We retrospectively analyzed complications of clipping surgery for paraclinoid aneurysms to establish the art of clipping with a maximum safety. Sixty patients with 63 paraclinoid aneurysms were retrospectively evaluated. The pterional approach was performed in all the patients, and the contralateral approach was applied to 12 aneurysms. Ninety-four clips were used for the 63 aneurysms. Straight or bayonet clips were used in 19 aneurysms; fenestrated clips, in 16; curved or angled clips, in 15; side-curved or side-angled clips, in 8; and L-shaped clips, in 5. The longitudinal clipping was performed for 44 aneurysms; and perpendicular clipping, in 19 aneurysms. The surgical complications included visual impairment in 4 patients (6.7%), temporary oculomotor paresis in 2, CSF leakage in 1, meningitis in 1, and epidural hematoma in 1. Straight or bayonet clips were used perpendicularly in all the 4 patients with visual deterioration. Longitudinal clipping with a non-straight clip is recommended to avoid damage to the optic nerve.

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Background: Blood blister-like aneurysms (BBAs) arising from the anterior wall of the internal carotid artery are characterized by a fragile wall, a poorly defined neck, and a high incidence of rebleeding during the acute period after subarachnoid hemorrhage (SAH). They remain as severe therapeutic challenges. The authors investigated the safety and mid-term efficacy of trapping of the aneurysm with high-flow bypass between the second portion of the middle cerebral and cervical external carotid arteries by using a radial artery graft (EC-RA-M2 bypass) for the complex lesions.
Methods: The medical charts of 14 consecutive patients with ruptured BBAs during the past 4 years were retrospectively reviewed. The patients' mean age was 60.0 years. The World Federation of Neurosurgical Societies grade was I or II in 7 patients and III-V in the other 7 patients. Nine patients underwent acute craniotomy within 24 hours after SAH.
Results: After operation, total elimination of the BBAs with good patency of the bypass was confirmed in all the patients. None of the patients had rebleeding from nor refilling of the aneurysms within a mean follow-up period of 26.5 months. Although one patient showed postoperative perforator area infarction and the other two patients had symptomatic vasospasm, good clinical outcome (Glasgow Outcome Scale: good recovery or mild disability) was observed in 12 patients (89%) at the last follow-up.
Conclusions: Acute surgery using aneurysmal trapping with EC-RA-M2 bypass is effective for the treatment of BBAs, with good and safe mid-term outcomes.

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Surgical treatment of anterior choroidal artery (AChA) aneurysms used to be associated with a high risk of ischemic stroke in the AChA territory. We retrospectively studied 70 consecutive patients with AChA aneurysms to evaluate their clinical characteristics and surgical outcome against the background of routine use of indocyanine green video angiography and motor-evoked potential (MEP). Between 2007 and 2016, 70 procedures were performed for 70 patients with AChA aneurysms. AChA aneurysms were the primary target in 45 patients and the secondary target in 25 patients. Nineteen patients were men and 51 were women, with a mean age of 60.1 years. The mean size of the aneurysm was 4.2 mm. Sixty-eight aneurysms were obliterated with clips. Combination of multiple clips was required in 18 aneurysms to secure the patency of the origin of AChA. Decreased MEP amplitude was observed in 8 of 68 procedures with MEP monitoring but fully recovered after readjustment of the clips. None of the 49 patients without subarachnoid hemorrhage (SAH) and 12 patients with SAH grades 1 and 2 according to the World Federation of Neurological Surgeons classification developed symptomatic ischemia of AChA. Postoperative diffusion-weighted imaging revealed high intensity in the AChA territory in one patient, but the lesion was asymptomatic. Provided that sufficient operative field is obtained to allow inspection of the aneurysm in multiple angles and careful angioplastic clipping technique is utilized under appropriate monitoring, surgical clipping of the AChA aneurysm is associated with low risk of ischemic complications.

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Distal middle cerebral artery (MCA) aneurysms are relatively rare, and only few reports deal with treatment strategies. The present study retrospectively investigated the characteristics of and surgical approaches to distal MCA aneurysms. The subjects were 10 patients with distal MCA aneurysms selected from among 452 patients with cerebral aneurysms treated with neck clipping between September 2006 and August 2016. Sixteen distal MCA aneurysms were identified, with 13 (81.3%) located on the M2 segment. All the patients showed multiple cerebral aneurysms, and the total number of cerebral aneurysms was 37, representing a mean of 3.7 aneurysms per patient. The multiplicity of the aneurysms appeared markedly higher than the previous study findings in patients with distal MCA aneurysms. Evaluation with preoperative neuroimaging therefore appears important from this perspective. Of the 3 patients with ruptured distal MCA aneurysm, all the aneurysms were embedded in surrounding parenchyma with cerebral hemorrhage. This finding suggests the necessity to expose aneurysms from the surrounding parenchyma to obtain a wide surgical field for neck clipping. As for surgical approaches, anatomically, the M3 segment begins at the circular sulcus after turning 180° from the M2 segment and courses over a narrow space between the frontoparietal and temporal opercula. We therefore recommend the following: aneurysms located on M2 or M2-M3 segments above the limen insulae are accessible by using a distal sylvian approach, whereas aneurysms located from the M3 segment within the narrow and complicated structure of the opercular space need to be approached from sulci beyond the aneurysms.

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Secondary normal-pressure hydrocephalus (sNPH) following subarachnoid hemorrhage (SAH) is known to be related with poor outcome. Neurosurgeons have tried several treatments and procedures for prevention of sNPH, but none of them was proven to be effective. We chronologically reviewed 20 articles that described the risk for the development of sNPH associated with microsurgical clipping and endovascular coil embolization as treatments for ruptured aneurysms. Among 17,042 patients with SAH caused by ruptured cerebral aneurysms registered in 20 articles, 2,527 patients (14.8%) were diagnosed as having sNPH. sNPH was diagnosed in 1,673 (15.2%) of 10, 986 patients treated with microsurgical clipping and in 854 (14.1%) of 6,056 patients treated with coil embolization. The odds ratio (95% confidential interval) for the development of sNPH among the patients treated with clipping was 1.09 (1.00-1.20) in comparison with that among the patients treated with coil embolization (probability value of a Fisher exact test, 0.048). Before 2012, compared with clipping, coil embolization was associated with a higher incidence for the development of sNPH. After 2012, however, clipping was associated with a higher incidence of sNPH than coil embolization. Recently, the techniques and devices used in coil embolization have remarkably progressed, and their indication has expanded. Therefore, the background of patients treated with coil embolization is similar to that of patients treated with microsurgical clipping. Large studies that directly compare between clipping and coil embolization are needed to elucidate their real effect on the risk of developing sNPH.

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The utility of motor evoked potentials (MEPs) for intraoperative neurophysiological monitoring for unclippable complex aneurysms has not been established.
The aim of this study was to evaluate and validate the usefulness of intraoperative MEP monitoring in the treatment of complex aneurysms with and without extracranial-intracranial (EC-IC) bypass.
From among a group of patients who underwent intraoperative MEP monitoring during surgery for aneurysm, between 2007 and 2014, we retrospectively enrolled 17 consecutive patients with complex aneurysms.
Aneurysms were located in the cavernous portion of the internal carotid artery (ICA) in 6, the intracranial portion of the ICA in 6, the anterior cerebral artery in 1, and the vertebral artery in 4 patients. They included 4 large, 7 thrombosed, and 6 dissecting aneurysms. All were treated with parent artery occlusion with or without EC-IC bypass, which included 7 high-flow bypass procedures with radial artery grafting, and 7 low-flow bypass procedures. Of the 17 patients, 6 showed transient or permanent MEP changes. Four of 6 patients showed MEP changes due to temporary occlusion of the recipient artery during bypass construction. However, these changes were reversed by substitution of the recipient artery, intentional hypertension, and shortening of occlusion time. Two patients demonstrated MEP changes when the parent artery was occluded. In one of those two patients, MEP completely disappeared after parent artery trapping, and this remained unchanged until the completion of the surgery without any modification in obliteration of the parent artery. This patient experienced permanent postoperative hemiparesis. The second patient showed significant changes in MEP during temporary ICA occlusion, which however improved after changing the site of occlusion to the common carotid artery (CCA).
In conclusion, intraoperative MEP monitoring has a useful role in the treatment of complex aneurysms—in the selection of the safest and most appropriate recipient artery for EC-IC bypass, and choosing the most appropriate point for occlusion of the parent artery.

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Treatment of unruptured aneurysms in elderly patients tends to be contraindicated based on the risks and benefits for a limited life expectancy. In such cases, endovascular treatment has been frequently adopted because of its minimal invasiveness. We compared the results of endovascular treatment between non-elderly and elderly patients aged >75 years, and discussed its safety and agerelated issues.
We treated 531 patients with unruptured aneurysms in the past 5 years, including 74 elderly patients. We retrospectively examined and compared patient and aneurysm profiles, treatment methods, and angiographic and clinical results among non-elderly and elderly patients. We focused on large cavernous carotid aneurysms treated with flow diverters, which were used predominantly in the elderly.
The proportion of women was significantly greater in the elderly group. Aneurysms with a symptomatic mass effect, those of large and giant size, and those located in the cavernous portion were significantly greater in the elderly group. Regarding treatment methods, adjunctive techniques using double catheters and flow diversion were more often performed in the elderly group, and the rate of using the balloon or stent assist technique was higher in the non-elderly group. However, no significant differences in angiographic and clinical results were found between the two groups. However, the total complication rate was lower in the elderly group, and the rate of procedure-related ischemic complications was 4% in both groups, respectively. Among the 20 large carotid cavernous aneurysms, no significant differences in the rate of clinical improvement and angiographic results were found.
The clinical results and safety profiles of endovascular treatment for unruptured aneurysms in the elderly patients were not inferior to those in the non-elderly patients. In addition, considering the tendency for elderly patients to develop large aneurysms, particularly symptomatic large carotid aneurysms in the cavernous portion, the endovascular approach, including the use of a flow diverter, will be useful as a less invasive treatment option.

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In a high flow bypass, used for therapeutic occlusion of the internal carotid artery affected by giant or large aneurysms, a radial artery graft provides better long-term patency, but shorter available length compared with a saphenous vein graft. Therefore, a radial artery graft requires a shorter graft route. The purpose of this study was to verify the shortest graft route for a high flow bypass using cadaver dissection. Five cadavers were tested bilaterally, i.e. 10 sides in total. According to the relationships among the mandible, posterior belly of digastric muscle, stylohyoid muscle, and zygomatic arch, we examined 10 types of graft routes. The shortest of the 10 routes was a sub-mandibular route running laterally to both the digastric and stylohyoid muscles, and through the zygomatic arch at the occipital side. The longest route was an over-mandibular route through the zygomatic arch at the frontal side. On average, the former route was 2.5 cm shorter than the latter. Considering graft length limitations, a sub-mandibular route, lateral to both the digastric and stylohyoid muscles, and through the occipital side zygomatic arch, appears to be the most suitable for high flow bypass using a radial artery graft.

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We report two cases of very small (≤3 mm) de novo internal carotid-posterior communicating aneurysms (IC-PC AN) that developed and ruptured within a short period at the mirror site of a previous aneurysm.
Case 1: A 75-year-old woman presented with subarachnoid hemorrhage (SAH) caused by rupture of a very small (2.5 mm) left de novo IC-PC AN at the mirror site of a right IC-PC AN clipped 4 years and 6 months ago. The de novo IC-PC AN evolved from dilatation of the infundibulum of the posterior communicating artery and ruptured within 10 months after her last MR angiography (MRA).
Case 2: A 75-year-old woman presented with SAH following rupture of a very small (2.5 mm) right de novo IC-PC AN at the mirror site of a left IC-PC AN embolized 14 years ago. The de novo IC-PC AN developed and ruptured within 7 months after her last MRA.
We emphasize the importance of routine and-long-term radiographic screening in patients with cerebral aneurysms to detect de novo aneurysms, especially at mirror sites of previously occurring aneurysms. Aggressive surgical intervention may be indicated for even very small-sized de novo aneurysms due to the high risk of SAH.

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The authors encountered an interesting phenomenon in an adult hemorrhagic patient with moyamoya disease. A peripheral aneurysm in the distal branch of the right lateral posterior choroidal artery was resolved by additional cerebral revascularization surgery. This case illustrated that cerebral revascularization surgery with large craniotomy was more effective than it was with small craniotomy for preventing rebleeding events.
A 38-year-old woman was admitted to our hospital with disturbed consciousness, left hemiparesis, and total aphasia. She had a history of hemorrhagic moyamoya disease and had undergone cerebral revascularization surgeries in both hemispheres to prevent rebleeding. These surgeries included superficial temporal artery/middle cerebral artery [STA-MCA] double bypass with large craniotomy in the left hemisphere 5 years previously and STA-MCA single bypass with small craniotomy 2 years previously on the opposite side.
Computed tomography (CT) demonstrated that right intracerebral hemorrhage and intraventricular hemorrhage had occurred as a rebleeding event. Seven months after the rebleeding event, angiography showed a new peripheral aneurysm of the distal branch of the right lateral posterior choroidal artery and development of abnormal collateral flow from the posterior cerebral artery (PCA). We performed an additional cerebral revascularization surgery (occipital artery [OA]-MCA bypass + encephalo-myosynangiosis in the occipital lobe and encephalo-duro-periosteal-synangiosis in the frontal lobe) in the right hemisphere. By three months after surgery, the peripheral aneurysm had disappeared.
This case suggests that cerebral revascularization surgery with STA-MCA single bypass and small craniotomy is insufficient to prevent rebleeding and that cerebral revascularization surgery with STA-MCA double bypass and a larger craniotomy is necessary to prevent rebleeding in adult hemorrhagic moyamoya patients.

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We report a case of dural arteriovenous fistula (DAVF) of the isolated superior sagittal sinus (SSS) that was successfully treated with transcranial transvenous embolization. The transcranial approach has only been reported in small case series, and its technical details have yet to be discussed.
A 53-year-old man who underwent five craniotomies for an occipitoparietal hemangiopericytoma presented with dizziness and mild cognitive dysfunction 2 months after the last craniotomy. The patient's MRI showed venous congestion of the deep medullary veins of the bilateral cerebral hemispheres. Cerebral angiography revealed a DAVF of the SSS with cortical reflux. As the posterior part of the SSS had been removed in the previous surgery, the transcranial approach was applied for embolization of the fistula. An oval craniectomy above the SSS was prepared anteriorly to the DAVF in the operating room. The SSS was punctured by an 18-gauge cannula under fluoroscopic guidance in the angiography room on the following day. Through the outer sheath of this cannula, the fistula was embolized with platinum coils. The venous congestion showed significant improvement on postoperative imaging, along with improvements in cognitive impairment and dizziness.
Thus, direct sinus puncture can be a useful option for transvenous embolization of DAVF when the typical transjugular approach is difficult.

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