Dynamic Evolution of Diffusion-Weighted Imaging Lesions in Patients With Minor Ischemic Stroke

The fuzzy MAD stroke conjecture, using Fuzzy C Means to classify multimodal apparent diffusion for ischemic stroke lesion stratification

BACKGROUND

In conjunction with an epidemiologically determined treatment window, current radiological acute ischemic stroke practice discerns two lesion (stage) types: core (dead tissue, identified by diffusion-weighted imaging (DWI)) and penumbra (tissue region receiving just enough blood flow to be potentially salvageable, identified by the perfusion diffusion mismatch). However, advancements in preclinical and clinical studies have indicated that this approach may be too rigid, warranting a more fine-grained patient-tailored approach. This study aimed to demonstrate the ability to noninvasively provide insights into the current in vivo stroke lesion cascade.

METHODS

To elucidate a finer-grained depiction of the acute focal ischemic stroke cascade in vivo, we retrospectively applied our multimodal apparent diffusion (MAD) method to multi-b-value DWI, up to a b-value of 10,000 s/mm2 in 34 patients with acute focal ischemic stroke. Fuzzy C Means was used to cluster the MAD parameters.

RESULTS

We discerned 18 clusters consistent with normal appearing tissue (NAT) types and 14 potential ischemic lesion (stage) types, providing insights into the variability and aggressiveness of lesion progression and current anomalous stroke-related imaging features. Of the 529 ischemic stroke lesion instances previously identified by two radiologists, 493 (92 %) were autonomously identified; 460 (87 %) were identified as efficaciously or better than the radiologists.

CONCLUSIONS

The data analyzed included a small number of clinical patients without follow-up or contemporaneous histology; therefor, the findings and theorizing should be treated as conjecture. Nevertheless, each identified NAT and lesion type is consistent with the known underpinnings of physiological tissues and pathological ischemic stroke lesion (stage) types. Several findings should be considered in current clinical imaging: WM fluid accumulation, BBB compromise conundrum, b1000 identified core may not be dead tissue, and a practical reason for DWI (pseudo) normalization.

Effects of Oral Antiplatelet Agents and Tirofiban on Functional Outcomes of Patients with Non-Disabling Minor Acute Ischemic Stroke

BACKGROUND AND PURPOSE

Over half of patients with acute ischemic stroke present with minor neurologic deficits. We investigated the effects of oral antiplatelet agents vs. tirofiban, a highly selective GP IIb/IIIa antiplatelet drug, on functional outcomes of stroke patients with non-disabling neurologic deficits.

METHODS

This retrospective study analyzed data of 125 patients with minor stroke who had National Institutes of Health Stroke Scale (NIHSS) scores of 5 or less within 6 hours of stroke symptom onset between January 2010 and June 2018. All patients were selected from the Department of Neurology at the Third Affiliated Hospital of Army Medical University. There were 54 cases in each group after propensity score matching, in which patients received oral antiplatelet agents (n = 64) and tirofiban (n = 61). Safety outcomes were assessed by incident intracranial hemorrhage, systemic bleeding and death. Efficacy outcomes were assessed using the NIHSS score at 24 hrs, 7 days or at discharge, and clinical deterioration. The modified rankin scale (mRs) was assessed at 90 days.

RESULTS

No significant differences were found in the incidence of intracranial hemorrhage, systemic bleeding or death between groups (P>0.05). Although neurological function improved significantly in both groups, NIHSS scores were lower in the tirofiban group compared with those in the oral antiplatelet agents group at 24 hrs (1 versus 3, P = 0.000), 7 days or at discharge (0 versus 2, P = 0.000). The clinical deterioration rate was higher in the oral antiplatelet agents group than in the tirofiban group, but without significance (16.7% versus 5.6%, P = 0.126). Functional outcomes (mRs = 0) were more favorable in the tirofiban group than in the oral antiplatelet agents group (66.7% vs. 44.4%; adjusted odds ratio 3.32; 95% CI: 1.38-7.99; P = 0. 008).

CONCLUSION

Intravenous tirofiban seems to be safe and effective with more favorable functional outcomes than oral antiplatelet agents, suggesting that tirofiban is a viable treatment choice for selected patients with non-disabling minor acute ischemic stroke.

Within-lesion heterogeneity of subcortical DWI lesion evolution, and stroke outcome: A voxel-based analysis

The fate of subcortical diffusion-weighted imaging (DWI) lesions in stroke patients is highly variable, ranging from complete tissue loss to no visible lesion on follow-up. Little is known about within-lesion heterogeneity and its relevance for stroke outcome. Patients with subcortical stroke and recruited through the prospective DEDEMAS study (NCT01334749) were examined at baseline (n = 45), six months (n = 45), and three years (n = 28) post-stroke. We performed high-resolution structural MRI including DWI. Tissue fate was determined voxel-wise using fully automated tissue segmentation. Within-lesion heterogeneity at baseline was assessed by free water diffusion imaging measures. The majority of DWI lesions (66%) showed cavitation on six months follow-up but the proportion of tissue turning into a cavity was small (9 ± 13.5% of the DWI lesion). On average, 69 ± 25% of the initial lesion resolved without any visually apparent signal abnormality. The extent of cavitation at six months post-stroke was independently associated with clinical outcome, i.e. modified Rankin scale score at six months (OR = 4.71, p = 0.005). DWI lesion size and the free water-corrected tissue mean diffusivity at baseline independently predicted cavitation. In conclusion, the proportion of cavitating tissue is typically small, but relevant for clinical outcome. Within-lesion heterogeneity at baseline on advanced diffusion imaging is predictive of tissue fate.

Self- or caregiver-delivered manual remote ischemic conditioning therapy in acute ischemic stroke is feasible: the Early Remote Ischemic Conditioning in Stroke (ERICS) trial

Background: Infarct growth and recurrent stroke may be responsible for early morbidity and mortality in patients with acute ischemic stroke. Remote ischemic conditioning (RIC) may reduce infarct growth and prevent recurrent stroke; however, the exact dose remains to be investigated. We hypothesized that self- or caregiver-delivered six cycles of RIC intervention in acute ischaemic stroke for the first 12 weeks is feasible and safe compared to the four cycles RIC intervention. Methods: Adult ischemic stroke patients presenting within the first 48 h of symptom onset were screened. Patients with magnetic resonance imaging (MRI) evidence of acute infarct were randomized (1:1) to receive either four or six cycles of RIC therapy sessions two times daily in both arms for 12 weeks. All patients underwent MRI for infarct volume assessment and endothelial-dependent flow-mediated dilation (EDFMD) testing at baseline, 7 days and 12 weeks.   Results: A total of 57 patients with mean±SD age of 59.4±12.4 years and median National Institute of Stroke Scale, 4 (IQR, 3-7) were randomised at a median of 23 h 30 min (IQR, 10 h 20 min to 30 h) after symptom onset to either the four-cycle (n=27) or six-cycle group (n=30). A total of 18 (66%) patients completed ≥50% sessions in 12 weeks in the four-cycles group; 21 (69.7%) patients completed ≥50% sessions in 12 weeks in the six-cycle group (p=0.4). There was no between-group differences in infarct growth, early neurological deterioration, recurrent stroke, and EDFMD at 7 days and 90 days. Conclusion: Both four and six cycles of short-term self- or caregiver-delivered RIC therapy is safe and may be feasible in acute ischaemic stroke patients. Randomised clinical trials are needed to assess efficacy to decrease infarct growth and prevent early neurological deterioration. Registration: Clinical Trial Registry - India: CTRI/2016/11/007495; registered on 25/11/2016.

Harmful neutrophil subsets in patients with ischemic stroke: Association with disease severity

Objective

To better understand the functional state of circulating neutrophils in patients with ischemic stroke (IS) for planning future clinical trials.

Methods

We analyzed by flow cytometry activation state of circulating neutrophils and the distribution of neutrophil peripheral subsets in 41 patients with acute IS less than 6 hours before admission and compared them with 22 age-matched healthy controls.

Results

Our results demonstrated continuous basal hyperactivation of circulating neutrophils during acute IS, characterized by lower l-selectin expression and higher CD11b expression at the cell surface, increased ROS production by neutrophils, and greater circulating levels of neutrophil elastase. Neutrophil hyperactivation was associated with deregulation of the equilibrium between apoptotic and necrotic. Patients also had higher percentages than controls of the overactive senescent (CXCR4^bright/CD62L^dim) neutrophil subset and increased percentage of neutrophils with a reverse transendothelial migration (CD54^highCXCR1^low) phenotype. Importantly, neutrophil alterations were associated with the clinical severity of the stroke, evaluated by its NIH Stroke Scale score.

Conclusion

Altogether, our results indicate that during acute IS, the inflammatory properties of circulating neutrophils rise, associated with the expansion of harmful neutrophil subsets. These changes in neutrophil homeostasis, associated with disease severity, may play an instrumental role by contributing to systemic inflammation and to the blood-brain barrier breakdown. Our findings highlight new potential therapeutic approaches of stroke by rebalancing the ratio of senescent to immunosuppressive neutrophils or decreasing reverse neutrophil transmigration or both.

An open-label, one-arm, dose-escalation study to evaluate safety and tolerability of extremely low frequency magnetic fields in acute ischemic stroke

Extremely low frequency magnetic fields (ELF-MF) could be an alternative neuroprotective approach for ischemic stroke because preclinical studies have demonstrated their effects on the mechanisms underlying ischemic damage. The purpose of this open-label, one arm, dose-escalation, exploratory study is to evaluate the safety and tolerability of ELF-MF in patients with acute ischemic stroke. Within 48 hours from the stroke onset, patients started ELF-MF treatment, daily for 5 consecutive days. Clinical follow-up lasted 12 months. Brain MRI was performed before and 1 month after the treatment. The distribution of ELF-MF in the ischemic lesion was estimated by dosimetry. Six patients were stimulated, three for 45 min/day and three for 120 min/day. None of them reported adverse events. Clinical conditions improved in all the patients. Lesion size was reduced in one patient stimulated for 45 minutes and in all the patients stimulated for 120 minutes. Magnetic field intensity within the ischemic lesion was above 1 mT, the minimum value able to trigger a biological effect in preclinical studies. Our pilot study demonstrates that ELF-MF are safe and tolerable in acute stroke patients. A prospective, randomized, placebo-controlled, double-blind study will clarify whether ELF-MFs could represent a potential therapeutic approach.

Diffusion-weighted magnetic resonance imaging reflects activation of signal transducer and activator of transcription 3 during focal cerebral ischemia/reperfusion

Signal transducer and activator of transcription (STAT) is a unique protein family that binds to DNA, coupled with tyrosine phosphorylation signaling pathways, acting as a transcriptional regulator to mediate a variety of biological effects. Cerebral ischemia and reperfusion can activate STATs signaling pathway, but no studies have confirmed whether STAT activation can be verified by diffusion-weighted magnetic resonance imaging (DWI) in rats after cerebral ischemia/reperfusion. Here, we established a rat model of focal cerebral ischemia injury using the modified Longa method. DWI revealed hyperintensity in parts of the left hemisphere before reperfusion and a low apparent diffusion coefficient. STAT3 protein expression showed no significant change after reperfusion, but phosphorylated STAT3 expression began to increase after 30 minutes of reperfusion and peaked at 24 hours. Pearson correlation analysis showed that STAT3 activation was correlated positively with the relative apparent diffusion coefficient and negatively with the DWI abnormal signal area. These results indicate that DWI is a reliable representation of the infarct area and reflects STAT phosphorylation in rat brain following focal cerebral ischemia/reperfusion.