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ObjectiveTo evaluate whether an occlusion pathomechanism can be accurately determined by common preprocedural findings through a machine learning-based prediction model (ML-PM).MethodsA total of 476 patients with acute stroke who underwent endovascular treatment were retrospectively included to derive an ML-PM. For external validation, 152 patients from another tertiary stroke center were additionally included. An ML algorithm was trained to classify an occlusion pathomechanism into embolic or intracranial atherosclerosis. Various common preprocedural findings were entered into the model. Model performance was evaluated based on accuracy and area under the receiver operating characteristic curve (AUC). For practical utility, a decision flowchart was devised from an ML-PM with a few key preprocedural findings. Accuracy of the decision flowchart was validated internally and externally.ResultsAn ML-PM could determine an occlusion pathomechanism with an accuracy of 96.9% (AUC=0.95). In the model, CT angiography-determined occlusion type, atrial fibrillation, hyperdense artery sign, and occlusion location were top-ranked contributors. With these four findings only, an ML-PM had an accuracy of 93.8% (AUC=0.92). With a decision flowchart, an occlusion pathomechanism could be determined with an accuracy of 91.2% for the study cohort and 94.7% for the external validation cohort. The decision flowchart was more accurate than single preprocedural findings for determining an occlusion pathomechanism.ConclusionsAn ML-PM could accurately determine an occlusion pathomechanism with common preprocedural findings. A decision flowchart consisting of the four most influential findings was clinically applicable and superior to single common preprocedural findings for determining an occlusion pathomechanism.

Ischemic complications including silent or symptomatic events are known to occur during the clipping of intracranial aneurysms, although at a relatively lower rate than during endovascular treatment. An atherosclerotic or calcified neck is one of the major contributors to postoperative ischemic sequelae from a surgically treated aneurysm. Atherosclerotic changes in intracranial vessels or within an aneurysm wall or neck area are often seen during surgery. However, we were not previously able to detect any showering of atheromatous emboli during temporary or permanent clipping procedures. We describe a case of an intra-aneurysmal rupture of a squeezed atheroma observed after permanent clipping of an atherosclerotic large middle cerebral artery aneurysm. After tentative clipping to treat the severe atherosclerotic aneurysm in this patient, we applied supplementary clipping to the atherosclerotic area of the aneurysmal sac. The resulting squeezing of the intra-aneurysmal atheroma caused a leakage into the subadventitial layer of the aneurysmal sac. We also discuss the potential ischemic complications of aneurysmal clipping surgery. We conclude that the surgical techniques used to treat these specific aneurysms require circumspect planning through a review of preoperative images.

Background We reviewed our clinical experience of patients with moyamoya disease (MMD) who gave birth and assessed characteristics of those experiencing neurologic deterioration. Methods The patients were classified into patients diagnosed with MMD during pregnancy and puerperium (group 1) and those diagnosed before pregnancy (group 2). We retrospectively reviewed patient characteristics, MMD treatment, neurologic symptoms before and during pregnancy and/after puerperium, obstetrical history, and delivery type in groups 1 and 2. Results Group 1 included 2 patients with deterioration of pre-existing transient ischemic attacks (TIAs) and acute cerebral infarction and 1 patient with seizures and newly developed TIAs during pregnancy and/or puerperium. Group 2 included 20 patients with 23 pregnancies. In group 2, 4 patients had deterioration of TIAs during pregnancy and puerperium. There were significant differences between the cases without neurologic deterioration and with deterioration in group 2 (TIAs ≥10 before pregnancy, 0% vs. 75%, P = 0.002; severely reduced regional cerebrovascular reserve on single-photon emission computed tomography, 10.5% vs. 100%, P = 0.002; and surgical revascularization before pregnancy, 75% vs. 15.8%, P = 0.04). In groups 1 and 2, 6 of the 7 cases in which TIAs occurred or worsened during pregnancy or puerperium recovered to prepregnancy TIA levels after puerperium. Conclusions Patients with severely reduced regional cerebrovascular reserve on single-photon emission computed tomography and frequent TIAs before pregnancy may experience neurologic deterioration during pregnancy, delivery, and puerperium. Surgical revascularization before pregnancy may decrease neurologic deterioration during these periods.

Background There are several treatment modalities for vertebral dissecting aneurysms. The purpose of this study was to evaluate the efficacy and safety of triple stent therapy for intracranial vertebral dissecting aneurysm (VDA). Methods Eight patients with 9 VDAs underwent multiple stent insertion therapy. Seven patients who presented with progressive ischemic symptoms and showed changes in follow-up images underwent triple stent insertion therapy, and 1 patient who presented with subarachnoid hemorrhage underwent double stent therapy twice and 1 additional single stent therapy with coil embolization (total 5 stents). Safety, technical feasibility, clinical, and imaging follow-up data for triple stent therapy were retrospectively evaluated. Results Triple stent deployment for VDAs was successfully performed in all 9 VDAs without any procedure-related complication. Among them, 8 unruptured VDAs showed near normalization on follow-up imaging studies within 90 days after the procedure. One case of ruptured VDA showed repeated recurrence without new symptoms and delayed normalization after insertion of 5 stents. Seven patients with long-term follow-up (median clinical follow-up, 22.6 months; median imaging follow-up, 17.1 months) showed clinical and imaging improvement without development of new symptoms. Conclusions Triple stent therapy for VDAs was safe and effective. This technique showed favorable results in clinical and imaging follow-up for unruptured VDAs, although caution is advised for ruptured VDAs.

Background Cranial defects following anterior cranial base surgery have been frequently reconstructed using the pericranial flap. Methods We present a simple technique for preparing the flap using injection of saline into the subgaleal space. Results We inserted a 20-gauge needle perpendicular to 8–10 spots in the frontal area and injected 5–7 mL of saline at each spot 10 minutes before skin incision. Distinctive swelling of the scalp was then observed. After the scalp was incised, the layers were dissected with a monopolar electrocautery device. The layer containing saline allowed us to better localize its exact position and harvest the flap without injury. Dissection in the subgaleal plane was performed mainly using the tip of a surgical blade. After the periosteum was stripped from the calvaria, the flap that had been considerably thickened by saline injection was harvested. Conclusions Because pericranium thickness in the frontal areas is reported to be thinner than in other areas, a beginning neurosurgeon may have difficulty harvesting an anteriorly based flap of sufficient size. The technique presented here can help increase awareness of the subgaleal layer, facilitate the dissection process, and reduce additional tissue injury resulting from electrocautery manipulation.

Superficial temporal artery (STA) to middle cerebral artery (MCA) bypass is associated with several surgical problems. Despite the vascular patency and hemodynamic changes after the anastomosis, wound problems can be a major surgical complication.In a review of 41 surgical cases of STA-MCA bypass for moyamoya disease or cerebral occlusive vascular disease, we compared the conventional (out-to-in) dissection method for STA (n = 23) with the in-to-out (ITO) dissection method (n = 18) and evaluated the surgical results with respect to wound problems.The incidence of skin maceration was significantly higher in the conventional dissection group than the ITO dissection group (34.8% vs. 5.5%; P0.01). Skin necrosis also showed a higher incidence in the conventional dissection group (39.1%) than the ITO group (22.2%).These data suggest that the simple layering technique of the ITO dissection method can protect against contamination from bacteria and reduce postoperative surgical wound problems. Sealing of the galea aponeurotica (first protective barrier), including fibrous septa and loose areolar tissues, including the periosteal layer (second protective barrier), is an important factor to decrease the rate of scalp wound infection.

Although new imaging tools have been developed for the detection of smaller aneurysms, angiographically negative microaneurysms are still encountered during cerebral microsurgery. Currently, only limited information regarding incidence and efficacy of treatment of these microaneurysms is available.We investigated the incidence and treatment of incidental microaneurysms (IMAs) in the last 5 years. IMAs are unidentifiable and invisible on preoperative angiography, but are detected during microvascular surgery. The inclusion criteria were aneurysm cases treated with microsurgery via transsylvian approaches, and those undergoing preoperative digital subtraction angiography.This study enrolled 484 surgical cases (248 cases of subarachnoid hemorrhage and 236 cases of unruptured aneurysms) in 460 patients, and 33 tiny aneurysms were found in 31 operative cases (6.4% incidence per operation). The most typical type was located on another branching site of the middle cerebral artery found during neck clipping of the middle cerebral artery bifurcation aneurysm. A patient with multiple aneurysms presented a statistically significant risk (375/78 vs. 15/16; P0.001) of IMA identification. IMAs were treated by clipping and wrapping in 18 and 15 cases, respectively, without complications.This study revealed a 6.4% incidence of IMAs; however, this could be underestimated because of the limited range of inspection. Early detection of an IMA through careful inspection during microvascular surgery could be beneficial, especially in patients with multiple aneurysms.

AIM For endovascular embolization of paraclinoid aneurysms, superselection needs consideration of the complex anatomy around the carotid siphon. As no guideline or classification has been established for selecting proper microcatheters, pre-shaped microcatheters must be considered. We suggest a geometric classification of paraclinoid aneurysms for microcatheter selection. MATERIAL AND METHODS Clinical data from 76 patients (80 paraclinoid aneurysms) who underwent endovascular treatments were retrospectively reviewed. Paraclinoid aneurysms were classified according to the six directions where the aneurysm neck lies and simplified into three groups as follows: superior, medial, and lateral groups. The medial group was further divided into proximal, mid, and distal subgroups according to the location of the aneurysm neck on lateral angiography. Furthermore, we assessed the superselection success rate with the first-selected pre-shaped microcatheter per group. RESULTS According to the aneurysm direction, the medial group showed relatively lower superselection success rates (66.1%) than the superior (81.8%) and lateral groups (85.7%). The S-shaped microcatheter was the most frequently used in the superior (69.2%) and lateral groups (62.5%). Acute-angled J- and C-shaped microcatheters (88.5%) were preferred for proximal aneurysms; and obtuse-angled 45° - and 90°-angled microcatheters (75%), for distal aneurysms. The mid-portion group showed the lowest success rate (45.8%) and more difficulties in pre-shaped microcatheter superselection. CONCLUSION Medially directed mid-portion aneurysms were difficult to access using pre-shaped microcatheters; thus, tailored steam-shaping techniques may be considered. Superiorly and laterally directed aneurysms could be accessed using pre-S-shaped microcatheters. Acute-angled microcatheters may be considered for proximal aneurysms; and obtuse-angled microcatheters, for distal aneurysms.

We report a case of dural arteriovenous fistula (DAVF) that showed spontaneous conversion of venous drainage pattern from Borden type II to type III within a four month period of follow-up. Upon admission, the patient presented with aggravated neurologic status and newly developed seizure. After admission, endovascular embolization was performed through the middle meningeal artery with Onyx®. Complete obliteration of dural arteriovenous shunt was confirmed by angiography, and the patient's clinical symptoms improved. Although most cases of DAVF show benign clinical course and conversion pattern, close follow-up is required to detect potential aggravation.

Background Many methods for treating complex anterior cerebral artery (ACA) aneurysms are available; however, there is substantial variation among methods because of various aneurysm locations, the relationship of the aneurysm to arterial branches, aneurysm size and other morphologic characteristics, and the diameters of the parent or branching arteries. Methods We reviewed complex ACA aneurysms based on both our own experience and the available literature. Each unique case is analyzed in terms of the characteristics of the aneurysm, along with analysis and classification of the revascularization method used. Computer tablet–drawn illustrations of each unique technique are provided for comprehension and application in various situations. Results Over 6 years, we treated 5 cases of complex ACA aneurysms (1 precommunicating, 1 communicating, 1 postcommunicating, and 2 precallosal-supracallosal segment) with revascularization. Side-to-side anastomoses included pericallosal ACA segment-pericallosal ACA segment in 3 cases, supracallosal ACA segment-supracallosal ACA segment in 1 case, and ipsilateral callosomarginal artery-pericallosal artery in 1 case. Final modified Rankin scale score was 0 in 4 of 5 cases and 3 in 1 case. Six treatment strategies were used for the precommunicating aneurysm, 8 for the communicating aneurysm, 7 for the postcommunicating aneurysm, and 9 for the 2 precallosal-supracallosal segment aneurysms. Conclusions Treatment of complex ACA aneurysms should be tailored according to the location and nature of the aneurysm and collateral circulation. Viable and feasible treatment strategies must be established by the neurovascular surgeon.

In situ side-to-side (STS) anastomosis is a unique technique used for intracranial artery-intracranial artery revascularization. Over a 7-year period, 7 STS anastomoses were performed for anterior cerebral artery aneurysms in 6 patients and a posteroinferior cerebellar artery aneurysm in 1 patient. We provide a step-by-step guide for suturing techniques from arteriotomy to vessel wall sutures based on clinical experiences, with detailed illustrations. Technical considerations in each stage are also discussed. The current technique provides a viable option for treatment of complex aneurysms.

A relevant irrigating and flushing maneuver during cerebral microsurgical procedures allows for a neat and optimal operative field. However, when operating on the deep region of the brain, a delicately created slim surgical corridor could unintentionally hinder the assisting surgeon from properly performing this routine maneuver. To address this problem, the authors devised a useful and convenient irrigation system that can be used during cerebral microsurgery. This system only necessitates a readily available silastic feeding tube and a malleable wire. The advantages of our devised system include the convenience of free molding, good endurance of the molded contour, and easy control over the amount of irrigation. In this report, the authors demonstrated technical tips for using this newly devised system.

Pseudoaneurysm on the distal anterior cerebral artery (ACA) is rare but potentially fatal. It usually cannot be treated with typical treatment modalities. A 47-year-old female patient was diagnosed with a ruptured aneurysm on the pericallosal artery (PerA). During surgical exploration, it was found to be a pseudoaneurysm and could not be treated with clipping. We performed surgical trapping of the involved segment of the proximal PerA followed by side-to-side anastomosis between the ipsilateral PerA and the callosomarginal artery. The patient recovered without any neurologic deficit. This new method of anastomosis could be an alternative option.

Objective To provide detailed information about how to realize a self-training laboratory with cost-effective microsurgical instruments, especially pertinent for the novice trainee. Methods Our training model is designed to allow the practice of the microsurgery skills in an efficient and cost-effective manner. A used stereoscopic microscope is prepared for microsurgical training. A sufficient working distance for microsurgical practice is obtained by attaching an auxiliary objective lens. The minimum instrument list includes 2 jeweler's forceps, iris scissors, and alligator clips. The iris scissors and alligator clip provide good alternatives to micro-scissors and microvascular clamp. Results The short time needed to set up the microscope and suture the gauze with micro-forceps makes the training model suitable for daily practice. It takes about 15 minutes to suture 10 neighboring fibers of the gauze with 10-0 nylon; thus, training can be completed more quickly. Conclusions We have developed an inexpensive and efficient micro-anastomosis training system using a stereoscopic microscope and minimal micro-instruments. Especially useful for novice trainees, this system provides high accessibility for microsurgical training.

Introduction Deep bypass surgery remains a challenging operative procedure. For novice trainees, there is a high barrier to improving the microsurgical skills needed for this procedure because of the relatively low number of cases and the high cost of microsurgical instruments. Here, the authors introduce a training model that includes highly accessible devices and does not require a microscope. Materials and Methods The surgical environment consisted of two 15.5-cm straight serrated forceps with a 1-mm tip width (Medicon, Tuttlingen, Germany), 9-cm curved iris scissors (Medicon), 4-0 black silk suture, gauze, and a 15 × 10.5 × 3.5-cm-sized box with a transparent cover. These materials are affordable even in low-income countries. Procedure To understand and learn the hand positioning used in the deep surgical field, suturing practice was performed as follows: the forceps and a needle were placed in a slanted position, with hand position maintained at a 50° angle between the 2 forceps. This was also performed above the desk, without wrist support. Conclusions Our training system will be helpful, especially for deep bypass surgery, since training with similar muscle effort and fatigue can improve surgical skills. This system is economic, highly accessible, and available even for portable training.

Purpose This report describes the need for a tailored approach for intracranial vascular occlusive disease and introduces the usefulness of the OA as a donor artery for interposition graft. Materials and Methods A 65-year-old male patient suffered from repeated transient ischemic attack (TIA). Imaging studies revealed complete occlusion of the proximal left side of the internal carotid artery (ICA) and multiple infarction in the watershed zone. We planned superficial temporal artery-middle cerebral artery (STA-MCA) bypass to restore cerebral blood flow and to prevent the progression of infarction. However, the parietal branch of the STA was too small in diameter and not suitable as a single donor for the bypass in order to supply sufficient blood flow. Moreover, the frontal branch of the STA had collateral channels through the periorbital anastomosis into the cerebral cortex that could result in infarction during clamping for anastomosis. Results We determined that tailored treatment planning was necessary for successful revascularization under these conditions. Thus, we performed a bypass between the parietal branch of the STA and a cortical branch of the MCA as an “insurance bypass.” Then we performed another bypass between the frontal branch of the STA and a cortical branch of the MCA using an ipsilateral occipital artery (OA) interposition graft. The patient had no perioperative complications, and postoperative imaging confirmed the restoration of cerebral blood flow. Conclusion When end-to-side anastomosis in single-branch bypass is not appropriate for cerebral revascularization, a tailored double-barrel “insurance bypass” with an OA interposed graft could be a good alternative treatment modality. In addition, an OA interposition graft is a useful option for double-barrel bypass surgery in such cases of intracranial vascular occlusive disease.

Objective Isolated dissections that develop on the posterior inferior cerebellar artery (PICA) require intensive treatment because of their potential fatality. However, because of the rarity of these dissections, the optimal treatment has not yet been established. Methods We retrospectively reviewed the clinical records of all patients who underwent any PICA dissection treatment in our institute over the last 4 years. Ten patients were enrolled, including 7 patients with subarachnoid hemorrhage (SAH) and 3 with PICA territory infarction. Dissection was seen at the proximal portion in 8 patients, whereas the remaining 2 patients showed distal PICA dissecting aneurysms. Results Among the 7 patients with hemorrhage, 5 were actively treated (trapping and bypass, 2 patients; surgical clipping, 1 patient; coil embolization, 2 patients). Conservative management was performed in the other 2 patients. Among the 3 patients with infarction, 2 received conservative treatment. Endovascular treatment was performed in 1 patient, who showed rapid progression, aneurysm formation, and conversion to massive SAH within 10 days after the initial attack. Although 7 patients showed relatively good outcomes (modified Rankin Scale score, ≤2) after 30 days of follow-up, 1 patient had a final modified Rankin Scale score of 3. In addition, the other 2 patients (1 in each group) died as a result of major SAH. Conclusions Given the dynamic clinical course and potential fatality of PICA dissection, meticulous evaluation, intensive treatment with a diverse range of modalities, and proper follow-up are required for patients with PICA dissection to achieve favorable outcomes.

Background Venous infarction in the brainstem caused by venous congestion is an extremely rare complication of traumatic carotid cavernous fistulas (CCFs). This condition requires immediate treatment and a multimodal treatment strategy is needed to prevent recurrence. Case Description A 24-year-old man presented with exophthalmos and chemosis after a bicycle accident. Cerebral angiography showed an engorged right superior ophthalmic vein and a right carotid cavernous fistula. Transvenous coil embolization was successfully performed without severe complications. Two months later, a decline in mental status occurred. Follow-up angiography showed recanalization of the CCF. The patient underwent radial artery graft bypass surgery combined with endovascular trapping of the internal carotid artery. Sylvian veins and other cortical veins became intraoperatively arterialized and we observed marked brain edema after high-flow CCF. After surgery, the patient's mental status recovered and angiography showed good patency of the bypass graft and complete obliteration of the recurrent CCF. Conclusions To ensure prevention of recurrent CCF, internal carotid artery trapping combined with high-flow bypass surgery can be a good salvage treatment for urgent cases in which an endovascular approach already failed.