The skills of skull-base drilling and cerebral revascularization are now essential in open surgery for cerebral aneurysms. For this purpose, achieving a bloodless operative field, and identifying and preserving the normal anatomical structures are imperative. We propose the effectiveness of creating a bloodless operative field and operating under a high magnetic field by presenting four common approaches for aneurysm surgery: the transsylvian approach; interhemispheric approach; extradural anterior clinoidectomy; and lateral suboccipital approach. Here we show how we achieve our preferred operative field and present our operative figures.
For safe, high-quality clipping of cerebral aneurysms, vascular surgeons should create a bloodless operative field, adjust to surgery under a high magnetic field and train hard for skull-base drilling by attending cadaver courses.

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Meticulous dissection to detach an aneurysm from perforating arteries and cranial nerves is often indispensable to achieve complete neck clipping. We report surgical techniques for dissection of an unruptured aneurysm using a pterional approach.
Aneurysmal retraction with a suction tube in an appropriate direction is considered to facilitate dissection of aneurysms. For this purpose, our surgical techniques are summarized as follows: 1) Our “hand-resting” operating style. 2) The use of short-size operating instruments securing meticulous dissection of an aneurysm. 3) Dissection in an appropriate direction derived from both a subfrontal and transsylvian operative field. 4) Mobilization of parent arteries, which is considered to secure aneurysmal retraction.
A wide operative view and steady aneurysmal retraction contribute to the safe dissection and clipping of unruptured aneurysms, preserving the parent arteries and its perforators.

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A bloodless operation field is one of the most important factors for the success of cerebral aneurysm surgery. Therefore, surgeons must know how to create a bloodless operation field. In this paper, we describe some surgical techniques and points to provide and maintain a bloodless operation field in cerebral aneurysm surgery.

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The role of endoscopic surgery for intraventricular hemorrhage remains controversial. We compared the surgical results and outcomes of intraventricular hematoma associated with hypertensive intracerebral hemorrhage between patients who underwent external ventricular drainage (n＝6) and those who received both endoscopic surgery and external ventricular drainage (n＝6). The period of external ventricular drainage was significantly shorter in the endoscopic surgery group (4.7 days vs. 10.5 days), leading to prevention of meningitis and cerebrospinal fluid leakage. However, there was no significant difference in the rate of patients who required cerebrospinal fluid shunt surgery and the hospitalization period between the two groups. The functional outcome at one and three months tended to be more favorable in the endoscopic surgery group, but the differences were not significant.
Endoscopic surgery may be an effective treatment for intraventricular hemorrhage, but a larger study is needed to prove it.

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The surgical procedure for a brainstem lesion must be carefully considered because of the critical neurological functions of the brainstem. We have surgically treated brainstem cavernous angioma after bleeding without significant postoperative morbidity, because the boundary between the angioma and normal brain tissue is generally well demarcated by preceding hemorrhages. However, because the angioma tissues are often destroyed by hemorrhage, care must be taken not to leave any pieces of the angioma tissue. To reduce the risk of morbidity, surgeons must investigate carefully when performing the operation.
We analyze the surgical results and pathological findings of nine cases of symptomatic brainstem cavernous angiomas, and discuss the various surgical strategies especially based on the timing of surgery.

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Patients with posterior circulation insufficiency often have a poor prognosis despite aggressive medical treatment. We performed nine superficial temporal artery to superior cerebellar artery (STA-SCA) anastomosis for such unstable patients between December 2008 and December 2012. Surgery was performed using the subtemporal approach. The floor of the middle fossa was shaved flat and the tentorium was incised to obtain sufficient working space. The vein of Labbé and other temporal bridging veins were detached from the brain to facilitate retraction of the temporal lobe. The patency of the anastomosis was confirmed using indocyanine-green (ICG) videoangiography and Doppler ultrasonography. Postoperatively, all the patients showed clinical and radiological improvement of vertebrobasilar insufficiency. Temporal contusion was not observed on the postoperative MRI’s in the present series. Transient trochlear nerve palsy was observed in five patients.
STA-SCA anastomosis is effective in selected patients with refractory vertebrobasilar insufficiency, and the procedure is safe when performed by expert neurosurgeons.

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Recently, endovascular technology such as mechanical thrombectomy has been used for carotid recanalization as a potentially effective treatment option in the acute phase. However, to date, angiographical results and clinical outcome remain unsatisfactory. We report our experience on ten patients treated with endovascular techniques for acute internal carotid artery occlusion. Three patients were given intravenous tissue plasminogen activator therapy before the intervention. The endovascular procedure was carried out under local anesthesia. PTA/stenting was performed in eight patients, suction thrombectomy in four and mechanical thrombectomy using Merci retriever in two. Recanalization was successful (TICI grade 2B–3) in four of the 10 patients (40%). In four of six patients (60%) with the occlusion caused by atherosclerotic stenosis, recanalization was achieved. Only two patients (20%) had a favorable outcome (modified Rankin Scale score 0–2) at discharge, and the mortality rate was 40%. There were three procedure-related complications, two distal embolisms and one hematoma at the puncture site. Patients with internal carotid artery occlusion caused by atherosclerosis benefitted more from the endovascular treatment than those whose occlusion was caused by cardiac embolism. Our case series suggest that in patients with an acute internal carotid artery occlusion, particularly caused by atherosclerotic stenosis, endovascular treatment may be associated with recanalization and neurological improvement.

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Balloon protection effectively prevents distal embolism during carotid artery stenting (CAS). However, some patients have occlusion intolerance to transient balloon-induced ischemia and can develop secondary perioperative ischemic complications. We conducted this study to identify factors that can predict ischemic intolerance. We analyzed 58 patients undergoing CAS in which double balloon protection was used. Seven patients (12.1%) had ischemic intolerance. These patients had a significantly lower stenosis rate (p＝0.0255), poor collateral flow (p=0.0001), and pooling appearance of the contrast medium in the ipsilateral internal carotid artery during test proximal balloon occlusion (P＝0.0086).
We conclude that preoperative assessment of collateral flow and intraoperative assessment of flow pattern during the proximal test occlusion are useful predictors of ischemic intolerance. These findings may be useful when choosing the protection devices during CAS or determining whether a shunt system should be used during carotid endarterectomy.

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It is difficult to completely prevent rupture or the need for retreatment after coil embolization for saccular aneurysms.
We retrospectively analyzed the correlation between rupture or retreatment and the volume embolization ratio (VER) after coil embolization, and used a receiver operating characteristic (ROC) curve analysis to determine the optimal cut-off value of the volume embolization ratio.
Of the 289 embolized aneurysms, rupture and retreatment occurred in 23 (8.0%) and in nine (3.1%) aneurysms, respectively, during a follow-up period of 22.7 months. Rupture or retreatment tended to occur more frequently in ruptured aneurysms with a low VER (＜25%). An ROC curve based on the VER in ruptured aneurysms showed an AUC (area under the ROC curve) of 0.68 (95% confidence interval＝0.58–0.79). A VER cut-off value of 25% yielded optimal sensitivity and specificity (78.9%, 54.7%).
There is a correlation between the rupture or retreatment and the VER after coil embolization in ruptured aneurysms. The optimal cut-off value of the VER for ruptured aneurysms is 25%.

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We retrospectively studied the mechanisms of development and enlargement of cyst following gamma knife surgery (GKS) for arteriovenous malformation (AVM) in 25 (15 males and 10 females) patients who developed cysts at 1.1–16 years after GKS. Cysts contained a nodular lesion enhanced with gadolinium-DTPA in 12 patients, and were associated with so-called expanding hematoma with severe surrounding brain edema in 10 patients. Magnetic resonance imaging with gadolinium-DTPA was not performed in three patients. Fourteen patients were treated with craniotomy, and two with placement of the Ommaya reservoir. One patient underwent both placement of the Ommaya reservoir and craniotomy. Spontaneous regression of the cyst was observed in one patient, and nine patients were treated conservatively. Two patients were lost to follow up. Histological examination showed proliferation of dilated vessels with fibrinoid degeneration associated with exudation of protein and bleeding. These findings were compatible with late radiation change. Increased vascular permeability at the vessel wall may be important in cyst formation and enlargement. Histological findings of nodular enhancement and expanding hematoma were essentially similar in terms of late radiation change.
Our study suggests the optimum treatment for cyst formation following GKS for AVM is cyst opening and removal of late radiation change lesion through craniotomy.

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A 49-year-old woman presented with a sudden onset of right hemiparesis and motor aphasia. Computed tomography (CT) and magnetic resonance imaging (MRI) showed subarachnoid hemorrhage (SAH) localized in the interhemispheric fissure and cerebral infarction in the territory of the left anterior cerebral artery (ACA). Digital subtraction angiography (DSA) demonstrated segmental narrowing and dilatation at the left A2 segment, leading to a diagnosis of ACA dissection.
The day after the onset, we planed trapping of the dissecting portion and A3–A3 side-to-side anastomosis. As a result, we performed only the wrapping of the dissection portion, because the dissection was longer than we expected. Neither aneurysmal dilatation nor narrowing progressed almost six months after the operation.
This case indicates wrapping is also effective as a treatment of dissecting aneurysms, and it is important to consider longer-than-expected ACA dissections.

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