Background: Bypass surgery is a fundamental and essential technique used by neurosurgeons. The indication for extracranial-intracranial (EC-IC) bypass surgery for cerebral ischemia is limited due to the high rate of perioperative stroke, and it is necessary to conduct safe and secure surgery to reduce perioperative complications. Herein, we report our technique of conducting bypass surgery in a safe and secure manner.
Methods: We performed EC-IC bypass surgeries for patients with symptomatic internal carotid artery or middle cerebral artery (MCA) steno-occlusive lesions. All surgeons trained with 10-0 nylon sutures and gauze or the artery of a chicken wing using a microscope before performing the operation. Antiplatelet treatment was continuously administered before and after the operation. The parietal and frontal branches of the superficial temporal artery (STA) were harvested under microscopic visualization and secure hemostasis was achieved. After a dry and acceptable operative field was obtained and established, STA-MCA bypass surgery was performed. During the anastomotic procedure, we focused on not taking a bite of the underside of the artery, and not injuring the intima of the arteries, by controlling the magnification of microscope appropriately.
Results: Twenty-six patients underwent EC-IC bypass surgery between 2014 and 2016 (mean age 66.3 years). Postoperative complications were delayed wound healing and chronic subdural hematoma. During the perioperative period, bypass patency was confirmed in all cases, and there was no cerebral infarction or hemorrhage.
Conclusions: EC-IC bypass surgery can be performed in a safe and secure manner by using a basic surgical strategy which recognizes pitfalls, and incorporating training which enables surgeons to conduct basic procedures with high precision.

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Objective: Radial artery graft (RAG) for complex vascular lesions has been a well-established treatment option. In the last 20 years, our center has performed more than 120 RAGs, during which we have come across various experiences including complications. In this report, we present the surgical technique, and intraoperative monitoring for 10 of our recent cases, based on our experiences of the complications. The results of diffusion-weighted image (DWI) ischemic findings within 2 days after surgery are also reported.
Materials & Methods: Recent RAGs performed for unruptured internal carotid aneurysm, and spontaneous carotid-cavernous fistula (CCF) are included in this study. The basic procedure was external carotid artery-radial artery-M2 (ECA-RA-M2) graft bypass combined with superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis. The highlights of this surgical technique are as follows.
1) Subcutaneous tunnel insertion using temporary clip to prevent kinking of the graft.
2) STA-MCA anastomosis is important for continuous cerebral perfusion pressure monitoring.
3) Selection of the recipient MCA for RA and STA anastomosis is confirmed by indocyanine green video angiography (ICGVAG), combined with temporary proximal MCA occlusion clip. The authors used monitoring bypass for select cases.
4) Antithrombotic agents are used before surgery for unruptured lesions as well, to prevent ischemic complications due to thrombosis and graft spasm. Additionally, DWI, 3DCTA perfusion CT, SPECT etc. are performed in the early postoperative period for the same reason.
Results: In this series with modified RAG technique, no symptomatic ischemic complications were experienced. Although the number of cases is small, the incidence of symptomatic ischemic complications with this surgical technique was lower than that reported in the past.
Conclusion: Since three surgical sites are involved, various parameters and possible complications need to be monitored during surgery, and in the postoperative period.

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Superficial temporal artery (STA)-to-middle cerebral artery (MCA) anastomosis is sometimes effective for moyamoya disease and chronic ischemic disease. Surgical indications are decided for internal carotid artery or middle cerebral artery occlusive disease with misery perfusion. The surgery must be performed safely to reduce the risk of complications. Forty patients underwent extracranial-intracranial bypass between July 2010 and July 2017 (30 men and 10 women; 28 patients had ischemic disease and 12 patients had moyamoya disease). We monitored the motor-evoked potential (MEP), micro-Doppler imaging, and indocyanine green (ICG) staining for STA-MCA bypass surgery. We determined the cortical MEP for all the cases. We used the MEP and micro-Doppler image for identifying a safe and effective recipient artery before anastomosis. During anastomosis, the MEP was monitored every minute. After anastomosis, we checked the micro-Doppler and ICG findings for the patency of the anastomosis. We think MEP is highly useful for performing STA-MCA bypass surgery safely and that micro-Doppler imaging and ICG staining are effective for evaluating postoperative bypass patency. We could perform STA-MCA bypass safely for using several modalities.

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Anterior clinoidectomy is an important skull base technique in the surgical treatment of aneurysms; however, certain complications are associated with this technique. Here, we developed a standardized extradural anterior clinoidectomy for improving surgical safety and retrospectively analyzed the procedural outcomes. The key steps of this technique include opening the superior orbital fissure, elevating the dura propria, using minimum drilling around the optic canal, maintaining hemostasis of the cavernous sinus, preserving the ophthalmic artery, and using the temporal fascia and abdominal fat during dura closure. Between 2014 and 2017, nine patients underwent extradural anterior clinoidectomy using these standardized procedures. Subsequently, no surgical complications were observed in any patient. Thus, we suggest that standardized extradural anterior clinoidectomy is useful for preventing surgical complications.

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Clipping of the internal carotid artery (ICA)-paraclinoid aneurysm is well known to be associated with a risk of visual impairment. However, whether visual function is influenced more by anterior clinoidectomy or by other procedures is still controversial. In this study, the impact of each procedure on visual function was evaluated by monitoring visual evoked potential (VEP). Between January 2008 and September 2016, 52 ICA-paraclinoid aneurysms were treated with clipping or trapping. All the surgeries for treating the aneurysms were performed from the ipsilateral side irrespective of their projection. After craniotomy, anterior clinoidectomy was performed extradurally only with a micro-rongeur to avoid heat injury. A clip was placed to avoid interrupting blood flow in the ophthalmic and superior hypophyseal arteries. VEP was monitored with light-emitting diode flashing silicone electrodes concomitant with electroretinography monitoring to confirm the stimulus to the retina. All aneurysms were clipped or trapped completely. Postoperative visual deterioration occurred in two cases (3.8%). VEP could be monitored in 42 cases (81%). During anterior clinoidectomy, change in VEP was observed in 11 cases but was transient in all the cases and did not affect the outcomes. Two of seven cases with permanent change in VEP after dural opening had a postoperative visual deficit. In conclusion, VEP monitoring is effective for predicting visual outcome if done reliably.

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Purpose: We review our case series of embolization for unruptured aneurysms <5 mm in maximum diameter to clarify the safety and availability of embolization for these aneurysms, for which surgery is not indicated in the present guidelines.
Materials and methods: The clinical materials were 499 unruptured aneurysms treated with embolization between 2010 and 2016, including 115 very small aneurysms <5 mm in diameter (VS group), 303 sub-small aneurysms 5-10 mm in diameter (SS group), and 81 large aneurysms 10-20 mm in diameter (L group). Profiles of the patients and aneurysms, treatment methods, angiographic and clinical results, and complications were investigated and compared among the 3 different size groups. Giant aneurysms >20 mm in diameter and aneurysms treated with trapping or a flow diverter were excluded because the treatment concept is completely different from that of typical saccular embolization.
Results: No significant difference in patient profile was found. The treatment methods were significantly different among the groups. More than half of the aneurysms in the VS group were treated with a simple method, but most of those in the SS and L groups were treated with various adjunctive techniques. Particularly, the stent-assisted technique was used for 61.7% of the aneurysms in the L group. The angiographic result of embolization was superior in the VS group. Complete occlusion was obtained in 37.4% of the aneurysms in the VS group, 21.1% of the aneurysms in the SS group, and 28.7% of the aneurysms in the L group (p≤0.001). The incidence rate of complications in the VS group was 5.2%, less than that in the other groups, though not significantly. The morbid-mortality rate in the VS group (1.7%) was also similar to or lower than that in the other groups.
Conclusion: Very small aneurysms have been considered untreatable according to a risk-benefit assessment. Some aneurysms have an associated high risk of procedure-related complications because of anatomical difficulty. However, aneurysms that are treatable with a simple method can be embolized more safely than larger aneurysms. Recent improvements in neuroendovascular devices and techniques have led to the expansion of surgical indication to small unruptured aneurysms. For some patients with aneurysms who are very anxious about future ruptures, treatment of their incidental aneurysms may be beneficial to provide them with security. However, the indication should always be decided ensuring safety foremost on the basis of patient consent after an impartial and experience-oriented explanation, considering the small annual rupture rate of very small, unruptured aneurysms.

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Although surgery for cerebrovascular disease is an important field for neurosurgeons, the number of operations is decreasing due to the developments of endovascular intervention (techniques). Recently, due to innovative training methods, novice neurosurgeons have been able to obtain necessary surgical skills by working on smaller numbers of cases. Here, we present our surgical education methods, which are designed to facilitate efficient, safe and reliable neurovascular surgery while utilizing a minimum number of actual clinical cases. Additionally, the author discloses the surgical results which occurred during his own training period.
Our educational methods consisted of hands-on training, students drawing surgical illustrations, and audiovisual simulations. Hands-on education is the first step to developing basic microsurgical skills. Creating operative illustrations before surgery is the most effective way for learners to confirm microsurgical anatomy, and is vital in allowing for simulation of individual cerebrovascular surgeries. Operative illustrations are created using digital techniques that can provide surgeons with three-dimensional images of surgical anatomy. Our audio-visual training is derived from records of several surgical maneuvers, and allows both trainers and trainees to manipulate microsurgical instruments in order to replicate the conditions of microsurgery. These audio-visual records are synchronized and edited on the same screen, so that trainees can watch sessions repeatedly, thereby learning to emulate neurosurgical techniques efficiently.
Using the educational methods described above, the author completed 28 clippings (11 cases of unruptured cerebral aneurysms; 17 cases of ruptured cerebral aneurysms), and 25 cerebral vascular anastomoses (23 cases of superficial temporal-middle cerebral artery [STA-MCA] anastomoses; 2 cases of occipital artery-to-posterior inferior cerebellar artery [OA-PICA] anastomoses). These results occurred during the neurosurgical training period in the third and fourth years of his surgical residency. All cases were resolved successfully. We emphasize the importance of neurosurgical education in environments where current neurosurgeons are practicing.

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We report our experience with a gelatin-human thrombin matrix (Floseal^®) as an intraoperative hemostatic agent, which provided effective hemostasis, in patients undergoing carotid endarterectomy (CEA). Angioplasty using a Hemashield patch graft was performed after intimal dissection in 15 consecutive patients undergoing CEA. Floseal was used at the suture site after resumption of vascular clamping and bleeding from the posterior surface of the carotid artery.
No postoperative hemorrhagic complications or lower cranial nerve dysfunction developed. Floseal provided sufficient hemostasis even with intraoperative heparin administration using an internal shunt. Floseal could also be used in bleeding from tissues surrounding the lower cranial nerves without causing nerve dysfunction. Our experience indicates that Floseal is effective and safe in CEA.

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Purpose: Intraoperative fluorescence angiography (IFA) using the fluorescent dyes fluorescein (FS) or indocyanine green (ICG) is a useful tool for cerebrovascular surgery. We compared these two fluorescent dyes for the detection of perforators and their application during bypass surgery.
Methods: Intraoperative fluorescence angiography was performed with intraoperative observatory modules using a OPMI PENTERO 900 microscope including two types of induction light for both FS and ICG to evaluate each dye within the same fluorescent operative field. Each dye (250 mg FS and 10× diluted ICG) were intravenously administered and quantitative analysis was performed within regions of interest using movie analysis software. The subjects for the evaluation of perforators were 17 cases of cerebral aneurysms treated in our department from December 2015 to May 2016.
Results: The detection of perforators was evaluated in 6 cases of ruptured and 11 cases of unruptured aneurysms. The locations of the aneurysms were as follows: 6 cases in the anterior communicating artery, 4 cases in the internal carotid artery/posterior communicating artery, and 7 cases in the middle cerebral artery. The fluorescence intensity of the perforators was evaluated using the hypothalamic artery, the lenticulostriate artery, and branches from the posterior communicating artery. The fluorescence intensity of the main trunks was evaluated using the A1, A2, M1, and M2 segments. The average fluorescence intensity of FS was 78.3±25.8 in the perforators and 117.4±22.2 in the main trunks. The average fluorescence intensity of ICG was 29.2±14.0 in the perforators and 76.2±40.0 in the main trunks. The ratio of average fluorescence intensity to maximum fluorescent intensity, which indicated the contrast of the vascular structure during fluorescence angiography, was 2.97 for FS and 1.98 for ICG. Fluorescence angiography was utilized in a case associated with postoperative hyper-perfusion after a superficial temporal artery/middle cerebral artery bypass, and the fluorescence intensity of the cortex was markedly higher using FS than for ICG after the bypass.
Conclusions: Fluorescein was superior to ICG for detecting perforators during clipping with respect to both fluorescence intensity and contrast. Fluorescence angiography with FS might be superior for predicting hyper-perfusion after bypass surgery.

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Among 307 cases of subarachnoid hemorrhage in our institution between February 2008 and September 2016, 21 cases of ruptured cerebral aneurysm accompanied by intraventricular hematoma with cast formation (packed IVH) were considered. Excluding cases of deep coma accompanied by bilateral dilated pupils at the time of admission, radical surgery was performed in 13 patients in the extremely early phase, that is, within 12 h of hospital admission. The World Federation of Neurological Surgeons grades upon admission were Grade 5 in 11 cases and Grade 4 in two cases. All nonoperative cases died within a short period. The 6-month outcome of the 13 treated cases was good prognosis in 4 patients at modified Rankin Scale (mRS) 0-2, mRS 3 in 1, mRS 4 in 1, mRS-5 in 4, and death in 3. Treatment for aneurysm was performed with priority on clipping. All patients aged below 60 years receiving treatment regained consciousness; however, all elderly patients had poor prognosis. In cases of “long hour” unconsciousness, where 1 h or more had passed before emergency admission, prognosis was extremely poor, regardless of receiving treatment or not. For patients with ruptured cerebral aneurysm accompanied by packed IVH, who frequently exhibit a high level of disturbance of consciousness, the concept of a therapeutic time window should be kept in mind. In some cases, complete recovery has been achieved as a result of rapid treatment of aneurysm and excision of hematoma.

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Some brain arteriovenous fistulas (AVFs) present with clinical signs that suggest their anatomical site. We describe successful treatment of 2 cases with unexpected fistula locations.
Case 1: A 69-year-old man presented with progressive chemosis in his right eye 6 months after suffering head trauma and cervical spine dislocation. From his clinical course, we expected to find a carotid-cavernous sinus fistula. However, the lesion was in the temporal muscle and drained into the superior ophthalmic vein.
Case 2: A 58-year-old man developed rapidly deteriorating paraparesis, associated with upper extremity motor weakness and brainstem symptoms. Although we strongly suspected a spinal dural AVF, the lesion was found between the tentorial artery and veins that fed through the brainstem vein into the spinal vein.
In both cases, the clinical symptoms were caused by unusual AVF drainage patterns. Venous or sinus thrombosis and collateral venous pathways apparently contributed to these unusual patterns. A complete brain vascular study is necessary to avoid missing such lesions.

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