar to those of case 1 , except for the use of two micro - catheters for coil delivery and use of a 4  22 mm enterprise stent . after placement of the first two coils , eliminating contrast filling of the aneurysm dome , systemic heparinization ( 3,000 iu ) was administered intravenously . however , thrombosis occurred in the aneurysm neck during placement of the last coil , which resulted in near occlusion of the pica flow . tirofiban was given as an intraarterial bolus of 0.5 mg over five minutes , resulting in recanalization of the occluded pica . 2b ) , no progressive thrombosis was observed and the pica flow was intact , so that the patient was awakened . on neurological examination , no neurological deficit was identified immediately or at one month after the procedure . the patient received dual anti - platelet therapy for 30 days , but was lost to follow - up afterwards . a 71-year - old woman who had no past medical history presented to our emergency room with a sudden thunderclap headache , nausea , and vomiting . on neurological examination , the score on the glasgow coma scale was 11 ( e3v3m5 ) and isocoric pupil response was observed . initial computed tomography ( ct ) and ct angiography showed fischer grade 4 subarachnoid hemorrhage ( sah ) and a ruptured left pica aneurysm ( fig . cerebral angiography and 3d image reconstruction showed a left pica origin aneurysm measuring 7 mm in length with a dome to neck ratio of 0.7 and pica incorporation into the sac ( fig . 1c and 1d ) . as a treatment option , in view of anticipated surgical difficulty and patient 's preference , our neurovascular team decided on endovascular treatment . the use of a multi - catheter or balloon remodeling technique is likely to have a high risk of pica occlusion during coil embolization of this complex aneurysm ; therefore , coiling with placement of a stent in the vertebral artery ( va)-aneurysm - pica path was planned . however , an antegrade approach to the pica appeared to be very difficult and too risky , so a retrograde approach via the contralateral va was decided . for selection of the left pica arising from the aneurysm , a 6f guiding catheter was placed in the right va , an excelsior sl-10 microcatheter ( striker , fremont , ca ) was introduced into the right va via the guiding catheter to cross over the vertebrovertebral junction to the left va , and the microcatheter over a synchro-14 guidewire ( striker , fremont , ca ) was able to select the left pica smoothly ( fig . after being placed in the left pica , the excelsior microcatheter was exchanged for a rebar-18 microcatheter ( ev3 inc , irvine , ca ) that was compatible with a stent delivery system . another 6f guiding catheter was introduced into the left va and an excelsior sl-10 microcatheter was placed in that aneurysm through the guiding catheter for coil delivery . the right vertebral artery was non - dominant and smaller than the left vertebral artery . however , the size of the right vertebral artery was sufficient to accept the rebar-18 microcatheter . after deployment of a solitaireab stent ( ev3 inc , irvine , ca ) for protection of the pica ( fig . 1f ) , a total of eight detachable coils were packed in the aneurysm . as only a 20-mm - long stent ( 4  20 ) was available at that time , it covered the left pica , aneurysm neck , left va , and a short segment of the right va , in order . the patient received dual anti - platelet therapy for 30 days , and continued life - long aspirin . at the four - month follow - up evaluation , a previously healthy 43-year - old man visited our emergency room complaining of a severe headache for six hours . except for nuchal rigidity , brain ct showed right premedullary sah and minimal intraventricular hemorrhage mainly in the fourth ventricle , three - dimensional ct angiography showed a ruptured right pica origin aneurysm , and cerebral angiography was successively performed for visualization of anatomic details of the aneurysm . it had a maximal size of 11 mm and a low dome - to - neck ratio of 0.9 , and gave rise to the pica , which was incorporated into the sac ( fig . aiming at both aneurysm occlusion and pica preservation , coiling with placement of a stent in the va - aneurysm - pica path was considered the best method . all procedural steps were similar to those of case 1 , except for the use of two micro - catheters for coil delivery and use of a 4  22 mm enterprise stent . after placement of the first two coils , eliminating contrast filling of the aneurysm dome , systemic heparinization ( 3,000 iu ) was administered intravenously . however , thrombosis occurred in the aneurysm neck during placement of the last coil , which resulted in near occlusion of the pica flow . tirofiban was given as an intraarterial bolus of 0.5 mg over five minutes , resulting in recanalization of the occluded pica . 2b ) , no progressive thrombosis was observed and the pica flow was intact , so that the patient was awakened . on neurological examination , no neurological deficit was identified immediately or at one month after the procedure . the patient received dual anti - platelet therapy for 30 days , but was lost to follow - up afterwards . pica origin aneurysms frequently have unfavorable anatomic findings , including a wide neck and pica incorporation into the sac.1)10)14 ) endovascular treatment of such aneurysms is associated with risk for pica occlusion or procedural failure . although special techniques have recently been addressed,6)8 ) two goals of aneurysm occlusion and pica preservation appear to be mostly secured by stent - assisted coiling , where a self expanding stent successively covers the pica , aneurysm neck , and va . however , in the case of pica incorporation , selecting the pica antegrade through the ipsilateral va is extremely difficult and risky . anatomy - wise , if the contralateral va were non - interrupted and large enough to accept a catheter , a contralateral and retrograde approach to the pica would be easier than the ipsilateral antegrade one . a few case studies regarding the " cross - over technique " using the communicating artery or vertebrovertebral junction as an access route have been reported in the literature.5)9 ) moret et al.14 ) suggested that the anatomic benefits afforded by this technique outweigh the potential risks associated with catheterization of another major cerebral artery . we believe that , in two cases in this study , without stent - assisted coiling using the " cross - over technique " , pica occlusion would have been inevitable . however , long - term follow - up results of this procedure are not available . in particular , the size of the pica is so variable that the issue of long - term stent patency remains unanswered . after far - lateral suboccipital exposure , pica origin aneurysms can be approached between the 11 cranial nerve inferiorly and the ninth and tenth cranial nerves superiorly . therefore , the 10 and 11 cranial nerves are at risk of injury during the operation , which can result in lower cranial nerve dysfunction.3)7)10)15 ) in addition , complex aneurysmal geometry may make it difficult for neurosurgeons to complete aneurysm clipping without occlusion of the pica . occlusion of the pica close to its origin may lead to serious morbidity and mortality , depending on the distribution of the medullary perforators and the presence of collateral supply from other cerebellar arteries . aneurysm clipping following occipital artery - pica bypass surgery may be a solution to this serious complication,2)19)20 ) however , it is too early to generalize the staged treatments . due to recent instrumental and technical developments leading to good results , endovascular treatment is considered the primary treatment for posterior circulation aneurysms . however , complex pica aneurysms , having a wide neck and pica incorporation , remain a challenge for both surgical and endovascular treatments . in such cases , a bilateral approach for
aneurysms of the posterior inferior cerebellar artery ( pica ) are rarely encountered . in particular , due to frequent anatomic complexity and the presence of nearby critical structures , pica origin aneurysms are difficult to treat . 
 however , recent reports of anecdotal cases using advanced endovascular instruments and skills have made the results of endovascular treatment rather outstanding . 
 pica preservation is the key to a successful endovascular treatment , based on the premise that a pica origin aneurysm is well occluded . to secure pica flow , stenting into the pica 
 would be the best method , however , it is nearly impossible technically via the ipsilateral vertebral artery ( va ) if the pica arose at an acute angle from the sac . in such a case , a bilateral approach for stent - assisted coiling can be a creative method for achievement of two goals of both aneurysm occlusion and pica preservation : ipsilateral approach for coil delivery and contralateral cross - over approach for stent delivery via a retrograde smooth path into the pica .