Endovascular Treatment for Ruptured Proximal Anterior Cerebral Artery Dissecting Aneurysm: A Case Series.

Subarachnoid hemorrhage due to the A1 segment of an anterior cerebral artery dissecting aneurysm is rare. Therefore, a standard treatment has not been established. Though several case reports of direct surgery exist, there are few reports on endovascular treatment. This is the first study to describe five patients who underwent endovascular treatment for ruptured A1 dissecting aneurysms. Between January 2001 and December 2022 in our affiliated centers, five cases of SAH-onset A1 dissecting aneurysms were treated with endovascular treatment. We describe in detail two representative cases, briefly summarize the other three, and analyze their complications and outcomes. In the five cases, four were female. Four were in their 50s, and one was in her 80s. The WFNS grades were as follows: three were 2, one was 4, and one was 5. No re-ruptures or symptomatic complications were observed. The modified Rankin Scale scores at the time of discharge were as follows; one was 0, one was 1, two were 2, and one was 5. One in five patients needed retreatment after endovascular trapping because of recanalization. Endovascular treatment may be an effective and viable treatment option for ruptured A1 dissecting aneurysms. Further studies are needed to collect detailed data on complications and outcomes.

Contact aspiration for basilar artery occlusion safely reduces the puncture-to-recanalization time.

OBJECTIVE: Effective thrombectomies in the posterior circulation remain controversial. Previous reports have demonstrated the superiority of contact aspiration in anterior circulation. Aspiration catheters and stent retrievers are often used alone on a global scale, while combined techniques are commonly used in Japan. This study evaluated the effect of first-line contact aspiration with other strategies for the treatment of basilar artery occlusion. METHODS: The primary outcome was the frequency of the first-pass effect, and the secondary outcome was the time from puncture to the first-pass effect. A multicenter observational registry including 16 Japanese stroke centers was used. Between December 2013 and February 2021, enrolled patients underwent endovascular thrombectomy for basilar artery occlusion. The efficacy of contact aspiration compared to other methods (including stent retrievers and combined techniques) was evaluated. RESULTS: Eighty-four patients were included, all of whom had achieved effective recanalization. Twenty-six patients were treated with contact aspiration, 13 with combined technique, and 45 with stent retrievers. The two groups: contact aspiration and non-contact aspiration, had different backgrounds. Both had similar frequencies of effective recanalization and first-pass effects. The contact aspiration group experienced better functional outcomes without statistical significance, while this strategy was significantly associated with a shorter puncture-to-recanalization time (38 vs. 55 minutes, P=0.036). In particular, in the 55 patients with the first-pass effect, multivariate Cox proportional hazard analysis showed that contact aspiration was significantly associated with a shorter time from puncture to first-pass effect, independent of age and etiology of large-artery atherosclerosis (hazard ratio 2.02, 95% confidence intervals 1.10-3.69, P=0.023). CONCLUSION: This study suggested that contact aspiration for basilar artery occlusion may shorten the puncture-to-first-pass effect, compared to stent retrievers and combined techniques.

Two-Step Effective Onyx Embolization from the Occipital Artery for the Treatment of Intracranial Dural Arteriovenous Fistula: A Technical Note.

AIM: To report our experience and the technique of two-step effective Onyx embolization from occipital artery (OA) for the obliteration of dural arteriovenous fistulas (DAVFs) with OA feeders. MATERIAL AND METHODS: The medical records of patients with intracranial DAVFs treated with trans-arterial embolization (TAE) using Onyx from the OA were retrospectively reviewed. RESULTS: Seven patients were included. The methods of Onyx injection from the OA were categorized as simple Onyx injection into the shunt, and two-step embolization. Two-step embolization involved the Onyx or coil embolization of the OA distal to the branching site of the feeders in the first step, and Onyx was injected toward the target shunt in the second step. Simple Onyx injection was performed in two cases; in both cases, the residual shunt remained. By contrast, the two-step embolization technique was performed in five cases, and in all those cases, sufficient embolization of the DAVFs was achieved. CONCLUSION: Prior embolization using Onyx or coil of the distal OA helped prevent Onyx from unexpected embolization through the subcutaneous branches that were not associated with the shunt, thereby leading to effective embolization. This new two-step embolization technique from the OA may improve the obliteration rate of DAVFs with OA feeders using TAE with Onyx.

Successful Retrieval of Filter Embolic Protection Device Fragment Trapped by a Carotid Stent: A Case Report.

Objective: Embolic protection devices are useful for preventing distal embolism during carotid artery stenting (CAS); however, complications have been reported. The successful removal of a filter fragment trapped at the distal edge of a carotid stent during the retrieval procedure is described. Case Presentation: CAS was performed for internal carotid artery stenosis in a patient in his 70s, and the carotid stent was successfully placed. During the retrieval procedure, the tip of the filter was trapped at the distal edge of the stent and detached from the filter. Using a snare kit, the filter tip was successfully retrieved, and no postoperative neurological symptoms occurred. Conclusion: The edge of a carotid stent can potentially trap devices. When trapping or fragmentation of a device is suspected, it is necessary to evaluate the situation and cause, and the device should be appropriately retrieved without using force.

Delayed hydrocephalus and visual field defect due to perianeurysmal inflammation after treating a large unruptured aneurysm with flow diverter and coil: A case report.

Flow diverter (FD) placement is increasingly used to treat large supraclinoid aneurysms. Here, we report a case of hydrocephalus following FD placement. One patient in her 60 s underwent FD placement combined with coil embolization. Within 1 month, the patient started to show visual field defects and symptoms of hydrocephalus, which worsened within another month. We report that hydrocephalus developed acutely, without high protein levels in the cerebrospinal fluid, and as a complication using a Surpass Streamline. Although the precise mechanisms are unclear, our report suggests a different mechanism for the development of hydrocephalus after FD placement combined with coil embolization.

Impact of cancer history on long-term outcome after elective neuro-endovascular treatment in patients aged 80 years or older: A retrospective multicenter observational study.

AIM: Assessing the indication for elective neuro-endovascular treatment (EVT) in older patients requires consideration of the impact of systemic comorbidities on their overall reduced life expectancy. The objective of this study was to determine the long-term outcomes of elective neuro-EVT in patients aged ≥80 years, and to investigate the impact of pre-existing cancer on their long-term outcomes. METHODS: Of the patients enrolled in multicenter observational registry, those aged ≥80 years undergoing elective neuro-EVT between 2011 and 2020 were enrolled. A history of cancer was defined as a pre-existing solid or hematologic malignancy at the time of EVT. The primary outcome was time to death from elective neuro-EVT. RESULTS: Of the 6183 neuro-EVT cases implemented at 10 stroke centers, a total of 289 patients (median age, 82 years [interquartile range 81-84 years]) were analyzed. A total of 58 (20.1%) patients had a history of cancer. A total of 78 patients (27.0%) died during follow up. The 5-year survival rate of enrolled patients was 64.6%. Compared with patients without a history of cancer, those with a history of cancer showed significantly worse survival (log-rank test, P = 0.001). Multivariate Cox proportional hazards analysis showed history of cancer was an independent predictor of time to death from elective neuro-EVT (HR 1.74, 95% CI 1.01-3.00, P = 0.047). Cancer was the leading cause of death, accounting for 25.6% of all deaths. CONCLUSIONS: The present study showed that history of cancer has a significant impact on time to death from elective neuro-EVT in patients aged ≥80 years. Geriatr Gerontol Int 2024; 24: 211-217.

Cerebral Small Vessel Disease Burden for Bleeding Risk during Antithrombotic Therapy: Bleeding with Antithrombotic Therapy 2 Study.

OBJECTIVE: This study was undertaken to determine the excess risk of antithrombotic-related bleeding due to cerebral small vessel disease (SVD) burden. METHODS: In this observational, prospective cohort study, patients with cerebrovascular or cardiovascular diseases taking oral antithrombotic agents were enrolled from 52 hospitals across Japan between 2016 and 2019. Baseline multimodal magnetic resonance imaging acquired under prespecified conditions was assessed by a central diagnostic radiology committee to calculate total SVD score. The primary outcome was major bleeding. Secondary outcomes included bleeding at each site and ischemic events. RESULTS: Of the analyzed 5,250 patients (1,736 women; median age = 73 years, 9,933 patient-years of follow-up), antiplatelets and anticoagulants were administered at baseline in 3,948 and 1,565, respectively. Median SVD score was 2 (interquartile range = 1-3). Incidence rate of major bleeding was 0.39 (per 100 patinet-years) in score 0, 0.56 in score 1, 0.91 in score 2, 1.35 in score 3, and 2.24 in score 4 (adjusted hazard ratio [aHR] for score 4 vs 0 = 5.47, 95% confidence interval [CI] = 2.26-13.23), that of intracranial hemorrhage was 0.11, 0.33, 0.58, 0.99, and 1.06, respectively (aHR = 9.29, 95% CI = 1.99-43.35), and that of ischemic event was 1.82, 2.27, 3.04, 3.91, and 4.07, respectively (aHR = 1.76, 95% CI = 1.08-2.86). In addition, extracranial major bleeding (aHR = 3.43, 95% CI = 1.13-10.38) and gastrointestinal bleeding (aHR = 2.54, 95% CI = 1.02-6.35) significantly increased in SVD score 4 compared to score 0. INTERPRETATION: Total SVD score was predictive for intracranial hemorrhage and probably for extracranial bleeding, suggesting the broader clinical relevance of cerebral SVD as a marker for safe implementation of antithrombotic therapy. ANN NEUROL 2024;95:774-787.

eQTL mapping in fetal-like pancreatic progenitor cells reveals early developmental insights into diabetes risk.

The impact of genetic regulatory variation active in early pancreatic development on adult pancreatic disease and traits is not well understood. Here, we generate a panel of 107 fetal-like iPSC-derived pancreatic progenitor cells (iPSC-PPCs) from whole genome-sequenced individuals and identify 4065 genes and 4016 isoforms whose expression and/or alternative splicing are affected by regulatory variation. We integrate eQTLs identified in adult islets and whole pancreas samples, which reveal 1805 eQTL associations that are unique to the fetal-like iPSC-PPCs and 1043 eQTLs that exhibit regulatory plasticity across the fetal-like and adult pancreas tissues. Colocalization with GWAS risk loci for pancreatic diseases and traits show that some putative causal regulatory variants are active only in the fetal-like iPSC-PPCs and likely influence disease by modulating expression of disease-associated genes in early development, while others with regulatory plasticity likely exert their effects in both the fetal and adult pancreas by modulating expression of different disease genes in the two developmental stages.

Ghost twisting of the dual-layer flow-diverting stent.

The twisting phenomenon of the flow diverter stents rarely occurs, but it recently became relatively well-recognized. There have been few reports on single-layer flow diverters only. The Flow Redirection Endoluminal Device (FRED) (MicroVention, Tustin, California) has a unique design characterized by a braided dual-layer self-expanding stent. There have been no reports on the twisting phenomenon of FRED. This study reports two cases of acute in-stent blood flow disturbances after the deployment of FRED in a patient with intracranial aneurysms associated with "ghost twisting." In this phenomenon, the inner layer does not expand with the coning deformation, even though the outer layer is fully open. This was confirmed through high-resolution cone-beam computed tomography, but not conventional angiography. The two cases were successfully treated using balloon angioplasty and showed favorable outcomes. The structural issue of "ghost twisting" was a possible underlying factor for the ischemic complications associated with FRED deployment.

Imaging predictors of clinical outcomes after endovascular treatment in MRI-selected patients with acute basilar artery occlusion.

PURPOSE: We aimed to investigate the impact of baseline infarct area and collateral status (CS), which are imaging predictors of clinical outcome following stroke, after endovascular treatment (EVT) in MRI-selected patients with acute basilar artery occlusion (BAO). METHODS: Patients with acute BAO who underwent EVT within 24 h after stroke from December 2013 to February 2021 were included in this retrospective, multicenter, observational study. The baseline infarct area was evaluated by the posterior circulation of Acute Stroke Prognosis Early Computed Tomography Score (pc-ASPECTS) using diffuse-weighted imaging (DWI), and CS was assessed by measuring the computed tomography angiography of the basilar artery (BATMAN) score and the posterior circulation collateral score (PC-CS) using magnetic resonance angiography (MRA). A Good outcome was defined as a modified Rankin scale score ≤ 3 at 3 months. For each imaging predictor, a multivariate logistic regression analysis was performed to evaluate its impact on good outcomes. RESULTS: A total of 86 patients were analyzed, and 37 (43.0%) had a good outcome. The latter showed significantly higher pc-ASPECTS than those without good outcomes. In multivariate analyses, a pc-ASPECTS ≥ 7 was significantly associated with good outcomes (OR, 2.98 [95% CI, 1.10-8.13], P = 0.032), while PC-CS ≥ 4 (OR, 2.49 [95% CI, 0.92-6.74], P = 0.073) and BATMAN score ≥ 5 (OR, 1.51 [95% CI, 0.58-3.98], P = 0.401) were not. CONCLUSIONS: In MRI-selected patients with acute BAO, pc-ASPECTS on DWI was an independent predictor of clinical outcomes after EVT, while the MRA-based CS assessments were not.

Influence of Bilateral Cerebellar Infarction on Functional Outcome After Endovascular Treatment for Basilar Artery Occlusion.

BACKGROUND AND PURPOSE: To measure the magnitude of the effect of the infarct location measured using the posterior circulation Alberta Stroke Program Early Computed Tomographic Score (pc-ASPECTS) on the functional outcome at 90 days in patients with basilar artery (BA) occlusion undergoing endovascular therapy (EVT). METHODS: Of the acute ischemic stroke patients undergoing EVT for acute posterior circulation large vessel occlusion enrolled in the multicenter observational registry from December 2013 to February 2021, patients with BA occlusion were included. A favorable outcome was defined as achieving a modified Rankin Scale score of 0-3 at 90 days. The effect of pc-ASPECTS including the distribution on favorable outcomes was evaluated. RESULTS: One hundred patients were analyzed. Fifty-one patients (51%) achieved favorable outcome. Patients achieving a favorable outcome were younger, had a lower National Institutes of Health Stroke Scale score before EVT, and had a higher pc-ASPECTS before EVT than those not achieving a favorable outcome. Multivariable logistic analysis showed a significant association between higher pc-ASPECTS and a favorable outcome (odds ratio [OR] 1.24; 95% confidence interval [CI] 1.02-1.52; P = 0.028). Considering the infarct location, bilateral cerebellar infarction was significantly associated with a lower frequency of favorable outcomes than those without cerebellar infarction (OR 0.16; 95% CI 0.04-0.51; P = 0.002). CONCLUSIONS: A higher pc-ASPECTS before EVT could be a predictor of a favorable outcome after EVT for BA occlusion. In particular, the presence of bilateral cerebellar infarction before EVT was significantly associated with a lower likelihood of a favorable outcome.

A Case of Dural Arteriovenous Fistula Following Cerebral Venous Sinus Thrombosis Associated with the COVID-19 Vaccine.

Objective: Cerebral venous sinus thrombosis (CVST) is one of the rare and severe complications of coronavirus disease 2019 (COVID-19) vaccines. CVST has also been reported to develop into dural arteriovenous fistula; however, there were no reports of dural arteriovenous fistula associated with COVID-19 vaccine-induced cerebral venous sinus thrombosis. Here, we describe a rare case of a transverse-sigmoid sinus dural arteriovenous fistula followed by CVST due to COVID-19 vaccination. Case Presentation: A 70-year-old patient presented with headache five days after receiving a second dose of COVID-19 vaccine. MRI showed a CVST in the superior sagittal sinus, left transverse sinus, and left sigmoid sinus. His headache improved after the administration of anticoagulant therapy. Six months later, a similar headache recurred, and cerebral angiography demonstrated a dural arteriovenous fistula in the left transverse sigmoid sinus and convexity dural arteriovenous fistulas in the left parietal cortex. The patient was treated twice with two sessions of transarterial embolization, and the shunts were completely occluded. His symptoms improved, and he was discharged with a modified Rankin Scale score of 0. Conclusion: Dural arteriovenous fistula can develop after CVST in association with COVID-19 vaccination.

P2Y12 reaction units and ischemic and bleeding events after neuro-endovascular treatment.

BACKGROUND AND PURPOSE: To investigate the associations of perioperative P2Y12 reaction units (PRU) measured using VerifyNow with ischemic and bleeding events, and to determine the PRU threshold in the setting of elective neuro-endovascular treatment (EVT) for intracranial/extracranial vascular disease in patients taking aspirin and clopidogrel. METHODS: Of the patients undergoing elective neuro-EVT while taking aspirin and clopidogrel, those taking both antiplatelet agents for 7 days or more and whose PRU and aspirin reaction units (ARU) were measured were included. The primary and safety outcomes were defined as symptomatic ischemic and major bleeding events within 30 days after EVT. RESULTS: A total of 197 patients were available for the analyses. Higher PRU was associated with symptomatic ischemic events on multivariable logistic analysis (odds ratio per 10 increase 1.14 [95% confidence interval 1.03-1.27], p=0.011). Receiver operating characteristic curve analysis showed that PRU ≥212 was the threshold to predict symptomatic ischemic events (area under the curve=0.73; sensitivity, 62.5%; specificity, 82.0%). Lower PRU was also associated with major bleeding events (odds ratio per 10 increase 0.87 [0.78-0.96], p=0.004), and the threshold to predict major bleeding events was PRU ≤46 (area under the curve=0.76; sensitivity, 70.0%; specificity, 87.2%) CONCLUSIONS: The PRU value was associated with symptomatic ischemic and major bleeding events after elective neuro-EVT in patients taking aspirin and clopidogrel. PRU ≥212 and PRU ≤46 appeared to be the threshold values to predict symptomatic ischemic and major bleeding events, respectively.

Endovascular Treatment for Acute Ischemic Stroke After Video-Assisted Thoracoscopic Pulmonary Lobectomy in Patients With Lung Cancer: A Report of Four Cases and Literature Review.

BACKGROUND: Postoperative cerebral embolic stroke is a serious complication of pulmonary lobectomy, occurring in 1.1% of patients undergoing lobectomy through video-assisted thoracoscopic surgery (VATS). The mechanism of this complication is thought to be embolic stroke caused by thrombus formed due to stagnation in the pulmonary vein stump after VATS lobectomy. There have been few reports demonstrating the utility of endovascular treatment (EVT) for cerebral embolic stroke after VATS lobectomy. CASE DESCRIPTION: In our case series, cerebral embolic stroke occurred after VATS pulmonary lobectomy for lung cancer, including the left upper lobe in three cases and the right lobe in one. The median duration of ischemic stroke after VATS was 4.5 days (interquartile range, 2-9 days). The median time from stroke onset to puncture was 130 min. Successful recanalization was achieved in all cases, and two patients achieved favorable clinical outcomes (modified Rankin scale, 0-2). CONCLUSION: We report a case series of four patients who underwent EVT for acute embolic stroke after VATS lobectomy for lung cancer. EVT is considered a reasonable and feasible therapeutic option for this condition.

Increased Cerebral Small Vessel Disease Burden With Renal Dysfunction and Albuminuria in Patients Taking Antithrombotic Agents: The Bleeding With Antithrombotic Therapy 2.

Background The aim of this study was to determine the associations of cerebral small vessel disease (SVD) burden with renal dysfunction and albuminuria in patients taking oral antithrombotic agents. Methods and Results Patients who newly started or continued taking oral antiplatelets or anticoagulants were enrolled in a prospective, multicenter, observational study. Obligatorily acquired multimodal magnetic resonance imaging at registration with prespecified imaging conditions was assessed for cerebral microbleeds, white matter hyperintensities, enlarged basal ganglia perivascular spaces, or lacunes, and an ordinal SVD score was calculated (range, 0-4). Multivariable adjusting covariates were age, sex, hypertension, diabetes, dyslipidemia, current smoking, drinking, and estimated glomerular filtration rate (eGFR). Of 5324 patients (1762 women; median age, 73 years), 4797 (90.1%) patients were taking oral antithrombotic agents for secondary stroke prevention. Cerebral microbleeds were present in 32.7%, confluent white matter hyperintensities in 51.8%, extensive basal ganglia perivascular spaces in 38.9%, and lacunes in 59.4%. Median SVD score was 2. Compared with eGFR category G1 (eGFR ≥90 mL/min per 1.73 m2), adjusted odds ratios for SVD score increment were 1.63 (95% CI, 1.11-2.39) at category G4 (eGFR 15-<30 mL/min per 1.73 m2) and 2.05 (95% CI, 1.33-3.16) at G5 (eGFR <15 mL/min per 1.73 m2). Corresponding odds ratios relative to urinary albumin-to-creatinine ratio (ACR) category A1 (ACR <30 mg/g) were 1.29 (95% CI, 1.12-1.49) for category A2 (ACR 30-<300 mg/g) and 1.37 (95% CI, 1.05-1.77) for A3 (ACR ≥300 mg/g). When combined eGFR and ACR categories were assessed, risks for SVD score increment generally increased as eGFR decreased and ACR increased. Conclusions Both reduced eGFR and albuminuria were independently associated with increased cerebral SVD burden in patients requiring oral antithrombotic medication mainly for secondary stroke prevention. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT01581502; URL: https://www.umin.ac.jp/ctr; Unique identifier: UMIN000023669.

Clinical Course of Abducens Nerve Palsy in Patients with Ruptured Vertebral Artery Dissecting Aneurysms.

Objective: There are few detailed reports on abducens nerve palsy due to a ruptured vertebral artery dissecting aneurysm (VADA). We investigated the clinical characteristics and long-term course of abducens nerve palsy in ruptured VADA patients treated by endovascular surgery. Methods: Of the 51 cases of ruptured VADA treated by endovascular intervention from 2011 to 2019, 31 with a good/fair outcome, in which ocular motility disorder was able to be followed, were included and investigated. Results: In all, 11 patients (35.5%) had abducens nerve palsy, and the World Federation of Neurological Surgeons (WFNS) grade and Hunt & Hess (H&H) grade at the time of arrival of patients with abducens nerve palsy were significantly higher than those of patients without abducens nerve palsy. Of the 10 patients who were able to be followed, abducens nerve palsy in 3 completely recovered in 7-180 days. Abducens nerve palsy improved in five patients and remained in two patients. Conclusion: More severe neurological findings on admission reflect a higher rate of abducens nerve palsy. Diplopia induced by abducens nerve palsy is one of the most important sequelae of ruptured VADA, which impairs the daily activities of the patients. Some cases of abducens nerve palsy improve over a long period. Therefore, appropriate diagnosis and follow-up should be concerned.

Correlation between the CT Perfusion Parameter Values and Response to Recanalization in Patients with Acute Ischemic Stroke.

Objective: CT perfusion (CTP) provides various hemodynamic parameters. However, it is unclear which CTP parameters are useful in predicting clinical outcome in patients with acute ischemic stroke (AIS). Methods: Between February 2019 and June 2021, patients with anterior circulation large-vessel occlusion who achieved successful recanalization within 8 hours after stroke onset were included. The relative CTP parameter values analyzed by the reformulated singular value decomposition (SVD) method in the affected middle cerebral artery territories compared to those in the unaffected side were calculated. In addition, the ischemic core volume (ICV) was evaluated using a Bayesian Vitrea. The final infarct volume (FIV) was assessed by 24-hour MRI. The correlation between these CTP-derived values and clinical outcome was assessed. Results: Forty-two patients were analyzed. Among the CTP-related parameters, the ICV, relative cerebral blood volume (rCBV), and relative mean transit time (rMTT) showed a strong correlation with the FIV (ρ = 0.74, p <0.0001; ρ = -0.67, p <0.0001; and ρ = -0.66, p <0.0001, respectively). In multivariate analysis, rCBV, rMTT, and ICV were significantly associated with good functional outcome, which was defined as a modified Rankin Scale score ≤2 (OR, 6.87 [95% CI, 1.20-39.30], p = 0.0303; OR, 11.27 [95% CI, 0.97-130.94], p = 0.0269; and OR, 36.22 [95% CI, 2.78-471.18], p = 0.0061, respectively). Conclusion: Among the CTP parameters analyzed by the SVD deconvolution algorithms, rCBV and rMTT could be useful imaging predictors of response to recanalization in patients with AIS, and the performances of these variables were similar to that of the ICV calculated by the Bayesian Vitrea.

Refractory in-stent stenosis after flow diverter stenting associated with delayed cobalt allergic reaction.

In-stent stenosis (ISS) triggered by a metal-induced allergic reaction of Pipeline embolization device (PED) placement is extremely rare. The present report describes a patient who presented with delayed parent artery occlusion and refractory ISS after PED placement due to cobalt allergy. A patient in her 70s underwent PED placement for a right internal carotid artery (ICA) large aneurysm; 4 months later, the patient presented with left-sided hemiparesis, and MRI revealed right ICA occlusion even though antiplatelet therapy was optimal. She underwent mechanical thrombectomy, and successful recanalization was achieved. However, follow-up angiography 6 months after the thrombectomy revealed severe ISS, and the patch testing showed a positive reaction for cobalt. As a result of long-term administration of oral steroids and antihistamine, progression of ISS was suppressed. It was supposed that a delayed hypersensitivity reaction to cobalt might induce refractory ISS after PED placement.