The intravenous (IV) administration of recombinant tissue plasminogen activator (rtPA), which is supported by the highest level of scientific evidence, continues to be the gold standard for the treatment of acute ischemic stroke following a major vessel occlusion. Nevertheless, not all patients are eligible to receive IV rtPA, and rates of recanalization remain greatly variable depending on the site of occlusion. The advent of endovascular treatment appeared as a very attractive alternative for those who had failed, or were ineligible for, IV rtPA. In addition to the preexisting endovascular treatment modalities such as local fibrinolytic therapy and balloon angioplasty / stenting, mechanical thrombectomy has been incorporated in the treatment options to restore cerebral perfusion to the downstream region. Merci^® Retriever and Penumbra System^® were approved by the United States Food and Drug Administration (FDA), for the treatment of acute ischemic stroke in 2004 and 2008, respectively. Likewise, Merci^® Retriever and Penumbra^® received an approval by the Japanese Ministry of Health, Labor and Welfare in 2010 and 2011, respectively. The endovascular treatment of acute ischemic stroke has ushered in a new age of multipledevices, whereby the selection of an appropriate device becomes vital. In this article, the authors present clinical cases, in which Merci^® Retriever (a device that applies force to the distal base of the thrombus), Penumbra System^® (a device that applies force to the proximal base of the thrombus), stent-retriever (a device meant to be placed across the thrombus), direct angioplasty and permanent stent placement, and local fibrinolytic injections were utilized. The theoretical advantages and disadvantages of these devices and treatment modalities were also discussed in the clinical case presentations. The poor overall outcome associated with nonrecanalized major vessel occlusion is well recognized. Proper indication and successful recanalization of the occluded vessel are the keys to achieve the good clinical outcome. Newer generation devices are not necessarily associated with a higher recanalization rate. It is appropriate device selection based on the functional mechanism and the type of the occlusion that enables a higher rate of recanalization.

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Objective: Treatment of very small cerebral aneurysms remains challenging. The aim of the present study was to assess the feasibility and safety of endovascular treatment for these aneurysms.
Methods: Between 2003 and 2008, a total of 831 aneurysms were selectively occluded with coils. Of these aneurysms, 110 (13.2%) were very small (57 ruptured and 53 unruptured). We performed a retrospective analysis of these cases using the Glasgow outcome scale (GOS) for clinical followup and digital subtraction angiography (DSA) and/or MR angiography (MRA) for angiographic followup.
Results: Mean duration of followup was approximately one year. Overall clinical outcome of patients showed 78 patients (76.5%) with good recovery, six (5.9%) with moderate disability, nine (8.8%) with severe disability, five (4.9%) with vegetative state, and four (3.9%) that had died. All asymptomatic unruptured aneurysms showed good recovery. No delayed rebleeding was observed. There were no procedural related complications. We encountered major recanalization in four aneurysms (10%) of the followedup ruptured aneurysms, requiring retreatment with coils; there were no major recanalizations in cases of unruptured aneurysms. Six out of nine (67%) unruptured aneurysms showing initial body filling had changed into complete occlusion at later follow up.
Conclusions: Endovascular treatment may be a feasible and effective therapeutic alternative for very small aneurysms. Endovascular coil embolization of very small ruptured aneurysms was effective in controlling hemorrhage; however, this technique requires strict followup and may necessitate additional treatment. By contrast, outcome of very small unruptured aneurysms was excellent.

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Objective: Mechanical thrombectomy is a newly available endovascular treatment for acute stroke in Japan, as MERCI Retriever was approved in 2010. We evaluated initial experience of Merci Retriever mechanical thrombectomy in Japanese top centers.
Method: Fifteen of 19 centers, which experienced 4 cases or more of MERCI Retriever mechanical thrombectomy since approval of MERCI Retriever, contributed to this study. This series was equivalent to 42.0% of whole experience in Japan during the initial 8 months. Baseline, procedure and clinical results variables were retrospectively recorded. Outcome was categorized as Good (modified Rankin scale 0 to 2), Fair (3 to 4), and Poor (5 to 6), and analyzed by each variable and successful recanalization (TICI scale 2A or better 2B or better).
Result: One hundred and ten patients received Merci Retriever mechanical thrombectomy in this study. Mean age was 71.8 years, number of males was 67.2%, and median time from onset to admission was 95 minutes. Baseline median NIHSS was 19, and site of occluded artery was ICA 40.3%, MCA 49.5%, and VABA 9.2%. Mean number of the device used in one treatment was 1.3, and median number of attempts per one target vessel was 2. Treatment resulted in successful recanalization in 74.6% of TICI grade 2A and or better, 48.3% of TICI grade 2B and or better, with adjunctive endovascular technique in 56.7%. Overall, Good clinical outcomes obtained in 28.2%, Fair outcomes in 40.0%, and Poor outcomes in 31.8%. Mortality rate was 10.9%. Intracerebral hemorrhage occurred in 31.6%, while symptomatic hemorrhage occurred only in 2.6%. Clinically significant procedural complication did not occur. Hemorrhage and complications were less than previous reports. Factors significantly related to good outcome were successful recanalization, younger age, low NIHSS score at admission, and high ASPECTS-DWI score before treatment. These results are compatible with previous report of mechanical thrombectomy using MERCI Retriever.
Conclusion: A high rate of successful vessel recanalization and acceptable clinical results with low rate of complications were obtained in initial experience of Mechanical thrombectomy using Merci Retriever in Japan top centers. Contraindicated or failed patients with intravenous rtPA therapy recommended to treat with Merci Retriever mechanical thrombectomy.

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Objective: Carotid Wallstent is available in three diameter sizes. It is considered important to have knowledge regarding the state of the stent cells of different sizes of Carotid Wallstent. The aim of this study was to examine the state of stent cells of different sizes.
Methods: The 6mm, 8mm and 10mm diameter Carotid Wallstents were deployed in a 6mminner diameter tube. States of stent cells of Carotid Wallstents in tube were examined for shape, angle of one stent cell, area of one stent cell, and stent cell number per 1 cm².
Results: Cell shape was stretched longitudinally when placed in a tube of smaller diameter than the stent. Angle of stent cell of 6, 8, and 10 mm diameter Carotid Wallstent were mean 116.4, 82.8, and 67.2 degrees, respectively. Free cell area of 6, 8, and 10 mm diameter Carotid Wallstent were mean 2.7, 3.2, and 4.4mm², respectively. Stent cell number per 1 cm² of 6, 8, and 10 mm diameter Carotid Wallstent were mean 37.1, 31.1, and 22.7 cells, respectively.
Conclusions: It may be necessary to select a stent of diameter near the target vesseldiameter to expect a high stent mesh density by stent cells.

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Objective: We report on a case of the right anterior condylar confluent (ACC) dural arteriovenous fistula (AVF) with unique clinical course.
Case presentation: A 57yearold man presented with pulsatile tinnitus and right hypoglossal nerve palsy. Cerebral angiography revealed right ACC dural AVF. Transarterial embolization was performed at first to avoid permanent hypoglossal nerve palsy after the treatment. One year after regression of symptoms following the initial treatment, the patient developed the right ocular symptoms due to an alteration of venous outflow. He underwent transvenous embolization using an approach via the intercavernous sinus from the contralateral inferior petrosal sinus with complete obliteration of the dural AVF with clinical cure.
Conclusion: Dural AVF involving ACC may recur with clinical symptoms similar to cavernous sinus dural AVF. Selection of a strategy based on the clinical and angiographic condition is extremely important. Contralateral approach can be a useful alternative in certain situations for the treatment of ACC dural AVF.

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Objective: The authors report a case of migration of glue (NBCA : nbutyl2cyanoacrylate) during presurgical direct puncture embolization of carotid body tumor.
Case presentation: A 42yearold woman had a gradually enlarging mass at the left neck. She underwent presurgical embolization of the tumor under the diagnosis of carotid body tumor. After failed transarterial embolization due to numerous but tiny feeding arteries, direct percutaneous embolization of the tumor using 20% NBCA was performed under fluoroscopic loadmap guidance. No neurological complications were caused by the procedures, though retrograde migration of NBCA into the occipital artery and facial artery occurred during the procedure. Postembolization angiography showed complete devascularization of the tumor. The tumor was completely removed without massive bleeding during surgery the day after the embolization. Histological examination revealed the diagnosis of paraganglioma. Her postoperative course was uneventful.
Conclusion: Presurgical direct percutaneous embolization with NBCA would be an effective procedure to control bleeding during removal surgery for a carotid body tumor. However, a careful attention should be paid for migration of NBCA into surrounding normal arteries to avoid neurological complications.

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Objective: To report two cases of rapidly enlarged bloodblister like aneurysm (BBA) of internal carotid artery, which were successfully treated by aneurysmal coiling.
Case presentation: Case 1: A 44 year old woman suffering from subarachnoid hemorrhage (SAH) was referred to our hospital. 3DCT angiography revealed BBA, though surgical treatment could not be done immediately because of the administration of antiTNFα monoclonal antibody for rheumatoid arthritis. The aneurysm had been enlarged for a few days after the onset, therefore aneurysmal coiling was done. The clinical course was good with mRS 0 and rerupture or regrowth of the aneurysm not observed 2 years after the treatment. Case 2: A 39 year old man suffering from SAH was admitted. Digital subtraction angiography demonstrated BBA which had been enlarged for a few days after the onset. It was treated by aneurysmal coiling after the enlargement. The patient was discharged from the hospital without any neurological deficit. Recanalization of the aneurysmal neck had been seen after the treatment, however regrowth or dome filling was not observed on MR angiography performed 1 year after the onset.
Conclusion: Coil embolization can be one of the treatment options for saccularshaped BBA in the acute stage; however, strict observation is needed against recanalization and regrowth of the aneurysm.

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Objective: We herein report a rare case of primitive trigeminal artery variant (PTAv) aneurysm presenting with abducens nerve palsy.
Case presentation: A 61yearold female had suffered from diplopia of her left lateral gaze for seven days due to left abducens nerve palsy. Left carotid angiography showed a PTAv trunk aneurysm. Internal trapping of the aneurysm with detachable coils was performed. The left abducens nerve palsy thereafter showed a remarkable improvement and disappeared completely.
Conclusion: Only six previously reported cases of PTAv were associated with an aneurysm of the PTAv. Two of the six cases presented with abducens nerve palsy. We therefore consider coil embolization of PTAv aneurysms to be a useful treatment, even if the patient presents with abducens nerve palsy.

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Objective: To report new technique to stabilize a guiding catheter, which was introduced from brachial artery by use of a GooseNeck Snare from contralateral brachial artery.
Case presentation: A 76yearold man presented with unruptured left internal carotid artery aneurysm with a type III aortic arch. The guiding catheter was successfully navigated from the right brachial artery to the left common carotid artery using the GooseNeck Snare inserted from the left brachial artery. The aneurysm was successfully treated with coil embolization.
Conclusion: The use of GooseNeck Snare is considered to be effective for inducing and holding a guiding catheter. Gentle and synchronized manipulation by two operators was required to succeed with this technique.

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Objective: The authors report a case of cavernous sinus dural arteriovenous fistula (CS dAVF) treated by transvenous embolization (TVE) using microcatheter pullup technique.
Case presentation: A 76yearold woman with dAVF in the bilateral CS underwent transvenous embolization of the right CS. The right inferior petrosal sinus could not be reached using a 0.035inch guidewire via the right internal jugular vein (IJV) where a guiding catheter was located. Then, a guiding catheter was relocated in the left IJV. A guidewire reached the right inferior petrosal sinus (IPS) through the left IPS and the posterior intercavernous sinus. The guidewire could go proximally in the left IPS to the right IJV, though it could not pass distally into the right IPS. The guidewire in the right IJV was caught using a gooseneck snare through a coaxial microcatheter, which was introduced via another guiding catheter located in the right IJV. By pulling the guidewire, the gooseneck snare was pulled up with the microcatheter into the right IPS, then the microcatheter could reach the right CS. Embolization of the right CS with platinum coils through the microcatheter resulted in complete disappearance of the CS dAVF. The patient's symptoms improved 2 weeks after the procedure.
Conclusion: Microcatheter pullup technique might be effective to reach an affected CS during transvenous embolization of CS dAVF, when a microcatheter could not be introduced into the CS by an ordinary method.

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