Moyamoya disease (MMD) is a unique cerebrovascular disease with unknown etiology. It is characterized by progressive stenosis of the terminal portion of the internal carotid artery and abnormal vascular network formation at the base of the brain. Surgical revascularization not only prevents ischemic attack by improving cerebral blood flow, but also reduces the risk of re-bleeding in patients with intracerebral hemorrhage at the posterior circulation territory. Regarding surgical procedure, recent studies have indicated the effectiveness of direct/indirect combined revascularization surgery, such as superficial temporal artery-middle cerebral artery anastomosis with pial synangiosis. Despite its long-term favorable outcome, local cerebral hyperperfusion syndrome and cerebral infarction caused by watershed shift phenomenon are potential complications of this procedure. Therefore, routine hemodynamic study and intensive perioperative management, including strict blood pressure control and administration of neuroprotective agents, are essential for a favorable outcome.

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Superficial temporal artery-middle cerebral artery (STA-MCA) bypass is a fundamental neurosurgery and a highly versatile technique. Off-the-job training has already been widely permeated, and even young surgeons can learn this surgical skill through training.
However, there are various difficulties in STA-MCA bypass surgery. To perform a successful surgery without complications, it is important for the surgeon to update their surgical skills and techniques, receive surgical instructions as an assistant, and to have various experiences that will allow him to be able to handle surgical complications later.
In this article, we describe important points from a more detailed viewpoint using photos and schemas on how to avoid complications beforehand and perform successful STA-MCA bypass surgery.
In STA-MCA bypass surgery, to avoid complications, it is important to take care of the following: (1) ensuring an optimal operating field, (2) gentle handling of blood vessels, (3) proper suturing.
To ensure an optimal operating field, an environment for proper suturing in a bloodless and semi-wet condition is essential. For gentle handling of blood vessels, attention should be paid to manipulation of the recipient/donor artery, processing method of small arterial branches, and handling method of the suturing needle. For proper suturing, attention should be paid to prevent suturing the opposite side, for suturing to adhere each inner membrane, and proper thread knotting, such as the Square knot.

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During high flow bypass (HFB) surgery to make a submandibular route using a radial artery, the passage of a graft between an anastomosis site of the cervical external carotid artery to the temporal base is made blindly. This is also a frequent occlusion site of the graft in the surgery. In this study, we focused on complications that can occur during this procedure. Fourteen consecutive patients undergoing HFB for internal carotid artery aneurysms between 2012 and 2017 were evaluated. In all 14 patients, patency of HFB was confirmed with postoperative computed tomography angiograms. Major complications concerning the surgery to make the submandibular route were the following: 1) the use of a medial route to the stylohyoid muscle (SHM) resulted in no extra margin of the radial artery length in 5 patients; 2) a long styloid process obstructed the submandibular route in 2 patients; 3) the superior temporal artery, which was compressed by a route tube at the external carotid artery, was obstructed during the assist bypass procedure in 2 patients; 4) a radial arterial graft was occluded in the submandibular region during the procedure in one patient. Considering the limitation of the available graft length, a submandibular route lateral to the SHM was the most suitable for HFB using a radial artery graft. To obtain good patency of HFB using this route, preparation for possible complications occurring during surgery is essential in addition to sufficient knowledge on the anatomy of this region.

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Gamma Knife radiosurgery (GKRS) for arteriovenous malformation (AVM) is a well-established procedure, and there have been few reports of recurrence or new nidus formation after complete obliteration. To date, we have had to treat three pediatric patients again because of recurrence of radiosurgically treated nidus or formation of a new nidus at a different site. Here, we reviewed these cases and report their pathological features.
The three of our AVM patients are 8, 11, and 13 years-old respectively. Each patients' AVM are found due to either intracerebral or intraventricular hemorrhage. For their first GKRS, 20-25 Gy was delivered to the margin of a nidus 0.08-2.33 ml in volume.
The post GKRS course was uneventful in all cases. In cases 1 and 2, complete obliteration was observed several years after GKRS. However, approximately 1 year later from the complete obliteration, the patients had bleeding because of nidus formation at the same or an adjacent site, and this necessitated a second GKRS. Subsequently, the patients have been followed-up closely, and complete obliteration has been achieved. In case 3, angiography performed approximately 3 years after the first GKRS revealed a residual subtle shunt but verified the disappearance of the nidus. However, angiography also revealed the formation of a new nidus adjacent to the site of the previous one. The patient underwent a second GKRS and complete obliteration was achieved 3 years later.
Obliteration progresses gradually after GKRS for AVM. Our cases suggest that along with obliteration, gradual hemodynamic or other changes also occur simultaneously in the surrounding area, which may result in recurrence or new nidus formation at the same or a different site. Therefore, even after complete obliteration is observed, magnetic resonance imaging should be performed for careful follow-up of patients. Any changes observed should necessarily be evaluated by angiography to exclude the possibility of a new nidus formation.

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High-grade cerebral arteriovenous malformations (AVMs) are too complex to be treated only with surgery; hence, combined therapy is an alternative that has emerged recently. Our standard treatment for AVMs that are difficult to treat with surgery was CyberKnife hypo-fractionated stereotactic radiosurgery alone. However, this procedure also has delayed adverse effects, such as subtotal occlusion, cystic changes, hemangiomatous lesions, and radiation-induced tumors. We report a case with an AVM requiring surgical removal at the irradiated site 5 years after undergoing CyberKnife treatment. A 47-year-old female developed an epileptic episode 20 years ago and was diagnosed with AVM following various evaluations. At the age of 42, she underwent CyberKnife stereotactic radiation therapy in another hospital. She came to us complaining of headaches and vision disorders 5 years later. Diagnostic imaging showed tumorous lesions in the area where the AVM existed. Edema was also noted in the surrounding areas. Conservative treatment showed no improvement. Therefore, surgical resection was performed and symptoms improved soon after. Considering her history and symptoms, we made a diagnosis of radiation-induced cavernoma. From this case, we learned that stereotactic radiation shows potential as a preoperative treatment for AVMs and is useful for multi-stage extirpation, which is one of the options in combined therapy.

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The aim of the present study was to clarify the current practices related to the use of carotid artery stenting (CAS) in comparison with carotid endarterectomy (CEA) for cervical internal carotid artery stenosis (CICAS) in neurosurgical facilities without full-time neuroendovascular specialists. A total of 82 patients (68 men and 14 women; mean age of 72.4 years) with CICAS treated surgically at Kanmon Medical Center during a 13-year period from April 2002 to March 2015 were identified, and their medical records were reviewed. Seventy-six CEAs (47 for symptomatic lesions and 29 for asymptomatic lesions) and 16 CASs (9 for symptomatic lesions and 7 for asymptomatic lesions) were performed in 68 and 15 patients, respectively. CAS has been performed since 2009, and 30 CEAs (21 for symptomatic lesions and 9 for asymptomatic lesions) were performed during the same period. Both sets of clinical data were compared and analyzed. No apparent difference in the characteristics of the stenotic lesion were observed. The main reasons for performing CAS were a high location of the stenotic lesion and serious previous disease. Cerebral ischemia occurred as a complication in 4 patients who had undergone CAS, but had no adverse influence on outcome; however it adversely influenced the outcome in 1 of 4 patients who had undergone CEA. Although currently few patients undergo CAS for CICAS, these results support its validity and safety in neurosurgical facilities that lack full-time neuroendovascular specialists. Accordingly the proportion of CAS procedures performed relative to CEA will likely increase in the future, also in such neurosurgical facilities.

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We report 2 cases with subarachnoid hemorrhage (SAH) secondary to ruptured blood-blister aneurysms (BBAs) originating from the anterior wall of the internal carotid artery (ICA).
Case 1: A 56-year-old man was transferred to our hospital with disturbed consciousness following a severe headache. Computed tomography (CT) showed diffuse subarachnoid hemorrhage, and cerebral angiography demonstrated a BBA originating from the anterior wall of the left ICA. We performed left ICA trapping with a high-flow bypass. His postoperative course was uneventful, and he was discharged without any neurological deficits.
Case 2: A 49-year-old man was transferred to our hospital with disturbed consciousness. Although CT showed diffuse SAH, using cerebral angiography, we could not identify any aneurysms. CT repeated 16 days after admission revealed a BBA originating from his right ICA. We decided to perform direct neck clipping because we could identify the neck of the aneurysm. Direct neck clipping of the aneurysm was performed without any complications. The patient was discharged without neurological deficits. Although the treatment of BBAs is usually difficult, an individualized strategy should be considered in patients presenting with BBAs.

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Non-traumatic aneurysms of the middle meningeal artery (MMA) are extremely rare. We report a rare case of a MMA aneurysm (MMA AN) associated with Paget's disease of the skull, which was effectively treated with transarterial embolization. A 73-year-old woman was referred to the Department of Internal Medicine at our hospital with an elevated serum alkaline phosphatase level. Bone scintigrams using technetium-99m-hydroxy methylene diphosphonate (^99mTc-HMDP) showed abnormal radioisotope uptake in the skull bones, and skull X-rays demonstrated a cotton wool appearance. Based on these findings, she was diagnosed with Paget's disease. Skull radiographs also showed intracranial platinum coils conforming to her history of coil embolization performed for the treatment of MMA AN. Magnetic resonance angiography revealed recurrence of a left MMA AN, and she underwent transarterial embolization using coils and n-butylcyanoacrylate. Because of an abundant blood supply to the skull, hemostatic complications might occur in patients with Paget's disease undergoing surgery. Therefore, endovascular embolization is a safe and effective treatment in such patients.

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Objective: Flat detector computed tomography perfusion (FD-CTP) imaging is a new modality that enables quick assessment of the cerebral perfusion in the angiography suite. We present three cases in which FD-CTP served to improve the precision of the therapeutic strategy during endovascular treatment.
Case presentation: The first case was a 40-year-old woman with a ruptured blood blister-like aneurysm in the right internal carotid artery (ICA). After the evaluation for tolerance to ICA occlusion using FD-CTP, she was treated successfully with endovascular internal trapping of the ICA.
The second case was an 89-year-man with a cerebral infarct in the left cerebrum due to severe stenosis of the left middle cerebral artery. After the angioplasty, we could confirm the therapeutic effect by using FD-CTP, which demonstrated the disappearance of hypoperfusion in the left cerebral hemisphere. The third case was an 88-year-old man with severe stenosis of the left cervical carotid artery. After dilatation of the stenotic lesion by using a small-diameter balloon, a FD-CTP image showed hyperemia in the left cerebral hemisphere, so we decided not to undergo further carotid artery stenting.
Conclusion: FD-CTP was useful for determining the therapeutic strategy during endovascular treatment.

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A 69-year old woman presented with a history of surgical clipping of an unruptured right middle cerebral artery (MCA) aneurysm 13 years before. Angiography revealed no residual aneurysm just after the operation. She presented to our hospital for the first time in 13 years. Computed tomographic angiography revealed a recurrent aneurysm from which M2 branches were distributed. We planned direct surgical clipping with preparation for surgical revascularization. The ipsilateral superficial temporal artery (STA) was sacrificed at the time of the first operation; therefore, we used the contralateral STA graft for a temporary bypass. Blood flow to this vessel was supplied by the radial artery via an arterial line. Intraoperatively, we monitored motor evoked potential (MEP) amplitude. The MEP amplitude was lowered to 23% of the control level 25 minutes after applying a temporary clip to M1 and M2 segments. We clipped the aneurysm and confirmed complete clipping by obtaining an indocyanine green (ICG) angiogram. The MEP amplitude recovered within 30 min after removing the temporary clips.
After operation, she experienced a transient right hemiparesis, which resolved within 12 hours. We propose that this method could be an alternative treatment strategy if, for whatever reason, the ipsilateral STA is not available for bypass surgery.

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Although computed tomographic angiography (CTA) is often the only modality for imaging before surgical treatment of intracranial aneurysms, it has some limitations and pitfalls. We report a case of diffuse subarachnoid hemorrhage (SAH) in which CTA revealed a small enhanced saccular abnormality on the surface of the caudal loop of the left posterior inferior cerebellar artery (PICA) that was highly suggestive of ruptured aneurysm. Surgical exploration failed to identify any PICA aneurysm but revealed an abnormal small structure with blood clot and a fibrous wall close by the PICA. The structure was connected to an irregularly shaped arteriole and easily bled, and was thus clipped with two hemoclips to prevent bleeding. Postoperative CTA scan demonstrated the hemoclips in precisely the same position as the enhanced abnormality on the preoperative image. We made a diagnosis of SAH caused by a distal PICA dissecting lesion with a false-positive saccular aneurysm on CTA and presumed that the contrast extravasation mimicked a distal PICA aneurysm. Physicians should be aware that the finding of a small aneurysm on CTA indicates a risk of a false-positive result, especially in patients being investigated for a ruptured aneurysm. Confirmatory imaging by repeated CTA or digital subtraction angiography is recommended in such cases.

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