Association between CT Perfusion Parameters and Hemorrhagic Transformation after Endovascular Treatment in Acute Ischemic Stroke: Results from the ESCAPE-NA1 Trial.

BACKGROUND AND PURPOSE: Hemorrhagic transformation can occur as a complication of endovascular treatment for acute ischemic stroke. This study aimed to determine whether ischemia depth as measured by admission CTP metrics can predict the development of hemorrhagic transformation at 24 hours. MATERIALS AND METHODS: Patients with baseline CTP and 24-hour follow-up imaging from the ESCAPE-NA1 trial were included. RAPID software was used to generate CTP volume maps for relative CBF, CBV, and time-to-maximum at different thresholds. Hemorrhage on 24-hour imaging was classified according to the Heidelberg system, and volumes were calculated. Univariable and multivariable regression analyses assessed the association between CTP lesion volumes and hemorrhage/hemorrhage subtypes. RESULTS: Among 408 patients with baseline CTP, 142 (35%) had hemorrhagic transformation at 24-hour follow-up, with 89 (63%) classified as hemorrhagic infarction (HI1/HI2), and 53 (37%), as parenchymal hematoma (PH1/PH2). Patients with HI or PH had larger volumes of low relative CBF and CBV at each threshold compared with those without hemorrhage. After we adjustied for baseline and treatment variables, only increased relative CBF <30% lesion volume was associated with any hemorrhage (adjusted OR, 1.14; 95% CI, 1.02-1.27 per 10 mL), as well as parenchymal hematoma (adjusted OR, 1.23; 95% CI, 1.06-1.43 per 10 mL). No significant associations were observed for hemorrhagic infarction. CONCLUSIONS: Larger "core" volumes of relative CBF <30% were associated with an increased risk of PH following endovascular treatment. This particular metric, in conjunction with other clinical and imaging variables, may, therefore, help estimate the risk of post-endovascular treatment hemorrhagic complications.

Prevalence of "Ghost Infarct Core" after Endovascular Thrombectomy.

BACKGROUND AND PURPOSE: Baseline CTP sometimes overestimates the size of the infarct core ("ghost core" phenomenon). We investigated how often CTP overestimates infarct core compared with 24-hour imaging, and aimed to characterize the patient subgroup in whom a ghost core is most likely to occur. MATERIALS AND METHODS: Data are from the randomized controlled ESCAPE-NA1 trial, in which patients with acute ischemic stroke undergoing endovascular treatment were randomized to intravenous nerinetide or placebo. Patients with available baseline CTP and 24-hour follow-up imaging were included in the analysis. Ghost infarct core was defined as CTP core volume minus 24-hour infarct volume > 10 mL). Clinical characteristics of patients with versus without ghost core were compared. Associations of ghost core and clinical characteristics were assessed by using multivariable logistic regression. RESULTS: A total of 421 of 1105 patients (38.1%) were included in the analysis. Forty-seven (11.2%) had a ghost core > 10 mL, with a median ghost infarct volume of 13.4 mL (interquartile range 7.6-26.8). Young patient age, complete recanalization, short last known well to CT times, and possibly male sex were associated with ghost infarct core. CONCLUSIONS: CTP ghost core occurred in ∼1 of 10 patients, indicating that CTP frequently overestimates the infarct core size at baseline, particularly in young patients with complete recanalization and short ischemia duration.

Modeling diffusion-weighted imaging lesion expansion between 2 and 24 h after endovascular thrombectomy in acute ischemic stroke.

PURPOSE: Diffusion-weighted imaging (DWI) lesion expansion after endovascular thrombectomy (EVT) is not well characterized. We used serial diffusion-weighted magnetic resonance imaging (MRI) to measure lesion expansion between 2 and 24 h after EVT. METHODS: In this single-center observational analysis of patients with acute ischemic stroke due to large vessel occlusion, DWI was performed post-EVT (< 2 h after closure) and 24-h later. DWI lesion expansion was evaluated using multivariate generalized linear mixed modeling with various clinical moderators. RESULTS: We included 151 patients, of which 133 (88%) had DWI lesion expansion, defined as a positive change in lesion volume between 2 and 24 h. In an unadjusted analysis, median baseline DWI lesion volume immediately post-EVT was 15.0 mL (IQR: 6.6-36.8) and median DWI lesion volume 24 h post-EVT was 20.8 mL (IQR: 9.4-66.6), representing a median change of 6.1 mL (IQR: 1.5-17.7), or a 39% increase. There were no significant associations among univariable models of lesion expansion. Adjusted models of DWI lesion expansion demonstrated that relative lesion expansion (defined as final/initial DWI lesion volume) was consistent across eTICI scores (0-2a, 0.52%; 2b, 0.49%; 2c-3, 0.42%, p = 0.69). For every 1 mL increase in lesion volume, there was 2% odds of an increase in 90-day mRS (OR: 1.021, 95%CI [1.009, 1.034], p < 0.001). CONCLUSION: We observed substantial lesion expansion post-EVT whereby relative lesion expansion was consistent across eTICI categories, and greater absolute lesion expansion was associated with worse clinical outcome. Our findings suggest that alternate endpoints for cerebroprotectant trials may be feasible.

Prospective Margin Estimates Predict Local Tumor Progression Following Microwave Ablation of Small Renal Masses.

PURPOSE: To evaluate the relationship between prospectively generated ablative margin estimates and local tumor progression (LTP) among patients undergoing microwave ablation (MWA) of small renal masses (SRMs). MATERIALS AND METHODS: Between 2017 and 2020, patients who underwent MWA for SRM were retrospectively identified. During each procedure, segmented kidney and tumor shapes were coregistered with intraprocedural helical CT images obtained after microwave antenna placement. Predicted ablation zone shape and size were then overlaid onto the resultant model, and a model-to-model distance algorithm was employed to calculate multiple ablative margin estimates. LTP was modeled as a function of each margin estimate by hazard regression. Models were evaluated using hazard ratios and Akaike information criterion. Receiver operating characteristic curve area under the curve was also estimated using Harrell's and Uno's C indices (HI and UI, respectively). RESULTS: One hundred and twenty-eight patients were evaluated (median age 72.1 years). Mean tumor diameter was 2.4 ± 0.9 cm. LTP was observed in nine (7%) patients. Analysis showed that decreased estimated margin size as measured by first quartile (Q1; 25th percentile), maximum, and average ablative margin metrics was significantly associated with risk of LTP. For every one millimeter increase in Q1, maximum, and mean ablative margin, the hazard of LTP increased 67% (HR: 1.67; 95% CI = 1.25-2.20, UI = 0.93, HI = 0.77), 32% (HR: 1.32; 95% CI 1.09-1.60; UI = 0.93; HI = 0.76), and 48% (HR: 1.48; 95% CI 1.18-1.85; UI = 0.83; HI = 0.75), respectively. CONCLUSION: Prospectively generated ablative margin estimates can be used to predict the risk of local tumor progression following microwave ablation of small renal masses. LEVEL OF EVIDENCE 3: Retrospective cohort study.

Endovascular therapy in acute ischemic stroke with poor reperfusion is associated with worse outcomes compared with best medical management: a HERMES substudy.

BACKGROUND: Functional outcomes in patients with acute ischemic stroke (AIS) with large vessel occlusion (LVO) undergoing endovascular treatment (EVT) with poor reperfusion were compared with patients with AIS-LVO treated with best medical management only. METHODS: Data are from the HERMES collaboration, a patient-level meta-analysis of seven randomized EVT trials. Baseline characteristics and functional outcomes (modified Rankin Scale (mRS) score at 90 days) were compared between patients with poor reperfusion (defined as modified Thrombolysis in Cerebral Infarction Score 0-1 on the final intracranial angiography run as assessed by the central imaging core laboratory) and patients in the control arm with multivariable logistic ordinal logistic regression adjusted for pre-specified baseline variables. RESULTS: 972 of 1764 patients from the HERMES collaboration were included in the analysis: 893 in the control arm and 79 in the EVT arm with final mTICI 0-1. Patients with poor reperfusion who underwent EVT had higher baseline National Institutes of Health Stroke Scale than controls (median 19 (IQR 15.5-21) vs 17 (13-21), P=0.011). They also had worse mRS at 90 days compared with those in the control arm in adjusted analysis (median 4 (IQR 3-6) vs median 4 (IQR 2-5), adjusted common OR 0.59 (95% CI 0.38 to 0.91)). Symptomatic intracranial hemorrhage was not different between the two groups (3.9% vs 3.5%, P=0.75, adjusted OR 0.94 (95% CI 0.23 to 3.88)). CONCLUSION: Poor reperfusion after EVT was associated with worse outcomes than best medical management, although no difference in symptomatic intracranial hemorrhage was seen. These results emphasize the need for additional efforts to further improve technical EVT success rates.

The Vessel Has Been Recanalized: Now What?

When treating acute ischemic stroke patients in our daily clinical practice, we strive to achieve recanalization of the occluded blood vessel as fast as possible using pharmacological thrombolysis and mechanical clot removal. However, successful recanalization does not equal successful reperfusion of the ischemic tissue due to mechanisms such as microvascular obstruction. Even if successful reperfusion is achieved, numerous other post-recanalization tissue damage mechanisms may impair patient outcomes, namely blood-brain barrier breakdown, reperfusion injury and excitotoxicity, late secondary changes, and post-infarction local and global brain atrophy. Several cerebroprotectants are currently evaluated as adjunctive treatments to pharmacological thrombolysis and mechanical clot removal, many of which interfere with post-recanalization tissue damage pathways. However, our current lack of knowledge about the prevalence and importance of the various post-recanalization tissue damage mechanisms makes it difficult to reliably identify the most promising cerebroprotectants and to design appropriate clinical trials to evaluate them. Serial human MRI studies with complementary animal studies in higher order primates could provide answers to these critical questions and should be first conducted to allow for adequate cerebroprotection trial design, which could accelerate the translation of cerebroprotective agents from bench to bedside to further improve patient outcomes.

A hierarchical anatomical framework and workflow for organizing stereotactic encephalography in epilepsy.

Stereotactic electroencephalography (SEEG) is an increasingly utilized method for invasive monitoring in patients with medically intractable epilepsy. Yet, the lack of standardization for labeling electrodes hinders communication among clinicians. A rational clustering of contacts based on anatomy rather than arbitrary physical leads may help clinical neurophysiologists interpret seizure networks. We identified SEEG electrodes on post-implant CTs and registered them to preoperative MRIs segmented according to an anatomical atlas. Individual contacts were automatically assigned to anatomical areas independent of lead. These contacts were then organized using a hierarchical anatomical schema for display and interpretation. Bipolar-referenced signal cross-correlations were used to compare the similarity of grouped signals within a conventional montage versus this anatomical montage. As a result, we developed a hierarchical organization for SEEG contacts using well-accepted, free software that is based solely on their post-implant anatomical location. When applied to three example SEEG cases for epilepsy, clusters of contacts that were anatomically related collapsed into standardized groups. Qualitatively, seizure events organized using this framework were better visually clustered compared to conventional schemes. Quantitatively, signals grouped by anatomical region were more similar to each other than electrode-based groups as measured by Pearson correlation. Further, we uploaded visualizations of SEEG reconstructions into the electronic medical record, rendering them durably useful given the interpretable electrode labels. In conclusion, we demonstrate a standardized, anatomically grounded approach to the organization of SEEG neuroimaging and electrophysiology data that may enable improved communication among and across surgical epilepsy teams and promote a clearer view of individual seizure networks.

Incidence, Characteristics, and Outcomes of Pseudomeningocele and Cerebrospinal Fluid Fistula after Posterior Fossa Surgery.

OBJECTIVE: Posterior fossa approaches are common neurosurgical procedures. Rates of postoperative infection, pseudomeningocele, and cerebrospinal fluid (CSF) fistula are high; however, evidence regarding predisposing risk factors and treatment outcomes remain sparse. METHODS: A retrospective cohort study was carried out of all posterior fossa surgeries conducted at a single institution between January 2015 and October 2019. Univariate statistical methods and stepwise logistic regression were used to assess which factors contributed most to risk of development of postoperative complications. RESULTS: A total of 269 patients were included; 18.6% experienced any postoperative complication, 13% developed either pseudomeningocele or CSF fistula, and 9.7% developed an infection. In multivariate analysis, development of a pseudomeningocele was significantly associated with previous cranial surgery (hazard ratio [HR], 3.15; 95% confidence interval [CI], 1.12-9.28; P = 0.0391). Development of a CSF fistula was significantly associated with index surgery for resection of neoplasm (HR, 7.65; 95% CI, 1.86-22.31; P = 0.0174). Development of an infection was significantly associated with concurrent CSF fistula (HR, 7.16; 95% CI, 1.91-23.19; P = 0.0041) and concurrent pseudomeningocele (HR, 3.41; 95% CI, 1.37-5.95; P = 0.0082) and nonsignificantly associated with diabetes requiring treatment (HR, 2.42; 95% CI, 0.69-8.50; P = 0.168). Other hypothesized risk factors for these complications, such as nonmidline approaches to the posterior fossa, watertight duraplasty, use of dural fibrin sealant, and cranioplasty were not associated with these complications on multivariate analysis. Although many patients with pseudomeningocele were successfully managed with observation, only 38% of patients in whom CSF diversion was attempted avoided surgery. CONCLUSIONS: History of diabetes, cranioplasty, revision surgery, and surgery for tumor resection are identified as risk factors for the development of infection, pseudomeningocele, and CSF fistula, respectively.

Modeling the Clinical Implications of Andexanet Alfa in Factor Xa Inhibitor-Associated Intracerebral Hemorrhage.

BACKGROUND AND OBJECTIVES: Andexanet alfa was recently approved as a reversal agent for the factor Xa inhibitors (FXais) apixaban and rivaroxaban, but its impact on long-term outcomes in FXai-associated intracerebral hemorrhage (ICH) is unknown. We aimed to explore potential clinical implications of andexanet alfa in FXai-associated ICH in this simulation study. METHODS: We simulated potential downstream implications of andexanet alfa across a range of possible hemostatic effects using data from a single center that treats FXai-associated ICH with prothrombin complex concentrate (PCC). We determined baseline probabilities of inadequate hemostasis across patients taking FXai and those not taking FXai via multivariable regression models and then determined the probabilities of unfavorable 3-month outcome (modified Rankin Scale score 4-6) using models comprising established predictors and each patient's calculated probability of inadequate hemostasis. We applied bootstrapping with model parameters from this derivation cohort to simulate a range of hemostatic improvements and corresponding outcomes and then calculated absolute risk reduction (relative to PCC) and projected number needed to treat (NNT) to prevent 1 unfavorable outcome. RESULTS: Training models using real-world patients (n = 603 total, 55 on FXai) had good accuracy in predicting inadequate hemostasis (area under the curve [AUC] 0.78) and unfavorable outcome (AUC 0.78). Inadequate hemostasis was strongly associated with unfavorable outcome (odds ratio 4.5, 95% confidence interval [CI] 2.0-9.9) and occurred in 11.4% of patients taking FXai. Across simulated patients taking FXai comparable to those in A Study in Participants With Andexanet Alfa, a Novel Antidote to the Anticoagulation Effects of Factor Xa Inhibitors (ANNEXA-4) study, predicted absolute risk reduction of unfavorable outcome was 4.9% (95% CI 1.3%-7.8%) when the probability of inadequate hemostasis was reduced by 33% and 7.4% (95% CI 2.0%-11.9%) at 50% reduction, translating to projected NNT of 21 (cumulative cost $519,750) and 14 ($346,500), respectively. DISCUSSION: Even optimistic simulated hemostatic effects suggest that the costs and potential benefits of andexanet alfa should be carefully considered. Placebo-controlled randomized trials are needed before its use can definitively be recommended.