Objective: There has been no detailed study reporting the relationship between flow restoration (FR)/re-occlusion status and recanalization results during the acute thrombectomy using stent retrievers. In this study, we examined the influence of FR/re-occlusion during stent deployment on recanalization in our experiences.

Subjects and Methods: In all, 24 patients with cardiogenic cerebral embolism underwent thrombectomy with a TREVO stent retriever (10 males, 14 females, mean age: 77.2 years). Intravenous tissue plasminogen activator (t-PA) infusion was preceded in 17 of 24 patients, occlusion sites were as follows: internal carotid artery, 9 patients; M1 of middle cerebral artery, 13 patients; and basilar artery, 2 patients. We investigated the relationship between the presence or absence of FR/re-occlusion and grade of recanalization thrombolysis in cerebral infarction (TICI). We also examined the interval from FR until re-occlusion and frequency of stent deployment.

Results: In the first session of stent deployment, FR and subsequent re-occlusion were observed in 11 patients (11/24, 46%). Of these, TICI 2b or higher grade recanalization was achieved in nine patients (9/11, 81%). Of 10 patients who had FR but no re-occlusion in the first session of stent deployment (10/24, 42%), TICI 2b or higher scale recanalization was achieved in 4 (4/10, 40%). In three patients without FR (3/24, 13%), TICI 2b or higher scale recanalization was not achieved. Of the above 11 patients who showed FR and subsequent re-occlusion in the first session of stent deployment, the waiting time until re-occlusion was 5 minutes in seven patients and 10 minutes in four patients. Of the 10 patients who had FR but no re-occlusion, the waiting time was 5 minutes in four patients, 10 minutes in four patients, and 20 minutes in two patients. In 9 of the 24 patients, several sessions of stent deployment were required, and the total frequency of stent deployment was 37 times. In 37 sessions of stent deployment showed the achievement of FR and re-occlusion in 17 sessions (17/37, 46%). Of these, TICI 2b or higher scale recanalization was achieved in 14 (14/17, 82%). Of 12 sessions with FR but no re-occlusion (12/37, 32%), TICI 2b or higher scale recanalization was achieved in 5 (5/12, 41%). TICI 2b or higher scale recanalization was not achieved in eight sessions without FR (8/37, 22%).

Conclusion: Flow restoration immediately after stent deployment was a necessary condition for recanalization. If re-occlusion is confirmed after FR, satisfactory recanalization may be achieved at a high percentage. The results demonstrated that satisfactory recanalization was not achieved without FR, and less likely without re-occlusion following FR.

Objective: The hemodynamics of cerebral aneurysms was evaluated by computational fluid dynamics (CFD) analysis using the non-Newtonian (Casson’s) fluid model and the Newtonian fluid model obtained from measurements. The two fluid models were examined to clarify the influence of blood viscosity on hemodynamic parameters.

Methods: We measured blood viscosity of blood obtained from 50 healthy adults at 12 shear rate ranges using a compact-sized falling needle rheometer. Blood viscosity was set as the Newtonian and Casson’s fluid models determined using these measurements. In all, 12 cerebral aneurysms were evaluated by transient analysis to calculate the wall shear stress (WSS), wall shear stress gradient (WSSG), flow velocity (FV), oscillatory shear index (OSI), and parameters that facilitate the quantitative assessment of the fluctuations of individual vectors, including the gradient oscillatory number (GON) and oscillatory velocity index (OVI). Bland–Altman analysis was performed to compare the two models, and systematic errors were examined.

Results: The relationship between the apparent viscosity and the shear rate obtained from blood samples of 50 healthy adults revealed the characteristics of Casson’s fluid. The systematic errors in hemodynamic parameters for the two fluid models were small, and the correlation coefficients of the WSS, WSSG, FV, OSI, GON, and OVI were 0.9999, 0.9999, 0.9985, 0.9734, 0.9758, and 0.9258, respectively. Furthermore, the means of these hemodynamic parameters for the entire aneurysm showed a high consistency rate between the two groups, whereas different values were observed in focal hemodynamics including blebs.

Conclusion: Newtonian fluid numerical modeling may be useful for analyzing the entire aneurysm. On the other hand, these results indicated that hemodynamics analyzed using non-Newtonian blood viscosity could have certain effects on focal hemodynamics that may be related to aneurysm growth and rupture.

Objective: We report a patient who underwent thrombectomy for acute bilateral internal carotid artery occlusion (ICAO).

Case Presentation: A 76-year-old female presented consciousness disturbance. Although warfarin had been administered after prosthetic replacement, it was discontinued due to gastrointestinal hemorrhage. MRI showed bilateral ICAO and right-dominant ischemic changes involving the bilateral hemispheres. Radiological findings indicated acute occlusion of the right internal carotid artery (ICA), and chronic occlusion of the left ICA was primarily considered; however, revascularization was conducted with considering the possibility of bilateral occlusion. Thrombectomy was performed and recanalization of the bilateral ICAs was achieved. However, ischemia progressed, leading to extensive cerebral infarction.

Conclusion: Thrombectomy for bilateral ICAO was performed although the outcome was unfavorable. Acute bilateral ICAO contains poor prognosis although it is indispensable to appropriately diagnose, evaluate, and select therapeutic strategy. A proper management for bilateral ICAO awaits further investigation.

Objective: We report a patient with allergy to iodinated contrast medium for whom a working angle was prepared based on preoperative CTA data, and coil embolization was performed using gadolinium (Gd) contrast medium at minimum.

Case Presentation: The patient was a 44-year-old female. For detailed examination of an unruptured cerebral aneurysm, contrast-enhanced CT was performed, leading to a diagnosis of an unruptured cerebral aneurysm, measuring 7 mm in maximum diameter, beside the left internal carotid artery. At this point, serious allergic symptoms were observed. Based on the CT data, we prepared a fluoroscopic image of the skull at a working angle on endovascular treatment. Under general anesthesia, body movement was restricted, and angiography with Gd contrast medium was performed by identifying the same angle of fluoroscopy as that on the above fluoroscopic image. Subsequently, coil embolization of the aneurysm was conducted using this image as a road map. Treatment was completed without complications. The volume of Gd contrast medium infused into the artery was 10 mL.

Conclusion: The treatment of an unruptured cerebral aneurysm with a small volume of Gd contrast medium could be performed by adapting image processing from the preoperative CT data to fluoroscopy at the time of treatment.

Objective: We report a case of spinal cord infarction that developed after successful coil embolization of a recurrent basilar bifurcation aneurysm. This complication has been rarely reported in the literature, but may cause severe sequelae following the endovascular embolization.

Case Presentation: During a follow-up examination 6 years after balloon-assisted coil embolization by bilateral vertebral artery (VA) approach to treat an unruptured basilar bifurcation aneurysm, recanalization was noted in a 78-year-old patient. There had been no complications after the original surgery and the postoperative course was uneventful. We planned retreatment by stent-assisted coil embolization via the left VA approach. Immediately after the surgery was successfully completed, severe left-sided hemiparesis appeared, but there were no discernible intracranial ischemic lesions causing the symptom. Cervical MRI revealed an infarction on the left side of the cervical spinal cord between the first and fourth cervical vertebrae. At 6 months’ follow-up, she was able to walk with minimal assistance.

Conclusions: The spinal cord infarction seemed to have been caused by wedging of the guiding catheter, which had not occurred during initial treatment. When performing endovascular treatment for posterior circulation disease, wedging of the guiding catheter should be avoided.

Purpose: When intending balloon-/stent-assisted embolization of cerebral aneurysms using ≥8 Fr guiding and coaxial 6 Fr inner catheters, operations can be conducted more safely by inserting the inner catheter to a site proximal to the aneurysm. However, tortuous-blood-vessel-related mechanical vasospasm or blood stagnation makes it impossible to insert a 6 Fr inner catheter to a distal site in some patients. For adjunctive techniques, devices may interfere with each other in a 6 Fr inner catheter, reducing the operability.

Case Presentation: In this study, we termed a method of placing two 4.2 Fr FUBUKI catheters (Asahi Intecc Co., Ltd, Aichi, Japan) in parallel in an 8 Fr shuttle sheath (SS) to reduce the resistance to a parent blood vessel and improve the operability during an adjunctive technique, “dual inner catheter technique (DICT)”, and selected the DICT for 10 patients with unruptured cerebral aneurysms.

Conclusion: The DICT reduced the distance from the aneurysm, device-related interference, and risk of blood stagnation/mechanical vasospasm, improving the operability/safety.

Purpose: We report three patients with wide-necked cerebral aneurysms in whom the T-stent technique with a low-profile visualized intraluminal support (LVIS) Jr. was useful, and review its usefulness and tips.

Case Presentations: Case 1: A 75-year-old male with a left internal carotid-posterior communicating (IC-PC) aneurysm (maximum diameter: 11 mm, neck diameter: 7.0 mm). The posterior communicating (P-com; 2.3 mm) had branched from the aneurysmal dome. Stent-assisted coil embolization (SACE) was performed by inserting an LVIS Jr. 3.5 × 28 on the fetal-type posterior cerebral artery (PCA). P-com side and an LVIS Jr. 3.5 × 18 on the internal carotid artery (ICA) side (T-stent technique).

Case 2: An 80-year-old female with a right IC-PC aneurysm (maximum diameter: 6.0 mm, neck diameter: 5.4 mm). The P-com (2.2 mm) had branched from the aneurysmal dome. SACE was performed by inserting an LVIS Jr. 2.5 × 13 on the fetal-type PCA. P-com side and a Neuroform Atlas 4.5 × 21 on the ICA side.

Case 3: A 61-year-old female with a left vertebral artery (VA)-posterior inferior cerebellar artery (PICA) aneurysm (maximum diameter: 6.4 mm, neck diameter: 5.6 mm, PICA diameter: 2.2 mm). SACE was performed by inserting an LVIS Jr. 2.5 × 13 on the PICA side and an LVIS Blue 4.5 × 23 on the VA side.

Conclusion: The T-stent technique with an LVIS Jr. was useful for achieving neck formation for a wide-necked aneurysm directly branching from an aneurysm or preserving branches measuring ≥2 mm in diameter. We reported its tips.

Objective: We could cure two cases of arteriovenous fistula (AVF) of the scalp by the pressure cooker technique (PCT).

Case Presentations: Case 1 showed scalp AVF with a direct arteriovenous (AV) shunt between the left posterior auricular artery (PAA) and the left superficial temporal vein (STV), which was also fed by a branch of the left occipital artery (OA). Case 2 showed scalp AVF with a direct AV shunt between the left occipital vein (OV) connected to the left STV and the left OA and left PAA as the collateral feeders. The shunts could be completely occluded by forming a plug using coils and low-concentration n-butyl-2-cyanoacrylat (NBCA) and injecting Onyx with pressure through a non-detachable microcatheter (MC) by the PCT via the left PAA in Case 1 and via the left OA in Case 2. The MC could be removed in both patients.

Conclusion: This technique may be useful if it is applied only to the external carotid artery system, in which adhesion of the MC is manageable, and Onyx injection finishes within a several minutes.