[Transverse Sinus / Sigmoid Sinus].

The transverse sinus(TS)and sigmoid sinus(SS)are common sites for dural arteriovenous fistulas, and an understanding of vascular anatomy is important when developing treatment strategies. In recent years, transarterial embolization, with a liquid embolization material, has become the treatment of choice, preserving the sinus without extensive coil filling of the affected sinus. With this expansion of therapeutic options, we feel that an understanding of the microanatomy has become more important. For example, the exact site where the vein of Labbé joins the TS should be determined. This article focuses on the development and anatomy of the TS and SS and makes points that should be considered when treating dural arteriovenous fistulas.

Relationship between Shape Retention and X-ray Absorption Value of the Tip of Microcatheters in Neuroendovascular Treatment.

Objective We noticed that the X-ray absorption value of the tip of each microcatheter used for aneurysm treatment varied from product to product. We hypothesized that the differences were caused by variations in the metal's density braid, which could be related to the ability of the tip to retain its shape. Methods The X-ray absorption value of each microcatheter tip was measured. Next, heat forming was performed using a shaping mandrel at 6 mm and 90 degrees to determine whether there was a correlation between the X-ray absorption value and the forming angle. Next, the optimal mandrel angle for forming each microcatheter at 90 degrees was investigated. We also examined the shape retention after 20 times wire insertions into each microcatheter. Conclusion It was found that the higher the X-ray absorption value, the harder it was for the microcatheter to be formed. The mandrel angle required to form 90 degrees was determined by the X-ray absorption value. The higher the X-ray absorption value, the higher the shape retention of the tip shape. The heat formation and shape-retention conditions of the microcatheter tip were correlated with the X-ray absorption value of the metal braid. Even for unknown microcatheters, the optimum shaping conditions can be inferred from the X-ray absorption value.

Hairball-Like Migration of "Onyx Threads" into the Draining Vein during Transarterial Embolization of a Dural Arteriovenous Fistula: A Case Report and Experimental Validation.

Transarterial embolization using Onyx is a well-established treatment for dural arteriovenous fistulas (DAVFs). However, complications can arise when Onyx migrates into the venous side, impairing the draining veins. We encountered a case where Onyx, injected through the arterial side, strayed into the jugular vein, forming a hairball-like structure. Our study aimed to investigate the underlying mechanism of this unusual phenomenon. We postulated that Onyx precipitates into thread-like shapes when passing through extremely narrow openings. To test this, we extruded Onyx from a syringe through a 27-gauge needle into a silicone tube with flowing water. By varying the flow speed, we observed the hardening behavior of Onyx. Under slow flow, the extruded Onyx quickly solidified at the needle tip, forming a round mass. Conversely, high-speed flow resulted in Onyx being dispersed as small pieces. We successfully replicated the formation of "Onyx threads" under continuous slow flow conditions, similar to our case. This phenomenon occurs when Onyx unexpectedly migrates to the draining vein through a tiny opening during transarterial embolization for arteriovenous shunt diseases. Early recognition and appropriate measures are necessary to prevent occlusive complications in the draining veins and the pulmonary system.

A Novel Approach to Neuroendovascular Treatment Looking Up from the Ascending Aorta Using an Alpha Shape Guiding Catheter.

BACKGROUND: A method of guiding an intermediate catheter from a new alpha-type guiding catheter placed in the ascending aorta to the carotid artery is evaluated in neuroendovascular treatment in challenging anatomic directions of the guiding catheter, such as the bovine aortic arch and type III aortic arch. METHODS: The existing 8-Fr guiding catheter was given a strong bending shape at the tip to make it an alpha type. The total length of the catheter was 85 cm. This guiding catheter was inserted into the ascending aorta to verify whether a 6-Fr intermediate or aspiration catheter could be coaxially guided into the right and left internal carotid arteries. A silicone vascular model was used for evaluation and in actual clinical cases. RESULTS: Creating an alpha shape of the catheter at the aortic arch was very easy. The inner catheter could be easily guided from the brachiocephalic artery to the right common carotid artery by pushing the alpha shape guiding catheter toward the aortic valve. The catheter was easily guided into the left common carotid artery when the α-guide was pulled a little bit backward. The 0.071-inch lumen aspiration catheter reached the bilateral middle cerebral arteries. CONCLUSIONS: The 8-Fr alpha shape guiding catheter quickly guides the inner catheter into the bovine and the type III aortic arch by looking up from the ascending aorta.

A novel remote hands-on training for neuroendovascular-based treatment in the era of the COVID-19 pandemic.

The COVID-19 pandemic has demanded a change in learning modalities, which led us to develop a remote personal training system for clinicians performing neuroendovascular procedures. A portable vascular model designed for practicing catheter navigation guidance, thrombus retrieval, and intracranial aneurysm coil embolisation was established. We created an environment that enabled interactive dialogue and communication across long distances using the Internet. The instructor conducted approximately 2 h of hands-on training with two to four trainees at a time. Despite the restrictions enforced by the Government of Japan due to the COVID-19 pandemic, 17 online hands-on training were successfully conducted throughout Japan over 1 year for a total of 48 trainees. The developed remote training programme, to avoid the aggregation of a large number of trainees at a developed time, proved to be at par with the conventional learning system. The training was well-received since the operation time was longer and the question and answer sessions were more fulfilling compared to the conventional format in which a group of trainees had got a brief opportunity to receive actual hands-on experience.

Positional Relationship between Two Microcatheters according to the Navigation Sequence within the Curved Vessel in Neuroendovascular Procedures.

In neuroendovascular treatment, there are many opportunities to guide multiple catheters into the intracranial blood vessels. We report the relationship between two microcatheters according to the guiding order with experimental in vitro studies. We hypothesize that in a bent blood vessel such as a paraclinoid region of the internal carotid artery, the catheter that was first guided tended to pass through the inside, and the catheter that was guided later tended to pass through the outside. The in vitro verification was performed using a microcatheter and a balloon catheter in a silicone vascular aneurysmal model. As a result, it was found that the two catheters were arranged according to our hypothesis. This finding was also observed during the actual operation of balloon-assisted coil embolization. The positional relationship between the two catheters according to the navigation order is very important, in particular during balloon-assisted coiling and stent-assisted coiling via a jailed microcatheter.

Usefulness of a Curved Multiple Reconstruction Image for Transarterial Intravenous Coil Embolization of a Dural Arteriovenous Fistula of the Sphenobasal Vein: A Case Report.

Hemorrhagic isolated dural arteriovenous fistulas (DAVFs) are often challenging to treat. Here, we report a case of the lateral cavernous sinus (CS) DAVF successfully treated by transarterial intravenous coil embolization using a curved multiplanar reconstruction (MPR) image assistance. A 54-year-old man presented with a severe headache and was diagnosed with subarachnoid hemorrhage caused by CSDAVF. Angiography indicated that the fistula was fed by branches of the left external carotid artery and drained into cortical veins. There were multiple shunting points at the left sphenobasal vein accompanied by varicose veins. Using curved MPR images, the left accessory meningeal artery was chosen for the endovascular approach into the affected veins, including ruptured varix. The shunt was completely occluded by detachable coils. When the curved MPR image indicates a developing feeding artery and a large shunting point, transarterial intravenous coil embolization becomes a good treatment option for CSDAVF, which has no venous access.

Experimental Study of Coil Compaction: Impact of Pulsatile Stress.

Objective: Coil compaction after aneurysm embolization is one of the major issues associated with aneurysm recurrence. On the presumption that pulsatile stress to the aneurysm is responsible for coil compaction, we developed an experimental model in vitro to visualize the mechanical stresses exerted by blood pressure and pulse and their relation to coil compaction. Methods: A closed-type non-circulation system was developed by installing a syringe that generated pressure at one end of a tube, along with a spherical aneurysm made of silicone and a pressure sensor in the bifurcated end. We installed a fixed-pressure model under a steady pressure of 300 mmHg while the pressure-fluctuation model simulated the pressure variations using a plunger (in a syringe) by using a motor that applied pulsatile stress in the range of 50 mmHg for a 10-ms cycle. We devised four types of aneurysms with different depths and the same coil length. After coil packing, the aneurysms were observed for 3 days (the observation period in the pressure-fluctuation model corresponded to approximately 300 days in real time). The distance from the datum point to the observable coil loops was determined as the initial position, and the temporal change in the distance from that position was measured. Results: In the fixed-pressure model, the average distance of coil movement was very small (less than ±0.1 mm). In the pressure-fluctuation model, the movement of coils was observed to be significant for the two longest depths (0.11 and 0.14 mm). The maximal dynamic change in coil movement was observed on the second day. The range of movement was observed to decrease thereafter. Conclusion: Our experimental study enabled the observation of coil movement within a short duration. It examined coil compaction by applying pulsed pressure to the coils at high speeds. Consequently, a shift of the coil loops inside the incompletely occluded aneurysms was detected on applying a pulsed pressure.

A Novel Technique of Microcatheter Shaping using Real Image Display for Endovascular Aneurysmal Coil Embolization.

In coil embolization of intracranial aneurysms, guiding the microcatheter to an appropriate site in the aneurysm and stabilizing it there are important. In paraclinoid internal carotid aneurysms, complicated three-dimensional (3-D) shaping of the microcatheter tip is occasionally required. We devised a novel shaping method for microcatheters by using a real image display (RID). The usefulness of this technique was validated. We used a RID consisting of a couple of concave mirrors. A piece of patient-specific vascular model, which was made using a 3-D printer before the operation, was set inside the RID. We obtained a real 3-D image just above the RID. As a microcatheter and its shaping inner mandrel could be entered in the hologram of the vasculature, we could create the actual shape of the microcatheter. The shaped microcatheter could be navigated at the desired position in the aneurysm. Complete obliteration of the aneurysm was achieved without any trouble among 30 consecutive cases. We evaluated the effectiveness of the RID for making and navigating a microcatheter in cases with challenging anatomies. It was useful for favorable microcatheter shaping, as the RID could be entered inside the aneurysm models, unlike when tracing the outer surface of rigid 3-D models.

Safety and Effectiveness of a Modified ASAP Technique during Mechanical Thrombectomy for Acute Ischemic Stroke: Initial Clinical Experience.

OBJECTIVES: For patients with acute ischemic stroke, various endovascular approaches have been reported with high recanalization rates and good clinical outcomes. However, the best technique for the first attempt at mechanical thrombectomy remains a matter of debate. In this study, we evaluated the efficacy of a modified version of a stent-retrieving into an aspiration catheter with a proximal balloon (ASAP) technique. MATERIALS AND METHODS: Modification 1: After stent deployment, the microcatheter was not removed immediately. Modification 2: After the withdrawal of the stent retriever into an aspirator and its removal from the entire system, we focused on the drainage of fluid into a pump. The aspirator was withdrawn slowly until the fluid appeared to be draining continuously into the pump. Before the removal of the aspirator, we performed angiography through the aspirator. We carried out a retrospective analysis of 30 consecutive patients with acute ischemic stroke caused by occlusion of the anterior circulation who were treated with the modified ASAP technique at our institution. RESULTS: A thrombolysis in cerebral infarction score of 2B or 3 was achieved in 29/30 patients (96.7%). The average number of passes was 1.2 ± 0.5. The mean time from puncture to recanalization was 17.6 ± 6.84 min. Twenty-three (76.7%) patients achieved a modified Rankin Scale score of 0-2 at 3 months after the procedure. CONCLUSIONS: We found that the modified ASAP technique yielded fast recanalization, minimal complications, and good clinical outcomes of mechanical thrombectomy in this case series.

Experimental Evaluation of the Risk of Distal Embolization during Endovascular Clot Retrieval Using Various Techniques.

BACKGROUND: This study was conducted to evaluate various devices and techniques for endovascular thrombectomy that can reduce the risk of intraprocedural distal embolism in a preliminary in vitro setting with different types of thrombi. MATERIALS AND METHODS: Endovascular clot retrieval was performed in a vascular model with collateral circulation. White and red thrombi were prepared using whole blood collected from a pig. A Direct Aspiration First Pass Technique (ADAPT), simple stentretrieving with and without proximal flow arrest by a guiding balloon (SR [B+] and SR [B±]), the AspirationRetriever Technique for Stroke (ARTS), and A stentretrieving into an Aspiration catheter with Proximal balloon (ASAP) were performed three times, respectively. The saline samples that were collected at the distal side during each procedure were examined using a particle counter. The particles were counted and categorized into three groups based on size (100 µm). RESULTS: SR (B-) and SR (B+) could not achieve complete retrieval of the clot, especially using the white thrombus. ASAP was the only method that was able to retrieve the clots in all attempts. In both clot types, SR (B-), SR (B+), and ARTS, which involved a temporary flow restoration through stent deployment, demonstrated the migration of a greater number of particles measuring >100 µm in size than that shown by ADAPT and ASAP. CONCLUSIONS: ASAP was the safest method in terms of intraprocedural clot migration among the five methods evaluated in this study. Temporary flow restoration through stent deployment may affect the dangerous distal clot migration.

Remote Surgery Using a Neuroendovascular Intervention Support Robot Equipped with a Sensing Function: Experimental Verification.

PURPOSE: Expectations for remote surgery in endovascular treatments are increasing. We conducted the world's first remote catheter surgery experiment using an endovascular treatment-supported robot. We considered the results, examined the issues, and suggested countermeasures for practical use. METHODS: The slave robot in the angiography room is an original machine that enables sensing feedback by using an originally developed insertion force-measuring device, which detects the pressure stress on the vessel wall and alerts the operator using an audible scale. The master side was set in a separate room. They were connected via HTTP communication using local area network system. The surgeon operated by looking at a personal computer monitor that shared an angiography monitor. The slave robot catheterized and inserted a coil for an aneurysm in the silicon blood vessel model in the angiography room. RESULTS: Our robot responded to the surgeon's operations promptly and to the joystick's swift movements quite accurately. The surgeon could control the stress to the model vessels using various actions, because the operator could hear the sound from the insertion force. However, the robot required a time gradient to reach a stable advanced speed at the time of the initial movement, and experienced a slight time lag. CONCLUSION: Our remote operation appeared to be sufficiently feasible to perform the surgery safely. This system seems extremely promising for preventing viral infection and radiation exposure to medical staff. It will also enable medical professionals to operate in remote areas and create a ubiquitous medical environment.

Local Balloon-Assisted Navigation of a Microcatheter into an Aneurysm during Intracranial Aneurysmal Coiling: A Dunk Shot Technique.

OBJECTIVES: Various endovascular approaches have been reported for patients with intracranial aneurysms. However, the safety of navigating a microcatheter into the aneurysm remains debatable. In this study, we evaluated a novel method "dunk shot technique," in which a proximal balloon and a local balloon are used for navigation of a microcatheter into an aneurysm under challenging situations. MATERIALS AND METHODS: We have reported two cases of unruptured internal carotid artery-superior hypothalamic artery aneurysm. An 8-F balloon-attached catheter was used as the guiding catheter. A local balloon catheter for neck remodeling and a microcatheter for coil insertion were navigated around the aneurysmal neck region. When it seemed difficult to navigate a microcatheter into an aneurysm, both the guiding balloon and a local balloon catheter were used for assistance. After inflation of the guiding balloon, the local balloon was inflated partially to negotiate the tip of the microcatheter. RESULTS: The uncontrollable tip of the microcatheter could be intentionally moved by the local balloon. CONCLUSIONS: We evaluated the effectiveness of the balloon-assisted technique for the navigation of a microcatheter in cases with challenging anatomy. A little bit of direct effect to the tip of the microcatheter by a local balloon could produce effective outcomes under the proximal flow arrest.

Unruptured Paraclinoid Carotid Aneurysms Occur More Frequently in Younger Ages.

PURPOSE: We investigated the age distribution of cerebral saccular aneurysms in various locations to clarify the differences by location and discuss the mechanism of formation. MATERIALS AND METHODS: We retrospectively assessed clinical material obtained from 1,252 unruptured aneurysms treated with endovascular embolization between 2004 and 2019. Age, sex, laterality, and size were investigated by the location of aneurysms, classified as cavernous internal carotid artery (ICA), paraclinoid ICA, supraclinoid ICA, anterior communicating artery, anterior cerebral artery, middle cerebral artery, basilar artery complex, and posterior inferior cerebellar artery. Paraclinoid aneurysms were subclassified into 3 patterns according to their projecting direction: S-type, with superior protrusion; M-type, with medial protrusion; and P-type, with posteroinferior protrusion. RESULTS: There was no significant difference by location for sex, laterality, and size. The mean age of patients with paraclinoid aneurysms (56.5 years old) was significantly lower than that of other aneurysm patients (64.3 years old). Notably, 40% of the patients with M-type aneurysms were <50 years old. This percentage was significantly higher than that of aneurysms at other locations (P<0.05). CONCLUSION: We found a young female predominance for patients with paraclinoid carotid aneurysms. This study may suggest that congenital factors contribute to paraclinoid aneurysm formation as well acquired factors, such as hemodynamic stress, atherosclerotic wall damage, and local inflammation.

Pull the Trigger Sign: A Novel Method to Identify the Clot Position during Acute Endovascular Thrombectomy.

Objective: Accurately determining the clot position is highly important for immediate recanalization when endovascular mechanical thrombectomy is performed using a stent retriever and aspiration catheter. We describe a new method that facilitates the precise identification of the clot position called pull the trigger sign (PTS). Case Presentation: Selective angiography was performed through a 0.027-inch microcatheter that penetrated the clot into the distal lumen. Although the contrast media highlighted the occluded artery, it often stagnated in the distal artery. It was washed away at a certain point when a stent clot retriever was deployed over the potential clot site. We hypothesized that this point represented the exact position of the clot's proximal end and used in vitro analyses to assess this hypothesis. Briefly, a circulation-enabled silicone vascular model in which colored water was used to simulate stagnation beyond a fake clot was developed and utilized to investigate PTS six times. The rate of identifying PTS in the vascular model was 100%. As hypothesized, stagnant fluid was washed away when the deployed stent reached the clot's proximal position. The clinical efficacy of PTS was also confirmed. Conclusion: PTS was useful in revealing the precise position of clot's proximal end, which enabled safer contact aspiration when using an aspiration catheter. Thus, PTS led to a higher success rate and faster recanalization in the first attempt than conventional methods.

A Method to Evaluate Vessel Deviation during Withdrawal of a Stent Retriever Using a Silicon Vascular Model.

Objective: Catastrophic complications may develop because of vessel deviation during device delivery into intracranial vessels for neurointerventions. We report a novel method using a silicon model capable of evaluating vessel deviation as a numerical value. Methods: In all, 10 tiny markers, each with a pitch of approximately 5 mm, were attached to the vessel model along the long axis. We used a high-resolution camera to record movies of the deviation of the vessel model while employing different stent retrievers. The movies were reviewed to determine the maximum deviation of each marker on the vessel model. Results: As expected, stent retrievers of the same type exhibited more vessel shifts when they had a larger diameter and longer length. On the other hand, stents with a segmental structure demonstrated less vessel deviation than those with a tubular structure, regardless of the large lumen and long length. Conclusion: If the degree of vessel stress can be represented by a numerical value, areas where the careful use of different devices for neurointerventions is required may be able to be identified. Moreover, this method may be useful for training.

A Novel Technique for Mitigation of the Ledge Effect Caused by the Use of a Large-Lumen Catheter during Neurointervention: Beanstalk Method.

Navigating a large-caliber catheter into the intracranial artery may generate a "ledge effect," which disturbs successful neurointervention. Particularly, navigation of a large-lumen aspiration catheter is often required to achieve fast recanalization in acute ischemic stroke cases. Occasionally, the aspirator cannot be passed through the ophthalmic artery origin because of the ledge effect. Here, we report a new technique for mitigation of the ledge effect that involves the use of double micro-guidewires (MGWs). We refer to this technique as the "beanstalk method." We evaluated the efficacy of our idea using a silicon vascular model. Two 0.014" MGWs are used for navigation of a 0.068" aspirator. After one guidewire is navigated to the distal portion, another MGW is advanced along with the former guidewire, in a spiral fashion, similar to the growth of a beanstalk. The aspirator can then pass with the coaxial double-guidewire, although there is a severe gap in the vessel. We performed an in vitro study to demonstrate the effectiveness of the beanstalk method. The beanstalk method was very useful, even under challenging conditions that did not allow for passage of a conventional coaxial catheter or buddy-wire. The beanstalk method effectively decreases the ledge effect because of the shape of the two wires just ahead of the catheter, which contrasts with the hardness of the spiral wires. In cases involving challenging vasculature, the beanstalk method achieves smoother catheter navigation than the conventional coaxial method or buddy-wire technique.

Cholesterol Embolization Syndrome After Carotid Artery Stenting Associated with Delayed Cerebral Hyperperfusion Intracerebral Hemorrhage.

BACKGROUND: The cholesterol embolization syndrome (CES) results from the distal embolization of cholesterol crystals from atheromatous plaques in large vessels such as the aorta and results in multiorgan damage. CASE DESCRIPTION: We present the case of a patient with definite CES with skin manifestations (e.g., blue toes) and renal and neurological dysfunction, including parenchymal hematoma with cytotoxic and vasogenic edema after he had undergone left carotid artery stenting for symptomatic critical left carotid artery stenosis. CONCLUSIONS: Our patient with CES had cutaneous involvement affecting the lower limbs and renal and neurological involvement. High clinical suspicion and early treatment can reduce the mortality and morbidity after endovascular procedures. The neurological symptoms had most likely resulted from delayed cerebral hyperperfusion syndrome resulting in intracerebral hemorrhage.

Initial Clinical Experience of Using a Newly Designed Preshaped Microguidewire in Acute Endovascular Thrombectomy.

Mechanical thrombectomy has been widely used for the treatment of acute ischemic stroke. During this procedure, operators must navigate the microcatheter with a microguidewire (MGW) into vessels that cannot be visualized on fluoroscopy as rapidly as possible. In this study, we developed a modified pigtail-shaped MGW (MPMGW) for security and controllability. Moreover, the efficacy of the MPMGW for the treatment of acute ischemic stroke was assessed. The MPMGW was designed using 0.014 MGW. Because we created four MPMGWs during a clinical evaluation before the launch in the market, these wires were used in four consecutive patients with acute ischemic stroke in the single institution. The occluded arteries were the basilar artery (n = 1), middle cerebral arteries (M1 and M2, n = 2), and internal carotid artery (n = 1). All four procedures were conducted without any complications. The procedures included navigating the MGW and passing it through the clot. Complete recanalization was achieved in all cases. The average time between femoral artery puncture and recanalization was 15 min. The use of the preshaped MPMGW in acute thrombectomy was effective in terms of both security of procedure and reduction in recanalization time.

Novel Technique for Detection of Actual Position of Clot During Endovascular Clot Retrieval: Assessment of Microcatheter Withdrawing Angiography.

BACKGROUND: When endovascular clot retrievals are performed using a stent retriever and/or an aspiration catheter, identifying the accurate position of a clot is extremely important for a successful immediate recanalization. Herein, we report a new technique called microcatheter withdrawing angiography, which facilitates the identification of the precise position of a clot. The negative shadow appearance of the clot on angiography was referred to as the actual crab claw sign. METHODS: When a 0.027-inch microcatheter penetrated the clot after inserting a 0.014-inch microwire, selective angiography was conducted using the microcatheter. Simultaneously, the microcatheter was slowly withdrawn with continuous contrast media injection, while the microwire was kept in the distal vessel. The precise position of the clot was found, which was referred to as the actual crab claw sign. Next, we conducted in vitro and in vivo analyses. RESULTS: The actual crab claw sign could be identified in the vascular model and in actual clinical settings. Therefore the sweet spot of the stent retriever could be set over the clot, and an accurate contact aspiration could be performed using an aspirator. CONCLUSIONS: Microcatheter withdrawing angiography can help identify the actual crab claw sign. This technique has a higher success rate and faster recanalization than conventional strategy, particularly in challenging cases of unsuccessful recanalization during the first attempt.