Adequate operative field and preservation of perforating arteries is necessary for successful, safe clipping of cerebral aneurysm. However, it is often difficult to avoid multiple perforators adjacent or dorsal to the aneurysm even if they could be separated from the aneurysm. Here, we used a polyglactin mesh (Vicryl mesh®) for aneurysmal clipping surgery. The polyglactin mesh is made of glycolic-lactic acid polyester and can be hydrolyzed within a living body. It is very thin, about 0.1 mm, without being fuzzy, and can be cut freely into any size and shape. Because of its consistency, it can hold dissected perforators off the aneurysm while clipping the neck, thus facilitating safe and successful maneuvers. It can also be retrieved safely and easily because it does not adhere to the surrounding structures. We used them in 45 cases of aneurysm. We could clip the cerebral aneurysms safely while avoiding perforators, other critical arteries, and cranial nerves around the aneurysm. No complications like vasospasm and perforator injuries were noted. Eighty-seven percent of the clipping procedures were accomplished by junior neurosurgeons under the guidance of senior instructors using the polyglactin mesh. This procedure is useful and safe in preserving critical arteries and structures like perforators and cranial nerves around the cerebral aneurysm.

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Direct clipping of thrombosed or large cerebral aneurysm is sometimes difficult and has relatively high morbidity. Flow alteration with bypass could be a treatment option for such unclippable aneurysms. The author's cases are presented. Twenty-nine complex aneurysms were treated between January 2006 and December 2013. Ruptured/unruptured aneurysms were 7 cases/22 cases, respectively. Six aneurysms were symptomatic with mass sign. Treatment strategies were as follows: 1) Clipping or trapping using bypass or thrombectomy (17 cases), 2) Bypass with proximal occlusion (flow alteration) (10 cases), 3) Bypass with distal occlusion (flow alteration) (2 cases). Aneurysms treated finally with clipping or trapping could be cured with relatively low morbidity. Furthermore, thrombectomy after clipping or trapping led to the recovery of the symptoms. On the other hand, flow alteration techniques induced intra-aneurysmal thrombosis in all aneurysms, but 2 intracranial aneurysms ruptured after partial thrombosis. Therefore, intra-aneurysmal thrombosis after flow alteration techniques does not always result in the cure of aneurysms, and care should be taken for the possibility of recanalization after this treatment.

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Because the passage of a graft for a high flow bypass between an anastomosis site of the cervical external carotid artery to the temporal base is made in a blind manner, knowledge of anatomy is essential for a surgeon to perform the high-flow bypass. A radial artery graft provides better long-term patency but shorter available length in comparison to a saphenous vein graft. The radial artery graft, therefore, demands a shorter graft route. The purposes of this study were to confirm a relationship among a graft, surrounding muscles, vessels, and bones on a source image of a computed tomography angiogram (CTASI), and to investigate the shortest graft route. Fourteen patients undergoing high flow bypass for internal carotid artery aneurysms between 2008 and 2015, with a graft demonstrated on a CTASI, were evaluated. The following four types of graft routes including routes 1-3, which were submandibular routes, were classified on CTASIs. Route 1: A graft passes through the medial space to both the posterior belli of the digastric muscle and the stylohyoid muscle. Route 2: A graft goes up to the lateral space to the digastric muscle and turns to the medial space to the stylohyoid muscle. Route 3: A graft goes up to the lateral space to both the digastric muscle and the stylohyoid muscle. Route 4: A subcutaneous route lateral to the mandible. Measurement of the graft length on CTASIs revealed that the route 3 was the shortest among the four routes. The graft in route 3, however, was so close to the external carotid artery between the styloid process and the mandible on a CTASI that a passage tube for the graft could have disturbed the blood flow in the superficial temporal artery, which was used as an assist bypass. In consideration of the limitation of an available graft length, a submandibular route lateral to both the digastric and stylohyoid muscles was the most suitable for high flow bypass using a radial artery graft. Pre-operative observation of the graft routes on CTASIs seems to be useful to prepare for the procedure.

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Endothelin-A receptor inhibitor (clazosentan) treatment after aneurysmal subarachnoid hemorrhage has failed to show any beneficial effects on neurological outcome, despite resolution in angiographic vasospasm, challenging the central dogma that angiographic vasospasm is the main cause of delayed ischemic neurological deficit (DIND). Many putative mechanisms have been proposed, such as microvascular disturbance, spreading cortical ischemia, early brain injury, and inflammation, to explain the cause of DIND. Consequently, recent research findings pertaining to treatment of cerebral vasospasm and DIND have been confusing and contradictory. In this review, we summarize the latest research concerning this issue and discuss the future trends in treatment strategy.

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Microvascular anastomosis is a very important technique for cerebrovascular surgeons, and although it is not frequently used, technical failure is unacceptable because of the high risk of morbidity. Therefore, training using simulation models is essential. However, the required training volume has not been fully clarified in previous reports. Hence, determining the minimum training volume required before performing actual bypass surgery may contribute to more efficient training of young neurosurgeons, enabling them to attain technical expertise in a shorter period.
The author instructed young residents (postgraduate years 2-3) in microvascular anastomosis with the silicone tube training model. The time required to complete one stitch was measured, and these data were used to generate and study the residents' learning curves.
All of our residents achieved a dramatic improvement in dexterity after the initial thirty trials, and the time required to complete one stitch progressively decreased thereafter.
Based on the author's training record and the actual time required for suturing a STA-MCA bypass, the goal to be attained on the silicone tube model was calculated to be 1.10 minutes for one stitch. It was presumed that all trainees would attain this goal after 200 to 300 trials.
Thus, it is possible for a young neurosurgeon with limited training to acquire the technical skills for microvascular anastomosis within 3 to 6 months with appropriate instruction and continuous training.

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The posterior cerebral artery (PCA) is an important source of collateral blood supply to the anterior circulation in moyamoya disease. It has been reported that some patients with moyamoya disease require additional surgery after revascularization surgery of the anterior circulation due to delayed progression of PCA stenosis or occlusion.
This study included 68 pediatric patients with moyamoya disease who underwent revascularization surgery of the anterior circulation in our institute and followed up for a minimum of three years. At onset, the PCA was involved in 17 patients, and the PCA was intact in 51 patients. Of the 51 patients with an intact PCA, 10 (19.6%) presented with delayed progression of PCA stenosis or occlusion, and seven (13.7%) required additional revascularization surgery for the PCA territory. The average interval between initial surgery and additional surgery was 6.1 years. Five patients were symptomatic, and two patients were asymptomatic. All symptomatic patients exhibited transient ischemic attacks (visual disturbance in 5 patients and sensory disturbance in one patient). In asymptomatic patients, MRA showed progression of PCA stenosis, and single-photon emission computed tomography (SPECT) revealed markedly decreased uptake in the PCA territory.
Encephalogaleosynangiosis (EGS) was performed in all patients. All symptomatic patients showed clinical improvement. In both the asymptomatic patients, postoperative SPECT demonstrated an increase of uptake in the PCA territory.
EGS for the PCA territory is effective for improving clinical symptoms and radiological findings in pediatric patients with moyamoya disease who showed delayed progression of PCA stenosis. Even in asymptomatic patients, surgery should be considered, because it is difficult for young pediatric patients to describe transient visual impairment.

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We present our cases of cerebrovascular disease surgically treated in a hybrid operating room (Hybrid OR) in Okayama University Hospital. A total of 14 patients (cerebral aneurysm, 7; cerebral/spinal AVM, 7) were treated in combination with various kinds of support equipment such as intraoperative angiography, indocyanine green videoangiography, motor-evoked potential, and a navigation system in the Hybrid OR. All support equipment worked well, and all surgical procedures were performed safely. Surgical treatment using multi-modality support equipment in a Hybrid OR is a feasible option to reliably overcome cerebrovascular disease.

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We analyzed the incidence and mechanism of ischemic complications after internal trapping of ruptured vertebral artery dissecting aneurysms (VADANs). Between April 2009 and January 2014, we identified seven patients who were diagnosed with ruptured VADANs and who underwent internal coil trapping. All cases were treated in the acute stage and were evaluated with magnetic resonance imaging (MRI), including diffusion-weighted imaging (DWI), during the perioperative period. The incidence of ischemic complications was 71.4% (five cases), whereas the incidence of ischemia influencing the outcomes was 28.6% (two cases). Postoperative medullary infarctions were identified in two cases; one case was found before the surgery (possibly developed at the onset of dissection), while the other case was found postoperatively and was due to intentional obstruction of the perforator involved in the dissecting aneurysm. We conclude that careful internal coil trapping for VADANs can reduce, but not eliminate, the incidence of ischemia.

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Recently, endovascular therapy (EVT) for acute ischemic stroke has been developed to enhance early recanalization in patients who do not respond to intravenous recombinant tissue plasminogen activator (rt-PA). However, the efficacy of EVT remains uncertain. We compared clinical outcomes in patients treated with intravenous rt-PA alone (t-PA group; n=32) and those with EVT with/ without intravenous rt-PA (IVR group; n=42). The primary good outcome, defined as a modified Rankin Scale ≤2 at discharge, showed no statistical difference between the two groups (42.8% and 31.2%, chi-square: p = 0.31). In patients with internal carotid artery occlusion, the IVR group clearly showed better clinical outcomes than the t-PA group (Mann-Whitney U test: p = 0.019). Our clinical study indicates that in patients with internal carotid artery occlusion, EVT may be more effective as rescue therapy than intravenous rt-PA alone. Moreover, new generation devices, such as stent retrievers, are expected to have improved efficacy.

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We report a case of repeated cerebral infarction caused by internal carotid artery (ICA) dissection triggered by an elongated styloid process, a form of Eagle syndrome. A 41-year-old man presented with sudden, mild left hemidysesthesia. Magnetic resonance imaging (MRI) revealed a small acute cerebral infarction in the right parietal cortex and insular cortex. Magnetic resonance angiography and digital subtraction angiography (DSA) revealed a right-sided ICA dissection distal to the carotid bifurcation. Idiopathic carotid artery dissection was suspected, and the patient was prescribed aspirin and observed. However, 5 months after the initial cerebral infarction, he had a second episode of left hemiparesis and confusion accompanied by occlusion of the right ICA. Because the area of impaired perfusion in the right hemisphere was greater than that suggested by the diffusion-weighted images of head MRI and clinical status was worse than expected, we performed acute revascularization with aspiration of the thrombus and stenting to treat the carotid dissection. Recanalization with thrombolysis of cerebral infarction (TICI)-grade IIB was achieved. Computed tomographic (CT) angiography combined with analysis of bony structures revealed close proximity of the right ICA and an elongated styloid process with its tip directed toward the dissection. In an angiographic suite, a dynamic cone beam CT was performed with the head of the patient variedly rotated and tilted; the carotid artery dissection appeared to be triggered by the elongated styloid process. Resection of this process was performed to prevent recurrence of the cerebral infarction. Under the guidance of a navigation system, the elongated styloid process, which was located ventral to the anterior belly of the digastric muscle, was cut 3 cm from the tip. The patient was discharged on postoperative day 8 without medical problems, and no recurrence was observed for 12 months after the surgery.

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Dural arteriovenous fistulas (DAVFs) are generally present in the transverse-sigmoid sinus as well as the cavernous sinus. To date, endovascular surgery has been mainstream; however, direct surgical treatment seems to be primarily limited to anterior skull base DAVFs. We herein report two cases of non-sinus-type DAVF located in the middle cranial fossa that were successfully treated with direct surgery. Both were symptomatic and angiographically classified as Cognard type IV. The first case was referred to our institution because of recurrence of a left middle fossa DAVF seven years after initial treatment with transarterial coil embolization (TAE). Drainer obliteration was performed using the subtemporal approach. The second case had severe headache with prominent clinical features similar to those of a carotid cavernous sinus fistula. TAE was applied to the branches of the right external carotid artery to reduce the flow rate. Drainer obliteration was performed without difficulty using the conventional frontotemporal approach.
The cortical vein-draining DAVF, classified as Cognard type III or type IV, presents a high risk of intracranial hemorrhage. When diagnosed, they should be treated completely, as early as possible. The aforementioned drainer obliteration appeared to be the best way to cure the DAVF. Endovascular surgery before direct surgical treatment was effective to reduce shunt flow and to enable an easy access to the shunt point.

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