Objective: Symptomatic vasospasm (VS) following subarachnoid hemorrhage is well known. Delayed symptomatic VS after clipping of unruptured aneurysms (uANs) rarely occurs, but its mechanism remains unclarified.

Based on our experience with two cases of symptomatic VS after clipping of uANs, magnetic resonance angiography (MRA) around postoperative day seven was performed for the investigation of VS after uAN-clipping operations.

Patients and methods: From January 2014 to December 2017, 34 consecutive patients with uANs underwent clipping at our institution. We performed MRA for the detection of VS following clipping of uANs around one week after the operation. Clinical characteristics were compared between the VS and non-VS groups.

Results: MRA-based VS was detected in seven (20.6%) of the 34 patients who underwent clipping of uANs, but these seven patients were asymptomatic. Although the clinical characteristics of these patients were evaluated to identify the risk factors for VS after the clipping of the uANs, there were no statistically significant differences in the analysis of the factors for the occurrence of VS.

Conclusion: Asymptomatic VS after clipping of uANs occurs relatively frequently, and early detection and prompt treatment are important to prevent delayed ischemic deficits.

For treating middle cerebral artery (MCA) aneurysms, clipping is given more priority than coiling due to easier accessibility during craniotomy. We reviewed patients with unruptured MCA aneurysms treated with coil embolization in our hospital and investigated its safety and usefulness.

In total, 1, 386 patients with unruptured aneurysms were treated for 12 years. 86 patients (6.2%) with MCA aneurysms were included in this study. We focused on 53 patients (34 females; mean age, 66 years) who were treated after 2010, when various adjunctive techniques were established. Clinical results and complications were examined and compared with those patients in the early period before 2010.

All aneurysms with a maximum diameter of 3-10 mm (mean, 5.3 mm) were successfully treated with coil packing with the following: single microcatheter (22 patients), balloon-assisted technique (3 patients), stent-assisted technique (9 patients), and double catheter technique (19 patients). Angiographic results showed complete occlusion (24 patients, 45.3%), neck remnant (24 patients, 45.3%), and body filling (5 patients, 9.4%). We encountered two procedure-related complications due to branch occlusion, and one affected patient showed symptoms. Morbidity and mortality rates were 1.9% and 0%, respectively. Endovascular treatment was selected due to the following: patient preference (28 patients), poor general condition (8 patients), single-session treatment for multiple aneurysms (17 patients), and retreatment of a clipped aneurysm (1 patient). Compared with the results obtained during the early period, the rates of complete occlusion and favorable outcomes were higher in the latter period.

Generally, most unruptured MCA aneurysms have an extremely broad neck and direct branching pattern from the dome. This makes clipping difficult even for highly skilled surgeons. Additionally, unique situations require less invasive treatment, such as poor general condition, multiple aneurysms requiring multiple craniotomy sessions, and strong patient preference. Since results of endovascular treatment have improved owing to new adjunctive methods, its demand may increase.

Cerebellar arteriovenous malformations (AVMs) are one of the most difficult AVMs to treat due to difficulty of access and the small surgical field involved. We reviewed 24 patients with cerebellar AVMs who underwent embolization from 2001 to 2018. We investigated its safety and effects, particularly before extirpation and stereotactic radiosurgery.

Endovascular treatment was performed in 24 patients (mean age, 42.4 years; range, 7-68 years) across 30 sessions. Clinical presentation included the following: hemorrhage (16 patients), headache (4 patients), cerebellar dysfunction (2 patients), and other non-specific symptoms (2 patients). Endovascular pretreatment strategies were as follows: preoperative (3 patients), preradiosurgery (17 patients), and curative (4 patients). The median Spetzler-Martin grade was III. The mean number of embolized arteries and treatment sessions were 3.8 (range, 1-10) and 1.3 (range, 1-4), respectively. AVM volume was ＜10 mL in 8 patients, 10-24 mL in 12 patients, and ≥25 mL in 3 patients. The nidus was located in the right cerebellar hemisphere (13 patients), left hemisphere (6 patients), and the median part including the vermis and the fourth ventricle (5 patients). Aneurysms were associated in 6 patients, including proximal feeder aneurysms (4 patients), flow-related aneurysms (3 patients), and intranidal aneurysms (2 patients). N-butyl cyanoacrylate (NBCA) was used in all patients, and coils were added to 5 patients with AVMs.

Angiographic results revealed ＞40% devascularization in all patients and complete occlusion of the nidus in 4 patients. All associated aneurysms were successfully occluded. Surgical extirpation was successfully performed in 3 patients. Subsequent stereotactic radiosurgery resulted to disappearance of AVMs in 75% of patients after ＞3 years of follow-up (6/8). We encountered 3 procedure-related complications, including hearing disturbance (2 patients) and temporary oculomotor palsy (1 patient). In our study, embolization of cerebellar AVMs was safe and effective which can improve future treatments. From a technical perspective, ischemic complications of the internal auditory artery should be considered in the embolization of anterior inferior cerebellar artery feeders of AVMs at the cerebellopontine angle. Endovascular treatment of associated aneurysms is necessary to reduce perioperative rupture risk during and after secondary treatment. Embolization may be a useful option in multimodal treatments for cerebellar AVMs.

Aneurysmal localization is important for effective treatment. We used Aquarius NET® (TeraRecon, Inc, Durham, USA) to review cases of middle cerebral artery aneurysms treated between June 2015 and September 2018 and simulated surgical clipping on them. The XY plane represented the surgical field with a transsylvian approach, while the Z axis corresponded to the visual axis. The distribution map of all 36 aneurysms was plotted onto the XY plane, in the vicinity of the lateral side of the sphenoid ridge, which was the origin. The use of Aquarius NET® to plot the coordinates of aneurysms can be practical and useful in the simulation of surgical clipping.

Paraclinoid aneurysms generally have benign natural history. The risk of rupture, however, may vary due to the anatomical environment of the individual aneurysm. When dural and bony structure surround the aneurysm, the risk is small; alternately, when it is mostly exposed in the cerebrospinal fluid space, the risk is more significant. This study aims to reveal the natural history of paraclinoid aneurysms that are covered and anatomically “protected” by the surrounding dura and the bone. Patients with paraclinoid aneurysms with 50 to 100% of the surface covered by the endocrania of the skull base were enrolled. During 2003 and 2017, 119 patients with 125 aneurysms were prospectively followed for up to 15 years using MRA with a 6- to 12-months interval. Not a single instance of subarachnoid hemorrhage was observed in the series. In addition, no aneurysm showed enlargement or transformation during the observation period (642 aneurysm-years). Based on the observation of the very benign natural history of these paraclinoid aneurysms, surgical or endovascular intervention should not be recommended during the first diagnosis. Moreover, they should be kept under close follow-up observation with repeat MRA.

Gamma knife radiosurgery (GK) is a standard treatment for AVMs, but it tends to be avoided for cerebellar arteriovenous malformation (C-AVM) because of concerns about fatal posterior fossa hemorrhage before nidus obliteration. The goal of this study was to evaluate the long-term outcomes of GK for C-AVM. Sixty patients treated with GK between 1990 and 2015 were included in the study. The median age, volume, maximal diameter, and prescription dose were 42 years, 1.4 ml, 19 mm, and 20 Gy, respectively. Forty patients (67%) developed hemorrhage prior to GK. The cumulative obliteration rates were 49% and 79% at 3 and 5 years, respectively. A prescription dose of ＞ 20 Gy was associated with better obliteration via multivariate analysis. The 15-year significant neurological event (SNE)-free rate was 96%. The annual post-GK hemorrhage rates were 1.5% and 0.3% before and after obliteration, respectively. In conclusion, GK is a favorable alternative for C-AVMs, providing a high obliteration rate and very low risk of SNEs. The treatment strategy for C-AVM should be determined after considering the merits and drawbacks of surgery and GK.

Endovascular coil embolization of very small aneurysms (＜ 3 mm in maximum diameter) remains challenging and requires scrupulous attention to detail during treatment to overcome technical difficulties and mitigate high complication rates. We focused on techniques for positioning microcatheters into aneurysms.

In principle, we placed a balloon microcatheter across or proximal to the aneurysm neck and adopted a microcatheter that is usually shaped with steam according to the three-dimensional relationship of the vascular structure. If the angle between the long axis of the aneurysm and that of the parent artery is approximately 90°, we pulled back the microcatheter from the distal site to place the catheter in the aneurysm. In cases where the long axis of the aneurysm is nearly parallel to that of the parent artery, we often adopt the catheterization technique using of a preceding coil loop or, in anatomically inevitable cases, a preceding micro guidewire.

In this case report, we have described our endovascular coil embolization technique for very small aneurysms, focusing on the method of positioning the microcatheter into the aneurysm.

Here, we report a case of acquired pial arteriovenous fistula (AVF) supplied by both internal and external carotid arteries. The patient was a 69-year-old man who had subarachnoid hemorrhage due to a ruptured left middle cerebral artery aneurysm and underwent neck clipping in 2009. Magnetic resonance imaging revealed infarction in a portion of the left temporal lobe. Digital subtraction angiography demonstrated obstruction of the inferior trunk of the left middle cerebral artery and blood flow to the left temporal lobe through a leptomeningeal anastomosis from the left posterior cerebral artery. Follow-up digital subtraction angiography 9 years after the operation showed an AVF supplied by the middle meningeal artery, middle deep temporal artery, and artery of the foramen rotundum from the external carotid artery and by some branches of the middle cerebral artery from the internal carotid artery. The drainage route was the superficial Sylvian vein with retrograde cortical venous drainage. Endovascular embolization was performed using fiber coils, followed by surgical ligation of the AVF. The obvious fistulous point that connected the dura and the superficial Sylvian veins was not identified, but the AVF located on the brain surface was mainly supplied by the cortical middle cerebral arteries and drained into the Sylvian vein via a venous pouch. Therefore, we diagnosed a pial AVF. The fistulous point was removed after coagulation, and some arteries were cut and connected to the venous pouch. This case demonstrated the possibility of pial AVF supplied by both internal and external carotid arteries after cerebral infarction and craniotomy.

Brainstem cavernous malformations (BCMs) that present with hemorrhage are known to show a higher risk of rebleeding than that associated with cavernous malformations at other sites. We report a surgical case of a tectal cavernous malformation that manifested with post-hemorrhagic obstructive hydrocephalus in a 69-year-old-woman who presented with sudden headache and impaired consciousness. Computed tomography (CT) revealed tectal hemorrhage and acute hydrocephalus. Emergency ventricular drainage was performed; however, the patient's level of consciousness showed only slight improvement. CT performed on day 20 revealed a gradual increase in the size of the hemorrhagic area, suggestive of cavernous malformation-induced rebleeding. We performed microsurgical total resection of the midbrain mass via an occipital transtentorial approach, 5 weeks after onset. Postoperatively, the patient's level of consciousness and right hemiparesis recovered completely, her modified Rankin Scale score was 2, and she was independent at the time of discharge. Aggressive surgical resection is strongly recommended in patients with BCMs that manifest with hemorrhage, owing to the high risk of rebleeding and morbidity associated with this complication. This therapeutic strategy should be promptly considered using the appropriate approach based on the patient's health condition.

We report a case of a 53-year-old man who presented with progressive left eye chemosis and proptosis 1 year after craniotomy for hematoma evacuation. Cerebral angiography showed a combination of dural and pial arteriovenous fistulas (AVF), which were supplied by the middle meningeal arteries (MMA) and the middle cerebral arteries and drained into the Sylvian veins (SSV) as the common venous drainage. Endovascular embolization of the MMA and surgical disconnection of the pial arteries were performed, and the shunt was successfully removed. These unique shunts were acquired after the previous surgery, and seemed to be associated. We hypothesized that the injury of the SSV during the evacuation of hematoma primarily induced the formation of dural AVF and that the hemodynamic changes brought about by the development of the dural AVF led to the formation of pial AVF secondarily.

We report two cases of ruptured dissecting aneurysms of the vertebral artery (VA) involving the origin of the posterior inferior cerebellar artery (PICA), which were successfully managed thorugh proximal occlusion (PO) of the VA and PICA along with reconstruction of the PICA. Case 1: A 43-year-old male presented with subarachnoid hemorrhage (SAH) that was caused by a PICA-involved type of VA dissection. A PO along with the reconstruction of the PICA was performed because a massive and hard hematoma involving the lower cranial nerves (LCN) prevented the distal end of the dissection from being secured safely. Case 2: A 54-year-old male presented with SAH that was caused by a PICA-involved type of VA dissection was operated upon with this method because the anterior spinal artery (ASA) originating at the end of the dissection made it difficult to trap the entire lesion without compromising the ASA. Both patients eventually recovered without ischemic complications or LCN palsy (LCNP). Postoperative computed angiography demonstrated the disappearance of the dissection and good patency of the bypass.

;Although trapping of the entire lesion along with the reconstruction of the PICA is the first line of surgical management for PICA-involved type of VA dissections, high frequency of LCNP, and ischemic complications in the brain stem have been reported. PO with the reconstruction of the PICA is an effective alternative in cases with a high risk of LCNP or ischemic complications.