In 2016, the Japanese Society on Surgery for Cerebral Stroke established a surgical skill certification system for cerebrovascular surgery. Its purpose is to promote the training of doctors involved in stroke surgery, advance and develop surgical treatment strategies for stroke, improve the standard of medical care, and contribute to the welfare of the nation by ensuring basic standards for stroke surgery. In the same year, we began accrediting instructors who provide educational guidance to doctors aiming to become skill-certified. The Society established that an instructor must be a skill-certified surgeon. Initially, for a provisional period of three years (until 2018), surgeons with 10 years or more years of experience after being board-certified by the Neurosurgical Society were considered as candidate instructors.

In 2017, we started accrediting surgeons with proficient surgical skills for performing surgeries for cerebral stroke safely. Initially, the target surgeries used for video reviews were neck clipping of cerebral aneurysms, bypasses, and/or carotid endarterectomies. In 2019, we changed the surgical experience requirements and the target surgeries accepted for surgical video reviews. By 2022 (application for 2021), 6 qualified instructor examinations and 5 surgical skill certification examinations were conducted, resulting in 750 instructors and 346 surgical skill-accredited surgeons being certified. The certification period for both instructors and skill-certified surgeons is five years. Since 2021 and 2022, we have started accepting renewal applications for the initially certified instructors and skill-certified surgeons, respectively. This paper outlined the purpose of the skill-certification system and the progress made after seven years. We documented the history and the problems. Furthermore, future directions were discussed, including the establishment of a comprehensive stroke center.

Introduction: A preoperative understanding of local wall thinning and thickening may be useful for safe surgery in both microsurgical clipping and endovascular coiling for the treatment of cerebral aneurysms. Based on our computational fluid dynamics (CFD) analysis of cerebral aneurysms, we found that wall shear stress vector cycle variation (WSSVV) and oscillatory shear index (OSI) can predict local wall thinning or thickening. Preoperative CFD analysis using these parameters was introduced in 2019 to determine local aneurysm wall thinning and thickening.

Purpose: To demonstrate the effectiveness of these parameters during surgery.

Methods: This study included 42 patients (15 men and 27 women; mean age, 61 years) who had undergone cerebral aneurysm clipping at our hospital between January 2019 and August 2022. Among them, 18, 15, 8, 1 aneurysms involved the middle cerebral, internal catorid, and anterior commissural, basilar arteries, respectively (mean aneurysm size 5.9 mm). Considering the possibility of intraoperative rupture at the local thinning areas of the aneurysms, the proximal vessels were secured prior to exposure of the expected thinning areas, as if they were ruptured aneurysms. The thickened areas could cause stenosis of the normal vessel or incomplete occlusion of the aneurysm lumen during clipping. Therefore, care was taken when clipping the thickened areas.

Results: As expected, aneurysms harboring the predicted thickened areas were difficult to close with a single clip and required multiple clips. No cerebral infarction due to perforator or parent vessel injury or occlusion was encountered; however, intraoperative rupture (2.4%) from the predicted thinning area was reported in one patient. All patients were discharged without deterioration in modified Rankin Scale (mRS) scores.

Conclusion: A preoperative understanding of local wall thinning or thickening of unruptured cerebral aneurysms using CFD analysis facilitated safe surgery. With further improvements, this technique can be used not only for microsurgical clipping but also for endovascular treatment, in which the aneurysm wall cannot be directly visualized.

Background: We have been practicing the two-surgeon-three-handed surgical approach (three-hand surgery). This involves a young surgeon performing the operation and the attending surgeon supervising and assisting. The recent introduction of the 4K-three dimensional exoscope has enabled surgeons and assistants alike to access a clearer and wider surgical field. Here, we report our practice of three-hand surgery including how to avoid and deal with intraoperative difficulties during surgical clipping of the anterior circulation. Methods: The study included 965 patients who underwent surgical clipping for unruptured cerebral aneurysms in the anterior circulation between January 1, 2012 and October 31, 2021. Results: All patients underwent three-hand surgery and all operations were competed. At discharge (from the hospital), 23 (2.4%) patients decreased by 2 or more on the modified Rankin scale. The cause was stroke in 14 patients, optic neuropathy in 7 patients, and other disorders in 2 patients. Conclusions: Three-hand surgery for surgical clipping of unruptured cerebral aneurysms allows young surgeons to obtain experience and achieve appropriate outcomes, while ensuring patient safety.

Preservation of blood flow in perforating arteries is of paramount importance in aneurysm surgery to avoid devastating ischemic complications. Surgical strategies for internal carotid artery (ICA) aneurysms include: 1) detailed evaluation of the anatomy of the perforators and aneurysms in preoperative imaging, especially assessing the cerebrospinal fluid space around the perforator, parent artery, and aneurysm using construction interference in steady state (CISS) images, 2) performing a sufficiently wide craniotomy and creating a wide opening of the sylvian fissure to allow for multiple viewing angles, 3) thoroughly inspecting perforators under direct vision, with the aid of an endoscope when necessary, 4) meticulously dissecting perforators as freely as possible while avoiding injury to the aneurysmal wall, 5) placing clips with the utmost care, using a combination of clips when necessary to occlude the origin of the perforator, 6) confirming blood flow using indocyanine green (ICG) videoangiography and assessing the function of the corticospinal tract through motor-evoked potential (MEP) monitoring at the end of the procedure. One hundred sixty-one patients underwent surgical clipping of 170 ICA aneurysms between 2012 and 2021. Target aneurysms were located at the posterior communicating artery (PCoA) in 101 patients, anterior choroidal artery (AChA) in 49, bifurcation of the internal carotid artery (ICB) in 15, and C1 segment of the ICA in 5. No intra-operative ruptures were observed. Temporary occlusion of the ICA was performed in 44 procedures (27.3%) with a mean duration of 169.9 seconds. A combination of clips was used to occlude the origin of the perforator in 14 patients with AChA aneurysms. Changes in MEP amplitude was observed in six (3.7%) procedures; the MEP fully recovered after readjustment of the clip(s) in the procedures. Postoperatively, all 161 patients left the hospital with a modified Rankin Scale score of 0. Diffusion-weighted imaging (DWI) on postoperative day 4 revealed high-intensity lesions (DWHI) in the area of the perforators adjacent to the aneurysm in 15 patients (9.3%), all of whom were asymptomatic. Aneurysms located at the ICB showed the highest incidence (4/15, 26.7%), followed by those at the PCoA (9/101, 8.9%) and AChA (2/45, 4.4%). Seven (15.9%) of the 44 procedures with temporary ICA occlusion showed DWHI compared to 8 (6.8%) of the 117 procedures without temporary occlusion (p=0.076). One (16.7%) of 6 procedures with changes in MEP showed DWHI compared to 14 (9.0%) of 155 procedures without MEP changes. Meticulous surgical maneuvers and a combination of multimodal intraoperative monitoring can minimize ischemic complications due to compromised flow in the perforating arteries. Further refinement of surgical skills and analysis of the causes of potentially devastating lesions, i.e. asymptomatic ischemic lesions are the pre-requisites to progress toward the goal of “zero complications” in the preemptive procedures for unruptured intracranial aneurysms.

Carotid endarterectomy (CEA) for high cervical internal carotid artery (ICA) stenosis is challenging. The high cervical approach, a skull-based technique primarily used to address jugular foramen schwannomas, is useful for understanding the anatomy and for the successful removal of high cervical lesions. Herein, we present an anatomical description and demonstrate the upper limit of CEA and our internal shunt insertion technique for such difficult lesions. The internal jugular vein and lower cranial nerves are located above the ICA at the level of the C1 transverse process in the operative field, making it difficult to manage the ICA. Consequently, when an internal shunt catheter is used, the safe upper limit for CEA is at the level of the C2 body. For the upper limit, in difficult cases, the distal plaque should be treated first, thereby facilitating the insertion of the internal shunt.

Recent advances in imaging technology have made it possible to diagnose detailed vascular anatomy of the dural arteriovenous fistula (dAVF). At our institution, we have been working on the qualitative diagnosis of dAVF using slab maximum intensity projection imaging with digital subtraction angiography. These advances in imaging techniques have also contributed to determining of endovascular and surgical treatment strategies, leading to improved outcomes. In this issue, we will address new developments in diagnostic imaging for dAVF, presenting our findings and recent literature on each theme.

A 60-year-old man underwent trans-sphenoidal surgery for a pituitary tumor 30 years ago. He suffered massive bleeding during the surgery. The patient was transferred to our hospital because of anemia due to sudden massive epistaxis. The source of bleeding was a small aneurysm of the C3 internal carotid artery exposed through a bony window in the posterior wall of the sphenoid sinus. Consequently, a parent artery occlusion with high-flow bypass was performed. To date, the patient has been doing well. Injury to the internal carotid artery during trans-sphenoidal surgery and delayed pseudo-aneurysm formation are very serious complications.

A 50-year-old man presented with subarachnoid hemorrhage caused by a ruptured dominant vertebral artery dissecting aneurysm (VADA) involving the posterior inferior cerebellar artery (PICA) and the anterior spinal artery (ASA). In the acute stage, stent-assisted coiling (SAC) was performed at the rupture point while preserving the PICA and ASA. However, minor rebleeding occurred on POD8 due to insufficient coil embolization. Additional coil embolization was performed at the rupture site. Subsequently, the patient was discharged without further bleeding. After two months, dilation of the pseudolumen in the aneurysm was observed along with the occipital artery (OA)-PICA anastomosis. Therefore, coil embolization of the pseudolumen was performed. Deconstructive treatment, such as internal trapping of a ruptured VADA, is the first-line surgical treatment. However, for dominant VADA involving the PICA and ASA, this treatment is not the best option. Reconstructive treatment using SAC in the acute stage may offer prompt and effective therapy for preventing rebleeding, while preserving the PICA and ASA. Particular attention is required in cases of insufficient coil embolization. In the chronic stage, coil embolization of the pseudolumen combined with an OA–PICA bypass is curative.

Giant thrombosed aneurysms have a poor prognosis based on the risk of rupture-induced subarachnoid hemorrhage and the neurological deficit caused by the compression of surrounding tissues from further growth. In this case report, we described a patient with a giant thrombosed vertebral artery aneurysm that was successfully treated with two-stage embolization and thrombectomy. A 50-year-old man presented with nausea, appetite loss, and dysstasia that had persisted for several days. Magnetic resonance imaging (MRI) and angiography revealed a giant thrombosed right vertebral artery aneurysm, measuring 30 mm in diameter. The patient underwent two-stage surgery consisting of interventional occlusion of the parent artery followed by thrombectomy via craniotomy because the distal neck of the aneurysm was difficult to secure through direct surgery. The patient’s preoperative symptoms improved after the second surgery, with no additional neurological deficits. Neck clipping for giant thrombosed aneurysms was difficult because of the size of the aneurysm and the bleeding risk. The risk of intraoperative bleeding was reduced by occluding the parent artery while preserving the perforating branch of the brainstem. The pressure on the brainstem was released by removing the thrombus in the aneurysm via direct surgery. The adoption of these optimal strategies using hybrid neurosurgery resulted in a good outcome, despite the critical pathology of symptomatic giant thrombosed aneurysms.

Objective: This study discussed the treatment strategy for progressive enlargement of an asymptomatic vertebral artery (VA) dissection.

Case presentation: Seven years ago, a female patient in her 40s was diagnosed with a left vertebral artery dissection (17 mm×5 mm) after undergoing an examination for headaches. Over seven years, the dissection expanded to 24 mm×9 mm, leading to a referral to our clinic. At the time of referral, the patient was asymptomatic with no neurological deficits or headaches. Angiographic findings revealed that the left VA exhibited contralateral meandering after entering the intracranial region. The lesion was longitudinally extensive, posing challenges in securing the peripheral side through a lateral suboccipital approach. In open surgery, it is feasible to occlude the proximal portion of the VA and perform an occipital artery to posterior inferior cerebellar artery (OA-PICA) bypass. However, accessing the VA-PICA branching site and the distal portion of the dissection from the suboccipital approach presents difficulties. Endovascular treatment raises concerns including ischemic complications, particularly for large partially thrombosed VA dissections. For our patient, we opted for a craniotomy with an OA-PICA bypass and proximal occlusion of the VA, without closing the VA-PICA bifurcation. Postoperatively, thrombosis of the dissection was observed. No infarction in the PICA region occurred. The patient was discharged without neurological complications. Conclusion: In cases of PI-CA-involved VA dissections, OA-PICA anastomosis and proximal VA occlusion may promote aneurysm thrombosis without necessitating the closure of the VA-PICA branch.

An 82-year-old woman was diagnosed with extracranial carotid artery aneurysms (ECAAs). These aneurysms were resected using the posterior cervical triangle. The patient had transient right paresis and a left cervical aneurysm, measuring a maximum diameter of 72.2 mm. Six years earlier, a left cervical aneurysm of 24.1 mm in diameter was detected but the patient was asymptomatic during follow-ups. Diffusion-weighted magnetic resonance imaging revealed a fresh cerebral infarction in the left frontal cortex. The surgical procedure consisted of a skin incision from the mastoid process along the anterior margin of the sternocleidomastoid muscle and an L-shaped incision extending outward over the clavicle from its lower edge. Proper field development during extracranial carotid artery aneurysm surgery and the selection of an appropriate surgical technique are both important. In this case, the internal jugular vein was riding on the outer wall of the aneurysm and was firmly attached to the surrounding tissues. Thus, an internal shunt was placed and an arteriotomy was performed. Although the intima was smooth and normal, the aneurysm was filled with organic thrombus. After dissecting the aneurysm from the surrounding tissues, the aneurysm was removed, and the normal vessel wall was sutured.