DSC perfusion-based collateral imaging and quantitative T2 mapping to assess regional recruitment of leptomeningeal collaterals and microstructural cortical tissue damage in unilateral steno-occlusive vasculopathy

The relationship between neutrophil-to-lymphocyte ratio and cerebral collateral circulation in patients with symptomatic severe intracranial artery stenosis or occlusion

BACKGROUND

The neutrophil/lymphocyte ratio (NLR) has been considered a prognostic indicator for determining the systemic inflammatory response and atherosclerosis. We aimed to determine the relationship between NLR and the development of cerebral collateral circulation in patients with symptomatic severe stenosis or occlusion of intracranial arteries.

METHODS

All patients underwent digital subtraction angiography (DSA) within 14 days of admission and were divided into a group with good collateral circulation (77 patients) and a group with poor collateral circulation (86 patients) according to the DSA collateral compensation grading method. Apo B, total cholesterol, LDL, and Neutrophil count in the poor side branch group were significantly higher than in the good side branch group. Multifactorial analysis showed that high NLR levels were a valid predictor of poor collateral circulation in patients with symptomatic severe intracranial artery stenosis or occlusion. Spearman correlation analysis showed that the size of the collateral branch score was negatively correlated with NLR (r = -0.509, P < 0.001) and cholesterol content (r = -0.249, P = 0.002). NLR predicted poor collateral circulation with an AUC of 0.620 (sensitivity 66.7 %, specificity 61.3 %, 95 % CI = 0.517-0.723,P < 0.05).

CONCLUSION

We demonstrate a correlation between NLR levels and the development of collateral circulation in the brain in patients with symptomatic severe stenosis or occlusion of the intracranial arteries.

Factors affecting the outcomes of tirofiban after endovascular treatment in acute ischemic stroke: Experience from a single center

AIMS

To investigate the predicted factors influencing the outcomes in acute ischemic stroke (AIS) patients who received tirofiban after endovascular treatment (EVT) and the optimal administration of tirofiban.

METHODS

In this retrospective study, AIS patients who received EVT followed by tirofiban between January 2017 and October 2021 were enrolled. The dose and duration of tirofiban were adjusted by trained clinicians according to the patient's clinical status. A reduction of at least four points on the National Institutes of Health Stroke Scale (NIHSS) after tirofiban compared with that before tirofiban was defined as an effective response. A modified ranking scale (mRS) of 0-2 was defined as a favorable outcome at a 90-day follow-up.

RESULTS

A total of 260 consecutive patients were enrolled, and 36.5% of patients achieved a favorable outcome. The modified thrombolysis in cerebral infarction (mTICI) 2b-3 occurred in 93.5% of patients. Symptomatic intracerebral hemorrhage (sICH) occurred in 6.2% of patients, and the mortality at 90-day follow-up was 16.9%. Duration of tirofiban >24 h (adjusted OR: 2.545; 95% CI: 1.008-6.423; p = 0.048) and effective response to tirofiban (adjusted OR: 25.562; 95% CI: 9.794-66.715; p < 0.001) were related to the favorable outcome (mRS 0-2). Higher NIHSS (adjusted OR: 0.855; 95% CI: 0.809-0.904; p < 0.001) and glucose level on admission (adjusted OR: 0.843; 95% CI: 0.731-0.971; p = 0.018) were predictive for the unfavorable outcome (mRS 3-6).

CONCLUSIONS

An effective response to tirofiban is an independent factor in predicting the long-term efficacy outcome, and extending the duration of tirofiban is beneficial for neurological improvement.

Quantifying cerebral blood arrival times using hypoxia-mediated arterial BOLD contrast

Cerebral blood arrival and tissue transit times are sensitive measures of the efficiency of tissue perfusion and can provide clinically meaningful information on collateral blood flow status. We exploit the arterial blood oxygen level dependent (BOLD) signal contrast established by precisely decreasing, and then increasing, arterial hemoglobin saturation using respiratory re-oxygenation challenges to quantify arterial blood arrival times throughout the brain. We term this approach the Step Hemoglobin re-Oxygenation Contrast Stimulus (SHOCS). Carpet plot analysis yielded measures of signal onset (blood arrival), global transit time (gTT) and calculations of relative total blood volume. Onset times averaged across 12 healthy subjects were 1.1 ± 0.4 and 1.9 ± 0.6 for cortical gray and deep white matter, respectively. The average whole brain gTT was 4.5 ± 0.9 seconds. The SHOCS response was 1.7 fold higher in grey versus white matter; in line with known differences in tissue-specific blood volume fraction. SHOCS was also applied in a patient with unilateral carotid artery occlusion revealing ipsilateral prolonged signal onset with normal perfusion in the unaffected hemisphere. We anticipate that SHOCS will further inform on the extent of collateral blood flow in patients with upstream steno-occlusive vascular disease, including those already known to manifest reductions in vasodilatory reserve capacity or vascular steal.

Collateral Supply in Preclinical Cerebral Stroke Models

Enhancing the collateral blood supply during the acute phase of cerebral ischemia may limit both the extension of the core infarct, by rescuing the penumbra area, and the degree of disability. Many imaging techniques have been applied to rodents in preclinical studies, to evaluate the magnitude of collateral blood flow and the time course of responses during the early phase of ischemic stroke. The collateral supply follows several different routes at the base of the brain (the circle of Willis) and its surface (leptomeningeal or pial arteries), corresponding to the proximal and distal collateral pathways, respectively. In this review, we describe and illustrate the cerebral collateral systems and their modifications following pre-Willis or post-Willis occlusion in rodents. We also review the potential pharmaceutical agents for stimulating the collateral blood supply tested to date. The time taken to establish a collateral blood flow supply through the leptomeningeal anastomoses differs between young and adult animals and between different species and genetic backgrounds. Caution is required when transposing preclinical findings to humans, and clinical trials must be performed to check the added value of pharmacological agents for stimulating the collateral blood supply at appropriate time points. However, collateral recruitment appears to be a rapid, beneficial, endogenous mechanism that can be stimulated shortly after artery occlusion. It should be considered a treatment target for use in addition to recanalization strategies.

Leptomeningeal collateral activation indicates severely impaired cerebrovascular reserve capacity in patients with symptomatic unilateral carotid artery occlusion

For patients with symptomatic unilateral internal carotid artery (ICA) occlusion, impaired cerebrovascular reactivity (CVR) indicates increased stroke risk. Here, the role of collateral activation remains a matter of debate, whereas angio-anatomical collateral abundancy does not necessarily imply sufficient compensatory flow provided. We aimed to further elucidate the role of collateral activation in the presence of impaired CVR. From a prospective database, 62 patients with symptomatic unilateral ICA occlusion underwent blood oxygenation-level dependent (BOLD) fMRI CVR imaging and a transcranial Doppler (TCD) investigation for primary and secondary collateral activation. Descriptive statistic and multivariate analysis were used to evaluate the relationship between BOLD-CVR values and collateral activation. Patients with activated secondary collaterals exhibited more impaired BOLD-CVR values of the ipsilateral hemisphere (p = 0.02). Specifically, activation of leptomeningeal collaterals showed severely impaired ipsilateral hemisphere BOLD-CVR values when compared to activation of ophthalmic collaterals (0.05 ± 0.09 vs. 0.12 ± 0.04, p = 0.005). Moreover, the prediction analysis showed leptomeningeal collateral activation as a strong independent predictor for ipsilateral hemispheric BOLD-CVR. In our study, ipsilateral leptomeningeal collateral activation is the sole collateral pathway associated with severely impaired BOLD-CVR in patients with symptomatic unilateral ICA occlusion.

Influence of hypertension classification on hypertensive intracerebral hemorrhage location

The authors sought to explore whether hypertension classification was risk factor for lobar and non‐lobar hypertensive intracerebral hemorrhage (HICH) and the prognosis in patients with hematoma. This retrospective cohort study was conducted on HICH patients admitted at the First Affiliated Hospital of Soochow University. Observations with first‐ever intracerebral hemorrhage (ICH) were recruited. The authors divided the brain image into three groups according to the location of ICH to predict whether there were significant differences between lobar and non‐lobar ICH. A Mann‐Whitney U test was used and this retrospective trial also compared the operation and mortality rates. Our cohort included 209 patients (73.7% male; median age:60.5±16.7). The overall incidence of lobar HICH was less than non‐lobar HICH (24.4% vs. 68.4%), 7.2% cases of mixed HICH was included in this analysis. In a Mann‐Whitney U test analyze, it indicated that there were significant differences in hypertension classification between lobar and non‐lobar HICH (Z = ‐3.3, p<.05). And the percentage of hematoma in lobar areas with relatively slightly high blood pressure (BP) (high normal and grade 1 hypertension) accounts for 52.9% versus 30.1% in non‐lobar areas. The increasing trends of the prevalent rate of lobar ICH with BP rising were not remarkable. The non‐lobar HICH showed a sharper increase in the condition of grade 3 hypertension compared with lobar HICH. During the period of research, the fatality of lobar hemorrhage was 2.9% versus 7.7% (non‐lobar). Besides, the fatality incidence of HICH with relatively slightly high BP (high normal and grade 1 hypertension) was lower than poorly controlled hypertensive patients (grade 2 and grade 3 hypertension). (8.0% vs. 15.7%). The increase of hypertension classification will aggravate the occurrence of non‐lobar ICH and positively corrected with BP, but not in lobar areas. It is essential to understand the distinction influence of hypertension classification between lobar and non‐lobar ICH.

Multiparametric Quantitative MRI in Neurological Diseases

Magnetic resonance imaging (MRI) is the gold standard imaging technique for diagnosis and monitoring of many neurological diseases. However, the application of conventional MRI in clinical routine is mainly limited to the visual detection of macroscopic tissue pathology since mixed tissue contrasts depending on hardware and protocol parameters hamper its application for the assessment of subtle or diffuse impairment of the structural tissue integrity. Multiparametric quantitative (q)MRI determines tissue parameters quantitatively, enabling the detection of microstructural processes related to tissue remodeling in aging and neurological diseases. In contrast to measuring tissue atrophy via structural imaging, multiparametric qMRI allows for investigating biologically distinct microstructural processes, which precede changes of the tissue volume. This facilitates a more comprehensive characterization of tissue alterations by revealing early impairment of the microstructural integrity and specific disease-related patterns. So far, qMRI techniques have been employed in a wide range of neurological diseases, including in particular conditions with inflammatory, cerebrovascular and neurodegenerative pathology. Numerous studies suggest that qMRI might add valuable information, including the detection of microstructural tissue damage in areas appearing normal on conventional MRI and unveiling the microstructural correlates of clinical manifestations. This review will give an overview of current qMRI techniques, the most relevant tissue parameters and potential applications in neurological diseases, such as early (differential) diagnosis, monitoring of disease progression, and evaluating effects of therapeutic interventions.