Background and Purpose: In acute ischemic stroke (AIS) due to large‐vessel occlusion (LVO), the relationship between cerebral oxygen extraction fraction (OEF) as the hallmark of the ischemic penumbra and leptomeningeal collateral supply is not well established. We aimed to investigate the relationship between pial collateralization and tissue oxygen extraction in patients with LVO using magnetic resonance imaging (MRI).Methods: Data from 14 patients with anterior circulation LVO who underwent MRI before acute stroke treatment were analyzed. In addition to diffusion‐weighted imaging and perfusion‐weighted imaging (PWI), the protocol comprised sequences for multiparametric quantitative blood‐oxygen‐level‐dependent imaging for the calculation of relative OEF (rOEF). Pial collateral supply was quantitatively assessed by analyzing the signal variance in T2*‐weighted PWI time series. Relationships between collateral supply, infarct volume, rOEF in peri‐infarct hypoperfused tissue, and clinical stroke severity were assessed.Results: The PWI‐based parameter quantifying collateral supply was negatively correlated with baseline ischemic core volume and rOEF in the hypoperfused peri‐infarct area (p < .01). Both reduced collateral supply and increased rOEF correlated significantly with higher scores on the National Institutes of Health Stroke Scale (p < .05). Increased rOEF within hypoperfused tissue was associated with higher baseline (p = .043) and follow‐up infarct volume (p = .009).Conclusions: Signal variance‐based mapping of collaterals with PWI depicts pial collateral supply, which is closely tied to tissue pathophysiology and clinical and imaging outcomes. Magnetic‐resonance‐derived mapping of cerebral rOEF reveals penumbral characteristics of hypoperfused tissue and might provide a promising imaging biomarker in AIS.

Background: Besides its more advantageous pharmacological profile compared to alteplase (rt-PA), increasing evidence suggest a favorable clinical efficacy and safety of tenecteplase (TNK) as alternative thrombolytic agent for the treatment of acute ischemic stroke (AIS). We aimed to analyze the short-term effects of the switch in thrombolytics at our tertiary care stroke center. Methods: We performed a retrospective analysis of patients receiving intravenous thrombolysis (IVT) for AIS in the time window < 4.5 h, including patients treated with rt-PA (from January 1st to June 30, 2024) and patients treated with TNK (from July 1st to December 31, 2024). Primary and secondary endpoints were the workflow times and the modified Rankin Scale (mRS) at discharge as the early functional outcome. Safety outcomes included any intracerebral hemorrhage (ICH) on follow-up imaging at 24 h, symptomatic (s)ICH and death by day 7. Results: During the period of 12 months, n = 139 patients received IVT in the 4.5 h time window. Median door to needle (DTN) times were significantly shorter for patients treated with TNK ( n = 74) compared to rt-PA ( n = 65) (TNK 23 min [IQR 32–17] vs. rt-PA 28 min [IQR 33–22], p = 0.047). Patients undergoing endovascular thrombectomy (EVT) after TNK treatment had significantly shorter door to groin (DTG) times in comparison to treatment with rt-PA prior to EVT ( p = 0.002). No significant differences between the groups were found for early functional outcome ( p = 0.194 for patients with, p = 0.852 for patients without EVT), the rate of sICH (TNK vs. rt-PA: 17.6 vs. 4.2%, p = 0.290 with EVT and 3.6 vs. 0%, p = 0.507 without EVT) and mortality (TNK vs. rt-PA: 17.6 vs. 4.2%, p = 0.290 with EVT and 7.0 vs. 2.4%, p = 0.393 without EVT). Conclusions: Transition from rt-PA to TNK for AIS treatment < 4.5 h after onset at a tertiary care center seems feasible and resulted in shorter onset to treatment durations. Functional outcomes at discharge were comparable between the groups. Rates of ICH, sICH and mortality were numerically higher in the TNK group. Further data are required to assess the clinical efficacy and safety of TNK after the transition from rt-PA in real-world scenarios.

Purpose: In acute ischemic stroke with large-vessel occlusion (LVO), collateral assessment with single-phase computed tomography angiography (CTA) might underestimate pial collateral supply in a considerable proportion of patients. We aimed to compare time-resolved magnetic resonance imaging (MRI)-based quantitative collateral mapping to conventional collateral imaging with CTA. Methods: This retrospective single-center study covering a period of 6 years (2012–2018) included drip-and-ship LVO patients who underwent MR imaging after initial imaging evaluation with CT. For MRI-based collateral assessment, T2*-weighted time series from perfusion-weighted imaging (PWI) were processed to compute a quantitative collateral vessel index (CVI_PWI) based on the magnitude of signal variance across the entire acquisition time. CTA-based collateral scores (Tan and Maas) and CVI_PWI were investigated in terms of inter-modality associations between collateral measures, as well as their relationships with stroke severity, infarct volume and early functional outcome. Results: The final analysis included n = 56 patients (n = 31 female, mean age 69.9 ± 14.21 years). No significant relationship was found between MR-based quantitative collateral supply (CVI_PWI) and CT-based collateral scores (r = −0.00057, p = 0.502 and r = −0.124, p = 0.797). In contrast to CVI_PWI, CTA-based collateral scores showed no significant relationship with clinical stroke severity and infarct volume. While MR-based CVI_PWI was independently associated with favorable early functional outcome in multivariate analysis (OR 1.075, 95% CI 1.001–1.153, p = 0.046), CTA-based collateral scores were not significantly associated with outcome. Conclusions: Since collateral scores based on single-phase CTA do not accurately reflect infarct progression and might underestimate pial collateralization in a relevant proportion of patients, they are not associated with early functional outcome in LVO patients. In contrast, CVI_PWI represents a robust imaging parameter of collateral supply and is independently associated with functional outcome.

Background: In cerebral small vessel disease (CSVD), cortical atrophy occurs at a later stage compared to microstructural abnormalities and therefore cannot be used for monitoring short-term disease progression. We aimed to investigate whether cortical diffusion tensor imaging (DTI) and quantitative (q) magnetic resonance imaging (MRI) are able to detect early microstructural involvement of the cerebral cortex in CSVD. Materials and Methods 33 CSVD patients without significant cortical or whole-brain atrophy and 16 healthy control subjects were included and underwent structural MRI, DTI and high-resolution qMRI with T₂, T₂* and T_2′ mapping at 3 T as well as comprehensive cognitive assessment. After tissue segmentation and reconstruction of the cortical boundaries with the Freesurfer software, DTI and qMRI parameters were saved as surface datasets and averaged across all vertices. Results: Cortical diffusivity and quantitative T₂ values were significantly increased in patients compared to controls (p < 0.05). T₂ values correlated significantly positively with white matter hyperintensity (WMH) volume (p < 0.01). Both cortical diffusivity and T₂ showed significant negative associations with axonal damage to the white matter fiber tracts (p < 0.05). Conclusions: Cortical diffusivity and quantitative T₂ mapping are suitable to detect microstructural involvement of the cerebral cortex in CSVD and represent promising imaging biomarkers for monitoring disease progression and effects of therapeutical interventions in clinical studies.

Background: Primary angiitis of the central nervous system (PACNS) is a rare vasculitis affecting CNS blood vessels, posing diagnostic challenges due to the limited specificity of the established diagnostic tools. Neurofilament light chain (NfL) might be a promising biomarker in PACNS. Methods: NfL in serum and CSF was measured in 33 PACNS patients (25 active [aPACNS], 8 in remission [rPACNS]) enrolled between 2014 and 2022 and compared to controls (serum: n = 303; CSF: n = 68); Results: Serum NfL was significantly elevated in aPACNS (median: 45.77 pg/mL) versus rPACNS (6.68 pg/mL; p < 0.001) and healthy controls (6.05 pg/mL; p < 0.001). Similarly, CSF NfL was significantly elevated in aPACNS (median: 4914.58 pg/mL) compared to rPACNS (301.19 pg/mL; p = 0.002) and controls (262.83 pg/mL; p < 0.001). Serum and CSF NfL were significantly correlated (r = 0.90, p < 0.001). Additionally, an association between elevated NfL and ischemic lesions was observed (serum: r = 0.59, p = 0.006; CSF: r = 0.43, p = 0.032). A subgroup analysis excluding stroke patients still revealed elevated NfL in 90% (CSF) and 50% (serum), with diminishing discriminatory power with older age. Conclusions: NfL holds potential as a biomarker for PACNS, in particular in younger patients.

Background and purpose: Despite the fundamental role of pial collateral vessels in limiting the progression of ischemic tissue injury in acute stroke with large vessel occlusion (LVO), in addition to the fact that collateral vessel abundance varies naturally from person to person for genetic reasons, there is limited knowledge regarding potential factors contributing to inherent interindividual variation in pial collateral supply. As it has been repeatedly hypothesized that chronic carotid occlusive disease may favor pial collateralization, we aimed to investigate the association between quantitatively assessed leptomeningeal collateral supply and pre-existing carotid stenosis in patients with acute stroke due to LVO.Materials and methods: Patients with proximal middle cerebral artery (MCA) occlusion with or without additional internal carotid artery (ICA) occlusion were included. The degree of collateral supply was quantitatively assessed based on signal variance in T2*-weighted time series in perfusion-weighted magnetic resonance imaging (PWI). Patients were stratified into two groups according to quantitative collateral status (poor and fair to good collateral supply). The prevalence of high-grade ICA stenosis (≥70%) was evaluated in both groups.Results: A total of 98 patients (mean age 68.8 ± 16.1 years, n = 52 (53.1%) of whom were female individuals) with MCA and/or ICA occlusion were included in the final analysis. Out of these patients, 42 had poor collateral supply, while 56 exhibited fair to good collateral supply. Additionally, 18 patients showed ipsilateral high-grade ICA stenosis. After classifying the entire cohort based on their collateral status (poor vs. fair to good collateral supply), there was no significant difference in the proportion of the patients with ipsilateral high-grade ICA stenosis between the two groups. Specifically, 6 (14.3%) patients had poor collateral supply, and 12 (21.1%) patients had fair to good collateral supply. The odds ratio (OR) was 1.58, with a 95% confidence interval (CI) of 0.490–5.685 and the p-value of 0.440. In the entire patient cohort, signal variance-based collateral supply was significantly correlated with initial stroke severity (r = −0.360, p < 0.001), baseline ischemic core volume (r = −0.362, p < 0.001), and functional outcomes (score on the modified Rankin Scale) at discharge (r = −0.367, p < 0.01).Conclusion: In this study, we performed a quantitative and observer-independent MRI-based collateral assessment in patients with LVO. We found no significant difference in the prevalence of pre-existing high-grade ICA stenosis between patients with fair to good collateral supply and those with poor collateral supply. The potential influence of demographic and clinical variables on pial collateral supply in patients with acute stroke warrants further exploration in future studies. MRI-based collateral supply is significantly related to initial stroke severity, ischemic core volume, and early functional outcomes.