Microhemorrhagic transformation of ischemic lesions on T2*-weighted magnetic resonance imaging after Pipeline embolization device treatment

Nomogram for predicting delayed intraparenchymal hemorrhage after pipeline embolization device treatment in patients with intracranial aneurysms: a multicenter, retrospective model development and validation study

BACKGROUND

Delayed intraparenchymal hemorrhage (DIPH) is a severe complication after pipeline embolization device (PED) deployment for intracranial aneurysms (IAs). However, predictive models are lacking. This study aims to develop and validate a new nomogram to predict DIPH risk in IA patients.

METHODS

This retrospective study included 959 IA patients treated with PEDs at three institutions between October 2018 and June 2024. Patients were categorized into a training cohort (n=685) and a validation cohort (n=274). Predictors were identified using the least absolute shrinkage and selection operator and multivariable regression analyses. A nomogram was developed based on these predictors. The area under the receiver operating characteristic curve (AUC), calibration curves, and decision curve analysis (DCA) were utilized to assess the predictive accuracy and clinical value of the nomograms.

RESULTS

The incidence of DIPH was 2.3% in the training cohort. Multivariate logistic regression analysis demonstrated that age (odds ratio [OR] per 10 years, 2.063, P=0.005), maximum diameter (OR, 1.099, P=0.004), adenosine diphosphate-induced maximal platelet aggregation (OR, 0.896, P<0.001), and overlapping devices (OR, 7.226, P=0.007) were independent risk factors for DIPH. A nomogram was developed based on these four predictors. The AUCs of the nomogram in the training and validation cohorts were 0.875 (95% CI, 0.762 to 0.988) and 0.886 (95% CI, 0.757 to 1.000), respectively. The calibration curve and DCA analyses confirmed the utility and clinical applicability of the nomogram.

CONCLUSION

A simple to use nomogram for the individualized prediction of DIPH after PED treatment in patients with IAs was constructed, which may facilitate early identification of high-risk patients and the development of advanced treatment strategies.

Active drug-coated flow diverter in a preclinical model of intracranial stenting

BACKGROUND

Flow diverters carry the risk of thromboembolic complications (TEC). We tested a coating with covalently bound heparin that activates antithrombin to address TEC by locally downregulating the coagulation cascade. We hypothesized that the neuroimaging evidence of TEC would be reduced by the coating.

METHODS

16 dogs were implanted with overlapping flow diverters in the basilar artery, separated into two groups: heparin-coated (n=9) and uncoated (n=7). Following implantation, high-frequency optical coherence tomography (HF-OCT) was acquired to quantify acute thrombus (AT) formation on the flow diverters. MRI was performed postoperatively and repeated at 1, 2, 3, 4, and 8 weeks, consisting of T1-weighted imaging, time-0f-flight (ToF), diffusion weighted imaging (DWI), susceptibility weighted imaging (SWI), and fluid attenuated inversion recovery (FLAIR) sequences. Neurological examinations were performed throughout the 8-week duration of the study.

RESULTS

The mean AT volume on coated devices was lower than uncoated (0.014 vs 0.018 mm3); however, this was not significant (P=0.3). The mean number of foci of magnetic susceptibility artifacts (MSAs) on SWI was significantly different between the uncoated and coated groups at the 1-week follow-up (P<0.02), and remained statistically different throughout the duration of the study. The AT volume showed a direct linear correlation with the MSA count and 80% of the variance in the MSA could be explained by the AT volume (P<0.001). Pathological analysis showed evidence of ischemic injury at locations of MSA.

CONCLUSIONS

Heparin-coated flow diverters significantly reduced the number of new MSAs after 1 week follow-up, showing the potential to reduce TEC.

Classification and hemodynamic characteristics of delayed intracerebral hemorrhage following stent-assisted coil embolism in unruptured intracranial aneurysms

Background and objective

Stent-assisted coil (SAC) embolization is a commonly used endovascular treatment for unruptured intracranial aneurysms (UIAs) but can be associated with symptomatic delayed intracerebral hemorrhage (DICH). Our study aimed to investigate the hemodynamic risk factors contributing to DICH following SAC embolization and to establish a classification for DICH predicated on hemodynamic profiles.

Methods

This retrospective study included patients with UIAs located in the internal carotid artery (ICA) treated with SAC embolization at our institution from January 2021 to January 2022. We focused on eight patients who developed postoperative DICH and matched them with sixteen control patients without DICH. Using computational fluid dynamics, we evaluated the hemodynamic changes in distal arteries [terminal ICA, the anterior cerebral artery (ACA), and middle cerebral artery (MCA)] pre-and post-embolization. We distinguished DICH-related arteries from unrelated ones (ACA or MCA) and compared their hemodynamic alterations. An imbalance index, quantifying the differential in flow velocity changes between ACA and MCA post-embolization, was employed to gauge the flow distribution in distal arteries was used to assess distal arterial flow distribution.

Results

We identified two types of DICH based on postoperative flow alterations. In type 1, there was a significant lower in the mean velocity increase rate of the DICH-related artery compared to the unrelated artery (-47.25 ± 3.88% vs. 42.85 ± 3.03%; p < 0.001), whereas, in type 2, there was a notable higher (110.58 ± 9.42% vs. 17.60 ± 4.69%; p < 0.001). Both DICH types demonstrated a higher imbalance index than the control group, suggesting an association between altered distal arterial blood flow distribution and DICH occurrence.

Conclusion

DICH in SAC-treated UIAs can manifest as either a lower (type 1) or higher (type 2) in the rate of velocity in DICH-related arteries. An imbalance in distal arterial blood flow distribution appears to be a significant factor in DICH development.

DWI-Detected Ischemic Lesions after Endovascular Treatment for Cerebral Aneurysms: An Updated Systematic Review and Meta-analysis

BACKGROUND AND PURPOSE

DWI-detected ischemic lesions are potential complications of endovascular procedures that are performed to treat intracranial aneurysms. We completed a systematic review and meta-analysis to identify the occurrence of DWI-detected ischemic lesions after endovascular treatment for intracranial aneurysms.

MATERIALS AND METHODS

A systematic literature search of PubMed, the Web of Science, EMBASE, and Scopus between January 2000 and June 2022 of post-endovascular procedures for intracranial aneurysm studies was conducted using the Nested Knowledge AutoLit software. The main outcome was DWI-detected ischemic lesions within 5 days of the procedures. Information regarding associated risk factors such as the type of procedure, patient demographics, and aneurysm characteristics was also collected.

RESULTS

Twenty-nine studies with 2686 patients were included. The overall incidence of DWI ischemic lesions was 47.0% (95% CI, 39.6%-55.8%). The highest rate of lesions was seen with flow diversion at 62.4% (95% CI, 48.4%-80.5%), followed by complex procedures at 49.3% (95% CI, 29.5%-82.1%), stent-assisted coiling at 47.5% (95% CI, 34.6%-65.3%), simple coiling at 47.1% (95% CI, 35.7%-62.3%), and balloon-assisted coiling at 37.0% (95% CI, 28.3%-48.4%). The differences among different techniques were not statistically significant; however, there was significant heterogeneity and a significant risk of publication bias among included studies.

CONCLUSIONS

Many patients who undergo endovascular procedures for intracranial aneurysms present with new postprocedural DWI-detected ischemic lesions, regardless of the endovascular procedure used. Future studies and meta-analyses are needed to investigate early and long-term outcomes of such small infarcts.

Diffusion-weighted imaging lesions after endovascular treatment of cerebral aneurysms: A network meta-analysis

Background

Thromboembolism is one of the common complications in endovascular treatments including coiling alone, stent-assisted coiling (SAC), balloon-assisted coiling (BAC), and flow-diverting (FD) stents. Such treatments are widely used in intracranial aneurysms (IAs), which usually present as positive lesions in diffusion-weighted imaging (DWI). Whether these adjunctive techniques increase postprocedural DWI-positive lesions after endovascular treatment remains unclear.

Methods

A thorough electronic search for the literature published in English between January 2000 and October 2022 was conducted on PubMed, Medline, and EMBASE. Eighteen studies (3 cohort studies and 15 case-control studies) involving 1,843 patients with unruptured IAs (UIAs) were included. We performed a frequentist framework network meta-analysis (NMA) to compare the rank risks of cerebral thromboembolism of the above four endovascular treatments. The incoherence test was used to analyze the statistical disagreement between direct and indirect evidence. Funnel plots were used to analyze publication bias.

Results

The incidences of DWI lesions in patients who received FD stents, SAC, BAC, and coiling alone were 66.1% (109/165), 37.6% (299/795), 31.1% (236/759), and 25.6% (236/921). The incidence of DWI lesions in patients who received FD stents was higher than that in patients who received SAC [OR: 2.40; 95% CI (1.15, 5.00), P < 0.05], BAC [OR: 2.62; 95% CI (1.19, 5.77), P < 0.05], or coiling alone [OR: 2.77; 95% CI (1.26, 6.07), P < 0.05]. The incoherence test showed preferable consistency in this NMA. No obvious publication bias was found in the funnel plot.

Conclusion

FD stent placement brings more ischemic lesions identified by DWI than any other procedures for patients with UIA. The characteristics of FD stents may result in a high incidence of DWI lesions.

The Combination of Stent and Antiplatelet Therapy May Be Responsible of Parenchymal Magnetic Susceptibility Artifacts after Endovascular Procedure

The aim was to assess the occurrence of magnetic susceptibility artifacts (MSA) following endovascular treatment of intracranial aneurysm by stent using susceptibility weighted imaging (SWI). Imaging and clinical data of 46 patients who underwent stent placement in the case of intracranial aneurysm endovascular treatment (S-Group) were retrospectively analyzed and compared to a control group (C-Group) in which 46 patients had coiling alone. The mean number of MSA was higher in the S-group than in the C-group on postprocedural SWI sequence (8.76, 95%CI [5.76; 11.76] vs. 0.78 [0.32; 1.25], respectively, p < 0.001) with a higher frequency of the appearance of MSA also in the S-group (78.26% vs. 21.74% in the C-group, p < 0.001). In the S-group, in the vascular territory of the treated artery, there was a higher number of MSA than in other vascular territories (mean of 5.18 [3.43; 6.92] vs. 3.08 [1.79; 4.36], p = 0.001). An odds ratio (OR) of 20.98 [5.24; 83.95] suggested a higher proportion of onset of MSA in the S-group than in the C-group (p < 0.001). The appearance of MSA after a treatment by stenting for intracranial aneurysm in patients under antiplatelet therapy was common, particularly in the treated artery territory.

Antiplatelet Therapy and Periprocedural Risk Factor Analysis for Pipeline Embolization Device Treatment of Unruptured Internal Carotid Artery Aneurysms: A Retrospective, Multicenter Analysis

BACKGROUND

Aneurysm treatment using the Pipeline Embolization Device has been established but appropriate maintenance of dual antiplatelet therapy (APT) is essential. This multicenter retrospective study assessed whether APT was properly adjusted for clopidogrel resistance and identified risk factors associated with periprocedural complications.

METHODS

Consecutive cases of use of the Pipeline Embolization Device for internal carotid artery aneurysms (>10 mm) between November 2015 and April 2020 were analyzed. Dual APT (aspirin + clopidogrel) was prescribed before treatment. If preprocedural P2Y12 reaction unit (PRU) values were >240, APT was adjusted. Periprocedural complications were compared between APT nonadjustment and adjustment groups and periprocedural risk factors were also analyzed.

RESULTS

A total of 162 procedures were assessed. The mean maximum aneurysm size was 15.35 mm. APT adjustment was required in 47 cases (29.0%), primarily by switching to prasugrel. There were no significant differences in complication incidence between the 2 groups even after propensity score matching. The risk factor independently associated with ischemic complications was a neck size of 8 mm or larger (odds ratio [OR], 5.25; P = 0.018) and restricting analysis to the APT nonadjustment group showed PRU values of 190 or higher (OR, 5.84; P = 0.047) and neck sizes of 8 mm or larger (OR, 7.05; P = 0.029) as significant factors. The risk factor independently associated with hemorrhagic complications was a neck size of 7 mm or larger (OR, 11.57; P = 0.023).

CONCLUSIONS

APT adjustment for clopidogrel resistance was safe and effective. Neck width was a risk factor for both ischemic and hemorrhagic complications. PRU values of 190 or higher were also associated with ischemic complications.

Factors associated with the new appearance of cerebral microbleeds after endovascular treatment for unruptured intracranial aneurysms

PURPOSE

Endovascular treatment of unruptured intracranial aneurysms may increase cerebral microbleeds (CMBs) in postprocedural T2*-weighted MRIs, which may be a risk for future intracerebral hemorrhage. This study examined the characteristics of postprocedural CMBs and the factors that cause their increase.

METHODS

The patients who underwent endovascular treatment for unruptured intracranial aneurysms from April 2016 to February 2018 were retrospectively analyzed. Treatment techniques for endovascular treatment included simple coiling, balloon-assisted coiling, stent-assisted coiling, or flow diverter placement. To evaluate the increase in CMBs, a head MRI including diffusion-weighted imaging and T2*-weighted MRIs was performed on the preprocedural day; the first postprocedural day; and at 1, 3, and 6 months after the procedure.

RESULTS

Among the 101 aneurysms that were analyzed, 38 (37.6%) showed the appearance of new CMBs. In the multivariate analysis examining the causes of the CMB increases, chronic kidney disease, a higher number of preprocedural CMBs, and a higher number of diffusion-weighted imaging-positive lesions on the first postprocedural day were independent risk factors. Furthermore, a greater portion of the increased CMBs was found in cortical and subcortical lesions of the treated vascular perfusion area within 1 month after the procedure.

CONCLUSION

In endovascular treatment for unruptured intracranial aneurysms, CMBs tended to increase in patients with small vessel disease before the procedure, and it was also implicated in hemorrhagic changes after periprocedural microinfarction.

Risk Factor Analysis of Delayed Intracerebral Hemorrhage After Coil Embolization of Unruptured Cerebral Aneurysms

Background: We sought to analyze diffusion-weighted imaging (DWI) and dual antiplatelet therapy (DAPT) for risk factors of delayed intracerebral hemorrhage (d-ICH) after coil embolization for an unruptured intracranial aneurysm (UIA).

Methods: A total of 539 aneurysms were analyzed in this study. Ruptured and flow diverter cases were excluded. All aneurysms enrolled in this study were treated with stent-assisted or simple coiling techniques. Before the procedure, all patients administered (DAPT). After the procedure, patients who underwent stent-assisted coil embolization were given DAPT, and patients who underwent simple coiling were given single antiplatelet therapy (SAPT) only during their admission. The response of the antiplatelet agent was assessed the day before the procedure with The VerifyNow assay. DWI MRI and CT were obtained routinely the next day after the procedure. d-ICH was defined as an intracerebral hemorrhagic lesion identified in follow up CT at least 48 h after the procedure.

Results: A larger positive lesion on day 1 DWI MRI (p = 0.001), the value of PRU (p = 0.002), and the inhibition rate (p = 0.025) were considered meaningful risk factors for d-ICH in univariate analysis. Accordingly, larger DWI positivity (OR = 83.73, 95% CI = 11.132–712.886, P = 0.001) and PRU (OR = 0.98, 95% CI = 0.972–0.999, P = 0.033) reached statistical significance in multivariate analysis.

Conclusions: Thromboembolic infarction may work as an initiating factor, and antiplatelet medication may work as an aggravating factor. We might suggest that a tailored reduction in antiplatelet agents could help reduce d-ICH when a larger volume of post-procedural thromboembolic infarction is seen on 1-day follow-up DWI MRI.

Flow-diverting stent and delayed intracranial bleeding: the case for discussing acquired von Willebrand disease

A unique feature of the flow-diverting stent (FDS) has rendered it useful in the endovascular treatment of selected intracranial aneurysms for the last decade. Delayed aneurysmal rupture and intracranial parenchymal bleeding are two leading hemorrhagic complications after FDS. It has recently been shown for the first time that there is a relationship between FDS and reduced level of vWF activity in patients undergoing endovascular cerebral aneurysm treatment. Here, the current literature is reviewed in the context of this novel finding to propose an illustrative scenario that conceptually links implantation of FDS to delayed intracranial bleeding, through the mechanism of shear-induced activation of vWF. In this scenario, after FDS implantation, sustained release of activated vWF in association with platelets plays a pivotal role in the mechanisms of delayed intracranial hemorrhages.

Treatment of acute thrombosis during stent-assisted coil embolization of ruptured proximal posterior inferior cerebellar artery aneurysm

Aneurysms located in the posterior inferior cerebellar artery (PICA) are not a majority of the intracranial aneurysms cases. Many challenges were addressed in the endovascular procedure to treat the disease. The authors have successfully diagnosed and treated a ruptured proximal PICA aneurysm. However, digital subtraction angiography showed acute thrombosis in the vertebral artery in the procedure, which probably could be an acute in-stent thrombosis. The tirofiban hydrochloride injection was subjected through a microcatheter, and then, the second Neuroform EZ stent was planted. In the 6-month follow-up, no recurrence of the aneurysm and complete patency of the right PICA at the site of aneurysm formation were found. We believe that the treatment of PICA aneurysms with Neuroform EZ stents could get a favorable result. Combination of tirofiban hydrochloride and Neuroform EZ stent could be an effective approach in treating acute thrombotic complications.

Reduced Activity of von Willebrand Factor after Flow-Diverting Stent Implantation for Intracranial Aneurysms: A Link to Acquired von Willebrand Disease?

BACKGROUND AND PURPOSE

Vascular devices generating high shear stress can cause type 2A acquired von Willebrand disease, which is characterized by low von Willebrand factor activity accompanied by hemorrhagic complications. The braided mesh structure of flow-diverting stents with a relatively small strut size can create abnormally high shear stress while arterial blood flows through the stent struts into the aneurysm, and flow-diverting stent may be associated with reduced von Willebrand factor activity.

MATERIALS AND METHODS

Aneurysmal morphologic parameters and patient data were examined retrospectively among patients who had an unruptured intracranial aneurysm treated with a flow-diverting stent. The RISTOtest (test for whole blood ristocetin-induced platelet aggregation) for von Willebrand factor activity, as well as tests for aspirin and clopidogrel/prasugrel effectiveness, were performed immediately before the endovascular procedure and 24 hours later by multiple electrode aggregometry.

RESULTS

A total of 39 patients with 56 aneurysms were recruited, and statistical analyses were performed in 32 patents with 49 aneurysms. Compared with the baseline values, von Willebrand factor activity was reduced in 16 patients but increased in 23 patients. Aneurysmal variables (eg, neck area, volume, volume-to-neck area ratio, size ratio, and morphologic index) clearly distinguished patients with reduced von Willebrand factor activity from those with nonreduced von Willebrand factor activity. The receiver operating characteristic curve showed that the morphologic index and volume had the highest discriminative power, with an area under the curve of 0.99.

CONCLUSIONS

In high-volume/large-neck aneurysms, flow-diverting stent implantation can cause reduced von Willebrand factor activity, which may be linked causally to acquired von Willebrand disease.